Method for fully discharging used battery

Abstract

One embodiment of the present invention provides a method for completely discharging waste batteries using pulse discharge to a level that eliminates the risk of fire or other dangers during the crushing process.

Description

Technology Field

[0001] The present invention relates to a method for completely discharging waste batteries, and more specifically, to a method for completely discharging waste batteries using pulse discharge to a level that eliminates risks such as fire during the crushing process. Background Technology

[0002] As the electric vehicle market grows rapidly, the global battery market is also experiencing explosive growth. With the trend of tightening environmental regulations continuing in countries around the world, the electric vehicle market is expected to continue growing in the future.

[0003] As the demand for lithium-ion batteries increases over time, the issue lies in the management of secondary batteries that are discarded or reprocessed after use. Lithium-ion batteries are not only vulnerable to heat and easily ignite, but they also contain organic solvents and metal oxides, making fire suppression difficult using fire extinguishers or water. Furthermore, a short circuit in a single battery cell can lead to a chain of explosions, potentially escalating the scale of the accident. Currently, ensuring safety in the event that a battery cell splits due to external impact remains challenging.

[0004] One method to safely dispose of the aforementioned used lithium-ion batteries and to supplement the battery shortage is to recycle lithium-based batteries. However, in most cases, to ensure safety during the crushing stage of lithium-based batteries, only completely discharged batteries are required as a prerequisite for processing.

[0005] In the recycling of lithium-ion batteries, conventional methods used to discharge the remaining charge have involved either saltwater discharge or electronic loads. However, the saltwater discharge method is unsuitable for high-voltage modules and packs due to its high electrolysis rate and violent gas release. It also results in increased discharge times and causes problems such as complicating additional separation processes due to contamination of cell contents or reduced purity of the processed materials. Furthermore, toxic gases generated from wastewater and electrolytes during the process can contribute to environmental pollution, making this a method that should be avoided in the future.

[0006] Meanwhile, in the case of the conventional method using electronic loads, there is a problem where the discharge speed slows down as the discharge time increases, and there is a possibility of a large explosion accompanied by a strong spark during the process of transmitting the output of the inverting unit. In addition, even after the battery is discharged to a total voltage of 0V, if the discharge device is removed, the voltage increases again; to prevent this phenomenon, the positive and negative terminals of the battery must be short-circuited. However, some of the multiple cells of the battery may be in a reverse potential state, and in this case, there is a problem that there is a risk of accident due to the short circuit of the positive and negative terminals. Prior art literature

[0007] Republic of Korea Registered Patent No. 10-2245581 The problem to be solved

[0008] The technical problem that the present invention aims to solve is to provide a method for completely discharging waste batteries using pulse discharge to a level where risks such as fire during the crushing process can be eliminated.

[0009] Furthermore, the technical problem that the present invention aims to solve is to provide a method for discharging a lithium-ion battery pack that enables rapid discharge of the internal residual voltage of the lithium-ion battery. Through this, the time required for battery discharge can be reduced compared to conventional discharge methods.

[0010] In addition, another technical objective of the present invention is to provide a discharge method that can prevent the phenomenon of voltage increasing again after the removal of the discharge device without undergoing a dangerous short-circuit process.

[0012] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention belongs from the description below. means of solving the problem

[0013] To achieve the above technical objectives, one embodiment of the present invention provides a method for completely discharging a waste battery.

[0014] The method for completely discharging a waste battery according to one embodiment of the present invention is,

[0015] A discharge step; and a resting step after the discharge step; wherein the discharge step comprises a CC discharge step for discharging the battery to a minimum operating voltage via CC discharge; and a pulse discharge step for discharging the CC-discharged battery via pulse discharge; and wherein the pulse discharge step comprises a discharge current (I peak ) Authorization time (t app ) and rest time (t relax It may be a method for completely discharging waste batteries characterized by proceeding repeatedly with ) as one cycle.

[0017] In addition, according to one embodiment of the present invention, there may be a method for completely discharging a waste battery, characterized in that the discharge step includes a section in which the voltage of the battery drops to 0V or lower during the discharge process.

[0019] In addition, according to one embodiment of the present invention, there may be a method for completely discharging a waste battery characterized in that the total discharge time is within 120 minutes.

