Waste Battery Discharge Process

Abstract

The present invention relates to a process for discharging waste batteries for recycling the waste batteries, and more particularly to a process for verifying the charge state of the waste batteries (used batteries) before reusing or recycling the waste batteries, and discharging the waste batteries in a safe and cost-effective manner.

Description

[Technical field]

[0001] The present invention relates to a process for discharging waste batteries for recycling the waste batteries, and more particularly to a process for verifying the stability, charge state, remaining life, etc. of the waste batteries (used batteries) before reusing or recycling the waste batteries, and discharging the waste batteries in a safe, cost-effective manner. [Background technology]

[0002] Recently, the use of large-capacity lithium-ion batteries is increasing due to the carbon neutral declaration in Korea and the policy to popularize electric vehicles in Korea. Such batteries are widely used in electric vehicles or hybrid vehicles that require large electric capacity, and electric vehicles are attracting the most attention as a means to solve the climate change problem through carbon neutrality. However, due to the use of such a large number of batteries, it is expected that the amount of waste batteries generated from electric vehicles will increase rapidly in the future.

[0003] Meanwhile, if waste vehicle batteries that have been used in environmentally friendly vehicles and then collected are immediately disposed of (for example, through resource recovery), it is predicted that huge disposal costs will be required annually from 2024, and disposal costs will increase explosively from 2031. To partially solve this problem, the waste vehicle batteries should be recycled in other application fields, but recycling waste vehicle batteries without any guarantee, which poses the risk of fire or explosion at any time, is extremely dangerous both technically and socially.

[0004] Therefore, in order to recycle / reuse waste batteries, the energy remaining in the waste batteries, that is, the pre-charged power, needs to be reduced to a certain SOC or lower or completely discharged.

[0005] In the past, to solve these problems, a method was mainly used in which waste batteries were collected from environmentally friendly automobiles, and then the waste batteries were immersed in salt water to discharge the electricity that had been pre-charged in the waste batteries (salt water precipitation method) (Patent Document 1). However, the method of immersing waste batteries in salt water to discharge the electricity required a long time, and a large space was required to immerse waste batteries (heavy and large waste batteries) collected from environmentally friendly automobiles in salt water, which was not cost-effective, and there was also the problem that further treatment of the waste salt water could cause environmental pollution.

[0006] In addition, even if a waste battery is simply discharged using a discharge device that uses electric current, if the discharge is performed without considering the materials (cathode material, anode material, electrolyte, etc.) that make up the battery and without any foresight to erase the energy in the battery, serious loads may be placed on the battery. For example, if a waste battery is simply discharged quickly, a swelling phenomenon due to a side reaction of the electrolyte in the waste battery and a heat generation phenomenon in the battery due to over-discharge may occur, which may cause safety problems such as thermal runaway and ignition, and safety problems may occur due to the open circuit voltage even after discharge.

[0007] Therefore, before reusing or recycling the waste batteries, there is a need for a method for safely and environmentally friendly discharging the pre-charged power, i.e., residual energy, remaining in the waste batteries, so that the waste batteries can be easily reused or recycled. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 10-2019-0018340 Summary of the Invention [Problem to be solved by the invention]

[0009] A first problem to be solved by the present invention is to provide a process for discharging waste batteries, which discharges the power precharged in the waste batteries before the waste batteries are reused or recycled.

[0010] A second problem to be solved by the present invention is to provide a discharge process that can discharge waste batteries in a cost effective, safe and environmentally friendly manner, instead of the conventional salt water precipitation method.

[0011] A third problem to be solved by the present invention is to provide an optimal discharge process taking into consideration the type of waste battery and the design of the materials that make up the electrodes (positive electrode material, negative electrode material, electrolyte, etc.). The object of the present invention is not limited to the object mentioned above, and other objects and advantages of the present invention not mentioned above can be understood from the following description and will be more clearly understood by the embodiments of the present invention. In addition, it should be easily understood that the object and advantages of the present invention can be realized by the means and combinations thereof as set forth in the claims. [Means for solving the problem]

