阅读说明：本技术 电池的熟化过程 (Battery aging process ) 是由 J·西尔维斯特 蒂莫西·克林布尔 格兰特·斯通 格雷戈里·卡梅伦 乔·罗伯特·勒沃思 于 2018-08-14 设计创作，主要内容包括：本发明涉及一种用于至少一个电池单元(32)的熟化过程。熟化过程包括对至少一个电池单元(32)充电,并使所述至少一个电池单元经历至少一天的熟化期,其中除了测量装置(30)之外,没有电负载连接到所述至少一个电池单元。熟化过程还包括在熟化期的开始和结束之间利用测量装置(30)取得所述至少一个电池单元(32)的开路电压的至少一个测量值。熟化过程还包括根据所述至少一个测量值来确定所述至少一个电池单元的完整性。(The invention relates to a curing process for at least one battery cell (32). The maturation process comprises charging at least one battery cell (32) to which no electrical load is connected other than the measuring device (30) and subjecting the at least one battery cell to a maturation period of at least one day. The maturation process further comprises taking at least one measurement of the open circuit voltage of the at least one battery cell (32) with the measuring device (30) between the beginning and the end of the maturation period. The maturing process further comprises determining the integrity of the at least one battery cell from the at least one measurement value.)

1. A maturation process for at least one battery cell, the process comprising:

charging the at least one battery cell;

subjecting the at least one battery cell to a maturation period of at least one day, wherein no electrical load is connected to the at least one battery cell other than the measuring device;

taking at least one measurement of the open circuit voltage of the at least one battery cell between the beginning and the end of the maturation period using a measuring device; and

determining an integrity of the at least one battery cell based on the at least one measurement.

2. The maturation process of claim 1, wherein at least one measurement of the open circuit voltage is taken after a beginning of a maturation period and before an end of a maturation period.

3. A maturing process according to claim 1 or 2, wherein the at least one measured value is compared with a predetermined voltage value, wherein the step of determining the integrity of the at least one battery cell is performed on the basis of the comparison with the predetermined voltage value.

4. A maturation process according to any one of the preceding claims, including taking a plurality of measurements between the start and the end of a maturation period, the plurality of measurements being taken at intervals.

5. The maturation process of claim 4, further comprising comparing a voltage difference between a first measurement and a second measurement of the plurality of measurements of open circuit voltage to a predetermined difference, wherein the step of determining the integrity of the at least one battery cell is based on the comparison to the predetermined difference.

6. The maturation process of claim 4 or 5, further comprising determining a voltage difference between a first measurement and a second measurement of the plurality of measurements of open circuit voltage; determining a time difference between the determined first measurement and the second measurement; and determining a voltage rate of change based on the voltage difference and the time difference, wherein the step of determining the integrity of the at least one battery cell is based on a comparison of the voltage rate of change to a predetermined rate of change.

7. A maturation process according to any one of the preceding claims, wherein at least three measurement values are taken, a voltage difference between adjacent pairs of measurement values is determined, thereby obtaining at least a first voltage difference and a second voltage difference, the maturation process comprising determining at least one discharge phase based on at least the first voltage difference and the second voltage difference, the at least one discharge phase comprising a relaxation period.

8. The aging process of claim 7, wherein the step of determining the integrity of the at least one battery cell is performed based on at least one voltage measurement taken after the relaxation period.

9. A maturation process according to any one of the preceding claims, the plurality of measurements of the open circuit voltage of the at least one battery cell being taken at intervals to provide a trace of the open circuit voltage over time, the maturation process including comparing the trace with a predetermined trace to determine the end of the relaxation period, the step of determining the integrity of the at least one battery cell being performed on the basis of at least one open circuit voltage measurement taken after the end of the relaxation period.

10. A maturation process according to any one of the preceding claims, comprising taking at least one measured voltage value measured on the basis of a resistance when a load is connected between a positive terminal and a negative terminal of at least one battery cell, the internal resistance of said at least one battery cell being determined according to: the at least one resistance-based measured voltage value; and one of the measured current drawn by the load and the resistance of the load.

