KR20220015008A - Case Capable Of Uniform Pressure For Solid State Battery And Battery Comprising The Same - Google Patents

Abstract

Disclosed is an all-solid-state secondary battery having improved interfacial properties by uniform pressurization. The present invention provides the all-solid-state secondary battery including: an all-solid-state battery cell in which a positive electrode, a negative electrode and a solid electrolyte are stacked; a rigid case surrounding the all-solid-state battery cell; and an elastic buffer layer interposed between the all-solid-state battery cell and the rigid case.

Description

Uniform pressure case for all-solid-state battery and all-solid-state secondary battery comprising same

The present invention relates to an all-solid-state battery, and more particularly, to an all-solid-state secondary battery having a case capable of applying uniform pressure to the all-solid-state battery.

Lithium secondary batteries using conventional liquid electrolytes have little need for external uniform pressurization. Therefore, as the case of all-solid-state secondary batteries, metal cans (aluminum) or flame-retardant plastic materials have been widely used as they are designed to minimize weight and facilitate processing. However, the conventional case as shown in FIG. 1 is difficult to withstand the positive pressure of the internal electrode material and has poor heat dissipation characteristics, so improvement of thermal stability is required.

In particular, since the all-solid-state battery uses a solid electrolyte, it is very important to form a close interface between the solid electrolyte membrane and the positive electrode, and conventionally, a pellet-type torque cell as shown in FIG. 2 is mainly used. It is being used as a test cellot in the experimental stage with a diameter of less than 2 cm.

However, in order to apply all-solid-state batteries to automobile batteries or ESS batteries, large-area electrode stacking and stacking are essential. necessary.

(1) Journal of Power Sources, Volume 248, 15 February 2014, Pages 943-950

In order to solve the problems of the prior art, an object of the present invention is to provide an all-solid-state secondary battery having excellent performance by forming a close interface.

In addition, the present invention provides a case that can apply uniform pressure from the outside of a large-area or multi-stacked all-solid-state battery, rather than a pellet-pressurized all-solid-state battery, thereby minimizing the high resistance at the interface between the separator and the electrode. An object of the present invention is to provide an all-solid-state secondary battery.

In order to achieve the above technical object, the present invention provides an all-solid-state battery cell in which a positive electrode, a negative electrode and a solid electrolyte are stacked; a rigid case surrounding the all-solid-state battery cell; and an elastic buffer layer interposed between the all-solid-state battery cell and the rigid case.

According to the present invention, it is possible to provide an all-solid-state battery having excellent performance by forming a close interface. In addition, an all-solid-state secondary battery that minimizes the high resistance at the interface between the separator and the electrode by providing a case that can apply uniform pressure outside of a large-area or multi-stacked all-solid-state battery rather than a pellet-pressurized all-solid-state battery be able to provide

1 is a schematic diagram showing the structure of a conventional secondary battery.
2 is a cross-sectional view showing the structure of a conventional pellet-type torque cell.
3 is a schematic diagram showing a pressurization structure of an all-solid-state secondary battery according to an embodiment of the present invention.
4 is a schematic diagram showing a pressurization structure of an all-solid-state secondary battery according to another embodiment of the present invention.
5 is a graph showing the results of measuring the electrochemical properties of the all-solid-state secondary battery manufactured according to an embodiment of the present invention.
6 is a graph showing the results of measuring the electrochemical properties of the all-solid-state secondary battery prepared according to the comparative example of the present invention.

The present invention will be described in detail below with reference to the drawings.

All-solid-state secondary batteries require a condition in which compressive stress is applied or maintained from the outside of the all-solid-state battery in order to minimize the electrochemical reaction resistance that occurs at the interface between the electrolyte and the electrode and at the interface between the separator and the electrode. In particular, as the cycle progresses, the volume expansion and contraction of the all-solid-state battery occurs according to charging and discharging, and an external pressurizing case capable of actively controlling the corresponding pressure is required.

Therefore, in the present invention, a case capable of applying a uniform pressure from the outside of the all-solid-state battery is proposed, and a method for minimizing the high resistance at the interface between the separator and the electrode is to be presented.

In addition, in order to improve the thermal safety characteristics of the battery by exposing the battery to high temperatures or by self-heating of the battery by giving heat resistance characteristics as a material of the case, the case can use a heat dissipation material capable of discharging internal heat well.

Existing interfacial resistance reduction technology is difficult to secure fundamental thermal stability by applying a semi-solid hybrid electrolyte matrix to which a liquid electrolyte is applied. In order to do this, a method of artificially coating an artificial SEI layer on the surface of the active material is proposed. can't be

3 is a schematic diagram showing a pressurization structure of an all-solid-state secondary battery according to an embodiment of the present invention.

Referring to FIG. 3 , the pressing jig includes two upper and lower plates and a shaft supporting the plate. An all-solid-state battery cell and an elastic buffer layer are inserted between the plates of the jig. The elastic buffer layer may consist of a plurality of sheets, each sheet preferably being an elastic body.

