All-solid secondary battery and method of preparing the same

1. An all-solid secondary battery, comprising:

a cathode;

an anode; and

a solid electrolyte layer disposed between the cathode and the anode,

wherein the anode comprises

an anode current collector;

a first anode active material layer in contact with the anode current collector and comprising a first metal;

a second anode active material layer disposed between the first anode active material layer and the solid electrolyte layer and comprising a carbon-containing active material; and

a contact layer between the second anode active material layer and the solid electrolyte layer, and disposed such that the contact layer prevents contact between the second anode active material layer and the solid electrolyte layer,

wherein the contact layer comprises a second metal, and has a thickness less than a thickness of the first anode active material layer.

2. The all-solid secondary battery of claim 1 , wherein

the first metal comprises lithium metal or a lithium alloy, and

the second metal comprises lithium metal or a lithium alloy.

3. The all-solid secondary battery of claim 2 , wherein the first metal and the second metal are the same.

4. The all-solid secondary battery of claim 1 , wherein the thickness of the contact layer is 20% or less of the thickness of the first anode active material layer.

5. The all-solid secondary battery of claim 1 , wherein the thickness of the contact layer is about 1 nanometer to about 1 micrometer.

6. The all-solid secondary battery of claim 1 , wherein the thickness of the contact layer is less than a thickness of the second anode active material layer.

7. The all-solid secondary battery of claim 1 , wherein the contact layer does not comprise a carbon-containing material.

8. The all-solid secondary battery of claim 1 , wherein during a charge/discharge cycle, a volume change rate of the first anode active material layer is greater than a volume change rate of the contact layer.

9. The all-solid secondary battery of claim 1 , wherein during a charge/discharge cycle, a volume change rate of the second anode active material layer is greater than a volume change rate of the contact layer.

10. The all-solid secondary battery of claim 1 , wherein a volume of the contact layer after charge is about 1.5 times to about 20 times a volume of the contact layer after discharge.

11. The all-solid secondary battery of claim 1 , wherein a volume of the first anode active material layer after charge is about 1.5 times to about 500 times a volume of the first anode active material layer after discharge.

12. The all-solid secondary battery of claim 1 , wherein a volume of the second anode active material layer after charge is greater than a volume of the second anode active material layer after discharge, and the volume of the second anode active material layer after charge is about 2 times or less the volume of second anode active material layer after discharge.

13. The all-solid secondary battery of claim 1 , wherein the solid electrolyte layer comprises an oxide-containing solid electrolyte.

14. A method of preparing an all-solid secondary battery, the method comprising:

providing a cathode layer;

providing an anode layer;

providing a solid electrolyte layer;

attaching the anode layer to a surface of the solid electrolyte layer; and

attaching the cathode layer to another surface of the solid electrolyte layer,

wherein the providing of the anode layer comprises:

disposing a first layer comprising lithium metal or a lithium alloy on a first substrate,

disposing a second layer comprising a carbon-containing active material on a second substrate,

disposing the first layer and the second layer to face each other, and pressing the first substrate and the second substrate such that the first substrate and the second substrate move closer to each other,

wherein in the process of pressing the first substrate and the second substrate, a third layer comprising lithium metal or a lithium alloy is formed between the second substrate and the second layer, and the third layer has a thickness less than a thickness of the first layer.

15. The method of claim 14 , wherein

the second layer comprises a metal alloyable with lithium, and

in the pressing of the first substrate and the second substrate, the metal alloyable with lithium forms an alloy with lithium in the first layer and in the third layer.

16. The method of claim 14 , wherein in the providing of the anode layer further comprises, removing the second substrate after the third layer is formed.

17. The method of claim 14 , wherein a pressure applied in the pressing of the first substrate and the second substrate is about 150 megapascals to about 1,000 megapascals.

18. A method of preparing an anode layer of an all-solid secondary battery, the method comprising:

providing a first layer comprising lithium metal or a lithium alloy disposed on a first substrate,

providing a second layer comprising a carbon-based active material disposed on a second substrate;

disposing the first layer and the second layer to face each other; and

pressing the first substrate and the second substrate such that the first substrate and the second substrate are move closer to each other,

wherein, in the pressing of the first substrate and the second substrate,

a third layer comprising lithium metal or a lithium alloy is formed between the second substrate and the second layer, and the third layer has a thickness less than a thickness of the first layer.

19. The method of claim 18 , wherein

the second layer comprises a metal alloyable with lithium, and

in the pressing of the first substrate and the second substrate, the metal alloyable with lithium forms an alloy with lithium in the first layer and in the third layer, a pressure applied in the pressing of the first substrate and the second substrate is about 150 megapascals to about 1,000 megapascals.

20. The method of claim 18 , wherein the providing of the anode layer further comprises removing the second substrate after the third layer is formed.