Modified high-nickel positive electrode material, preparation method thereof and lithium ion battery

Abstract

The application discloses a modified high-nickel positive electrode material, a preparation method thereof and a lithium ion battery, and relates to the technical field of lithium ion batteries. ‑ , PO4 3‑ Multi-anions are introduced into the lithium borate lattice together, and a high-entropy multi-anion coating layer is successfully constructed. The coating layer has extremely high configuration entropy and chemical disorder degree, can effectively inhibit the crystallization trend of the coating in the long-term cycle process, can make the coating persistently keep amorphous state, and thus can provide a long-term stable lithium ion transmission channel. The doping of mixed transition metal ions introduces a large number of lithium ion vacancies in the coating, and in combination with the synergistic effect of multi-anions, the room-temperature ionic conductivity is improved by several orders of magnitude compared with conventional fast ionic conductors, and the interface charge transfer impedance between the positive electrode and the sulfide electrolyte is significantly reduced. The modified high-nickel positive electrode material prepared by the application can realize significant improvement in long-cycle stability in a sulfide solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a modified high-nickel cathode material, its preparation method, and a lithium-ion battery. Background Technology

[0002] High-nickel cathode materials generally refer to layered ternary cathodes (NCMNCA) with a nickel content of 80%. Their core advantages are high energy density, high specific capacity, and low cobalt cost, making them the mainstream choice for long-range electric vehicles. However, the chemical potential mismatch, thermodynamic instability, and concentration gradient-driven solid-state diffusion between the high-nickel cathode and the solid electrolyte can lead to the formation of a space charge layer, an inert layer resulting from severe side reactions under high voltage, and lattice disruption due to elemental interdiffusion. These problems collectively cause a sharp increase in interfacial impedance and rapid capacity decay, becoming the main bottleneck restricting their long-cycle stability.

[0003] To address the aforementioned issues, existing technologies primarily employ coating methods. Most current coating layers utilize fast ion conductors; however, conventional fast ion conductors (such as Li3BO3 and Li2ZrO3) have a room-temperature ionic conductivity of only 10. -7 ~10 -6 The S / cm ratio is far lower than that of sulfide electrolytes. Coating prevents rapid ion transport between the cathode and electrolyte, resulting in a significant increase in interfacial charge transfer resistance and limiting the rate performance and capacity of solid-state batteries.

[0004] Furthermore, the coating layer is mostly crystalline, resulting in rigid contact and making uniform coating difficult. Common fast ion conductors are mostly crystalline structures, forming a "hard contact" with the cathode particles. They lack mechanical flexibility, cannot tightly adhere to the cathode surface, and are prone to coating defects or discontinuous layers. At the same time, crystalline materials are difficult to achieve uniform and complete nanoscale coating on the cathode surface, and cannot effectively suppress the side reactions between residual alkali and sulfide electrolyte, leading to a continuous deterioration of interfacial stability.

[0005] Therefore, there is an urgent need to optimize the coating of high-nickel cathode materials in order to achieve a significant improvement in both long-cycle stability and high-rate performance in sulfide solid-state batteries.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a modified high-nickel cathode material, its preparation method, and a lithium-ion battery, aiming to achieve a significant improvement in both long-cycle stability and high-rate performance in sulfide solid-state batteries.

[0008] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a modified high-nickel cathode material, comprising: A sol is formed by mixing lithium alkoxide, borate ester, transition metal alkoxide, solvent and complexing agent; wherein the metal element in the transition metal alkoxide is selected from four to six of Ti, Nb, Zr, Ta, Mo, W, V and Y; The sol was mixed with fluoride and phosphate ester, aged, and dried to obtain a dry gel; The dry gel was ground and then sintered to obtain high-entropy multi-anionic lithium borate powder; High-entropy multi-anion lithium borate powder was mixed with high-nickel cathode material and then annealed.

[0009] In an optional embodiment, during the preparation of high-entropy multi-anionic lithium borate powder, the molar ratio of Li, B, F and P is controlled to be 1.5:(0.9-1.1):(0.2-0.4):(0.1-0.3), and the crystallinity of the lithium borate powder is 40-70%. And / or, the molar ratio of Li to each transition metal element is 1.5:(0.10-0.25). And / or, the molar ratio of Li to the total amount of transition metals is 1.5:(0.8-1.2).

