Secondary battery discharge state sorting method and device

Abstract

The present application discloses a method and device for sorting a secondary battery in a discharge state, wherein the sorting method includes charging a secondary battery to be sorted to a first state of charge at a first charging rate; after standing for a first predetermined time, discharging the secondary battery to be sorted to a second state of charge at at least two discharge rates with a decreasing gradient, so that the secondary battery to be sorted is in a discharge state; after standing for a second predetermined time, trickle charging the secondary battery to be sorted in a discharge state, and maintaining the power of the secondary battery to be sorted in a discharge state at the second state of charge. The above scheme can shorten the time for sorting a secondary battery in a discharge state.

Description

Technical Field

[0001] This invention generally relates to the field of battery technology, and specifically to a method and apparatus for sorting secondary batteries in their discharge state. Background Technology

[0002] After the secondary batteries are manufactured, they need to be sorted to determine their grade. During sorting, the K-value (K-value refers to the voltage drop of the battery per unit time, a physical quantity used to describe the self-discharge rate of the cell) is an important indicator. The K-value is calculated by measuring the open-circuit voltage twice after the secondary battery has been depolarized, with a certain time interval between the measurements. The difference between the two measured open-circuit voltages is then divided by the time interval to obtain the K-value. If depolarization is incomplete, the obtained K-value will be too large, leading to misclassification during sorting.

[0003] Since the calculation of the K value needs to be performed after the secondary battery has been depolarized, the depolarization time for a secondary battery in the charging state is generally less than 48 hours. However, for a secondary battery in the discharging state, the depolarization time is generally more than 72 hours. It is easy to see that the sorting time required for secondary batteries in the discharging state is significantly longer than that required for secondary batteries in the charging state. How to shorten the sorting time required for secondary batteries in the discharging state is a technical problem to be solved in this field. Summary of the Invention

[0004] This application aims to provide a method, apparatus, device, and storage medium for sorting secondary batteries in their discharge state, at least for shortening the time required for sorting secondary batteries in their discharge state.

[0005] In a first aspect, the present invention provides a method for sorting secondary batteries in their discharged state, comprising the following steps:

[0006] The secondary batteries to be sorted are charged to the first state of charge at the first charging rate.

[0007] After being left to stand for a first predetermined period of time, the secondary battery to be sorted is discharged to a second state of charge at at least two discharge rates with a gradient decrease, so that the secondary battery to be sorted is in a discharged state.

[0008] After being left to stand for a second predetermined period of time, the secondary battery to be sorted in the discharge state is trickle charged, and the charge of the secondary battery to be sorted in the discharge state is maintained at the second state of charge.

[0009] After trickle charging, the secondary batteries to be sorted are left to stand for a third predetermined time. The first open-circuit voltage of the secondary batteries to be sorted is obtained. Then, after standing for a fourth predetermined time, the second open-circuit voltage of the secondary batteries to be sorted is obtained. Based on the first open-circuit voltage, the second open-circuit voltage, and the fourth predetermined time, the K value of the secondary batteries to be sorted is determined. The secondary batteries to be sorted are then classified based on the K value. The third predetermined time is 12h-48h.

[0010] As one possible implementation method, the trickle charging of the secondary battery to be sorted in the discharged state specifically includes:

[0011] The secondary batteries to be sorted in the discharged state are charged with a constant current or constant current and constant voltage of 0.08C-0.1C for 1min-2min.

[0012] As one possible implementation, charging the secondary battery to be sorted to a first state of charge at a first charging rate specifically includes:

[0013] The secondary batteries to be sorted are charged to the first state of charge (SOC) at the first charging rate using constant current or constant current and constant voltage. The first charging rate is 0.5C-1C, and the first SOC is 30%-90% SOC.

[0014] One possible implementation includes two discharge rates, namely a first discharge rate and a second discharge rate, wherein the secondary battery to be sorted is discharged at a constant current to the second state of charge using the first discharge rate and the second discharge rate respectively; the first discharge rate is 0.8C-1C, the second discharge rate is 0.1C-0.3C, and the second state of charge is 25%SOC-60%SOC.

[0015] One possible implementation includes three discharge rates, namely a first discharge rate, a second discharge rate, and a third discharge rate, wherein the secondary battery to be sorted is discharged at a constant current to the second state of charge in sequence at the first discharge rate, the second discharge rate, and the third discharge rate; the first discharge rate is 0.8C-1C, the second discharge rate is 0.1C-0.3C, the third discharge rate is 0.02C-0.05C, and the second state of charge is 25% SOC-60% SOC.

[0016] As one possible implementation, before charging the secondary battery to be sorted to a first state of charge at the first charging rate, the method further includes:

[0017] According to the correspondence between battery type and target charging voltage, the secondary battery to be sorted is charged to the first target voltage at the second charging rate, and then charged to the cutoff at the third charging rate, wherein the second charging rate is greater than the third charging rate;

[0018] After a predetermined period of time, the secondary batteries to be sorted are discharged to the second target voltage at a fourth discharge rate, according to the correspondence between battery type and target discharge voltage.

[0019] As one possible implementation, charging the secondary battery to be sorted to the first target voltage at the second charging rate specifically involves:

[0020] The secondary battery to be sorted is charged to a first target voltage at a second charging rate of 0.33C-1C and a third charging rate of 0.04C-0.06C.

[0021] As an implementation method, discharging the secondary battery to be sorted to the second target voltage at the fourth discharge rate specifically includes:

[0022] The secondary battery to be sorted is discharged at a constant current to the second target voltage at a fourth discharge rate of 0.33C-1C.

[0023] As an implementation method, the fifth predetermined duration is 5 min to 30 min.

[0024] As an implementation method, the first predetermined duration and the second predetermined duration are 5min-30min respectively; the fourth predetermined duration is 110h-130h.

[0025] In a second aspect, the present invention provides a secondary battery power regulation device, comprising:

[0026] A charging unit is used to charge the secondary battery to be sorted to a first state of charge at a first charging rate.

[0027] A discharge unit is used to discharge the secondary battery to be sorted to the second state of charge at at least two discharge rates with a gradient decrease after the secondary battery to be sorted has been charged to the first state of charge and left to stand for a first predetermined time, so that the secondary battery to be sorted is in a discharged state.

