All-solid lithium secondary battery and preparation method thereof

1 . An all-solid lithium secondary battery, comprising:

a positive electrode active material layer;

a negative electrode active material layer; and

a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer,

wherein the negative electrode active material layer comprises a carbon structure and silver nanoparticles,

wherein the carbon structure comprises a structure in which a plurality of graphene sheets are connected to each other,

wherein the plurality of graphene sheets are interconnected to form a secondary particle in the form of a chain,

wherein the graphene sheets have an average lateral size of 10 nm to 500 nm, and

wherein the plurality of graphene sheets comprise two or more graphene sheets having different plane directions.

2 . The all-solid lithium secondary battery of claim 1 , wherein the silver nanoparticles are disposed on a surface of the carbon structure.

3 . The all-solid lithium secondary battery of claim 1 , wherein, in the carbon structure,

each of the plurality of the graphene sheets has an average thickness of 0.34 nm to 10 nm.

4 . The all-solid lithium secondary battery of claim 1 , wherein, in Raman spectrum measurement of the carbon structure,

the carbon structure has an I D /I G of 0.9 to 2.0.

5 . The all-solid lithium secondary battery of claim 1 , wherein the carbon structure has a specific surface area of 200 m 2 /g to 1,100 m 2 /g.

6 . The all-solid lithium secondary battery of claim 1 , wherein an oxygen content of the carbon structure is in a range of 1 wt % to 10 wt % based on a total weight of the carbon structure.

7 . The all-solid lithium secondary battery of claim 1 , wherein the carbon structure is included in an amount of 50 wt % to 98 wt % in the negative electrode active material layer.

8 . The all-solid lithium secondary battery of claim 1 , wherein the silver nanoparticles have an average particle diameter of 1 nm to 100 nm.

9 . The all-solid lithium secondary battery of claim 1 , wherein, in the negative electrode active material layer,

the silver nanoparticles are included in an amount of 1 wt % to 40 wt % based on a total weight of the carbon structure and the silver nanoparticles.

10 . The all-solid lithium secondary battery of claim 1 , wherein a weight ratio of the carbon structure to the silver nanoparticles is in a range of 99:1 to 60:40.

11 . The all-solid lithium secondary battery of claim 1 , wherein the negative electrode active material layer further comprises a negative electrode binder.

12 . The all-solid lithium secondary battery of claim 1 , wherein the negative electrode active material layer has a thickness of 1 μm to 100 μm.

13 . The all-solid lithium secondary battery of claim 1 , further comprising:

a negative electrode collector; and

a metal layer disposed between the negative electrode active material layer and the negative electrode collector in a charged state,

wherein the metal layer comprises lithium.

14 . A method of preparing the all-solid lithium secondary battery of claim 1 , the method comprising:

a first step of forming a dry mixed powder including the carbon structure and the silver nanoparticles disposed on the carbon structure by reducing silver ions in a mixture of the silver ions and the carbon structure; and

a second step of forming the negative electrode active material layer on a negative electrode collector through a negative electrode mixture including the dry mixed powder.