Device and method for discharging a battery before shipment

Abstract

A battery pre-shipment discharge device according to an embodiment of the present invention can include a charge and discharge unit connected to one or more battery cells to perform charge and discharge on the one or more battery cells; a measurement unit that monitors each of the battery cells and provides related measurement values measured to a control unit; and a control unit that controls the charge and discharge unit to perform a first discharge on the one or more battery cells with a first current value based on a preset discharge capacity, and perform a second discharge on the one or more battery cells with a second current value that changes according to a detailed time interval based on a preset voltage.

Description

Technical Field

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2023-0012727, filed with the Korean Intellectual Property Office on January 31, 2023, and all of the contents disclosed in the document of the Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an apparatus and method for pre-shipment discharge of batteries, and more particularly, to an apparatus and method for performing pre-shipment discharge on one or more battery cells using a plurality of discharge steps.

Background Art

[0003] A secondary battery is a battery that can be reused through charging even after discharge, and can be used as an energy source for small devices such as mobile phones, tablet PCs, and vacuum cleaners, and is also used as a medium to large energy source such as personal mobility, automobiles, and energy storage systems (ESS) for smart grids. Secondary batteries are applied in the form of assemblies such as battery modules in which a number of battery cells are connected in series or parallel according to the requirements of the system, or battery packs in which battery modules are connected in series or parallel.

[0004] Batteries can be broadly classified into cylindrical, pouch, and prismatic types according to their shape. Although such batteries are the same in that they are manufactured by producing a positive electrode plate and a negative electrode plate and then combining a separator and an electrolyte, they can be made into different shaped batteries depending on how they are assembled and packaged.

[0005] Generally, batteries can be manufactured through an electrode process, an assembly process, an activation process, and a pack process. In the activation process among these processes, charging and discharging operations for activating the battery cells are repeatedly performed. Although the charging and discharging operations take a lot of time, the charging and discharging time is proportional to the investment cost for the charging and discharging device, and therefore has a great impact on the profitability of the battery.

[0006] On the other hand, among the charge and discharge operations required during the activation process, pre-shipment charging or pre-shipment discharging is performed immediately before the battery is shipped. In the case of pre-shipment charging, there is a problem of increased charging time, and in the case of pre-shipment discharging, there is a problem of increased voltage variation between cells. Therefore, there is a need for a charge and discharge method that can improve voltage variation and shorten the process time.

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention for solving the above problems is to provide a pre-shipment discharging device for a battery that performs pre-shipment discharging on one or more battery cells.

[0008] Another object of the present invention for solving the above problems is to provide a pre-shipment discharging method for one or more battery cells.

Means for Solving the Problems

[0009] A pre-shipment discharging device for a battery according to an embodiment of the present invention for achieving the above object is a device that performs pre-shipment discharging on one or more battery cells, and includes a charge and discharge unit connected to the one or more battery cells to perform charge and discharge on the one or more battery cells; a measurement unit that monitors each of the battery cells and provides related measurement values measured to a control unit; and a control unit that controls the charge and discharge unit to perform a first discharge on the one or more battery cells with a first current value based on a preset discharge capacity, and perform a second discharge on the one or more battery cells with a second current value that changes according to a detailed time interval based on a preset voltage, and the control unit performs the first discharge and the second discharge before the one or more battery cells are shipped.

[0010] At this time, when the control unit reaches the preset discharge capacity during the first discharge, the control unit can terminate the first discharge.

[0011] Further, when each battery cell reaches the preset voltage during the second discharge, the control unit can terminate the second discharge for each battery cell.

[0012] Here, the first current value may be a value larger than the second current value.

[0013] On the other hand, the second discharge can include three or more detailed discharge steps using the same or different charge-discharge rates.

[0014] Among the three or more detailed discharge steps included in the second discharge, the charge-discharge rate of the detailed discharge step that is temporally last can be set to a value smaller than the charge-discharge rates applied to the remaining detailed discharge steps.

[0015] For example, the second discharge can include a first detailed discharge step of discharging using a first charge-discharge rate; a second detailed discharge step of discharging using a second charge-discharge rate; a third detailed discharge step of discharging using a third charge-discharge rate; a fourth detailed discharge step of discharging using a fourth charge-discharge rate; and a fifth detailed discharge step of discharging using a fifth charge-discharge rate.

[0016] According to one embodiment, the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate are set to the same value, and the fifth charge-discharge rate can be set to a value smaller than the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate.

