ABSTRACT
Abstract
In some variations, an apparatus provides real-time monitoring of voltage and differential voltage of both anode and cathode in a battery configured with at least one reference electrode. Voltage monitors are connected to a computer programmed for receiving anode voltage signals; receiving cathode voltage signals; calculating the derivative of the anode voltage with respect to time or with respect to capacity; and calculating the derivative of the cathode voltage with respect to time or with respect to capacity. Other variations provide an apparatus for real-time assessment of capacities of both anode and cathode in a battery, comprising a computer programmed for receiving electrode voltage signals; estimating first and second electrode open-circuit voltages at two different times, and correlating the first and second electrode open-circuit voltages to first and second electrode states of charge, respectively, for each of anode and cathode. The anode and cathode capacities may then be estimated independently.
Description
PRIORITY DATA
This patent application is a non-provisional application with priority to U.S. Provisional Patent App. No. 61/908,095, filed Nov. 23, 2013, which is hereby incorporated by reference herein.
FIELD OF THE INVENTION
The present invention generally relates to systems and methods to monitor the health and capacity of metal-ion batteries configured with a reference electrode.
BACKGROUND OF THE INVENTION
An electrochemical system is a system that either derives electrical energy from chemical reactions, or facilitates chemical reactions through the introduction of electrical energy. An electrochemical system generally includes a cathode, an anode, and an electrolyte, and is typically complex with multiple scales from nanometers to meters. Examples of these systems include batteries and fuel cells. On-line characterization of batteries or fuel cells in vehicles is difficult, due to very rough noisy environments.
On-line characterization of such electrochemical systems is desirable in many applications, which include real-time evaluation of in-flight batteries on a satellite or aviation vehicle, and dynamic diagnostics of traction batteries for electric and hybrid-electric vehicles. In many battery-powered systems, the efficiency of batteries can be greatly enhanced by intelligent management of the electrochemical energy storage system. Management is only possible with proper diagnosis of the battery states.
In many battery-powered systems such as electric vehicles and satellites, real-time characterization of battery thermodynamic potential and kinetics is desirable. The characterization is crucial for battery states estimation including the state of charge (SOC), the charge and the discharge power capabilities (state of power, SOP), and the battery state of health (SOH).
Current systems typically rely exclusively on voltage monitoring of the full battery cell, which is useful for identifying a problem but is often incapable of preventing damage because the system is triggered during/after the system has exceeded its threshold values. In these systems, the only way to completely avoid damage is to establish conservative threshold values (tighten the operating limits), which limits the performance of the battery.
A three-electrode battery structure (i.e., a battery structure that includes a reference electrode) has one more reference electrode than a conventional battery configuration, which has only two electrodes (cathode and anode). Due to this additional electrode, more current and voltage information is measurable than in conventional batteries. Therefore, a three-electrode configuration is very useful for diagnostics.
Typical in-lab experiments on three-electrode batteries are conducted around equilibrium states; therefore, the measured anode (or cathode) potential against the reference electrode is the open-circuit potential (OCV), also called thermodynamic potential, of the anode (or cathode). However, so far there hasn't been a reliable instrumentation and method to characterize each individual electrode of the battery when the battery is cycling away from equilibrium states, under a random driving profile. In many applications, such as electric vehicles, batteries are usually driven in high rates and therefore are not around equilibrium.
Methods, systems, and apparatus are sought which are capable of characterizing each individual electrode of a three-electrode battery, including open-circuit potentials, when the battery is cycling in a non-equilibrium state and under a random driving profile. What is desired is a simple, direct method of monitoring the voltage and differential voltage of each electrode independently in a battery. In a typical battery, the management system relies only on the voltage from the full cell. However, the full cell voltage is a poor indicator of the health of each electrode.
SUMMARY OF THE INVENTION
In some variations, the invention provides an apparatus for real-time monitoring of voltage and differential voltage of both anode and cathode in a metal-ion battery, the apparatus comprising:
a first voltage monitor that is connectable between the anode and a reference electrode of the battery; a second voltage monitor that is connectable between the cathode and the reference electrode or another reference electrode; and a computer programmed using non-transitory memory with executable code for executing the steps of:
receiving anode voltage signals derived from the first voltage monitor;
receiving cathode voltage signals derived from the second voltage monitor;
receiving or calculating a derivative of anode voltage with respect to time and/or a derivative of anode voltage with respect to capacity; and
receiving or calculating a derivative of cathode voltage with respect to time and/or a derivative of cathode voltage with respect to capacity.
In some embodiments, the computer is programmed to execute the step of estimating one or more battery states selected from the group consisting of state of charge, state of power, state of health, state of safety, and combinations thereof. In certain embodiments in which the state of charge is estimated, the computer is further programmed to execute the step of estimating anode capacity or anode remaining capacity. In these or other embodiments, the computer is further programmed to execute the step of estimating cathode capacity or cathode remaining capacity.
Some embodiments provide a system in which the apparatus, described above, is linked in operable communication with the battery (such as, but not limited to, a lithium-ion battery).
Some variations of the invention provide an apparatus for real-time assessment of capacity of both anode and cathode in a metal-ion battery, the apparatus comprising:
a first voltage monitor that is connectable between the anode and a reference electrode of the battery; a second voltage monitor that is connectable between the cathode and the reference electrode or another reference electrode; and a computer programmed using non-transitory memory with executable code for executing the steps of:
receiving anode voltage signals derived from the first voltage monitor at a plurality of times;
receiving cathode voltage signals derived from the second voltage monitor at the plurality of times;
receiving current signals derived from battery current at the plurality of times;
estimating, at a first time and a second time, first and second anode open-circuit voltages and correlating the first and second anode open-circuit voltages to first and second anode states of charge, respectively;
calculating anode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first anode states of charge;
estimating, at the first time and a second time, first and second cathode open-circuit voltages and correlating the first and second cathode open-circuit voltages to first and second cathode states of charge, respectively; and
calculating cathode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first cathode states of charge.
In some embodiments, the first and second times are selected such that the battery current is about 0. The first and second anode open-circuit voltages may each be estimated from anode voltage at the first and second times, when the battery current is about 0. Also, the first and second cathode open-circuit voltages may each be estimated from cathode voltage at these first and second times.
In some embodiments, the first and second anode open-circuit voltages are correlated to the first and second anode states of charge using a look-up table, graph, equation, or combination thereof. In these or other embodiments, the first and second cathode open-circuit voltages are correlated to the first and second cathode states of charge using a look-up table, graph, equation, or combination thereof.
Some embodiments provide a system in which the apparatus for real-time assessment of capacity of both anode and cathode in a metal-ion battery, is linked in operable communication with the battery (such as, but not limited to, a lithium-ion battery).
