Stepped charging and discharging load adjusting method for recycling waste lithium battery

Abstract

The invention relates to the technical field of batteries, and provides a stepped load adjusting method for recycling waste lithium batteries, the method comprises an electric quantity release stage, a capacity calibration stage and a consistent load adjusting stage, the defects of a traditional load adjusting method are eliminated through three-stage gradient current, and efficient capacity grading of the waste lithium batteries is achieved; in addition, according to the method, the voltage change is analyzed, the voltage drop is used as a state index, calculation of an SOC model is abandoned, and the response speed is increased while the computing power requirement is reduced.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a stepped charge-discharge load regulation method for recycling waste lithium batteries. Background Technology

[0002] With the rapid development of the global new energy vehicle industry, the retirement of power batteries has become an unavoidable challenge. According to statistics from the China Association of Automobile Manufacturers, my country's new energy vehicle sales reached 6.887 million units in 2022 (a year-on-year increase of 90%). Based on this, it is estimated that the installed capacity of power batteries will also surge accordingly. Assuming an average service life of 5 years for power batteries, it is estimated that by 2030, the total amount of retired batteries in my country will exceed 2.37 million tons, and the market size is expected to reach hundreds of billions of yuan. If these retired batteries are not scientifically treated, they will cause various hazards, such as heavy metal pollution, electrolyte leakage, and resource waste.

[0003] In response to this pressing situation, my country's "Interim Measures for the Management of Recycling and Utilization of Power Batteries for New Energy Vehicles" clearly proposes the recycling principle of "first using in stages and then regenerating," aiming to extend the entire life cycle of batteries through a multi-level utilization model, alleviate environmental pressure, and tap into remaining economic value.

[0004] Currently, the secondary utilization of spent lithium batteries requires restoring the performance of retired batteries and adjusting their consistency before reuse. However, traditional load adjustment methods have many drawbacks:

[0005] (1) Traditional load adjustment strategies require battery packs to operate synchronously, and their performance is limited by the weakest single cell. High-capacity batteries cannot fully release energy, while low-capacity batteries are prone to overcharging / over-discharging and accelerated damage.

[0006] (2) The aging mechanism of retired batteries is complicated (such as lithium loss, active material decay or structural damage, etc.), and the performance of recycled lithium-ion batteries is inconsistent and the battery pack efficiency is not high.

[0007] (3) The SOC estimation error of traditional BMS based on a fixed model is as high as 10% to 15%;

[0008] (4) Load adjustment is generally used in the fields of new battery manufacturing and waste battery recycling. However, since new batteries do not need to consider aging issues such as internal micro-short circuits and active material shedding, the load adjustment method for waste battery recycling cannot simply refer to the load adjustment scheme for new batteries. Summary of the Invention

[0009] To address the technical problems existing in the background art, this invention proposes a stepped charge-discharge load regulation method for recycling waste lithium-ion batteries, comprising the following steps:

[0010] S3, Consistent Load Adjustment Phase

[0011] S3-1. Charge the waste lithium batteries after capacity testing. Increase the charging current from 0C to the fourth target value for 3-8 minutes. Maintain the fourth target value current for 60-120 minutes. After charging, let them rest for 3-5 minutes to obtain waste lithium batteries in A% SOC state.

[0012] S3-2. Discharge the waste lithium battery in A% SOC state in S3-1. Increase the discharge current from 0C to the fifth target value for 3-8 minutes. Maintain the fifth target value current for 1-20 minutes to obtain the waste lithium battery in B% SOC state.

[0013] S3-3. After letting the waste lithium batteries in the B% SOC state from step S3-2 rest for 3-5 minutes, detect the load adjustment termination voltage, retain the waste lithium batteries whose load adjustment termination voltage is within the predetermined range, and monitor the voltage drop value (dV / dt) of the retained waste lithium batteries.

[0014] S3-4. Retain waste lithium batteries with voltage drop values ​​within a predetermined range, and combine waste lithium batteries with similar voltage drop values ​​into new battery packs.

[0015] In this invention, the gradual current significantly reduces the polarization phenomenon during the battery charging and discharging process. Only a very short rest time is required to accurately and efficiently redistribute the battery through a single voltage drop value.

