Ionic conductor, all-solid state battery, and method of producing ionic conductor

1 . An ionic conductor comprising:

Li;

P;

S;

BH 4 ; and

I,

wherein a crystalline phase X having peaks at a position of 2θ=29.1°±0.5° and 30.4°±0.5° in XRD measurement using a CuKα ray is included,

wherein the ionic conductor has a composition represented by (100−α){(1−β)LiBH 4 -βP 2 S 5 }-αLiI, and

wherein α satisfies 0<α≤20, and β satisfies 0.01<β≤0.3.

2 . The ionic conductor according to claim 1 , wherein when an intensity of the peak at 2θ=29.1°±0.5° is denoted by IA and an intensity of the peak at 2θ=30.4°±0.5° is denoted by I B , a ratio of I B to I A (I B /I A ) is 35% or more.

3 . The ionic conductor according to claim 2 , wherein I B /I A is 60% or more.

4 . The ionic conductor according to claim 1 , wherein the ionic conductor is 95 (0.9LiBH 4 -0.1P 2 S 5 )-5LiI.

5 . An all-solid state battery comprising:

a positive electrode layer;

a negative electrode layer; and

a solid electrolyte layer provided between the positive electrode layer and the negative electrode layer,

wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains the ionic conductor according to claim 1 .

6 . The all-solid state battery according to claim 5 , wherein the negative electrode layer contains the ionic conductor.

7 . The all-solid state battery according to claim 6 , wherein the negative electrode layer contains a Li elemental substance or a Li alloy.

8 . A production method for an ionic conductor, the production method comprising:

preparing an intermediate containing Li, P, S, and BH 4 ;

adding an I source to the intermediate to obtain a precursor; and

calcinating the precursor to obtain an ionic conductor having a crystalline phase X having peaks at a position of 2θ=29.1°±0.5° and 30.4°±0.5° in XRD measurement using a CuKα ray.

9 . The production method according to claim 8 , wherein the I source is LiI.

10 . The production method according to claim 8 , wherein the precursor is obtained by amorphizing a mixture containing the intermediate and the I source.