Cathode active material coated with f-doped lithium borosilicate and sulfide all-solid-state battery comprising same

Abstract

Disclosed herein is a cathode active material particle at least partially coated with a F-doped lithium borosilicate. In some embodiments, the F-doped lithium borosilicate has a formula of ((Li4SiO4)1-x – (Li3BO3)x)1-y—(AFm)y wherein 0 < y < 0.1, A is an alkali metal or alkaline earth metal, m is 1 or 2. In some embodiments, 0.5 < x <1.0. A cathode layer comprising the coated CAM and an all-solid-state battery (ASSB) comprising the cathode layer are also disclosed. The ASSB exhibits an improved initial discharge capacity retention at 5C and a 20th cycle stability at 0.5C.

Description

[0001]Atty Docket #: F121PCT CATHODE ACTIVE MATERIAL COATED WITH F-DOPED LITHIUM BOROSILICATE AND SULFIDE ALL-SOLID-STATE BATTERY COMPRISING SAME CROSS-REFERENCE The present application claims the benefit of US Serial No. 63 / 636,278, filed April 19, 2024, the entire content of which is incorporated herein by reference into this application TECHNICAL FIELD The present disclosure relates to a cathode active material coated with F-doped lithium borosilicate and a sulfide-based all-solid-state battery (ASSB) comprising the same. BACKGROUND All-solid-state batteries (ASSBs) are considered as promising candidates for future energy storage devices as they may enable the use of lithium metal as anode material and lead to higher specific energies compared to conventional lithium-ion batteries based on organic liquid electrolytes. Sulfide solid electrolyte (SE) materials comprise element sulfur in the -2 oxidation state (S-2) and have narrow intrinsic electrochemical windows. Thiophosphate-based solid electrolytes (SEs) contain elements phosphorus (P) and sulfur (S) and are particularly promising because of their high ionic conductivities, good mechanical compatibility, and relatively low costs. The passivation of SEs is necessary for the reversible operation of all-solid-state batteries. In particular, the adaptation of conventional high-capacity cathode active materials (CAMs) such as lithium metal oxide CAMs (ex. LiNi0.88Co0.09Al0.03O2-- NCA88) to ASSBs suffer from interfacial resistances. There are two ways to improve the compatibility with high-voltage cathodes: (1) using SEs with high-anodic limit and good interfacial stability and (2) coating protective materials on cathodes. When it comes to sulfide-based ASSBs, the S / O exchange at the CAM / SE interface and the poor ion-conducting properties of the resulting degradation compositions are of major concern. Lithium metal fluoride (LMF) type CAM coatings may offer improved electrochemical stability due to the electronegativity of fluorine and minimization of O / F and S / F atom exchange between the CAM / coating and SE / coating. However, LMF type coatings generally have lower Li ion conductivities compared to their oxide counterparts, which limits high-rate capabilities in the cell. Doping small amounts of LiF into a lithium metal oxide (LMO) glassy structure may improve Li ion conductivities of the coating while providing enhanced electrochemical stability. Thus, a new cathode active material is desired for sulfide-based ASSB batteries with improved electrochemical stability and high-rate capabilities. SUMMARY Disclosed herein is a cathode active material particle at least partially coated with a F-doped lithium borosilicate. In some embodiments, the F-doped lithium borosilicate has a formula of ((Li4SiO4)1-x– (Li3BO3)x)1-y—(AFm)ywherein A is an alkali metal or alkaline earth metal, m is 1 or 2, 0 < x < 1.0 and 0 < y < 0.1. A cathode layer comprising the coated CAM and an all-solid-state battery comprising the cathode layer are also disclosed. BRIEF DESCRIPTION OF THE DRAWINGS Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. Fig. 1 shows a representative structure of a cathode according to one embodiment of the present disclosure. Fig. 2 shows a typical structure of an all-solid-state battery (ASSB) according to one embodiment of the present disclosure. Fig. 3 shows a plot of discharge capacity retention (%) vs. cycle number at 75oC of half-cells according to one embodiment of the present disclosure. Fig. 4 shows a plot of discharge capacity retention (%) vs. cycle number at 75oC of half-cells according to one embodiment of the present disclosure. Fig. 5 shows a plot of discharge capacity retention (%) vs. cycle number at 75oC of half-cells according to one embodiment of the present disclosure. DETAILED DESCRIPTION Disclosed herein is a cathode active material particle at least partially coated with a F-doped lithium borosilicate. In some embodiments, the F-doped lithium borosilicate has a formula of ((Li4SiO4)1-x – (Li3BO3)x)1-y—(AFm)y, wherein A is an alkali metal or alkaline earth metal, wherein m is 1 or 2, and 0 < y < 0.1. In some embodiments, the coated CAM is incorporated into a cathode layer as representatively shown in Fig.1. The particles (1) of a cathode active material (CAM) are coated by a F-doped lithium borosilicate as a CAM coating layer (2). As shown in Fig. 1, a cathode layer comprises a CAM particle (1), a coating (2) around the CAM particle, an inorganic or sulfide solid electrolyte (3) and an electronically conductive carbon fiber (4). In some embodiments, the coating is a F-doped lithium borosilicate. Fig.2 shows a typical structure of an all-solid-state battery (ASSB) comprising a cathode layer (5), a solid electrolyte (6), an anode layer (7), a first current collector (8-1) in