[0021] In addition, according to one embodiment of the present invention, the discharge step may be a method for completely discharging a waste battery characterized by maintaining the surface temperature of the battery within 100℃.

[0023] In addition, according to one embodiment of the present invention, there may be a method for completely discharging a waste battery, wherein the discharge step is characterized in that the absolute value of the negative potential reached during discharge is within the maximum operating voltage.

[0025] In addition, according to one embodiment of the present invention, there may be a method for completely discharging a waste battery characterized in that, after the resting step, the OCV is maintained in a range of less than or equal to 5% of the maximum operating voltage.

[0027] In addition, according to one embodiment of the present invention, there may be a method for completely discharging a waste battery characterized in that the pulse discharge step is carried out for 30 minutes to 120 minutes.

[0028] In addition, according to one embodiment of the present invention, the pulse discharge step is,

[0029] Discharge current (I peak ) Authorization time (t app ) and rest time (t relax There may be a method for completely discharging a waste battery characterized by repeating the process 900 to 3000 times with ) as one cycle.

[0031] In addition, according to one embodiment of the present invention, the discharge current (Ipeak ) Authorization time (t app ) and the above rest time (t relax There may be a method for completely discharging a waste battery characterized by each being 0.5 seconds to 2 seconds.

[0033] In addition, according to one embodiment of the present invention, the discharge current (I peak There may be a method for completely discharging a waste battery characterized by the absolute value of ) being 2C to 4C. Effects of the invention

[0034] According to one embodiment of the present invention, a method can be provided to completely discharge waste batteries by utilizing pulse discharge to a level that eliminates the risk of fire or other dangers during the crushing process.

[0035] According to one embodiment of the present invention, the waste battery can be discharged quickly while maintaining the internal temperature of the battery below a certain temperature, and the phenomenon of the voltage increasing again after the discharge device is removed can be prevented without short-circuiting the positive / negative terminals.

[0037] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description of the invention or the claims. Brief explanation of the drawing

[0038] FIG. 1 is a graph showing the current flow over time of a pulse discharge applied in one embodiment of the present invention. FIG. 2 is a graph showing the discharge profile of waste battery No. 1 according to one embodiment of the present invention. FIG. 3 is a graph showing the discharge profile of waste battery No. 2 according to one embodiment of the present invention. FIG. 4 is a graph showing the discharge profile of waste battery No. 3 according to one embodiment of the present invention. FIG. 5 is a graph showing the discharge profile of waste battery No. 4 according to one embodiment of the present invention. FIG. 6 is a graph showing the discharge profile of waste battery No. 5 according to one embodiment of the present invention. FIG. 7 is a graph showing the discharge profile of waste battery No. 6 according to one embodiment of the present invention. FIG. 8 is a photograph of the anode surface and an SEM image of the cell before and after discharge by a discharge method according to one embodiment of the present invention. FIG. 9 is an SEM and EDS image of the separator membrane of a cell before and after discharge by a discharge method according to an embodiment of the present invention. Specific details for implementing the invention

[0039] The present invention will be described below with reference to the attached drawings. However, the present invention may be implemented in various different forms and is therefore not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification have been given similar reference numerals.

[0040] Throughout the specification, when it is stated that a part is "connected (connected, in contact, combined)" with another part, this includes not only cases where they are "directly connected," but also cases where they are "indirectly connected" with other members interposed between them. Furthermore, when it is stated that a part "includes" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but rather allows for the inclusion of additional components.

[0041] The terms used herein are merely for describing specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising” or “having” are intended to indicate the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0043] Embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0044] A method for completely discharging a waste battery according to one embodiment of the present invention is described.

[0045] FIG. 1 is a graph showing the current flow over time of a pulse discharge applied in one embodiment of the present invention.

[0046] Hereinafter, the above embodiment will be described with reference to FIG. 1.

[0048] As an example of the above embodiment, the method comprises: a discharge step; and a resting step after the discharge step; wherein the discharge step comprises: a CC discharge step for discharging the battery by CC discharge to a minimum operating voltage; and a pulse discharge step for discharging the CC-discharged battery by pulse discharge.