[0028] The charging unit is further configured to trickle charge the secondary battery to be sorted in the discharge state after it has been discharged to the second state of charge and left to stand for a second predetermined period of time, and to maintain the charge of the secondary battery to be sorted in the discharge state at the second state of charge.

[0029] As an implementation method, the charging unit is used to charge the secondary battery to be sorted in the discharged state at a constant current of 0.08C-0.1C or a constant current and constant voltage for 1min-2min.

[0030] As an implementation method, the charging unit is used to charge the secondary battery to be sorted to the first state of charge at a constant current or constant current and constant voltage at the first charging rate; the first charging rate is 0.5C-1C, and the first state of charge is 30%SOC-90%SOC.

[0031] One possible implementation includes two discharge rates, namely a first discharge rate and a second discharge rate.

[0032] The discharge unit is used to discharge the secondary battery to be sorted, which is charged to the first state of charge, to the second state of charge in sequence at the first discharge rate and the second discharge rate, respectively, and discharge it to the second state of charge at a constant current; the first discharge rate is 0.8C-1C, the second discharge rate is 0.1C-0.3C, and the second state of charge is 25%SOC-60%SOC.

[0033] As an implementation method, it includes three discharge rates, namely a first discharge rate, a second discharge rate, and a third discharge rate;

[0034] The discharge unit is used to discharge the secondary battery to be sorted, which is charged to the first state of charge, to the second state of charge in sequence at the first discharge rate, the second discharge rate, and the third discharge rate, respectively, and discharge it to the second state of charge at a constant current; the first discharge rate is 0.8C-1C, the second discharge rate is 0.1C-0.3C, the third discharge rate is 0.02C-0.05C, and the second state of charge is 25%SOC-60%SOC.

[0035] Thirdly, the present invention provides a secondary battery discharge state sorting device, including the above-mentioned secondary battery power adjustment state device;

[0036] It also includes a sorting unit, which is used to obtain the first open-circuit voltage of the secondary battery to be sorted after trickle charging and resting for a third predetermined time, and then obtain the second open-circuit voltage of the secondary battery to be sorted after resting for a fourth predetermined time. Based on the first open-circuit voltage, the second open-circuit voltage and the fourth predetermined time, the K value of the secondary battery to be sorted is determined, and the secondary battery to be sorted is classified based on the K value; the third predetermined time is 12h-48h.

[0037] Fourthly, the present invention provides a computing device having a computer program stored thereon, the computer program being used to implement the above-described secondary battery discharge state sorting method.

[0038] Fifthly, the present invention provides a non-transitory computer-readable storage medium, characterized in that, when the instructions in the storage medium are executed by a processor of a computing device, the computing device is able to execute the secondary battery discharge state sorting method described above.

[0039] The above scheme involves trickle charging the secondary battery to be sorted while it is in a discharged state, maintaining the battery's charge in the second state of charge. That is, trickle charging introduces only a very small amount of charge, which is insufficient to change the battery's state of charge. However, trickle charging can offset or reduce the voltage hysteresis effect caused by the concentration polarization effect after the secondary battery has finished discharging. This effect causes the voltage to rise first and then gradually fall over time, thus shortening the depolarization time of the secondary battery to be sorted. The depolarization time can be reduced to less than 48 hours. As the depolarization time is shortened, the sorting time of the secondary battery in the discharged state is also shortened. Attached Figure Description

[0040] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0041] Figure 1 A schematic diagram of the lithium-ion battery manufacturing process;

[0042] Figure 2 This is a flowchart of a secondary battery discharge state sorting method provided in an embodiment of the present invention;

[0043] Figure 3 This is a graph showing the voltage change over time after capacity gradation, provided in Embodiment 2 of the present invention.

[0044] Figure 4 A graph showing the voltage change over time after capacity gradation for Comparative Example 1;

[0045] Figure 5 A graph showing the change of voltage over time after capacity gradation for Comparative Example 2;

[0046] Figure 6 This is a schematic diagram of the structure of a computing device provided in an embodiment of the present invention. Detailed Implementation

[0047] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0048] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0049] First, the terminology used in this application will be explained as follows:

[0050] Rechargeable batteries: Batteries that can be repeatedly charged and discharged. Depending on the materials used, they can include, but are not limited to, lithium-ion batteries and sodium-ion batteries; lithium-ion batteries can further include lithium iron phosphate batteries, lithium manganese oxide batteries, lithium cobalt oxide batteries, and ternary lithium batteries. Based on the form of the electrolyte, they can be divided into liquid batteries, semi-solid batteries, and solid batteries. Liquid batteries use liquid electrolytes, solid batteries use solid electrolytes, and semi-solid batteries have an electrolyte that is somewhere between liquid and solid.

[0051] Capacity grading and sorting: During the manufacturing process of secondary batteries, even batteries of the same model and batch can exhibit differences in performance due to fluctuations in process conditions and subtle environmental variations. Capacity grading involves classifying secondary batteries according to their capacity through charge and discharge tests. Sorting involves separating secondary batteries according to their performance and product specifications by inspecting various performance indicators and product grade standards.

[0052] Polarization is classified into ohmic polarization, electrochemical polarization, and concentration polarization. During charging and discharging, redox reactions occur inside the secondary battery. The ion concentration near the electrodes changes due to the electrode reactions. The diffusion rate of ions inside the reactants cannot keep up with this change, resulting in a concentration gradient of reactants near the electrodes. The potential change caused by this concentration gradient is called concentration polarization.

[0053] Depolarization: also known as aging, involves leaving a charged and discharged secondary battery to stand for a certain period of time to at least eliminate the potential change caused by the concentration gradient.

[0054] State of Charge (SOC): The secondary battery is charged to the state of charge (SOC) required by the customer (factory).

[0055] Discharge state: The state of charge of the secondary battery is discharged to the state required by the customer (factory). The second state of charge discussed in this article is the state of charge required by the customer.

[0056] Operating voltage, also known as terminal voltage, refers to the potential difference between the positive and negative terminals of a secondary battery when it is in operation, i.e., when current flows through the circuit. During the discharge phase, as current flows through the battery, it must overcome the resistance caused by the battery's internal resistance, resulting in an ohmic voltage drop and electrode polarization. Therefore, the operating voltage is always lower than the open-circuit voltage. Conversely, during charging, the terminal voltage is always higher than the open-circuit voltage. In other words, polarization results in the terminal voltage being lower than the battery's electromotive force (EMF) during discharge and higher than the EMF during charging.