11. The curing process of claim 10, further comprising comparing the internal resistance to a predetermined resistance value, the determining the integrity of the at least one battery cell being based on the comparison to the predetermined resistance value.

12. The aging process of claim 10 or 11, further comprising determining a plurality of internal resistances at intervals based on measurements taken at respective times, the aging process comprising comparing a difference between two internal resistances to a predetermined internal resistance difference value, wherein determining the integrity of the at least one battery cell is based on the comparison to the predetermined internal resistance difference value.

13. The curing process of any one of claims 10-12, wherein the integrity is determined to be compromised if the determined rate of change of the internal resistance is greater than a predetermined rate of change of the internal resistance.

14. A maturation process according to any one of the preceding claims, further comprising measuring a temperature of the at least one battery cell and comparing the measured temperature with a predetermined temperature, the step of determining the integrity of the at least one battery cell being performed on the basis of the comparison with the predetermined temperature.

15. A maturation process according to any one of the preceding claims, further comprising measuring a first temperature and a second temperature at intervals, determining a temperature difference between the first measured temperature and the second measured temperature, and comparing the temperature difference with a threshold temperature difference, the step of determining the integrity of the at least one battery cell being performed on the basis of the comparison with the threshold temperature difference.

16. The curing process of any one of the preceding claims, further comprising determining a second derivative with respect to time of at least one of: a measured open circuit voltage; an internal resistance determined for the at least one battery cell; and a measured temperature of the at least one battery cell, the step of determining the integrity of the at least one battery cell being performed based on an analysis of the second derivative.

17. The curing process of claim 16, wherein if said second derivative exceeds a predetermined limit, then integrity is determined to be compromised.

18. The curing process of claim 16 or 17, wherein integrity is determined to be compromised if the second derivative is one of: less than a first predetermined second derivative; and greater than the second predetermined second derivative.

19. A maturation process according to any one of the preceding claims, wherein the step of determining the integrity of the at least one battery unit is performed in the measuring device, the result of the step of determining the integrity of the at least one battery unit being transmitted to a central computing device at a remote location, the result comprising identifying the at least one battery unit as integrity compromised.

20. A maturation process according to any one of the preceding claims, further comprising providing a battery unit removal signal in dependence of the step of determining the integrity of the at least one battery unit.

21. The maturation process according to any one of the preceding claims, said maturation period being of multiple days, at least one week, at least two weeks or at least three weeks duration.

22. A maturation process according to any one of the preceding claims, the at least one battery cell being subjected to a temperature above room temperature, above 25 ℃, above 30 ℃ or above 35 ℃ during the maturation period.

23. A maturation process according to any one of the preceding claims, the maturation period comprising at least a part of the shipping period.

24. A maturation process according to any one of the preceding claims, said measuring means being comprised in said at least one battery cell.

25. The maturation process of claim 24, said measuring device being included in the structure of said at least one battery cell, whereby said measuring device is part of said at least one battery cell.

26. A maturation process according to any one of the preceding claims, the at least one battery cell comprising a lithium-ion electrochemical device.

27. A manufacturing method for at least one battery cell, the manufacturing method comprising: a formation charging process performed on the at least one battery cell, and a maturation process based on any of the preceding claims performed on the at least one battery cell.

Technical Field

The present invention relates to a method for maturing at least one battery cell, and in particular, but not exclusively, to a process for maturing a battery comprising at least one battery cell.

Background

After the battery, such as a lithium ion battery, is manufactured, the battery needs to undergo a formation charging process. Formation charging constitutes the first charge cycle of a newly manufactured battery, involving subjecting the battery to finely controlled charge and discharge cycles to prepare the battery for use. Thereafter, the battery is often subjected to a maturation (aging) process before use. Maturation is sometimes referred to as aging. One purpose of the maturation process is to identify weak or defective cells before they are put into use.

