A method and device for evaluating the cycle performance of lithium-ion batteries

Abstract

The present invention discloses a method and device for evaluating the cycle performance of lithium-ion batteries. The method includes the following steps: S110, pre-treating multiple lithium-ion batteries; S120, performing a coulombic efficiency test on each pre-treated lithium-ion battery under a first set condition; S130, determining the comparative coulombic efficiency of each lithium-ion battery that has completed the coulombic efficiency test under the current first set condition; S140, determining whether at least two lithium-ion batteries have the same comparative coulombic efficiency based on the comparative coulombic efficiency of each lithium-ion battery; if so, executing S150; if not, executing S160; S150, changing the current first set condition, performing a coulombic efficiency test on lithium-ion batteries with the same comparative coulombic efficiency under the changed first set condition, and then returning to S130; S160, outputting the numbers of the lithium-ion batteries in descending order of cycle performance. The present invention can use an ordinary charge and discharge tester to evaluate the cycle performance of multiple lithium-ion batteries.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method and device for evaluating the cycle performance of a lithium-ion battery. Background Art

[0002] Compared with traditional batteries, lithium-ion batteries are widely used in energy storage systems and electric vehicles due to their environmental friendliness, low pollution, long cycle life and no memory effect.

[0003] Coulombic efficiency, or charge-discharge efficiency, refers to the ratio of a battery's discharge capacity to its charge capacity during the same cycle. Because the amount of charged electricity often cannot be fully used to convert active materials into a charged state, but rather is partially consumed (for example, by irreversible side reactions), the coulombic efficiency is often less than 100%. For current lithium-ion batteries, the coulombic efficiency can generally reach 99.9% or above. However, the accuracy of ordinary charge-discharge equipment currently on the market is typically within 0.1%. The coulombic efficiencies of multiple lithium-ion batteries measured using ordinary charge-discharge equipment are all 99.9%, making it impossible to distinguish the cycling performance of these lithium-ion batteries.

[0004] The measurement accuracy of high-precision charging and discharging equipment can reach 0.001%, but its cost is high. Using high-precision charging and discharging equipment will increase the testing cost. Summary of the Invention

[0005] The present invention provides a method and device for evaluating the cycle performance of lithium-ion batteries, which can use a common charge and discharge tester to evaluate the cycle performance of multiple lithium-ion batteries.

[0006] According to one aspect of the present invention, a method for evaluating the cycle performance of a lithium-ion battery is provided, the method comprising the following steps:

[0007] S110, pre-processing the plurality of lithium-ion batteries so that the discharge capacity of each of the lithium-ion batteries after pre-processing exceeds a set threshold;

[0008] S120, numbering each of the lithium-ion batteries and performing a coulombic efficiency test on each of the lithium-ion batteries under a first set condition;

[0009] S130, determining the comparative coulombic efficiency of each of the lithium-ion batteries that completes the coulombic efficiency test under the current first set conditions;

[0010] S140, determining whether at least two of the lithium-ion batteries have the same comparative coulombic efficiency based on the comparative coulombic efficiency of each of the lithium-ion batteries;

[0011] If yes, execute S150; if no, execute S160;

[0012] S150, changing the current first setting condition, performing the coulombic efficiency test on the lithium-ion batteries with the same compared coulombic efficiency under the changed first setting condition, and then returning to S130;

[0013] S160 , outputting serial numbers of the lithium-ion batteries in descending order of cycle performance.

[0014] Optionally, the performing a coulombic efficiency test on each of the lithium-ion batteries under the first set conditions specifically includes:

[0015] placing each of the lithium-ion batteries in an environment with a first set temperature until the difference between the temperature of the lithium-ion battery and the first set temperature does not exceed a set threshold;

[0016] The lithium-ion battery is charged to a first set SOC with a first set current, and then discharged to a second set SOC with the first set current, and the cycle is repeated for a first set number of times.

[0017] Optionally, determining the comparative coulombic efficiency of each of the lithium-ion batteries that complete the coulombic efficiency test under the current first set condition specifically includes:

[0018] The comparative coulombic efficiency is determined according to an average value of the coulombic efficiencies obtained from the coulombic efficiency tests in a set order.

[0019] Optionally, the first set temperature includes 20-55°C;

[0020] The first set number of times includes 5-20 times;

[0021] The first set current includes 0.01C-0.1C.

