A screening and evaluation method for cascade utilization of retired power monomer batteries

Abstract

The application discloses a kind of retired power monomer battery echelon utilization screening evaluation methods.Therein, the method includes: a plurality of initial batteries are charged to first state of charge, obtain a plurality of target batteries and with a plurality of target batteries respectively corresponding charge quantity;A plurality of target batteries are carried out predetermined activation operation, obtain a plurality of activation batteries;A plurality of activation batteries are discharged to second state of charge, obtain and with a plurality of activation batteries respectively corresponding discharge quantity and second polarization voltage;Based on the above charge quantity and discharge quantity, determine and with a plurality of target batteries respectively corresponding self-discharge rate;Determine the first polarization voltage corresponding to a plurality of activation batteries after charging from second state of charge to first state of charge;Based on the above charge quantity, self-discharge rate, first polarization voltage and second polarization voltage, determine the state parameter corresponding to a plurality of activation batteries respectively;Based on the state parameter corresponding to a plurality of activation batteries respectively, determine the state grade of a plurality of activation batteries.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and more specifically, to a screening and evaluation method for the cascade utilization of retired power cell batteries. Background Technology

[0002] In related technologies, the current state of a battery is mostly determined by measuring parameters such as open-circuit voltage, internal resistance, remaining capacity through charge-discharge cycles, battery temperature during charge-discharge, pulse charge-discharge voltage and internal resistance changes, and charging impedance. However, using the above methods to screen and evaluate the state of batteries for cascade utilization has problems such as long execution time, low efficiency, inaccurate battery impedance characterization, high testing costs due to the large number of testing devices involved, or high method complexity.

[0003] Therefore, the relevant technologies suffer from high costs, low efficiency, and poor results when selecting batteries for secondary use by screening battery conditions.

[0004] There is currently no effective solution to the above problems. Summary of the Invention

[0005] This invention provides a screening and evaluation method for the cascade utilization of retired power cell batteries, which at least solves the technical problems of high cost, low efficiency, and poor effect when determining batteries for cascade utilization by screening battery conditions.

[0006] According to one aspect of the present invention, a method for screening and evaluating the cascade utilization of retired power cell batteries is provided, comprising: charging a plurality of initial batteries to a first state of charge to obtain a plurality of target batteries and a charge amount corresponding to each of the target batteries; performing a predetermined activation operation on the plurality of target batteries to obtain a plurality of activated batteries; discharging the plurality of activated batteries to a second state of charge to obtain a discharge amount corresponding to each of the activated batteries and a second polarization voltage corresponding to each of the activated batteries when discharged to the second state of charge; determining a self-discharge rate corresponding to each of the target batteries based on the charge amount corresponding to each of the target batteries and the discharge amount corresponding to each of the activated batteries; charging the plurality of activated batteries from the second state of charge to the first state of charge to obtain a first polarization voltage corresponding to each of the activated batteries; determining state parameters corresponding to each of the activated batteries based on the charge amount and self-discharge rate corresponding to each of the target batteries, and the first and second polarization voltages corresponding to each of the activated batteries; and determining a state level corresponding to each of the activated batteries based on the state parameters corresponding to each of the activated batteries.

[0007] Optionally, before charging multiple initial batteries to a first state of charge and obtaining multiple target currents and corresponding charge amounts for each target battery, the method further includes: performing a first charge and a first discharge on the multiple initial batteries according to a predetermined current and a predetermined voltage.

[0008] Optionally, before charging multiple initial batteries to a first state of charge to obtain multiple target batteries and their respective charging amounts, the method further includes: determining multiple batteries to be evaluated; screening multiple batteries according to predetermined conditions, determining batteries that meet the predetermined conditions as initial batteries, and obtaining multiple initial batteries, wherein the predetermined rules are: the degree of no damage or deformation to the battery appearance is within a predetermined allowable range, and the open circuit voltage of the battery is higher than a predetermined value.

[0009] Optionally, a predetermined activation operation is performed on multiple target batteries to obtain multiple activated batteries, including: placing multiple target batteries in a predetermined temperature range for a predetermined time to obtain multiple activated batteries.

[0010] Optionally, the preset temperature range is 30℃~70℃, and the preset duration is 4h~158h.

[0011] Optionally, the self-discharge rate of each of the multiple target batteries can be determined as follows:

[0012] S = (C1 - C2) / C1 * 100%

[0013] Where S is the self-discharge rate, C1 is the charge amount corresponding to each of the multiple target batteries, and C2 is the discharge amount corresponding to each of the multiple activated batteries.

