Cylindrical cell high and low temperature discharge capacity test method and effect evaluation method

Abstract

The invention discloses a cylindrical cell high and low temperature discharge capacity test method and effect evaluation method, and relates to the technical field of new energy automobile and lithium battery test.The test method comprises the steps that a cylindrical cell sample to be tested is obtained, and after multiple times of charge and discharge cycles, multiple times of cycle charge and discharge tests at different temperatures are sequentially conducted after the performance of the cell is stable; in each cycle of charging and discharging test process, a cylindrical battery cell sample to be tested is fully charged at a constant current at a normal temperature, and discharging at different temperatures is carried out after a set time; wherein the discharge temperatures are increased in sequence in the multiple times of cyclic charge and discharge test processes, and the clamp is used according to different conditions in the test process according to different discharge temperatures; testing is completed after multiple times of cyclic charging and discharging, and the discharging capacity of the to-be-tested cylindrical battery cell sample is obtained. The high and low temperature discharge performance of the cylindrical battery cell can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles and lithium battery testing, and in particular to a high and low temperature discharge capacity testing method and an effect evaluation method for a cylindrical battery cell. Background Art

[0002] Cylindrical cells occupy an important position in the field of new energy vehicle batteries with their unique design and excellent performance. The standardized design of cylindrical cells enables them to achieve a high degree of automation in the production process, thereby reducing costs and improving production efficiency. However, in the face of complex and changeable usage environments, the performance stability of cylindrical cells is the key to whether they can gain a foothold in the market. To this end, high and low temperature discharge capacity testing has become an indispensable part of evaluating the performance of cylindrical cells. High and low temperature discharge capacity testing refers to the performance testing of cells under extreme temperature conditions, including high temperature and low temperature. The high temperature discharge capacity test mainly examines the discharge performance of the cell under high temperature conditions, while the low temperature discharge capacity test focuses on evaluating the discharge capacity of the cell under low temperature conditions. Through this test, the stability and reliability of cylindrical cells in various extreme environments can be ensured, providing a solid guarantee for the safe driving of new energy vehicles. Therefore, high and low temperature testing, as a key link to ensure the stability of the performance of cylindrical cells, is of great significance to promoting the development of the new energy vehicle industry.

[0003] At present, the national standard GB / T31486-2015 provides a standard method for high and low temperature discharge capacity testing, namely: the low temperature discharge capacity test method is: a) standardized charging of the battery; b) the battery is placed at -20℃±2℃ for 24h; c) the battery is discharged at -20℃±2℃ with a current of 1I(A) until the voltage reaches the discharge termination voltage provided by the enterprise (the voltage value is not less than 80% of the room temperature discharge termination voltage); d) the discharge capacity is measured (in Ah); correspondingly, the high temperature discharge capacity test method is: a) standardized charging of the battery; b) the battery is placed at 55℃±2℃ for 5h; c) the battery is discharged at 55℃±2℃ with a current of 1I1(A) until the voltage reaches the room temperature discharge termination voltage; d) the discharge capacity is measured (in Ah).

[0004] In order to further improve the discharge test performance of cylindrical cells, current research has proposed a variety of methods for high and low temperature discharge testing of lithium-ion batteries. For example, CN118655487A proposed a lithium battery charge and discharge test method, which analyzes the performance evaluation coefficient of lithium batteries under constant current charging, constant voltage charging and discharging, and then obtains a comprehensive evaluation index of lithium battery performance testing through comprehensive analysis of multiple performance tests, thereby ensuring the reliability and stability of lithium batteries in practical applications. However, the above-mentioned existing test methods focus on the unification of test methods and conditions throughout the test process, and do not consider the impact of other factors on the test results under different circumstances, and fail to achieve a better discharge capacity test effect. Summary of the invention

[0005] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides a high and low temperature discharge capacity testing method and effect evaluation method for cylindrical battery cells. Taking into account that the clamp has different usage effects at different temperatures during the test process, the clamp is used according to different discharge temperatures in different test processes to perform capacity testing and improve the high and low temperature discharge performance of the cylindrical battery cells.

[0006] In a first aspect, the present invention provides a method for testing the high and low temperature discharge capacity of a cylindrical battery cell.