contact with the anode layer (7), and a second current collector (8-2) in contact with the cathode layer (5). In some embodiments, 0 < x < 1.0. In some embodiments, 0.5 < x < 1.0. In some embodiments, 0.6 ≤ x <1.0. In some embodiments, 0.60 ≤ x ≤ 0.95. In some embodiments, 0.60 ≤ x ≤ 0.90. In some embodiments, the F-doped lithium borosilicate has a formulation selected from the group consisting of (Li4SiO4)0.05–(Li3BO3)0.95–(LiF)y, (Li4SiO4)0.10–(Li3BO3)0.90–(LiF)y, (Li4SiO4)0.15–(Li3BO3)0.85– (LiF)y, (Li4SiO4)0.20–(Li3BO3)0.80–(LiF)y, (Li4SiO4)0.25–(Li3BO3)0.75–(LiF)y, (Li4SiO4)0.30– (Li3BO3)0.70–(LiF)y, (Li4SiO4)0.35–(Li3BO3)0.65–(LiF)y, (Li4SiO4)0.40–(Li3BO3)0.60–(LiF)y, (Li4SiO4)0.45–(Li3BO3)0.55–(LiF)yand mixtures thereof, wherein 0 < y < 0.1. In some embodiments, y has a value no less than 0.01, 0.02, or 0.03. In some embodiments, y has a value no greater than 0.07, 0.08, or 0.09. In some embodiments, 0.01≤y<0.10. In some embodiments, 0.01≤y≤0.09. In some embodiments, 0.01≤y≤0.08. In some embodiments, 0.01≤y≤0.07. In some embodiments, 0.02≤y≤0.09. In some embodiments, 0.02≤y≤0.08. In some embodiments, 0.02≤y≤0.07. In some embodiments, 0.03≤y≤0.09. In some embodiments, 0.03≤y≤0.08. In some embodiments, 0.03≤y≤0.07. In some embodiments, the F-doped lithium borosilicate has a formulation selected from the group consisting of (Li4SiO4)0.05–(Li3BO3)0.95– (LiF)0.05, (Li4SiO4)0.10–(Li3BO3)0.90–(LiF)0.05, (Li4SiO4)0.15–(Li3BO3)0.85–(LiF)0.05, (Li4SiO4)0.20– (Li3BO3)0.80–(LiF)0.05, (Li4SiO4)0.25–(Li3BO3)0.75–(LiF)0.05, (Li4SiO4)0.30–(Li3BO3)0.70–(LiF)0.05, (Li4SiO4)0.35–(Li3BO3)0.65–(LiF)0.05, (Li4SiO4)0.40–(Li3BO3)0.60–(LiF)0.05, (Li4SiO4)0.45–(Li3BO3)0.55– (LiF)0.05 and mixtures thereof. In some embodiments, the molar ratio of B to Si is important. In some embodiments, the B / Si molar ratio is higher than 1.0. In some embodiments, the B / Si molar ratio is equal to 1.5 or greater. In some embodiments, B / Si molar ratio is equal to 2.0 or greater. In some embodiments, B / Si molar ratio is no greater than 20, no greater than 15, no greater than 10, no greater than 7.5 or no greater than 5.0. In some embodiments, the B / Si molar ratio is in a range from 1.2 to 20.0, from 1.2 to 15.0, from 1.2 to 10.0, from 1.2 to 7.0, from 1.2 to 5.0, from 1.2 to 3.0, from 1.5 to 20.0, from 1.5 to 15,0, from 1.5 to 10.0, from 1.5 to 7.0, from 1.5 to 5.0 or from 1.5 to 3.0. In some embodiments, the CAM includes without limitation: LixMn1-yMyA2(Formula 1), LixMn1-yMyO2-zXz (Formula 2), LixMn2O4-zXz (Formula 3), LixMn2-yMyA4 (Formula 4), LixCo1-yMyA2(Formula 5), LixCo1-yMyO2-zXz(Formula 6), LixNi1-yMyA2(Formula 7), LixNi1-yMyO2-zXz(Formula 8), LixNi1-yCoyO2-zXz(Formula 9), LixNi1-y-zCoyMzAa, (formula 10), LixNi1-y-zCoyMzO2-aXa(Formula 11), LixNi1-y-zMnyMzAa (Formula 12), LixNi1-y-zMnyMzO2-aXa (Formula 13), LixNi1-y- zMnyMzO2 (Formula 14) and combinations thereof wherein 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 a range from about 1 µm to about 15 µm, from about 1 µm to about 12 µm, from about 1 µm to about 10 µm, from about 1 µm to about 7 µm, from about 1 µm to about 6 µm , from about 3 µm to about 15 µm, from about 3 µm to about 12 µm, from about 3 µm to about 10 µm, from about 3 µm to about 7 µm, from about 3 µm to about 6 µm, from about 5 µm to about 15 µm, from about 5 µm to about 12 µm, from about 5 µm to about 10 µm and all ranges and subranges therebetween. In some embodiments, the CAM may have a weight percentage in a range from about 50 wt% to about 99 wt%, from about 50 wt% to about 95 wt%, from about 50 wt% to about 90 wt%, from about 50 wt% to about 85 wt%, from about 50 wt% to about 80 wt%, from about 55 wt% to about 99 wt%, from about 55 wt% to about 95 wt%, from about 55 wt% to about 90 wt%, from about 55 wt% to about 85 wt%, from about 55 wt% to about 80 wt%, from about 60 wt% to about 99 wt%, from about 60 wt% to about 95 wt%, from about 60 wt% to about 90 wt%, from about 60 wt% to about 85 wt%, from about 60 wt% to about 80 wt%, from about 65 wt% to about 99 wt%, from about 65 wt% to about 95 wt%, from about 65 wt% to about 90 wt%, from about 65 wt% to about 85 wt%, from about 65 wt% to about 80 wt%, from about 70 wt% to about 99 wt%, from about 70 wt% to about 95 wt%, from about 70 wt% to about 90 wt%, from about 70 wt% to about 85 wt%, from about 70 wt% to about 80 wt%, and all range and subranges therebetween in the cathode layer. In some embodiments, the CAM particles may be polycrystalline or single crystalline. In some embodiments, the CAM particles may have a single particle size distribution or multiple particle size distributions. In some embodiments, the F-doped lithium borosilicate coating may have a thickness in a range from 0.5 nm to 20 nm, from 0.8 nm to 20 nm, from 1 nm to 20 nm, from 2 nm to 20 nm, from 4 nm to 20 nm, from 10 nm to 20 nm, from 0.5 nm to 10 nm, from 1.0 nm to 10 nm, from 2 nm to 10 nm, or from 4 nm to 10 nm. In some embodiments, the coating has a thickness in a range from 0.5 nm to 8 nm, from 0.5 nm to 5 nm, from 0.5 nm to 3 nm, from 1 nm to 8 nm, from 1 nm to 5 nm, or from 1 nm to 3 nm. In some embodiments, the thickness is measured by observing the cross section of a dissected particle using a scanning electron microscope (SEM). In some embodiments, the thickness is measured on a transmission electron microscope (TEM). In some embodiments, the electrically conductive material may be carbon fibers including but not limited to, vapor grown carbon fiber (VGCF), carbon nanotube (CNT), multi-walled carbon nanotubes (MWCNT), carbon nanofiber, and graphite fiber. In some embodiments, the electrically conductive material may have a BET measured specific surface area in a range from 1 to 600 m2 / g and / or an electrical resistance of no more than 0.5 Ω∙cm. In some embodiments, the electrically conductive material may be coated with an oxide material. In some embodiments, the electrically conductive material (coated or uncoated) has a weight percentage in a range from 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 subranges therebetween in the cathode layer. In some embodiments, a method for preparing the coated CAM is also disclosed. A coating solution is prepared by dissolving or dispersing a predetermined amount of lithium precursor such as lithium acetate, a silicon oxide precursor such as tetraethoxysilane, a boron oxide precursor such as triisopropyl borate, and a fluoride precursor such as trifluoroacetic acid in a solvent. In some embodiments, the predetermined amount of each precursor is calculated based on the formula ((Li4SiO4)1-x – (Li3BO3)x)1-y—(LiF)y, wherein 0 < x < 1.0 and 0 < y < 0.1. In some embodiments, the solvent for preparing the coating solution is a non-aqueous solvent and is selected from the group consisting of methanol, ethanol, isopropanol, n-propanol, t-butanol, tetrahydrofuran, and mixtures thereof. The coating solution can be mixed with the uncoated cathode active material to form a mixture. The solvent can be removed from the mixture to form a gel. The gel can be annealed, whereby the lithium, silicon oxide, boron oxide, and fluoride precursors form the F-doped borosilicate coating on the CAM particle surface. In some embodiments, the gel is annealed in a range from 150oC to 500oC for a duration in a range from 0.5 to 3 hours under an oxygen atmosphere. In some embodiments, the solid electrolyte used may be any sulfide solid electrolyte as long as it contains Li and S and has a desired lithium-ion conductivity. The sulfide solid electrolyte may be any of crystalline material, glass ceramic, and glass. In some embodiments, the solid electrolyte is a lithium-phosphate-sulfur (LPS) electrolyte. Examples of the sulfide solid electrolyte include Li2S- P2S5, Li2S-P2S5-LiHa ("Ha" is one or more halogen elements), Li2S-P2S5-P2O5, Li2S-Li3PO4-P2S5, Li3PS4, Li4P2S6, Li10GeP2S12, Li3.25Ge0.25P0.75S4, Li7P3S11, Li3.25P0.95S4, and Li7-xPS6-xHax(argyrodite- type solid electrolyte, "Ha" is one or more halogen elements, where 0.2 < x < 1.8). In some embodiments, the sulfide solid electrolyte may have a weight percentage in a range from 1 wt% to 35 wt%, from 1 wt% to 30 wt%, from 1 wt% to 25 wt%, from 1 wt% to 20 wt%, from 1 wt% to 15wt%, 1 wt% to 10 wt%, from 5 wt% to 35 wt%, from 5 wt% to 30 wt%, from 5 wt% to 25 wt%, from 5 wt% to 20 wt%, from 5 wt% to 15 wt%, from 10 wt% to 35 wt%, from 10 wt% to 30 wt%, from 10 wt% to 25 wt%, from 10 wt % to 20 wt%, from 15 wt% to 35 wt%, from 15 wt% to 30 wt%, from 15 wt% to 25 wt%, from 20 wt% to 30 wt% and any and all ranges and subranges therebetween in the cathode layer. In some embodiments, the cathode layer is sandwiched between a cathode current collector and the solid electrolyte layer. In some embodiments, the cathode layer includes a cathode active material (CAM) that requires both lithium ion (Li+) and electron (e-) connectivity with the solid electrolyte layer and current collector, respectively. The Li+connectivity is mainly provided by small particles of sulfide-based solid electrolyte in the cathode layer, and the e- connectivity is mainly provided by the electrically conductive material. The sulfide-based solid electrolytes (such as the exemplary sulfide solid electrolyte set forth above) have a high Li+conductivity. However, they generally degrade at potentials below 1.7 V or above 2.1 V vs. Li / Li+at the CAM / SE, carbon fiber (CF) / SE, and current collector / SE interface. The degraded byproducts generally have a lower Li+ conductivity, which in return requires a higher percentage of SE in the cathode composite layer, leading to a lower percentage of CAM. Without wishing to be bound by theory, the F-doped lithium borosilicate coating disclosed herein prolongs the time for degradation, maintains a relatively higher Li+conductivity, and thus improves the overall battery cell performance. The cathode layer disclosed above can be incorporated into an all-solid-state battery. As shown for example in Fig. 2, the cathode layer 5 can act as a positive electrode in the all-solid-state battery (ASSB) and the all-solid-state-battery may also include a negative electrode (or anode layer) 7 and a solid electrolyte layer 6 between the cathode layer 5 and the negative electrode 7. In some embodiments, the solid electrolyte of the solid electrolyte layer may 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, for example 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, Li10GeP2S12, Li3.25Ge0.25P0.75S4, Li7P3S11, Li3.25P0.95S4, and Li7-xPS6-xHax(argyrodite-type solid electrolyte, “Ha” is one or more halogen elements, where 0.2 < x < 1.8). In some embodiments, the ASSB has an initial discharge specific capacity of at least 200 mAh / g or at least 205 mAh / g at a charge / discharge rate of 0.1C. In some embodiments, the ASSB has an initial discharge specific capacity of at least 200 mAh / g or at least 205 mAh / g at a charge / discharge rate of 0.33C. In some embodiments, the ASSB has an initial discharge capacity retention at 5C of at least 84%, 84.5%, or 85%, wherein the initial discharge capacity retention