[0014] Optionally, the state parameters corresponding to multiple activated cells can be determined as follows:

[0015] F(SOH)=f1*C+f2*(U 上 -U 下 ) / (ΔU1+ΔU2)+f3*1 / S

[0016] Where F(SOH) is the state parameter, f1, f2, and f3 are predetermined weighting factors, C is the charging capacity of the multiple activated cells when they are charged from the second state of charge to the first state of charge, and U 上 U represents the upper limit voltage corresponding to each of the multiple activated cells. 下 ΔU1 represents the lower limit voltage corresponding to each of the multiple activated batteries, ΔU2 represents the multiple second polarization voltages corresponding to each of the multiple activated batteries when they reach the second state of charge during discharge, and S represents the self-discharge rate corresponding to each of the multiple target batteries when they are charged from the second state of charge to the first state of charge.

[0017] Optionally, based on the state parameters corresponding to the multiple activated cells, the state levels corresponding to the multiple activated cells are determined, including: sorting the state parameters corresponding to the multiple activated cells according to their numerical values; determining multiple target state parameters based on the sorting results and a predetermined arrangement order range; obtaining target state evaluation parameters based on the multiple target state parameters; determining the range of state evaluation parameters corresponding to the multiple state levels based on the target state evaluation parameters and a predetermined state level weighting factor; and determining the state levels corresponding to the multiple activated cells based on the range of state evaluation parameters and the state parameters corresponding to the multiple target cells.

[0018] Optionally, the above method further includes: utilizing multiple activated batteries in stages based on the state levels corresponding to the multiple activated batteries respectively.

[0019] In this embodiment of the invention, the state parameters of the battery are calculated. Multiple initially screened batteries are subjected to a predetermined charge-discharge-recharge cycle to a first state of charge to obtain multiple target batteries and their charge amounts. Then, the multiple target batteries are placed at a preset temperature for a preset time to activate them, resulting in activated target batteries. The activated target batteries are then discharged to a second state of charge using a preset current to obtain their discharge amounts. Based on the charge amounts and discharge amounts of the activated target batteries, the self-discharge rate of each target battery is calculated. The second polarization voltage when the multiple target batteries reach the second state of charge and the first polarization voltage when they reach the first state of charge are measured and calculated. Based on the discharge amount, self-discharge rate, first polarization voltage, and second polarization voltage, the state parameters of each target battery are determined. These state parameters characterize the battery's health status. Therefore, the state level of each target battery can be determined based on these state parameters. Furthermore, this embodiment includes an activation operation under preset conditions during the battery state evaluation process. The activation operation can improve the health status of the evaluated battery. Therefore, more of the evaluated batteries can be repaired to a certain extent through activation, and can eventually pass the state assessment screening, so as to maximize their value in the cascade utilization stage. In addition, the equipment involved in the implementation of this embodiment is conventional charging and discharging equipment and voltmeter, thereby achieving the technical effect of determining the battery state assessment at low cost and high efficiency. This solves the technical problems of high cost, low efficiency and poor effect when determining batteries for cascade utilization by screening battery state. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0021] Figure 1 This is a flowchart of a screening and evaluation method for the cascade utilization of retired power cell batteries according to an embodiment of the present invention;

[0022] Figure 2 This is a flowchart of a screening and evaluation method for the cascade utilization of retired power cell batteries provided by an optional embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the test results of Example 1 provided by an optional embodiment of the present invention. Figure 1 ;

[0024] Figure 4 This is a schematic diagram of the test results of Example 1 provided by an optional embodiment of the present invention. Figure 2 ;

[0025] Figure 5 This is a schematic diagram of the test results of Example 2 provided by an optional embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of the test results of Example 3 provided according to an optional embodiment of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] Terminology Explanation

[0030] Retired power battery cells: refers to battery cells obtained from the modules of retired power battery packs.

[0031] Secondary use: This refers to the use of batteries that can no longer meet the requirements of the original design application scenarios after they have been retired, and then reused in scenarios with lower requirements.

[0032] State of charge (SOC): A relative measure of the energy stored in a battery, defined as the ratio of the amount of charge that can be extracted from the cell at a specific point in time to the total capacity.

[0033] According to an embodiment of the present invention, a screening and evaluation method for the cascade utilization of retired power cell batteries is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings may include, for example, ending the shelving, constant current discharge to the lower limit voltage, recording the discharge capacity C2, and calculating the self-discharge rate. Although the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than that shown here.