[0007] A method for testing the high and low temperature discharge capacity of a cylindrical battery cell, comprising:

[0008] Obtain a cylindrical battery sample to be tested, and perform multiple charge and discharge cycles at different temperatures after the battery performance is stable;

[0009] In each cycle charge and discharge test process, the cylindrical battery sample to be tested is first fully charged at a constant current at room temperature, and then discharged at different temperatures after a set time; the discharge temperature during the multiple cycle charge and discharge tests is increased successively, and the fixture is used according to the different discharge temperatures during the test;

[0010] The test is completed after multiple cycles of charge and discharge to obtain the discharge capacity of the cylindrical battery sample to be tested.

[0011] According to a further technical solution, during the test, the fixture is not used when the discharge temperature is lower than the set value, and the fixture is used when the discharge temperature is higher than the set value.

[0012] According to a further technical solution, the set value is a normal temperature of 25°C.

[0013] A further technical solution is that the discharge temperature during the multiple cycle charge and discharge tests is initially set to room temperature 25°C, and then each subsequent discharge temperature is raised sequentially from the lowest set temperature.

[0014] Further technical solutions, determination of the use of the clamp under different discharge temperatures, include:

[0015] Obtain multiple parallel cylindrical battery cell samples, and perform cyclic charge and discharge tests at different temperatures after multiple charge and discharge cycles, and after the battery cell performance is stable;

[0016] In each cycle charge and discharge test process, multiple cylindrical cell samples are first fully charged at a constant current at room temperature, and then discharged at different temperatures after a set time, and the discharge capacity of each discharge step is recorded; in the cycle charge and discharge test process, multiple cylindrical cell samples corresponding to the same are tested according to the use of multiple different fixtures;

[0017] According to the discharge capacity at different discharge temperatures and different fixtures, the capacity retention rate under normal temperature discharge conditions is calculated, and the improvement effect of discharge capacity under different temperatures and different fixtures is evaluated based on the capacity retention rate;

[0018] Determine the usage of the clamp under different discharge temperatures based on the lifting effect.

[0019] A further technical solution is that the various usage conditions of the various different clamps include: using the clamp throughout the entire test process, not using the clamp throughout the test process, not using the clamp when the discharge temperature during the test is lower than a set value and using the clamp when the discharge temperature is higher than a set value; the set value is room temperature 25°C.

[0020] According to a further technical solution, the higher the capacity retention rate, the better the effect of improving the discharge capacity.

[0021] A further technical solution is to set different fixture usage conditions based on different test fixture types, materials, and usage methods, and to develop and update the test method according to the effect of the fixture on improving the discharge capacity in different situations.

[0022] A further technical solution is to control the cell voltage within a set range during each cycle of charge and discharge testing. If the upper and lower limits of the set range are reached, the discharge test of the current step is stopped.

[0023] In a second aspect, the present invention provides a method for evaluating the effect of high and low temperature discharge capacity testing of a cylindrical battery cell.

[0024] A method for evaluating the high and low temperature discharge capacity test effect of a cylindrical battery cell, comprising:

[0025] Using the cylindrical battery cell high and low temperature discharge capacity test method proposed in the first aspect, the cylindrical battery cell sample to be tested is tested, and the discharge capacity of each discharge step in the cyclic charge and discharge test process at different temperatures is recorded;

[0026] According to the discharge capacity of each discharge step, the capacity retention rate under the normal temperature discharge condition is calculated;

[0027] Based on the capacity retention rate, the improvement effect on the discharge capacity under different temperatures and different fixture usage is evaluated. The improvement effect is used as the test result to evaluate the high and low temperature discharge capacity test method used.

[0028] One or more of the above technical solutions have the following beneficial effects:

[0029] 1. The present invention provides a method for testing the high and low temperature discharge capacity of cylindrical batteries. Taking into account that the clamp has different effects at different temperatures during the test, the clamp is used in different situations according to the different discharge temperatures during different test processes to perform capacity tests and improve the high and low temperature discharge performance of cylindrical batteries.