[0017] According to another embodiment, the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, the fourth charge-discharge rate, and the fifth charge-discharge rate can be set to different values that decrease sequentially. At this time, the third charge-discharge rate can be determined by the first charge-discharge rate and the fifth charge-discharge rate.

[0018] On the one hand, the control unit can fully charge the one or more battery cells before performing the first discharge.

[0019] A pre - shipment discharge method for a battery according to an embodiment of the present invention for achieving the above - mentioned another object is a pre - shipment discharge method for one or more battery cells. It includes a step of performing a first discharge on the one or more battery cells with a first current value based on a preset discharge capacity; and a step of performing a second discharge on the one or more battery cells with a second current value that changes according to a detailed time interval based on a preset voltage. The first discharge and the second discharge are performed before the shipment of the one or more battery cells.

[0020] The step of performing the first discharge can include a step of ending the first discharge when the preset discharge capacity is reached during the first discharge.

[0021] The step of performing the second discharge can include a step of ending the second discharge for each battery cell when the voltage of each battery cell reaches the preset voltage during the second discharge.

[0022] Here, the first current value may be a value larger than the second current value.

[0023] On the one hand, the second discharge can include three or more detailed discharge steps using the same or different charge - discharge rates.

[0024] Among the three or more detailed discharge steps included in the second discharge, the charge - discharge rate of the detailed discharge step that is temporally located last can be set to a value smaller than the charge - discharge rates applied to the remaining detailed discharge steps.

[0025] For example, the second discharge may include: a first detailed discharge step of discharging using a first charge-discharge rate; a second detailed discharge step of discharging using a second charge-discharge rate; a third detailed discharge step of discharging using a third charge-discharge rate; a fourth detailed discharge step of discharging using a fourth charge-discharge rate; and a fifth detailed discharge step of discharging using a fifth charge-discharge rate.

[0026] According to one embodiment, the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate are set to the same value, and the fifth charge-discharge rate can be set to a value smaller than the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate.

[0027] According to another embodiment, the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, the fourth charge-discharge rate, and the fifth charge-discharge rate can be set to different values that decrease sequentially. At this time, the third charge-discharge rate can be determined by the first charge-discharge rate and the fifth charge-discharge rate.

[0028] The pre-shipment discharge method of the battery may further include a step of fully charging the one or more battery cells before performing the first discharge.

Advantages of the Invention

[0029] By using the pre-shipment discharge method of the battery according to the embodiment of the present invention as described above, the voltage variation between battery cells can be improved and the process time required for pre-shipment discharge can be shortened.

[0030] Thereby, it is possible to expect the effects of reducing the investment cost for the charger and improving the power cost of the activation process.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0032] Since the present invention can be subjected to various modifications and can have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, but should be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention. Similar reference numerals are used for similar components while explaining each drawing.

[0033] Terms such as the first, the second, A, B, etc. can be used to describe various components, but the above components should not be limited by the above terms. The above terms are only used for the purpose of distinguishing one component from another. For example, without departing from the scope of the rights of the present invention, the first component can be named the second component, and similarly, the second component can also be named the first component. The term "and / or" includes a combination of a plurality of relatedly described items or an item among a plurality of relatedly described items.

[0034] When it is mentioned that a certain component is "connected to" or "attached to" another component, it should be understood that it may be directly connected or attached to the other component, but there may also be another component in the middle. In contrast, when it is mentioned that a certain component is "directly connected to" or "directly attached to" another component, it should be understood that there is no other component in the middle.

[0035] The terms used in this application are only used to explain a specific embodiment and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "including" or "having" are intended to specify the existence of the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and it should be understood that the existence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof, etc. are not precluded in advance.

[0036] Unless otherwise defined, all terms used herein, including technical or scientific terms, shall have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined as in a commonly used dictionary shall be interpreted to have a meaning consistent with the meaning in the context of the related art, and shall not be interpreted in an idealized or overly formal sense unless clearly defined in the present application.

[0037] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0038] FIG. 1 is a general flowchart of a battery manufacturing process to which the present invention can be applied.

[0039] The battery can be manufactured through an electrode process (S10), an assembly process (S20), an activation process (S30), and a packing process (S40). The battery completed through such processes is shipped in the form of a battery pack (or battery module) including a plurality of battery cells connected in series. The battery pack can be connected to a load via a positive terminal and a negative terminal to perform a charge / discharge operation. The battery pack can be configured by being connected in series / parallel according to the required specifications of the system in which the battery is used.