[0012] In order to achieve the above object, a discharge process for a used battery according to an embodiment of the present invention includes: (S100) preparing a waste battery; (S200) discharging the waste battery to a first discharge voltage or a first discharge SOC designated by a connection terminal connected to a power supply terminal of the waste battery; (S300) discharging the waste battery to a second discharge voltage designated by a connection terminal connected to a power supply terminal of the waste battery; (S400) applying a constant voltage when the voltage of the waste battery reaches a specified second discharge voltage; (S500) generating a short circuit in the waste battery to erase residual energy; The present invention provides a process for discharging a waste battery, comprising:

[0013] In one embodiment of the present invention, the discharge in step S200 is performed at a first current magnitude, and the first current magnitude is 0.2C(C-rate) to 5.0C(C-rate), preferably 0.5C(C-rate) to 3.0C(C-rate).

[0014] In one embodiment of the present invention, the first discharge voltage in step S200 is 0.05V to 3.0V, preferably 0.1V to 2.5V based on the single cell. In one embodiment of the present invention, the first discharge SOC in step S200 is between 0% and 50%, preferably between 0% and 30%.

[0015] In one embodiment of the present invention, the discharge in step S300 is performed at a second current magnitude, which is 10% to 50% of the first current magnitude, preferably 20% to 30% of the first current magnitude.

[0016] In one embodiment of the present invention, the second discharge voltage in step S300 is 0V to 0.5V, preferably 0V to 0.1V based on the single cell. In one embodiment of the present invention, the constant voltage applied in step S400 is equal to the second discharge voltage.

[0017] In one embodiment of the present invention, the constant voltage in step S400 is applied until a cutoff current of 0.005C to 0.5C, or 0.01C to 0.1C is measured.

[0018] The above-mentioned solutions are not intended to be exhaustive, and the various features of the present invention and their associated advantages and accomplishments will be more fully understood with reference to the following specific examples. Effect of the Invention

[0019] Conventional methods for discharging residual energy remaining in waste batteries using wet discharge methods such as saltwater precipitation not only require a long time and high costs, but also cause environmental pollution problems such as the disposal of waste saltwater, and have limitations in terms of large-volume, high-capacity discharge. In contrast, the discharge process for waste batteries according to the present invention is a dry method, which is free from the above-mentioned conventional problems and can discharge batteries in a short time. It is environmentally friendly because it does not require the disposal of waste saltwater, and allows waste batteries to be recycled or reused at an effective cost.

[0020] The discharge process for waste batteries according to the present invention can provide a discharge process that comprehensively considers characteristics that may vary depending on the constituent materials and design of the battery, such as battery specification information and information on electrode materials contained in the battery.

[0021] The waste battery discharge process according to the present invention can be utilized as a basic facility for storage, transportation, and reuse of batteries, and is expected to improve the safety of the battery reuse and recycling industry.

[0022] The above-mentioned effects and specific effects of the present invention will be described below with reference to the contents of the embodiment of the invention. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram showing a configuration of a discharge system 100 according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a flow chart illustrating a discharge process of a used battery according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram illustrating a step-by-step discharge process of the present invention using voltage curves according to one embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing an OCV rebound phenomenon that may occur when discharging a battery. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, the principles of the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the drawings and the following description are only for describing preferred embodiments of the present invention, and the present invention is not limited to the drawings and the description.

[0025] Meanwhile, although terms such as "first" or "second" may be used to describe various components, such terms should be construed only for the purpose of distinguishing one component from another component. For example, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component.

[0026] The singular surface includes the plural unless the context clearly dictates otherwise. As used herein, terms such as "comprise" or "have" are intended to specify the presence of stated features, numbers, steps, operations, components, parts, or combinations thereof, and should be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0027] Unless otherwise defined, all terms, including technical or scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which they pertain. Terms defined in commonly used dictionaries should be interpreted to have a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0028] Hereinafter, a discharge process for a waste battery according to an embodiment of the present invention will be described with reference to the accompanying drawings. 1 is a block diagram of a discharging process according to an embodiment of the present invention. Referring to FIG 1, a discharging system 100 according to an embodiment of the present invention includes a charge / discharge unit 110 that adjusts a current through a terminal 140 connected to a waste battery 200, a voltage measurement unit 120, and a memory unit 130.