[0022] Optionally, the changing the current first setting condition specifically includes:

[0023] The first set temperature and / or the first set current and the first set number of times are changed.

[0024] Optionally, the first set SOC includes 100%;

[0025] The second set SOC includes 0%.

[0026] Optionally, the pre-processing of the plurality of lithium-ion batteries specifically includes:

[0027] At a second set temperature, each of the lithium-ion batteries is subjected to a second set number of standard charges and discharges.

[0028] Optionally, the second set temperature includes 20-45°C;

[0029] The second set number of times includes 10-20 times.

[0030] Optionally, performing a second set number of standard charge and discharge operations on each of the lithium-ion batteries specifically includes:

[0031] The lithium-ion battery is charged to a charging voltage specified by the supplier using a charging current specified by the supplier, and then discharged to a discharge voltage specified by the supplier using a discharging current specified by the supplier, and the cycle is repeated for a second set number of times.

[0032] According to another aspect of the present invention, there is provided an apparatus for evaluating the cycle performance of a lithium-ion battery, the apparatus comprising: a pre-processing module, a testing module, a comparative coulombic efficiency determination module, a comparison module, a test condition changing module, and an output module;

[0033] The pre-processing module is used to pre-process the plurality of lithium-ion batteries so that the discharge capacity of each lithium-ion battery after pre-processing exceeds a set threshold;

[0034] The testing module is used to number each of the pre-treated lithium-ion batteries and perform a coulombic efficiency test on each of the lithium-ion batteries under a first set condition;

[0035] The comparative coulombic efficiency determination module is used to determine the comparative coulombic efficiency of each of the lithium-ion batteries that completes the coulombic efficiency test under the current first setting conditions;

[0036] The comparison module is configured to determine, based on the comparative coulombic efficiency of each of the lithium-ion batteries, whether at least two of the lithium-ion batteries have the same comparative coulombic efficiency;

[0037] The test condition changing module is used to change the current first set condition when the comparative coulombic efficiencies of at least two lithium-ion batteries are the same;

[0038] The testing module is further configured to perform a coulombic efficiency test on the lithium-ion batteries having the same comparative coulombic efficiency under the changed first setting conditions;

[0039] The output module is used to output the serial numbers of the lithium-ion batteries in descending order according to the cycle performance when the comparative coulombic efficiencies of any two lithium-ion batteries are different.

[0040] This embodiment provides a method for evaluating the cycling performance of lithium-ion batteries. The method includes: first, pre-treating a plurality of lithium-ion batteries. The pre-treating is performed to activate the lithium-ion batteries so that the discharge capacity of the lithium-ion batteries undergoing coulombic efficiency testing is in a stable state. The pre-treating is completed when the discharge capacity of the lithium-ion battery exceeds a set threshold. Next, a coulombic efficiency test is performed on each lithium-ion battery under first set conditions, and a comparative coulombic efficiency of each lithium-ion battery is determined. If the comparative coulombic efficiencies of any two lithium-ion batteries obtained from the coulombic efficiency test under the initial first set conditions are different, all lithium-ion batteries are directly numbered in descending order of cycling performance. If at least two of the comparative coulombic efficiencies obtained from the coulombic efficiency test under the initial first set conditions are equal, the first set conditions are changed, and lithium-ion batteries with equal comparative coulombic efficiencies are tested under the changed first set conditions. If the comparative coulombic efficiencies obtained from the coulombic efficiency test under the first changed first set conditions are different, all lithium-ion batteries are numbered in descending order of cycling performance. If at least two identical comparative coulombic efficiencies are still obtained when the coulombic efficiency test is performed under the first setting conditions after the first change, the first setting conditions are continued to be changed, and the lithium-ion batteries with the same comparative coulombic efficiency are tested under the changed first setting conditions, and this cycle is repeated until the comparative coulombic efficiencies obtained after the coulombic efficiency test is completed under the current first setting conditions are different. The method for evaluating the cycle performance of lithium-ion batteries provided in this embodiment, by changing the first setting conditions, ultimately makes the comparative coulombic efficiencies of any two lithium-ion batteries unequal, thereby distinguishing the advantages and disadvantages of the cycle performance between multiple lithium-ion batteries based on the comparative coulombic efficiencies. The method provided in this embodiment can use a charge and discharge tester with low test accuracy to test the comparative coulombic efficiency, without the need for a high-precision charge and discharge tester, thereby reducing testing costs.