Variations of the invention also provide a method of real-time monitoring of voltage and differential voltage of both anode and cathode in a metal-ion battery, the method comprising:
providing a first voltage monitor connected between the anode and a reference electrode of the battery;
providing a second voltage monitor connected between the cathode and the reference electrode or another reference electrode;
providing a computer in operable communication with the battery;
receiving, in the computer, anode voltage signals derived from the first voltage monitor;
receiving, in the computer, cathode voltage signals derived from the second voltage monitor;
receiving or calculating, in the computer, a derivative of anode voltage with respect to time and/or a derivative of anode voltage with respect to capacity; and
receiving or calculating, in the computer, a derivative of cathode voltage with respect to time and/or a derivative of cathode voltage with respect to capacity.
In some embodiments, the method further comprises estimating, in the computer, one or more battery states selected from the group consisting of state of charge, state of power, state of health, state of safety, and combinations thereof
When the state of charge is estimated, the method may further comprise estimating, in the computer, anode capacity or anode remaining capacity. Also, when the state of charge is estimated, the method may further comprise estimating, in the computer, cathode capacity or cathode remaining capacity.
In some embodiments, the anode voltage signals and/or the cathode voltage signals are compared, in the computer, to predetermined voltage safety limits of the anode and/or the cathode, respectively. In these or other embodiments, the anode and/or cathode voltage derivative with respect to time or with respect to capacity are/is compared, in the computer, to predetermined differential voltage safety limits of the anode and/or the cathode, respectively.
Some variations provide a method of real-time assessment of capacity of both anode and cathode in a metal-ion battery, the method comprising:
providing a first voltage monitor connected between the anode and a reference electrode of the battery;
providing a second voltage monitor connected between the cathode and the reference electrode or another reference electrode;
providing a computer in operable communication with the battery;
operating the battery with a driving profile;
receiving, in the computer, anode voltage signals derived from the first voltage monitor at a plurality of times;
receiving, in the computer, cathode voltage signals derived from the second voltage monitor at the plurality of times;
receiving, in the computer, current signals derived from battery current at the plurality of times;
estimating, in the computer, at a first time and a second time, first and second anode open-circuit voltages and correlating, in the computer, the first and second anode open-circuit voltages to first and second anode states of charge, respectively;
calculating, in the computer, anode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first anode states of charge;
estimating, in the computer, at the first time and the second time, first and second cathode open-circuit voltages and correlating, in the computer, the first and second cathode open-circuit voltages to first and second cathode states of charge, respectively; and
calculating, in the computer, cathode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first cathode states of charge.
In some embodiments, the first and second times are selected such that the battery current is about 0; the first and second anode open-circuit voltages are each estimated, in the computer, from first and second measured anode voltages at the first and second times, respectively. In certain embodiments, the battery current is about 0 for at least 5 minutes prior to recording each of the first and second measured anode voltage as each of the first and second anode open-circuit voltages, respectively.
Similarly, in some embodiments wherein the first and second times are selected such that the battery current is about 0, the first and second cathode open-circuit voltages are each estimated, in the computer, from first and second measured cathode voltages at the first and second times, respectively. In certain embodiments, the battery current is about 0 for at least 5 minutes prior to recording each of the first and second measured cathode voltage as each of the first and second cathode open-circuit voltages, respectively.
The anode capacity may be determined as constant-discharge current multiplied by the time period for discharging anode voltage from its minimum to maximum. The cathode capacity may be determined as constant-discharge current multiplied by the time period for discharging cathode voltage from its minimum to maximum.
In various embodiments, the first and second anode open-circuit voltages are correlated, in the computer, to the first and second anode states of charge using a look-up table, graph, equation, or combination thereof. In these or other embodiments, the first and second cathode open-circuit voltages are correlated, in the computer (or another computer), to the first and second cathode states of charge using a look-up table, graph, equation, or combination thereof.
Some embodiments also sense and respond to variations in temperature. In some embodiments, the method further comprises receiving, in the computer, battery temperature signals at the plurality of times. The first and second anode open-circuit voltages are optionally correlated, in the computer, to the first and second anode states of charge using a look-up table, graph, equation, or combination thereof which accounts for variation of anode state of charge with temperature.
Similarly, in some embodiments, the method further comprises receiving, in the computer, battery temperature signals at the plurality of times. The first and
PRIORITY DATA
This patent application is a non-provisional application with priority to U.S. Provisional Patent App. No. 61/908,095, filed Nov. 23, 2013, which is hereby incorporated by reference herein.
FIELD OF THE INVENTION
The present invention generally relates to systems and methods to monitor the health and capacity of metal-ion batteries configured with a reference electrode.
BACKGROUND OF THE INVENTION
An electrochemical system is a system that either derives electrical energy from chemical reactions, or facilitates chemical reactions through the introduction of electrical energy. An electrochemical system generally includes a cathode, an anode, and an electrolyte, and is typically complex with multiple scales from nanometers to meters. Examples of these systems include batteries and fuel cells. On-line characterization of batteries or fuel cells in vehicles is difficult, due to very rough noisy environments.
On-line characterization of such electrochemical systems is desirable in many applications, which include real-time evaluation of in-flight batteries on a satellite or aviation vehicle, and dynamic diagnostics of traction batteries for electric and hybrid-electric vehicles. In many battery-powered systems, the efficiency of batteries can be greatly enhanced by intelligent management of the electrochemical energy storage system. Management is only possible with proper diagnosis of the battery states.
In many battery-powered systems such as electric vehicles and satellites, real-time characterization of battery thermodynamic potential and kinetics is desirable. The characterization is crucial for battery states estimation including the state of charge (SOC), the charge and the discharge power capabilities (state of power, SOP), and the battery state of health (SOH).
Current systems typically rely exclusively on voltage monitoring of the full battery cell, which is useful for identifying a problem but is often incapable of preventing damage because the system is triggered during/after the system has exceeded its threshold values. In these systems, the only way to completely avoid damage is to establish conservative threshold values (tighten the operating limits), which limits the performance of the battery.
A three-electrode battery structure (i.e., a battery structure that includes a reference electrode) has one more reference electrode than a conventional battery configuration, which has only two electrodes (cathode and anode). Due to this additional electrode, more current and voltage information is measurable than in conventional batteries. Therefore, a three-electrode configuration is very useful for diagnostics.
Typical in-lab experiments on three-electrode batteries are conducted around equilibrium states; therefore, the measured anode (or cathode) potential against the reference electrode is the open-circuit potential (OCV), also called thermodynamic potential, of the anode (or cathode). However, so far there hasn't been a reliable instrumentation and method to characterize each individual electrode of the battery when the battery is cycling away from equilibrium states, under a random driving profile. In many applications, such as electric vehicles, batteries are usually driven in high rates and therefore are not around equilibrium.