[0016] In step S3:

[0017] The fourth and fifth target values ​​are each independently selected from 0.1-0.4C;

[0018] B and A are each independently selected from 20-40, and A > B.

[0019] In step S3-3:

[0020] When the waste lithium battery is an LFP battery, the predetermined range of the load adjustment termination voltage is 3.2-3.35V;

[0021] When the waste lithium battery is an NCM-based battery, the predetermined range of the load adjustment termination voltage is 3.5-3.7V.

[0022] In steps S3-4:

[0023] The predetermined range for the voltage drop value is 0-0.005V for 3 days and 0-0.025V for 14 days.

[0024] In this invention, the detection of the load-adjusting voltage not only provides an initial voltage value for the subsequent voltage drop, but also verifies whether the SOC value is within the range of 20-40% SOC.

[0025] The stepped charge-discharge load regulation method for recycling waste lithium batteries proposed in this invention further includes the following steps:

[0026] S1, Power Release Phase;

[0027] S2, Battery capacity calibration stage.

[0028] In this invention, the battery capacity calibration is a preliminary step and an important indicator for the redistribution and reorganization of waste batteries.

[0029] Step S1 includes:

[0030] S1-1. After leaving the waste lithium battery for 3-5 minutes, discharge it. Increase the discharge current from 0C to the first target value and continue for 3-8 minutes.

[0031] S1-2, Maintain a constant current at the first target value to complete the release of the main capacity of the waste lithium battery;

[0032] S1-3. After the main capacity of the waste lithium battery is released, the discharge current is gradually reduced from the first target value to 0C for 3-8 minutes. Then the waste lithium battery is left to stand for 3-5 minutes to obtain a waste lithium battery in 0% SOC state.

[0033] In step S1:

[0034] The first target value is 0.3-0.7C.

[0035] Step S2 includes:

[0036] S2-1. Charge the waste lithium battery at 0% SOC by gradually increasing the charging current from 0C to the second target value for 3-8 minutes and record the charging capacity C0 during this stage.

[0037] S2-2, Maintain a constant current at the second target value and continue charging for 120-180 minutes to complete the injection of the main capacity of the waste lithium battery;

[0038] S2-3. Under the charging cutoff voltage of the waste lithium battery, constant voltage charging is performed, and the charging current is reduced from the second target value to the cutoff current. The total capacity C1 of steps S2-2 and S2-3 is recorded. After charging is completed, the waste lithium battery is left to stand for 3-5 minutes to obtain a waste lithium battery in 100% SOC state.

[0039] S2-4. Perform the first discharge on the waste lithium battery in 100% SOC state. Increase the discharge current from 0C to the third target value and continue for 3-8 minutes. Then maintain the third target value current for continuous discharge for 120-180 minutes to complete the release of the main capacity of the waste lithium battery. After the first discharge of the waste lithium battery in 100% SOC state is completed, let the battery rest for 5-10 minutes.

[0040] S2-5. Perform a second discharge on the waste lithium battery that has completed the main capacity release in step S2-4. The discharge current gradually decreases from the third target value to the step value 1, and the duration is 3-8 minutes. Maintain the step value 1 and continue discharging for 30-120 minutes. After completion, let the battery rest for 3-5 minutes.

[0041] S2-6. Perform a third discharge on the waste lithium battery that has completed the second discharge in step S2-5. The discharge current decreases from step value 1 to step value 2, and the duration is 3-8 minutes. Then the battery is kept at step value 2 and discharged for 10-60 minutes. After completion, let the battery rest for 1-5 minutes to obtain a waste lithium battery with 0% SOC.

[0042] S2-7. The total charging capacity C0+C1 of steps S2-1, S2-2 and S2-3 is the maximum charging capacity of the battery. The total discharging capacity C2+C3+C4 of steps S2-4, S2-5 and S2-6 is the maximum discharging capacity of the battery. The waste lithium batteries are allocated for the first time according to the capacity value.

[0043] In step S2:

[0044] The second target value and the third target value are each independently selected from 0.3-0.7C; the cutoff current is ≤0.02C; the step value 1 is 0.1-0.3C; and the step value 2 is 0.02-0.1C.