[0057] Due to polarization, the instantaneous voltage of a secondary battery deviates from the actual voltage during charging and discharging. During charging, the instantaneous voltage is slightly higher than the actual voltage; after charging, the polarization disappears and the voltage drops. During discharging, the instantaneous voltage is slightly lower than the actual voltage; after discharging, the polarization disappears and the voltage rises.

[0058] K-value: refers to the voltage drop of a secondary battery per unit time. It is a physical quantity used to describe the self-discharge rate of the battery cell. It should be noted that the voltage drop here refers to the voltage drop generated by self-discharge of the secondary battery in the open circuit state. This is the battery capacity loss caused by the spontaneous reaction inside the secondary battery.

[0059] like Figure 1 As shown, taking lithium-ion battery manufacturing as an example, its process typically includes main steps such as electrode preparation, cell assembly, electrolyte injection, formation, and capacity grading and sorting. Electrode preparation begins with mixing positive and negative electrode active powder materials, binders, solvents, and conductive agents. This mixture is stirred and dispersed to ensure uniform dispersion of the components, forming a slurry. The slurry is then evenly coated onto a current collector and dried. The electrodes are then rolled and slit to obtain the required positive and negative electrode sheets. Assembly involves welding positive and negative electrode tabs onto the positive and negative electrode sheets, then winding or stacking them together with a separator to form a cell. The cell is then encapsulated in an aluminum, stainless steel, or aluminum-plastic composite film soft packaging shell. The electrolyte injection, formation, and aging process involves injecting electrolyte into the assembled battery after drying. The injected battery is then charged for formation and finally stored at a specific temperature for a period of time for aging. Capacity grading and sorting involves testing the batteries and classifying them into different grades based on indicators such as capacity, internal resistance, thickness, and voltage. Finally, the batteries are packaged and shipped.

[0060] For a rechargeable battery, different methods—charging or discharging—result in either a charged or discharged state. Because these states of charge differ, even rechargeable batteries at the same state of charge will have different voltages. Some customers' Battery Management Systems (BSMs) require the voltage to be collected in the discharged state, while others require it in the charged state. Therefore, to accommodate different customer BSMs and allow customers to directly collect the battery's voltage upon receipt without needing to perform charging or discharging to alter its state of charge, it is necessary to select the appropriate state of charge for shipment based on the customer's BSM requirements.

[0061] In related technologies, when shipping secondary batteries in the discharged state, the voltage hysteresis effect, caused by the concentration polarization effect after discharge, results in a prolonged depolarization time, typically exceeding 72 hours. Since secondary battery sorting must occur after depolarization, the extended sorting time in the discharged state significantly impacts production capacity and delivery time. To address this, the present invention trickles-charges the secondary batteries while they are in the discharged state without altering their state of charge. This trickle-charging counteracts or reduces the voltage hysteresis effect caused by the concentration polarization effect after discharge, thus shortening the depolarization time to less than 48 hours. Consequently, the sorting time in the discharged state is also reduced. The sorting time can be considered to begin at the start of depolarization and end at the classification of secondary batteries using the K-value. Details of this invention are described below.

[0062] like Figure 2 As shown, the secondary battery discharge state sorting method provided in this embodiment of the invention includes the following steps:

[0063] S10: Charge the secondary battery to be sorted to the first state of charge at the first charging rate.

[0064] For example, but not limited to, charging the secondary battery to be sorted to the first state of charge using constant current or constant current and constant voltage at the first charging rate; the first charging rate is 0.5C-1C, and the first state of charge is 30%SOC-90%SOC.

[0065] Generally, it is preferable to perform constant current charging to the first state of charge.

[0066] The first charging rate is 0.5C, 0.55C, 0.58C, 0.6C, 0.63C, 0.66C, 0.7C, 0.75C, 0.8C, 0.81C, 0.9C, 1C, etc.

[0067] The first state of charge is 30%, 32%, 38%, 40%, 45%, 49%, 52%, 57%, 60%, 65%, 70%, 75%, 80%, 85%, and 90%.

[0068] S20: After being left to stand for a first predetermined period of time, the secondary battery to be sorted is discharged to a second state of charge at at least two discharge rates with a gradient decrease, so that the secondary battery to be sorted is in a discharged state.

[0069] The first predetermined duration can be 5 minutes to 30 minutes, for example, but not limited to 5 minutes, 6 minutes, 8 minutes, 10 minutes, 12 minutes, 18 minutes, 21 minutes, 25 minutes, 30 minutes, etc.

[0070] For example, the secondary battery to be sorted can be discharged to the second state of charge by two gradually decreasing discharge rates.

[0071] The two discharge rates are a first discharge rate and a second discharge rate, respectively. The secondary battery to be sorted is discharged at a constant current to the second state of charge using the first discharge rate and the second discharge rate, respectively. The first discharge rate is 0.8C-1C, the second discharge rate is 0.1C-0.3C, and the second state of charge is 25%SOC-60%SOC.

[0072] The first discharge rate is 0.8C, 0.83C, 0.86C, 0.89C, 0.9C, 0.91C, 0.93C, 0.95C, 0.98C, 1C, etc.

[0073] The second discharge rate is 0.1C, 0.11C, 0.13C, 0.15C, 0.18C, 0.2C, 0.22C, 0.26C, 0.3C, etc.

[0074] The second state of charge is 25% SOC, 25% SOC, 30% SOC, 32% SOC, 38% SOC, 40% SOC, 45% SOC, 49% SOC, 52% SOC, 57% SOC, 60% SOC, etc.

[0075] Generally, each state of charge uniquely corresponds to a voltage value, and the state of charge can be determined by detecting the magnitude of the voltage. Due to the existence of errors, and as mentioned earlier, the instantaneous voltage is slightly lower than the actual voltage during discharge, and the voltage will rise after the polarization disappears after discharge. Therefore, in this scheme, after discharging to the second state of charge (corresponding to the cutoff voltage of the second state of charge) at a large discharge rate, it is then discharged to the second state of charge at a small discharge rate. That is, the secondary batteries to be sorted are discharged to the same voltage at a gradually decreasing discharge rate, which can improve the voltage accuracy of the second state of charge.

[0076] In other examples, the secondary battery to be sorted can be discharged to a second state of charge using three progressively decreasing discharge rates.