Methods, systems, and apparatus are sought which are capable of characterizing each individual electrode of a three-electrode battery, including open-circuit potentials, when the battery is cycling in a non-equilibrium state and under a random driving profile. What is desired is a simple, direct method of monitoring the voltage and differential voltage of each electrode independently in a battery. In a typical battery, the management system relies only on the voltage from the full cell. However, the full cell voltage is a poor indicator of the health of each electrode.
SUMMARY OF THE INVENTION
In some variations, the invention provides an apparatus for real-time monitoring of voltage and differential voltage of both anode and cathode in a metal-ion battery, the apparatus comprising:
a first voltage monitor that is connectable between the anode and a reference electrode of the battery; a second voltage monitor that is connectable between the cathode and the reference electrode or another reference electrode; and a computer programmed using non-transitory memory with executable code for executing the steps of:
receiving anode voltage signals derived from the first voltage monitor;
receiving cathode voltage signals derived from the second voltage monitor;
receiving or calculating a derivative of anode voltage with respect to time and/or a derivative of anode voltage with respect to capacity; and
receiving or calculating a derivative of cathode voltage with respect to time and/or a derivative of cathode voltage with respect to capacity.
In some embodiments, the computer is programmed to execute the step of estimating one or more battery states selected from the group consisting of state of charge, state of power, state of health, state of safety, and combinations thereof. In certain embodiments in which the state of charge is estimated, the computer is further programmed to execute the step of estimating anode capacity or anode remaining capacity. In these or other embodiments, the computer is further programmed to execute the step of estimating cathode capacity or cathode remaining capacity.
Some embodiments provide a system in which the apparatus, described above, is linked in operable communication with the battery (such as, but not limited to, a lithium-ion battery).
Some variations of the invention provide an apparatus for real-time assessment of capacity of both anode and cathode in a metal-ion battery, the apparatus comprising:
a first voltage monitor that is connectable between the anode and a reference electrode of the battery; a second voltage monitor that is connectable between the cathode and the reference electrode or another reference electrode; and a computer programmed using non-transitory memory with executable code for executing the steps of:
receiving anode voltage signals derived from the first voltage monitor at a plurality of times;
receiving cathode voltage signals derived from the second voltage monitor at the plurality of times;
receiving current signals derived from battery current at the plurality of times;
estimating, at a first time and a second time, first and second anode open-circuit voltages and correlating the first and second anode open-circuit voltages to first and second anode states of charge, respectively;
calculating anode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first anode states of charge;
estimating, at the first time and a second time, first and second cathode open-circuit voltages and correlating the first and second cathode open-circuit voltages to first and second cathode states of charge, respectively; and
calculating cathode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first cathode states of charge.
In some embodiments, the first and second times are selected such that the battery current is about 0. The first and second anode open-circuit voltages may each be estimated from anode voltage at the first and second times, when the battery current is about 0. Also, the first and second cathode open-circuit voltages may each be estimated from cathode voltage at these first and second times.
In some embodiments, the first and second anode open-circuit voltages are correlated to the first and second anode states of charge using a look-up table, graph, equation, or combination thereof. In these or other embodiments, the first and second cathode open-circuit voltages are correlated to the first and second cathode states of charge using a look-up table, graph, equation, or combination thereof.
Some embodiments provide a system in which the apparatus for real-time assessment of capacity of both anode and cathode in a metal-ion battery, is linked in operable communication with the battery (such as, but not limited to, a lithium-ion battery).
Variations of the invention also provide a method of real-time monitoring of voltage and differential voltage of both anode and cathode in a metal-ion battery, the method comprising:
providing a first voltage monitor connected between the anode and a reference electrode of the battery;
providing a second voltage monitor connected between the cathode and the reference electrode or another reference electrode;
providing a computer in operable communication with the battery;
receiving, in the computer, anode voltage signals derived from the first voltage monitor;
receiving, in the computer, cathode voltage signals derived from the second voltage monitor;
receiving or calculating, in the computer, a derivative of anode voltage with respect to time and/or a derivative of anode voltage with respect to capacity; and
receiving or calculating, in the computer, a derivative of cathode voltage with respect to time and/or a derivative of cathode voltage with respect to capacity.
In some embodiments, the method further comprises estimating, in the computer, one or more battery states selected from the group consisting of state of charge, state of power, state of health, state of safety, and combinations thereof
When the state of charge is estimated, the method may further comprise estimating, in the computer, anode capacity or anode remaining capacity. Also, when the state of charge is estimated, the method may further comprise estimating, in the computer, cathode capacity or cathode remaining capacity.
In some embodiments, the anode voltage signals and/or the cathode voltage signals are compared, in the computer, to predetermined voltage safety limits of the anode and/or the cathode, respectively. In these or other embodiments, the anode and/or cathode voltage derivative with respect to time or with respect to capacity are/is compared, in the computer, to predetermined differential voltage safety limits of the anode and/or the cathode, respectively.
Some variations provide a method of real-time assessment of capacity of both anode and cathode in a metal-ion battery, the method comprising:
providing a first voltage monitor connected between the anode and a reference electrode of the battery;
providing a second voltage monitor connected between the cathode and the reference electrode or another reference electrode;
providing a computer in operable communication with the battery;
operating the battery with a driving profile;
receiving, in the computer, anode voltage signals derived from the first voltage monitor at a plurality of times;
receiving, in the computer, cathode voltage signals derived from the second voltage monitor at the plurality of times;
receiving, in the computer, current signals derived from battery current at the plurality of times;
estimating, in the computer, at a first time and a second time, first and second anode open-circuit voltages and correlating, in the computer, the first and second anode open-circuit voltages to first and second anode states of charge, respectively;
calculating, in the computer, anode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first anode states of charge;
estimating, in the computer, at the first time and the second time, first and second cathode open-circuit voltages and correlating, in the computer, the first and second cathode open-circuit voltages to first and second cathode states of charge, respectively; and
calculating, in the computer, cathode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first cathode states of charge.
In some embodiments, the first and second times are selected such that the battery current is about 0; the first and second anode open-circuit voltages are each estimated, in the computer, from first and second measured anode voltages at the first and second times, respectively. In certain embodiments, the battery current is about 0 for at least 5 minutes prior to recording each of the first and second measured anode voltage as each of the first and second anode open-circuit voltages, respectively.
Similarly, in some embodiments wherein the first and second times are selected such that the battery current is about 0, the first and second cathode open-circuit voltages are each estimated, in the computer, from first and second measured cathode voltages at the first and second times, respectively. In certain embodiments, the battery current is about 0 for at least 5 minutes prior to recording each of the first and second measured cathode voltage as each of the first and second cathode open-circuit voltages, respectively.
The anode capacity may be determined as constant-discharge current multiplied by the time period for discharging anode voltage from its minimum to maximum. The cathode capacity may be determined as constant-discharge current multiplied by the time period for discharging cathode voltage from its minimum to maximum.