[0030] 2. The present invention provides a method for evaluating the test effect of high and low temperature discharge capacity of cylindrical batteries, which provides development guidance and effect evaluation support for subsequent improvements in fixtures and tooling, and improvements in fixture material performance. When the type, material, and usage method of the test fixture changes, the test method can be formulated and updated based on the effect of the fixture on improving the discharge capacity, and the test method can be re-evaluated, thereby effectively improving the high and low temperature discharge performance of cylindrical batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] Figure 1 The present invention is a flowchart of a method for testing the high and low temperature discharge capacity of a cylindrical battery cell according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are exemplary only, are intended to describe specific embodiments, are intended to provide further explanation of the present invention, and are not intended to limit exemplary embodiments according to the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art to which the present invention belongs. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] Embodiment 1

[0035] This embodiment provides a method for testing the high and low temperature discharge capacity of cylindrical cells. By performing a 0.33C rate discharge test under different common discharge temperature conditions, the test process determines whether to use a test fixture according to different test temperatures, records and compares the discharge capacity, calculates the capacity retention rate at different temperatures, and evaluates based on the capacity retention rate, thereby obtaining a test method that can determine whether to use a fixture based on the discharge temperature. Under this test method, the high and low temperature discharge performance of cylindrical cells can be improved. Figure 1 As shown, the method proposed in this embodiment includes the following steps:

[0036] Step S1, obtaining a cylindrical battery sample to be tested, and subjecting the sample to multiple charge and discharge cycles, and then sequentially performing multiple cycle charge and discharge tests at different temperatures after the performance of the battery is stable.

[0037] Specifically, six parallel samples of 30Ah cylindrical cells were selected and subjected to three conventional 0.33C charge and discharge cycles, and then tested after the battery performance stabilized.

[0038] Step S2, in each cycle charge and discharge test process, the cylindrical battery sample to be tested is first fully charged at a constant current at room temperature, and then discharged at different temperatures after a set time; wherein, the discharge temperature in the multiple cycle charge and discharge tests performed in sequence increases successively, and during the test process, the fixture is used according to different discharge temperatures.

[0039] Specifically, 6 cells are charged at 0.33C constant current at 25℃ (normal temperature) to fully charge the battery; set aside for 2 hours; discharge the cells at 0.33C to the discharge cut-off voltage at different temperatures; set aside for 2 hours; the above charging and discharging steps are cycled in the order of first normal temperature and then increasing temperature, that is, the above charging and discharging steps are cycled in the order of 25℃, -20℃, -10℃, 0℃, 10℃, 45℃, and 55℃. In the process of cyclic charge and discharge test, the fixture is used according to the situation, and the cell voltage is controlled within the set range (2.5V~4.2V). If the upper and lower limits of the set range are reached, the test of the current step is stopped.

[0040] Step S3, completing the test after multiple cycles of charge and discharge, and obtaining the discharge capacity of the cylindrical battery sample to be tested.

[0041] Furthermore, during the above test process, it is necessary to determine the use of the fixture under different discharge temperatures to ensure the improvement of the final test performance. The determination method includes:

[0042] First, obtain multiple parallel cylindrical battery cell samples, and after multiple charge and discharge cycles, perform cyclic charge and discharge tests at different temperatures in turn after the battery cell performance stabilizes.

[0043] Secondly, during each cycle charge and discharge test, multiple cylindrical battery cell samples are first fully charged at a constant current at room temperature, and then discharged at different temperatures after a set time, and the discharge capacity of each discharge step is recorded; among them, during the cycle charge and discharge test, the corresponding multiple cylindrical battery cell samples are tested separately according to the use of multiple different fixtures.

[0044] In this embodiment, the various different clamp usage conditions include: using the clamp during the entire test process, not using the clamp during the entire test process, not using the clamp when the discharge temperature is lower than the set value during the test process, and using the clamp when the discharge temperature is higher than the set value, etc. In this embodiment, the set value (i.e., the set temperature) is set to a normal temperature of 25°C. Preferably, the test conditions can be adjusted by comparing the test results under various different conditions, that is, the set temperature can be adjusted and selected according to the actual situation.

[0045] Specifically, this embodiment sets three different clamp usage conditions, uses 6 parallel cylindrical cells A to F and divides them into 3 groups, and performs discharge capacity tests at different temperatures under the three different conditions for the 3 groups of cylindrical cells. The specific test process is as follows:

[0046] (1) No fixture is used during the entire test process

[0047] (1.1) Take two 30Ah cylindrical cells A and B, and cycle them at 0.33C for three cycles. After the battery performance stabilizes, test it.