The maturation process involves measuring the open circuit voltage of each cell, storing the cells for a maturation period of up to several weeks, and measuring the open circuit voltage of each cell after the maturation period. If the drop in open circuit voltage from a measurement before the maturation period to a measurement after the maturation period is greater than a predetermined voltage, the cell will be deemed unsuitable for use and rejected. The purpose of the ripening process is to detect defects such as excessive self-discharge rate, electrolyte seal leakage, mechanical defects, excessive internal resistance, and malformed solid electrolyte interface layer (SEI). This defect usually takes some time to become apparent, and so the maturation period is usually prolonged. Maturation is typically performed on higher value batteries and may be performed on the battery itself, on a stack of battery cells or on individual battery cells.

The present inventors have recognized that there are disadvantages to existing curing processes. The present invention was devised in light of the inventors' recognition of these shortcomings. It is therefore an object of the present invention to provide an improved maturation process for at least one battery cell.

Disclosure of Invention

According to a first aspect of the present invention, there is provided a maturation process for at least one battery cell, the process comprising:

charging the at least one battery cell;

subjecting the at least one battery cell to a maturation period of at least one day, wherein no electrical load is connected to the at least one battery cell other than the measuring device;

taking at least one measurement of the open circuit voltage of the at least one battery cell between the beginning and the end of the maturation period using a measuring device; and

determining an integrity of the at least one battery cell based on the at least one measurement.

The aging process includes charging the at least one battery cell. The at least one battery cell may be charged to a predetermined charge level, for example 30% of full capacity. The at least one battery cell may be charged at the end of the formation process in preparation for curing. Alternatively, the at least one battery cell may be charged in a step other than the steps involved in the formation process in preparation for curing. The maturation process further comprises subjecting the at least one battery cell to a maturation period of at least one day, wherein no electrical load is connected to the at least one battery cell other than the measuring device. The at least one battery cell may be stored in the storage region, for example during maturation. The maturation process further includes taking at least one measurement of an open circuit voltage of at least one battery cell between the beginning and the end of the maturation period using a measurement device. More specifically, the at least one measurement of the open circuit voltage may be taken after the onset of the maturation period and before the end of the maturation period. The maturing process further comprises determining the integrity of the at least one battery cell from the at least one measurement value.

Known maturation processes introduce a significant delay between the end of the formation process and the subsequent transport of the battery before it is put into use. Furthermore, the known maturation process requires a large storage space for the battery to undergo maturation. Delays and storage space requirements before subsequent shipments have a significant impact on cost increases. The inventors have recognized that cells with compromised integrity often become apparent before the end of the maturation period. The invention therefore relates to taking at least one measurement of the open-circuit voltage between the beginning and the end of the maturation period, so that a defective battery can be identified before the end of the maturation period.

The at least one measured value may be compared to a predetermined voltage value, and the step of determining the integrity of the at least one battery cell is based on the comparison. If at least one of the measured values is less than the predetermined voltage value, a determination may be made that the integrity is compromised. Thus, an excessively high internal self-discharge can be identified.

The maturation process may include taking a plurality of measurements between the beginning and the end of the maturation period, the plurality of measurements taken at intervals. The maturing process may further include comparing a voltage difference between a first measurement value and a second measurement value of the plurality of measurement values of the open circuit voltage to a predetermined difference value, and the step of determining the integrity of the at least one battery cell is performed based on the comparison. If the voltage difference is greater than the predetermined difference, then the integrity may be determined to be compromised. A time difference between the first measurement and the second measurement may be determined. The maturation process may determine the rate of change of voltage from the voltage difference and the time difference. Alternatively or additionally, the at least first and second measurement values may be compared to stored at least first and second reference measurement values. The discharge rate may be determined by comparison with a stored reference measurement. Thus, an excessively high internal self-discharge may be identified.