[0010] In an optional embodiment, the transition metal alkoxide is selected from four to six of the following: titanium alkoxide, niobium alkoxide, zirconium alkoxide, tantalum alkoxide, molybdenum alkoxide, tungsten alkoxide, vanadium alkoxide, and yttrium alkoxide. The titanium alkoxide is selected from at least one of tetraethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate; The niobium alkoxide is selected from at least one of niobium ethanol, niobium propoxide, and niobium butoxide; The zirconium alkoxide is selected from at least one of zirconium n-propoxide, zirconium isopropoxide, and zirconium n-butoxide; The tantalum alkoxide is selected from at least one of tantalum ethoxide, tantalum propoxide, tantalum butoxide, and tantalum isopropoxide; Molybdenum alkoxide is molybdenum ethanol; Tungsten alkoxide is selected from at least one of tungsten ethoxide and tungsten isopropoxide; The vanadium alkoxide is selected from at least one of vanadium ethoxide and vanadium triisopropoxide; The yttrium alkoxide is selected from at least one of yttrium butoxide and yttrium isopropoxide.

[0011] In an optional embodiment, the lithium ethanol is selected from at least one of lithium methoxide, lithium ethanol, lithium isopropoxide, lithium n-butoxide, and lithium tert-butoxide. And / or, the borate ester is selected from at least one of trimethyl borate, triethyl borate, triisopropyl borate and tri-n-butyl borate; And / or, the fluoride is selected from at least one of lithium fluoride, ammonium fluoride and trifluoroacetic acid; And / or, the phosphate ester is selected from at least one of trimethyl phosphate, triethyl phosphate, tributyl phosphate and trioctyl phosphate.

[0012] In an optional embodiment, the solvent is selected from at least one of methanol, tetrahydrofuran, ethanol, isopropanol, and ethylene glycol monomethyl ether; And / or, the complexing agent is selected from at least one of citric acid, ethylene glycol, oxalic acid, tartaric acid and acrylic acid; the molar ratio of the complexing agent to the metal ion is 0.5:1-4:1; In an optional embodiment, during the preparation of the sol, the stirring temperature is controlled at 50℃-70℃ and the stirring time is 1h-3h. And / or, during the preparation of the dry gel, the aging time is controlled to be 6h-24h, the drying temperature is 120℃-180℃, and the drying time is 2h-6h; And / or, after grinding the dry gel for 4-8 hours, place it in an oxygen-containing atmosphere and pre-calcine it at 380℃-420℃ for 1-3 hours, then raise the temperature to 480℃-520℃ and hold it for 4-8 hours.

[0013] In an optional embodiment, the mass ratio of high-entropy multi-anion lithium borate powder to high-nickel cathode material is (0.05-2.00):100; And / or, during the mixing process of high-entropy multi-anion lithium borate powder and high-nickel cathode material, the stirring speed is controlled at 800rpm-1500rpm and the stirring time is 15min-30min; And / or, the chemical formula of the high-nickel cathode material is LiNi x Co y Mn z O2, where: x+y+z=1, 0.8≤x<1, 0<y<0.2, 0<z<0.2; And / or, the average particle size of the high-nickel cathode material is 2-15 μm, and the average particle size of the high-entropy multi-anion lithium borate powder is 0.5-3 μm.

[0014] In an optional embodiment, high-entropy multi-anionic lithium borate powder is mixed with high-nickel cathode material and then placed in an oxygen-containing atmosphere for low-temperature annealing at 300℃-450℃ for 4h-8h.

[0015] Secondly, the present invention provides a modified high-nickel cathode material, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0016] Thirdly, the present invention provides a lithium-ion battery comprising the modified high-nickel cathode material of the aforementioned embodiments.

[0017] The present invention has the following beneficial effects: The present invention uses four to six transition metal ions and F - PO4 3-Multiple anions were introduced into the lithium borate lattice, successfully constructing a high-entropy multi-anion coating layer. This coating layer possesses extremely high configurational entropy and chemical disorder, effectively suppressing the crystallization tendency of the coating during long-term cycling and maintaining its amorphous state for a long time, thus providing a long-term stable lithium-ion transport channel. Doping with mixed transition metal ions introduced a large number of lithium-ion vacancies into the coating. Combined with the synergistic effect of multiple anions, the room-temperature ionic conductivity was increased by several orders of magnitude compared to conventional fast ion conductors such as Li3BO3 and Li2ZrO3, significantly reducing the interfacial charge transfer impedance between the cathode and the sulfide electrolyte.

