Positive active material coated with lithium borate doped lithium carbonate and sulfide all-solid-state battery comprising same

Abstract

Disclosed are a positive active material (CAM) and a method for preparing the same, the positive active material (CAM) being coated with lithium carbonate doped with lithium borate having the formula of Li < 2 + x > C < 1-x > B < x > O < 3 >, where 0 lt; xlt; and 0.5. Also disclosed is a positive electrode layer comprising the coated CAM in particulate form. In one embodiment, an all-solid-state battery comprising the positive electrode layer exhibits improved stability and cycle performance.

Description

[0001] Cross-reference

[0002] This application claims priority to U.S. Application No. 18 / 194,145, filed Mar. 31, 2023, and claims the benefit of U.S. Application No. 63 / 386,183, filed Dec. 6, 2022, the entire contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates to a cathode active material coated with lithium carbonate borate and a sulfide-based all-solid-state battery (ASSB) including the same. Background Art

[0004] All-solid-state batteries (ASSBs) are considered promising candidates for future energy storage devices because they can enable the use of lithium metal as an anode material and result in higher specific energy compared to conventional lithium-ion batteries based on organic liquid electrolytes. Sulfide solid electrolyte (SE) materials contain elemental sulfur in the -2 oxidation state (S -2 ) and have a narrow intrinsic electrochemical window. Thiophosphate-based solid electrolytes (SEs) contain elemental phosphorus (P) and sulfur (S) and are particularly promising due to their high ionic conductivity, good mechanical compatibility, and relatively low cost. Passivation of the SE is necessary for the reversible operation of all-solid-state batteries. In particular, the adaptability of conventional high-capacity cathode active materials (CAMs) such as lithium metal oxides CAM (e.g., LiNi 0.88 Co 0.09 Al 0.03 O2--NCA88) etc. to ASSBs is affected by the interfacial resistance. The interfacial resistance is attributed to various factors such as surface impurities on the CAM surface, severe reactions between lithium metal oxides and sulfide SEs, the space charge layer effect, lattice mismatch, and poor wettability of the SE. It is known that surface impurities such as LiOH and Li2CO3 are formed on the CAM surface under ambient atmospheric conditions, leading to deterioration of the electrochemical performance of conventional LIBs. When it comes to ASSBs, S / O exchange at the CAM / SE interface and the poor ionic conduction properties of surface impurities are the main concerns. Zhang et al.'s 1 computational model reported that the Li + conductivity in crystalline Li2CO3 is ~10 -10 S cm -1 at room temperature and may lead to high interfacial resistance.

[0005] Various protective coatings have been developed to reduce the interfacial resistance. LiNbO3 is one of the most studied coating materials for sulfide ASSBs because of its high Li -6 conductivity of ~10 -1 S cm +Conductivity. US20110045348A1 discloses that a LiNbO3 layer coating on the CAM can reduce the interfacial resistance.

[0006] However, such coating materials may not fully address the challenges. Zhang et al. 2 reported that transition metals may diffuse from the CAM into the thin film coating. First-principles calculations also indicate that the high binding energy of the PO4 group creates a driving force for S / O exchange between the oxygen atoms in the coatings of lithium transition metal oxides such as LiNbO3 and LiTaO3 and the S atoms in the sulfide SE. In addition, the relatively low oxidation limit of these ternary metal oxide coatings raises concerns about their stability at high voltages. Therefore, additional coating materials and all-solid-state batteries incorporating them are still needed. Summary of the Invention

[0007] Disclosed herein is a cathode active material (CAM) and a method for preparing the same, wherein the cathode active material (CAM) is at least partially coated with lithium carbonate doped with lithium borate of the formula Li 2+ xC 1-x B x O3, where 0 < x < 0.5. Also disclosed are a cathode layer comprising the coated CAM and an all-solid-state battery comprising the cathode layer. When introduced into an all-solid-state battery, the CAM disclosed herein having the lithium carbonate doped with lithium borate improves the discharge specific capacity and / or cycle life stability. On the other hand, a CAM surface-doped with lithium borate is also disclosed herein. Brief Description of the Drawings

[0008] Figure 1 Shows a representative structure of the cathode layer: the cathode layer comprises CAM particles (1), a coating (2) composed of a thin (1 - 10 nm) LCBO (Li 2+x C 1-x B x O3; 0.00 < x < 0.5) layer surrounding the CAM particles, conductive carbon fibers (3), and a sulfide SE (4).

[0009] Figure 2 Shows a typical structure of an all-solid-state battery (ASSB): the all-solid-state battery includes a cathode layer (5), a solid electrolyte (6), a negative electrode layer (7), a first current collector (8 - 1) in contact with the negative electrode layer, and a second current collector (8 - 2) in contact with the cathode layer.

[0010] Figure 3 Shows a Li metal negative electrode, LPSCl (Li6PS5Cl) SE, and a cathode layer comprising NCA88 (LiNi 0.88 Co 0.09 Al 0.03Graph of the specific capacity of a half-cell of a positive electrode layer with particles of O2 and vapor-grown carbon fiber (VGCF) versus the number of cycles. Cycles 1 and 2 were cycled at 0.1C charge / discharge; cycles 3 and 4 were cycled at 0.33C charge / discharge, cycle 5 was cycled at 1.0C charge / discharge, and cycles 6 - 25 were cycled at 0.5C charge / discharge. The cycle graph compares Li-coated with approximately 5nm 2+x C 1-x B x NCA88 CAM of O3, where x = 0, 0.05, 0.1, 0.15, 0.25, 0.3, 0.5, and 1.

[0011] Figure 4 Graph showing the initial 0.1C discharge specific capacity of 5nm LCBO-coated CAM, with x = 0, 0.05, 0.1, 0.15, 0.25, 0.3, 0.5, and 1 (values from Table 1).

[0012] Figure 5 Graph showing the cycle-life capacity retention rate of 5nm LCBO-coated CAM, with x = 0, 0.05, 0.1, 0.15, 0.25, 0.3, 0.5, and 1 (values from Table 1).