[0045] In step S2-3:

[0046] When the waste lithium battery is an LFP battery, the charging cut-off voltage is 3.65V;

[0047] When the waste lithium battery is an NCM-based battery, the charging cut-off voltage is 4.2V.

[0048] In this invention, the voltage drop value and the rated charge / discharge capacity can be used as parameters for subsequent battery pack grouping.

[0049] In this invention, the stepped load adjustment method for waste lithium batteries mainly includes the following principles:

[0050] (1) Ordered migration mechanism of lithium ions: The charging and discharging of lithium-ion batteries is essentially the directional migration of lithium ions between the positive and negative electrodes. During charging, Li + The material is extracted from the positive electrode lattice, passes through the electrolyte channel and the separator, and then embeds into the negative electrode graphite layered structure. The reaction that occurs during discharge is the opposite of that during charging. This cycle is the charging and discharging process of the battery.

[0051] (2) Gradual Current Protection Electrode: Stepped charging and discharging controls the gradual change of current to match the lithium ion insertion / extraction rate with the lattice change rate of the electrode material, reducing ion transport resistance. As the current gradually increases from 0C to the target value, Li... + Orderly detachment from the crystal lattice avoids excessive local stress, protecting the electrode material and extending the lifespan of the lithium battery; as the current gradually decreases from the target value to 0C, the residual Li... + Sufficient diffusion time allows for a more uniform ion distribution on the electrode surface, reducing lithium metal deposition on the electrode surface.

[0052] (3) Reduce polarization effect and capacity release: Adding a short rest time before and after each charge and discharge stage can effectively reduce or eliminate concentration polarization and balance the battery potential.

[0053] Beneficial effects of this invention:

[0054] (1) The method used in this application can eliminate the passive static stage of 30 to 60 minutes in the traditional load adjustment scheme, shorten the equipment running time by 3-7%, significantly improve the recovery efficiency, and reduce the overall energy consumption by 2% to 10%.

[0055] (2) After the load adjustment, the battery packs of this scheme have similar capacities and basically consistent voltage drops, which ensures the performance consistency of the battery packs and eliminates the overall systemic shortcomings.

[0056] (3) This invention uses voltage drop (dV / dt) as a state indicator by analyzing the voltage change trend, abandoning the SOC model calculation, reducing computing power requirements while improving response speed and reducing estimation errors;

[0057] (4) The pressure drop can be monitored in real time, without the need for multiple load tests to measure the pressure drop. The operation is simple and the working cycle is short. Attached Figure Description

[0058] Figure 1 This is a flow topology diagram of the stepped charge-discharge load adjustment method for waste lithium batteries according to the present invention. Detailed Implementation

[0059] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0061] The technical solution of the present invention will now be described more clearly and completely with reference to specific embodiments and comparative examples.

[0062] Example 1

[0063] This embodiment proposes a stepped charge-discharge load regulation method for recycling waste lithium-ion batteries. The specific steps are as follows (maintaining a constant temperature of 25°C in operation steps S1-S3):

[0064] S1, Charge Release Phase:

[0065] S1-1. Let the waste lithium iron phosphate batteries rest for 4 minutes, then discharge the waste lithium iron phosphate batteries after resting. Gradually increase the discharge current from 0C to the target value of 0.5C for 5 minutes.

[0066] S1-2, Maintain a constant current of 0.5C to complete the release of the main capacity of the waste lithium iron phosphate battery;

[0067] S1-3. After the main capacity of the waste lithium iron phosphate battery is released, continue deep discharge, gradually reduce the discharge current from the target value of 0.5C to 0C for 5 minutes, and then let the waste lithium battery rest for 4 minutes to obtain a waste lithium iron phosphate battery in 0% SOC state.

[0068] S2, Battery Capacity Calibration Stage:

[0069] S2-1. Charge the waste lithium iron phosphate battery with 0% SOC. Gradually increase the charging current from 0C to the target value of 0.5C for 5 minutes and record the charging capacity C0 during this stage.