[0034] Figure 1 This is a flowchart of a screening and evaluation method for the cascade utilization of retired power cell batteries according to an embodiment of the present invention, such as... Figure 1 As shown, the method includes the following steps:

[0035] Step S102: Charge multiple initial batteries to the first state of charge to obtain multiple target batteries and the charging amount corresponding to each of the multiple target batteries;

[0036] Step S104: Perform a predetermined activation operation on multiple target batteries to obtain multiple activated batteries;

[0037] Step S106: Discharge multiple activated batteries to the second state of charge to obtain the discharge amount corresponding to each of the multiple activated batteries, and the second polarization voltage corresponding to each of the multiple activated batteries when they are discharged to the second state of charge.

[0038] Step S108: Based on the charging amount corresponding to the multiple target batteries and the discharging amount corresponding to the multiple activated batteries, determine the self-discharge rate corresponding to the multiple target batteries respectively.

[0039] Step S110: Charge multiple activated cells from the second state of charge to the first state of charge to obtain the first polarization voltage corresponding to each of the multiple activated cells.

[0040] Step S112: Based on the charge amount and self-discharge rate of the multiple target batteries, and the first polarization voltage and second polarization voltage of the multiple activated batteries, determine the state parameters of the multiple activated batteries.

[0041] Step S114: Based on the state parameters corresponding to the multiple activated cells, determine the state level corresponding to each of the multiple activated cells.

[0042] Through the above steps, by calculating the battery's state parameters, multiple initially screened batteries are subjected to a predetermined charge-discharge-recharge cycle to reach a first state of charge, resulting in multiple target batteries and their charge amounts. Next, the target batteries are activated by resting at a preset temperature for a preset time, resulting in activated target batteries. The activated target batteries are then discharged to a second state of charge using a preset current, yielding their discharge amounts. Based on the charge amounts and discharge amounts of the activated target batteries, the self-discharge rate of each target battery is calculated. The second polarization voltage when the target batteries reach the second state of charge and the first polarization voltage when they reach the first state of charge are measured and calculated. Based on the discharge amount, self-discharge rate, first polarization voltage, and second polarization voltage, the state parameters of each target battery are determined. These state parameters characterize the battery's health status. Therefore, the state level of each target battery can be determined based on these state parameters. Furthermore, this embodiment includes an activation operation under preset conditions during the battery state evaluation process, which improves the health status of the evaluated battery. Therefore, more of the evaluated batteries can be repaired to a certain extent through activation, and can eventually pass the state assessment screening, so as to maximize their value in the cascade utilization stage. In addition, the equipment involved in the implementation of this embodiment is conventional charging and discharging equipment and voltmeter, thereby achieving the technical effect of determining the battery state assessment at low cost and high efficiency. This solves the technical problems of high cost, low efficiency and poor effect when determining batteries for cascade utilization by screening battery state.

[0043] It should be noted that the second state of charge mentioned above can be the state where the battery is discharged to the lower limit voltage (0% SOC), while the first state of charge can be the state where the battery is charged to the upper limit voltage and fully charged at the upper limit voltage (100% SOC). Correspondingly, the second polarization voltage can be ΔU1 = U1 - U 下 The first polarization voltage can be ΔU2 = U 上 -U2, where U 上 U represents the upper limit voltage corresponding to multiple target batteries. 下 ΔU1 represents the lower limit voltage corresponding to each of the multiple target batteries, ΔU2 represents the multiple second polarization voltages corresponding to each of the multiple target batteries when they reach the second state of charge during discharge, ΔU2 represents the first polarization voltages corresponding to each of the multiple target batteries when they are charged from the second state of charge to the first state of charge, U1 represents the open circuit voltage of the battery in the second state of charge, and U2 represents the open circuit voltage of the battery in the first state of charge.

[0044] As an optional embodiment, before charging multiple initial batteries to a first state of charge to obtain multiple target batteries and their corresponding charge amounts, the method further includes: performing a first charge and a first discharge on the multiple initial batteries according to a predetermined current and a predetermined voltage. During battery discharge, the stored electrical energy is gradually released, and the voltage slowly decreases. When the voltage drops to a certain predetermined value, discharge should be stopped, and the battery should be recharged to restore its energy storage state. Continuing to discharge below this predetermined value constitutes over-discharge, which may damage the active materials of the electrodes, causing them to lose their reactivity and shortening the battery's lifespan. In this embodiment, after identifying the initial batteries, they are first charged once, followed by subsequent discharge-charge, high-temperature activation, and other operations. For example, the initial batteries can be charged to full capacity using a constant current and voltage according to a predetermined current and voltage, then discharged and recharged, followed by high-temperature activation. Through these operations, the adverse effects of potential over-discharge during battery storage can be effectively avoided, ensuring that these initial batteries can recover to a better health state, pass state assessment, and meet the state level requirements for battery cascade utilization.