at 5C is calculated by dividing the initial discharge capacity at 5C by the initial discharge capacity at 0.1C. In some embodiments, the ASSB has a 20thcycle stability at 0.5C of at least 98%, 98.5%, or 99%, wherein the 20thcycle stability at 0.5C is calculated by dividing the discharge capacity retention of the 20thcycle at 0.5C by the discharge capacity retention of the 1stcycle of cycle-life test at 0.5C. discharge capacity retention of the 1stcycle of cycle-life test at 0.5C is calculated by dividing the discharge capacity of the 1stcycle of the cycle-life test by the initial discharge capacity at 0.1C. The 20thcycle-life capacity retention is calculated by dividing the discharge capacity of the 20thcycle at 0.5C by the discharge capacity of the initial discharge capacity at 0.1C. In some embodiments, the ASSB has a 20thcycle-life capacity retention of at least 94.0%, at least 94.5%, or at least 95.0%. The disclosure will be better understood by reference to the Experimental Details which follow, but those skilled in the art will readily appreciate that the specific experiments detailed are only illustrative, and are not meant to limit the disclosure as described herein, as numerous variations and modifications of these exemplary embodiments are possible without undue experimentation. All such variations and modifications are within the scope of the teachings of this disclosure. It will be appreciated that the foregoing description and following examples, no matter how detailed they may appear in text, the disclosure may be practiced in many ways, and the disclosure should be construed in accordance with the appended claims and equivalents thereof. EXAMPLE 1 A coating solution was prepared by dissolving lithium acetate as lithium precursor, tetraethoxysilane as silicon oxide precursor, and triisopropyl borate as boron oxide precursor in anhydrous ethanol or tetrahydrofuran as solvent. A predetermined amount of the coating solution was then mixed with CAM particles, wherein the predetermined amount is calculated given a desired coating thickness using the BET surface area of the CAM and an estimated coating density of 2.311g / cm3. The mixing lasted for 30 minutes followed by solvent removal via vacuum while being sonicated, leading to a gel of CAM coated with the lithium borosilicate. The gel was then annealed for 1 hour at 400oC under an oxygen flow to form the lithium borosilicate coated CAM particles. In this example, the CAM coating contains no fluorine (F) and the CAM coating formula can be described as ((Li4SiO4)1-x(Li3BO3)x), wherein 0≤x≤1. A cathode layer comprising 65wt% uncoated or coated LiNi0.88Co0.09Al0.03O2 (NCA88) as CAM, 5wt% carbon fiber (VGCF), and 30wt% lithium phosphorus sulfur chloride (LPSCl) (Li6PS5Cl) was prepared. The cathode layers were electrochemically evaluated in torque-cells using Li metal on copper as the anode and Li6PS5Cl (LPSCl) as SE. The cells were cycled at 75oC from 2.5V to 4.25V at 0.1C charge / discharge for cycles 1 and 2, 0.33C charge / discharge for cycles 3 and 4, 0.5C charge / discharge for cycles 5 and 6, 1C charge / discharge for cycles 7 and 8, 2C charge / discharge for cycles 9 and 10, 5C charge / discharge for cycles 11 and 12, and 0.5C charge / discharge for cycles 13 to 32. The initial capacity retentions at 0.33C, 0.5C, 1C, 2C and 5C are calculated by dividing the discharge capacities at 0.33C, 0.5C, 1C, 2C and 5C by the initial discharge capacity at 0.1C, respectively. The 20thcycle stability at 0.5C is calculated from the 20thcycle-life discharge capacity retention at 0.5C divided by the 1stcycle-life discharge capacity retention at 0.5C. As representatively shown in Fig. 3, the 1stand 20thcycle-life discharge capacity retention at 0.5C are cycle no. 13 and 32, respectively. Note that cycles no. 5 and 6 were tested at 0.5C as part of the rate test but not part of the cycle-life test for the calculation of cycle-life discharge capacity retention and cycle stability. The initial specific discharge capacities and capacity retention of the various lithium borosilicate coatings are summarized in Table 1. Fig. 3 shows a plot of cell discharge capacity retention (%) vs. cycle number at 75oC of half-cells comprising uncoated CAM or coated CAM with a lithium borosilicate with different boron contents, i.e., x = 0, 0.3, 0.5, 0.6, 0.7, 0.9 and 1.0 and without F dopant. (i.e., y = 0). The coating has a thickness of approximately 3 nm. When x has a value of 0.3, 0.5, 0.6, 0.7 and 0.9, the B / Si molar ratio is 3 / 7, 1 / 1, 6 / 4, 7 / 3, and 9 / 1, respectively. As shown in Table 1, all examples exhibited an initial discharge specific capacity of at least 200 mAh / g at a rate of 0.1C. Kinetic performance is important for high-rate performance such as fast charge or discharge of an electrochemical device and can be representatively shown by its initial discharge capacity retention at elevated C rates greater than 1C, such as 5C. A cell comprising uncoated CAM exhibited an initial discharge capacity retention at 5C of around 62.8%. It is much lower than those comprising lithium borosilicate coated CAM as shown in Table 1, which are higher than 80% or even higher than 84%. Cycle-life stability is important for cycling performance of an electrochemical device and can be typically measured by 20thcycle stability at 0.5C. As shown in Table 1, a cell comprising uncoated CAM exhibited a 20thcycle stability at 0.5C of around 70%. In contrast, the cell comprising a lithium borosilicate coated CAM exhibited an improved cycle