[0029] The connection terminal of the connection unit 140 is electrically connected to a power terminal of the waste battery, and the connection unit 140 provides an electrical circuit for measuring a voltage value or a current value of the waste battery 200 through the connection terminal, or for charging or discharging the waste battery.

[0030] FIG. 2 is a flow chart illustrating a process of discharging a used battery step by step according to an embodiment of the present invention. Referring to FIG. 2, the present invention includes: (S100) preparing a waste battery; (S200) discharging the waste battery to a first discharge voltage or a first discharge SOC designated by a connection terminal connected to a power supply terminal of the waste battery; (S300) discharging the waste battery to a second discharge voltage designated by a connection terminal connected to a power supply terminal of the waste battery; (S400) applying a constant voltage when the voltage of the waste battery reaches a specified second discharge voltage; (S500) generating a short circuit in the waste battery to erase residual energy; The present invention provides a process for discharging a waste battery, comprising:

[0031] And FIG. 3 is an example of a voltage curve reflecting the discharge process of a waste battery according to an embodiment of the present invention. Meanwhile, in the discharge process of the waste battery according to the present invention, the method of discharging the battery uses a CC-CV (Constant Current-Constant Voltage) method in which the battery is discharged at a constant current up to a specific voltage, and then discharged at a constant voltage until a preset low current is reached, and the present invention is characterized by its detailed process.

[0032] The configuration of the present invention will be described in more detail below. 1. (S100) A step of preparing a waste battery; Before describing the discharge process of the waste battery of the present invention, the waste battery referred to in the present invention means a waste battery for a vehicle that has been used in an environmentally friendly vehicle (e.g., an electric vehicle, a hydrogen vehicle, etc.) and then collected for various reasons (e.g., inspection, repair, expiration of the period, accident, scrapping, etc.), and the battery to be inspected is one of a battery cell, a battery module, or a battery pack.

[0033] In the discharge process of a waste battery according to the present invention, if the waste battery is a battery module, the battery module may include N (N≧2) battery cells and a BMS (Battery Management System) of the battery manufacturer that was installed when the battery manufacturer manufactured the vehicle battery, and may also include a vehicle housing (which may be omitted if the battery is installed in the vehicle without a separate housing) that was prepared when the battery was manufactured or when the battery was installed in the vehicle.

[0034] In the waste battery discharging process according to the present invention, the step of preparing a waste battery in step S100 is a step of collecting waste batteries from the environmentally friendly vehicles, separating the battery manufacturer's BMS and the vehicle casing (optional) from the waste batteries, and then preparing (or storing) a battery module including N battery cells. Meanwhile, the discharge process of a waste battery according to the present invention may include a step of identifying the specifications of the waste battery (S110) after preparing the waste battery, and a step of inspecting the electric flow of the waste battery (S120).

[0035] In detail, the step of identifying the use of the waste battery is a step of determining the type of the waste battery by considering the composition of the waste battery (positive electrode material, negative electrode material, electrolyte, etc.). Since the capacity-voltage curve of the battery, which indicates the discharge characteristics of the battery, is determined by the positive electrode material and the negative electrode material, the specifications of the waste battery should always be taken into consideration in order to set specific conditions of the discharge process such as the first discharge voltage and the second discharge voltage described later.

[0036] Meanwhile, the electric flow inspection (S120) may include an insulation resistance measurement step (S1121), a voltage measurement step (S1122), and an EIS (Electrochemical Impedance Spectroscopy) measurement step (S1123). In this manner, by inspecting the electric flow before discharging the waste battery, the electrical safety of the waste battery undergoing the discharge process can be evaluated, and the SOC (State of Charge) and SOH (State of Health) of the waste battery can be diagnosed. In this case, the SOC and SOH measured in the electric flow inspection step are applied to set the conditions of the subsequent discharge process.

[0037] The waste battery discharge process according to the present invention may further include a step (S110) of identifying the specifications of the waste battery and a step (S130) of setting optimal discharge process conditions based on the results of the step (S120) of inspecting the electrical flow. More specifically, in step S130, discharge conditions such as a first discharge voltage, a second discharge voltage, a constant voltage, a first current, a second current, and a cutoff current, which will be described later, are set.