[0045] As an optional embodiment, before performing the first charge on each of the multiple initial batteries according to a predetermined current and a predetermined voltage, the method further includes: identifying multiple batteries to be evaluated; screening the multiple batteries according to predetermined conditions, and determining the batteries that meet the predetermined conditions as initial batteries, thereby obtaining multiple initial batteries. The predetermined rules are: the degree of damage or deformation to the battery's appearance is within a predetermined allowable range, and the battery's open-circuit voltage is higher than a predetermined value. For the batteries to be evaluated, a preliminary screening can be performed first to remove batteries that can be directly judged as unusable for cascade utilization without requiring multiple measurements or other testing operations. For example, batteries with damaged or severely deformed appearances and open-circuit voltages lower than a predetermined voltage value (e.g., 0.5V) can be directly rejected; these batteries can be used for recycling.

[0046] As an optional embodiment, a predetermined activation operation is performed on multiple target batteries to obtain multiple activated batteries, including: placing multiple target batteries in a predetermined temperature range for a predetermined time to obtain multiple activated batteries.

[0047] As an optional embodiment, the predetermined temperature range can be 30℃ to 70℃, and the predetermined duration can be 4h to 158h. Preferably, the predetermined temperature range can be specifically set to 45℃ to 60℃, and the predetermined duration can be specifically set to 12h to 72h.

[0048] To avoid overlooking batteries that can be reused after activation, and to ensure that more batteries pass the state assessment and meet the state level requirements for battery reuse, this embodiment activates the target battery during the predetermined charge-discharge operation of the initial battery, enabling more batteries to meet the quality requirements for reuse. For example, the battery can be placed in a temperature range of 45℃-60℃, i.e., a high-temperature placement method can be used to activate the battery. Through high-temperature placement, some deposited lithium can be activated, reducing the battery's internal resistance, increasing and stabilizing the battery capacity, and reducing the self-discharge rate in the future reuse stage.

[0049] As an optional embodiment, the self-discharge rate of the multiple target batteries is determined as follows:

[0050] S = (C1 - C2) / C1 * 100%

[0051] Where S is the self-discharge rate, C1 is the charge amount corresponding to each of the multiple target batteries, and C2 is the discharge amount corresponding to each of the multiple activated batteries.

[0052] It should be noted that in this embodiment, after recording the initial battery charge, the target battery is obtained and subjected to high-temperature storage. The purpose of high-temperature storage is to activate the battery. During the high-temperature storage process, the battery will self-discharge, and the self-discharge situation can be observed simultaneously. Therefore, after the high-temperature storage activation is completed, the target battery needs to be discharged again based on the self-discharge during the storage period until the target battery's lower limit voltage (i.e., the second state of charge) is reached. The discharge amount at this time is then recorded, and based on this discharge amount and the aforementioned charge amount, the self-discharge rate of the target battery is calculated using the above formula.

[0053] As an optional embodiment, the state parameters corresponding to the multiple target batteries are determined as follows:

[0054] F(SOH)=f1*C+f2*(U 上 -U 下 ) / (ΔU1+ΔU2)+f3*1 / S

[0055] Where F(SOH) is the state parameter, f1, f2, and f3 are predetermined weighting factors, C is the charging capacity of the multiple activated cells when they are charged from the second state of charge to the first state of charge, and U 上 U represents the upper limit voltage corresponding to each of the multiple activated cells. 下 ΔU1 represents the lower limit voltage corresponding to each of the multiple activated batteries, ΔU2 represents the multiple second polarization voltages corresponding to each of the multiple activated batteries when they reach the second state of charge during discharge, and S represents the self-discharge rate corresponding to each of the multiple target batteries when they are charged from the second state of charge to the first state of charge.

[0056] In the above formula, f1, f2, and f3 are used as predetermined weight factors, and a certain relationship can be set among the three of them, and the specific values can be adjusted according to actual application needs. For example, it can be set that f1 + f2 + f3 = 10, where 1 < f1 ≤ 3, 4 < f2 ≤ 7, 1.5 < f3 ≤ 4, and so on.

[0057] It should be noted that in order to improve the efficiency of determining the state parameters of each target battery, a battery state evaluation model can be constructed based on the above formula. By inputting the discharge capacity, self-discharge rate, first polarization voltage, and second polarization voltage of the battery into this model, the corresponding state parameters of the battery can be obtained quickly and accurately.

[0058] It should be noted that in order to ensure the accuracy of the battery state level, the number of batteries for state evaluation in the same batch can be restricted. For example, the number of batteries for test evaluation in each batch can be restricted to more than 50, and so on.