[0077] The three discharge rates are a first discharge rate, a second discharge rate, and a third discharge rate. The secondary battery to be sorted is discharged at a constant current to the second state of charge using the first discharge rate, the second discharge rate, and the third discharge rate, respectively. The first discharge rate is 0.8C-1C, the second discharge rate is 0.1C-0.3C, the third discharge rate is 0.02C-0.05C, and the second state of charge is 25% SOC-60% SOC.

[0078] The first discharge rate is 0.8C, 0.83C, 0.86C, 0.89C, 0.9C, 0.91C, 0.93C, 0.95C, 0.98C, 1C, etc.

[0079] The second discharge rate is 0.1C, 0.11C, 0.13C, 0.15C, 0.18C, 0.2C, 0.22C, 0.26C, 0.3C, etc.

[0080] The third discharge rate is 0.02C, 0.021C, 0.023C, 0.03C, 0.035C, 0.04C, 0.042C, 0.046C, 0.05C, etc.

[0081] The second state of charge is 25% SOC, 27% SOC, 30% SOC, 32% SOC, 38% SOC, 40% SOC, 45% SOC, 49% SOC, 52% SOC, 57% SOC, 60% SOC, etc.

[0082] For example, for a certain secondary battery, the voltage corresponding to its second state of charge (SOC) of 60% is 3.305V. It can be discharged at a constant current of 1C to 3.305V. Due to the existence of errors, and as mentioned earlier, the instantaneous voltage is slightly lower than the actual voltage during discharge. After the polarization disappears after discharge, the voltage will rise. Therefore, after discharging at a constant current of 1C to 3.305V, it is then discharged at a constant current of 0.2C to 3.305V, and then discharged at a constant current of 0.05C to 3.305V, completing three gradient-decreasing discharge rates to discharge the secondary battery to be sorted to its second state of charge. Discharging the secondary battery to be sorted to the same voltage at three gradient-decreasing discharge rates can further reduce the influence of the internal polarization of the secondary battery on the voltage and improve the voltage accuracy in the second state of charge.

[0083] S30: After a second predetermined period of rest, the secondary battery to be sorted in the discharge state is trickle-charged, and the charge of the secondary battery to be sorted in the discharge state is maintained at the second state of charge.

[0084] The second predetermined duration can be 5 min to 30 min, for example, but not limited to 5 min, 6 min, 8 min, 10 min, 12 min, 18 min, 21 min, 25 min, 30 min, etc.

[0085] For example, the secondary battery to be sorted in the discharged state is charged with a constant current or constant current and constant voltage of 0.08C-0.1C for 1min-2min.

[0086] A constant current method can be preferred for trickle charging.

[0087] The trickle charging rate can be, but is not limited to, 0.08C, 0.085C, 0.09C, 0.093C, 0.1C, etc., and the charging time can be 60s, 65s, 70s, 80s, 85s, 90s, 93s, 96s, 100s, 105s, 110s, 112s, 117s, 120s, etc.

[0088] S40: After trickle charging, the secondary battery to be sorted is left to stand for a third predetermined time. The first open-circuit voltage of the secondary battery to be sorted is obtained. Then, after standing for a fourth predetermined time, the second open-circuit voltage of the secondary battery to be sorted is obtained. Based on the first open-circuit voltage, the second open-circuit voltage, and the fourth predetermined time, the K value of the secondary battery to be sorted is determined. The secondary battery to be sorted is classified based on the K value. The third predetermined time is 12h-48h.

[0089] The third scheduled duration can be, but is not limited to, 12h, 15h, 19h, 20h, 22h, 23h, 27h, 30h, 32h, 39h, 41h, 48h, etc.

[0090] The fourth scheduled duration is 110h-130h; for example, but not limited to, 110h, 112h, 115h, 116h, 117h, 120h, 121h, 123h, 127h, 129h, 130h, etc.

[0091] Wherein, K value: the difference between the first open-circuit voltage and the second open-circuit voltage, divided by the fourth predetermined duration.

[0092] The above scheme involves trickle charging the secondary battery to be sorted while it is in a discharged state, maintaining the battery's charge in the second state of charge. That is, trickle charging introduces only a very small amount of charge, which is insufficient to change the battery's state of charge. However, trickle charging can offset or reduce the voltage hysteresis effect caused by the concentration polarization effect after the secondary battery has finished discharging. This effect causes the voltage to rise first and then gradually fall over time, thus shortening the depolarization time of the secondary battery to be sorted. The depolarization time can be reduced to less than 48 hours. As the depolarization time is shortened, the sorting time of the secondary battery in the discharged state is also shortened.

[0093] Before sorting, there is a capacity grading step. Specifically, before charging the secondary batteries to be sorted to the first state of charge at the first charging rate, the following steps are also included:

[0094] Based on the correspondence between battery type and target charging voltage, the secondary battery to be sorted is charged to the first target voltage at a second charging rate, and then charged to the cutoff at a third charging rate, wherein the second charging rate is greater than the third charging rate.

[0095] For example, the target charging voltage for lithium iron phosphate batteries is 3.6V-3.7V; for ternary lithium batteries, the target charging voltage is 4.2V-4.25V.

[0096] The secondary battery to be sorted is charged to a first target voltage at a second charging rate of constant current and constant voltage or constant current, wherein the second charging rate is 0.33C-1C, for example, but not limited to, 0.33C, 0.4C, 0.45C, 0.47C, 0.5C, 0.52C, 0.56C, 0.7C, 0.8C, 0.9C, or 1C.

[0097] The third charging rate is 0.04C-0.06C, such as, but not limited to, 0.04C, 0.041C, 0.044C, 0.047C, 0.05C, 0.053C, 0.058C, 0.06C, etc.

[0098] If the secondary battery to be sorted is a lithium iron phosphate battery, the first target voltage is any value between 3.6V and 3.7V, and the specific value can be determined according to the actual situation; if the secondary battery to be sorted is a ternary lithium battery, the first target voltage is any value between 4.2V and 4.25V, and the specific value can be determined according to the actual situation.

[0099] The secondary batteries to be sorted are charged using the two different charging rates mentioned above until they are fully charged.

[0100] After a predetermined period of time, the secondary batteries to be sorted are discharged to the second target voltage at a fourth discharge rate, according to the correspondence between battery type and target discharge voltage.

[0101] The fifth preset duration can be 5 min to 30 min, for example, but not limited to 5 min, 6 min, 8 min, 10 min, 12 min, 18 min, 21 min, 25 min, 30 min, etc.