[0048] (1.2) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0049] (1.3) Set aside for 2 hours;

[0050] (1.4) Discharge the two batteries at 0.33C at 25°C to the discharge cut-off voltage;

[0051] (1.5) Set aside for 2 hours;

[0052] (1.6) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0053] (1.7) Set aside for 2 hours;

[0054] (1.8) Discharge the two batteries at 0.33C at -20°C to the discharge cut-off voltage;

[0055] (1.9) Set aside for 2 hours;

[0056] (1.10) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0057] (1.11) Set aside for 2 hours;

[0058] (1.12) Discharge the two batteries at 0.33C at -10°C to the discharge cut-off voltage;

[0059] (1.13) Set aside for 2 hours;

[0060] (1.14) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0061] (1.15) Set aside for 2 hours;

[0062] (1.16) Discharge the two batteries at 0.33C at 0°C to the discharge cut-off voltage;

[0063] (1.17) Set aside for 2 hours;

[0064] (1.18) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0065] (1.19) Set aside for 2 hours;

[0066] (1.20) Discharge the two batteries at 0.33C at 10°C to the discharge cut-off voltage;

[0067] (1.21) Set aside for 2 hours;

[0068] (1.22) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0069] (1.23) Set aside for 2 hours;

[0070] (1.24) Discharge the two batteries at 0.33C at 45°C to the discharge cut-off voltage;

[0071] (1.25) Set aside for 2 hours;

[0072] (1.26) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0073] (1.27) Set aside for 2 hours;

[0074] (1.28) Discharge the two batteries at 0.33C at 55°C to the discharge cut-off voltage;

[0075] (1.29) Set aside for 2h.

[0076] The above test process does not use a fixture, and the battery voltage is controlled in the range of 2.5V to 4.2V. If the upper and lower limits are reached, the test of this step is stopped. During the test, the discharge capacity of each discharge step is recorded, and the capacity retention rate under the discharge condition of 25°C is calculated.

[0077] (2) The fixture is used throughout the test process

[0078] (2.1) Take two 30Ah cylindrical cells C and D, and cycle them at 0.33C for three cycles. After the battery performance stabilizes, test it.

[0079] (2.2) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0080] (2.3) Leave for 2 hours;

[0081] (2.4) Discharge the two batteries at 0.33C using a fixture at 25°C to the discharge cut-off voltage; (2.5) Leave for 2 hours;

[0082] (2.6) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0083] (2.7) Set aside for 2 hours;

[0084] (2.8) Discharge the two batteries at -20°C using a fixture at 0.33C to the discharge cut-off voltage; (2.9) Leave for 2 hours;

[0085] (2.10) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0086] (2.11) Leave for 2 hours;

[0087] (2.12) Discharge the two batteries at -10°C using a fixture at 0.33C to the discharge cut-off voltage; (2.13) Leave for 2 hours;

[0088] (2.14) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0089] (2.15) Set aside for 2 hours;

[0090] (2.16) Discharge the two batteries at 0.33C using a fixture at 0°C to the discharge cut-off voltage; (2.17) Leave for 2 hours;

[0091] (2.18) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0092] (2.19) Set aside for 2 hours;

[0093] (2.20) Discharge the two batteries at 0.33C using a fixture at 10°C to the discharge cut-off voltage; (2.21) Leave for 2 hours;

[0094] (2.22) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0095] (2.23) Set aside for 2 hours;

[0096] (2.24) Discharge the two batteries at 0.33C using a fixture at 45°C to the discharge cut-off voltage; (2.25) Leave for 2 hours;

[0097] (2.26) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0098] (2.27) Set aside for 2 hours;

[0099] (2.28) Discharge the two batteries at 0.33C using a fixture at 55°C to the discharge cut-off voltage; (2.29) Leave them for 2 hours.

[0100] The above test process uses a fixture to control the battery voltage range of 2.5V to 4.2V. If the upper and lower limits are reached, the test of this step is stopped. During the test, the discharge capacity of each discharge step is recorded, and the capacity retention rate under the discharge condition of 25°C is calculated.

[0101] (3) During the test, the fixture is not used when the discharge temperature is less than or equal to 25°C, and the fixture is used when the discharge temperature is higher than 25°C

[0102] (3.1) Take two 30Ah cylindrical cells E and F, and cycle them at 0.33C for three cycles. After the battery performance stabilizes, test it.