[0038] 2. (S200) discharging the waste battery to a designated first discharge voltage or a first discharge SOC through a connection terminal connected to a power supply terminal of the waste battery; In the discharge process of the waste battery according to the present invention, the step S200 is a step of discharging the waste battery to a first discharge voltage / first discharge SOC, which is a preset voltage / SOC of the waste battery, through the connection terminal of the waste battery. In the present invention, the step S200 can be changed according to the characteristics of the waste battery, for example, the type of the configuration (electrode material) of the waste battery.

[0039] As described above, the waste vehicle batteries that are used in environmentally friendly automobiles and then collected may not be collected in a completely discharged state because they are collected for various reasons. A charged battery has a risk of fire or explosion if an external impact or stimulus occurs due to the energy stored inside it, and it is very dangerous to recycle it without any guarantee. Therefore, the step S200 is a step of discharging the waste battery through a terminal connected to the waste battery in order to lower the level of the energy charged in the waste battery.

[0040] In the discharge process of the waste battery according to the present invention, the discharge step S200 of the present invention is a step of discharging the waste battery to a first discharge voltage or a first discharge SOC. The step S200 is a step of discharging the battery only to a first discharge voltage or a first discharge SOC, rather than completely discharging the charged energy of the waste battery.

[0041] Meanwhile, in step S200, the first discharge voltage and the first discharge SOC refer to a limit discharge voltage and a limit discharge SOC at which the waste battery no longer exhibits reversible capacity.

[0042] In the present invention, since the step S200 is to discharge to a reversible capacity development region, the waste battery may be recycled / reused after the step S200, i.e., discharging to the first discharge voltage or the first discharge SOC, and therefore may be defined as a "reuse discharge step."

[0043] Meanwhile, in the discharge process of the waste battery according to the present invention, whether or not the reversible capacity is expressed may vary depending on the design of the battery, i.e., the positive and negative electrode materials of the electrodes, so the first discharge voltage or the first discharge SOC may be variably set depending on the positive and negative electrode materials constituting the battery.

[0044] In the discharge process of the waste battery according to the present invention, the first discharge voltage considering the positive and negative electrode materials constituting the waste battery may be 0.05V to 3.0V, preferably 0.1V to 2.5V based on the single cell.

[0045] In the discharge process of the waste battery according to the present invention, the first discharge SOC in step S200 is 0% to 50%, preferably 0% to 30%, and more preferably 5% to 30%.

[0046] Meanwhile, in the present invention, voltage means a potential difference between a positive electrode and a negative electrode, and a value measured based on a single cell, but in a battery module or pack, the voltage standard may be different depending on the battery configuration. For example, in a module or pack in which N (N≧2) single cells are connected in series, the first discharge voltage (single cell voltage*N) may be the discharge voltage.

[0047] In the discharge process of the waste battery according to the present invention, the step S200 may be discharging the waste battery to a first current magnitude through the connection terminal. Here, the magnitude of the first current may be a constant current of 0.2C(C-rate) to 5.0C(C-rate), preferably 0.5C(C-rate) to 3.0C(C-rate).

[0048] Here, C-rate is an abbreviation of current rate, which means a characteristic of a battery that indicates the charge / discharge rate of current according to the capacity of the battery, and the actual unit is [ / h], but the unit [C] is generally used. For example, if the capacity of a battery (the amount of current that can be used in one hour) is 1000mAh and the charge / discharge current is 1A, the C-rate is 1C1A / 1000mAh=1[ / h].

[0049] Meanwhile, in the discharge process of a used battery according to the present invention, the step S200 may further include a step (S210) of checking balance information including a difference in charge voltage between N battery cells provided in the battery through the cell connection terminal after discharging to the first discharge voltage or the first discharge SOC, and a step (S220) of performing a balance check to determine whether the difference in charge voltage between the N battery cells included in the balance information matches a preset effective balance range of charge voltages.

[0050] As described above, by including steps S210 and S220, the voltage variation among the N battery cells constituting the battery module can be checked. In this manner, by checking the voltage variation among the battery cells, the subsequent discharge process of step S300 can be performed more safely.