[0040] More specifically, the electrode process (S10) is a process of making a positive electrode and a negative electrode by mixing an active material, a conductive material, and a binder that constitute the electrode after raw materials are input. The assembly process (S20) is a process of assembling the positive electrode plate and the negative electrode plate manufactured through the electrode process together with a separator to make a finished cell, and the manufacturing order differs depending on the form of the battery (cylindrical, pouch type, square), and the technologies applied also differ for each manufacturer. Also, the activation process (S30) is a process of activating electrical energy and confirming stability. The last packing process (S40) is a process of modularizing the manufactured battery cells and putting them into a pack.

[0041] On one hand, the activation process (S30) is carried out by repeating aging and charge-discharge. In the "aging" process, the battery is stored at room temperature while maintaining a constant temperature and humidity so that the electrolyte soaks into the positive and negative electrodes. Once the electrolyte is dispersed inside the battery and the ion movement between the positive and negative electrodes becomes smooth, the battery is partially charged to activate the cell. At this time, lithium ions all move to the negative electrode, and while the electrolyte is decomposed, a "SEI (Solid Electrolyte Interphase)" layer, which is a thin solid film with low ion conductivity, is formed on the surface of the negative electrode. "SEI" prevents the movement of electrons and allows only lithium ions to pass through, which is an important factor that enhances the safety inside the battery and affects the battery performance and lifespan.

[0042] The charged battery undergoes secondary aging at a high temperature of 40 - 70°C. Through this, SEI can become more stabilized and have a uniform thickness. Gas may be generated inside the battery during the process of aging and charging. At this time, the generated gas undergoes a process of being removed through "Degassing".

[0043] After degassing, aging and charging are further repeated several times. Then, through the process of testing the charge capacity and sorting out defective batteries. Finally, before the battery is shipped, it undergoes a pre-shipment discharge process of discharging at a predetermined charge rate (usually 0.1 - 1C (C-rate)), and then the activation process ends.

[0044] Here, the charge rate (C-rate) is a value indicating the speed at which the battery is charged or discharged, and is also called the charge-discharge rate. The unit of the charge rate uses C (Capacity) which means capacity. The charge rate (C-rate) is the value obtained by dividing the charge-discharge current (A) by the rated capacity value (Ah) of the battery, and the standard value is 1C.

[0045] Figure 2a is a diagram showing the concept of a general 1-step constant current pre-shipment discharge method. Figure 2b shows the current flow used in a general 1-step constant current pre-shipment discharge, and Figure 2c shows the voltage changes of multiple cells during a general 1-step constant current pre-shipment discharge process.

[0046] The pre-shipment discharge method is one of the methods for aligning the shipment SOC (State of Charge), which is the cell charge level at the time of shipment. Among the methods for setting the shipment SOC, it is a method of discharging directly to the shipment SOC without going through a full discharge. Here, SOC (State of Charge; charge rate) represents the charged state of the battery as a percentage [%].

[0047] In the example of FIG. 2a, a pre-shipment discharge method using constant current (CC: Constant Current) is shown. Referring to FIGS. 2a and 2b, after the battery cell is fully charged to 4.xxV, when it is discharged at a constant speed and then reaches a certain amount (discharge capacity) of discharge, the discharge ends. Thereafter, the shipment SOC can be determined by the voltage measured after a certain time (for example, one day later) (3.xxV in the example of FIG. 2).

[0048] At this time, looking at the change in each cell voltage during the discharge process shown in FIG. 2c, it can be confirmed that the deviation between each cell voltage, that is, the voltage variation between cells is significant.

[0049] That is, such a pre-shipment discharge method is a method of discharging only directly to the shipment SOC without going through a full discharge, and although the charge and discharge time can be shortened, there is a quality risk that the voltage variation between cells further increases.

[0050] On the other hand, among the methods for setting the shipment SOC, the pre-shipment charge method of charging the battery cell further to the shipment SOC after full discharge has the disadvantage that the charging time increases because the charging proceeds after full discharge.

[0051] Thus, when following a general pre-shipment discharge method or pre-shipment charge method, there are problems such as long charge and discharge times or quality risks occurring.

[0052] FIG. 3a is a diagram showing the concept of the pre-shipment discharge method according to an embodiment of the present invention.

[0053] Figure 3b shows the current flow used in the pre-shipment discharge method according to an embodiment of the present invention, and Figure 3c shows the voltage changes of a plurality of cells during the pre-shipment discharge process according to an embodiment of the present invention.

[0054] The pre-shipment discharge method according to an embodiment of the present invention can include a discharge process over a plurality of steps. Referring to Figure 3a, the pre-shipment discharge method according to an embodiment of the present invention generally includes the discharge in the first step and the discharge in the second step.

