All-solid secondary battery
An all-solid secondary battery, comprising: a cell comprising a positive electrode active material layer, a negative electrode active material comprising at least one of lithium metal and a lithium-containing alloy, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein a ratio of volume density to true density of the positive electrode active material layer is about 0.6 or greater, wherein a ratio of volume density to true density of the solid electrolyte layer is about 0.6 or greater, and wherein an average pressure applied to opposite sides of the solid electrolyte layer in a fully discharged state is greater than 0 megapascals and 7.5 megapascals or less.
1. An all-solid secondary battery, comprising:
a cell comprising:
a positive electrode active material layer comprising a lithium transition metal oxide comprising layered rock-salt-type structure and a solid electrolyte,
a negative electrode active material layer comprising at least one of lithium metal and a lithium-containing alloy, and
a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the solid electrolyte layer comprises a sulfide solid electrolyte material;
a pair of pressure applying members disposed on opposite sides of the cell and configured to apply a pressure to the opposite sides of the cell; and
a plurality of pressure control members disposed at a periphery of each of the pressure applying members configured to control the pressure applied by the pair of pressure applying members,
wherein a ratio of volume density to true density of the positive electrode active material layer is about 0.6 or greater,
wherein a ratio of volume density to true density of the solid electrolyte layer is about 0.6 or greater,
wherein an average pressure applied to the opposite sides of the cell in a fully discharged state is about 0.5 megapascals to about 6.0 megapascals,
wherein a ratio of a standard deviation of a pressure distribution of the pressure applied to the opposite sides of the cell to the average pressure applied to the opposite sides of the cell in the fully discharged state, is about 0.35 or less, and
wherein the all-solid secondary battery is configured to has a capacity retention of greater than or equal to 84 percent after 50 cycles of charging and discharging at a temperature of 45° C. under a charge current 0.05 C, a discharge current of 0.05 C, and an operating voltage of 2.5 volts to 4 volts.
2. The all-solid secondary battery of claim 1 ,
wherein the ratio of the standard deviation of the pressure distribution to the average pressure applied to the opposite sides of the cell is about 0.15 to about 0.25.
3. The all-solid secondary battery of claim 1 , wherein the positive electrode active material layer comprises a compound represented by the formula LiNixCoyAlzO 2 ,
wherein 0≤x≤1, 0<y<1, 0<z<1, and x+y+z=1, or
LiNix′Coy′Mnz′O2
wherein 0≤x′≤1, 0<y′<1, 0<z′<1, and x′+y′+z′=1.
4. The all-solid secondary battery of claim 1 ,
wherein the positive electrode active material layer further comprises a binder.
5. The all-solid secondary battery of claim 4 ,
wherein the binder comprises styrene-butadiene rubber, polytetrafluoroethylene, poly(vinylidene fluoride), polyethylene, or a combination thereof.
6. The all-solid secondary battery of claim 1 ,
wherein the ratio of the volume density to the true density of the positive electrode active material layer is about 0.7 to about 0.95.
7. The all-solid secondary battery of claim 1 ,
wherein the negative electrode active material layer is a lithium metal layer.
8. The all-solid secondary battery of claim 1 ,
wherein the lithium-containing alloy is an alloy of lithium metal and at least one of indium, aluminum, tin, and silicon.
9. The all-solid secondary battery of claim 1 ,
wherein the solid electrolyte layer comprises at least one of sulfur, silicon, phosphorus, and boron.
10. The all-solid secondary battery of claim 1 ,
wherein the ratio of the volume density to the true density of the solid electrolyte layer is about 0.75 to about 0.995.
11. The all-solid secondary battery of claim 1 ,
wherein the solid electrolyte layer has an average thickness of about 50 micrometers to about 100 micrometers.
12. The all-solid secondary battery of claim 1 ,
wherein a surface of the cell has an area of about 20 square centimeters to about 1500 square centimeters.
13. The all-solid secondary battery of claim 1 ,
wherein each of the pressure applying members and each of the plurality of pressure control members independently comprises stainless steel, steel, or a resin.
14. The all-solid secondary battery of claim 1 , further comprising a pressure measuring film disposed between the pair of pressure applying members,
wherein a pressure applied to each pressure application site is measured by applying pressure to the pressure measuring film.
15. The all-solid secondary battery of claim 1 , wherein
the ratio of volume density to true density of the positive electrode active material layer is about 0.65 to about 0.9;
the ratio of volume density to true density of the solid electrolyte layer is about 0.65 to about 0.9; and
the ratio of the standard deviation of the pressure distribution to the average pressure applied to the opposite sides of the cell is about 0.15 to about 0.35.