[0059] As an optional embodiment, based on the state parameters respectively corresponding to multiple activated batteries, determining the state levels respectively corresponding to the multiple activated batteries includes: sorting the state parameters respectively corresponding to the multiple activated batteries according to the numerical size; determining multiple target state parameters based on the sorting result and a predetermined arrangement order range; obtaining a target state evaluation parameter based on the multiple target state parameters; determining a state evaluation parameter range respectively corresponding to multiple state levels based on the target state evaluation parameter and a predetermined state level weight factor; and determining the state levels respectively corresponding to the multiple activated batteries based on the state evaluation parameter range and the state parameters respectively corresponding to the multiple target batteries.

[0060] After determining the state parameters of all activated batteries, these state parameters can be sorted, and a target state evaluation parameter can be determined according to the sorting result. For example, if the number of activated batteries is 50, the state parameters corresponding to these 50 activated batteries can be sorted according to the numerical size, and the average value of the state parameters of the 11th to 40th activated batteries in the sorted state parameters can be calculated, and this calculated average value can be used as the target state evaluation parameter.

[0061] After determining the target state evaluation parameter, the state level of the battery can be divided according to this target state evaluation parameter. For example, assuming the target state evaluation parameter is x, it can be set that those with F(SOH) > x are classified as level 1, those with 0.8x < F(SOH) ≤ x are classified as level 2, those with 0.5x < F(SOH) ≤ 0.8x are classified as level 3, and those with F(SOH) ≤ 0.5x are classified as level 4, and so on.

[0062] As an optional embodiment, the above method further includes: utilizing the multiple activated batteries in a tiered manner based on their respective state levels. After determining the state levels of the multiple activated batteries, they can be graded and sorted. For target batteries classified into different levels, they can be used in tiered applications for different scenarios to maximize the value of the battery tiered utilization stage.

[0063] It should be noted that the batteries to be evaluated mentioned above can be retired power cell cells.

[0064] Based on the above embodiments and optional embodiments, the present invention proposes an optional implementation method, which will be described below.

[0065] An optional embodiment of the present invention provides a screening and evaluation method for the cascade utilization of retired power cell batteries. Figure 2 This is a flowchart of a screening and evaluation method for the cascade utilization of retired power cell batteries provided by an optional embodiment of the present invention, such as... Figure 2 As shown, the steps of this method are as follows:

[0066] S1. Conduct a preliminary screening of a batch of single-cell batteries of the same model, and remove batteries with damaged appearance or severe deformation and open circuit voltage below 0.5V. The removed batteries are discarded and recycled.

[0067] S2. First, charge the battery to full capacity using constant current and constant voltage. Then, perform one discharge and one charge. Record the capacity C1 of the second charge.

[0068] S3. Activate the battery by placing it at a high temperature of 45℃-60℃ for 1-3 days, and observe its self-discharge at the same time.

[0069] S4. After the resting period ends, discharge to the lower limit voltage U. 下 (0% SOC), record the discharge capacity C2, and calculate the self-discharge rate S: S=(C1-C2) / C1*100%.

[0070] S5. Detect the open-circuit voltage U1 of the battery at 0% SOC and obtain the polarization voltage ΔU1 = U1 - U 下 ;

[0071] S6. Next, charge to the first state of charge (100% SOC), record the charging capacity C, and use this charging capacity as the remaining capacity of the battery; check the open-circuit voltage U2 of the battery at 100% SOC; polarization voltage ΔU2 = U 上 -U2.

[0072] S7. Battery Health Status Assessment: Randomly select more than 50 individual batteries for testing, and substitute the measured parameters into the battery health status assessment model:

[0073] F(SOH) = f1 * C + f2 * (U 上 - U 下 ) / (ΔU1 + ΔU2) + f3 * 1 / S "

[0074] Where, f1, f2, and f3 are weighting factors, f1 + f2 + f3 = 10, 1 < f1 ≤ 3, 4 < f2 ≤ 7, 1.5 < f3 ≤ 4;

[0075] F(SOH) is sorted by value, and the average value x of the 11th to 40th (a total of 30) F(SOH) is taken as the health factor benchmark number.

[0076] S8. Classification of the battery under test: Set a threshold according to the health factor F(SOH) benchmark number. Batteries with F(SOH) > x are classified as level 1, 0.8x < F(SOH) ≤ x are classified as level 2, 0.5x < F(SOH) ≤ 0.8x are classified as level 3, and F(SOH) ≤ 0.5x are classified as level 4 and directly eliminated.

[0077] The specific application of this method is introduced below.