[0103] (3.2) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0104] (3.3) Leave for 2 hours;

[0105] (3.4) Discharge the two batteries at 0.33C at 25°C to the discharge cut-off voltage;

[0106] (3.5) Leave for 2 hours;

[0107] (3.6) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0108] (3.7) Leave for 2 hours;

[0109] (3.8) Discharge the two batteries at 0.33C at -20°C to the discharge cut-off voltage;

[0110] (3.9) Set aside for 2 hours;

[0111] (3.10) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0112] (3.11) Leave for 2 hours;

[0113] (3.12) Discharge the two batteries at 0.33C at -10°C to the discharge cut-off voltage;

[0114] (3.13) Set aside for 2 hours;

[0115] (3.14) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0116] (3.15) Set aside for 2 hours;

[0117] (3.16) Discharge the two batteries at 0.33C at 0°C to the discharge cut-off voltage;

[0118] (3.17) Set aside for 2 hours;

[0119] (3.18) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0120] (3.19) Set aside for 2 hours;

[0121] (3.20) Discharge the two batteries at 0.33C at 10°C to the discharge cut-off voltage;

[0122] (3.21) Set aside for 2 hours;

[0123] (3.22) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0124] (3.23) Set aside for 2 hours;

[0125] (3.24) Discharge the two batteries at 0.33C using a fixture at 45°C to the discharge cut-off voltage;

[0126] (3.25) Set aside for 2 hours;

[0127] (3.26) Charge the two batteries at 0.33C constant current at 25°C until the batteries are fully charged;

[0128] (3.27) Set aside for 2 hours;

[0129] (3.28) Discharge the two batteries at 0.33C using a fixture at 55°C to the discharge cut-off voltage;

[0130] (3.29) Set aside for 2 h.

[0131] During the above test, the fixture is not used at the discharge temperatures of 25℃, -20℃, -10℃, 0℃, and 10℃, and the fixture is used at the discharge temperatures of 45℃ and 55℃. The battery voltage is controlled within the range of 2.5V to 4.2V. If the upper and lower limits are reached, the test of this step is stopped. During the test, the discharge capacity of each discharge step is recorded, and the capacity retention rate relative to the discharge condition of 25℃ is calculated.

[0132] Finally, according to the discharge capacity at different discharge temperatures and different fixtures, the capacity retention rate under normal temperature discharge conditions was calculated, and the improvement effect of discharge capacity under different temperatures and different fixtures was evaluated according to the capacity retention rate. Among them, the higher the capacity retention rate, the better the improvement effect on discharge capacity.

[0133] Specifically, the discharge capacity under different discharge temperatures and different clamp usage conditions was recorded, and the capacity retention rate of the acquirer relative to the normal temperature discharge condition was calculated, as shown in Table 1 below.

[0134] Table 1 Capacity retention rate of each cylindrical battery sample under different conditions and different discharge temperatures

[0135]

[0136] Furthermore, the effect of using the clamp can be evaluated by comparing the discharge capacity with and without the clamp during the whole process. That is, by calculating the capacity retention rate when the clamp is used minus the capacity retention rate when the clamp is not used, the effect of the clamp on improving the discharge capacity at different temperatures can be obtained.

[0137] Specifically, a comparison process is performed based on the data in Table 1 above, and the average discharge capacity retention rate of cylindrical battery samples C and D at different temperatures is subtracted from the average discharge capacity retention rate of cylindrical battery samples A and B. The results are shown in Table 2 below.

[0138] Table 2 Effect of using a fixture on discharge capacity improvement at different temperatures

[0139]

[0140] Similarly, by comparing the discharge capacity of each discharge step in the test results of using the fixture in different situations with the capacity retention rate of each discharge step without using (or using) the fixture in the whole process, the test improvement effect of the new test method can be obtained.

[0141] Specifically, according to the data in Table 1 above, a comparison process is performed, the average value of the discharge capacity retention rate of cylindrical battery samples E and F at different temperatures is subtracted from the average value of the discharge capacity retention rate of cylindrical battery samples A and B, and the average value of the discharge capacity retention rate of cylindrical battery samples E and F at different temperatures is subtracted from the average value of the discharge capacity retention rate of cylindrical battery samples C and D. The results are shown in Table 3 below.

[0142] Table 3 Discharge capacity improvement effect at different temperatures when using different fixtures

[0143]

[0144] Finally, the use of the fixture under different discharge temperatures is determined based on the above-mentioned improvement effect. Specifically, according to the test results, it can be obtained that when the discharge temperature is lower than the set value (25°C) during the test, the fixture is not used, that is, at -20°C, -10°C, 0°C, and 10°C, the discharge capacity of the cylindrical battery cell without the fixture is higher, and the discharge performance is better; when the discharge temperature is higher than the set value (25°C), the fixture is used, that is, at 45°C and 55°C, the discharge capacity of the cylindrical battery cell using the fixture is higher, and the discharge performance is better. That is, the fixture has a negative improvement effect on the discharge capacity at -20°C, -10°C, 0°C, and 10°C, and a positive improvement effect on the discharge capacity at 45°C and 55°C.