[0102] The secondary battery to be sorted is discharged at a constant current to a second target voltage at a fourth discharge rate of 0.33C-1C, for example, but not limited to, 0.33C, 0.4C, 0.45C, 0.47C, 0.5C, 0.52C, 0.56C, 0.7C, 0.8C, 0.9C, and 1C.

[0103] For example, the target discharge voltage for lithium iron phosphate batteries is 2.0V-2.5V; for ternary lithium batteries, the target discharge voltage is 2.6V-2.7V. The target discharge voltage can be considered the cutoff voltage, meaning that the state of charge (SOC) of the secondary batteries to be sorted is 0% at this point.

[0104] In a second aspect, the present invention provides a secondary battery power regulation device, comprising:

[0105] A charging unit is used to charge the secondary battery to be sorted to a first state of charge at a first charging rate.

[0106] A discharge unit is used to discharge the secondary battery to be sorted to the second state of charge at at least two discharge rates with a gradient decrease after the secondary battery to be sorted has been charged to the first state of charge and left to stand for a first predetermined time, so that the secondary battery to be sorted is in a discharged state.

[0107] The charging unit is further configured to trickle charge the secondary battery to be sorted in the discharge state after it has been discharged to the second state of charge and left to stand for a second predetermined period of time, and to maintain the charge of the secondary battery to be sorted in the discharge state at the second state of charge.

[0108] As an implementation method, the charging unit is used to charge the secondary battery to be sorted in the discharged state at a constant current of 0.08C-0.1C or a constant current and constant voltage for 1min-2min.

[0109] As an implementation method, the charging unit is used to charge the secondary battery to be sorted to the first state of charge at a constant current or constant current and constant voltage at the first charging rate; the first charging rate is 0.5C-1C, and the first state of charge is 30%SOC-90%SOC.

[0110] One possible implementation includes two discharge rates, namely a first discharge rate and a second discharge rate.

[0111] The discharge unit is used to discharge the secondary battery to be sorted, which is charged to the first state of charge, to the second state of charge in sequence at the first discharge rate and the second discharge rate, respectively, and discharge it to the second state of charge at a constant current; the first discharge rate is 0.8C-1C, the second discharge rate is 0.1C-0.3C, and the second state of charge is 25%SOC-60%SOC.

[0112] As an implementation method, it includes three discharge rates, namely a first discharge rate, a second discharge rate, and a third discharge rate;

[0113] The discharge unit is used to discharge the secondary battery to be sorted, which is charged to the first state of charge, to the second state of charge in sequence at the first discharge rate, the second discharge rate, and the third discharge rate, respectively, and discharge it to the second state of charge at a constant current; the first discharge rate is 0.8C-1C, the second discharge rate is 0.1C-0.3C, the third discharge rate is 0.02C-0.05C, and the second state of charge is 25%SOC-60%SOC.

[0114] The aforementioned secondary battery power adjustment device is used to implement at least some steps of the aforementioned secondary battery discharge state sorting method. Its principle and effect are described in the method section above, and will not be repeated here.

[0115] Thirdly, the present invention provides a secondary battery discharge state sorting device, including the above-mentioned secondary battery power adjustment state device;

[0116] It also includes a sorting unit, which is used to obtain the first open-circuit voltage of the secondary battery to be sorted after trickle charging and resting for a third predetermined time, and then obtain the second open-circuit voltage of the secondary battery to be sorted after resting for a fourth predetermined time. Based on the first open-circuit voltage, the second open-circuit voltage and the fourth predetermined time, the K value of the secondary battery to be sorted is determined, and the secondary battery to be sorted is classified based on the K value; the third predetermined time is 12h-48h.

[0117] The aforementioned secondary battery discharge state sorting device is used to implement the aforementioned secondary battery discharge state sorting method. Its principle and effect are described in the method section above, and will not be repeated here.

[0118] Fourthly, the present invention provides a computing device having a computer program stored thereon, the computer program being used to implement the above-described secondary battery discharge state sorting method.

[0119] Fifthly, the present invention provides a non-transitory computer-readable storage medium, characterized in that, when the instructions in the storage medium are executed by a processor of a computing device, the computing device is able to execute the secondary battery discharge state sorting method described above.

[0120] The following is for reference. Figure 6 It shows a schematic diagram of a computing device suitable for implementing the embodiments of this application.

[0121] like Figure 6 As shown, the computing device includes a central processing unit (CPU) 501, which can perform various appropriate actions and processes based on programs stored in read-only memory (ROM) 502 or programs loaded from storage section 508 into random access memory (RAM) 503. The RAM 503 also stores various programs and data required for the operation of the computing device. The CPU 501, ROM 502, and RAM 503 are interconnected via a bus 504. An input / output (I / O) interface 505 is also connected to the bus 504.

[0122] The following components are connected to I / O interface 505: an input section 506 including a keyboard, mouse, etc.; an output section 507 including a cathode ray tube (CRT), liquid crystal display (LCD), etc., and speakers, etc.; a storage section 508 including a hard disk, etc.; and a communication section 509 including a network interface card such as a LAN card, modem, etc. The communication section 509 performs communication processing via a network such as the Internet. A drive 510 is also connected to I / O interface 505 as needed. A removable medium 511, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., is installed on drive 510 as needed so that computer programs read from it can be installed into storage section 508 as needed.

[0123] Specifically, according to the embodiments of the secondary battery discharge state sorting method disclosed in this application, the above references Figure 2 The described process can be implemented as a computer software program. For example, embodiments of the secondary battery discharge state sorting method disclosed in this application include a computer program product comprising a computer program tangibly contained on a machine-readable medium, the computer program containing instructions for performing... Figure 2 The program code for the method. In such an embodiment, the computer program can be downloaded and installed from a network via communication section 509, and / or installed from removable media 511.

[0124] It should be noted that the computer-readable storage medium shown in this invention can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. The computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this application, the computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0125] In this application, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. The computer-readable signal medium may also be any computer-readable storage medium other than a computer-readable storage medium, which can transmit, propagate, or transfer a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable storage medium can be transmitted using any suitable medium, including but not limited to: wireless, wireline, optical fiber, RF, etc., or any suitable combination thereof.