[0078] 1. Example 1

[0079] S11. Take 90 ternary monomer batteries of the same model, eliminate batteries with damaged appearance, severe deformation, and open - circuit voltage lower than 0.5V, and select 64 batteries for evaluation (ensure that the remaining batteries under test ≧ 50). The eliminated batteries are collected for recycling;

[0080] S12. First, charge at a constant current of 0.5C to the upper - limit voltage of 4.2V, then charge at a constant voltage of 4.2V until the cut - off current of 0.05C, set aside for 2 minutes, then discharge at a constant current of 0.5C to 1.0V, set aside for 2 minutes, charge at a constant current of 0.5C to the upper - limit voltage of 4.2V, and charge at a constant voltage of 4.2V until the cut - off current of 0.05C, and record the second charging capacity C1;

[0081] S13. Set aside at 45°C for 2 days (48 hours);

[0082] S14. After the high - temperature setting - aside ends, discharge at a constant current of 0.5C to the lower - limit voltage of 1.0V (0% SOC), record the discharge capacity C2, and calculate the self - discharge rate S: S = (C's1 - C2) / C1 * 100%.

[0083] S15. Detect the open - circuit voltage U1 of the battery at 0% SOC; obtain the polarization voltage ΔU1 = U1 - U 下 ;

[0084] S16. Next, charge at a constant current of 0.5C until the upper limit voltage of 4.2V is reached, then charge at a constant voltage of 4.2V until the cut-off current of 0.05C is reached, record the charging capacity C, and use the charging capacity in this step as the remaining capacity of the battery; detect the open circuit voltage U2 of the battery at the 100% SOC state at this time, and calculate the polarization voltage ΔU2 = U 上 - U2;

[0085] S17. Substitute the above measured parameters into the calculation formula of the battery health state evaluation model:

[0086] F(SOH) = f1 * C + f2 * (U 上 - U 下 ) / (ΔU1 + ΔU2) + f3 * 1 / S

[0087] Among them, f1, f2, and f3 are weighting factors, f1 + f2 + f3 = 10, 1 < f1 ≤ 3, 4 < f2 ≤ 7, 1.5 < f3 ≤ 4; in this example, f1 = 2, f2 = 5, f3 = 3. The obtained parameters are shown in Table 1.

[0088] Table 1

[0089]

[0090]

[0091]

[0092] Sort F(SOH) by value, and take the average value x of the 11th to 40th (a total of 30) F(SOH) as the health factor reference number.

[0093] S18. Classify the battery to be tested: Set a threshold according to the health factor F(SOH) reference number. Batteries with F(SOH) > x are classified as level 1, 0.8x < F(SOH) ≤ x are classified as level 2, 0.5x < F(SOH) ≤ 0.8x are classified as level 3, and F(SOH) ≤ 0.5x are classified as level 4 and directly eliminated. Figure 3 It is a schematic diagram of the test results of Example 1 provided according to an optional embodiment of the present invention Figure 1 , Figure 4 It is a schematic diagram of the test results of Example 1 provided according to an optional embodiment of the present invention Figure 2 .

[0094] 2. Example 2

[0095] S21. Take 90 ternary monomer batteries of the same model in a batch, eliminate the batteries with damaged appearance, serious deformation, and open circuit voltage lower than 0.5V, and the remaining 70 batteries to be tested. The eliminated batteries are collected for recycling;

[0096] S22: First, charge at a constant current of 0.5C until the upper limit voltage of 4.2V is reached, then charge at a constant voltage of 4.2V until the cut-off current of 0.05C is reached, hold for 2 minutes. Then, discharge at a constant current of 0.5C to 1.0V, hold for 2 minutes, charge at a constant current of 0.5C until the upper limit voltage of 4.2V is reached, and charge at a constant voltage of 4.2V until the cut-off current of 0.05C is reached, and record the second charging capacity C1;

[0097] S23: Hold at 45°C for 2 days (48 hours);

[0098] S24: After the high-temperature holding ends, discharge at a constant current of 0.5C to the lower limit voltage of 1.0V (0% SOC), record the discharge capacity C2, and calculate the self-discharge rate S: S = (C1 - C2) / C1 * 100%;

[0099] S25: Detect the open-circuit voltage U1 of the battery at the 0% SOC state; obtain the polarization voltage ΔU1 = U1 - U 下 。

[0100] S26: Then, charge at a constant current of 0.5C until the upper limit voltage of 4.2V is reached, charge at a constant voltage of 4.2V until the cut-off current of 0.05C is reached, record the charging capacity C, and use the charging capacity in this step as the remaining capacity of the battery; detect the open-circuit voltage U2 of the battery at the 100% SOC state at this time; polarization voltage ΔU2 = U 上 - U2;

[0101] S27: Substitute the above measured parameters into the calculation formula of the battery health state evaluation model:<​​​​​​​​​​​​​​​​​​​​​​S28. Battery grading for testing: Set thresholds according to the reference value of the health factor F(SOH). Batteries with F(SOH) > x are classified as level 1, those with 0.8x < F(SOH) ≤ x are classified as level 2, those with 0.5x < F(SOH) ≤ 0.8x are classified as level 3, and those with F(SOH) ≤ 0.5x are classified as level 4 and directly eliminated. Figure 5 It is a schematic diagram of the test results of Example 2 provided according to an optional implementation manner of the present invention.