In various embodiments, the first and second anode open-circuit voltages are correlated, in the computer, to the first and second anode states of charge using a look-up table, graph, equation, or combination thereof. In these or other embodiments, the first and second cathode open-circuit voltages are correlated, in the computer (or another computer), to the first and second cathode states of charge using a look-up table, graph, equation, or combination thereof.
Some embodiments also sense and respond to variations in temperature. In some embodiments, the method further comprises receiving, in the computer, battery temperature signals at the plurality of times. The first and second anode open-circuit voltages are optionally correlated, in the computer, to the first and second anode states of charge using a look-up table, graph, equation, or combination thereof which accounts for variation of anode state of charge with temperature.
Similarly, in some embodiments, the method further comprises receiving, in the computer, battery temperature signals at the plurality of times. The first and second cathode open-circuit voltages are optionally correlated to the first and second cathode states of charge using a look-up table, graph, equation, or combination thereof which accounts for variation of anode state of charge with temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A shows a schematic of a metal-ion battery with a reference electrode that can provide accurate monitoring of cathode and anode under battery operation, in some embodiments.
FIG. 1B depicts circuit connections that may be supplied to the metal-ion battery of FIG. 1B , in some embodiments.
FIG. 2 shows a simplified schematic of an exemplary computer system that may be utilized in variations of the invention.
FIG. 3 plots charge-discharge profiles of a lithium-ion battery cell with reference electrode in Example 1.
FIG. 4A depicts experimental voltage and differential voltage from a graphite-based negative electrode, in Example 2.
FIG. 4B depicts experimental voltage and differential voltage from a graphite-based negative electrode, in Example 2.
FIG. 5A shows current (top), cathode voltage (middle), and anode voltage data for Example 3.
FIG. 5B illustrates how a cathode OCV-SOC look-up table may be established, in Example 3.
FIG. 5C illustrates how an anode OCV-SOC look-up table may be established, in Example 3.
FIG. 6A plots current and voltage data during a rest period followed by a 5 min charge at 2 C rate, in Example 3.
FIG. 6B plots anode and cathode voltage versus time (in seconds) and open-circuit voltages are determined at two different points (during a period of about zero current) for both the anode and the cathode, in Example 3.
FIG. 7 shows experiments data obtained from a three-electrode pouch cell driven with a random profile, displaying current (top graph), cathode voltage (middle graph), and anode voltage (bottom graph) according to Example 4.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The methods, apparatus, and systems of the present invention will be described in detail by reference to various non-limiting embodiments and figures.
This description will enable one skilled in the art to make and use the invention, and it describes several embodiments, adaptations, variations, alternatives, and uses of the invention. These and other embodiments, features, and advantages of the present invention will become more apparent to those skilled in the art when taken with reference to the following detailed description of the invention in conjunction with the accompanying drawings.
As used in this specification and the appended claims, the singular forms âa,â âan,â and âtheâ include plural referents unless the context clearly indicates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this invention belongs. As intended herein, âreceivingâ shall be broadly construed as including âproviding,â âsensingâ (e.g., using a sensor attached to a computer), âcalculatingâ (e.g., using executable code in a computer), and so on.
Unless otherwise indicated, all numbers expressing parameters, conditions, results, and so forth used in the specification and claims are to be understood as being modified in all instances by the term âabout.â Accordingly, unless indicated to the contrary, the numbers set forth in the following specification and attached claims are approximations that may vary depending upon specific algorithms and calculations.
The term âcomprising,â which is synonymous with âincluding,â âcontaining,â or âcharacterized byâ is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. âComprisingâ is a term of art used in claim language which means that the named claim elements are essential, but other claim elements may be added and still form a construct within the scope of the claim.
As used herein, the phase âconsisting ofâ excludes any element, step, or ingredient not specified in the claim. When the phrase âconsists ofâ (or variations thereof) appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole. As used herein, the phase âconsisting essentially ofâ limits the scope of a claim to the specified elements or method steps, plus those that do not materially affect the basis and novel characteristic(s) of the claimed subject matter.
With respect to the terms âcomprising,â âconsisting of,â and âconsisting essentially of,â where one of these three terms is used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms. Thus in some embodiments not otherwise explicitly recited, any instance of âcomprisingâ may be replaced by âconsisting ofâ or, alternatively, by âconsisting essentially ofâ
Some variations of this invention provide a new method to monitor the health and capacity of the cathode (positive electrode) and, independently, the anode (negative electrode) during battery operation (charge and discharge). At least one reference electrode is part of a management system that monitors the potentials (i.e. voltage) along with the first differential voltage of both electrodes independently, to determine the battery state of capacity and state of health.
In a conventional electrochemical cell (battery), at a given state-of-charge (SOC), the measured cell voltage represents the voltage difference between the cathode and anode:
V cell =V cathode âV anode ââ(EQ. 1)
However, the voltage behavior of each individual electrode is largely unknown since the deconvolution of the full cell voltage to obtain the voltage of each electrode is especially challenging during battery operation.
In a three-electrode cell, for example, voltage monitoring may be used to mitigate damage to the electrodes when the voltage (or voltage rate of change) of the individual electrodes exceeds a threshold value. The derivatives of the potential may be used to reveal potential problems in the electrochemical behavior before the electrodes are damaged. By providing an early indication of a potential problem, the system can respond with the appropriate change in cycling conditions (e.g. reducing the rate or lowering the cycling limits) to avoid damage to the electrode. In addition, this system may also be used to determine the capacity of each electrode independently to better track the health and remaining life of the battery.
In a typical battery, the management system relies only on the voltage from the full cell (no reference electrode). However, the full cell voltage is a poor indicator of the health of each electrode itself. Some variations provide a simple, direct method of monitoring the voltage (V) and either or both of derivative of the voltage with respect to capacity (dV/dQ) or derivative of the voltage with respect to time (dV/dt) of each electrode independently, in a battery using a reference electrode (e.g., in a three-electrode cell). Improved battery management and a safer battery can result. The capacity Q is the capacity of the battery electrode, measured in coulombs.
A three-electrode cell equipped with a system to monitor the voltage and differential voltage can provide critical information to the battery management system. The system can respond by adjusting the limits and rates used in the charge/discharge reactions (optimizing electrochemical performance) and extending the battery life. Also, by monitoring the voltage and differential voltage of each of the electrodes independently, limits can be established below threshold values where damage occurs.
As a battery ages, the voltages of the positive and negative electrodes diverge due to resistance rise and material degradation. For example, during battery charging, the voltage of the negative electrode is depressed to a lower voltage close to 0 V, while the positive electrode voltage can rise higher quickly due to the increase in resistance as the battery ages. In this common scenario, the full cell voltage often appears normal while the actual voltages of each of the electrodes are outside the safety limits. Changes in the voltage profiles due to cell aging are very difficult to quantify from the terminal voltage of the full cell.