[0145] Based on the above analysis, the method for testing the discharge performance of cylindrical cells at different temperatures proposed in this embodiment can be obtained, which specifically includes:

[0146] (1) The battery cell is charged to full capacity at 0.33C constant current at 25°C;

[0147] (2) Set aside for 2 hours;

[0148] (3) Discharge at 0.33C at 25°C to the discharge cut-off voltage;

[0149] (4) Leave for 2 hours;

[0150] (5) Fully charge the battery at 0.33C constant current at 25°C;

[0151] (6) Set aside for 2 hours;

[0152] (7) Discharge at 0.33C to the discharge cut-off voltage without using a fixture at -20°C;

[0153] (8) Set aside for 2 hours;

[0154] (9) Fully charge the battery at 0.33C constant current at 25°C;

[0155] (10) Leave for 2 hours;

[0156] (11) Discharge at 0.33C to the discharge cut-off voltage without using a fixture at -10°C;

[0157] (12) Set aside for 2 hours;

[0158] (13) Fully charge the battery at 0.33C constant current at 25°C;

[0159] (14) Set aside for 2 hours;

[0160] (15) Discharge at 0.33C without a fixture to the discharge cut-off voltage at 0°C;

[0161] (16) Set aside for 2 hours;

[0162] (17) Fully charge the battery at 0.33C constant current at 25°C;

[0163] (18) Set aside for 2 hours;

[0164] (19) Discharge at 0.33C to the discharge cut-off voltage without using a fixture at 10°C;

[0165] (20) Set aside for 2 hours;

[0166] (21) Fully charge the battery at 0.33C constant current at 25°C;

[0167] (22) Set aside for 2 hours;

[0168] (23) Discharge at 0.33C using a fixture at 45°C to the discharge cut-off voltage;

[0169] (24) Set aside for 2 hours;

[0170] (25) Fully charge the battery at 0.33C constant current at 25°C;

[0171] (26) Set aside for 2 hours;

[0172] (27) 0.33C discharge to the discharge cut-off voltage at 55°C without using a fixture;

[0173] (28) Set aside for 2 hours;

[0174] (29)The test is completed.

[0175] As another implementation mode, different fixture usage conditions are set based on different test fixture types, materials, and usage methods, and test methods are developed and updated according to the effect of the fixture on improving the discharge capacity in different situations. For example, the effect of the fixture is evaluated by comparing the discharge capacity when the fixture is used throughout the process with that when the fixture is not used throughout the process. Based on the effect of the fixture on improving the discharge capacity, a temperature point suitable for using the fixture is found to develop and update the test method. After obtaining a new test method, the discharge capacity of each discharge step in the results obtained by the new test method is compared with the capacity retention rate of each discharge step when the fixture is not used (or used) throughout the process, so as to obtain the test improvement effect of the new test method.

[0176] Embodiment 2

[0177] This embodiment provides a method for evaluating the high and low temperature discharge capacity test effect of a cylindrical battery cell, which specifically includes the following steps:

[0178] (1) Using the cylindrical battery cell high and low temperature discharge capacity test method proposed in Example 1, the cylindrical battery cell sample to be tested is tested, and the discharge capacity of each discharge step in the cyclic charge and discharge test process at different temperatures is recorded;

[0179] (2) Calculate the capacity retention rate under normal temperature discharge conditions based on the discharge capacity of each discharge step;

[0180] (3) Based on the capacity retention rate, the improvement effect on the discharge capacity under different temperatures and different fixture conditions is evaluated. The improvement effect is used as the test result to evaluate the high and low temperature discharge capacity test method adopted.

[0181] Specifically, after the test method proposed in the first embodiment, the discharge capacity of each discharge step is recorded, and the capacity retention rate under the discharge condition of 25°C is calculated. The discharge capacity improvement effect of the fixture at different temperatures can be obtained by subtracting the capacity retention rate of the fixture without using the fixture. Based on the capacity retention rate, the discharge capacity improvement effect under different discharge temperatures and different fixture usage conditions is evaluated. The improvement effect is used as the test effect to evaluate the adopted high and low temperature discharge capacity test method, wherein the higher the capacity retention rate, the better the test method.