[0055] Referring to Figures 3a and 3b, in the pre-shipment discharge according to an embodiment of the present invention, discharge is performed using a constant current (CC: Constant Current). However, the magnitude of the current applied to the discharge in the first step is different from the magnitude of the current applied to the discharge in the second step.

[0056] More specifically, in the discharge of the first step, after the battery cell is fully charged and discharged at a certain speed (the first current), when it reaches a certain amount (discharge capacity) of discharge (discharge capacity cut-off), the discharge ends. Thereafter, in the discharge of the second step, discharge is performed using a second current having a value lower than the first current, and the discharge in the second step ends when the corresponding cell reaches a certain voltage (voltage cut-off).

[0057] On the other hand, the discharge in the second step includes a number of detailed discharge steps. According to a preferred embodiment of the present invention, the number of detailed discharge steps included in the discharge in the second step may be 3 or 5.

[0058] At this time, looking at the change in the voltage of each cell during the discharge process shown in Figure 3c, it can be confirmed that the voltage variation between cells decreases considerably as the discharge progresses. Also, it can be confirmed that the voltage variation between cells is surely improved at the time when the pre-shipment discharge ends, compared with the case of using the general pre-shipment discharge method in Figure 2c.

[0059] Figure 4 is a block diagram of a pre-shipment discharge device according to an embodiment of the present invention.

[0060] Referring to FIG. 4, the pre-shipment discharge device 100 according to the present invention can be configured to include a control unit 110, a charge and discharge unit 120, and a measurement unit 130.

[0061] The battery cells may be one or more battery cells during the production process, particularly the activation process. The charge and discharge unit 120 can perform charging and discharging operations on one or more battery cells according to the control of the control unit 110. The measurement unit 130 can measure the voltage and discharge capacity of the battery cells while charging and discharging are being performed through the charge and discharge unit 120, and provide the measurement data to the control unit 110.

[0062] The control unit 110 controls the charge and discharge unit 120 to control the charging and discharging operations on the battery cell 10. According to an embodiment of the present invention, the control unit 110 can first fully charge the battery cell (e.g., to 4.xxV). The control unit 110 controls the charge and discharge unit 120 to perform a first discharge based on the discharge capacity of the battery cell input from the measurement unit 130, and then perform a second discharge based on the measured voltage of the battery cell. A certain rest time can be provided between the first discharge and the second discharge.

[0063] At this time, when the control unit 110 reaches a preset reference discharge capacity during the first discharge, the first discharge can be terminated. The discharge capacity can be determined by the discharge current and the discharge time. When the discharge is performed only by the preset reference discharge capacity, the first discharge is completed and terminated.

[0064] Also, when the voltage of each battery cell reaches a preset voltage during the second discharge, the control unit can terminate the second discharge for each battery cell.

[0065] Here, the first current value used for the first discharge is larger than the second current value used for the second discharge. That is, if the first discharge is a discharge using a high rate constant current, it can be said that the second discharge is a discharge using a low rate constant current.

[0066] On the other hand, the second discharge according to an embodiment of the present invention can include three or more detailed discharge steps using the same or different charge-discharge rates. Thereby, the second current applied to the second discharge can have a value that changes according to the detailed time interval.

[0067] At this time, the charge-discharge rate of the detailed discharge step that is temporally last among the detailed discharge steps can be set to a value smaller than the charge-discharge rates applied to the remaining detailed discharge steps.

[0068] When the second discharge includes three detailed discharge steps according to an embodiment, the second discharge can include: a first detailed discharge step of discharging using a first charge-discharge rate; a second detailed discharge step of discharging using a second charge-discharge rate; and a third detailed discharge step of discharging using a third charge-discharge rate.

[0069] Here, the first charge-discharge rate and the second charge-discharge rate can be set to the same value, and the third charge-discharge rate can be set to a value smaller than the first charge-discharge rate and the second charge-discharge rate. Also, the second charge-discharge rate can be set to a value smaller than the first charge-discharge rate.

[0070] When the second discharge includes five detailed discharge steps according to another embodiment, the second discharge can include: a first detailed discharge step of discharging using a first charge-discharge rate; a second detailed discharge step of discharging using a second charge-discharge rate; a third detailed discharge step of discharging using a third charge-discharge rate; a fourth detailed discharge step of discharging using a fourth charge-discharge rate; and a fifth detailed discharge step of discharging using a fifth charge-discharge rate.

