Cathode active material coated with lithium borate doped lithium carbonate and sulfide all-solid-state battery comprising same
Disclosed are cathode active material (CAM) coated with a lithium carbonate doped with lithium borate with a formula of Li 2+x C 1−x B x O 3 wherein 0<x<0.5 and a preparation method therefor. Also disclosed is a cathode layer comprising the coated CAM in the form of particles. In one embodiment, an all-solid-state battery comprising the cathode layer exhibits improved stability and cycling performance.
1 . A coated cathode active material comprising:
particles of a cathode active material (CAM) comprising lithium carbonate (LCO) on the surface of the particles; and
a coating coated on the particles,
wherein the coating on the particles comprises a lithium carbonate borate (LCBO) having a formula of Li 2+x C 1−x B x O 3 , wherein 0<x≤0.3, the coating has a thickness in a range from 0.5 to 20 nm, and
wherein the coating comprising the LCBO is prepared by:
a) applying to the particles of the CAM a coating solution comprising a nonaqueous 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 nonaqueous solvent; and
b) annealing the particles of the CAM coated with the lithium precursor and the borate precursor, wherein at least a portion of the LCO on the 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, wherein both the LCBO and LCO are present on the particles of the CAM.
2 . The coated cathode active material of claim 1 , wherein the particles have an average diameter of 1-15 μm.
3 . The coated cathode active material of claim 1 , 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.
4 . The coated cathode active material of claim 1 , 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 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.
5 . The coated active material of claim 4 , 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.
6 . The coated active material of claim 1 , wherein the CAM contains element Ni with a molar fraction of at least 50% in all metal elements other than lithium.
7 . The coated active material of claim 1 , wherein the cathode active material is polycrystalline particles or single crystalline particles.
8 . A cathode layer comprising the coated cathode active material of claim 1 .
9 . The cathode layer of claim 8 , wherein the coated cathode active material has a weight percentage of at least 65% of the cathode layer.
10 . The cathode layer of claim 8 , further comprising an electrically conductive material.
11 . The cathode layer of claim 10 , wherein the electrically conductive material is selected from carbon fiber, vapor growth carbon fiber, carbon nanotube, graphite fiber, and mixtures thereof.
12 . The cathode layer of claim 8 , further comprising a sulfur-containing inorganic electrolyte.
13 . The cathode layer of claim 12 , wherein the sulfur-containing inorganic electrolyte is 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—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.
14 . An all-solid-state battery (ASSB) comprising the cathode layer of claim 8 .
15 . The ASSB of claim 14 further comprising an inorganic solid electrolyte layer.
16 . The ASSB of claim 15 , wherein the inorganic solid electrolyte layer comprises a sulfur-containing inorganic electrolyte.
17 . The ASSB of claim 16 , wherein the sulfur-containing inorganic electrolyte is 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 2 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.
18 . The ASSB of claim 14 , wherein the LCBO has a formulation 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 .
19 . The ASSB of claim 14 , 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, 0.33C for cycles 3 and 4, 1.0C 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.
20 . The ASSB of claim 14 , where the ASSB possesses an initial discharge specific capacity of at least 180 mAh/g at 0.1 C at 45° C.
21 . The coated cathode active material of claim 1 , wherein the LCO is positioned between the LCBO and the surface of the CAM.
22 . The coated cathode active material of claim 1 , wherein the LCBO is formed between the LCO on the surface of the particles of the CAM and a lithium borate or a precursor of lithium borate.
23 . A method for preparing the coated cathode active material of claim 1 , comprising:
a) determining weight percentage of lithium carbonate on surface of particles of cathode active material;
b) preparing a coating solution comprising a nonaqueous 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 nonaqueous 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.
24 . The method of claim 23 , wherein the weight percentage of lithium carbonate is determined using thermal gravimetric analysis (TGA) or titration.
25 . The method of claim 23 , wherein the nonaqueous solvent for preparing the coating solution is non-aqueous and is selected from the group consisting of methanol, ethanol, isopropanol, n-propanol, t-butanol, and mixtures thereof.
26 . The method of claim 23 , 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.
27 . The method of claim 23 , wherein applying the coating solution comprises spray coating the coating solution onto surface of the cathode active material.
28 . The method of claim 23 , wherein applying the coating solution comprises mixing the particles of the cathode active material with the coating solution.