[0070] S2-2, Maintain a constant current of 0.5C for 150 minutes to complete the injection of the main capacity of the waste lithium iron phosphate battery;

[0071] S2-3. Under a constant voltage of 3.65V, continue to charge the waste lithium iron phosphate battery. The charging current is gradually reduced from 0.5C to the cutoff current of 0.01C. Record the capacity C1 during the constant current and constant voltage charging stage. C0+C1 is calibrated as the maximum charging capacity of the battery. After charging is completed, let the waste lithium iron phosphate battery rest for 4 minutes to obtain a waste lithium battery in 100% SOC state.

[0072] S2-4. Perform the first discharge on the waste lithium iron phosphate battery at 100% SOC. Gradually increase the discharge current from 0C to the target value of 0.5C and continue for 5 minutes. Then maintain a constant current of 0.5C for 150 minutes to complete the release of the main capacity of the waste lithium iron phosphate battery. Record the total discharge capacity C2 of the first discharge stage. After completion, let the battery rest for 4 minutes.

[0073] S2-5. Perform a second discharge on the waste lithium iron phosphate battery that has completed the main capacity release in step S2-4. The discharge current is gradually reduced from the target value of 0.5C to the step value 1 (0.2C) for 5 minutes. Then the battery is kept at the step value 1 (0.2C) for 100 minutes. Record the total discharge capacity C3 of the second discharge stage. After completion, let the battery rest for 4 minutes.

[0074] S2-6. Perform a third discharge on the waste lithium iron phosphate battery that has completed the second discharge in step S2-5. The discharge current gradually decreases from step value 1 (0.2C) to step value 2 (0.05C) for 5 minutes. Then, the battery is discharged continuously at step value 2 (0.05C) for 30 minutes to ensure that the battery is completely discharged. After completion, the battery is left to stand for 3 minutes. Record the total discharge capacity C4 of the third discharge stage to obtain the waste lithium iron phosphate battery with 0% SOC.

[0075] S2-7. Let C0+C1 be the maximum charging capacity of the battery, and calculate the sum of C2+C3+C4 as the maximum discharging capacity of the battery. Based on the capacity value, the waste lithium iron phosphate batteries are allocated for the first time, and the capacity difference of individual cells in the battery pack is kept within ±5%.

[0076] S3, Consistent Load Adjustment Phase:

[0077] S3-1. Charge the waste lithium iron phosphate batteries after the first allocation. The charging current is gradually increased from 0C to the target value of 0.2C and held for 5 minutes. Then, the constant current of 0.2C is maintained for 90 minutes. After completion, the batteries are left to rest for 4 minutes to obtain waste lithium iron phosphate batteries with 30% SOC.

[0078] S3-2. Discharge the waste lithium iron phosphate battery with 30% SOC in step S3-1. Gradually increase the discharge current from 0C to the target value of 0.2C for 5 minutes, and then maintain a constant current of 0.2C for 10 minutes to obtain a waste lithium iron phosphate battery with 26.67% SOC.

[0079] S3-3. Let the waste lithium iron phosphate batteries with a state of 26.67% SOC in step S3-2 rest for 5 minutes, detect the battery load adjustment termination voltage, retain the waste lithium batteries with a load adjustment termination voltage between 3.2-3.35V, and monitor the voltage drop value (dV / dt) of the batteries.

[0080] S3-4. Retain waste lithium batteries with a voltage drop of 0-0.005V for 3 days and a voltage drop of 0-0.025V for 14 days. Based on the voltage drop value (dV / dt), redistribute the conditioned waste lithium iron phosphate batteries. Assign batteries with the same or similar voltage drop and capacity to the same group and recombine them into a brand new, highly consistent waste lithium iron phosphate battery pack.

[0081] Example 2

[0082] This embodiment proposes a stepped charge-discharge load regulation method for recycling waste lithium-ion batteries. The specific steps are as follows (maintaining a constant temperature of 25°C in operation steps S1-S3):

[0083] S1, Charge Release Phase:

[0084] S1-1. Let the waste nickel-cobalt-manganese lithium oxide batteries rest for 3 minutes, and then discharge the waste nickel-cobalt-manganese lithium oxide batteries after resting. The discharge current is gradually increased from 0C to the target value of 0.4C and lasts for 6 minutes.