The disclosed invention in some variations enables the monitoring of the individual electrode voltage and the rate of voltage change with time (dV/dt) or with capacity (dV/dQ) for enhanced battery performance and safety. While the direct monitoring of each individual electrode voltage is useful for identifying when a battery has reached or exceeded a safety limit, monitoring the change in voltage (dV/dQ), along with the voltage (V), provides more useful inputs for a battery management system (BMS). Monitoring V and dV/dQ (or dV/dt) provides an early warning system, identifying when the voltage is approaching a limit and allowing the BMS to make a change to the battery operation so the limits are never reached. The differential voltage is especially sensitive to changes in the material. As the battery electrode degrades, the magnitudes of the peaks in the dV/dQ spectrum tend to increase. Therefore dV/dQ is a reliable indicator of the battery state-of-health.
Some embodiments are premised on the realization that the magnitude of the dV/dQ change at a specific state-of-charge (SOC) can be used to indicate and predict the capacity of the battery. The differential voltage (dV/dt or dV/dQ) can also be used (with the voltage) in a battery management system to actively control the battery operation (cycling rate, depth of discharge, and/or depth of charge) to ensure optimal battery performance and safety. For example, during charging, when the electrode voltage is near the safety limit and approaching quickly, the BMS can be programmed to reduce the charging current to safeguard the battery while maximizing the charge capacity.
In some variations, the invention provides a method of determining the capacity (online) of each electrode over the life of the battery, which is useful for accurate state-of-charge and state-of-power determination, among other things. This information can also be used in a battery management system to maintain optimal cycling (within the safety limits) and to determine the remaining life of the battery.
Embodiments of the invention can improve battery diagnosis and battery management systems. Examples include improving battery state-of-charge (SOC) monitoring, enhancing battery safety, monitoring battery aging, and extending battery life. Battery states include, but are not limited to, state-of-health, state-of-charge, state-of-power, high-frequency resistance, charge-transfer resistance, and double-layer capacitance. State-of-health is a figure of merit of the condition of a battery (or a cell, or a battery pack), compared to its ideal conditions. State-of-charge is an indication of how much useful energy remains in the battery. State-of-power characterizes the charge and discharge power capabilities of the battery.
Embodiments of the present invention will now be described in detail, including reference to the accompanying figures. The figures provide representative illustration of the invention and are not limiting in their content. It will be understood by one of ordinary skill in the art that the scope of the invention extends beyond the specific embodiments depicted. For example, the invention is by no means limited to lithium-ion batteries.
Without a reference electrode, only the full cell battery voltage information is available. During battery operation, even when the battery voltage appears to be in a normal operating window, it is difficult to control the positive and negative electrode potentials within safety limits. There are several scenarios by which not knowing the individual electrode voltages can lead to potential shortcomings and serious safety concerns:
1. During charging, the negative electrode (anode) can drop below 0 V (vs. Li), causing lithium plating and ultimately an internal short circuit.
2. During charging, the positive electrode (cathode) can over-charge beyond the safety limit, causing decomposition of the active materials and electrolytes creating an excess of heat and possible thermal runaway.
3. During discharging, the negative electrode voltage can rise above voltage safety limit, causing dissolution of metal ions from the current collector and an internal short circuit.
4. During discharging, the positive electrode voltage can drop below the voltage safety limit, causing over-discharging of positive active materials.
It is therefore preferred to include at least one reference electrode in the battery configuration. FIGS. 1A and 1B depict an exemplary three-electrode cell, in some embodiments of a metal-ion battery with a reference electrode that can provide accurate monitoring of cathode and anode potentials under battery operation. The configuration includes a negative electrode material on metal foil, a positive electrode material on metal mesh, and a metal reference electrode on metal foil. Each electrode is electronically isolated by separators. In some embodiments of FIG. 1A , for example, the battery structure 100 is in a layered configuration. A cathode 140 coated on a porous aluminum (Al) mesh (porous) current collector 150 faces an anode 120 coated on a copper (Cu) current collector 110 separated by a separator layer 130 . The porous current collector 150 enables ion communication through the cathode. A reference electrode 170 (for example, lithium on copper foil 180 ) is disposed adjacent to the cathode 140 with Al mesh current collector 150 . The reference electrode 170 is electronically isolated from the other electrodes by a separator layer 160 . The anode 120 and cathode 140 may be switched, if desired.
The battery structure 105 of FIG. 1B depicts circuit connections that may be adapted to the battery structure 100 . A current source/monitor (labeled with a circled I) and a voltage monitor (labeled with a circled V) are connected between the anode's Cu current collector 110 and the cathode's Al current collector 150 . Another voltage monitor (labeled V a with dashed lines) is connected between the anode's Cu current collector 110 and the reference electrode's Cu foil current collector 180 . Another voltage monitor (labeled V c with dotted lines) is connected between the cathode's Al current collector 150 and the reference electrode's Cu foil current collector 180 . The battery is driven with a current I cycling profile, and measurement is made in real time of the current I and voltage V between anode and cathode, as well as the anode potential V a referring to the reference electrode and/or the cathode potential V c referring to the reference electrode. It is noted that one of the voltage monitors in FIG. 1B is redundant but may be employed to verify the data. That is, only two of the voltage monitors (V, V a , V c ) are necessary.
Some variations of the invention provide circuit connections in systems and apparatus, and associated methods, that can characterize a three-electrode battery in real time. The proposed circuit connection enables measurement of both anode and cathode potential, sampling them concurrently without interference.
In this disclosure, âreal timeâ is intended to mean that characterization (including monitoring and updating) has a time scale of about 1 millisecond (10 â3 s) or less. Any event happening within about 1 millisecond is considered as happening at the same time, with respect to battery monitoring. Therefore, battery characterization within about 1 millisecond is considered real-time (or delay-free) characterization. The actual time scale of characterization may on the order of 10 â4 s, 10 â5 s, 10 â6 s, or even shorter times, in some embodiments.
It should be noted that many other battery configurations are possible. For example, the reference electrode may be disposed perpendicular to the anode and cathode layers, on the side. A wire reference electrode may be supplied. Generally, various shapes, positions, and types of reference electrodes may be used. Also, more than one reference electrode may be employed. In some embodiments, a reference electrode is supplied for the anode, and another reference electrode is supplied for the cathode. A spare electrode may also be included which may function as either a reference electrode or as a backup anode or cathode, if needed.
In some variations, the invention provides an apparatus for real-time monitoring of voltage and differential voltage of both anode and cathode in a metal-ion battery, the apparatus comprising:
a first voltage monitor that is connectable between the anode and a reference electrode of the battery; a second voltage monitor that is connectable between the cathode and the reference electrode or another reference electrode; and a computer programmed using non-transitory memory with executable code for executing the steps of:
receiving anode voltage signals derived from the first voltage monitor;
receiving cathode voltage signals derived from the second voltage monitor;
receiving or calculating a derivative of anode voltage with respect to time and/or a derivative of anode voltage with respect to capacity; and
receiving or calculating a derivative of cathode voltage with respect to time and/or a derivative of cathode voltage with respect to capacity.