[0049] The above pulse discharge step is the discharge current (I peak ) Authorization time (t app ) and rest time (t relax There may be a method for completely discharging waste batteries characterized by proceeding repeatedly with ) as one cycle.

[0051] In the case of the above method for completely discharging waste batteries, the discharge target is a waste battery. However, it is not limited to this and can also be applied to the discharge stage of a general battery.

[0052] In addition, the above-mentioned battery type can be applied to various types of batteries, such as cylindrical, pouch, prismatic, and coin cell batteries.

[0053] In addition, the above battery is a lithium secondary battery and may include a battery using a positive active material such as NCM (Lithium Nickel Cobalt Manganese Oxide), LFP (Lithium Iron Phosphate), NCA (Lithium Cobalt Aluminum Oxide), LMO (Lithium Manganese Oxide), LCO (Lithium Cobalt Oxide).

[0055] In the case of one example of the above embodiment, the internal residual voltage of the lithium-ion battery can be discharged quickly, which has the advantage of reducing the time required for battery discharge compared to conventional discharge methods.

[0056] In addition, in the case of one example of the above embodiment, there is also an advantage in that the phenomenon of voltage increasing again after removal of the discharge device can be prevented without undergoing a dangerous short-circuit process.

[0058] The above Minimum Operating Voltage represents the minimum voltage required for the battery to continue operating. In other words, it is the voltage at which the battery is still operating and capable of providing power.

[0059] The minimum operating voltage of the above battery may vary depending on the type of battery. In the case of lithium-ion batteries used in smartphones, laptops, and electronic devices, the minimum operating voltage is approximately 2.5V to 2.8V. If the voltage drops below the range of the above minimum operating voltage, the battery will not operate stably.

[0061] The above CC discharge (Constant Current Discharge) refers to a method of discharging a battery at a constant current.

[0062] In the case of the above CC discharge, since the current is maintained constant when the voltage changes inside the battery, the battery discharge process can be controlled and accurate results obtained, and

[0063] Since the aforementioned CC discharge discharges the battery with a constant current, it is relatively easy to predict the discharge rate over time, which has the advantage of allowing for accurate measurement of battery capacity or evaluation of battery performance.

[0065] In addition, the above-mentioned pulse discharge is a method of discharging a battery or power supply using high-intensity current pulses occurring at regular intervals for very short periods of time.

[0066] Referring to FIG. 1, the pulse discharge step is a discharge current (I peak ) Authorization time (t app ) and rest time (t relax It can be confirmed that it proceeds repeatedly with ) as one cycle.

[0068] In general, pulse discharge has been used in various applications such as battery life and performance testing of electronic products, flash lighting, radar systems, lasers, and high-power electronic equipment testing,

[0069] In the above embodiment of the present invention, by utilizing the pulse discharge in a method for completely discharging a waste battery, not only can the internal residual voltage of the battery be discharged in a shorter time, but,

[0070] It is possible to provide a method to prevent the self-regeneration effect (Recovery Effect) of a battery, where the voltage increases again after the discharge device is removed, without going through a short-circuit process.

[0072] In the case of the aforementioned pulse discharge, since high-intensity current is delivered only for a short period of time, energy can be used more efficiently than when a battery or power supply is used continuously for a long time, so there is also the advantage of lower energy consumption.

[0074] As an example of the above embodiment, there may be a method for completely discharging a waste battery characterized in that the discharge step includes a section in which the voltage of the battery drops to 0V or lower during the discharge process.

[0076] In order to discharge without rebound to 0V for a short discharge time as in one embodiment of the present invention, a negative potential discharge is required.

[0077] In particular, negative potential discharge is essential to discharge to 0V without rebound during an extremely short discharge time of less than 60 minutes.

[0078] When the above negative potential discharge occurs, copper on the negative electrode is deposited as the positive electrode, causing an internal short circuit, so the OCV can be maintained at 0V without additional short circuit after the discharge.

[0079] In other words, through the principle of causing an internal short circuit by depositing copper from the negative electrode to the positive electrode via the aforementioned negative potential discharge, it is possible to prevent the battery's self-regeneration effect (Recovery Effect), where the voltage increases again after the discharge device is removed, without undergoing a dangerous short-circuit process.