[0041] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 11 is a flow chart of a method for evaluating the cycle performance of a lithium-ion battery provided in accordance with an embodiment of the present invention;

[0044] Figure 2 This is a test result curve graph obtained by pre-processing the lithium-ion battery;

[0045] Figure 3 Schematic diagram of the structure of a device for evaluating the cycle performance of a lithium-ion battery provided according to this embodiment. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0048] Figure 1 is a flow chart of a method for evaluating the cycle performance of a lithium-ion battery provided in accordance with an embodiment of the present invention, with reference to Figure 1 , the method provided in this embodiment includes the following steps:

[0049] S110 , pre-processing the plurality of lithium-ion batteries so that the discharge capacity of each lithium-ion battery after the pre-processing exceeds a set threshold.

[0050] Specifically, the multiple lithium-ion batteries provided in this embodiment can be of the same type or different types. Since lithium-ion batteries are not fully activated during initial use, their discharge capacity is unstable. Therefore, each lithium-ion battery needs to be pre-treated to activate it. Figure 2 This is a test result curve obtained by pre-processing lithium-ion batteries. Figure 2 During the pretreatment process, the discharge capacity of the lithium-ion battery will gradually increase, and the corresponding coulombic efficiency will also show an abnormal downward trend. When the discharge capacity of the lithium-ion battery exceeds the set threshold, the discharge capacity fluctuation of the lithium-ion battery is relatively small, that is, it reaches a stable state, and the corresponding coulombic efficiency is also relatively stable.

[0051] S120 , numbering each pre-treated lithium-ion battery and performing a coulombic efficiency test on each lithium-ion battery under a first set condition.

[0052] Specifically, each lithium-ion battery is numbered, and the corresponding lithium-ion battery can be identified based on the number. The coulombic efficiency test refers to charging the lithium-ion battery to a first set SOC and then discharging it to a second set SOC. The first set condition is to limit the lithium-ion battery to be charged to the first set SOC at a specific temperature and a specific current, and then discharged to the second set SOC at a specific current. The first set condition also includes the number of tests for the lithium-ion battery to be tested for coulombic efficiency.

[0053] S130: Determine the comparative coulombic efficiency of each lithium-ion battery that completes the coulombic efficiency test under the current first setting condition.

[0054] Specifically, each time a lithium-ion battery completes a coulombic efficiency test, a coulombic efficiency is obtained. If the lithium-ion battery is subjected to multiple coulombic efficiency tests, the comparative coulombic efficiency of the lithium-ion battery is determined based on the coulombic efficiencies obtained from the multiple coulombic efficiency tests.

[0055] S140 , determining whether at least two lithium-ion batteries have the same comparative coulombic efficiency based on the comparative coulombic efficiency of each lithium-ion battery.

[0056] Specifically, each lithium-ion battery has a comparative coulombic efficiency. If all comparative coulombic efficiencies are different, the cycling performance of these lithium-ion batteries can be directly analyzed based on these comparative coulombic efficiencies. If at least two lithium-ion batteries have the same comparative coulombic efficiency, the cycling performance of the lithium-ion batteries with the same comparative coulombic efficiency cannot be distinguished. Therefore, it is necessary to change the first set condition and then re-test the lithium-ion batteries with the same comparative coulombic efficiency, i.e., execute S150.

[0057] If yes, execute S150 ; if no, execute S160 .

[0058] S150 , changing the current first setting condition, performing a coulombic efficiency test on the lithium-ion batteries with the same coulombic efficiency under the changed first setting condition, and then returning to S130 .

[0059] Specifically, research has found that lithium-ion batteries have side reactions during the coulombic efficiency test. When the side reaction efficiency increases, the coulombic efficiency of the lithium-ion battery will decrease. When the ambient temperature of the coulombic efficiency test increases, the side reaction efficiency of the lithium-ion battery will increase. When the charge and discharge current of the coulombic efficiency test decreases, the side reaction efficiency of the lithium-ion battery will increase. Therefore, when the comparative coulombic efficiencies of at least two lithium-ion batteries are the same, the first setting condition is changed. By changing the first setting condition, the side reaction efficiency of the lithium-ion battery is changed. When the side reaction efficiencies of any two lithium-ion batteries are different, the comparative coulombic efficiencies of any two lithium-ion batteries will be different. By changing the first setting condition, the comparative coulombic efficiencies of at least two lithium-ion batteries obtained under the changed first setting condition are ultimately different.