[0018] Meanwhile, the amorphous coating layer possesses excellent mechanical flexibility, enabling it to form a uniform and tight "soft contact" with the surface of the high-nickel single-crystal cathode, avoiding the hard contact defects of the crystalline coating and effectively buffering the volume changes of the cathode material during charge and discharge. Furthermore, the coating layer physically isolates residual alkaline substances such as LiOH and Li₂CO₃ on the cathode surface from direct contact with the sulfide electrolyte, suppressing the formation of high-resistivity byproducts (such as Li₂S and B₂S₃), thereby significantly enhancing interface stability. In summary, the high-nickel ternary single-crystal cathode material coated with this high-entropy multi-anion lithium borate can achieve a significant improvement in long-cycle stability and high-rate performance in sulfide solid-state batteries. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The XRD pattern of the modified lithium borate prepared in Example 1; Figure 2 The graph shows the capacity retention test results for Example 1 and Comparative Examples 1-4. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] This invention provides a method for preparing a modified high-nickel cathode material. First, high-entropy multi-anion lithium borate powder (including amorphous form) is prepared using a sol-gel method. Then, the high-entropy multi-anion lithium borate powder is used to coat the high-nickel cathode material. The steps are as follows: S1. Preparation of sol A sol is formed by mixing lithium alkoxide, borate ester, transition metal alkoxide, solvent, and complexing agent. The metal element in the transition metal alkoxide is selected from four to six elements chosen from Ti, Nb, Zr, Ta, Mo, W, V, and Y. The transition metal elements contained in the transition metal alkoxide can be any four, five, or six of the above elements, resulting in a system configuration entropy ≥ 1.5. Preferably, the transition metal elements in the transition metal alkoxide include Ti, Nb, Zr, Ta, and Mo. Using these five elements for coating further increases the system configuration entropy (≥ 1.5RR is the ideal gas constant), suppresses the crystallization tendency of the coating during long-term cycling, and maintains its amorphous state, thereby obtaining stable ion transport channels.

[0023] In some embodiments, by adjusting the amount of raw materials, the molar ratio of Li to each transition metal element is 1.5:(0.10-0.25), such as 1.5:0.10, 1.5:0.13, 1.5:0.15, 1.5:0.16, 1.5:0.18, 1.5:0.20, 1.5:0.23, 1.5:0.25, etc. The amount of each transition metal element can be the same or different, but it is preferable to control it within the above range. The molar ratio of Li to the total amount of transition metals is 1.5:(0.8-1.2), such as 1.5:0.8, 1.5:0.9, 1.5:1.0, 1.5:1.1, 1.5:1.2, etc.

[0024] In some embodiments, the transition metal alkoxide includes four to six of the following: titanium alkoxide, niobium alkoxide, zirconium alkoxide, tantalum alkoxide, molybdenum alkoxide, tungsten alkoxide, vanadium alkoxide, and yttrium alkoxide. Specifically, the titanium alkoxide is selected from at least one of tetraethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and may be any one or more of these; the niobium alkoxide is selected from at least one of niobium ethoxide, niobium propoxide, and niobium butoxide, and may be any one or more of these; the zirconium alkoxide is selected from at least one of zirconium propoxide, zirconium isopropoxide, and zirconium butoxide, and may be any one or more of these; the tantalum alkoxide is selected from at least one of tantalum ethoxide, tantalum propoxide, tantalum butoxide, and tantalum isopropoxide, and may be any one or more of these; the molybdenum alkoxide is selected from at least one of molybdenum ethoxide, and may be any one or more of these; the tungsten alkoxide is selected from at least one of tungsten ethoxide and tungsten isopropoxide, and may be any one or more of these; and the vanadium alkoxide is selected from at least one of vanadium ethoxide and vanadium triisopropoxide, and may be any one or more of these. The yttrium alkoxide is selected from at least one of yttrium butoxide and yttrium isopropoxide, and the yttrium alkoxide can be any one or more of the above.

[0025] In some embodiments, the lithium ethanol is selected from at least one of lithium methoxide, lithium ethanol, lithium isopropoxide, lithium n-butoxide, and lithium tert-butoxide, and the lithium ethanol can be any one or more of the above. The borate ester is selected from at least one of trimethyl borate, triethyl borate, triisopropyl borate, and tri-n-butyl borate, and the borate ester can be any one or more of the above.

[0026] In some embodiments, the solvent is selected from at least one of methanol, tetrahydrofuran, ethanol, isopropanol, and ethylene glycol monomethyl ether, and the solvent can be any one or more of the above. The complexing agent is selected from at least one of citric acid, ethylene glycol, oxalic acid, tartaric acid, and acrylic acid, and the complexing agent can be any one or more of the above; the molar ratio of the complexing agent to the metal ion is 0.5:1-4:1, such as 0.5:1, 1.0:1, 1.5:1, 2.0:1, 2.5:1, 3.0:1, 3.5:1, 4.0:1, etc.

