Electrolyte separators including lithium borohydride and composite electrolyte separators of lithium-stuffed garnet and lithium borohydride

1. A substrate comprising a first layer, wherein the first layer comprises:

A·(LiBH 4 )·B·(LiX)·C·(LiNH 2 ),

wherein X is fluorine, bromine, chlorine, or iodine, and

wherein 2.5<A<3.5, 1.5<B<2.5, and 2.5<C<3.5.

2. The substrate of claim 1 , wherein X is chlorine.

3. The substrate of claim 1 , wherein X is bromine.

4. The substrate of claim 1 , wherein X is iodine.

5. The substrate of claim 2 , wherein the first layer is 3LiBH 4 ·2LiCl·3LiNH 2 or 3LiBH 4 ·4LiCl·9LiNH 2 .

6. The substrate of claim 3 , wherein the first layer is 3LiBH 4 ·2LiBr·3LiNH 2 or 3LiBH 4 ·4LiBr·9LiNH 2 .

7. The substrate of claim 4 , wherein the first layer is 3LiBH 4 ·2LiI·3LiNH 2 or 3LiBH 4 ·4LiI·9LiNH 2 .

8. The substrate of claim 1 , further comprising a second layer, wherein the second layer comprises an oxide, a sulfide, a sulfide-halide, or a combination thereof.

9. The substrate of claim 8 , wherein the second layer comprises a sulfide or sulfide-halide selected from LSS, SLOPS, LSTPS, SLOBS, LATS, or LPS+X, wherein X is selected from the group consisting of Cl, I, and Br.

10. The substrate of claim 9 wherein the LPS+X is LPSI.

11. The substrate of claim 8 , wherein the sulfide is a lithium sulfide characterized by one of the following formula:

Li a Si b Sn c P d S e O f , wherein 2≤a≤8, 0≤b≤1, 0≤c≤1, b+c=1, 0.5≤d≤2.5, 4≤e≤12, and 0<f≤10;

Li a Si b P c S d X e , wherein 8<a<12, 1<b<3, 1<c<3, 8<d<14, and 0<e<1, wherein X is F, Cl, Br, or I;

Li g As h Sn j S k O l , wherein 2≤g≤6, 0≤h≤1, 0≤j≤1, 2≤k≤6, and 0≤l≤10;

Li m P n S p I q , wherein 2≤m≤6, 0≤n≤1, 0≤p≤1, 2≤q≤6;

a mixture of (Li 2 S):(P 2 S 5 ) having a molar ratio of Li 2 S:P 2 S 5 from about 10:1 to about 6:4 and LiI, wherein the ratio of [(Li 2 S):(P 2 S 5 )]:LiI is from 95:5 to 50:50;

LPS+X, wherein X is selected from Cl, I, or Br;

vLi 2 S+wP 2 S 5 +yLiX;

vLi 2 S+wSiS 2 +yLiX; or

vLi 2 S+wB 2 S 3 +yLiX.

12. The substrate of claim 8 , wherein the composition comprises:

a mixture of LiI and Al 2 O 3 ;

Li 3 N;

a mixture of LiBH 4 and LiX wherein X is selected from Cl, I, or Br; or

vLiBH 4 +wLiX+yLiNH 2 , wherein X is selected from Cl, I, or Br; and

wherein coefficients v, w, and y are rational numbers from 0 to 1.

13. The substrate of claim 8 , wherein the oxide is a lithium-stuffed garnet oxide characterized by the formula Li u La y Zr x O y ·zAl 2 O 3 , wherein

u is a rational number from 4 to 8;

v is a rational number from 2 to 4;

x is a rational number from 1 to 3;

y is a rational number from 10 to 14;

z is a rational number from 0.05 to 1; and

wherein u, v, x, y, and z are selected so that the lithium-stuffed garnet oxide is charge neutral.

14. The substrate of claim 8 , wherein the oxide is a lithium-stuffed garnet oxide characterized by the formula Li u La v Zr x O y ·zTa 2 O 5 , wherein

u is a rational number from 4 to 10;

v is a rational number from 2 to 4;

x is a rational number from 1 to 3;

y is a rational number from 10 to 14; and

z is a rational number from 0 to 1;

wherein u, v, x, y, and z are selected so that the lithium-stuffed garnet oxide is charge neutral.

15. The substrate of claim 8 , wherein the oxide is a lithium-stuffed garnet oxide characterized by the formula Li u La v Zr x O y ·zNb 2 O 5 , wherein

u is a rational number from 4 to 10;

v is a rational number from 2 to 4;

x is a rational number from 1 to 3;

y is a rational number from 10 to 14; and

z is a rational number from 0 to 1;

wherein u, v, x, y, and z are selected so that the lithium-stuffed garnet oxide is charge neutral.

16. The substrate of claim 8 , wherein the oxide is a lithium-stuffed garnet oxide characterized by the formula Li u La v Zr x O y ·zGa 2 O 3 , wherein

u is a rational number from 4 to 10;

v is a rational number from 2 to 4;

x is a rational number from 1 to 3;

y is a rational number from 10 to 14; and

z is a rational number from 0 to 1;

wherein u, v, x, y, and z are selected so that the lithium-stuffed garnet oxide is charge neutral.

17. The substrate of claim 1 , wherein the substrate is a thin film and wherein the thin film has a porosity less than 5 percent.

18. The substrate of claim 1 , wherein the substrate has grains with a d 90 grain size of less than 10 μm.

19. The substrate of claim 1 , wherein the substrate has a lithium ion conductivity greater than 1×10 −4 S/cm at 60° C.

20. A method for making a thin film comprising the substrate of claim 1 , comprising:

(a) providing a powder mixture, wherein the mixture comprises:

A·(LiBH 4 )·B·(LiX)·C·(LiNH 2 );

wherein X is F, Br, Cl, or I; and

wherein 2.5<A<3.5, 1.5<B<2.5, and 2.5<C<3.5;

(b) dropping, casting, or spraying the powder mixture on a substrate;

(c) heating the powder mixture with substrate to the mixture melting point but lower than the powder mixture decomposition temperature; and

(d) cooling the substrate to room temperature.