[0060] If any two comparative coulombic efficiencies obtained after the first setting condition is changed and the coulombic efficiency test is performed under the changed first setting condition are different, S160 is executed. If at least two comparative coulombic efficiencies obtained after the first setting condition is changed and the coulombic efficiency test is performed under the changed first setting condition are the same, the first setting condition is continued to be changed until the comparative coulombic efficiencies of the lithium-ion batteries tested under the current first setting condition are completely different. For example, the number of lithium-ion batteries is set to five, and the five lithium-ion batteries are numbered a, b, c, d, and e respectively. Under the initial first setting conditions, the coulombic efficiency of the five lithium-ion batteries was tested, and the comparative coulombic efficiencies obtained were 99.9%, 99.8%, 99.9%, 99.9%, and 99.7%, respectively. It can be concluded that the cycle performance of the lithium-ion batteries numbered a, c, and d is better than that of the lithium-ion battery numbered b, and the cycle performance of the lithium-ion battery numbered b is better than that of the lithium-ion battery numbered e, but the cycle performance of the lithium-ion batteries numbered a, c, and d cannot be distinguished. Then, the first setting conditions are changed, and the lithium-ion batteries numbered a, c, and d are tested under the changed first setting conditions. The coulombic efficiency test is performed on the lithium-ion batteries of the embodiment, and the comparative coulombic efficiencies obtained are 99.8%, 99.8%, and 99.7%, respectively. It can be concluded that the cycling performance of the lithium-ion batteries numbered a and c is better than that of the lithium-ion battery numbered d. However, the cycling performance of the lithium-ion batteries numbered a and c cannot be distinguished. Then, the first setting condition is changed and the coulombic efficiency test is performed again under the changed first setting condition. The comparative coulombic efficiencies obtained are 99.7% and 99.6%, respectively. It can be concluded that the cycling performance of the lithium-ion battery numbered a is better than that of the lithium-ion battery numbered c. Finally, it can be concluded that the cycling performance of the five lithium-ion batteries is ranked from best to worst as follows: a, c, d, b, e. It can be seen that the method for evaluating the cycling performance of lithium-ion batteries provided in this embodiment can use an ordinary charge and discharge tester to distinguish the cycling performance of multiple lithium-ion batteries, without the need for a high-precision charge and discharge tester, thereby reducing testing costs.

[0061] S160: Output the serial numbers of the lithium-ion batteries in descending order of cycle performance.

[0062] Specifically, if the comparative coulombic efficiencies obtained under the current first set condition are completely different, the lithium-ion batteries are numbered in descending order of cycling performance. The user can understand the cycling performance of the lithium-ion batteries based on the order of the numbers. If any two comparative coulombic efficiencies obtained after at least one change in the first set condition are different, S160 is executed. When executing S160, the numbers of all lithium-ion batteries must be output, with each number having a corresponding position.

[0063] This embodiment provides a method for evaluating the cycling performance of lithium-ion batteries. The method includes: first, pre-treating a plurality of lithium-ion batteries. The pre-treating is performed to activate the lithium-ion batteries so that the discharge capacity of the lithium-ion batteries undergoing coulombic efficiency testing is in a stable state. The pre-treating is completed when the discharge capacity of the lithium-ion battery exceeds a set threshold. Next, a coulombic efficiency test is performed on each lithium-ion battery under first set conditions, and a comparative coulombic efficiency of each lithium-ion battery is determined. If the comparative coulombic efficiencies of any two lithium-ion batteries obtained from the coulombic efficiency test under the initial first set conditions are different, all lithium-ion batteries are directly numbered in descending order of cycling performance. If at least two of the comparative coulombic efficiencies obtained from the coulombic efficiency test under the initial first set conditions are equal, the first set conditions are changed, and lithium-ion batteries with equal comparative coulombic efficiencies are tested under the changed first set conditions. If the comparative coulombic efficiencies obtained from the coulombic efficiency test under the first changed first set conditions are different, all lithium-ion batteries are numbered in descending order of cycling performance. If at least two identical comparative coulombic efficiencies are still obtained when the coulombic efficiency test is performed under the first setting conditions after the first change, the first setting conditions are continued to be changed, and the lithium-ion batteries with the same comparative coulombic efficiency are tested under the changed first setting conditions, and this cycle is repeated until the comparative coulombic efficiencies obtained after the coulombic efficiency test is completed under the current first setting conditions are different. The method for evaluating the cycle performance of lithium-ion batteries provided in this embodiment, by changing the first setting conditions, ultimately makes the comparative coulombic efficiencies of any two lithium-ion batteries unequal, thereby distinguishing the advantages and disadvantages of the cycle performance between multiple lithium-ion batteries based on the comparative coulombic efficiencies. The method provided in this embodiment can use a charge and discharge tester with low test accuracy to test the comparative coulombic efficiency, without the need for a high-precision charge and discharge tester, thereby reducing testing costs.