[0109] 3. Example 3

[0110] S31. Take 70 ternary monomer batteries of the same model, eliminate batteries with damaged appearance, severe deformation, and open-circuit voltage lower than 0.5V. There are 55 remaining batteries for testing. The eliminated batteries are collected for recycling;

[0111] S32. First, charge at a constant current of 0.5C to the upper limit voltage of 4.2V, then charge at a constant voltage of 4.2V until the cut-off current of 0.05C, set aside for 2 minutes. Then discharge at a constant current of 0.5C to 1.0V, set aside for 2 minutes, charge at a constant current of 0.5C to the upper limit voltage of 4.2V, and charge at a constant voltage of 4.2V until the cut-off current of 0.05C, and record the second charging capacity C1;

[0112] S33. Set aside at 50°C for 1 day (24 hours);

[0113] S34. After the high-temperature setting aside ends, discharge at a constant current of 0.5C to the lower limit voltage of 1.0V (0% SOC), record the discharge capacity C2, and calculate the self-discharge rate S: S = (C1 - C2) / C1 * 100%.

[0114] S35. Detect the open-circuit voltage U1 of the battery at 0% SOC; obtain the polarization voltage ΔU1 = U1 - U 下 ;

[0115] S36. Then charge at a constant current of 0.5C to the upper limit voltage of 4.2V, charge at a constant voltage of 4.2V until the cut-off current of 0.05C, record the charging capacity C, and use the charging capacity in this step as the remaining capacity of the battery; detect the open-circuit voltage U2 of the battery at 100% SOC at this time, and calculate the polarization voltage ΔU2 = U 上 - U2;

[0116] S{37}. Substitute the above measured parameters into the calculation formula of the battery health state evaluation model:

[0117] F(SOH) = f1 * C + f2 * (U 上 - U 下 ) / (ΔU1 + ΔU2) + f3 * 1 / S

[0118] Among them, f1, f2, and f3 are weighting factors, f1 + f2 + f3 = 10, 1 < f1 ≤ 3, 4 < f2 ≤ 7, 1.5 < f3 ≤ 4; in this example, f1 = 2, f2 = 5, and f3 = 3. The obtained parameters are shown in Table 3.

[0119] Table 3

[0120]

[0121]

[0122]

[0123] F(SOH) is sorted by value, and the average value x of the 11th to 40th (a total of 30) F(SOH) is taken as the health factor reference number.

[0124] S38. Classification of the battery to be tested: According to the reference number of the health factor F(SOH), a threshold is set. Batteries with F(SOH) > x are classified as level 1, 0.8x < F(SOH) ≤ x are classified as level 2, 0.5x < F(SOH) ≤ 0.8x are classified as level 3, and F(SOH) ≤ 0.5x are classified as level 4 and directly eliminated. Figure 6 It is a schematic diagram of the test results of Example 3 provided according to an optional implementation manner of the present invention.

[0125] In summary, the optional implementation manner of the present invention has the following advantages:

[0126] 1) After the preliminary screening, the batteries for pre-ladder utilization are first charged, which can effectively prevent the adverse effects caused by possible over-discharge during the battery storage process, and ensure that the batteries in better condition are selected in the largest quantity.

[0127] 2) Usually, as the service life of retired batteries increases, there is a phenomenon of continuous deposition of some active lithium. Lithium deposition is one of the important factors causing problems such as battery capacity attenuation, internal resistance increase, and self-discharge rate increase. However, the high-temperature storage in the screening and evaluation steps of the optional implementation manner of the present invention can activate some of the deposited lithium, reduce the internal resistance of the battery, improve and stabilize the battery capacity, and reduce the self-discharge rate in the future ladder utilization stage; at the same time, after high-temperature activation and then continuing the screening, it can ensure that a larger number of batteries meet the quality requirements of ladder utilization and exert the maximum value of ladder utilization.

[0128] 3) The method for screening and evaluating single batteries in the optional implementation manner of the present invention only involves conventional charge and discharge equipment and voltmeters, and the measured parameters are simple and intuitive, easy to implement, with low screening and evaluation costs and high efficiency.