In some embodiments, the computer is programmed to execute the step of estimating one or more battery states selected from the group consisting of state of charge, state of power, state of health, state of safety, and combinations thereof. In certain embodiments in which the state of charge is estimated, the computer is further programmed to execute the step of estimating anode capacity or anode remaining capacity. In these or other embodiments, the computer is further programmed to execute the step of estimating cathode capacity or cathode remaining capacity.
Some embodiments provide a system in which the apparatus, described above, is linked in operable communication with the battery (such as, but not limited to, a lithium-ion battery).
In some variations, the invention provides a method of characterizing a metal-ion battery (e.g., a lithium-ion battery) in real time, the method comprising:
(a) providing or obtaining a battery with a first electrode, a second electrode, and a reference electrode;
(b) conducting at least two of the following substeps: (b)(i) providing a first voltage monitor connected between the first electrode and the second electrode; (b)(ii) providing a second voltage monitor connected between the first electrode and the reference electrode; and/or (b)(iii) providing a third voltage monitor connected between the second electrode and the reference electrode;
(c) driving the battery, using a current source connecting the first and second electrodes, with any current cycling profile;
(d) measuring, in real time, current signals between the first and second electrodes and at least two voltage signals derived from the first, second, and/or third voltage monitors in substeps (b)(i), (b)(ii), and/or (b)(iii), respectively; and
(e) optionally measuring, in real time, at least two voltage derivatives (with respect to capacity or with respect to time) derived from the first, second, and/or third voltage monitors in substeps (b)(i), (b)(ii), and/or (b)(iii), respectively.
In some embodiments, all of substeps (b)(i), (b)(ii), and (b)(iii) are conducted. Optionally, in these embodiments, one of the voltage monitors may be repositioned for use as another one of the voltage monitors.
In other variations, the invention provides a battery system comprising a three-electrode metal-ion battery configured with at least two voltage monitors selected from a first voltage monitor connected between a first electrode and a second electrode, a second voltage monitor connected between the first electrode and a reference electrode, and/or a third voltage monitor connected between the second electrode and the reference electrode; a current source connecting the first and second electrodes; and a computer disposed in communication with the battery, the computer programmed using non-transitory memory with executable code for executing the steps of:
(a) controlling the current source to drive the battery with a current cycling profile;
(b) measuring current signals between the first and second electrodes, and at least two voltage signals derived from the first, second, and/or third voltage monitors; and
(c) measuring at least two voltage derivatives (with respect to capacity or with respect to time) derived from the first, second, and/or third voltage monitors.
Some variations of the invention provide an apparatus for real-time assessment of capacity of both anode and cathode in a metal-ion battery, the apparatus comprising:
a first voltage monitor that is connectable between the anode and a reference electrode of the battery; a second voltage monitor that is connectable between the cathode and the reference electrode or another reference electrode; and a computer programmed using non-transitory memory with executable code for executing the steps of:
receiving anode voltage signals derived from the first voltage monitor at a plurality of times;
receiving cathode voltage signals derived from the second voltage monitor at the plurality of times;
receiving current signals derived from battery current at the plurality of times;
estimating, at a first time and a second time, first and second anode open-circuit voltages and correlating the first and second anode open-circuit voltages to first and second anode states of charge, respectively;
calculating anode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first anode states of charge;
estimating, at the first time and a second time, first and second cathode open-circuit voltages and correlating the first and second cathode open-circuit voltages to first and second cathode states of charge, respectively; and
calculating cathode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first cathode states of charge.
In some embodiments, the first and second times are selected such that the battery current is about 0 (such as less than 0.01 A, 0.005 A, 0.004 A, 0.003 A, 0.002 A, or 0.001 A). The first and second anode open-circuit voltages may each be estimated from anode voltage at the first and second times, when the battery current is about 0 (such as less than 0.01 A, 0.005 A, 0.004 A, 0.003 A, 0.002 A, or 0.001 A). Also, the first and second cathode open-circuit voltages may each be estimated from cathode voltage at these first and second times.
In some embodiments, the first and second anode open-circuit voltages are correlated to the first and second anode states of charge using a look-up table, graph, equation, or combination thereof. In these or other embodiments, the first and second cathode open-circuit voltages are correlated to the first and second cathode states of charge using a look-up table, graph, equation, or combination thereof.
Some embodiments provide a system in which the apparatus for real-time assessment of capacity of both anode and cathode in a metal-ion battery, is linked in operable communication with the battery (such as, but not limited to, a lithium-ion battery).
Variations of the invention also provide a method of real-time monitoring of voltage and differential voltage of both anode and cathode in a metal-ion battery, the method comprising:
providing a first voltage monitor connected between the anode and a reference electrode of the battery;
providing a second voltage monitor connected between the cathode and the reference electrode or another reference electrode;
providing a computer in operable communication with the battery;
receiving, in the computer, anode voltage signals derived from the first voltage monitor;
receiving, in the computer, cathode voltage signals derived from the second voltage monitor;
receiving or calculating, in the computer, a derivative of anode voltage with respect to time and/or derivative of anode voltage with respect to capacity; and
receiving or calculating, in the computer, a derivative of cathode voltage with respect to time and/or a derivative of cathode voltage with respect to capacity.
In some embodiments, the method further comprises estimating, in the computer, one or more battery states selected from the group consisting of state of charge, state of power, state of health, state of safety, and combinations thereof.
When the state of charge is estimated, the method may further comprise estimating, in the computer, anode capacity or anode remaining capacity. Also, when the state of charge is estimated, the method may further comprise estimating, in the computer, cathode capacity or cathode remaining capacity.
In some embodiments, the anode voltage signals and/or the cathode voltage signals are compared, in the computer, to predetermined voltage safety limits of the anode and/or the cathode, respectively. In these or other embodiments, the anode and/or cathode voltage derivative with respect to time or with capacity are/is compared, in the computer, to predetermined differential voltage safety limits of the anode and/or the cathode, respectively.
Some variations provide a method of real-time assessment of capacity of both anode and cathode in a metal-ion battery, the method comprising:
providing a first voltage monitor connected between the anode and a reference electrode of the battery;
providing a second voltage monitor connected between the cathode and the reference electrode or another reference electrode;
providing a computer in operable communication with the battery;
operating the battery with a driving profile;
receiving, in the computer, anode voltage signals derived from the first voltage monitor at a plurality of times;
receiving, in the computer, cathode voltage signals derived from the second voltage monitor at the plurality of times;
receiving, in the computer, current signals derived from battery current at the plurality of times;
estimating, in the computer, at a first time and a second time, first and second anode open-circuit voltages and correlating, in the computer, the first and second anode open-circuit voltages to first and second anode states of charge, respectively;
calculating, in the computer, anode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first anode states of charge;
estimating, in the computer, at the first time and the second time, first and second cathode open-circuit voltages and correlating, in the computer, the first and second cathode open-circuit voltages to first and second cathode states of charge, respectively; and
calculating, in the computer, cathode capacity as the integral of the current signals from the first time to the second time, divided by the difference between the second and first cathode states of charge.