stability higher than 90%, 95% or even higher than 98%. Table 1 Initial discharge (dChg.) specific capacity (Cap.), capacity retention, cycle-life capacity retention and 20thcycle stability at 75oC and different C-rates for half-cells comprising uncoated (U.C.) and lithium borosilicate coated CAM. U.C. x = 0.0 x = 0.3 x = 0.5 x = 0.6 x = 0.7 x = 0.9 x = 1.0 Initial dChg. Cap. @ 21098 21791 20203 21148 21179 20706 22186 21554 2 5 6 7 1 4 5 9 It is well known that it is highly challenging to simultaneously achieve both a high initial 5C discharge capacity retention and a high 20thcycle stability. Among all the examples without F-dopant, a coating of the lithium borate (Li3BO3) exhibited the best overall performance with an initial 0.1C dChg specific capacity of 215.5 mAh / g, an initial dChg specific capacity retention of 89.01% and a 20thcycle stability of 99.29% at 5C. EXAMPLE 2 A coating solution was prepared by following Example 1 except that lithium fluoride was incorporated into the solution with a molar amount of 5%, i.e., y=0.05. F-doped lithium borosilicate coated CAM particles were similarly prepared by using the coating solution. In this example, the CAM coating can be described as ((Li4SiO4)1-x(Li3BO3)x)1-y-(LiF)y, wherein 0≤x≤1.0, and y=0.05. The initial specific discharge capacities and capacity retention of cells comprising various F- doped lithium borosilicate coatings with y = 0.05 were tested according to the method in Example 1 and the results are summarized in Table 2. Fig. 4 shows a plot of cell discharge capacity retention (%) vs. cycle number at 75oC of half-cells comprising NCA88 coated with a F-doped lithium borosilicate with different boron contents, i.e., x = 0, 0.3, 0.5, 0.6, 0.7, 0.9 and 1.0, wherein the dopant is 5 mol% LiF, i.e., y=0.05. Note when x is 0, the coating is a F-doped lithium silicate ((Li4SiO4)0.95--(LiF)0.05) and when x is 1, the coating is a F-doped lithium borate, i.e., (Li3BO3)0.95-(LiF)0.05 in this example. Table 2 Initial dChg specific capacity, capacity retention, cycle-life capacity retention and 20thcycle stability at 75oC and different C-rates for half-cells comprising F-doped lithium borosilicate coated CAM for y = 0.05. x = 0.0 x = 0.3 x = 0.5 x = 0.6 x = 0.7 x=0.9 x = 1.0 2 By comparing Table 2 to Table 1, when 0≤x≤0.5, the incorporation of 5 mol% fluoride dopant i.e., y=0.05, improved the 20thcycle stability of each composition at 0.5C but decreased the initial discharge capacity retention at 5C. When 0.5 <x<1.0, more particularly when x is 0.6, 0.7, or 0.9, the incorporation of 5 mol% fluoride dopant simultaneously improved the 20thcycle stability at 0.5C and the initial discharge capacity retention at 5C. The result was unexpected. When x has a value of 1.0, the incorporation of 5 mol% fluoride dopant reduced the 20thcycle stability at 0.5C from 99.29% to 98.18% and the initial discharge capacity retention at 5C from 89.01% to 85.74%. Among all the examples in Table 2, the cell comprising a cathode comprising a CAM coated with ((Li4SiO4)0.1(Li3BO3)0.9)0.95-(LiF)0.05 exhibited an initial discharge capacity retention of 89.37% at 5C and a 20thcycle stability of 99.90% at 0.5C, each of which is higher than the best result in Table 1, particularly the one coated with lithium borate (Li3BO3, x=1.0 and y=0) . The cell comprising a cathode comprising CAM coated with ((Li4SiO4)0.3(Li3BO3)0.7)0.95-(LiF)0.05 exhibited an initial discharge capacity retention of 87.13% at 5C and a 20thcycle stability of 100.06% at 0.5C. EXAMPLE 3 A coating solution was prepared by following Example 1 except that lithium fluoride was incorporated into the solution with a molar amount of 10%, i.e., y=0.1. The F-doped lithium borosilicate coated CAM particles were similarly prepared by using the coating solution. In this example, the CAM coating can be described as ((Li4SiO4)1-x(Li3BO3)x)1-y-(LiF)y, wherein 0≤x≤1.0, and y=0.10. Table 3 Initial dChg specific capacity, capacity retention, cycle-life capacity retention and 20thcycle stability at 75oC and different C-rates for half-cells comprising F-doped lithium borosilicate coated CAM for y = 0.10. x = 0.0 x = 0.3 x = 0.5 x = 0.6 x = 0.7 x = 0.9 x = 1.0 3 The initial specific discharge capacities and capacity retention of the various F-doped lithium borosilicate coatings with y = 0.10 were similarly tested following the method in Example 1 and the results are summarized in Table 3. Fig. 5 shows a plot of cell discharge capacity retention (%) vs. cycle number at 75oC of half-cells comprising NCA88 coated with a F-doped lithium borosilicate with different boron contents, i.e., x = 0, 0.3, 0.5, 0.6, 0.7, 0.9 and 1.0, wherein the dopant is 10 mol% LiF, i.e., y=0.10. When x is 0, the coating is an F-doped lithium silicate, i.e., (Li4SiO4)0.90-(LiF)0.10 in this example. When x is 1.0, the coating is an F-doped lithium borate, i.e., (Li3BO3)0.95-(LiF)0.05in this example. By comparing Table 3 to Table 2, when x is 0, a 10 mol% fluoride dopant into the CAM coating increased the initial 5C discharge capacity retention from 85.88% to 86.7% while decreased the 20thcycle stability at 0.5C from 99.86% to 98.19%. When 0 < x ≤ 0.5, a 10 mol% fluoride dopant into the CAM coating led to a decreased or similar initial discharge capacity retention at 5C while a decreased 20thcycle stability at 0.5C. When 0.5 <x<1.0, incorporation of 10 mol% fluoride dopant into the CAM coating reduced the initial discharge capacity retention at 5C and also the 20thcycle stability at 0.5C. When x is 1.0, incorporation of 10 