[0081] As an example of the above embodiment, the discharge step may be a method for completely discharging a waste battery characterized by a total discharge time of within 120 minutes.

[0083] The above total discharge time refers to the time required including both the CC discharge step and the pulse discharge step, and

[0084] More preferably, as an example of the above embodiment, there may be a method for completely discharging a waste battery characterized in that the discharge step has a total discharge time of within 100 minutes.

[0085] In addition, more preferably, as an example of the above embodiment, there may be a method for completely discharging a waste battery characterized in that the discharge step has a total discharge time of 80 minutes or less.

[0086] In addition, most preferably, as an example of the above embodiment, there may be a method for completely discharging a waste battery characterized in that the discharge step has a total discharge time of 50 minutes or less.

[0087] In the case of one example of the above embodiment, a method for completely discharging waste batteries in a very short period of time as described above is presented. Through this, not only can the time and cost consumed in large-scale battery disposal operations be saved, but the energy and resources used in said battery disposal operations can also be reduced.

[0088] As described above in the prior art section, generally, when attempting to rapidly discharge a battery, various safety and environmental issues may arise; however, in the case of one example of the above embodiment, a faster method for completely discharging a waste battery can be provided without causing the aforementioned problems.

[0090] As an example of the above embodiment, the discharge step may be a method for completely discharging a waste battery characterized by maintaining the surface temperature of the battery within 100℃.

[0092] Lithium-ion batteries are vulnerable to heat and ignite easily. Furthermore, because they contain organic solvents and metal oxides, fire suppression using fire extinguishers or water is difficult, and a short circuit in a single battery cell can lead to a chain explosion, potentially increasing the scale of the accident.

[0094] As mentioned above, in the case of batteries that are susceptible to heat, safety issues such as fire or explosion may occur if the surface of the battery overheats during the disposal process.

[0095] In particular, if the surface temperature of the battery above becomes 100°C or higher, the separator may shrink and thermal runaway may occur.

[0096] In the case of the above embodiment of the present invention, a safer battery discharge method is provided by maintaining the battery surface temperature within 100℃ during the process of performing the battery discharge step.

[0098] As an example of the above embodiment, there may be a method for completely discharging a waste battery, wherein the discharge step is characterized in that the absolute value of the negative potential reached during discharge is within the maximum operating voltage.

[0100] The above Maximum Operating Voltage refers to the maximum voltage at which the battery can operate safely.

[0101] The above maximum operating voltage varies depending on the chemical characteristics and design of the battery, and generally refers to the maximum voltage that can be reached when the battery is charged.

[0102] If the above maximum operating voltage is exceeded, damage to the battery may occur, and safety issues such as fire or explosion may arise.

[0103] In the case of a lithium-ion battery, the maximum operating voltage has a value of approximately 3.6V to 4.2V.

[0104] Accordingly, in the case of one embodiment of the present invention, in the discharge step, the absolute value of the negative potential reached during battery discharge may be within any one value selected from the range of 3.6V to 4.2V.

[0106] The above negative potential voltage range has a limit for each charger / discharger and cannot rise indefinitely, and implementation may be difficult because the voltage range is determined by the equipment specifications.

[0107] In addition, the larger the absolute value of the aforementioned negative potential, the more severe the copper precipitation occurs, which may cause problems in terms of safety.

[0109] As an example of the above embodiment, there may be a method for completely discharging a waste battery characterized in that, after the resting step, the OCV is maintained in a range of less than or equal to 5% of the maximum operating voltage.

[0111] In the case of a lithium-ion battery, the maximum operating voltage is approximately 3.6V to 4.2V, so the value of 5% of the maximum operating voltage may be 0.18V to 0.21V.

[0112] That is, as an example of the above embodiment, there may be a method for completely discharging a waste battery characterized in that, after the resting step, the OCV is maintained in a range of less than or equal to any one value selected from 0.18V to 0.21V.

[0114] The above Open Circuit Voltage (OCV) represents the voltage measured when no current is flowing in an electrified battery or power supply. The above OCV can provide useful information for identifying or evaluating the state of the battery.

[0115] That is, the above OCV indicates the voltage status of the battery and can be used mainly to determine how much the battery is charged or discharged.

