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KR-102963178-B1 - Method for setting a cell pressure range of secondary battery module

KR102963178B1KR 102963178 B1KR102963178 B1KR 102963178B1KR-102963178-B1

Abstract

A method for setting a cell pressure range according to the present invention comprises: a first step of determining a minimum pressure for realizing the performance of the secondary battery cell as Pcell_min and a maximum pressure for realizing the performance of the secondary battery cell as Pcell_max based on performance data of the secondary battery cell; and a second step of determining a minimum pressure capable of supporting and fixing a cell stack as Pmodule_min and determining a maximum pressure capable of pressurizing the cell stack without damaging the module housing at the End Of Life (EOL) of the secondary battery cells as Pmodule_max, wherein the intersection range of Pcell_min to Pcell_max and Pmodule_min to Pmodule_max is set as the cell pressure range.

Inventors

  • 하종수
  • 김세호

Assignees

  • 주식회사 엘지에너지솔루션

Dates

Publication Date
20260508
Application Date
20201105

Claims (10)

  1. A method for setting a cell pressure range for secondary battery cells in a secondary battery module, A first step of selecting a secondary battery cell to be applied to a secondary battery module, performing a charge-discharge test while pressurizing the secondary battery cell by increasing the pressure, obtaining data for at least one performance indicator that quantitatively indicates the degree of degradation of the secondary battery cell, and if the data value of the performance indicator that changes according to the magnitude of the pressure satisfies all predetermined criteria values such that the performance of the secondary battery cell is optimized for each performance indicator, determining the minimum pressure as Pcell_min and the maximum pressure as Pcell_max among the pressure range applied to the secondary battery cell; and A second step comprising determining a minimum pressure Pmodule_min to support and fix the cell stack when the secondary battery cells are stacked in one direction to form a cell stack and the cell stack is housed in a module housing, and determining a maximum pressure Pmodule_max to press the cell stack without damaging the module housing at the End Of Life (EOL) of the secondary battery cells, and A method for setting a cell pressure range characterized by setting the intersection range of Pcell_min ~ Pcell_max and Pmodule_min ~ Pmodule_max as the cell pressure range.
  2. In paragraph 1, In the first step above, A method for setting a cell pressure range, characterized in that the above performance indicators include the capacity degradation rate, resistance increase rate, and separator thickness retention rate of the secondary battery cell.
  3. In paragraph 1, The above Pmodule_min is A method for setting a cell pressure range characterized by being a minimum pressure capable of supporting and fixing the cell stack in the Begin Of Life (BOL) of the secondary battery cells.
  4. In paragraph 1, A method for setting a cell pressure range characterized in that the above secondary battery cell is a pouch-type secondary battery cell.
  5. In paragraph 1, The allowable expansion dimensions of the module housing due to swelling of the secondary battery cells are predetermined, and The method further includes a third step of determining Pdimension_min as the minimum pressure at which the cell stack is pressurized during the Begin Of Life (BOL) of the secondary battery cells to manage the dimensions of the module housing within the allowable expansion dimensions, and determining Pdimension_max as the minimum pressure at which the cell stack is pressurized during the End Of Life (EOL) of the secondary battery cells to manage the dimensions of the module housing within the allowable expansion dimensions. The largest value among the above Pcell_min, the above Pmodule_min, and the above Pdimension_min is set as the minimum pressure of the cell pressure range, and A method for setting a cell pressure range, characterized by setting the smaller value between Pcell_min and Pmodule_min as the maximum pressure of the cell pressure range when (Pdimension_max < Pcell_max) & (Pdimension_max < Pmodule_max) are satisfied.
  6. In paragraph 1, The module housing comprises a bottom plate disposed at the bottom of the cell stack; a left side plate and a right side plate that are bent at opposing edge ends of the bottom plate, extend upward, and have a predetermined angle of inclination toward the inside of the module housing. A method for setting a cell pressure range characterized by placing the cell stack between the left side plate and the right side plate and applying pressure.
  7. In paragraph 6, A method for setting a cell pressure range characterized by adjusting the cell pressure range by adjusting the magnitude of the inclination of the left side plate and the right side plate.
  8. In paragraph 1, A method for setting a cell pressure range, characterized in that the module housing is provided with a plate spring inside, and the cell stack is pressed by the plate spring.
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Description

Method for setting a cell pressure range of secondary battery module The present invention relates to a method for manufacturing a secondary battery module, and more specifically, to a method for setting an optimal pressure range for secondary battery cells to optimize performance and structural stability of the secondary battery module. Currently, widely used types of secondary batteries include lithium-ion batteries, lithium-polymer batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries. The operating voltage of these individual secondary battery cells is approximately 2.5V to 4.2V. Therefore, if a higher output voltage is required, multiple secondary battery cells are connected in series, or a battery module is formed by connecting multiple secondary battery cells in series and parallel according to the charge/discharge capacity. When constructing medium to large battery modules by connecting multiple secondary battery cells in series or parallel, a cell stack is formed using a large number of lithium-polymer pouch-type cells, which offer high energy density and ease of stacking. The general method involves housing the cell stack within a module housing for protection and adding electrical components for the electrical connections and voltage measurement of the secondary battery cells to complete the battery module. However, during repeated charging and discharging, lithium-polymer pouch-type rechargeable batteries may experience electrode thickening or gas generation due to the decomposition of the internal electrolyte caused by side reactions. The phenomenon in which the pouch-type battery cell bulges out due to electrode expansion and/or generated gas is called "swelling." For reference, swelling is more significantly attributed to factors resulting from electrode expansion during charging and discharging. If swelling intensifies in pouch-type secondary battery cells, it not only degrades the performance of the secondary battery cells but also alters the external shape of the module housing, which can adversely affect the structural stability of the battery module. According to research to date, it is known that applying strong pressure to stacked secondary battery cells from the initial assembly stage relatively reduces thickness expansion due to swelling. Accordingly, among the technologies to prevent swelling, techniques that disperse expansion forces by inserting pressure pads between secondary battery cells and techniques that apply pressure by tightening the module housing with a strap are known. However, when pressurizing secondary battery cells, the required pressure is determined only empirically, and there is no method for setting the pressure based on qualitative or quantitative data. Therefore, a plan to systematize the cell pressure setting range is required to optimize the performance and structural stability of secondary battery modules. The following drawings attached to this specification illustrate an embodiment of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings. Figure 1 is a graph schematically illustrating the relationship between pressure and the performance of a unit secondary battery cell. FIG. 2 is a diagram illustrating a cell pressure range according to the result of performing the first step of a cell pressure range setting method according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a cell pressure range according to the results of performing the first and second steps of a method for setting a cell pressure range according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating the configuration of a secondary battery module according to one embodiment of the present invention. Figure 5 is a diagram illustrating a method of applying pressure to a cell stack with the module housing of Figure 4. Figure 6 is a diagram illustrating a modified example of the cell stack pressurization method according to Figure 5. FIG. 7 is a diagram illustrating a cell pressure range according to the results of performing the first, second, and third steps of a cell pressure range setting method according to an embodiment of the present invention. FIG. 8 is a flowchart illustrating a secondary battery module design method applying the cell pressure setting method according to the present invention. Since embodiments of the present invention are provided to more fully explain the invention to those skilled in the art, the shapes and dimensions of the components in the drawings may be exaggerated, omitted, or schematically depicted for clearer explanation. Accordingly, the dimensions or proportions of each component do not entirely reflect actual dimensions or