Furthermore, in case at least three measurement values are taken, the voltage difference between adjacent pairs of measurement values may be determined, thereby obtaining at least a first voltage difference and a second voltage difference. The curing process may include determining at least one discharge phase from the voltage differences. For example, the first voltage difference may represent a relaxation (relaxation) phase and the second voltage difference may represent a steady-state phase. By taking sufficient open circuit measurements during the battery maturation period, the discharge curve of the battery cell can be provided. For example, by measuring every hour during the aging period, the discharge curve can be well characterized. The step of determining the integrity of the at least one battery cell may be based on a confirmation of the at least one discharge phase. More specifically, the step of determining the integrity of the at least one battery cell may be based on at least one voltage measurement taken after a relaxation phase.

The first measurement may be taken at the beginning of the maturation period. In contrast, according to known maturation processes, the first measurement is taken before the maturation period and usually at the end of the formation period. The battery cell undergoes a relaxation period immediately after charging, so that an open-circuit voltage measurement performed immediately after charging, for example at the end of the formation process, may lead to a high first measurement value with misleading properties. The trace of the open circuit voltage measurement over time may be compared to a predetermined trace to determine the end of the relaxation period. The step of determining the integrity of the at least one battery cell may be based on an open circuit voltage measurement taken after the end of the relaxation period.

The maturing process may also include taking at least one voltage measurement based on the resistance measurement when a known resistance is connected between the positive terminal and the negative terminal of the at least one battery cell. The internal resistance of the at least one battery cell may be determined based on: a measurement of the open circuit voltage of the at least one battery cell (i.e., when the known resistance is not connected between the positive terminal and the negative terminal); a voltage measurement based on a resistance measurement when there is a known resistance connection; and the known resistance. Alternatively or additionally, the maturing process may include connecting a load, such as a FET, between the positive terminal and the negative terminal of the at least one battery cell. The internal resistance of the at least one battery cell may be determined from measurements of the voltage and current across the terminals when the load is connected. The maturing process may further include comparing the internal resistance to a predetermined resistance value, the step of determining the integrity of the at least one battery cell being based on a result of the comparison. If the internal resistance is greater than the predetermined resistance value, the integrity may be determined to be compromised. Insufficient or leaked electrolyte, poor welding of the electrodes, or improper SEI formation may result in excessive internal resistance.

Based on measurements taken at multiple times, a plurality of such internal resistances at intervals may be determined. The maturing process may include comparing a difference between the two internal resistances to a predetermined internal resistance difference, and the step of determining the integrity of the at least one battery cell is performed based on the comparison. If the difference between the two internal resistances is greater than a predetermined internal resistance difference, then the integrity may be determined to be compromised. More specifically, if the rate of change of the internal resistance is greater than the predetermined rate of change of the internal resistance, the integrity may be compromised. Electrolyte leakage may result in an excessively high rate of change of internal resistance.

The aging process may also include measuring a temperature of at least one of the battery cells. The step of determining the integrity of the at least one battery cell may be performed based on at least one temperature measurement. More specifically, the measured temperature may be compared to a predetermined temperature. If the measured temperature is greater than the predetermined temperature, it may be determined that the integrity is compromised. Alternatively or additionally, the first and second temperature measurements may be taken at spaced-apart times, a temperature difference between the first and second temperature measurements may be determined, and the temperature difference compared to a threshold temperature difference. If the temperature difference is greater than the threshold temperature difference, it may be determined that the integrity of the at least one battery cell is compromised. Internal short circuits may cause excessive temperatures.

The curing process may also include determining a second derivative of at least one of open circuit voltage, internal resistance, and temperature over time. The compromise of integrity can be determined from an analysis of the second derivative. More specifically, if the second derivative exceeds a predetermined limit, then the integrity may be determined to be compromised. Further, integrity damage may be determined if the second derivative is at least one of: less than a first predetermined second derivative; and greater than the second predetermined second derivative.

The step of determining the integrity of the at least one battery cell may be performed in a measuring device. The results of the step of determining the integrity of at least one battery unit may be transmitted to a remote location, and more particularly, to a central computing device of the remote location. The results may include identifying at least one battery cell as integrity compromised. Alternatively or additionally, the step of determining the integrity of the at least one battery unit may be performed at a location remote from the measurement apparatus, and more particularly, in a central computing device at a remote location. The result of the step of determining the integrity of the at least one battery cell may comprise identifying the at least one battery cell as integrity compromised.