[0013] Figure 6 Graph showing the specific capacity of a half-cell containing a Li metal anode, LPSCl (Li6PS5Cl) SE, and a positive electrode layer containing NCA88 (LiNi 0.88 Co 0.09 Al 0.03 O2) particles and VGCF versus the number of cycles at 45°C. Cycles 1 and 2 were cycled at 0.1C charge / discharge; cycles 3 and 4 were cycled at 0.33C charge / discharge, cycle 5 was cycled at 1.0C charge / discharge, and cycles 6 - 100 were cycled at 0.5C charge / discharge. The cycle graph compares Li-coated with approximately 5nm 2+x C 1-x B x NCA88 CAM of O3, where x = 0, 0.05, 0.15, and 0.25.

[0014] Figure 7Graph showing the specific capacity of a half-cell comprising a Li metal anode, LPSCl (Li6PS5Cl) SE, and a cathode layer comprising particles of NCA88 as the CAM and VGCF relative to the number of cycles at 75 °C. Cycles 1 and 2 were cycled at 0.1C charge / discharge; Cycles 3 and 4 were cycled at 0.33C charge / discharge, Cycles 5 and 6 were cycled at 0.5C charge / discharge; Cycles 7 and 8 were cycled at 1C charge / discharge; Cycles 9 and 10 were cycled at 2C charge / discharge; Cycles 11 and 12 were cycled at 5C charge / discharge; Cycles 13 - 40 were cycled at 0.5C charge / discharge. The cycle graph compares NCA88 CAMs with approximately 5 nm of Li 2+x C 1-x B x O3, where x = 0, x = 0.15 were coated using the sol - gel method, and x = 0.15, 0.20, and 0.25 were coated using the spray method. Detailed Description

[0015] In some embodiments, the cathode active material (CAM) is coated with LCBO of the formula Li 2+x C 1-x B x O3, where 0 < x < 0.5. Lithium carbonate borate (LCBO) is also known as lithium carbonate doped with lithium borate. In some embodiments, the coated CAM is introduced into the cathode layer as shown, for example, Figure 1 in. The cathode layer may have particles (1) of the cathode active material (CAM) coated with LCBO as the CAM coating (2), a conductive material such as carbon fiber (3), etc., and a solid electrolyte such as a sulfur - containing inorganic electrolyte or a sulfide - based solid electrolyte (4).

[0016] In some embodiments, the CAM is at least one selected from the group consisting of Li x MO2, Li x Ni 1-y- z Co y M1 z O2 and Li x Ni 1-y-z Mn y M2 zO2, where 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, where 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, where 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 where 0.95 ≤ x ≤ 1.1, 1 - y - z > 0, 0 < y ≤ 0.5, 0 ≤ z ≤ 0.5.

[0017] In some embodiments, the CAM is at least one selected from the group consisting of: Li x MO2, Li x Ni 1-y- z Co y M1 z O2 and Li x Ni 1-y-z Mn y M2 z O2, where 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, where 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, where 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 where 0.95 ≤ x ≤ 1.1, 1 - y - z > 0, 0 < y ≤ 0.5, 0 ≤ z ≤ 0.5.

[0018] In some embodiments, the CAM is surface doped with a doping element selected from at least one of 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.

[0019] In some embodiments, the CAM includes, but is not limited to: Li x Mn 1-y M y A2 (Formula 1), Li x Mn 1-y M y O 2-z X z (Formula 2), Li x Mn2O 4-z X z (Formula 3), Li x Mn 2-y M y A4 (Formula 4), Li x Co 1-y M y A2 (Formula 5), Li x Co 1-y M y O 2-z X z (Formula 6), Li x Ni 1-y M y A2 (Formula 7), Li x Ni 1-y M y O 2-z X z (Formula 8), Li x Ni 1-y Co y O 2-z X z (Formula 9), Li x Ni 1-y-z Co y M z A a , (Formula 10), Li x Ni 1-y- z Co y M z O 2-a X a (Formula 11), Li x Ni 1-y-z Mn y M z A a(Formula 12), Li x Ni 1-y-z Mn y M z O 2-a X a (Formula 13), Li x Ni 1-y-z Mn y M z O2 (Formula 14) and combinations thereof, where 0.95 ≤ x ≤ 1.1, 0 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.5, 0 ≤ a ≤ 2; M is selected from the group consisting of: Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, and rare earth elements; A is selected from the group consisting of: O, F, S, and P; and X is selected from the group consisting of: F, S, and P. In some embodiments, the CAM is in the form of particles having an average diameter in the following ranges: about 1 μm to about 15 μm, about 1 μm to about 12 μm, about 1 μm to about 10 μm, about 1 μm to about 7 μm, about 1 μm to about 6 μm, about 3 μm to about 15 μm, about 3 μm to about 12 μm, about 3 μm to about 10 μm, about 3 μm to about 7 μm, about 3 μm to about 6 μm, about 5 μm to about 15 μm, about 5 μm to about 12 μm, about 5 μm to about 10 μm, and all ranges and subranges therebetween. In some embodiments, the coated CAM can have the following range of concentrations in the positive electrode layer: about 50 wt% to about 99 wt%, about 50 wt% to about 95 wt%, about 50 wt% to about 90 wt%, about 50 wt% to about 85 wt%, about 50 wt% to about 80 wt%, about 55 wt% to about 99 wt%, about 55 wt% to about 95 wt%, about 55 wt% to about 90 wt%, about 55 wt% to about 85 wt%, about 55 wt% to about 80 wt%, about 60 wt% to about 99 wt%, about 60 wt% to about 95 wt%, about 60 wt% to about 90 wt%, about 60 wt% to about 85 wt%, about 60 wt% to about 80 wt%, about 65 wt% to about 99 wt%, about 65 wt% to about 95 wt%, about 65 wt% to about 90 wt%, about 65 wt% to about 85 wt%, about 65 wt% to about 80 wt%, about 70 wt% to about 99 wt%, about 70 wt% to about 95 wt%, about 70 wt% to about 90 wt%, about 70 wt% to about 85 wt%, about 70 wt% to about 80 wt%, and all ranges and subranges therebetween. In some embodiments, the CAM particles can be polycrystalline or single crystal. In some embodiments, the CAM particles can have a single particle size distribution or multiple particle size distributions.

[0020] In some embodiments, the CAM contains, among all metal elements other than lithium, an element Ni in a molar fraction of at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80% or at least 85%.