[0117] The battery recovery effect, which is mainly observed in lithium-ion batteries (Li-ion), refers to a phenomenon in which the voltage increases again and the battery's performance is partially restored when the battery is left in a resting state for a certain period of time, after the battery is completely discharged or over-discharged.

[0119] In other words, this means that even after a battery has been completely discharged for disposal, if the battery remains in a resting state for a certain period, the voltage can increase again and return to the state it was in before discharge.

[0121] In one example of the above embodiment, even after the discharged battery has gone through a resting phase, the OCV of the discharged battery can be maintained in a range of 0V to 5% of the maximum operating voltage.

[0122] More preferably, as an example of the above embodiment, there may be a method for completely discharging a waste battery characterized in that, after the resting step, the OCV is maintained at 0V or lower.

[0123] Even if the battery is completely discharged, if the voltage is restored after discharge due to the battery's self-regeneration effect (Recovery Effect), it must be brought to 0V through an additional short circuit to ensure safety. Since proceeding without this process could lead to a fire in the pre-processing section, it is also important to maintain the discharged state.

[0125] Therefore, after the above resting step, the OCV must be maintained within a range of at least 5% of the maximum operating voltage of the battery, and more preferably, the OCV must be maintained at 0V or lower for the battery to be considered to be in a completely discharged state.

[0127] As an example of the above embodiment, there may be a method for completely discharging a waste battery characterized in that the pulse discharge step is carried out for 30 minutes to 120 minutes.

[0128] More preferably, there may be a method for completely discharging a waste battery characterized in that the pulse discharge step is carried out for 30 to 50 minutes.

[0130] As an example of the above embodiment, the pulse discharge step is a discharge current (Ipeak ) Authorization time (t app ) and rest time (t relax There may be a method for completely discharging a waste battery characterized by repeating the process 900 to 3000 times with ) as one cycle.

[0131] More preferably, the pulse discharge step comprises a discharge current (I peak ) Authorization time (t app ) and rest time (t relax There may be a method for completely discharging a waste battery characterized by repeating the process 900 to 1500 times with ) as one cycle.

[0132] At this time, the pulse discharge step, the discharge current (I peak ) Authorization time (t app ) and rest time (t relax When ) is repeated 900 to 1500 times as one cycle, the pulse discharge step proceeds for 30 to 50 minutes.

[0134] As an example of the above embodiment, the discharge current (I peak ) Authorization time (t app ) and the above rest time (t relax There may be a method for completely discharging a waste battery characterized by each being 0.5 seconds to 2 seconds.

[0135] More preferably, the discharge current (I peak ) is 1 second to 1.5 seconds, and the application time (t app There may be a method for completely discharging a waste battery characterized by the duration being 0.5 seconds to 1 second.

[0136] As an example of the above embodiment, the discharge current (I peak There may be a method for completely discharging a waste battery characterized by the absolute value of ) being 2C to 4C.

[0138] In performing the above discharge step, the discharge current (I peak), application time of the discharge current (t app ), and the above rest time (t relax The critical significance of the range values ​​of ) is explained through the following experimental examples.

[0140] Comparative Experiment Example 1. Discharge experiment without pulse discharge.

[0142] The battery was evaluated by manufacturing electrodes with NCM as the positive active material and Graphite as the negative active material, and forming them into coin cells.

[0143] In the case of experiments 1 and 2 below, CC discharge was performed from a fully charged state to the discharge cut-off, and in the case of experiments 3 to 6, CV discharge was performed at the negative potential set in Table 1 below.

[0145] The test was conducted as follows.

[0146] Formation cycles x 2 are performed under charge / discharge conditions of 0.1C / 0.1C.

[0147] Afterwards, a discharge test is conducted under basic charge / discharge conditions of 0.5C / 2C and 4C.

[0148] Subsequently, OCV is measured and data analyzed. (OCV is measured after saturation.)

[0150] Experiment number CC discharge rate Discharge cut-off / CV voltage CV discharge time (min) OCV after discharge is complete 1 2C 2.8V - 3.44V 2 2C 0V - 3.16V 3 2C 0V 90 1.19V 4 2C -0.1V 90 1.15V 5 2C -0.1V 30 1.85V 6 4C -0.1V 90 1.22V

[0152] Referring to Table 1 above, it can be seen that the OCV increased after the battery discharge was completed due to the battery's self-regeneration effect (Recovery Effect).