In practice, the aging process may be performed simultaneously on each of the plurality of cell stacks. Thus, there may be communication from each of the plurality of cell stacks to a remote location.

The maturation process may further include providing a battery cell removal signal based on the step of determining the integrity of the at least one battery cell, and more specifically, providing a battery removal signal when the at least one battery cell is determined to have compromised integrity. The battery removal signal may be provided by the measurement device or a central computing device at a remote location. Providing a unit removal signal may include providing an operator perceptible output, such as through a display included in the central computing device. Thus, the operator may be informed of the need to remove at least one cell from the maturation process.

The maturation process may further include transmitting the results of the step of determining the integrity of the at least one battery cell to a remote location, and more specifically, to a central computing device at the remote location. The results of the step of determining the integrity of at least one battery cell may be wirelessly transmitted to a remote location. The measuring device may be configured accordingly as will be described below. The results may include identifying at least one battery cell as having compromised integrity.

The curing period can last for a plurality of days. More specifically, the maturation period may be at least one week, at least two weeks, or at least three weeks. During the aging period, more specifically, throughout the duration of the aging period, at least one battery cell may be subjected to temperatures above room temperature, more specifically, above 25 ℃, above 30 ℃ or above 35 ℃. The at least one battery cell may be stored in a temperature controlled environment during the maturation period. The maturation period may comprise at least a portion of the shipping period. The at least one battery cell may not be subjected to a temperature controlled environment during the shipping portion of the maturation period. Alternatively, where permitted, the at least one battery cell may be subjected to a temperature controlled environment during the shipping portion of the maturation period.

The aging process may be performed on a plurality of battery cells constituting one battery cell group. The cell stacks may be electrically connected to provide a desired voltage or current level, and after the aging process, may be used in a battery, and possibly with other cell stacks.

The measuring means may comprise voltage measuring means. The voltage measuring means may comprise a resistor connected across the terminals of the at least one battery cell, the resistor forming part of the voltage divider arrangement. The measurement arrangement may also comprise an analogue to digital converter which is operative to convert the analogue output of the voltage divider arrangement to digital form. The measurement device may also include a processor configured to perform the processes described herein. The processor may be a microcontroller. Alternatively, or in addition, the processor may include electronic circuitry in addition to or in place of the microcontroller that is configured to perform the processes described herein. Thus, the measurement device may include circuitry having structure and/or non-transitory memory having programming instructions for performing these processes.

The measurement device may further include a temperature sensor sensing a temperature of the at least one battery cell. The output of the temperature sensor may be converted to digital form as described above.

The measurement device may also include a load, such as a resistor or FET of known value, and switches operable to connect the load to the positive and negative terminals of the at least one battery cell.

The measurement apparatus may also include a communication device, and more particularly, may include a wireless communication device. The wireless communication device may be configured to provide radio frequency communication. The communication device may provide communication with a computing device at a remote location.

The measuring device may be comprised in at least one battery cell. More specifically, the measuring device may be included in the at least one battery cell at a previous stage of the manufacturing process, e.g. before the formation process. The measurement device may be included in the structure of the at least one battery cell such that the measurement device forms a portion of the at least one battery cell. The measurement device may be used during another part of the manufacturing process, for example during a formation charging process or during use.

The at least one battery cell may include a lithium ion electrochemical device, and more particularly, may include a lithium ion polymer electrochemical device.

The at least one battery cell may be included in a battery, whereby the battery is subjected to a maturing process.

According to a second aspect of the present invention, there is provided a manufacturing process for at least one battery, the manufacturing process comprising: performing a formation process on at least one battery cell; and a maturation process according to the first aspect of the invention.

Embodiments of the second aspect of the invention may include one or more features of the first aspect of the invention.