[0021] In some embodiments, the positive electrode coating material is Li3BO3-doped Li2CO3 (LCBO), where the ratio of Li2CO3-Li3BO3 is expressed as Li 2+x C 1-x B xO3. In some embodiments, 0 < x < 1, 0 < x ≤ 0.90, 0 < x ≤ 0.80, 0 < x ≤ 0.70, 0 < x ≤ 0.60, 0 < x ≤ 0.50, 0 < x ≤ 0.45, 0 < x ≤ 0.40, 0 < x ≤ 0.35, 0 < x ≤ 0.30, 0 < x ≤ 0.25, 0 < x ≤ 0.20, 0 < x ≤ 0.15, 0 < x ≤ 0.10, 0.10 ≤ x < 1, 0.10 ≤ x ≤ 0.90, 0.10 ≤ x ≤ 0.80, 0.10 ≤ x ≤ 0.70, 0.10 ≤ x ≤ 0.60, 0.10 ≤ x ≤ 0.50, 0.10 ≤ x ≤ 0.45, 0.10 ≤ x ≤ 0.40, 0.10 ≤ x ≤ 0.35, 0.10 ≤ x ≤ 0.30, 0.10 ≤ x ≤ 0.25, 0.10 ≤ x ≤ 0.20, 0.15 ≤ x < 1, 0.15 ≤ x ≤ 0.90, 0.15 ≤ x ≤ 0.80, 0.15 ≤ x ≤ 0.70, 0.15 ≤ x ≤ 0.60, 0.15 ≤ x ≤ 0.50, 0.15 ≤ x ≤ 0.45, 0.15 ≤ x ≤ 0.40, 0.15 ≤ x ≤ 0.35, 0.15 ≤ x ≤ 0.30, 0.15 ≤ x ≤ 0.25, 0.20 ≤ x < 1, 0.20 ≤ x ≤ 0.90, 0.20 ≤ x ≤ 0.80, 0.20 ≤ x ≤ 0.70, 0.20 ≤ x ≤ 0.60, 0.20 ≤ x ≤ 0.50, 0.20 ≤ x ≤ 0.45, 0.20 ≤ x ≤ 0.40, 0.20 ≤ x ≤ 0.35, 0.20 ≤ x ≤ 0.30, 0.25 ≤ x < 1, 0.25 ≤ x ≤ 0.90, 0.25 ≤ x ≤ 0.80, 0.25 ≤ x ≤ 0.70, 0.25 ≤ x ≤ 0.60, 0.25 ≤ x ≤ 0.50, 0.25 ≤ x ≤ 0.45, 0.25 ≤ x ≤ 0.40, 0.25 ≤ x ≤ 0.35, 0.30 ≤ x < 1, 0.30 ≤ x ≤ 0.90, 0.30 ≤ x ≤ 0.80, 0.30 ≤ x ≤ 0.70, 0.30 ≤ x ≤ 0.60, 0.30 ≤ x ≤ 0.50, 0.30 ≤ x ≤ 0.45, 0.30 ≤ x ≤ 0.40, 0.35 ≤ x < 1, 0.35 ≤ x ≤ 0.90, 0.35 ≤ x ≤ 0.80, 0.35 ≤ x ≤ 0.70, 0.35 ≤ x ≤ 0.60, 0.35 ≤ x ≤ 0.50, 0.35 ≤ x ≤ 0.45, 0.40 ≤ x < 1, 0.40 ≤ x ≤ 0.90, 0.40 ≤ x ≤ 0.80, 0.40 ≤ x ≤ 0.70, 0.40 ≤ x ≤ 0.60, 0.40 ≤ x ≤ 0.50, 0.45 ≤ x < 1, 0.45 ≤ x ≤ 0.90, 0.45 ≤ x ≤ 0.80, 0.45 ≤ x ≤ 0.70, 0.45 ≤ x ≤ 0.60, 0.50 ≤ x < 1, 0.50 ≤ x ≤ 0.90, 0.50 ≤ x ≤ 0.80, 0.50 ≤ x ≤ 0.70, 0.50 ≤ x ≤ 0.60, 0.70 ≤ x < 1, 0.70 ≤ x ≤ 0.90, 0.70 ≤ x ≤ 0.80, and all ranges and sub-ranges therebetween. The ranges of x disclosed above improve ionic conductivity by doping lithium borate into lithium carbonate, which in turn improves the discharge capacity of the all-solid-state battery. Doping lithium borate into lithium carbonate also results in higher cycle-life stability because the B-O bond is stronger than the C-O bond, which results in less O-S exchange between the positive electrode active material and the sulfide solid electrolyte. It has been found that doping a large amount of lithium borate into lithium carbonate can lead to a decrease in ionic conductivity and cycle-life stability, which results in a lower discharge capacity. Without wishing to be bound by theory, the decrease in the cycle-life capacity of the high lithium borate doped composition may be the result of the higher hardness of lithium borate (Mohs hardness scale of 4) compared to lithium carbonate (Mohs hardness scale of 0.6). The harder lithium borate coating will be more prone to cracking during the volume expansion and contraction of the positive electrode active material during cycling, thereby exposing the surface of the positive electrode active material to the solid electrolyte, which will reduce the cycle-life stability.

[0022] In some embodiments, the LCBO coating can have a thickness in the following ranges: 0.5 to 20 nm, 0.8 to 20 nm, 1 to 20 nm, 2 to 20 nm, 4 to 20 nm, 10 to 20 nm, 0.5 to 10 nm, 1.0 to 10 nm, 2 to 10 nm, or 4 to 10 nm. In some embodiments, the thickness is measured by observing the cross-section of the cut particles using a scanning electron microscope (SEM). In some embodiments, the thickness is measured on a transmission electron microscope (TEM). In some embodiments, the thickness is calculated by using the weight content of lithium carbonate, the content of lithium carbonate borate after doping, and the surface area (such as the BET specific surface area).