4 is a schematic diagram showing a pressurization structure of an all-solid-state secondary battery according to another embodiment of the present invention.

A rigid case (jig) surrounds the perimeter of the all-solid-state battery cell. An all-solid-state battery cell stack is positioned inside the rigid case. The all-solid-state battery cell stack may be a structure in which a positive electrode, a negative electrode, and a solid electrolyte are stacked. An elastic buffer layer is disposed in a space between the all-solid-state battery cell stack and the rigid jig. The elastic buffer layer may be an elastic material such as rubber.

The elastic buffer layer and the rigid jig may apply a constant pressure to the all-solid-state battery cell. The rigid jig may be formed of a rigid material that is elastically deformed within a pressing force range of the elastic buffer layer.

In this way, a buffer sheet that can provide mechanical buffering is placed on both sides of the manufactured pouch cell, and the case is covered with a metal plate having a heat dissipation function and a pressure resistance function on the outside to form an interface between the electrodes closely, thereby lowering the resistance and cell performance. can improve

<Example>

A solid electrolyte slurry dispersed in a solvent was applied to prepare an all-solid-state battery separator.

The solid electrolyte composite separator is composed of a polymer composite membrane or green sheet composed of a solid electrolyte (sulfide-based electrolyte and oxide-based electrolyte) and a binder (PEO, PEP-NMB, NBR, etc.) Non-woven membranes and the like may be applied.

The all-solid-state battery positive electrode layer was prepared by adding positive electrode active material, binder, and conductive powder to NMP (N-Methyl-2-pyrrolidone) solvent and stirring to prepare a slurry, which was then applied to an aluminum current collector.

The all-solid-state battery anode layer was prepared by dispersing lithium metal, a metal and carbon composite, and graphite in a binder and a solvent at an appropriate ratio, and applying it to the current collector.

The all-solid-state battery cell manufacturing method was prepared by sequentially stacking a positive electrode layer, a solid electrolyte separator layer, and a negative electrode layer, or coating and drying a positive electrode layer slurry, a solid electrolyte layer slurry, and a negative electrode layer slurry in order.

After vacuum sealing the stacked anode layer, solid electrolyte separator layer, and cathode layer in a pouch, uniaxial, biaxial, or isotropic pressure is applied to form a close interface or between electrode materials.

The uniform pressurization case places one or more buffer sheets on both sides in the direction of the cell, and the size of the buffer sheet is equal to or larger than the cell. The uniform pressurization case has a larger area than the buffer sheet and is located outside the buffer sheet. Because pressure is applied to the cell in the plane direction, a material with pressure-resistant performance must be used, and a material with a heat dissipation function is used to improve thermal stability.

The shape of the uniform pressurization case may be a form in which two plate-shaped bars are tightened with bolts and nuts (FIG. 3) or a case type (FIG. 4), but the structure of FIG. 3 is adopted in this embodiment. The cell specifications are shown in Table 1 below.

part standard weight note anode 25*25 mm ² 0.6680 g 6.0 mA/cm ² anode foil 25*25 mm ² 0.0223 g - Separator/C-M 30*30 mm ² 0.3157 g both sides cathode foil 30*30 mm ² 0.085 g pouch - 0.7072 g other parts - 0.1360 g Electrode/Separator 30*30 mm ² 1.091 g This Battery Dimensions battery 32*32 mm ² 1.9342 g

The cell electrochemical properties of the prepared cell were measured and shown in FIG. 5 . The electrode current density of the cell was 5.0-6.0 mA/cm2.

<Comparative example>

For comparison, a cell under the same conditions as in Example was prepared except that it was in a non-pressurized state. The cell specifications are shown in Table 2 below, and the measurement results of the electrochemical properties of the prepared cells are shown in FIG. 6 .

part standard weight note anode 25*25 mm ² 0.6680 g 6.0 mA/cm ² anode foil 25*25 mm ² 0.0223 g - Separator/C-M 30*30 mm ² 0.3157 g both sides cathode foil 30*30 mm ² 0.085 g pouch - 0.7072 g other parts - 0.1360 g Electrode/Separator 30*30 mm ² 1.091 g This Battery Dimensions battery 32*32 mm ² 1.9342 g

The energy per unit weight of Examples and Comparative Examples was calculated and shown in Table 3.

division active material
(%) discharge capacity
(mAh/g) Volume
(mAh) Voltage
(V) energy
(Wh) Wh/Kg
(electrode + separator) in comparison 70 50 23.4 3.68 0.085 78 Example 70 141.6~
149.9 66.2~70.1 3.68~3.69 0.25 to 0.26 223.3~237.0

Claims (1)

an all-solid-state battery cell in which a positive electrode, a negative electrode, and a solid electrolyte are stacked;
a rigid case surrounding the all-solid-state battery cell; and
An all-solid-state secondary battery comprising an elastic buffer layer interposed between the all-solid-state battery cell and the rigid case.

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