[0071] Here, the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate can be set to the same value, and the fifth charge-discharge rate can be set to a value lower than the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate.

[0072] According to another embodiment, the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, the fourth charge-discharge rate, and the fifth charge-discharge rate can be set to different values that sequentially decrease.

[0073] Here, the third charge-discharge rate can be determined by the first charge-discharge rate and the fifth charge-discharge rate. In other words, the current corresponding to the third charge-discharge rate can be determined by the current corresponding to the first charge-discharge rate and the current corresponding to the fifth charge-discharge rate, and can be determined, for example, by the following Equation 1.

[0074]

Equation

[0075] In Equation 1, I3 represents the current corresponding to the third charge-discharge rate, I1 represents the current corresponding to the first charge-discharge rate, and I5 represents the current corresponding to the fifth charge-discharge rate.

[0076] On the other hand, the charge-discharge rate (C-rate) is a value obtained by dividing the charge-discharge current (A) by the rated capacity value (Ah) of the battery, and in the present invention, it can be understood to have the same meaning as the battery discharge speed. Since the rated capacity of the battery is determined, the charge-discharge rate corresponds to the charge-discharge current.

[0077] In this specification, the control unit may be a processor, a controller, an MCU (Main Control Unit), etc., and may also mean a dedicated processor in which the method according to the embodiment of the present invention is performed.

[0078] FIG. 5 shows the operation flow of the pre-shipment discharge method of the battery according to the embodiment of the present invention.

[0079] The pre-shipment discharge method of the battery shown in FIG. 5 can be performed by a pre-shipment discharge device for the battery or a control unit in the pre-shipment discharge device for the battery. In this embodiment, for the sake of convenience of explanation, the operating entity will be described as the control unit, but the operating entity of the pre-shipment discharge method of the battery according to the present invention is not limited thereto.

[0080] The control unit fully charges one or more battery cells during the activation process (S510). Thereafter, the control unit performs a first discharge on the one or more battery cells with a first current value based on a preset discharge capacity (S520). When the preset discharge capacity is reached during the first discharge (S521), the first discharge can be terminated (S522).

[0081] The control unit performs a second discharge on one or more battery cells with a second current value that changes according to a detailed time interval based on a preset voltage after the first discharge (S530). As the discharge progresses, the voltage of each battery cell gradually decreases. However, when the voltage (V cell ) of each battery cell reaches a preset voltage (V final ) during the second discharge (S531), the second discharge for each battery cell can be terminated (S532).

[0082] Here, the first current value may be a value larger than the second current value. That is, if the first discharge is a discharge using a high rate constant current, it can be said that the second discharge is a discharge using a low rate constant current.

[0083] On the other hand, the second discharge according to an embodiment of the present invention can include three or more detailed discharge steps using the same or different charge-discharge rates. Thereby, the second current applied to the second discharge can have a value that changes according to a detailed time interval.

[0084] According to the embodiment, the charge-discharge rate of the detail discharge step that is temporally the last among three or more detail discharge steps included in the second discharge can be set to a value smaller than the charge-discharge rate applied to the remaining detail discharge steps.

[0085] In one embodiment, when the second discharge includes three detail discharge steps, the second discharge can include: a first detail discharge step that discharges using a first charge-discharge rate; a second detail discharge step that discharges using a second charge-discharge rate; and a third detail discharge step that discharges using a third charge-discharge rate.

[0086] Here, the first charge-discharge rate and the second charge-discharge rate can be set to the same value, and the third charge-discharge rate can be set to a value smaller than the first charge-discharge rate and the second charge-discharge rate. Also, the second charge-discharge rate can be set to a value smaller than the first charge-discharge rate.

[0087] In another embodiment, when the second discharge includes five detail discharge steps, the second discharge can include: a first detail discharge step that discharges using a first charge-discharge rate; a second detail discharge step that discharges using a second charge-discharge rate; a third detail discharge step that discharges using a third charge-discharge rate; a fourth detail discharge step that discharges using a fourth charge-discharge rate; and a fifth detail discharge step that discharges using a fifth charge-discharge rate.

[0088] Here, the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate can be set to the same value, and the fifth charge-discharge rate can be set to a value lower than the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate.

[0089] According to another embodiment, the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, the fourth charge-discharge rate, and the fifth charge-discharge rate can be set to different values that decrease sequentially.