[0126] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the secondary battery discharge state sorting methods of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code, which contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0127] The units or modules described in the embodiments of this application can be implemented in software or hardware. The described units or modules can also be housed in a processor; for example, a processor can be described as including an acquisition model, a first calculation module, and a second calculation module. The names of these units or modules do not necessarily limit the specific unit or module itself. For example, a sorting unit can be described as "for obtaining a first open-circuit voltage of the secondary battery to be sorted after trickle charging and allowing it to rest for a third predetermined time, then obtaining a second open-circuit voltage of the secondary battery to be sorted after a fourth predetermined time, determining a K value of the secondary battery to be sorted based on the first open-circuit voltage, the second open-circuit voltage, and the fourth predetermined time, and classifying the secondary battery to be sorted based on the K value."

[0128] In another aspect, this application also provides a computer-readable storage medium, which may be the computer-readable storage medium included in the aforementioned apparatus in the above embodiments; or it may be a standalone computer-readable storage medium not assembled into the device. The computer-readable storage medium stores one or more programs, which are used by one or more processors to execute the secondary battery discharge state sorting method described in this application.

[0129] The following examples illustrate the effectiveness of this solution using specific embodiments and comparative examples of several secondary battery discharge state sorting methods.

[0130] Example 1

[0131] In this example, the secondary battery discharge state sorting method includes the following steps:

[0132] 1) After the secondary batteries to be sorted are placed in the capacity sorting and sorting equipment, let them stand for 5 minutes;

[0133] 2) Charge the secondary battery to be sorted at a constant current and constant voltage at a second charging rate of 0.33C to the first target voltage of 3.65V, and then charge it at a third charging rate of 0.05C until the current is cut off. At this time, the secondary battery to be sorted is in a fully charged state.

[0134] 3) Let it stand for the fifth predetermined time of 5 minutes;

[0135] 4) Discharge the secondary battery to be sorted at a constant current of 0.33C at the fourth discharge rate to the second target voltage of 2.5V. At this time, the secondary battery to be sorted is in a state of 0 charge.

[0136] 5) Let stand for 5 minutes;

[0137] 6) Charge the secondary battery to be sorted at a constant current of 1C to 80% SOC. The charging time to 80% SOC may vary depending on the secondary battery to be sorted.

[0138] 7) Let stand for the first predetermined time of 5 minutes;

[0139] 8) Discharge the secondary battery to be sorted at a first discharge rate of 1C with a constant current to 3.305V, then discharge it at a second discharge rate of 0.2C with a constant current to 3.305V, and then discharge it at a third discharge rate of 0.05C with a constant current to 3.305V. At this time, the secondary battery to be sorted has a second state of charge of 60% SOC.

[0140] 9) Let stand for the second predetermined time of 5 minutes;

[0141] 10) Trickle charge the secondary batteries to be sorted at a constant current of 0.1C for 1 minute;

[0142] 11) After a third predetermined time of 48 hours, the first open-circuit voltage of the secondary battery to be sorted is obtained. After a fourth predetermined time of 5 days, the second open-circuit voltage of the secondary battery to be sorted is obtained. Based on the first open-circuit voltage, the second open-circuit voltage and the fourth predetermined time, the K value of the secondary battery to be sorted is determined. The secondary battery to be sorted is then classified based on the K value.

[0143] Example 2

[0144] In this example, the secondary battery discharge state sorting method includes the following steps:

[0145] 1) After the secondary batteries to be sorted are placed in the capacity sorting and sorting equipment, let them stand for 10 minutes;

[0146] 2) Charge the secondary battery to be sorted at a constant current and constant voltage at a second charging rate of 0.5C to the first target voltage of 3.65V, and then charge it at a third charging rate of 0.02C until the current is cut off. At this time, the secondary battery to be sorted is fully charged.

[0147] 3) Let it stand for the fifth predetermined time of 10 minutes;

[0148] 4) Discharge the secondary battery to be sorted at a constant current of 0.5C at the fourth discharge rate to the second target voltage of 2.5V. At this time, the secondary battery to be sorted is in a state of 0 charge.

[0149] 5) Let stand for 10 minutes;

[0150] 6) Charge the secondary batteries to be sorted at a constant current rate of 0.5C to 30% SOC (State of Charge).

[0151] 7) Let stand for the first predetermined time of 10 minutes;

[0152] 8) Discharge the secondary battery to be sorted to 3.255V at a constant current rate of 0.8C, then discharge it to 3.255V at a constant current rate of 0.1C, and then discharge it to 3.255V at a constant current rate of 0.03C. At this time, the secondary battery to be sorted has a second state of charge of 25% SOC.

[0153] 9) Let stand for the second predetermined time of 10 minutes;

[0154] 10) Charge the secondary batteries to be sorted at a trickle charge of 0.08C with a constant current for 2 minutes;

[0155] 11) After a third predetermined time of 48 hours, the first open-circuit voltage of the secondary battery to be sorted is obtained. After a fourth predetermined time of 5 days, the second open-circuit voltage of the secondary battery to be sorted is obtained. Based on the first open-circuit voltage, the second open-circuit voltage and the fourth predetermined time, the K value of the secondary battery to be sorted is determined. The secondary battery to be sorted is then classified based on the K value.

[0156] like Figure 3 As shown, two sets of experiments were conducted on this example, namely Example 2-1 and Example 2-2. After step 10) above, the change of voltage over time was observed. The horizontal axis represents time, in days (d), and the vertical axis represents the static voltage value, in volts (V). From Figure 3 It is not difficult to see that after step 10), the voltage value did not rise significantly, but only slightly due to the influence of internal polarization of the battery. The voltage rose from the original theoretical dynamic voltage of 3.255V to slightly higher than 3.27V (3.2703V in Example 2-1 and 3.2702V in Example 2-2). After the rise, the voltage quickly tended to be relatively stable. The voltage reached a relatively stable value after 2 days (48 hours) (generally, when the voltage change rate is less than or equal to 0.03V / s, the voltage can be considered to have reached a relatively stable value). At this time, the relatively stable static voltage is 3.27V. At this time, the first open-circuit voltage of the secondary battery to be sorted can be obtained. It can be seen that after multiple gradient discharges, that is, after step 8), the battery to be sorted is charged with a constant current of 0.08C for 2 minutes. Under the premise of maintaining the discharge state, the internal polarization of the battery can be quickly achieved. Voltage hysteresis was eliminated in each group of experiments. Therefore, the depolarization time can be reduced.

