Composite electrolyte for lithium metal battery, preparing method thereof, and lithium metal battery comprising the same

1. A composite electrolyte for a lithium metal battery, comprising:

a network web formed of a fiber containing a polymer and inorganic particles, and a lithium salt,

wherein a content of the inorganic particles is 1 wt % to 5 wt % based on a total weight of the composite electrolyte,

the polymer is polyethylene oxide,

the inorganic particles are each TiO 2 , and

the lithium salt is lithium bis(trifluoromethanesulfonyl) imide (LiTFSI).

2. A composite electrolyte for a lithium metal battery, comprising:

a network web formed of a fiber containing a polymer and inorganic particles; and

a lithium salt,

wherein a content of the inorganic particles is 1 wt % to 5 wt % based on a total weight of the composite electrolyte,

the polymer is polyethylene oxide,

the inorganic particles are at least one selected from SiO 2 , TiO 2 , ZnO, Al 2 O 3 , BaTiO 3 , and cage-structured silsesquioxane, and

the lithium salt is at least one selected from lithium bis(trifluoromethanesulfonyl) imide (LiTFSI), LiSCN, LiN(CN) 2 , LiClO 4 , LiBF 4 , LiAsF 6 , LiPF 6 , LiCF 3 SO 3 , LiN(SO 2 C 2 F 5 ) 2 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 F) 2 , LiSbF 6 , LiPF 3 (CF 2 CF 3 ) 3 , LiPF 3 (CF 3 ) 3 , and LiB(C 2 O 4 ) 2 .

3. The composite electrolyte of claim 2 ,

wherein the polymer has a weight average molecular weight of 400,000 to 1,000,000.

4. The composite electrolyte of claim 2 ,

wherein the inorganic particles have an average particle diameter of 15 nm to 25 nm.

5. The composite electrolyte of claim 2 ,

wherein the fiber has an average particle diameter of 500 nm to 5 μm.

6. The composite electrolyte of claim 2 ,

wherein the composite electrolyte has a thickness of 5 μm to 30 μm.

7. The composite electrolyte of claim 2 ,

wherein the composite electrolyte has a hardness of 0.01 GPa to 1 GPa at 25° C. and an elastic modulus of 0.1 GPa to 10 GPa at 25° C.

8. The composite electrolyte of claim 2 ,

wherein the cage-structured silsesquioxane is represented by Formula 1:

Si k O 1.5k (R 1 ) a (R 2 ) b (R 3 ) c   [Formula 1]

wherein, in Formula 1, R 1 , R 2 , and R 3 are each independently a hydrogen, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C2-C30 alkenyl group, a substituted or unsubstituted C2-C30 alkynyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C6-C30 aryloxy group, a substituted or unsubstituted C2-C30 heteroaryl group, a substituted or unsubstituted C4-C30 carbocyclic group, or a silicon-containing functional group; and

a, b, and c are each an integer of 1 to 20, and a, b, and c are selected such that the sum thereof (k=a+b+c) satisfies 6≤k≤20.

9. The composite electrolyte of claim 8 ,

wherein the cage-structured silsesquioxane is represented by at least one of Formula 2 or Formula 3:

wherein in Formulae 2 and 3, R 1 to R 8 are each independently the same as described in connection with R 1 to R 3 in Formula 1.

10. A lithium metal battery, comprising:

a positive electrode;

a negative electrode; and

the composite electrolyte of claim 2 interposed between the positive electrode and the negative electrode.

11. A method of preparing the composite electrolyte of claim 2 , comprising:

preparing a composition comprising the polymer, the inorganic particles, and an organic solvent; and

electrospinning the composition.