[0051] 3. (S300) discharging the waste battery to a second discharge voltage designated by a connection terminal connected to a power supply terminal of the waste battery; In the process of discharging the waste battery according to the present invention, the step S300 is a step of discharging the waste battery through the connecting terminal of the waste battery. In detail, the step S300 is a step of discharging the waste battery to a designated voltage or SOC by a connecting terminal of the waste battery.

[0052] In the discharge process of the waste battery according to the present invention, the step S300 is a step of discharging the waste battery discharged only to the first discharge voltage or the first discharge SOC in the step S200 again, and is a step of discharging again to a specified discharge voltage, i.e., the second discharge voltage. In the present invention, the step S300 may be a step of discharging in a region where the reversible capacity is not expressed, for example, a region below SOC 0. Therefore, it may also be defined as an "irreversible discharge step" in the sense that the waste battery is discharged outside the voltage range where the reversible capacity is expressed.

[0053] By discharging the waste battery to the second discharge voltage, most of the energy charged in the waste battery is discharged. Here, step S300 is a step distinct from step S200. Meanwhile, the second discharge voltage in step S300 may be a voltage at which the pre-charged energy can be almost completely discharged, and may be a voltage at which the difference in energy level between the positive electrode and the negative electrode approaches 0. The second discharge voltage according to the present invention may be 0V to 0.1V, preferably 0V to 0.05V based on the single cell.

[0054] In the discharge process of the waste battery according to the present invention, the step S300 may be discharging the waste battery to a second current magnitude through the connection terminal. In this case, the second current may be discharged to a current magnitude of 10% to 50% of the first current, preferably 20% to 30%. In this manner, the magnitude of the second current applied in step S300 is smaller than the magnitude of the first current.

[0055] In the discharge process of the present invention, discharging the waste battery to the first discharge voltage / SOC region and then discharging again to the discharge voltage means discharging the waste battery by electrochemically inducing oxidation / reduction reactions in the waste battery. At this time, as the voltage approaches the second discharge voltage, a stronger oxidation atmosphere is formed at the negative electrode and a stronger reduction atmosphere is formed at the positive electrode. By discharging at a low current in a low voltage region having such characteristics, oxidation / reduction reactions of the electrolyte in the waste battery can be reduced. In addition, by discharging at a slow current from near the second discharge voltage, safety accidents that may occur near the second discharge voltage can be prevented.

[0056] In general, when there are a large number of used batteries and the discharge device is limited, in order to increase the recycling efficiency of the used batteries, a fast discharge current may be applied to the used batteries so that the batteries are in a discharged state, thereby performing a rapid discharge. However, simply rapidly discharging the used batteries in order to increase the recycling efficiency may cause an acceleration of side reactions in the electrolyte due to the rapid discharge, which may cause safety accidents involving swelling and heat generation of the batteries.

[0057] 4. (S400) applying a constant voltage when the voltage of the waste battery reaches a specified second discharge voltage; In the waste battery discharging process according to the present invention, the step S400 is characterized in that, when the voltage of the waste battery reaches a second discharge voltage, a constant voltage is applied to the waste battery.

[0058] In step S400, a constant voltage is applied to induce a fully-discharged waste battery, and therefore, in the present invention, step S400 is defined as a "waste discharge step."

[0059] From the viewpoint of the electrode material of the waste battery, in the case of the negative electrode, the residual lithium ions inserted in the negative electrode material are de-lithiated by applying a constant voltage, and in the case of the positive electrode, the lithium ions are inserted in the positive electrode material. In this way, the residual lithium ions are de-lithiated from the negative electrode, and the waste battery is completely discharged, minimizing the energy level remaining in the waste battery.

[0060] Meanwhile, in the discharge process of the waste battery according to the present invention, the constant voltage applied in step S400 is a voltage where the difference in energy levels between the positive electrode and the negative electrode is close to 0, that is, a voltage approaching 0 V. As the voltage approaches 0 V, lithium ions are more likely to be desorbed from the negative electrode and lithium ions are more likely to be inserted into the positive electrode.