[0085] S1-2, Maintain a constant current of 0.4C to complete the release of the main capacity of the waste nickel-cobalt-manganese lithium oxide battery;

[0086] S1-3. After the main capacity of the waste nickel-cobalt-manganese lithium oxide battery is released, continue deep discharge, gradually reduce the discharge current from the target value of 0.4C to 0C for 4 minutes, and then let the waste lithium battery rest for 3 minutes to obtain a waste nickel-cobalt-manganese lithium oxide battery in 0% SOC state.

[0087] S2, Battery Capacity Calibration Stage:

[0088] S2-1. Charge the waste nickel-cobalt-manganese lithium oxide battery at 0% SOC. Gradually increase the charging current from 0C to the target value of 0.4C for 4 minutes and record the charging capacity C0 during this stage.

[0089] S2-2, Maintain a constant current of 0.4C for 120 minutes to complete the injection of the main capacity of the waste nickel-cobalt-manganese lithium oxide battery;

[0090] S2-3. Under a constant voltage of 4.2V, continue to charge the waste nickel-cobalt-manganese lithium oxide battery. The charging current is gradually reduced from 0.4C to the cutoff current of 0.01C. Record the capacity C1 during the constant current and constant voltage charging stage. C0+C1 is calibrated as the maximum charging capacity of the battery. After charging is completed, let the waste nickel-cobalt-manganese lithium oxide battery rest for 4 minutes to obtain a waste nickel-cobalt-manganese lithium oxide battery in 100% SOC state.

[0091] S2-4. Perform the first discharge on the waste nickel-cobalt-manganese lithium oxide battery at 100% SOC. The discharge current is gradually increased from 0C to the target value of 0.4C and held for 4 minutes. Then, maintain a constant current of 0.4C for 120 minutes to complete the release of the main capacity of the waste nickel-cobalt-manganese lithium oxide battery. Record the total discharge capacity C2 of the first discharge stage. After completion, let the battery rest for 3 minutes.

[0092] S2-5. Perform a second discharge on the waste nickel-cobalt-manganese lithium oxide battery that has completed the main capacity release in step S2-4. The discharge current is gradually reduced from the target value of 0.4C to the step value 1 (0.15C) for 5 minutes. Then the battery is kept at the step value 1 (0.15C) for 50 minutes. Record the total discharge capacity C3 of the second discharge stage. After completion, let the battery rest for 4 minutes.

[0093] S2-6. Perform a third discharge on the waste lithium battery that has completed the second discharge in step S2-5. The discharge current gradually decreases from step value 1 (0.15C) to step value 2 (0.05C) for 5 minutes. Then, the battery is discharged continuously at step value 2 (0.05C) for 15 minutes to ensure that the battery is completely discharged. After completion, the battery is left to stand for 3 minutes. Record the total discharge capacity C4 of the third discharge stage to obtain the waste lithium battery in 0% SOC state.

[0094] S2-7. Let C0+C1 be the maximum charging capacity of the battery, and calculate the sum of C2+C3+C4 as the maximum discharging capacity of the battery. Based on the capacity value, the waste nickel-cobalt-manganese lithium oxide batteries are allocated for the first time, and the capacity difference of individual cells in the battery pack is kept within ±5%.

[0095] S3, Consistent Load Adjustment Phase:

[0096] S3-1. Charge the waste nickel-cobalt-manganese lithium oxide batteries after the first allocation. The charging current is gradually increased from 0C to the target value of 0.3C and held for 5 minutes. Then, the constant current of 0.3C is maintained for 70 minutes. After completion, the batteries are left to rest for 4 minutes to obtain waste nickel-cobalt-manganese lithium oxide batteries with 40% SOC.

[0097] S3-2. Discharge the waste nickel-cobalt-manganese lithium oxide battery with a state of 40% SOC in step S3-1. Gradually increase the discharge current from 0C to the target value of 0.3C for 5 minutes, and then maintain a constant current of 0.3C for 8 minutes to obtain a waste nickel-cobalt-manganese lithium oxide battery with a state of 36% SOC.