According to another aspect of the present invention, there is provided a process for maturing at least one battery cell, the process comprising: charging at least one battery cell; subjecting the at least one battery cell to a maturation period of at least one day, wherein no electrical load is connected to the at least one battery cell other than the measuring device; obtaining at least one measurement of the open circuit voltage of the at least one battery cell using a measurement device; and determining the integrity of the at least one battery cell from the at least one measurement.

Embodiments of another aspect of the present invention may include one or more features of the first aspect of the invention.

Drawings

Other features and advantages of the present invention will become apparent from the following detailed description, given by way of example only and with reference to the accompanying drawings, in which:

fig. 1 is a block diagram of a battery manufacturing process including a maturing process according to one embodiment of the present invention;

FIG. 2 is a schematic representation of a cell and measuring device used in the maturation process;

FIG. 3 is a diagrammatic view of a maturing device comprising a plurality of batteries;

FIG. 4 is a first graph of open circuit voltage versus time for a battery;

FIG. 5 is a second graph of open circuit voltage versus time for a battery;

FIG. 6 is a third graph of open circuit voltage versus time for a battery;

FIG. 7 shows a graph of discharge rate as characteristic of a non-damaged cell and a graph of discharge rate as characteristic of a damaged cell; and

fig. 8 shows a graph of the rate of change of the discharge rate as characteristic of a non-damaged battery.

Detailed Description

Fig. 1 shows a block diagram of a battery manufacturing process including a maturing process according to one embodiment of the present invention. The battery manufacturing process 10 begins with the manufacture of an electrode 12, followed by a stack 14, and then an assembly 16. The assembled structure is then filled with electrolyte and sealed 18. Thereafter, the battery is subjected to a formation charging process 20. The formation charging process 20 constitutes a first charging cycle for a newly manufactured battery and involves subjecting the battery to finely controlled charging and discharging cycles to prepare the battery for use. When the formation charging process is complete, the battery undergoes a maturation process 22. The curing process 22 will be described in detail below. When the maturation process 22 is complete, the cells are packaged and shipped 24 for subsequent use. Although the present specification describes a battery with reference to fig. 1 to 3, the present specification is equally applicable to a battery cell or a pack formed by connecting battery cells.

Fig. 2 shows a battery and measuring device 30 used during the maturation process 22. The measurement device 30 is connected across the positive and negative terminals of the battery 32. At an early stage of the manufacturing process 10, such as during assembly 16, the measurement device 30 is included in the battery 32, wherein the measurement device operates during the formation charging process 20, during the maturation process 20, and during battery use after packaging and shipping 24. The measurement device 30 includes measurement circuitry 34. The measurement circuit 34 includes a voltage measurement device, a temperature sensor, an analog-to-digital converter that converts the analog output from each voltage divider device and temperature sensor to digital form, and a processor that receives and processes the digital signals received from the analog-to-digital converter. The voltage measuring means comprises a first resistor of known value connected across the terminals of the battery and forming part of a voltage divider arrangement. The temperature sensor is provided in the battery to sense a temperature of the battery.

The measurement device 30 further includes a second resistor 36 of known value and an electrically actuated switch 38, the electrically actuated switch 38 being operable to connect the second resistor across the positive and negative terminals of the battery in parallel with the first resistor of the voltage divider arrangement. The second resistor 36 is connected to or disconnected from the positive and negative terminals by a switch 38, which is controlled by the processor. The connection and disconnection of the second resistor 36 is used for measurement of the internal resistance of the battery. When the second resistor 36 is disconnected, the first voltage is measured by the measurement circuit 34, and when the second resistor is connected, the second voltage is measured by the measurement circuit. In view of the resistance values of the first and second resistors being known, the processor is operable to determine a difference between the first and second voltages and to determine the internal resistance on the basis thereof. In the alternative, a FET is used instead of the second resistor, and when the FET is connected, the voltage and current between the terminals are measured. The design of the current measurement circuit is within the ordinary design capabilities of those skilled in the art. The internal resistance depends on the measured current and the measured voltage.