[0064] Optionally, performing a coulombic efficiency test on each lithium-ion battery under a first set condition specifically includes: placing each lithium-ion battery in an environment of a first set temperature until the difference between the temperature of the lithium-ion battery and the first set temperature does not exceed a set threshold; charging the lithium-ion battery to a first set SOC with a first set current, and then discharging the lithium-ion battery to a second set SOC with the first set current, and cycling the battery a first set number of times.

[0065] Specifically, the difference between the temperature of the lithium-ion battery and the first set temperature does not exceed the set threshold. The temperature of the lithium-ion battery can be equal to the first set temperature, or the temperature of the lithium-ion battery can fluctuate around the first set temperature, but the range of the fluctuation does not exceed the set threshold. Cycling the first set number of times means charging the lithium-ion battery with a first set current to a first set SOC and then discharging it with the first set current to a second set SOC, and such charging and discharging cycles are repeated the first set number of times. For example, if the first set number of times is 10, then charging the lithium-ion battery with the first set current to a first set SOC and then discharging it with the first set current to a second set SOC are repeated 10 times.

[0066] Optionally, determining the comparative coulombic efficiency of each lithium-ion battery that completes the coulombic efficiency test under the current first set condition specifically includes: determining the comparative coulombic efficiency according to an average value of coulombic efficiencies obtained from the coulombic efficiency tests in a set order.

[0067] Specifically, the setting order represents the order in which the lithium-ion batteries are tested for coulombic efficiency under the first setting conditions. For example, if the first setting number is 6, each lithium-ion battery needs to undergo 6 coulombic efficiency tests. The order of the first coulombic efficiency test is 1, the order of the second coulombic efficiency test is 2, the order of the third coulombic efficiency test is 3... and the number of times the sixth coulombic efficiency test is performed is 6. The setting order of this embodiment can be multiple. For example, the setting order can be 4, 5, and 6. The comparative coulombic efficiency is determined based on the average of the coulombic efficiencies obtained after the fourth, fifth, and sixth coulombic efficiency tests.

[0068] Optionally, the first set temperature includes 20-55°C; the first set number of times includes 5-20 times; and the first set current includes 0.01C-0.1C.

[0069] Specifically, the first set temperature in the changed first set condition still includes 20-55° C., the first set number of times still includes 5-20 times, and the first set current still includes 0.01-0.1C.

[0070] Setting the first set temperature between 20 and 55°C and the first set current between 0.01 and 0.1C can shorten the time it takes for the lithium-ion battery to charge to the first set SOC and shorten the time it takes for the lithium-ion battery to discharge to the second set SOC. In addition, when the first set temperature changes within the range of 20 to 55°C, the corresponding comparative coulombic efficiency of the lithium-ion battery will change, and different comparative coulombic efficiencies can be obtained by testing with a common charge and discharge tester. Similarly, when the first set number of times changes within the range of 5-20 times or the first set current changes within the range of 0.01C to 0.1C, different comparative coulombic efficiencies can be obtained by testing with a common charge and discharge tester.

[0071] Optionally, changing the current first setting condition specifically includes: changing the first setting temperature and / or the first setting current and the first setting number of times.