[0154] Based on the above experimental results, it can be concluded that discharge to a negative potential is required for the OCV to reach 0V after the battery discharge is complete.

[0156] Experimental Example 1. Discharge experiment according to one embodiment of the present invention.

[0158] Unlike the above comparative experimental example 1, in experimental example 1, pulse discharge was used to proceed with the discharge up to the negative potential range.

[0159] The battery was evaluated by manufacturing electrodes with NCM as the positive active material and Graphite as the negative active material, and forming them into coin cells.

[0160] The battery was fully charged and CC discharged to 2.8V Cut-off, and then pulse discharge was performed under the conditions shown in Table 2 below.

[0161] For experiments 1 to 4, the total discharge capacity was set to be the same, and the experiments were conducted with C-rate, current application time, rest time, and cycle as variables.

[0163] Experiment number |I peak |(C-rate) t app (s) t relax (s) Cycles Discharge time (including CC) OCV after discharge is complete 1 2C 1 1 2700 120 0V 2 2C 1 0.5 2700 98 0V 3 4C 1 1 1350 75 0V 4 4C 0.5 1 2700 98 0.17V

[0165] Referring to Table 2 above, it can be confirmed that complete discharge is reached at 0V OCV under conditions 1 to 3, and among them, condition 3 has the shortest discharge time of 75 minutes.

[0167] FIG. 2 is a graph showing the discharge profile of waste battery No. 1 according to one embodiment of the present invention.

[0168] FIG. 3 is a graph showing the discharge profile of waste battery No. 2 according to one embodiment of the present invention.

[0169] FIG. 4 is a graph showing the discharge profile of waste battery No. 3 according to one embodiment of the present invention.

[0170] FIG. 5 is a graph showing the discharge profile of waste battery No. 4 according to one embodiment of the present invention.

[0172] By referring to FIGS. 2 to 5, the battery discharge profile according to each condition of Table 2 can be individually checked.

[0173] The discharge profiles of FIGS. 2 to 5 above are profiles for the part where CC discharge was performed up to 2.8V first, followed by pulse discharge.

[0175] Under the conditions of Table 2 above, pulse discharge conditions with a total discharge time of 75 minutes were confirmed, but additional experiments were conducted according to the conditions of Table 3 below in order to derive a complete discharge condition within 60 minutes by reducing the pulse cycle.

[0177] Experiment number |I peak |(C-rate) t app (s) t relax (s) Cycles Discharge time (including CC) OCV after discharge is complete 5 2C 1 1 900 45 0.16V 6 2C 1.5 0.5 900 49 0V

[0179] FIG. 6 is a graph showing the discharge profile of waste battery No. 5 according to one embodiment of the present invention.

[0180] FIG. 7 is a graph showing the discharge profile of waste battery No. 6 according to one embodiment of the present invention.

[0182] By referring to FIGS. 6 and FIGS. 7, the battery discharge profile according to each condition of Table 3 can be individually verified.

[0183] The discharge profiles of FIGS. 6 and FIGS. 7 above are profiles for the part where CC discharge was performed up to 2.8V first, followed by pulse discharge.

[0185] Referring to Figure 6, the total discharge time was 45 minutes, which is within 60 minutes. However, when measuring the OCV after discharge completion, it was 160mV (0.16V), which is a low OCV, and it can be confirmed that it did not reach complete discharge.

[0187] Referring to Fig. 6, it can be seen that the discharge ends while maintaining a negative potential value during the pulse discharge period, and then the OCV recovers to around 0V during the resting phase.

[0188] On the other hand, referring to Fig. 7, it can be seen that although the voltage has a negative potential value during the pulse discharge section is the same as in Fig. 6, there is a section in the pulse discharge section where the voltage rises again to 0V.

[0189] That is, the above experiment number 6 differs from the above experiment number 5 in that there is a section during the pulse discharge section before the discharge ends in which the voltage recovers to 0V.

[0191] In the case of Experiment No. 6, in order to reach complete discharge, the experiment was conducted by increasing the current application time within the cycle and decreasing the rest time.