[0027] In some embodiments, during the preparation of the sol, the stirring temperature is controlled at 50℃-70℃, such as 50℃, 55℃, 60℃, 65℃, 70℃, etc.; the stirring time is 1h-3h, such as 1.0h, 1.3h, 1.5h, 1.8h, 2.0h, 2.3h, 2.5h, 2.8h, 3.0h, etc.

[0028] S2, dry gel The sol was mixed with fluoride and phosphate ester, and stirred continuously to ensure uniform dispersion. After aging and drying, a dry gel was obtained. This process involved introducing F... - and PO4 3- Two types of multi-anion compounds further enhance the chemical disorder and configurational entropy of the coating, thus preparing high-entropy multi-anion lithium borate containing amorphous state.

[0029] In some embodiments, by adjusting the amount of raw materials used in steps S1 and S2, the molar ratio of Li, B, F, and P is controlled to be 1.5:(0.9-1.1):(0.2-0.4):(0.1-0.3), such as 1.5:0.90:0.20:0.10, 1.5:0.95:0.25:0.15, 1.5:1.00:0.30:0.20, 1.5:1.05:0.35:0.25, 1.5:1.10:0.40:0.30, etc. The crystallinity of lithium borate powder is 40-70%, such as 40%, 50%, 60%, 70%, etc.

[0030] In some embodiments, the fluoride is selected from at least one of lithium fluoride, ammonium fluoride, and trifluoroacetic acid, and the fluoride may be any one or more of the above. The phosphate ester is selected from at least one of trimethyl phosphate, triethyl phosphate, tributyl phosphate, and trioctyl phosphate, and the phosphate ester may be any one or more of the above.

[0031] In some embodiments, during the preparation of the dry gel, the aging time is controlled to be 6h-24h, such as 6h, 10h, 15h, 20h, 24h, etc. The aging temperature can be room temperature, such as 20℃-30℃. After aging is completed, drying is performed at a temperature of 120℃-180℃, such as 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, etc.; the drying time is 2h-6h, such as 2h, 3h, 4h, 5h, 6h, etc.

[0032] S3. Preparation of high-entropy multi-anion lithium borate powder The dry gel was ground and then sintered to obtain high-entropy multi-anionic lithium borate powder containing amorphous state.

[0033] In practice, the dry gel can be ground for 4-8 hours and then placed in an oxygen-containing atmosphere. It is first pre-calcined at 380℃-420℃ for 1-3 hours, and then heated to 480℃-520℃ and held for 4-8 hours. The organic matter is removed by pre-calcination at low temperature, and then sintered at higher temperatures to obtain high-entropy multi-anionic lithium borate powder containing amorphous state.

[0034] Specifically, the grinding method is not limited, and the grinding time can be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc. The oxygen-containing atmosphere can be oxygen, but is not limited to it. The pre-firing temperature can be 380℃, 390℃, 400℃, 410℃, 420℃, etc., and the pre-firing time can be 1 hour, 2 hours, 3 hours, etc. After pre-firing, the temperature is raised and held at that temperature, which can be 480℃, 490℃, 500℃, 510℃, 520℃, etc.; the holding time can be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc.

[0035] S4, Covering High-entropy multi-anion lithium borate powder is mixed with high-nickel cathode material at high speed to ensure that the coating agent is uniformly attached to the surface of the cathode particles. Then, the mixed powder is subjected to low-temperature annealing and furnace cooling to obtain the coated cathode material.

[0036] In some embodiments, the mass ratio of high-entropy multi-anionic lithium borate powder to high-nickel cathode material is (0.05-2.00):100, such as 0.05:100, 0.10:100, 0.30:100, 0.50:100, 0.80:100, 1.00:100, 1.30:100, 1.50:100, 1.80:100, 2.00:100, etc. That is, the powder obtained in step S3 is fed to the high-nickel cathode material at a mass ratio of 0.05-2 wt%. To achieve uniform coating, the average particle size of the high-nickel cathode material is 2-15 μm, and the average particle size of the high-entropy multi-anionic lithium borate powder is 0.5-3 μm.

[0037] Furthermore, during the mixing process of high-entropy multi-anionic lithium borate powder and high-nickel cathode material, the stirring speed is controlled at 800 rpm-1500 rpm, such as 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, etc.; the high-speed mixing time is 15 min-30 min, such as 15 min, 18 min, 20 min, 23 min, 25 min, 28 min, 30 min, etc. After mixing the high-entropy multi-anionic lithium borate powder and high-nickel cathode material, it is placed in an oxygen-containing atmosphere (such as oxygen) and annealed at a low temperature of 300℃-450℃ for 4 h-8 h. Specifically, the low-temperature annealing temperature can be 300℃, 330℃, 350℃, 380℃, 400℃, 430℃, 450℃, etc.; the low-temperature annealing time can be 4 h, 5 h, 6 h, 7 h, 8 h, etc.