mol% fluoride dopant into the CAM coating increased the initial discharge capacity retention at 5C from 85.74% to 88.65% but decreased the 20thcycle stability at 0.5C from 98.18% to 97.76%. Table 4-1 Initial dChg specific capacity, retention and cycle stability at different C rates when x=0 y=0 y=0.05 y=0.10 Among all the examples in Table 3, the cell comprising a cathode comprising CAM coated with (Li3BO3)0.9-(LiF)0.1exhibited a highest initial 5C discharge capacity retention of 88.65% and a 20thcycle stability of 97.76%. Among all the examples in Table 2, the cell comprising a cathode containing CAM coated with ((Li4SiO4)0.1(Li3BO3)0.9)0.95-(LiF)0.05, i.e., x=0.9 and y=0.05 exhibited a highest initial 5C discharge capacity retention of 89.37% and a 20thcycle stability of 99.90%, which is better than the one in Table 3. It demonstrates that the CAM coating composition is important and the incorporation of Si and F is critically important to simultaneously achieve a desirable high rate performance and high cycling performance. Table 4-2 Initial dChg specific capacity, retention and cycle stability at different C rates when x=0.3 (molar ratio of B / Si is 3 / 7) y=0 y=0.05 y=0.10 Initial dCh Ca @ 01C (mAh / ) 20203 21914 21102 The influence of the amount of fluoride on the electrochemical performance was also studied, particularly when the value of x is fixed. The result of x = 0 (B / Si with a molar ratio of 0) is summarized in Table 4-1. It shows that incorporation of fluoride into the CAM coating decreased the initial discharge capacity retention at 5C. It also shows that 5 mol% F (y=0.05) achieved the highest 20thcycle stability at 0.5C while an F-dopant at either too low (y=0) or too high (y=0.1) concentration may decrease the cycle stability. When x is greater than 0 and no greater than 1.0, e.g., x=0.3 (B / Si = 3 / 7) and x =0.5 (B / Si = 1 / 1), the results are summarized in Tables 4-2 and 4-3. It shows that incorporation of fluoride into the CAM coating decreased the initial discharge capacity retention at 5C but achieved a similar 20thcycle stability at 0.5C only when fluoride is a selected range, e.g., when y=0.05. Excessive fluoride, e.g., y=0.1, decreased both characteristics. Table 4-3 Initial dChg specific capacity, retention and cycle stability at different C rates when x=0.5 (molar ratio of B / Si is 1 / 1) y=0 y=0.05 y=0.10 Initial dChg. Cap. @ 0.1C (mAh / g) 211.48 208.49 208.30 en x s g er an . an ower an . , .e., x = . ( / = / ), . ( / = 7 / 3) and 0.9 (B / Si = 9.0), the results are summarized in Tables 4-4, 4-5 and 4-6. It shows that the incorporation of 5 mol% fluoride into the CAM coating simultaneously increased the initial discharge capacity retention at 5C and the 20thcycle stability at 0.5C. The results were unexpected. When the fluoride amount is high, e.g., y=0.1, both characteristics are less desired. Table 4-4 Initial dChg specific capacity, retention and cycle stability at different C rates when x=0.6 (molar ratio of B / Si is 6 / 4) y=0 y=0.05 y=0.10 Table 4-5 Initial dChg specific capacity, retention and cycle stability at different C rates when x=0.7 (molar ratio of B / Si is 7 / 3) y=0 y=0.05 y=0.10 Initial dChg. Cap. @ 0.1C (mAh / g) 207.06 216.09 219.47 Table 4 - n a g spec c capac y, re en on an cyc e s a y a eren ra es when x=0.9 (molar ratio of B / Si is 9 / 1) y=0 y=0.05 y=0.10 When x has a value of 1.0, i.e., the coating is an F-doped lithium borate, (Li3BO3)1-y-(LiF)y, the results are summarized in Table 4-7. It shows that incorporation of 5 mol% fluoride into the CAM coating decreased the initial 5C discharge capacity retention and the 20thcycle stability. Incorporation of 10 mol% fluoride resulted in an even worse result. It suggests that the CAM coating comprising lithium silicate (x<1.0) is desired. Table 4-7 Initial dChg specific capacity, retention and cycle stability at different C rates when x=1.0 y=0 y=0.05 y=0.10 Initial dChg. Cap. @ 0.1C (mAh / g) 215.54 216.92 211.53 In s , p g p y role. In some embodiments, the CAM coating has a formula of ((Li4SiO4)1-x(Li3BO3)x)1-y-(LiF)y, wherein 0.5 < x < 1.0, and 0<y<0.1. In some embodiments, 0.6 ≤ x < 1.0. In some embodiments, 0.6 ≤ x ≤ 0.9. In some embodiments, 0.01 ≤ y ≤ 0.08. In some embodiments, 0.02 ≤ y ≤ 0.08. In some embodiments, 0.03 ≤ y ≤ 0.08. ASPECTS In a first aspect of the disclosure, a coated cathode active material comprising particle of a cathode active material (CAM) and a coating on the particle, wherein the coating is a F-doped lithium borosilicate, wherein the F-doped lithium borosilicate has a formula of ((Li4SiO4)1-x–(Li3BO3)x)1-y– (AFm)yand 0 < y < 0.10, wherein A is an alkali metal or alkaline earth metal, wherein m is 1 or 2. In a second aspect according to the first aspect, 0.5 < x < 1.0. In some embodiments, 0.6 ≤ x < 1.0. In a third aspect according to any preceding aspect, A is at least one selected from the group consisting of Li, Na, K, Rb, Be, Mg, Ca, and Sr. In a fourth aspect according to any preceding aspect, the coating has a thickness in a range from 1 to 10 nm. In a fifth aspect according to any preceding aspect, 0.03 ≤ y ≤ 0.08. In a sixth aspect according to any preceding aspect, a molar ratio of B / Si in the formula has a value in a range from 1.5 to 20.0. In some embodiments, the molar ratio of B / Si is in a range from 1.2 to 20.0, from 1.2 to 15.0, from 1.2 to 10.0, from 1.2 to 7.0, from 1.2 to 5.0, from 1.2 to 3.0, from 1.5 to 20.0, from 1.5 to 15,0, from 1.5 to 10.0, from 1.5 to 7.0, from 1.5 to 5.0 or from 1.5 to 3.0. In