[0192] Referring to Fig. 7, although the discharge time increased slightly, the total discharge time was 49 minutes, satisfying the discharge within one hour, and it can be confirmed that the OCV after discharge was maintained at 0V, indicating a completely discharged state.

[0193] The lowest negative voltage under pulse conditions was confirmed to be -3.96V.

[0195] Through this, it can be confirmed that in order to reach a complete discharge when discharging via pulse discharge, a voltage rise section to 0V must be confirmed during the pulse discharge section to reach a complete discharge.

[0197] Experimental Example 2. Decomposition analysis of the cell after complete discharge (OCV 0V after discharge) according to Experimental Example 1 above.

[0199] In Experimental Example 1 above, the cell with an OCV of 0V after discharge was disassembled to check the positive electrode.

[0201] FIG. 8 is a photograph of the anode surface and an SEM image of the cell before and after discharge by a discharge method according to one embodiment of the present invention.

[0202] FIG. 9 is an SEM and EDS image of the separator membrane of a cell before and after discharge by a discharge method according to an embodiment of the present invention.

[0203] Experimental Example 2 above is explained with reference to Figs. 8 and 9.

[0205] Referring to Fig. 8, it can be seen that the electrode surface takes on a copper color after pulse discharge.

[0206] In addition, referring to Fig. 9, through SEM and EDS image analysis of the anode and cathode surfaces of the separator after pulse discharge, it can be confirmed that copper is deposited on the anode surface after complete discharge (OCV 0V).

[0208] The deposition of copper on the anode surface is a phenomenon that occurs during negative potential discharge; when the potential becomes negative, the copper foil, which acts as the cathode current collector, corrodes and oxidizes into copper ions, which then move through the separator to the anode and are deposited on the anode surface.

[0210] When the above negative potential discharge occurs, copper on the negative electrode is deposited as the positive electrode, causing an internal short circuit, so the OCV can be maintained at 0V without additional short circuit after the discharge.

[0211] In other words, through the principle of causing an internal short circuit by depositing copper from the negative electrode to the positive electrode via the aforementioned negative potential discharge, it is possible to prevent the battery's self-regeneration effect (Recovery Effect), where the voltage increases again after the discharge device is removed, without undergoing a dangerous short-circuit process.

[0213] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical spirit or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0214] The scope of the present invention is defined by the claims set forth below, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention.

Claims

Claim 1 A discharge step; and a resting step after the discharge step; wherein the discharge step comprises: a CC discharge step for discharging the battery to a minimum operating voltage via CC discharge; and a pulse discharge step for discharging the CC-discharged battery via pulse discharge; and wherein the pulse discharge step comprises a discharge current (I peak ) Authorization time (t app ) and rest time (t relax A method for completely discharging a waste battery, characterized by being performed repeatedly with ) as one cycle, and the discharge step being performed while maintaining the surface temperature of the battery at 100℃ or lower. Claim 2 A method for completely discharging a waste battery according to claim 1, wherein the discharge step includes a section in which the voltage of the battery drops to 0V or lower during the discharge process. Claim 3 A method for completely discharging a waste battery according to claim 1, wherein the discharge step is characterized by a total discharge time of within 120 minutes. Claim 4 delete Claim 5 A method for completely discharging a waste battery according to claim 1, wherein the discharge step is characterized in that the absolute value of the negative potential reached during discharge is within the maximum operating voltage. Claim 6 A method for completely discharging a waste battery according to claim 1, characterized in that, after the resting step, the OCV is maintained within a range of 5% or less of the maximum operating voltage. Claim 7 A method for completely discharging a waste battery according to claim 1, wherein the pulse discharge step is carried out for 30 minutes to 120 minutes. Claim 8 In claim 1, the pulse discharge step is a discharge current (I peak ) Authorization time (t app ) and rest time (t relax A method for completely discharging a waste battery characterized by repeating the process 900 to 3000 times with ) as one cycle. Claim 9 In claim 1, the discharge current (I peak ) Authorization time (t app ) and the above rest time (t relax A method for completely discharging a waste battery, characterized in that each ) is 0.5 seconds to 2 seconds. Claim 10 In claim 1, the discharge current (I peak A method for completely discharging a waste battery characterized by the absolute value of ) being 2C to 4C.

Images