[0023] In some embodiments, the conductive material can be carbon fibers including but not limited to the following: vapor grown carbon fiber (VGCF), carbon nanotube (CNT), multi-walled carbon nanotube (MWCNT), carbon nanofiber, and graphite fiber. In some embodiments, the conductive material can have a BET measured specific surface area in the range of 1 to 600 m 2 / g and / or a resistance of no more than 0.5 Ω·cm. In some embodiments, the conductive material can be coated with an oxide material. In some embodiments, the oxide material includes but not limited to lithium borate, aluminum oxide, lithium zirconate (Li2ZrO3), LiNbO3, Li4SiO4, Li3PO4, Li2SiO3, LiPO3, Li2SO4, Li2WO4, Li2MoO4, LiAlO2, Li2TiO3, Li4Ti5O 12 or its composite oxide. In some embodiments, the conductive material coating with lithium borate includes but not limited to Li3B 11 O 18, Li3BO3, Li4B2O5, Li6B4O9, LiBO2, Li2B4O7, Li3B7O 12 and LiB3O5. In some embodiments, the conductive material (coated or uncoated) has a concentration in the positive electrode layer in the following ranges: 0.01 wt% to 5 wt%, 0.01 wt% to 4 wt%, 0.01 wt% to 3 wt%, 0.01 wt% to 2 wt%, 0.5 wt% to 5 wt%, 0.5 wt% to 4 wt%, 0.5 wt% to 3 wt%, 0.5 wt% to 2 wt%, 1 wt% to 5 wt%, 1 wt% to 4 wt%, 1 wt% to 3 wt%, 2 wt% to 5 wt%, 2 wt% to 4 wt%, and any or all ranges and sub-ranges therebetween.

[0024] In some embodiments, the method for preparing the coated positive electrode active material disclosed herein may include, for example, determining the weight percentage of lithium carbonate in the uncoated positive electrode active material by using thermogravimetric analysis (TGA) or titration. A coating solution containing a solvent, a lithium precursor, and a borate precursor may be prepared, wherein the amounts of the lithium precursor and the borate precursor are calculated based on the formula Li 2+x C 1-x B x O3 and the previously determined weight percentage of lithium carbonate present in the uncoated positive electrode active material. In some embodiments, the solvent used to prepare the coating solution is non-aqueous and is selected from the group consisting of methanol, ethanol, isopropanol, n-propanol, tert-butanol, and mixtures thereof. The coating solution may be applied to the uncoated positive electrode active material, and then the coating solution may be annealed, whereby the lithium precursor and the borate precursor are converted into lithium carbonate doped with lithium borate, and a coating is formed on the positive electrode active material. In some embodiments, the annealing is carried out in an oxygen atmosphere at a temperature in the range of 150 to 600 °C for a duration of 0.5 to 3 hours. In some embodiments, the coating solution may be applied by spraying the coating solution onto the uncoated positive electrode active material, which is referred to herein as the spraying method. In other embodiments, the coating solution may be applied by mixing the uncoated positive electrode active material with the coating solution to form a mixture, and then it may be formed into a gel by removing the solvent by means of vacuum, which is referred to herein as the sol-gel method.

[0025] In some embodiments, the solid electrolyte used can be any sulfide solid electrolyte, as long as it contains Li and S and has a desired lithium-ion conductivity. The sulfide solid electrolyte can be any crystalline material, glass-ceramic, and glass. In some embodiments, the solid electrolyte is a lithium-phosphate-sulfur (LPS) electrolyte. Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiHa (“Ha” is more than one halogen element), Li2S-P2S5-P2O5, Li2S-Li3PO4-P2S5, Li3PS4, Li4P2S6, Li 10 GeP2S 12 、Li 3.25 Ge 0.25 P 0.75 S4、Li7P3S 11 、Li 3.25 P 0.95 S4 and Li 7-x PS 6-x Ha x (argyrodite-type solid electrolyte, “Ha” is more than one halogen element, where 0.2 < x < 1.8). In some embodiments, the sulfide solid electrolyte in the positive electrode layer can have a concentration in the following ranges: 1 wt% to 35 wt%, 1 wt% to 30 wt%, 1 wt% to 25 wt%, 1 wt% to 20 wt%, 1 wt% to 15 wt%, 1 wt% to 10 wt%, 5 wt% to 35 wt%, 5 wt% to 30 wt%, 5 wt% to 25 wt%, 5 wt% to 20 wt%, 5 wt% to 15 wt%, 10 wt% to 35 wt%, 10 wt% to 30 wt%, 10 wt% to 25 wt%, 10 wt% to 20 wt%, 15 wt% to 35 wt%, 15 wt% to 30 wt%, 15 wt% to 25 wt%, 20 wt% to 30 wt%, and any and all ranges and sub-ranges therebetween.

[0026] In some embodiments, the positive electrode layer is sandwiched between a positive electrode current collector and a solid electrolyte layer. In some embodiments, the positive electrode layer includes a positive electrode active material (CAM), and the positive electrode active material (CAM) requires lithium ions (Li + ) and electrons (e-) that are respectively connected to both the solid electrolyte layer and the current collector. The connection of Li + is mainly provided by small particles of the sulfide-based solid electrolyte in the positive electrode layer, and the connection of e- is mainly provided by a conductive material. Sulfide-based solid electrolytes (such as the above-exemplified sulfide solid electrolytes) have a high Li+ conductivity. However, they are usually in relation to Li / Li +Potentials below 1.7 V or above 2.1 V deteriorate at the CAM / SE, CF / SE, and current collector / SE interfaces. The by-products of the deterioration typically have a low Li+ conductivity, which in turn requires a higher percentage of SE in the cathode composite layer, resulting in a lower percentage of CAM. Without wishing to be bound by theory, the LCBO coating disclosed herein extends the deterioration time and maintains a relatively high Li+ conductivity, thereby improving the cycling performance.

[0027] The cathode layer disclosed above can be incorporated into an all-solid-state battery. As shown, for example, Figure 2 in Figure 5, the cathode layer 5 can be used as the cathode in an all-solid-state battery (ASSB), and the all-solid-state battery can further include an anode (or anode layer) 7 and a solid electrolyte layer 6 between the cathode layer 5 and the anode 7. In some embodiments, the solid electrolyte of the solid electrolyte layer can be the same as or different from the solid electrolyte in the cathode layer. In some embodiments, the solid electrolyte layer is an inorganic solid electrolyte layer, such as a sulfur-containing inorganic electrolyte, including but not limited to Li2S-P2S5, Li2S-P2S5-LiHa (“Ha” is one or more halogen elements), Li2S-P2S5-P2O5, Li2S-Li3PO4-P2S5, Li3PS4, Li4P2S6, Li 10 GeP2S 12 、Li 3.25 Ge 0.25 P 0.75 S4、Li7P3S 11 、Li 3.25 P 0.95 S4 and Li 7-x PS 6-x Ha x (lithium thiogermanate solid electrolyte, “Ha” is one or more halogen elements, where 0.2 < x < 1.8).