[0072] Specifically, the first set number of times is related to the first set temperature and the first set current. When the first set temperature and / or the first set current change, the first set number of times will change. The first set temperature and the first set current will both affect the side reaction efficiency of the lithium-ion battery. When the first set temperature and / or the first set current change, the side reaction efficiency will change, which will ultimately cause the comparative coulombic efficiency to change. By changing the first set condition, the comparative coulombic efficiency is changed. When the side reaction efficiencies of the lithium-ion batteries are different, the comparative coulombic efficiencies will be different. When ordinary charge and discharge testers display different comparative coulombic efficiencies, the cycling performance of the lithium-ion batteries can be distinguished.

[0073] Optionally, the first set SOC includes 100%; the second set SOC includes 0%.

[0074] Specifically, the first set SOC is set to 100% and the second set SOC is set to 0%, so that the coulombic efficiency obtained after each coulombic efficiency test can accurately reflect the cycle performance of the lithium-ion battery.

[0075] Optionally, pre-processing the plurality of lithium-ion batteries specifically includes: performing a second set number of standard charges and discharges on each lithium-ion battery at a second set temperature.

[0076] Optionally, performing standard charge and discharge for each lithium-ion battery for a second set number of times specifically includes: charging the lithium-ion battery with the charging current specified by the supplier of the lithium-ion battery to the charging voltage specified by the supplier, and then discharging the lithium-ion battery with the discharge current specified by the supplier to the discharge voltage specified by the supplier, and repeating the cycle for the second set number of times.

[0077] Specifically, after the lithium-ion battery is charged to the charging voltage specified by the supplier, the lithium-ion battery can be left to stand for a period of time, and then discharged to the discharge voltage specified by the supplier using the discharge current specified by the supplier.

[0078] Optionally, the second set temperature includes 20=45° C.; the second set number includes 10=20 times.

[0079] Specifically, setting the second set temperature within the range of 20-45°C can shorten the time it takes for the lithium-ion battery's discharge capacity to increase, shorten the test time, and improve test efficiency. Setting the second set number of times to 10-20 times can complete the activation of the lithium-ion battery and ultimately achieve a stable discharge capacity of the lithium-ion battery.

[0080] Figure 3 This is a schematic diagram of the structure of a device for evaluating the cycle performance of a lithium-ion battery provided in this embodiment, with reference to Figure 3 The device provided in this embodiment includes: a pre-processing module 210, a testing module 220, a comparative coulombic efficiency determination module 230, a comparison module 240, a test condition change module 250 and an output module 260; the pre-processing module 210 is used to pre-process a plurality of lithium-ion batteries so that the discharge capacity of each lithium-ion battery after pre-processing exceeds a set threshold; the testing module 220 is used to number each lithium-ion battery after pre-processing and perform a coulombic efficiency test on each lithium-ion battery under a first set condition; the comparative coulombic efficiency determination module 230 is used to determine whether the coulombic efficiency test is completed under the current first set condition. The comparison module 240 is used to determine whether at least two lithium-ion batteries have the same comparative coulombic efficiency based on the comparative coulombic efficiency of each lithium-ion battery; the test condition changing module 250 is used to change the current first setting condition when the comparative coulombic efficiencies of at least two lithium-ion batteries are the same, and the test module 220 is further used to perform a coulombic efficiency test on the lithium-ion batteries with the same comparative coulombic efficiency under the changed first setting condition; the output module 260 is used to output the numbers of the lithium-ion batteries in descending order according to the cycling performance when the comparative coulombic efficiencies of any two lithium-ion batteries are different.

[0081] Specifically, the preprocessing module 210 is connected to the testing module 220, the testing module 220 is connected to the comparative coulombic efficiency determination module 230, the comparative coulombic efficiency determination module 230 is connected to the comparison module 240, the comparison module 240 is connected to the test condition changing module 250 and the output module 260, and the test condition changing module 250 is connected to the testing module 220.

[0082] The device for evaluating the cycle performance of a lithium-ion battery provided in an embodiment of the present invention has corresponding beneficial effects as the method for evaluating the cycle performance of a lithium-ion battery provided in any embodiment of the present invention. The technical details not detailed in this embodiment are detailed in the method for evaluating the cycle performance of a lithium-ion battery provided in any embodiment of the present invention.