[0090] Here, the third charge-discharge rate can be determined by the above-mentioned first charge-discharge rate and the fifth charge-discharge rate. In other words, the current corresponding to the third charge-discharge rate can be determined by the current corresponding to the first charge-discharge rate and the current corresponding to the fifth charge-discharge rate, and can be determined, for example, by the above-mentioned mathematical formula 1.

[0091] FIG. 6 shows the experimental parameters and test results used to derive the optimal pre-shipment discharge process according to the present invention.

[0092] The inventor of the present invention conducted various experiments to determine which factors related to the pre-shipment discharge process affect the discharge time and the voltage standard deviation. The experiment is related to a second discharge process including three or more detailed discharge steps using the same or different charge-discharge rates.

[0093] Referring to FIG. 6, the main experimental factors considered in the experiment mainly include the end C-rate (charge-discharge rate) applied to the last detailed discharge step among a number of detailed discharge steps in the second discharge process, and the intermediate C-rate applied to the intermediate detailed discharge steps, the number of detailed discharge steps, the rest time between the detailed discharge steps, etc. The end C-rate is a factor related to the voltage deviation, and the intermediate C-rate, the number of detailed discharge steps, and the rest time are understood as factors related to the discharge time.

[0094] As the end C-rate, five different values of 1.3C, 1.0C, 0.5C, 0.2C, and 0.1C were applied for experiments. As the intermediate C-rate, two values were applied for experiments. One was the case when an arbitrary value (1.3C, 0.8C) was used, and the other was the case when the value derived using the formula was applied for experiments.

[0095] Here, the formula applied to the intermediate C-rate value may be Equation 1 described above. That is, the intermediate C-rate value can be determined by the C-rate of the detailed discharge step that progresses earliest in time within the second discharge and the C-rate of the detailed discharge step that progresses latest in time within the second discharge.

[0096] Also, the number of detailed discharge steps was set to 2, 3, and 5 to conduct experiments, and the rest times were set to 5 minutes (5 min), 1 minute (1 min), and 0 to conduct experiments.

[0097] As a result of the cell tests, in the case of the end C-rate, the lower the value, the better the voltage deviation improvement was shown, indicating a desirable small characteristic. Also, in the case of the intermediate C-rate, it was found that using the value determined by the C-rate of the detailed discharge step that progresses earliest in time within the second discharge and the C-rate of the detailed discharge step that progresses latest in time within the second discharge is advantageous for shortening the discharge time.

[0098] Furthermore, it was found that the more detailed discharge steps there are, the more advantageous it is in terms of discharge time, and the lower the rest time, the more advantageous it is for shortening the time.

[0099] FIG. 7 shows the test results for many experimental examples with different experimental parameters used to derive the optimal pre-shipment discharge process according to the present invention.

[0100] To understand the performance of various experimental examples (No. 1 to No. 12) made with the combination of favorable experimental factors derived through the experiment of FIG. 6, the test results of deriving the discharge time and the voltage standard deviation value for each experimental example are shown.

[0101] Three or five detailed discharge steps were used, a low value of 0.1 to 0.5 was used for the end C-rate, and a value derived by the formula according to Equation 1 or 1.3C, which is an arbitrary value, was used for the intermediate C-rate.

[0102] The target discharge time was set to less than 70 minutes, and the target voltage standard deviation value was set to less than 1.0. First, candidates that could meet these target conditions were selected.

[0103] As a result of the test, more favorable results can be obtained in the experimental example with 5 detailed discharge steps among the experimental examples shown in FIG. 7. Among them, Case 1 where the charge-discharge rates (corresponding to the discharge current) for detailed discharge steps 1 to 5 are 1.3 / 1.3 / 1.3 / 1.3 / 0.5, and Case 2 where they are 1.3 / 0.7 / 0.4 / 0.2 / 0.1 were found to be the most favorable combinations.

[0104] It can be confirmed that in the case of Case 1, it is more advantageous than Case 2 in terms of the average discharge time, and in the case of Case 2, it is more advantageous than Case 1 in terms of the average voltage deviation.

[0105] Through the tests in FIGS. 6 and 7, it can be confirmed that the charge-discharge rate of the detailed discharge step that is temporally the last among three or more detailed discharge steps included in the second discharge according to the embodiment of the present invention is preferably set to a value smaller than the charge-discharge rates applied to the remaining previous detailed discharge steps.

[0106] Also, when the second discharge includes 5 detailed discharge steps, when the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate are set to the same value, and the fifth charge-discharge rate is set to a value smaller than the first to fourth charge-discharge rates, and when the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, the fourth charge-discharge rate, and the fifth charge-discharge rate are set to different values that decrease sequentially, favorable results can be obtained in terms of the discharge time and the voltage standard deviation.