[0028] In some embodiments, the ASSB has an initial discharge specific capacity of at least 180 mAh / g, at least 185 mAh / g, or at least 190 mAh / g at a discharge rate of 0.5 C at 45 °C.

[0029] In some embodiments, the ASSB has an initial discharge specific capacity of at least 190 mAh / g, at least 195 mAh / g, at least 200 mAh / g, or at least 205 mAh / g at a discharge rate of 0.1 C at 45 °C.

[0030] In some embodiments, when the ASSB is charged and discharged 20 cycles at 45 °C, where each cycle is charged to 4.25 V and discharged to 2.8 V, at 0.1 C for cycles 1 and 2, at 0.33 C for cycles 3 and 4, at 1.0 C for cycle 5, and at 0.5 C for cycles 6 to 20, the ASSB has a 20-cycle discharge of at least 180 mAh / g, at least 185 mAh / g, or at least 190 mAh / g and / or a 20th-cycle life retention rate of at least 95%, at least 96%, at least 97%, or at least 98%. The 20th-cycle life retention rate is the ratio of the discharge specific capacity at the 20th cycle as described above to the initial discharge specific capacity at 0.5 C at 45 °C.

[0031] In one embodiment, the present disclosure provides a layer for a positive electrode of a all-solid-state battery, wherein the layer comprises a cathode active material (CAM) coated with LCBO. In one embodiment, LCBO is formed between lithium carbonate and lithium borate or a precursor thereof on the surface of the CAM particles. In some embodiments, the lithium borate for doping lithium carbonate on the surface of the CAM includes, but is not limited to, Li3B 11 O 18 , Li3BO3, Li4B2O5, Li6B4O9, LiBO2, Li2B4O7, Li3B7O 12 and LiB3O5. In some embodiments, the lithium borate for doping lithium carbonate on the surface of the CAM is doped with a doping element. In some embodiments, the doping element is fluorine (F), sulfur (S), silicon (Si), germanium (Ge), or a mixture thereof. In some embodiments, the lithium borate includes more than one of the undoped or doped lithium borates as described above. In some embodiments, the lithium borate is structurally similar to lithium carbonate such that lithium carbonate doped with lithium borate is formed on the surface of the CAM.

[0032] In some embodiments, the LCBO formed on the surface of the CAM exhibits lower uniformity in terms of the concentration of lithium carbonate and lithium borate. In some embodiments, lithium carbonate exhibits a gradient concentration in the LCBO coating on the surface of the CAM particles. In some embodiments, the concentration of lithium carbonate has a relatively high concentration near (near) or close to the surface of the CAM particles and / or the concentration of lithium carbonate decreases from the surface of the CAM particles to the outer surface of the LCBO coating. In some embodiments, lithium borate exhibits a gradient concentration in the LCBO coating on the surface of the CAM particles. In some embodiments, the concentration of lithium borate is relatively high on or near the outer surface of the LCBO coating and / or the concentration of lithium borate decreases from the outer surface of the LCBO coating to the surface of the CAM particles. In some embodiments, the exposure of lithium carbonate is minimized to reduce or avoid side reactions between the positive active material and the sulfide electrolyte. In some embodiments, the LCBO is formed based on lithium carbonate on the surface of the CAM particles without any external lithium carbonate source. The gradient can be determined using high-resolution TEM and element mapping line scans such as energy dispersive spectroscopy (EDS) across the thickness of the coating.

[0033] In some embodiments, the CAM particles coated with the LCBO coating exhibit a core-shell structure, wherein the core is the CAM particle and the shell is the LCBO coating.

[0034] In one embodiment, the present disclosure provides an all-solid-state battery (ASSB) including the above-mentioned cathode layer.

[0035] In some embodiments, the present disclosure provides a positive electrode active material having a surface doped with lithium borate.

[0036] In some embodiments, the solid electrolyte layer of the ASSB is an inorganic solid electrolyte layer, such as a sulfur-containing inorganic electrolyte, including but not limited to Li2S-P2S5, Li2S-P2S5-LiHa ("Ha" is one or more halogen elements), Li2S-P2S5-P2O5, Li2S-Li3PO4-P2S5, Li3PS4, Li4P2S6, Li 10 GeP2S 12 , Li 3.25 Ge 0.25 P 0.75 S4、Li7P3S 11 , Li 3.25 P 0.95 S4 and Li 7-x PS 6-x Ha x (Argentum-type solid electrolyte, "Ha" is one or more halogen elements, of which 0.2 <x<1.8)。

[0037] The present disclosure will be better understood by reference to the following experimental details, but those skilled in the art will readily appreciate that the detailed specific experiments are illustrative only and are not meant to limit the present disclosure described herein, which is defined by the appended claims.

[0038] It should be noted that the transitional term "comprising", which is synonymous with "including", "containing", or "characterized by", is inclusive or open-ended and does not exclude additional, unrecited elements or method steps.

[0039] Example 1

[0040] Due to the standard manufacturing process, Li2CO3 is inherently on the surface of the CAM. Thus, the wt% of Li2CO3 relative to the CAM can be determined, for example, by using thermogravimetric analysis (TGA). The stoichiometric amount of Li3BO3 required to produce the LCBO coating is further calculated. For the LCBO coating with x = 0.15, a stoichiometric amount of Li precursor (such as lithium acetate or lithium metal) and B precursor (such as triisopropyl borate) are dissolved in a dry solvent (such as ethanol) to form a coating solution containing the Li precursor and the borate precursor. The coating solution is added to a predetermined amount of CAM, and the required Li3BO3 doping ratio is calculated from the TGA data. The mixture is stirred for 30 minutes and then the solvent is removed via vacuum while ultrasonicating, resulting in a gel of CAM coated with the Li precursor and the B precursor. Then the gel is annealed at 300 °C for 1 hour under an oxygen flow to form the LCBO coating.