In some embodiments, the first and second times are selected such that the battery current is about 0 (such as less than 0.01 A, 0.005 A, 0.004 A, 0.003 A, 0.002 A, or 0.001 A); the first and second anode open-circuit voltages are each estimated, in the computer, from first and second measured anode voltages at the first and second times, respectively. In certain embodiments, the battery current is about 0 for at least 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 minutes prior to recording each of the first and second measured anode voltage as each of the first and second anode open-circuit voltages, respectively.
Similarly, in some embodiments wherein the first and second times are selected such that the battery current is about 0 (such as less than 0.01 A, 0.005 A, 0.004 A, 0.003 A, 0.002 A, or 0.001 A), the first and second cathode open-circuit voltages are each estimated, in the computer, from first and second measured cathode voltages at the first and second times, respectively. In certain embodiments, the battery current is about 0 for at least 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 minutes prior to recording each of the first and second measured cathode voltage as each of the first and second cathode open-circuit voltages, respectively.
The anode capacity may be determined as constant-discharge current multiplied by the time period for discharging anode voltage from its minimum to maximum. The cathode capacity may be determined as constant-discharge current multiplied by the time period for discharging cathode voltage from its minimum to maximum.
In various embodiments, the first and second anode open-circuit voltages are correlated, in the computer, to the first and second anode states of charge using a look-up table, graph, equation, or combination thereof. In these or other embodiments, the first and second cathode open-circuit voltages are correlated, in the computer (or another computer), to the first and second cathode states of charge using a look-up table, graph, equation, or combination thereof
In certain embodiments, additional data inputs (beyond current and voltage) are considered in the model and algorithms. Additional data inputs may relate to ambient conditions of the local environment, including temperature, relative humidity, and electromagnetic interference patterns, for instance. Additional data inputs may be based on previous experience with similar devices, or other ways to capture prior knowledge to improve the accuracy of the diagnostics for the intended purpose. These additional data inputs may be quantitative or qualitative in nature.
Some embodiments also sense and respond to variations in temperature. In some embodiments, the method further comprises receiving, in the computer, battery temperature signals at the plurality of times. The first and second anode open-circuit voltages are optionally correlated, in the computer, to the first and second anode states of charge using a look-up table, graph, equation, or combination thereof which accounts for variation of anode state of charge with temperature.
Similarly, in some embodiments, the method further comprises receiving, in the computer, battery temperature signals at the plurality of times. The first and second cathode open-circuit voltages are optionally correlated, in a com
CLAIMS
Claims ( 27 )
What is claimed is:
1. An apparatus for real-time monitoring of anode and cathode voltage, anode and cathode differential voltage, and anode and cathode state of charge in a metal-ion battery, wherein said apparatus is linked in operable communication with said battery, said apparatus comprising:
a first voltage monitor that is connectable between said anode and a reference electrode of said battery; a second voltage monitor that is connectable between said cathode and said reference electrode, wherein a porous current collector is interposed between said reference electrode, on the one hand, and both of said anode and said cathode, on the other hand, to allow communication of metal ions (i) away from a metal-ion path between said cathode said anode and (ii) toward said reference electrode; and a computer programmed using non-transitory memory with executable code for executing the steps of:
receiving anode voltage signals derived from said first voltage monitor at a plurality of times;
receiving cathode voltage signals derived from said second voltage monitor at said plurality of times;
receiving or calculating a derivative of the anode voltage with respect to time and/or a derivative of the anode voltage with respect to capacity at said plurality of times;
receiving or calculating a derivative of the cathode voltage with respect to time and/or a derivative of the cathode voltage with respect to capacity at said plurality of times;
receiving current signals derived from battery current at said plurality of times;
identifying a first time and a second time, within said plurality of times, such that said battery current is 0 A for at least 1 minute, wherein between said first time and said second time, there exists an intermediate time such that said battery current is greater than 0 A;
estimating first and second anode open-circuit voltages from said anode voltage signals at said first and second times, respectively;
correlating said first and second anode open-circuit voltages to first and second anode states of charge at said first and second times, respectively;
estimating first and second cathode open-circuit voltages from said cathode voltage signals at said first and second times, respectively; and
correlating said first and second cathode open-circuit voltages to first and second cathode states of charge at said first and second times, respectively.
2. The apparatus of claim 1 , wherein said computer is programmed to execute the step of estimating one or more battery states selected from the group consisting of state of power, state of health, state of safety, and combinations thereof.
3. The apparatus of claim 1 , wherein said computer is further programmed to execute the step of estimating anode capacity or anode remaining capacity based on said first and second anode states of charge.
4. The apparatus of claim 1 , wherein said computer is further programmed to execute the step of estimating cathode capacity or cathode remaining capacity based on said first and second cathode states of charge.
5. The apparatus of claim 1 , wherein said battery is a lithium-ion battery.
6. An apparatus for real-time assessment of capacity of both anode and cathode in a metal-ion battery, wherein said apparatus is linked in operable communication with said battery, said apparatus comprising:
a first voltage monitor that is connectable between said anode and a reference electrode of said battery; a second voltage monitor that is connectable between said cathode and said reference electrode, wherein a porous current collector is interposed between said reference electrode, on the one hand, and both of said anode and said cathode, on the other hand, to allow communication of metal ions (i) away from a metal-ion path between said cathode said anode and (ii) toward said reference electrode; and a computer programmed using non-transitory memory with executable code for executing the steps of:
receiving anode voltage signals derived from said first voltage monitor at a plurality of times;
receiving cathode voltage signals derived from said second voltage monitor at said plurality of times;
receiving current signals derived from battery current at said plurality of times;
estimating, at a first time and a second time within said plurality of times, first and second anode open-circuit voltages and correlating said first and second anode open-circuit voltages to first and second anode states of charge, respectively;
calculating anode capacity as the integral of said current signals from said first time to said second time, divided by the difference between said second and first anode states of charge;
estimating, at said first time and said second time, first and second cathode open-circuit voltages and correlating said first and second cathode open-circuit voltages to first and second cathode states of charge, respectively; and
calculating cathode capacity as the integral of said current signals from said first time to said second time, divided by the difference between said second and first cathode states of charge,
wherein said first and second times are selected such that said battery current is 0 A for at least 1 minute, wherein between said first time and said second time, there exists an intermediate time such that said battery current is greater than 0 A,
wherein said first and second anode open-circuit voltages are each estimated as anode voltage at said first and second times, respectively, and
wherein said first and second cathode open-circuit voltages are each estimated as cathode voltage at said first and second times, respectively.