[0157] Example 3

[0158] In this example, the secondary battery discharge state sorting method includes the following steps:

[0159] 1) After the secondary batteries to be sorted are placed in the capacity sorting equipment, let them stand for 30 minutes;

[0160] 2) Charge the secondary battery to be sorted at a constant current and constant voltage at a second charging rate of 1C to the first target voltage of 4.2V, and then charge it at a third charging rate of 0.05C until the current is cut off. At this time, the secondary battery to be sorted is in a fully charged state.

[0161] 3) Let it stand for the fifth predetermined time of 30 minutes;

[0162] 4) Discharge the secondary battery to be sorted at a constant current of 1C at the fourth discharge rate to the second target voltage of 2.7V. At this time, the secondary battery to be sorted is in a state of 0 charge.

[0163] 5) Let stand for 30 minutes;

[0164] 6) Charge the secondary batteries to be sorted at a constant current rate of 1C to 80% SOC (State of Charge).

[0165] 7) Let stand for the first predetermined time of 30 minutes;

[0166] 8) Discharge the secondary battery to be sorted to 3.75V at a constant current rate of 0.9C, then discharge it to 3.75V at a constant current rate of 0.3C, and then discharge it to 3.75V at a constant current rate of 0.02C. At this time, the secondary battery to be sorted has a second state of charge of 50% SOC.

[0167] 9) Let stand for the second predetermined time of 30 minutes;

[0168] 10) Charge the secondary batteries to be sorted at a trickle charge of 0.09C with a constant current for 1 minute;

[0169] 11) After a third predetermined time of 48 hours, the first open-circuit voltage of the secondary battery to be sorted is obtained. After a fourth predetermined time of 5 days, the second open-circuit voltage of the secondary battery to be sorted is obtained. Based on the first open-circuit voltage, the second open-circuit voltage and the fourth predetermined time, the K value of the secondary battery to be sorted is determined. The secondary battery to be sorted is then classified based on the K value.

[0170] Comparative Example 1

[0171] This comparative example illustrates a method for sorting secondary batteries in their charged state, including the following steps:

[0172] 1) After the secondary batteries to be sorted are placed in the capacity sorting and sorting equipment, let them stand for 10 minutes;

[0173] 2) Charge the secondary battery to be sorted at a constant current and constant voltage of 0.5C to 3.65V, and then charge it at 0.02C until the current is cut off. At this time, the secondary battery to be sorted is fully charged.

[0174] 3) Let stand for 10 minutes;

[0175] 4) Discharge the secondary battery to be sorted at a constant current of 1C to 2.5V. At this time, the secondary battery to be sorted is in a state of 0 charge.

[0176] 5) Let stand for 10 minutes;

[0177] 6) Charge the secondary batteries to be sorted at a constant current of 1C to 3.31V (corresponding to 25% SOC);

[0178] 7) After standing for 48 hours, obtain the first open-circuit voltage of the secondary battery to be sorted, and then after standing for another 5 days, obtain the second open-circuit voltage of the secondary battery to be sorted. Based on the first open-circuit voltage, the second open-circuit voltage and the fourth predetermined time, determine the K value of the secondary battery to be sorted, and classify the secondary battery to be sorted based on the K value.

[0179] like Figure 4 As shown, two sets of experiments were conducted on this comparative example, namely Comparative Example 1-1 and Comparative Example 1-2. After step 6) above, the change of voltage over time was observed. The horizontal axis represents time, in days (d), and the vertical axis represents the static voltage value, in volts (V). From Figure 4 As can be seen, the voltage value continues to decrease over time, dropping from the original theoretical dynamic voltage of 3.31V to below 3.30V (3.2996V in Comparative Example 1-1 and 3.2994V in Comparative Example 1-2). The voltage reaches a relatively stable level after 2 days (48 hours), at which point the relatively stable static voltage is 3.2984V. At this point, the first open-circuit voltage of the secondary battery to be sorted can be obtained. Figure 4 It is easy to see that when the secondary battery is in the charging state, the voltage of each test group starts to drop directly after the secondary battery to be sorted has finished charging. Therefore, its depolarization time is relatively short.

[0180] Comparative Example 2

[0181] This comparative example illustrates a method for sorting secondary batteries in their discharged state, including the following steps:

[0182] 1) After the secondary batteries to be sorted are placed in the capacity sorting and sorting equipment, let them stand for 10 minutes;

[0183] 2) Charge the secondary battery to be sorted at a constant current and constant voltage of 0.5C to 3.65V, and then charge it at 0.02C until the current is cut off. At this time, the secondary battery to be sorted is fully charged.

[0184] 3) Let stand for 10 minutes;

[0185] 4) Discharge the secondary battery to be sorted to 2.5V at a constant current of 0.5C. At this time, the secondary battery to be sorted is in a state of 0% charge.

[0186] 5) Let stand for 10 minutes;

[0187] 6) Charge the secondary batteries to be sorted at a constant current of 0.5C to 30% SOC;

[0188] 7) Let stand for 10 minutes;

[0189] 8) Discharge the secondary battery to be sorted at a constant current of 1C to 3.255V, then discharge it at a constant current of 0.2C to 3.255V, and then discharge it at a constant current of 0.05C to 3.255V. At this point, the secondary battery to be sorted has a state of charge (SOC) of 25%.

[0190] 7) After standing for 72 hours, obtain the first open-circuit voltage of the secondary battery to be sorted, and then after standing for another 5 days, obtain the second open-circuit voltage of the secondary battery to be sorted. Based on the first open-circuit voltage, the second open-circuit voltage and the fourth predetermined time, determine the K value of the secondary battery to be sorted, and classify the secondary battery to be sorted based on the K value.

[0191] like Figure 5 As shown, two sets of experiments were conducted on this comparative example, namely Comparative Example 2-1 and Comparative Example 2-2. After step 8) above, the change of voltage over time was observed. The horizontal axis represents time, in days (d), and the vertical axis represents the static voltage value, in volts (V). From Figure 5 As can be seen, the initial voltage value initially increases to a certain extent over time, rising from the original theoretical dynamic voltage of 3.255V to nearly 3.27V (3.2696V in Comparative Example 2-1 and 3.2695V in Comparative Example 2-2). The voltage reaches its maximum value after 2 days (48 hours) and begins to decrease. After 3 days (72 hours), the voltage decrease reaches a relatively stable level, with a relatively stable static voltage of 3.2705V. At this point, the first open-circuit voltage of the secondary battery to be sorted can be obtained. Figure 5 It is easy to see that when the secondary battery is in the discharge state, the voltage of each test group increases first and then slowly decreases after the secondary battery to be sorted has finished the stepped discharge. Therefore, its depolarization time is relatively long.