[0041] For x = 0 to 1.00, the specific discharge capacity and cycle-life retention rate of various LCBO coating compositions are summarized in Table 1. For LCBO with x = 1.00 (no lithium carbonate in the coating), the CAM is first annealed in air at 600 °C for 16 hours to remove the inherently present Li2CO3 on the surface before coating with the stoichiometric amount of Li3BO3 sol-gel reagent. The positive electrode layer contains 65 wt% CAM (NCA88), 5 wt% carbon fiber, and 30 wt% lithium phosphorus sulfide chloride (LPSCl) (Li6PS5Cl). The positive electrode layer is electrochemically evaluated in torque-cells using Li metal on copper as the negative electrode and LPSCl (Li6PS5Cl) as the SE. The cells are cycled from 2.8 V to 4.25 V, charged / discharged at 0.1 C for cycles 1 and 2, charged / discharged at 0.33 C for cycles 3 and 4, charged / discharged at 1.0 C for cycle 5, and charged / discharged at 0.5 C for cycles 6 to 25.

[0042] The LCBO coating with x = 0.15 reduces the decay of discharge specific capacity while maintaining the initial battery performance at a high level. For example, as shown in Table 1 and Figure 4 as follows, for the half-cell containing undoped CAM (x = 0.00), the initial discharge capacity is 205.95 mAh / g at a discharge rate of 0.1C. When Li3BO3 is doped into Li2CO3 (x = 0.05, 0.10, and 0.15), the initial discharge specific capacities are 211.00 mAh / g, 208.03 mAh / g, and 204.46 mAh / g, respectively. When x = 1.00 (100% Li3BO3), the initial discharge capacity decreases to 186.39 mAh / g. The LCBO-coated CAM effectively reduces battery decomposition, as evidenced by the cycle-life capacity retention rate after 20 cycles at 0.5C in Table 1 and Figure 4 as shown, and may be crucial for achieving high-capacity SSBs, as evidenced by the increase in the initial discharge specific capacity at a rate of 0.1C, which is close to the theoretical capacity of CAM (for NCA88-LiNi 0.88 Co 0.09 Al 0.03 O2, 219.8 mAh / g). Table 1 Initial discharge (dChg.) specific capacity (mAh / g) of half-cells using LCBO-coated CAM at 45 °C and different C-rates for x = 0 - 1.

[0043]

[0044] a: The cycle-life 0.5C dChg. capacity retention rate is calculated by dividing the 0.5C dChg. capacity at the 20th cycle by the initial 0.5C dChg. capacity and multiplying by 100%.

[0045] Also as shown in Table 1 and Figure 5 as follows, the cycle-life capacity retention rates increase from 95.87% at x = 0 to 99.22%, 98.21%, 99.63%, 98.83%, and 99.04% at x = 0.05, 0.10, 0.15, 0.25, and 0.3, respectively. When x is 0.5 or 1.0, the cycle-life capacity retention rate drops to equal or below the level of the uncoated CAM (x = 0). In some cases, when x is higher than 0.5, some benefits may be brought, such as the medium- and short-term cycle-life capacity retention rate.

[0046] Figure 6 is a graph of specific capacity from cycle 1 to cycle 100. It shows that x = 0.05 and 0.15 have improved cycle performance compared to the uncoated (x = 0). The cycle performance of x = 0.25 gradually decreases to below the uncoated level, even though the specific capacity is higher in the early cycles.

[0047] Example 2

[0048] Using the same method for preparing the coating solution as detailed in Example 1, an LCBO coating was applied to the CAM surface via the spray method. The coating solution was applied to the CAM powder using a FD-MP-01D type rolling fluidized bed granulator and coater from Powrex Corporation. The coated CAM was then annealed in a stream of oxygen at 300 °C for 1 hour to form the LCBO coating.

[0049] For x = 0.00, x = 0.15 via the sol-gel method, and x = 0.15, 0.20, and 0.25, the 0.1C to 5C charge / discharge specific capacities and cycle-life retention rates of the LCBO coating compositions are shown in Figure 7 and summarized in Table 2. Comparing the sol-gel and spray-coated materials with x = 0.15, the spray-coated material shows similar rate and discharge performance but higher stability, most likely due to more uniform / complete coating coverage, which is a solid benefit of using the spray method over the sol-gel method. When comparing the spray-coated LCBO materials with x = 0.15 to 0.25, the material with x = 0.15 shows a higher rate capacity of over 200 mAh / g at 5C charge / discharge. The material with x = 0.25 shows a lower discharge capacity and rate capability, but does show a slight improvement in cycle-life capacity retention. When compared to the CAM with x = 0.00, all coated materials show improved performance.

[0050] Table 2 Initial discharge (dChg.) specific capacity (mAh / g) of half-cells with NCA88 CAM having approximately 5 nm of Li 2+x C 1-x B x O3 at 75 °C and different C-rates, where x = 0, x = 0.15 was coated using the sol-gel method, and x = 0.15, 0.20, and 0.25 were coated using the spray method. The 0.5C cycle-life capacity retention rate was calculated by dividing the 0.5C dChg. capacity of the 20th cycle by the initial 0.5C cycle dChg. capacity and multiplying by 100%.

[0051]

[0052] SG : Materials coated using the sol-gel method.

[0053] SC : Materials coated using the spray method.

[0054] In a first aspect of the present disclosure, a coated positive electrode active material comprises a positive electrode active material (CAM) and a coating in contact with the positive electrode active material, wherein the coating comprises lithium carbonate doped with lithium borate of the formula Li 2+x C 1-x B x O3, where 0 < x < 0.5.

[0055] In a second aspect according to the first aspect, the thickness of the coating is in the range of 0.5 to 20 nm.

[0056] In a third aspect according to any of the foregoing aspects, 0.00 < x ≤ 0.30.

[0057] In a fourth aspect according to any of the foregoing aspects, the positive electrode active material is in particulate form and has an average diameter of 1 to 15 μm.

[0058] In a fifth aspect according to any of the foregoing aspects, the CAM is selected from the group consisting of Li x MO2, Li x Ni 1-y-z Co y M1 z O2 and Li x Ni 1-y-z Mn y M2 z O2, where 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, where 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, where 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 where 0.95 ≤ x ≤ 1.1, 1 - y - z > 0, 0 < y ≤ 0.5, 0 ≤ z ≤ 0.5.

[0059] In a sixth aspect, the CAM is selected from the group consisting of Li x MO2, Li x Ni 1-y-z Co y M1 z O2 and Li x Ni 1-y-z Mny M2 z At least one selected from the group consisting of O2, where 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, where 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, where 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 where 0.95 ≤ x ≤ 1.1, 1 - y - z > 0, 0 < y ≤ 0.5, 0 ≤ z ≤ 0.5.