[0098] S3-3. Let the waste nickel-cobalt-manganese lithium oxide batteries in the 36% SOC state of step S3-2 rest for 5 minutes, detect the battery load adjustment termination voltage, retain the waste nickel-cobalt-manganese lithium oxide batteries with load adjustment termination voltage between 3.5-3.7V, and monitor the voltage drop value (dV / dt) of the batteries.

[0099] S3-4. Retain spent nickel-cobalt-manganese lithium oxide batteries with a voltage drop of 0-0.005V for 3 days and 0-0.025V for 14 days. Redistribute the adjusted spent nickel-cobalt-manganese lithium oxide batteries according to the voltage drop value (dV / dt). Assign batteries with the same or similar voltage drop and capacity to the same group and recombine them into a brand new, highly consistent spent nickel-cobalt-manganese lithium oxide battery pack.

[0100] Comparative Example 1

[0101] This comparative example proposes a charging and discharging load adjustment method for recycling waste lithium-ion batteries. The specific steps are the same as in Example 1, except that the charging and discharging current in step S3 and the consistency load adjustment stage are all replaced with a constant current of 0.2C.

[0102] Comparative Example 1 uses a traditional load adjustment method, namely high-current constant-current charging and discharging load adjustment. However, due to the excessive change in the initial current value, Li... + The instantaneous large-scale insertion and extraction can cause stress concentration in the electrode lattice, resulting in microcracks and damage to the electrode material. When traditional charging and discharging terminates, the current stops abruptly, and the uneven distribution of ions on the electrode surface can lead to concentration polarization.

[0103] Comparative Example 2

[0104] This comparative example proposes a stepped charge-discharge load regulation method for recycling waste lithium batteries. The specific steps are the same as in Example 1, except that "maintain a constant temperature of 25°C in operation steps S1-S3" is changed to "maintain a constant temperature of 45°C in operation steps S1-S3".

[0105] In Comparative Example 2, although high temperature environment will accelerate the internal physicochemical reaction of the battery, since the load adjustment object of this invention is a recycled waste lithium battery, high temperature will aggravate the internal electrochemical reaction and related side reaction of the waste lithium battery, causing the loss of active materials, resulting in unnecessary loss and waste.

[0106] Comparative Example 3

[0107] This comparative example proposes a stepped charge-discharge load adjustment method for recycling waste lithium batteries. The specific steps are the same as in Example 1, except that step "S2, battery capacity calibration stage" is omitted.

[0108] In Comparative Example 3, since most of the recycled waste lithium batteries have been cycled multiple times, their capacity has changed compared to new batteries. When adjusting the load without knowing the capacity of the waste lithium batteries, it is impossible to group them according to the capacity differences. As a result, the performance of the battery packs after redistribution and recombination is inconsistent, and the systemic shortcomings are obvious.

[0109] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A stepwise charge-discharge load regulation method for recycling waste lithium batteries, characterized by, Comprising the following steps: S3, consistency load stage S3-1, charging the split capacity of the waste lithium battery, the charging current is increased from 0C to the fourth target value, the duration is 3-8 min, the current is maintained at the fourth target value for 60-120 min, and the waste lithium battery is placed for 3-5 min after charging to obtain a waste lithium battery with A% SOC state; S3-2, discharging the waste lithium battery with A% SOC state in S3-1, the discharging current is increased from 0C to the fifth target value, the duration is 3-8 min, and the waste lithium battery with B% SOC state is obtained by maintaining the fifth target value current for 1-20 min discharging; S3-3, after the waste lithium battery with B% SOC state in step S3-2 is placed for 3-5 min, the load termination voltage is detected, the waste lithium battery with the load termination voltage within the predetermined range is reserved, and the pressure drop value (dV / dt) of the reserved waste lithium battery is monitored; S3-4, reserving the waste lithium battery with the pressure drop value within the predetermined range, and combining the waste lithium batteries with similar pressure drop values into a new battery pack.

2. The step charging and discharging load adjusting method for recycling waste lithium batteries according to claim 1, characterized in that, In step S3: The fourth target value and the fifth target value are independently selected from 0.1-0.4C; B and A are independently selected from 20-40, and A>B.