[0192] The depolarization times of each embodiment and comparative example of this solution, as tested, are detailed in the table below:

[0193]

[0194] The depolarization time is defined as the period from the start of depolarization until the voltage change rate is less than or equal to 0.03V / s. The depolarization time in the table above can be obtained by testing. It is easy to see that the discharge state sorting scheme of this application can significantly shorten the depolarization time compared with the discharge state sorting scheme in the related technology (Comparative Example 2).

[0195] It should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., used above to indicate orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise stated, "a plurality of" means two or more.

[0196] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for sorting discharged state of secondary batteries, characterized in that: The following steps are involved: Charging the secondary battery to be sorted to a first state of charge at a first charging rate; After standing for a first predetermined time, the secondary battery to be sorted is discharged to a second state of charge at at least two discharge rates with a decreasing gradient, so that the secondary battery to be sorted is in a discharged state; After standing for a second predetermined time, trickle charging the discharged secondary battery to be sorted, and maintaining the electric quantity of the discharged secondary battery to be sorted at the second charge state; After the trickle-charged secondary battery to be sorted is left to stand for a third predetermined time, a first open-circuit voltage of the secondary battery to be sorted is obtained, and then after being left to stand for a fourth predetermined time, a second open-circuit voltage of the secondary battery to be sorted is obtained, and based on the first open-circuit voltage, the second open-circuit voltage and the fourth predetermined time, the K value of the secondary battery to be sorted is determined, and the secondary battery to be sorted is classified based on the K value; the third predetermined time is 12h-48h.

2. The method for sorting discharged state of secondary batteries according to claim 1, characterized in that: The trickle charging of the discharged secondary battery to be sorted is specifically: The discharged secondary battery to be sorted is charged at a constant current of 0.08C-0.1C or constant current and constant voltage for 1 min-2 min.

3. The method for separating discharged state of secondary batteries according to claim 1 or 2, characterized in that: The step of charging the to-be-sorted secondary battery to a first state of charge at a first charging rate is specifically as follows: The secondary battery to be sorted is charged to the first state of charge at the first charging rate with constant current or constant current constant voltage; the first charging rate is 0.5C-1C, and the first state of charge is 30% SOC-90% SOC.

4. The method for separating discharged state of secondary batteries according to claim 1 or 2, characterized in that: It includes two discharge rates, which are respectively a first discharge rate and a second discharge rate. The secondary battery to be sorted is discharged at a constant current to the second state of charge at the first discharge rate and the second discharge rate respectively; the first discharge rate is 0.8C-1C, the second discharge rate is 0.1C-0.3C, and the second state of charge is 25% SOC-60% SOC.

5. The method for separating discharged state of secondary batteries according to claim 1 or 2, characterized in that: The method comprises three discharge rates, which are respectively a first discharge rate, a second discharge rate and a third discharge rate, and the secondary battery to be sorted is discharged to the second state of charge at a constant current at the first discharge rate, the second discharge rate and the third discharge rate respectively; the first discharge rate is 0.8C-1C, the second discharge rate is 0.1C-0.3C, the third discharge rate is 0.02C-0.05C, and the second state of charge is 25% SOC-60% SOC.

6. The method for separating discharged state of secondary batteries according to claim 1 or 2, characterized in that: Before charging the secondary battery to be sorted to the first state of charge at the first charging rate, the method further includes: According to the correspondence between the battery type and the target charging voltage, the secondary battery to be sorted is charged to a first target voltage at a second charging rate, and then the secondary battery to be sorted is charged to a cutoff at a third charging rate, wherein the second charging rate is greater than the third charging rate; After standing for a fifth predetermined time, the secondary battery to be sorted is discharged to a second target voltage at a fourth discharge rate according to the correspondence between the battery type and the target discharge voltage.

7. The method for sorting discharged state of secondary batteries according to claim 6, characterized in that: The step of charging the to-be-sorted secondary battery to a first target voltage at a second charging rate is specifically as follows: The secondary battery to be sorted is charged to a first target voltage at a constant current and constant voltage or constant current at a second charging rate, wherein the second charging rate is 0.33C-1C, and the third charging rate is 0.04C-0.06C.

8. The method for sorting discharged state of secondary batteries according to claim 6, characterized in that: The step of discharging the to-be-sorted secondary battery to a second target voltage at a fourth discharge rate is specifically as follows: The secondary battery to be sorted is discharged at a constant current to a second target voltage at a fourth discharge rate, wherein the fourth discharge rate is 0.33C-1C; and the fifth predetermined time length is 5min-30min.

9. The method for sorting discharged state of secondary batteries according to any one of claims 1, 2, 7 and 8, characterized in that: The first predetermined time length and the second predetermined time length are 5 minutes to 30 minutes respectively; the fourth predetermined time length is 110 hours to 130 hours.

10. A secondary battery power state adjustment device, characterized in that: include: A charging unit, used for charging the secondary battery to be sorted to a first state of charge at a first charging rate; a discharge unit, configured to discharge the secondary battery to be sorted to a second state of charge at at least two discharge rates with a decreasing gradient after the secondary battery to be sorted, which is charged to the first state of charge, is left to stand for a first predetermined period of time, so that the secondary battery to be sorted is in a discharged state; The charging unit is further used for trickle charging the discharged secondary battery to be sorted after the discharged secondary battery to be sorted has been left to stand for a second predetermined time, and maintaining the power level of the discharged secondary battery to be sorted at the second charge state.

11. A secondary battery discharge state sorting device, characterized in that: The secondary battery power state adjustment device according to claim 10; It also includes a sorting unit, which is used to obtain the first open circuit voltage of the secondary battery to be sorted after the trickle-charged secondary battery is left to stand for a third predetermined time, and then obtain the second open circuit voltage of the secondary battery to be sorted after the trickle-charged secondary battery is left to stand for a fourth predetermined time, determine the K value of the secondary battery to be sorted based on the first open circuit voltage, the second open circuit voltage and the fourth predetermined time, and classify the secondary battery to be sorted based on the K value; the third predetermined time is 12h-48h.

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