[0083] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0084] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for evaluating the cycle performance of a lithium-ion battery, characterized in that: The steps include: S110, pre-processing the plurality of lithium-ion batteries so that the discharge capacity of each of the lithium-ion batteries after pre-processing exceeds a set threshold; S120, numbering each of the pre-treated lithium-ion batteries and performing a coulombic efficiency test on each of the lithium-ion batteries under the first set conditions; S130, determining the comparative coulombic efficiency of each of the lithium-ion batteries that completes the coulombic efficiency test under the current first set conditions; S140, determining whether at least two of the lithium-ion batteries have the same comparative coulombic efficiency based on the comparative coulombic efficiency of each of the lithium-ion batteries; If yes, execute S150; if no, execute S160; S150, changing the current first setting condition, performing the coulombic efficiency test on the lithium-ion batteries with the same compared coulombic efficiency under the changed first setting condition, and then returning to S130; S160, outputting serial numbers of the lithium-ion batteries in descending order of cycle performance; The coulombic efficiency test of each lithium-ion battery under the first set condition specifically includes: placing each of the lithium-ion batteries in an environment with a first set temperature until the difference between the temperature of the lithium-ion battery and the first set temperature does not exceed a set threshold; The lithium-ion battery is charged to a first set SOC with a first set current, and then discharged to a second set SOC with the first set current, and the cycle is repeated for a first set number of times.

2. The method according to claim 1, characterized in that Determining the comparative coulombic efficiency of each of the lithium-ion batteries that complete the coulombic efficiency test under the current first set conditions specifically includes: The comparative coulombic efficiency is determined according to an average value of the coulombic efficiencies obtained from the coulombic efficiency tests in a set order.

3. The method according to claim 1, characterized in that The first set temperature includes 20-55°C; The first set number of times includes 5-20 times; The first set current includes 0.01C-0.1C.

4. The method according to claim 1, wherein The changing of the current first setting condition specifically includes: The first set temperature and / or the first set current and the first set number of times are changed.

5. The method according to claim 1, wherein The first set SOC includes 100%; The second set SOC includes 0%.

6. The method according to claim 1, characterized in that The pre-processing of the plurality of lithium-ion batteries specifically includes: At a second set temperature, each of the lithium-ion batteries is subjected to a second set number of standard charges and discharges.

7. The method according to claim 6, characterized in that The second set temperature includes 20-45°C; The second set number of times includes 10-20 times.

8. The method according to claim 6, characterized in that The performing of a second set number of standard charge and discharge on each of the lithium-ion batteries specifically includes: The lithium-ion battery is charged to a charging voltage specified by the supplier using a charging current specified by the supplier, and then discharged to a discharge voltage specified by the supplier using a discharging current specified by the supplier, and the cycle is repeated for a second set number of times.

9. A device for evaluating the cycle performance of a lithium-ion battery, characterized in that: include: A preprocessing module, a testing module, a comparative coulombic efficiency determination module, a comparison module, a testing condition changing module, and an output module; The pre-processing module is used to pre-process the plurality of lithium-ion batteries so that the discharge capacity of each lithium-ion battery after pre-processing exceeds a set threshold; The testing module is used to number each of the pre-treated lithium-ion batteries and perform a coulombic efficiency test on each of the lithium-ion batteries under a first set condition; The comparative coulombic efficiency determination module is used to determine the comparative coulombic efficiency of each of the lithium-ion batteries that completes the coulombic efficiency test under the current first setting conditions; The comparison module is configured to determine, based on the comparative coulombic efficiency of each of the lithium-ion batteries, whether at least two of the lithium-ion batteries have the same comparative coulombic efficiency; The test condition changing module is used to change the current first set condition when the comparative coulombic efficiencies of at least two lithium-ion batteries are the same; The testing module is further configured to perform a coulombic efficiency test on the lithium-ion batteries having the same comparative coulombic efficiency under the changed first setting conditions; The output module is used to output the serial numbers of the lithium-ion batteries in descending order of cycle performance when the comparative coulombic efficiencies of any two lithium-ion batteries are different; The coulombic efficiency test of each lithium-ion battery under the first set condition specifically includes: placing each of the lithium-ion batteries in an environment with a first set temperature until the difference between the temperature of the lithium-ion battery and the first set temperature does not exceed a set threshold; The lithium-ion battery is charged to a first set SOC with a first set current, and then discharged to a second set SOC with the first set current, and the cycle is repeated for a first set number of times.

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