[0182] The above description is only a preferred embodiment of the present invention. Although the specific implementation mode of the present invention is described in conjunction with the accompanying drawings, it is not a limitation of the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the protection scope of the present invention.

Claims

1. A method for testing the high and low temperature discharge capacity of a cylindrical battery cell, characterized in that: include: Obtain a cylindrical battery sample to be tested, and perform multiple charge and discharge cycles at different temperatures after the battery performance is stable; In each cycle charge and discharge test process, the cylindrical battery sample to be tested is first fully charged at a constant current at room temperature, and then discharged at different temperatures after a set time; the discharge temperature during the multiple cycle charge and discharge tests is increased successively, and the fixture is used according to the different discharge temperatures during the test; The test is completed after multiple cycles of charge and discharge to obtain the discharge capacity of the cylindrical battery sample to be tested.

2. A method for testing the high and low temperature discharge capacity of a cylindrical battery cell as claimed in claim 1, characterized in that: During the test, the fixture is not used when the discharge temperature is lower than the set value, and the fixture is used when the discharge temperature is higher than the set value.

3. A method for testing the high and low temperature discharge capacity of a cylindrical battery cell as claimed in claim 2, characterized in that: The set value is the normal temperature of 25°C.

4. A method for testing the high and low temperature discharge capacity of a cylindrical battery cell as claimed in claim 1, characterized in that: For the discharge temperature during the multiple cycle charge and discharge tests performed sequentially, the first discharge temperature is room temperature 25°C, and then each discharge temperature increases sequentially from the lowest set temperature.

5. A method for testing the high and low temperature discharge capacity of a cylindrical battery cell as claimed in claim 1, characterized in that: Determination of fixture usage under different discharge temperatures, including: Obtain multiple parallel cylindrical battery cell samples, and perform cyclic charge and discharge tests at different temperatures after multiple charge and discharge cycles, and after the battery cell performance is stable; In each cycle charge and discharge test process, multiple cylindrical cell samples are first fully charged at a constant current at room temperature, and then discharged at different temperatures after a set time, and the discharge capacity of each discharge step is recorded; in the cycle charge and discharge test process, multiple cylindrical cell samples corresponding to the same are tested according to the use of multiple different fixtures; According to the discharge capacity at different discharge temperatures and different fixtures, calculate the capacity retention rate relative to normal temperature discharge conditions, and evaluate the improvement effect of discharge capacity at different temperatures and different fixtures based on the capacity retention rate; Determine the usage of the clamp under different discharge temperatures based on the lifting effect.

6. A method for testing the high and low temperature discharge capacity of a cylindrical battery cell as claimed in claim 5, characterized in that: The various different usage conditions of the clamps include: using the clamps throughout the entire test process, not using the clamps throughout the test process, not using the clamps when the discharge temperature during the test is lower than a set value and using the clamps when the discharge temperature is higher than a set value; the set value is room temperature 25°C.

7. A method for testing the high and low temperature discharge capacity of a cylindrical battery cell as claimed in claim 5, characterized in that: The higher the capacity retention rate, the better the effect of improving the discharge capacity.

8. A method for testing the high and low temperature discharge capacity of a cylindrical battery cell as claimed in claim 5, characterized in that: Based on different test fixture types, materials, and usage methods, different fixture usage conditions are set, and test methods are developed and updated according to the effect of the fixture on the discharge capacity improvement in different situations.

9. A method for testing the high and low temperature discharge capacity of a cylindrical battery cell as claimed in claim 1, characterized in that: During each cycle of charge and discharge test, the cell voltage is controlled within the set range. If the upper and lower limits of the set range are reached, the discharge test of the current step is stopped.

10. A method for evaluating the high and low temperature discharge capacity test effect of a cylindrical battery cell, characterized in that: include: Using the high and low temperature discharge capacity test method for cylindrical batteries as described in any one of claims 1 to 9, the cylindrical battery sample to be tested is tested, and the discharge capacity of each discharge step in the cyclic charge and discharge test process at different temperatures is recorded; According to the discharge capacity of each discharge step, the capacity retention rate under the normal temperature discharge condition is calculated; Based on the capacity retention rate, the improvement effect on the discharge capacity under different temperatures and different fixture usage is evaluated. The improvement effect is used as the test result to evaluate the high and low temperature discharge capacity test method adopted.

Images