[0107] FIG. 8 shows the verification results for the optimal pre-shipment discharge method as a preferred embodiment according to the present invention.

[0108] Based on the favorable combination of detailed discharges derived from the experimental examples in FIG. 7, two optimal embodiments as shown in FIG. 8 were derived by utilizing a statistical process optimization solution.

[0109] As evaluation materials for deriving the final two optimal embodiments, the average voltage deviation and the average discharge time were utilized. For the candidate solutions (including five detailed discharge steps, specifying the end C-rate and the intermediate C-rate values), the average voltage deviation compliance value and the average discharge time compliance value were individually calculated, and the final optimal embodiments were derived in a manner of finally deriving the satisfaction value considering the average voltage deviation and the average discharge time comprehensively.

[0110] The final two optimal embodiments as shown in FIG. 8 were derived. The optimal embodiment 1 is the second discharge process carried out at the charging rates of 1.3 / 0.75 / 0.45 / 0.25 / 0.15, and the optimal embodiment 2 was derived as the second discharge process carried out at the charging rates of 1.3 / 1.3 / 1.3 / 1.3 / 0.3.

[0111] For the optimal embodiment 1, the average discharge time was 72 minutes and the average voltage deviation was 0.89, and it was found that further improvement was required in terms of the discharge time. Also, for the optimal embodiment 2, the average discharge time was 61 minutes and the average voltage deviation was 0.94, and it was found that both the target discharge time (less than 70 min) and the target voltage standard deviation (less than 1.0) were satisfied.

[0112] Discharging was performed on one or more battery cells according to the discharge method according to the optimal embodiment 2, and as a result of checking the voltage variation of the battery cells in the tray in the shipped state, it was confirmed to be 0.9 mV. Considering that the voltage variation when using the normal discharge method is 2.4 V, an improvement effect of approximately 63% in voltage variation could be obtained. Also, an effect of shortening the charge-discharge time by 10.4% and an effect of reducing the investment cost by about 3.1 billion won due to this could be obtained, and the power cost of the battery activation process was improved by 10%.

[0113] According to the optimal embodiment 1, the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, the fourth charge-discharge rate, and the fifth charge-discharge rate can be set to different values that sequentially decrease.

[0114] According to the second preferred embodiment, the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate are set to the same value, and the fifth charge-discharge rate can be set to a value lower than the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate.

[0115] To summarize the above, a common feature of the first preferred embodiment and the second preferred embodiment is that the charge-discharge rate of the detailed discharge step that is temporally the last among the detailed discharge steps is set to a value smaller than the charge-discharge rate applied to the remaining previous detailed discharge steps.

[0116] The first preferred embodiment shows better results in terms of voltage deviation, and the second preferred embodiment shows better results in terms of discharge time. Therefore, in a situation where improvement in discharge time is more required than voltage deviation, the second preferred embodiment can be selected, and in a situation where improvement in voltage deviation is more required than discharge time, the first preferred embodiment can be selected to proceed with the battery activation process.

[0117] By using the battery pre-shipment discharge device and method of the present invention as described through the above embodiments, it is possible to improve the voltage variation between battery cells and shorten the process time required for pre-shipment discharge. As a result, it is possible to expect the effects of reducing the investment cost for the charger and improving the power cost of the activation process.

[0118] The operation of the method according to the embodiment of the present invention can be embodied as a computer-readable program or code on a computer-readable recording medium. The computer-readable recording medium includes all types of recording devices in which data that can be read by a computer system is stored. Also, the computer-readable recording medium can be distributed to a computer system connected via a network, and a computer-readable program or code can be stored and executed in a distributed manner.

[0119] Also, a computer-readable recording medium can include a hardware device specially configured to store and execute program instructions, such as a read-only memory (ROM), a random access memory (RAM), a flash memory, etc. The program instructions can include not only machine language code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like.

[0120] Some aspects of the present invention have been described in the context of an apparatus, which can also be illustrated by a corresponding method, where a block or apparatus corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method can be illustrated by corresponding blocks or items or features of a corresponding apparatus. Some or all of the method steps can be performed (or used) by a hardware device such as a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, one or more of the most important method steps can be performed by such a device.

[0121] Although the preferred embodiments of the present invention have been described above, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the present invention described in the following claims.