7. The apparatus of claim 6 , wherein said first and second times are selected such that said battery current is about 0 for at least 2 minutes.
8. The apparatus of claim 6 , wherein said first and second times are selected such that said battery current is about 0 for at least 5 minutes.
9. The apparatus of claim 6 , wherein said first and second anode open-circuit voltages are correlated to said first and second anode states of charge using a look-up table, graph, equation, or combination thereof.
10. The apparatus of claim 6 , wherein said first and second cathode open-circuit voltages are correlated to said first and second cathode states of charge using a look-up table, graph, equation, or combination thereof.
11. The apparatus of claim 6 , wherein said battery is a lithium-ion battery.
12. A method of real-time monitoring of anode and cathode voltage, anode and cathode differential voltage, and anode and cathode state of charge in a metal-ion battery, said method comprising:
providing a first voltage monitor connected between said anode and a reference electrode of said battery;
providing a second voltage monitor connected between said cathode and said reference electrode, wherein a porous current collector is interposed between said reference electrode, on the one hand, and both of said anode and said cathode, on the other hand, to allow communication of metal ions (i) away from a metal-ion path between said cathode said anode and (ii) toward said reference electrode;
providing a computer in operable communication with said battery;
receiving, in said computer, anode voltage signals derived from said first voltage monitor at a plurality of times;
receiving, in said computer, cathode voltage signals derived from said second voltage monitor at said plurality of times;
receiving or calculating, in said computer, a derivative of the anode voltage with respect to time and/or a derivative of the anode voltage with respect to capacity at said plurality of times;
receiving or calculating, in said computer, a derivative of the cathode voltage with respect to time and/or a derivative of the cathode voltage with respect to capacity at said plurality of times;
receiving current signals derived from battery current at said plurality of times;
identifying a first time and a second time, within said plurality of times, such that said battery current is 0 A for at least 1 minute, wherein between said first time and said second time, there exists an intermediate time such that said battery current is greater than 0 A;
estimating first and second anode open-circuit voltages from said anode voltage signals at said first and second times, respectively;
correlating said first and second anode open-circuit voltages to first and second anode states of charge at said first and second times, respectively;
estimating first and second cathode open-circuit voltages from said cathode voltage signals at said first and second times, respectively; and
correlating said first and second cathode open-circuit voltages to first and second cathode states of charge at said first and second times, respectively.
13. The method of claim 12 , said method further comprising estimating, in said computer, one or more battery states selected from the group consisting of state of power, state of health, state of safety, and combinations thereof.
14. The method of claim 12 , wherein said method further comprises estimating, in said computer, anode capacity or anode remaining capacity based on said first and second anode states of charge.
15. The method of claim 12 , wherein said method further comprises estimating, in said computer, cathode capacity or cathode remaining capacity based on said first and second cathode states of charge.
16. The method of claim 12 , wherein said anode voltage signals and/or said cathode voltage signals are compared, in said computer, to predetermined voltage safety limits of said anode and/or said cathode, respectively.
17. The method of claim 12 , wherein said derivative of said anode or cathode voltage with respect to time and/or said derivative of said anode or cathode voltage with respect to capacity is compared, in said computer, to predetermined differential voltage safety limits of said anode and/or said cathode, respectively.
18. A method of real-time assessment of capacity of both anode and cathode in a metal-ion battery, said method comprising:
providing a first voltage monitor connected between said anode and a reference electrode of said battery;
providing a second voltage monitor connected between said cathode and said reference electrode, wherein a porous current collector is interposed between said reference electrode, on the one hand, and both of said anode and said cathode, on the other hand, to allow communication of metal ions (i) away from a metal-ion path between said cathode said anode and (ii) toward said reference electrode;
providing a computer in operable communication with said battery;
operating said battery with a driving profile;
receiving, in said computer, anode voltage signals derived from said first voltage monitor at a plurality of times;
receiving, in said computer, cathode voltage signals derived from said second voltage monitor at said plurality of times;
receiving, in said computer, current signals derived from battery current at said plurality of times;
estimating, in said computer, at a first time and a second time within said plurality of times, first and second anode open-circuit voltages and correlating, in said computer, said first and second anode open-circuit voltages to first and second anode states of charge, respectively;
calculating, in said computer, anode capacity as the integral of said current signals from said first time to said second time, divided by the difference between said second and first anode states of charge;
estimating, in said computer, at said first time and said second time, first and second cathode open-circuit voltages and correlating, in said computer, said first and second cathode open-circuit voltages to first and second cathode states of charge, respectively; and
calculating, in said computer, cathode capacity as the integral of said current signals from said first time to said second time, divided by the difference between said second and first cathode states of charge,
wherein said first and second times are selected such that said battery current is 0 A for at least 1 minute, wherein between said first time and said second time, there exists an intermediate time such that said battery current is greater than 0 A,
wherein said first and second anode open-circuit voltages are each estimated, in said computer, as anode voltage measured at said first and second times, respectively, and
wherein said first and second cathode open-circuit voltages are each estimated, in said computer, as cathode voltage measured at said first and second times, respectively.
19. The method of claim 18 , wherein said first and second times are selected such that said battery current is about 0 for at least 2 minutes.
20. The method of claim 19 , wherein said battery current is about 0 for at least 5 minutes prior to recording each of said first and second measured anode voltage as each of said first and second anode open-circuit voltages, respectively.
21. The method of claim 19 , wherein said battery current is about 0 for at least 5 minutes prior to recording each of said first and second measured cathode voltage as each of said first and second cathode open-circuit voltages, respectively.
22. The method of claim 18 , wherein said anode capacity is determined as constant-discharge current multiplied by the time period for discharging anode voltage from its minimum to maximum.
23. The method of claim 18 , wherein said cathode capacity is determined as constant-discharge current multiplied by the time period for discharging cathode voltage from its minimum to maximum.
24. The method of claim 18 , wherein said first and second anode open-circuit voltages are correlated, in said computer, to said first and second anode states of charge using a look-up table, graph, equation, or combination thereof.
25. The method of claim 18 , wherein said first and second cathode open-circuit voltages are correlated, in said computer, to said first and second cathode states of charge using a look-up table, graph, equation, or combination thereof.
26. The method of claim 18 , said method further comprising receiving, in said computer, battery temperature signals at said plurality of times; and wherein said first and second anode open-circuit voltages are correlated, in said computer, to said first and second anode states of charge using a look-up table, graph, equation, or combination thereof which accounts for variation of anode state of charge with temperature.
27. The method of claim 18 , said method further comprising receiving, in said computer, battery temperature signals at said plurality of times; and wherein said first and second cathode open-circuit voltages are correlated, in said computer, to said first and second cathode states of charge using a look-up table, graph, equation, or combination thereof which accounts for variation of anode state of charge with temperature.
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