3. The step charging and discharging load adjusting method for recycling waste lithium batteries according to claim 1 or 2, characterized in that, In step S3-3: When the waste lithium battery is LFP battery, the predetermined range of load termination voltage is 3.2-3.35V; When the waste lithium battery is NCM battery, the predetermined range of load termination voltage is 3.5-3.7V.

4. The step charging and discharging load regulating method for recycling waste lithium batteries according to any one of claims 1-3, characterized in that, In step S3-4: The predetermined range of the pressure drop value is 0-0.005V for 3 days and 0-0.025V for 14 days.

5. The step charging and discharging load adjusting method for recycling waste lithium batteries according to any one of claims 1-4, characterized in that, Further comprising the following steps: S1, power release stage; S2, battery capacity calibration stage.

6. The step charging and discharging load adjusting method for recycling waste lithium batteries according to claim 5, characterized in that, Step S1 includes: S1-1, discharging the waste lithium battery after placing for 3-5 min, the discharging current is increased from 0C to the first target value, and the duration is 3-8 min; S1-2, maintaining the first target value constant current to complete the release of the main capacity of the waste lithium battery; S1-3, after completing the release of the main capacity of the waste lithium battery, gradually decreasing the discharging current from the first target value to 0C, and the duration is 3-8 min, and then placing the waste lithium battery for 3-5 min to obtain a waste lithium battery with 0% SOC state.

7. The step charging and discharging load adjusting method for recycling waste lithium batteries according to claim 6, characterized in that, In step S1: The first target value is 0.3-0.7C.

8. The step charging and discharging load regulating method for recycling waste lithium batteries according to any one of claims 5-7, characterized in that, Step S2 includes: S2-1, charging the waste lithium battery with 0% SOC state, the charging current is gradually increased from 0C to the second target value, and the duration is 3-8 min; S2-2, maintaining the second target value constant current for 120-180 min to complete the injection of the main capacity of the waste lithium battery; S2-3, constant voltage charging at the charging cutoff voltage of the waste lithium battery, the charging current is decreased from the second target value to the cutoff current, and the waste lithium battery is placed for 3-5 min after charging to obtain a waste lithium battery with 100% SOC state; S2-4, the first discharge of the waste lithium battery in 100% SOC state, the discharge current increases from 0C to the third target value, lasts for 3-8 min, and then maintains the third target value current for 120-180 min, completes the release of the main capacity of the waste lithium battery, and the waste lithium battery in 100% SOC state is discharged for the first time. After 5-10 min, the battery is placed; S2-5, the second discharge of the waste lithium battery in step S2-4 which completes the release of the main capacity, the discharge current gradually decreases from the third target value to the step value 1, lasts for 3-8 min, maintains the step value 1 for 30-120 min, and then the battery is placed for 3-5 min after completion; S2-6, the third discharge of the waste lithium battery in step S2-5 which completes the second discharge, the discharge current decreases from the step value 1 to the step value 2, lasts for 3-8 min, and then the battery maintains the step value 2 for 10-60 min, and then the battery is placed for 1-5 min after completion, and the waste lithium battery in 0% SOC state is obtained; S2-7, record the total charging capacity C1 of step S2-1, step S2-2 and step S2-3 as the maximum charging capacity of the battery, record the total discharge capacity C2+C3+C4 of step S2-4, step S2-5 and step S2-6 as the maximum discharge capacity of the battery, and according to the capacity value, the waste lithium battery is first allocated.

9. The step charging and discharging load adjusting method for recycling waste lithium batteries according to claim 8, characterized in that, In step S2: The second target value and the third target value are independently selected from 0.3-0.7C; the cutoff current is ≤0.02C; the step value 1 is 0.1-0.3C; and the step value 2 is 0.02-0.1C.

10. The step charging and discharging load adjusting method for recycling waste lithium batteries according to claim 8 or 9, characterized in that, In step S2-3: When the waste lithium battery is LFP battery, the charging cutoff voltage is 3.65V; When the waste lithium battery is NCM battery, the charging cutoff voltage is 4.2V.

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