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EP-4071883-B1 - DEGRADED CELL MANUFACTURING METHOD AND DEGRADED CELL EVALUATION METHOD

EP4071883B1EP 4071883 B1EP4071883 B1EP 4071883B1EP-4071883-B1

Inventors

  • PARK, SU HAN
  • LEE, JONG HWA
  • KIM, KI WOONG
  • CHUNG, DAE SIK

Dates

Publication Date
20260506
Application Date
20210805

Claims (11)

  1. A method for manufacturing a degenerate cell, the method comprising: preparing a battery cell which has a structure where an electrode assembly, which is generated by lamination of a negative electrode, a positive electrode, and a separator, is accommodated in a battery case, and an electrode lead is drawn out to an outside of the battery case; and precipitating lithium metal on a predetermined region between the negative electrode and the separator by performing charge and discharge under predetermined temperature, pressure and charge and discharge pattern conditions, wherein the charge and discharge is performed under a pressure in a range of 11,77 to 19,61 MPa, wherein the charge and discharge pattern includes constant current (CC)-charging the battery cell until reaching a predetermined voltage, constant voltage (CV)-charging the battery cell having reached the predetermined voltage until reaching a predetermined cutoff current, and constant current (CC)-discharging the CV-charged battery cell, and wherein the pressure is not applied to a lithium-precipitation-desired portion.
  2. The method of claim 1, wherein an initial state of charge (SOC) of the battery cell corresponds to 20 to 50%.
  3. The method of claim 1, wherein the charge and discharge is performed under a temperature in a range of -10 to 0°C.
  4. The method of claim 1, wherein the CC-charging and the CC-discharging are performed at a C-rate in a range of 0.5 to 1.5C.
  5. The method of claim 1, wherein a charge and discharge according to the charge and discharge pattern is performed two or more times.
  6. A method for evaluating a degenerate cell, the method comprising: manufacturing a degenerate cell, wherein manufacturing comprises preparing a battery cell which has a structure where an electrode assembly, which is generated by lamination of a negative electrode, a positive electrode, and a separator, is accommodated in a battery case, and an electrode lead is drawn out to an outside of the battery case; and wherein manufacturing further comprises precipitating lithium metal on a predetermined region between the negative electrode and the separator by performing charge and discharge under predetermined temperature, pressure and charge and discharge pattern conditions, wherein the charge and discharge is performed under a pressure in a range of 11,77 to 19,61 MPa, wherein the charge and discharge pattern includes constant current (CC)-charging the battery cell until reaching a predetermined voltage, constant voltage (CV)-charging the battery cell having reached the predetermined voltage until reaching a predetermined cutoff current, and constant current (CC)-discharging the CV-charged battery cell, and wherein the pressure is not applied to a lithium-precipitation-desired portion; and wherein the method for evaluating a degenerate cell further comprises determining: whether lithium metal has been precipitated in the degenerate cell; a precipitated region of the lithium metal; and a precipitation amount of the lithium metal.
  7. The method of claim 6, wherein the determining of: whether lithium metal has been precipitated in the degenerate cell; the precipitated region of the lithium metal; and the precipitation amount of the lithium metal includes building a database using information on whether lithium metal has been precipitated in the degenerate cell, the precipitated region of the lithium metal, and the precipitation amount of the lithium metal according to the temperature, pressure, and charge and discharge pattern.
  8. The method of claim 6, further comprising performing a safety test for the degenerate cell.
  9. The method of claim 8, wherein the safety test is performed after the degenerate cell is charged to show a predetermined state of charge (SOC).
  10. The method of claim 6, further comprising: preparing a module by connecting the degenerate cells and normal cells, where degeneration has not occurred, in series or in parallel, and performing a safety test for the module.
  11. The method of claim 10, wherein the safety test is performed after the degenerate cell is charged to show a predetermined state of charge (SOC).

Description

[Technical Field] The present invention relates to a method for manufacturing a degenerate cell and a method for evaluating a degenerate cell including the same. [Background Art] US 2019/0267671 A1 relates to the field of battery technology, and more specifically relates to an electrolyte and a secondary lithium battery. JP 2019 192553 A relates to a Li deposition evaluation method for evaluating the deposition of metallic Li that occurs on the surface of a negative electrode plate of a lithium ion secondary battery. JP 2018 156739 A relates to a battery safety evaluation device, a battery control device, a battery safety evaluation method, a program, a control circuit, and a power storage system. Recently, secondary batteries capable of charging and discharging have been widely used as energy sources of wireless mobile devices. In addition, the secondary battery has attracted attention as an energy source of an electric vehicle, a hybrid electric vehicle, etc., which are proposed as a solution for air pollution of existing gasoline vehicles and diesel vehicles using fossil fuel. Therefore, the types of applications using the secondary battery are currently much diversified due to the advantages of the secondary battery, and it is expected that the secondary battery will be applied to many fields and products in the future. Such secondary batteries may be classified into lithium ion batteries, lithium ion polymer batteries, lithium polymer batteries, etc., depending on the composition of the electrode and the electrolyte, and among them, the amount of use of lithium-ion polymer batteries that are less likely to leak electrolyte and are easy to manufacture is on the increase. In general, secondary batteries are classified into cylindrical batteries and prismatic batteries in which an electrode assembly is embedded in a cylindrical or rectangular metal can, depending on the shape of a battery case, and pouch-type batteries in which the electrode assembly is embedded in a pouch-type case of an aluminum laminate sheet. The electrode assembly built into the battery case is composed of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and is a power generating element capable of charging and discharging. The electrode assembly is classified into a jelly-roll type wound with a separator interposed between the positive electrode and the negative electrode which are long sheet-shaped and are coated with active materials, and a stack type in which a plurality of positive electrodes and negative electrodes of a predetermined size are sequentially stacked while a separator is interposed therebetween. Such a secondary battery may be used as one cell unit, a module unit generated by connection of a plurality of cells, or a pack unit generated by connection of a plurality of modules. FIG. 1 is a photograph showing a precipitated lithium metal when a degeneration phenomenon occurs in a battery cell. As shown in FIG. 1, if charge/discharge is repeated by the repeated use of a secondary battery, lithium is precipitated on the negative electrode, and accordingly, performance deterioration of the battery, such as voltage and capacity drop, occurs. In particular, when the battery is used in module and pack units, a difference occurs in the degeneration level between batteries according to the repetition of charge/discharge. Hence, it is necessary to secure the degeneration behavior according to the charge/discharge of the actual cell, and analyze the module or pack unit behavior, not one battery cell behavior. In this regard, Korean Patent No. 10-1293635 discloses an apparatus and method for managing a battery pack reflecting a degeneration degree of a secondary battery cell, capable of minimizing performance deterioration of the battery pack and allowing an electric vehicle having a battery pack mounted thereon to be more safely operated by more effectively generating and controlling various parameters showing characteristics of the battery pack by effectively reflecting the degeneration status of the secondary battery cell, and a battery pack including the method. In addition, the Korean Patent Publication No. 10-2016-0136045 discloses a cell fabrication kit capable of manufacturing an electrode symmetry cell for degeneration analysis of the cell. However, in order to determine the degenerated state, the cell was generally degenerated by repetition of the charge/discharge of the battery like the actual use of the battery, and it was difficult to measure the degenerated form of the battery according to the specific use conditions of the battery, for example, lithium precipitation pattern. Further, since the charge/discharge should be repeated until degeneration of the battery, it takes long time in measurement. Hence, there is a need for a technology capable of recognizing a degeneration form of a battery according to charge/discharge conditions of