[0061] In the discharge process of the waste battery according to the present invention, the constant voltage is the same as the second discharge voltage, which may be 0V to 0.5V, preferably 0V to 0.1V based on the single cell. In the discharge process of waste batteries according to the present invention, the constant voltage application in step S400 may be performed until a cut-off current magnitude of 0.005C to 0.5C, preferably 0.01C to 0.1C is measured.

[0062] Here, the cut-off current means a current generated by application of a constant voltage, and as the constant voltage is continued to be applied, the magnitude of the generated current gradually decreases as the battery approaches full discharge. At this time, when the magnitude of the cut-off current is within the range of 0.005C to 0.5C, preferably 0.01C to 0.1C, the applied constant voltage is stopped to terminate the discharge. Meanwhile, when a discharge current or voltage is applied to a battery and then the application of the current / voltage is stopped, the overvoltage caused by the applied current / voltage is eliminated and the voltage recovers, which is called OCV rebounding (see Figure 4).

[0063] Here, OCV is an abbreviation of open circuit voltage, which means the voltage between both terminals of the battery when no load is applied. If the OCV is recovered, it means that the internal state of the battery is not electrochemically stable, which may make it difficult to achieve the objective of the present invention, which is to completely discharge the used battery. However, it was confirmed that the degree of OCV rebound was significantly reduced according to the discharge process of the present invention. This is believed to be due to improved electrochemical stability within the battery by discharging using a low current rather than a high current in the voltage region below the first discharge voltage.

[0064] 5. (S500) A step of generating a short circuit in the waste battery to erase residual energy; In the waste battery discharging process according to the present invention, the step S500 is characterized in that it is a step of artificially generating a short circuit in the waste battery to erase residual energy.

[0065] In this case, the step S500 may erase the residual energy by generating an external short circuit with a resistance of 0.1 mΩ to 5 Ω, preferably 30 mΩ to 1 Ω. By short circuiting the waste battery in this manner, the possibility of sparks and fires occurring in the recycling step may be suppressed. Although a preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. In the process of discharging waste batteries, (S100) preparing a discarded battery; (S200) discharging the waste battery to a first discharge voltage or a first discharge SOC designated by a connection terminal connected to a power supply terminal of the waste battery; The discharge process of waste batteries, including

2. The discharge process for a waste battery according to claim 1 , further comprising: (S300) a step of further discharging the waste battery to a second discharge voltage designated by a connection terminal connected to a power supply terminal of the waste battery.

3. The discharge process for a waste battery according to claim 2, further comprising the step of: (S400) applying a constant voltage when the voltage of the waste battery reaches a second discharge voltage.

4. The discharge process for waste batteries according to claim 3, further comprising the step of generating a short circuit in the waste battery to erase residual energy.

5. (S100) After the step of preparing a discarded battery, (S110) Identifying the specifications of the discarded battery; (S120) inspecting the electrical flow of the discarded battery; The discharge process for waste batteries according to claim 1 or 2.

6. The discharge in step S200 is performed at a first current magnitude, and the first current magnitude is 0.2C (C-rate) to 5.0C (C-rate), or 0.5C (C-rate) to 3.0C (C-rate); The discharge process for waste batteries according to claim 1 or 2.

7. 3. The discharge process of waste batteries according to claim 1 or 2, wherein the first discharge voltage in step S200 is 0.05V to 3.0V, or 0.1V to 2.5V based on a single cell.

8. 3. The discharge process for a waste battery according to claim 1 or 2, wherein the first discharge SOC in step S200 is between 0% and 50%, or between 0% and 30%, or between 5% and 30%.

9. 3. The discharge process of waste batteries according to claim 2, wherein the discharge in step S300 is performed with the magnitude of the second current, and the magnitude of the second current is 10% to 50%, or 20% to 30% of the magnitude of the first current.

10. 3. The discharge process of a waste battery according to claim 2, wherein the second discharge voltage in step S300 is 0V to 0.5V, or 0V to 0.1V based on a single cell.

11. The constant voltage applied in step S400 is the same as the second discharge voltage in step S300; The discharge process for waste batteries according to claim 2.

12. 3. The discharge process of waste batteries according to claim 2, wherein the constant voltage in step S400 is applied until a cut-off current magnitude of 0.005C to 0.5C, or 0.01C to 0.1C is measured.

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