[0060] In a seventh aspect, the CAM is surface - doped with at least one doping element 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.

[0061] In an eighth aspect according to any of the foregoing aspects, the CAM contains element Ni with a molar fraction of at least 70% among all metal elements except lithium.

[0062] In a ninth aspect according to any of the foregoing aspects, the positive electrode active material is polycrystalline particles or single - crystal particles.

[0063] In a tenth aspect according to any of the foregoing aspects, the concentration of lithium carbonate in the coating decreases from the surface of the CAM towards the outside of the coating, and the concentration of lithium borate decreases from the outer surface of the coating towards the surface of the CAM.

[0064] In an eleventh aspect, a method for preparing a coated positive electrode active material according to any of the foregoing aspects, comprising:

[0065] a) Determining the weight percentage of lithium carbonate in the uncoated positive electrode active material;

[0066] b) Preparing a coating solution containing a solvent, a lithium precursor, and a borate precursor, where the amounts of the lithium precursor and the borate precursor are calculated based on the formulation and the weight percentage of lithium carbonate from step a);

[0067] c) Applying the coating solution to the uncoated positive electrode active material; and

[0068] d) Anneal the coating solution, where the lithium precursor and the borate precursor are converted into lithium carbonate doped with lithium borate (LCBO), thereby obtaining the coated positive electrode active material.

[0069] In a twelfth aspect according to the eleventh aspect, the solvent for preparing the coating solution is non-aqueous and is selected from the group consisting of methanol, ethanol, isopropanol, n-propanol, tert-butanol, and mixtures thereof.

[0070] In a thirteenth aspect according to any one of the eleventh to twelfth aspects, the coating solution is annealed in an oxygen atmosphere for a duration in the range of 0.5 to 3 hours within the range of 150 to 600 °C.

[0071] In a fourteenth aspect according to any one of the eleventh to thirteenth aspects, the application of the coating solution includes spraying the coating solution onto the positive electrode active material.

[0072] In a fifteenth aspect according to any one of the eleventh to thirteenth aspects, the application of the coating solution includes mixing the positive electrode active material in the coating solution.

[0073] In a sixteenth aspect, a positive electrode layer comprising the coated positive electrode active material described in any one of the first to fifteenth aspects above.

[0074] In a seventeenth aspect according to the sixteenth aspect, the weight percentage of the coated positive electrode active material is at least 65% of the positive electrode layer.

[0075] In an eighteenth aspect according to the sixteenth or seventeenth aspect, the positive electrode layer further comprises a conductive material.

[0076] In a nineteenth aspect according to the eighteenth aspect, the conductive material is selected from carbon fibers, vapor-grown carbon fibers, carbon nanotubes, graphite fibers, and mixtures thereof.

[0077] In a twentieth aspect according to any one of the sixteenth to nineteenth aspects, the positive electrode layer further comprises a sulfur-containing inorganic electrolyte.

[0078] In a twenty-first aspect according to the twentieth aspect, the sulfur-containing inorganic electrolyte is selected from the group consisting of: Li2S-P2S5, Li2S-P2S5-LiHa, Li2S-P2S5-P2O5, Li2S-Li3PO4-P2S5, Li3PS4, Li4P2S6, Li 10 GeP2S 12 、Li 3.25 Ge 0.25 P 0.75 S4、Li7P3S 11 、Li 3.25 P0.95 S4, Li 7-x PS 6-x Ha x and mixtures thereof, where "Ha" is one or more halogen elements and 0.2 < x < 1.

[0079] In a twenty - second aspect, a all - solid - state battery (ASSB) comprises a positive electrode layer as described in any one of the sixteenth to twenty - first aspects above.

[0080] In a twenty - third aspect according to the twenty - second aspect, the ASSB further comprises an inorganic solid electrolyte layer.

[0081] In a twenty - fourth aspect according to the twenty - third aspect, the inorganic solid electrolyte layer comprises a sulfur - containing inorganic electrolyte.

[0082] In a twenty - fifth aspect according to the twenty - fourth aspect, the sulfur - containing inorganic electrolyte is selected from the group consisting of: Li2S - P2S5, Li2S - P2S5 - LiHa, Li2S - P2S5 - P2O5, Li2S - Li3PO4 - P2S5, Li3PS4, Li4P2S6, Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, Li7P3S 11 Li 3.25 P 0.95 S4, Li 7-x PS 6-x Ha x and mixtures thereof, where "Ha" is one or more halogen elements and 0.2 < x < 1.

[0083] In a twenty - sixth aspect according to any one of the twenty - second to twenty - fifth aspects, the formulation of LCBO is selected from the group consisting of: Li 2.05 C 0.95 B 0.05 O3 (x = 0.05), Li 2.10 C 0.90 B 0.10 O3 (x = 0.10), Li 2.15 C 0.85 B 0.15 O3 (x = 0.15), Li 2.25 C 0.75 B 0.25 O3 (x = 0.25) and Li 2.30 C 0.70 B 0.30 O3 (x = 0.30).

[0084] In a twenty-seventh aspect according to any one of the twenty-second to twenty-sixth aspects, when the ASSB is charged and discharged 20 times from 2.8 V to 4.25 V at 45 °C, at 0.1 C for cycles 1 and 2, at 0.33 C for cycles 3 and 4, at 1.0 C for cycle 5, and at 0.5 C for cycles 6 to 20, the ASSB exhibits a 20th cycle life retention rate of at least 98%, where each cycle is charged to 4.25 V and discharged to 2.8 V, and the 20th cycle life retention rate is the ratio of the discharge specific capacity at the 20th cycle to the initial discharge specific capacity at 0.5 C at 45 °C.

[0085] In a twenty-eighth aspect according to any one of the twenty-second to twenty-seventh aspects, the initial discharge specific capacity of the ASSB at 0.1 C at 45 °C is at least 190 mAh / g.

[0086] References

[0087] 1. Zhang, et al., Achieving Both High Ionic Conductivity and High Interfacial Stability with the Li2+xC1-xBxO3 Solid-State Electrolyte: Design from Theoretical Calculations, ACS Appl. Mater. Interfaces 2020, 12, 5, 6007 - 6014. DOI: 10.1021 / acsami.9b22185.

[0088] 2. Zhang, et al., Direct Visualization of the Interfacial Degradation of Cathode Coatings in Solid State Batteries: A Combined Experimental and Computational Study, Adv. Energy Mater. 2020, 10, 1903778. DOI: 10.1002 / aenm.201903778.

