CATHODE ACTIVE MATERIAL COATED WITH LITHIUM BORATE DOPED LITHIUM CARBONATE AND SULFIDE ALL-SOLID-STATE BATTERY COMPRISING SAME

1 - 28 . (canceled)

29 . A coated cathode active material comprising:

particles of a cathode active material (CAM); and

a coating coated on surface of the particles,

wherein the coating comprises a lithium carbonate doped with lithium borate (LCBO) having a formula of Li 2+x C 1−x B x O 3 , wherein 0<x≤0.3, and wherein the coating has a thickness in a range from 0.5 to 20 nm, and the LCBO is formed between lithium carbonate on surface of the particles of the CAM and lithium borate or a precursor of lithium borate,

wherein the coating comprising the LCBO is prepared by:

a) applying to the particles of the CAM with a coating solution comprising a solvent, a lithium precursor and a borate precursor, leading to particles of the CAM coated with the lithium precursor and the borate precursor after removal of the solvent; and

b) annealing the particles of the CAM coated with the lithium precursor and the borate precursor, wherein lithium carbonate on surface of the particles of the CAM, the lithium precursor and the borate precursor are converted into the LCBO, thereby obtaining particles of the CAM coated with the LCBO.

30 . The coated cathode active material of claim 29 , wherein the solvent for preparing the coating solution is nonaqueous and selected from the group consisting of methanol, ethanol, isopropanol, n-propanol, t-butanol, and mixtures thereof.

31 . The coated cathode active material of claim 29 , wherein the particles have an average diameter of 1-15 μm.

32 . The coated cathode active material of claim 29 , wherein the CAM is selected from the group consisting of Li x MO 2 , Li x Ni 1-y-z Co y M1 z O 2 and Li x Ni 1-y-z Mn y M2 z O 2 , wherein M is at least one selected from the group consisting of Ni, Co, Mn, Al, B, Fe, Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Rh, Pd, Cu, Zn, Cd, Ga, In, Sn, and rare earth elements, wherein M1 is at least one selected from the group consisting of Mn, Al, B, Fe, Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Rh, Pd, Cu, Zn, Cd, Ga, In, Sn, and rare earth elements, wherein M2 is at least one selected from the group consisting of Co, Al, B, Fe, Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Rh, Pd, Cu, Zn, Cd, Ga, In, Sn, and rare earth elements, and wherein 0.95≤x≤1.1, 1-y-z>0, 0<y≤0.5, 0≤z≤0.5.

33 . The coated active material of claim 29 , wherein the CAM is surface-doped by a doping element which is at least one selected from the group consisting of Ni, Co, Mn, Al, B, Fe, Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Rh, Pd, Cu, Zn, Cd, Ga, In, Sn, Si, Ge, S, P, and rare earth elements.

34 . The coated active material of claim 29 , wherein the CAM contains element Ni with a molar fraction of at least 70% in all metal elements other than lithium.

35 . The coated active material of claim 29 , wherein the cathode active material is polycrystalline particles or single crystalline particles.

36 . The coated cathode active material of claim 29 , wherein a concentration of lithium carbonate in the coating decreases from a surface of the particles of the CAM to an exterior of the coating, and wherein a concentration of lithium borate decreases from the exterior surface of the coating to the surface of the particles of the CAM.

37 . The coated cathode active material of claim 29 , wherein the LCBO has a formula selected from the group consisting of Li 2.05 C 0.95 B 0.05 O 3 , Li 2.10 C 0.90 B 0.10 O 3 , Li 2.15 C 0.85 B 0.15 O 3 , Li 2.25 C 0.75 B 0.25 O 3 , and Li 2.30 C 0.70 B 0.30 O 3 .