[0038] This invention provides a modified high-nickel cathode material, prepared by the method described in this invention. The modified high-nickel cathode material prepared by the method described in this invention possesses both ultra-high ionic conductivity and mechanical flexibility, which can buffer the volume changes of ternary cathode materials during charge and discharge, significantly enhancing the long-cycle stability of the battery.

[0039] This invention also provides a lithium-ion battery comprising the aforementioned modified high-nickel cathode material. A cathode sheet is prepared using this modified high-nickel cathode material as the cathode active material, and then the battery is assembled with the cathode sheet, a negative electrode sheet, a separator, and an electrolyte. Through optimization of the cathode active material, a significant improvement in long-cycle stability and high-rate performance can be achieved.

[0040] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0041] Example 1 This embodiment provides a method for preparing a modified high-nickel cathode material, the steps of which are as follows: (1) According to the molar ratio of Li:B:Ti:Nb:Zr:Ta:Mo:F:P of 1.5:1.0:0.16:0.16:0.16:0.16:0.16:0.3:0.2, weigh lithium methoxide, n-butyl borate, and five transition metal alkoxides (tetraethyl titanate, niobium ethoxide, zirconium propoxide, tantalum ethoxide, and molybdenum ethoxide), use ethanol as solvent and citric acid as complexing agent, and stir at 60°C for 2 hours to form a sol. The molar ratio of complexing agent to metal ions is 2:1.

[0042] (2) Then add lithium fluoride (LiF) and tributyl phosphate (refer to step (1) for the amount of lithium fluoride and tributyl phosphate added), and continue stirring to disperse them evenly; age at room temperature for 12 hours and dry at 150°C for 4 hours to obtain dry gel.

[0043] (3) The dry gel was ground in a planetary ball mill for 6 hours using anhydrous ethanol as the medium. After grinding, it was placed in an oxygen atmosphere and pre-calcined at 400°C for 2 hours to remove organic matter. Then, the temperature was raised to 500°C and kept for 6 hours to obtain high-entropy multi-anionic lithium borate powder (average particle size of 1 μm).

[0044] (4) Mix the powder obtained in step (3) with a high-nickel cathode material (LiNi). 0.91 Co 0.06 Mn 0.03 O2 single crystals with an average particle size of 3μm were added to a high-speed mixer at a mass ratio of 1wt% (i.e., the mass ratio of high-entropy multi-anion lithium borate powder to high-nickel cathode material was 1:100) and mixed at a high speed of 1000rpm for 20 minutes to ensure that the coating agent was uniformly attached to the surface of the cathode particles. The mixed powder was then annealed at a low temperature of 400℃ for 6 hours in an oxygen atmosphere and cooled in the furnace to obtain the coated cathode material.

[0045] Example 2 The only difference from Example 1 is that the molar ratio of Li:B:Ti:Nb:Zr:Ta:Mo:F:P is 1.5:0.9:0.10:0.10:0.10:0.10:0.10:0.2:0.1 Example 3 The only difference from Example 1 is that the molar ratio of Li:B:Ti:Nb:Zr:Ta:Mo:F:P is 1.5:1.1:0.25:0.25:0.25:0.25:0.25:0.4:0.3. Example 4 The only difference from Example 1 is that the molar ratio of Li:B:Ti:Nb:Zr:Ta:Mo:F:P is 1.5:1.0:0.10:0.10:0.10:0.10:0.10:0.3:0.2.

[0046] Example 5 The only difference from Example 1 is that the molar ratio of Li:B:Ti:Nb:Zr:Ta:Mo:F:P is 1.5:1.0:0.25:0.25:0.25:0.25:0.25:0.3:0.2.

[0047] Example 6 The only difference from Example 1 is that the molar ratio of Li:B:Ti:Nb:Zr:Ta:Mo:F:P is 1.5:1.0:0.05:0.05:0.05:0.05:0.05:0.3:0.2.

[0048] Example 7 The only difference from Example 1 is that the molar ratio of Li:B:Ti:Nb:Zr:Ta:Mo:F:P is 1.5:1.0:0.40:0.40:0.40:0.40:0.40:0.3:0.2.

[0049] Example 8 The only difference from Example 1 is that the molar ratio of Li:B:Ti:Nb:Zr:