[0129] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments.

[0130] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0131] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for screening and evaluating the cascade utilization of retired power cell batteries, characterized in that, include: Multiple initial batteries are charged to a first state of charge to obtain multiple target batteries and the charging amount corresponding to each of the multiple target batteries. The first state of charge is charged to an upper limit voltage and fully charged at a constant voltage at the upper limit voltage. A predetermined activation operation is performed on the plurality of target batteries to obtain a plurality of activated batteries, wherein the predetermined activation operation is high-temperature resting. Discharge the plurality of activated batteries to a second state of charge to obtain the discharge amount corresponding to each of the plurality of activated batteries, and the second polarization voltage corresponding to each of the plurality of activated batteries when discharged to the second state of charge, wherein the second state of charge is the discharge to the lower limit voltage; Based on the charging amount corresponding to the plurality of target batteries and the discharging amount corresponding to the plurality of activated batteries, the self-discharge rate corresponding to the plurality of target batteries is determined. The plurality of activated batteries are charged from the second state of charge to the first state of charge to obtain a first polarization voltage corresponding to each of the plurality of activated batteries; Based on the charge amount and self-discharge rate corresponding to the plurality of target batteries, and the first polarization voltage and second polarization voltage corresponding to the plurality of activated batteries, the state parameters corresponding to the plurality of activated batteries are determined. Based on the state parameters corresponding to the plurality of activated cells, the state levels corresponding to the plurality of activated cells are determined. The state parameters corresponding to the plurality of activated batteries are determined as follows: ， in, The state parameter, , and As a predetermined weighting factor, The charging capacity corresponding to each of the plurality of activated batteries when charging from the second state of charge to the first state of charge. These are the upper limit voltages corresponding to the plurality of activated cells, These are the lower limit voltages corresponding to the plurality of activated cells, These are the multiple second polarization voltages corresponding to the multiple activated cells when they reach the second state of charge during discharge. The first polarization voltage corresponding to each of the plurality of activated cells when they are charged from the second state of charge to the first state of charge. The self-discharge rate corresponds to each of the plurality of target batteries; Wherein, the second polarization voltage is The first polarization voltage is ,in, This is the open-circuit voltage of the battery in its second state of charge. This is the open-circuit voltage of the battery in its first state of charge.

2. The method according to claim 1, characterized in that, Before charging the multiple initial batteries to a first state of charge to obtain multiple target batteries and the charging amount corresponding to each of the multiple target batteries, the method further includes: Multiple initial batteries were charged and discharged for the first time according to predetermined current and predetermined voltage.

3. The method according to claim 1, characterized in that, Before charging the multiple initial batteries to a first state of charge to obtain multiple target batteries and the charging amount corresponding to the multiple target batteries, the method further includes: Identify the multiple batteries to be evaluated; The plurality of batteries are screened according to predetermined conditions, and the batteries that meet the predetermined conditions are determined as initial batteries to obtain the plurality of initial batteries. The predetermined conditions are: the degree of damage or deformation of the battery appearance is within a predetermined allowable range, and the open circuit voltage of the battery is higher than a predetermined value.

4. The method according to claim 1, characterized in that, The predetermined activation operation on the plurality of target batteries to obtain a plurality of activated batteries includes: The plurality of target batteries are placed within a predetermined temperature range for a predetermined time to obtain the plurality of activated batteries.

5. The method according to claim 4, characterized in that, The predetermined temperature range is 30℃~70℃, and the predetermined duration is 4h~158h.

6. The method according to claim 1, characterized in that, The self-discharge rate of the multiple target batteries is determined as follows: in, The self-discharge rate is... The charging amount corresponds to each of the multiple target batteries. The discharge amount corresponds to each of the plurality of activated batteries.

7. The method according to claim 1, characterized in that, The step of determining the state level corresponding to each of the plurality of activated cells based on the state parameters corresponding to each of the plurality of activated cells includes: The state parameters corresponding to the plurality of activated batteries are sorted according to their numerical values; Based on the sorting results and the predetermined sorting order range, multiple target state parameters are determined; Based on the multiple target state parameters, target state evaluation parameters are obtained; Based on the target state assessment parameters and the predetermined state level weighting factors, determine the range of state assessment parameters corresponding to multiple state levels respectively; Based on the range of the state assessment parameters and the state parameters corresponding to the plurality of target batteries, the state levels corresponding to the plurality of activated batteries are determined.

8. The method according to any one of claims 1 to 7, characterized in that, The method further includes: Based on the state levels corresponding to the multiple activated batteries, the multiple activated batteries are utilized in a tiered manner.

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