38 . A method for preparing the coated cathode active material of claim 29 , comprising:

a) determining weight percentage of lithium carbonate on surface of particles of cathode active material;

b) preparing a coating solution comprising a solvent, a lithium precursor and a borate precursor, wherein the amounts of the lithium precursor and borate precursor are calculated based on the formula Li 2+x C 1−x B x O 3 , wherein 0<x≤0.3, and the weight percentage of lithium carbonate from step a);

c) applying the coating solution to the particles of the cathode active material, leading to particles of the CAM coated with the lithium precursor and the borate precursor after removal of the solvent; and

d) annealing the particles of the CAM coated with the lithium precursor and the borate precursor, wherein the lithium carbonate on surface of particles of cathode active material, the lithium precursor and the borate precursor are converted into lithium carbonate doped with lithium borate (LCBO) thereby obtaining the coated cathode active material.

39 . The method of claim 38 , wherein the solvent for preparing the coating solution is nonaqueous and selected from the group consisting of methanol, ethanol, isopropanol, n-propanol, t-butanol, and mixtures thereof.

40 . The method of claim 38 , wherein the coating solution is annealed in a range from 150 to 600° C. for a duration in a range from 0.5 to 3 hr under an oxygen atmosphere.

41 . The method of claim 38 , wherein applying the coating solution comprises spray coating the coating solution onto surface of the cathode active material or mixing the particles of the cathode active material with the coating solution.

42 . A cathode layer comprising the coated cathode active material of claim 29 .

43 . The cathode layer of claim 42 , further comprising an electrically conductive material selected from carbon fiber, vapor growth carbon fiber, carbon nanotube, graphite fiber, and mixtures thereof.

44 . The cathode layer of claim 42 , further comprising a sulfur-containing inorganic electrolyte selected from the group consisting of Li 2 S—P 2 S 5 , Li 2 S—P 2 S 5 -LiHa, Li 2 S—P 2 S 5 —P 2 O 5 , Li 2 S—Li 3 PO 4 —P 2 S 5 , Li 3 PS 4 , Li 4 P 2 S 6 , Li 10 GeP 2 S 12 , Li 3.25 Ge 0.25 P 0.75 S 4 , Li 7 P 3 S 11 , Li 3.25 P 0.95 S 4 , Li 7-x PS 6-x Ha x , and mixtures thereof wherein “Ha” is one or more halogen elements, and 0.2<x≤1.

45 . An all-solid-state battery (ASSB) comprising the cathode layer of claim 42 .

46 . The ASSB of claim 45 , further comprising an inorganic solid electrolyte layer, wherein the inorganic solid electrolyte layer comprises a sulfur-containing inorganic electrolyte selected from the group consisting of Li 2 S—P 2 S 5 , Li 2 S—P 2 S 5 -LiHa, Li 2 S—P 2 S 5 —P 2 O 5 , Li 2 S—Li 3 PO 4 —P 2 S 5 , Li 3 PS 4 , Li 4 P 2 S 6 , Li 10 GeP 2 S 12 , Li 3.25 Ge 0.25 P 0.75 S 4 , Li 7 P 3 S 11 , Li 3.25 P 0.95 S 4 , Li 7-x PS 6-x Ha x , and mixtures thereof, wherein “Ha” is one or more halogen elements, and 0.2<x<1.

47 . The ASSB of claim 45 , wherein when the ASSB is charged and discharged for 20 cycles at 45° C. from 2.8V to 4.25V at 0.1 C for cycles 1 and 2, 0.33 C for cycles 3 and 4, 1.0 C for cycle 5, and 0.5 C for cycles 6 to 20, the ASSB exhibits a 20 th cycle life retention rate of at least 98%, wherein each cycle charges to 4.25V and discharges to 2.8V, and wherein the 20 th cycle life retention rate is the ratio of the discharge specific capacity at the 20 th cycle to the initial discharge specific capacity at 0.5 C at 45° C.

48 . The ASSB of claim 45 , where the ASSB possesses an initial discharge specific capacity of at least 190 mAh/g at 0.1 C at 45° C.