Claims

1. A coated positive electrode active material, comprising: a positive electrode active material (CAM); and a coating in contact with the positive electrode active material, wherein the coating comprises lithium carbonate doped with lithium borate (LCBO) of the formula Li 2+x C 1-x B x O3, where 0 < x < 0.

5.

2. The coated positive electrode active material according to claim 1, wherein the thickness of the coating ranges from 0.5 to 20 nm.

3. The coated positive electrode active material according to claim 1, wherein 0 < x ≤ 0.

3.

4. The coated positive electrode active material according to claim 1, wherein the positive electrode active material is in the form of particles, and the average diameter of the particles is 1 to 15 μm.

5. The coated positive electrode active material according to claim 1, wherein the CAM is selected from the group consisting of Li x MO2, Li x Ni 1-y- z Co y M1 z O2, and Li x Ni 1-y-z Mn y M2 z O2. 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.

6. The coated positive active material according to claim 1, wherein the CAM is selected from the group consisting of Li x MO2, Li x Ni 1-y- z Co y M1 z O2 and Li x Ni 1-y-z Mn y M2 z O2. 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.

7. The coated active material according to claim 6, wherein the CAM is surface - doped with a doping element selected from at least one of 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.

8. The coated active material according to claim 1, wherein the CAM contains, among all metal elements other than lithium, an element Ni with a molar fraction of at least 70%.

9. The coated active material according to claim 1, wherein the positive electrode active material is polycrystalline particles or single crystal particles.

10. The coated positive electrode active material according to claim 1, wherein the concentration of lithium carbonate in the coating decreases from the surface of the CAM towards the outside of the coating, and wherein the concentration of lithium borate decreases from the outer surface of the coating towards the surface of the CAM.

11. A method for preparing a coated positive electrode active material according to claim 1, comprising: a) determining the weight percentage of lithium carbonate in the uncoated positive electrode active material; b) Prepare a coating solution comprising a solvent, a lithium precursor, and a borate precursor, wherein the amounts of the lithium precursor and the borate precursor are calculated based on the weight percentages of Li 2+x C 1-x B x O3 and lithium carbonate from step a), where 0 < x < 0.5; c) applying the coating solution to the uncoated positive electrode active material; and d) annealing the coating solution, wherein the lithium precursor and the borate precursor are converted into lithium carbonate doped with lithium borate (LCBO), thereby obtaining the coated positive electrode active material.

12. The method according to claim 11, wherein the solvent used for preparing the coating solution is non-aqueous and is selected from the group consisting of methanol, ethanol, isopropyl alcohol, n-propanol, tert-butanol, and mixtures thereof.

13. The method according to claim 11, wherein the coating solution is annealed in an oxygen atmosphere at a temperature in the range of 150 to 600 °C for a duration in the range of 0.5 to 3 hours.

14. The method according to claim 11, wherein applying the coating solution includes spraying the coating solution onto the positive electrode active material.

15. The method according to claim 11, wherein applying the coating solution includes mixing the positive electrode active material in the coating solution.

16. A positive electrode layer comprising the coated positive electrode active material according to claim 1.

17. The positive electrode layer according to claim 16, wherein the weight percentage of the coated positive electrode active material is at least 65% of the positive electrode layer.

18. The positive electrode layer according to claim 16, which further comprises a conductive material.

19. The positive electrode layer according to claim 18, wherein the conductive material is selected from carbon fibers, vapor grown carbon fibers, carbon nanotubes, graphite fibers, and mixtures thereof.

20. The positive electrode layer according to claim 16, which further comprises a sulfur-containing inorganic electrolyte.

21. The positive electrode layer according to claim 20, wherein the sulfur-containing inorganic electrolyte is selected from the group consisting of: Li2S-P2S5, Li2S-P2S5-LiHa, Li2S-P2S5-P2O5, Li2S-Li3PO4-P2S5, Li3PS4, Li4P2S6, Li 10 GeP2S 12 、Li 3.25 Ge 0.25 P 0.75 S4、Li7P3S 11 、Li 3.25 P 0.95 S4、Li 7-x PS 6-x Ha x 、 and mixtures thereof, wherein "Ha" is more than one halogen element, and 0.2 < x < 1.

22. A all-solid-state battery (ASSB) comprising the positive electrode layer according to claim 16.

23. The ASSB according to claim 22, which further comprises an inorganic solid electrolyte layer.

24. The ASSB according to claim 23, wherein the inorganic solid electrolyte layer comprises a sulfur-containing inorganic electrolyte.

25. The ASSB according to claim 24, wherein the sulfur-containing inorganic electrolyte is selected from the group consisting of: Li2S-P2S5, Li2S-P2S5-LiHa, Li2S-P2S5-P2O5, Li2S-Li3PO4-P2S5, Li3PS4, Li4P2S6, Li 10 GeP2S 12 、Li 3.25 Ge 0.25 P 0.75 S4, Li7P3S 11 、Li 3.25 P 0.95 S4, Li 7-x PS 6-x Ha x 、and mixtures thereof, wherein "Ha" is more than one halogen element, and 0.2 < x < 1.

26. The ASSB according to claim 22, wherein the formulation of the LCBO is selected from the group consisting of: Li 2.05 C 0.95 B 0.05 O3, Li 2.10 C 0.90 B 0.10 O3, Li 2.15 C 0.85 B 0.15 O3, Li 2.25 C 0.75 B 0.25 O3 and Li 2.30 C 0.70 B 0.30 O3.

27. The ASSB according to claim 22, wherein when the ASSB is charged and discharged 20 times between 2.8 V and 4.25 V at 45 °C, at 0.1 C for cycles 1 and 2, at 0.33 C for cycles 3 and 4, at 1.0 C for cycle 5, and at 0.5 C for cycles 6 to 20, the ASSB exhibits a 20th cycle life retention rate of at least 97%, wherein each cycle is charged to 4.25 V and discharged to 2.8 V, and the 20th cycle life retention rate is the ratio of the discharge specific capacity at the 20th cycle to the initial discharge specific capacity at 0.5 C at 45 °C.

28. The ASSB according to claim 22, wherein the initial discharge specific capacity of the ASSB at 0.1 C at 45 °C is at least 190 mAh / g.

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