a seventh aspect according to any preceding aspect, the F-doped lithium borosilicate has a formulation selected from the group consisting of ((Li4SiO4)0.05–(Li3BO3)0.95)1-y–(LiF)y, ((Li4SiO4)0.10–(Li3BO3)0.90)1-y–(LiF)y, ((Li4SiO4)0.15–(Li3BO3)0.85)1-y–(LiF)y, ((Li4SiO4)0.20– (Li3BO3)0.80)1-y–(LiF)y, ((Li4SiO4)0.25–(Li3BO3)0.75)1-y–(LiF)y, ((Li4SiO4)0.30–(Li3BO3)0.70)1-y–(LiF)y, ((Li4SiO4)0.35–(Li3BO3)0.65)1-y–(LiF)y, ((Li4SiO4)0.40–(Li3BO3)0.60)1-y–(LiF)y, ((Li4SiO4)0.45– (Li3BO3)0.55)1-y–(LiF)y and mixtures thereof, wherein 0 < y < 0.1. In some embodiments, the F-doped lithium borosilicate has a formulation selected from the group consisting of ((Li4SiO4)0.05– (Li3BO3)0.95)0.95–(LiF)0.05, ((Li4SiO4)0.10–(Li3BO3)0.90)0.95–(LiF)0.05, ((Li4SiO4)0.15–(Li3BO3)0.85)0.95– (LiF)0.05, ((Li4SiO4)0.20–(Li3BO3)0.80)0.95–(LiF)0.05, ((Li4SiO4)0.25–(Li3BO3)0.75)0.95–(LiF)0.05, ((Li4SiO4)0.30–(Li3BO3)0.70)0.95–(LiF)0.05, ((Li4SiO4)0.35–(Li3BO3)0.65)0.95–(LiF)0.05, ((Li4SiO4)0.40– (Li3BO3)0.60)0.95–(LiF)0.05, ((Li4SiO4)0.45–(Li3BO3)0.55)0.95–(LiF)0.05and mixtures thereof. In some embodiments, the particle is either polycrystalline or single crystalline and has an average diameter of 1-15µm. In some embodiments, the CAM is selected from the group consisting of LixMn1-yMyA2, LixMn1-yMyO2-zXz, LixMn2O4-zXz, LixMn2-yMyA4, LixCo1-yMyA2, LixCo1-yMyO2-zXz, LixNi1-yMyA2, LixNi1-yMyO2-zXz, LixNi1-yCoyO2-zXz, LixNi1-y-zCoyMzAa, LixNi1-y-zCoyMzO2-aXa, LixNi1-y-zMnyMzAa, LixNi1-y-zMnyMzO2-aXa, and mixtures thereof, wherein 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 an eighth aspect according to the first aspect, a method for preparing the coated cathode active material may comprise: a) preparing a coating solution comprising a predetermined amount of a lithium precursor, silicon oxide precursor, boron oxide precursor, and fluoride precursor, in a solvent, b) mixing the coating solution with an uncoated cathode active material into a mixture, c) removing the solvent from the mixture, leading to a gel, wherein a coating of gel is formed on the CAM, and d) annealing the gel in an oxygen atmosphere, wherein the lithium precursor, silicon oxide precursor, boron oxide precursor, and fluoride precursor are converted into a F-doped lithium borosilicate, thereby obtaining a coated cathode active material. In some embodiments, the solvent for preparing the coating solution is non-aqueous and is selected from the group consisting of methanol, ethanol, isopropanol, n-propanol, t-butanol, tetrahydrofuran, and mixtures thereof. In some embodiments, the gel is annealed in a range from 150 to 500oC for a duration in a range from 0.5 to 3 hours under an oxygen atmosphere. In a nineth aspect, the present disclosure provides a cathode layer comprising the coated cathode active material according to any of the first through seventh aspects, wherein the coated cathode active material has a percentage of at least 65wt% in the cathode layer. In a tenth aspect according to the nineth aspect, the cathode layer further comprises an electrically conductive material and a sulfur-containing inorganic electrolyte, 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, Li10GeP2S12, Li3.25Ge0.25P0.75S4, Li7P3S11, Li3.25P0.95S4, Li7-xPS6-xHax, and mixtures thereof wherein “Ha” is one or more halogen elements, and 0.2 < x < 1. In some embodiments, the electrically conductive material is selected from carbon fiber, vapor growth carbon fiber, carbon nanotube, graphite fiber, and mixtures thereof. In an eleventh aspect, the present disclosure provides an all-solid-state battery (ASSB) comprising the cathode layer according to the nineth or tenth aspect. In a twelfth aspect, the ASSB further comprises an inorganic solid electrolyte layer. In a thirteenth aspect according to the twelfth aspect, the inorganic solid electrolyte layer comprises a sulfur-containing inorganic electrolyte. 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, Li10GeP2S12, Li3.25Ge0.25P0.75S4, Li7P3S11, Li3.25P0.95S4, Li7-xPS6-xHax, and mixtures thereof, wherein "Ha" is one or more halogen elements, and 0.2 < x < 1. In a fourteenth aspect according to the twelfth or thirteenth aspect, the ASSB possesses at least one characteristic of the following: ^ an initial discharge specific capacity of at least 200 mAh / g at 0.1C; ^ an initial discharge capacity retention of at least 84% at 5C; and ^ a 20thcycle stability of at least 98% at 0.5C, wherein the initial discharge capacity retention at 5C is calculated by dividing the initial discharge capacity at 5C by the initial discharge capacity at 0.1C, and the 20thcycle stability at 0.5C is calculated by dividing the discharge capacity retention of the 20th cycle at 0.5C by the discharge capacity retention of the 1stcycle at 0.5C. In a fifteenth aspect according to the thirteenth or fourteenth aspect, the ASSB possesses an initial discharge capacity retention at 5C higher than an ASSB comprising a coating undoped with F. In some embodiments, the ASSB possesses a 20thcycle stability at 0.5C higher than an ASSB comprising a coating undoped with F. Various embodiments of the features of this disclosure are described herein. However, it should be understood that such embodiments are provided merely by way of example, and numerous variations, changes, and substitutions can occur to those skilled in the art without departing from the scope of this disclosure. It should also be understood that various alternatives to the specific embodiments described herein are also within the scope of this disclosure.