The measurement device 30 also includes a radio frequency communication transceiver 40 that provides data communication with the measurement device. In a first form, the data transmitted from the measurement device includes battery status data. The battery status data includes a battery cell removal signal that is generated by the processor if it is determined during the maturation process that the integrity of the battery cell is compromised. The integrity of the battery is determined to be compromised based on a determination of the integrity of the battery as will be described below. In a second form, the data transmitted from the measurement device includes periodic voltage, temperature and internal resistance measurements when the battery integrity measurement is performed elsewhere.

Fig. 3 shows a maturing device 50. The maturing device 50 comprises a plurality of batteries 52 which are stored in a temperature controlled environment during the maturing process. During the maturation process, the temperature controlled environment was maintained at a temperature of 40 ℃. The duration of the maturation process may be between several days and one month depending on the type of battery 52 undergoing maturation. Each cell 52 may be as described above with reference to fig. 2. In addition, the positive and negative terminals of each battery 52 are not electrically connected to an external device, whereby the measurement device 30 applies a unique electrical load to the battery. A radio frequency antenna 54 in the form of a strip is disposed to extend adjacent the radio frequency communications transceiver 40 of each of the plurality of batteries 52. The radio frequency antenna 54 is electrically coupled to a communication interface module 56 that is installed in a temperature controlled environment. The plurality of cells 52 are thus electrically isolated from each other.

The communication interface module 56 is in data communication with a remote computing device 58. The remote computing device 58 is operable to provide supervisory control of the measurement apparatus 30 contained in each of the plurality of batteries 52. The remote computing device 58 is operable to receive data from the measurement apparatus 30 included in each of the plurality of batteries 52. According to the first form described above, if it is determined that the integrity of the battery is compromised, the remote computing device 58 receives battery status data including a battery unit removal signal. The remote computing device 58 provides a perceptible output to the operator via, for example, a display included in the central computing device, upon receipt of the battery unit removal signal. The operator is thus informed of the need to remove the problematic battery from the maturation process. According to the second form described above, the remote computing device 58 receives data transmitted from the measurement apparatus, including periodic voltage, temperature and internal resistance measurements. The periodic voltage, temperature and internal resistance measurements are processed in the remote computing device 58 for battery integrity determinations as described below. Upon identifying a compromised integrity battery, the remote computing device 58 is operable to provide a perceptible output to the operator whereby the operator is informed of the need to remove the problematic battery from the curing process.

Referring to fig. 4-6, a description is provided herein of a battery integrity measurement performed during the aging process 20. Fig. 4 shows a first graph of the open circuit voltage of a battery as a function of time. As indicated by the circles in fig. 4, the open circuit voltage of the battery is measured periodically, and the measuring device 30 measures the open circuit voltage from t₀Start to t_endAnd (6) ending. The battery undergoes a relaxation period immediately after charging, and open circuit voltage measurements taken after charging are therefore prone to misleading high measurements, leading to false determinations of compromised integrity. Periodically measuring the open circuit voltage provides a determination of the trace of the open circuit voltage over time. The early part of the trajectory is analyzed to determine the end of the relaxation period. The horizontal dashed line 72 in fig. 4 indicates the end of the relaxation period. The determination of the end of the relaxation period will be described below with reference to fig. 5. The self-discharge rate is then determined based on the open circuit voltage measurement taken after the end of the relaxation period, thereby determining t, indicated by the vertical dashed line 74, at the end of the relaxation period_endThe open circuit voltage drop av in between. Further, the open circuit voltage trace after the end of the relaxation period is compared with a predetermined trace to identify an abnormal trace that may indicate an increase in internal resistance, improper SEI formation, insufficient or leaking electrolyte, and an internal short circuit. The trajectory comparison may provide identification of a battery with compromised integrity prior to the end of the maturation period.