Description of Reference Numerals

[0122] 100: Pre-discharge device before shipment 110: Control unit 120: Charge and discharge unit 130: Measurement unit

Claims

1. An apparatus for performing pre - shipment discharge on one or more battery cells, comprising: A charge - discharge unit connected to the one or more battery cells for performing charge and discharge on the one or more battery cells; A measurement unit for monitoring and measuring each of the battery cells and providing related measurement values to a control unit; and A control unit for controlling the charge - discharge unit to perform a first discharge on the one or more battery cells with a first current value based on a preset discharge capacity, and to perform a second discharge on the one or more battery cells with a second current value that varies according to a detailed time interval based on a preset voltage, wherein the control unit performs the first discharge and the second discharge on the one or more battery cells before shipment.

2. The control unit: When reaching the preset discharge capacity during the first discharge, ends the first discharge. The apparatus according to claim 1.

3. The control unit: When the voltage of each battery cell reaches the preset voltage during the second discharge, ends the second discharge for each battery cell separately. The apparatus according to claim 1 or 2.

4. The first current value is greater than the second current value. The apparatus according to claim 1.

5. The second discharge includes three or more detailed discharge steps using the same or different charge - discharge rates. The apparatus according to claim 1.

6. Among the three or more detailed discharge steps included in the second discharge, the charge - discharge rate of the detailed discharge step that is located last in time is set to a value smaller than the charge - discharge rates applied to the remaining detailed discharge steps. The apparatus according to claim 5.

7. The second discharge: A first detailed discharge step of discharging using a first charge - discharge rate; A second detailed discharge step of discharging using a second charge - discharge rate; A third detailed discharge step of discharging using a third charge - discharge rate; A fourth detailed discharge step of discharging using a fourth charge - discharge rate; and A fifth detailed discharge step of discharging using a fifth charge - discharge rate. The apparatus according to claim 5.

8. The first charge - discharge rate, the second charge - discharge rate, the third charge - discharge rate, and the fourth charge - discharge rate are set to the same value, The fifth charge - discharge rate is set to a value smaller than the first charge - discharge rate, the second charge - discharge rate, the third charge - discharge rate, and the fourth charge - discharge rate. The apparatus according to claim 7.

9. The device according to claim 7, wherein the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, the fourth charge-discharge rate, and the fifth charge-discharge rate are set to different values that sequentially decrease.

10. The device according to claim 9, wherein the third charge-discharge rate is determined by the first charge-discharge rate and the fifth charge-discharge rate.

11. The control unit The device according to claim 1, wherein the one or more battery cells are fully charged before the first discharge is performed.

12. A method for performing a pre-shipment discharge on one or more battery cells, comprising: performing a first discharge on the one or more battery cells with a first current value based on a preset discharge capacity; and performing a second discharge on the one or more battery cells with a second current value that varies according to a detailed time interval based on a preset voltage, wherein the first discharge and the second discharge are performed before the one or more battery cells are shipped.

13. The step of performing the first discharge The method according to claim 12, comprising ending the first discharge when the preset discharge capacity is reached during the first discharge.

14. The step of performing the second discharge The method according to claim 12 or 13, comprising ending the second discharge for each battery cell when the voltage of each battery cell reaches the preset voltage during the second discharge.

15. The method according to claim 12, wherein the first current value is greater than the second current value.

16. The method according to claim 12, wherein the second discharge includes three or more detailed discharge steps using the same or different charge-discharge rates.

17. The method according to claim 16, wherein the charge-discharge rate of the detailed discharge step that is last in time among the three or more detailed discharge steps included in the second discharge is set to a value smaller than the charge-discharge rates applied to the remaining detailed discharge steps.

18. The second discharge a first detailed discharge step of discharging using a first charge-discharge rate; a second detailed discharge step of discharging using a second charge-discharge rate; a third detailed discharge step of discharging using a third charge-discharge rate; a fourth detailed discharge step of discharging using a fourth charge-discharge rate; and a fifth detailed discharge step of discharging using a fifth charge-discharge rate, The method according to claim 16. The first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate are set to the same value. The method according to claim 18, wherein the fifth charge-discharge rate is set to a value smaller than the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, and the fourth charge-discharge rate. **Claim 20** The method according to claim 18, wherein the first charge-discharge rate, the second charge-discharge rate, the third charge-discharge rate, the fourth charge-discharge rate, and the fifth charge-discharge rate are set to different values that sequentially decrease. **Claim 21** The third charge-discharge rate is determined by the first charge-discharge rate and the fifth charge-discharge rate, according to the method of claim 20. **Claim 22** The method according to claim 12, further comprising the step of fully charging the one or more battery cells before performing the first discharge.

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