Claims

We claim:

1. A coated cathode active material comprising particle of a cathode active material (CAM) and a coating on the particle, wherein the coating is a F-doped lithium borosilicate, wherein the F- doped lithium borosilicate has a formula of ((Li4SiO4)1-x–(Li3BO3)x)1-y–(AFm)y and 0 < y < 0.10, wherein A is an alkali metal or alkaline earth metal, wherein m is 1 or 2.

2. The coated cathode active material of claim 1, wherein 0.5 < x < 1.

0.

3. The coated cathode active material of any preceding claim, wherein A is at least one selected from the group consisting of Li, Na, K, Rb, Be, Mg, Ca, and Sr.

4. The coated cathode active material of any preceding claim, wherein the coating has a thickness in a range from 1 nm to 10 nm.

5. The coated cathode active material of any preceding claim, wherein 0.01 ≤ y ≤ 0.

08.

6. The coated cathode active material of any preceding claim, wherein the formula has a molar ratio of B / Si in a range from 1.5 to 20.

0.

7. The ASSB of any preceding claim, wherein the F-doped lithium borosilicate has a formulation selected from the group consisting of ((Li4SiO4)0.05–(Li3BO3)0.95)1-y–(LiF)y, ((Li4SiO4)0.10– (Li3BO3)0.90)1-y–(LiF)y, ((Li4SiO4)0.15–(Li3BO3)0.85)1-y–(LiF)y, ((Li4SiO4)0.20–(Li3BO3)0.80)1-y– (LiF)y, ((Li4SiO4)0.25–(Li3BO3)0.75)1-y–(LiF)y, ((Li4SiO4)0.30–(Li3BO3)0.70)1-y–(LiF)y, ((Li4SiO4)0.35–(Li3BO3)0.65)1-y–(LiF)y, ((Li4SiO4)0.40–(Li3BO3)0.60)1-y–(LiF)y, ((Li4SiO4)0.45– (Li3BO3)0.55)1-y–(LiF)y and mixtures thereof, wherein 0 < y < 0.

1.

8. A method for preparing coated cathode active material of claim 1, comprising: a) preparing a coating solution comprising a predetermined amount of a lithium precursor, silicon oxide precursor, boron oxide precursor, and fluoride precursor, in a solvent, b) mixing the coating solution with an uncoated cathode active material into a mixture, c) removing the solvent from the mixture, leading to a gel, wherein a coating of gel is formed on the CAM, andd) annealing the gel in an oxygen atmosphere, wherein the lithium precursor, silicon oxide precursor, boron oxide precursor, and fluoride precursor are converted into a F-doped lithium borosilicate, thereby obtaining a coated cathode active material.

9. A cathode layer comprising the coated cathode active material of any of claims 1 through 7 with a percentage of at least 65wt% in the cathode layer.

10. The cathode layer of claim 9, further comprising an electrically conductive material and a sulfur-containing inorganic electrolyte, 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, Li10GeP2S12, Li3.25Ge0.25P0.75S4, Li7P3S11, Li3.25P0.95S4, Li7-xPS6- xHax, and mixtures thereof wherein “Ha” is one or more halogen elements, and 0.2 < x < 1 11. An all-solid-state battery (ASSB) comprising the cathode layer of claim 9 or 10.

12. The ASSB of claim 11, further comprising an inorganic solid electrolyte layer.

13. The ASSB of claim 12, wherein the inorganic solid electrolyte layer comprises a sulfur- containing inorganic electrolyte, 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, Li10GeP2S12, Li3.25Ge0.25P0.75S4, Li7P3S11, Li3.25P0.95S4, Li7-xPS6-xHax, and mixtures thereof wherein “Ha” is one or more halogen elements, and 0.2 < x < 1 14. The ASSB of any of claims 11 through 13, wherein the ASSB possesses at least one characteristic of the following: ^ an initial discharge specific capacity of at least 200 mAh / g at 0.1C; ^ an initial discharge capacity retention of at least 84% at 5C; ^ a 20thcycle-life capacity retention of at least 94.0% at 0.5C; and ^ a 20thcycle stability of at least 98% at 0.5C, wherein the initial discharge capacity retention at 5C is calculated by dividing the initial discharge capacity at 5C by the initial discharge capacity at 0.1C, the 20thcycle-lifecapacity retention is calculated by dividing the discharge capacity of the 20thcycle at 0.5C by the initial discharge capacity at 0.1C, and the 20thcycle stability is calculated by dividing the 20thcycle-life capacity retention at 0.5C by the 1stcycle-life capacity retention at 0.5C.

15. The ASSB of claim 13 or 14, wherein the ASSB possesses an initial discharge capacity retention at 5C higher than an ASSB comprising a coating undoped with F.

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