Fig. 5 shows a second graph of the open circuit voltage of the battery as a function of time. Fig. 5 is used to illustrate the relaxation period. t is t₀And t_sThe time in between constitutes the later part of the relaxation period. As can be seen from fig. 5, t₀And t_endThe open circuit voltage drop between Δ V is significantly higher than t_sAnd t_endAnd thus av is misleading high. As described above, the end of the relaxation period is determined as the basis for determining a more accurately reflective open circuit voltage drop. The end of the relaxation period is determined by comparing the early portion of the open circuit voltage trace with a predetermined trace that is characteristic of relaxation for this type of battery.

FIG. 6 shows the open circuit voltage of a battery over timeA third graph of variation. Fig. 6 is used to illustrate the identification of a battery with compromised integrity early in the maturation period. As shown by the upper dashed line 76 in fig. 6, where the open circuit voltage measurement is from t₀Is initiated, wherein the relaxation period has been at t₀And (6) ending. The lower dashed line 78 in fig. 6 indicates a predetermined voltage threshold for determining an over-discharge. As can be seen from FIG. 6, multiple measurements of the open circuit voltage during the maturation period provided a measure of the open circuit voltage at t which was about 20% of the total maturation period_fDetection of a time crossing a predetermined voltage threshold. In contrast, known ripening processes determine the presence of an over-discharge only after the end of the ripening period.

Five different scenarios involving integrity damage will now be described. For these five cases, two typical cells, cell a and cell B, have the following characteristics at 25 ℃:

characteristics of	Battery unit A	Battery unit B
			Capacity 'C'	50Ah	40Ah
Technique of	LFP	NMC
			Vnom	3.2V	3.7V
VMax	3.65V	4.2V
			Vmin	2.5V	2.7V
Rint (internal resistance)	[email protected]％SOC	1.5mOhm at 50％SOC

First case

The internal self-discharge is too high so that the open circuit voltage drops beyond a predetermined voltage after a period of time. Here, the open circuit voltage of the battery cell is measured at certain time intervals, and the voltage variation is compared with a threshold voltage difference:

second case

The internal self-discharge is too high and thus the gradient of the open circuit voltage with time is too high. By tracking the trajectory, it is determined when the battery is in a relaxation period, steady state, or self-discharging. At 30% SOC after battery relaxation, the following discharge rate limits are expected:

the discharge is not measured directly, but rather uses the open circuit voltage as an indication of the discharge. The discharge rate is related to the open circuit voltage by a graph shown in fig. 7. The open circuit voltage over time is compared to a predetermined upper limit 80 curve and a predetermined lower limit 82 curve to determine whether the open circuit voltage falls between the upper limit curve and the lower limit curve. The first curve 84 in fig. 7 falls between the upper limit curve 80 and the lower limit curve 82 and is therefore determined not to be integrity compromised. The second curve 86 in fig. 7 falls below the lower limit curve 82 and is therefore determined to be integrity compromised. The upper limit curve 80 and the lower limit curve 82 are characteristics for a particular battery type. In addition, the second derivative of the open circuit voltage with respect to time is also analyzed to reveal further information, such as the change between the positive and negative rates of change, which is indicative of a damaged cell. The use of the second derivative is shown in fig. 8. The second derivative of the open circuit voltage is compared to predetermined upper and lower rate limit 90, 92 curves to determine whether the second derivative falls between the upper and lower rate limit curves. As can be seen in fig. 8, the example curve 94 falls between the upper rate limit 90 and lower rate limit 92 curves, and thus no integrity penalty is determined in this regard.

Third case

The internal resistance is too high to be above a predetermined threshold. As described above, this may be due to insufficient/leaked electrolyte, poor electrolyte welding, or improper SEI formation. For a 1 ohm second resistor, the open circuit voltage is measured when the second resistor is disconnected and again when the second resistor is connected, as described above. In some cases, and where the measured current has sufficient effect, other integrity tests described herein are suitable to take the measured current into account.

Fourth case

The gradient of the internal resistance change with time is too large. This may be caused by electrolyte leakage. Multiple internal resistance measurements are made over time.

Fifth case

The battery has an internal short circuit and thus causes a change in the temperature of the battery cell greater than a threshold value. The temperature is measured at intervals as described above and compared to a threshold value.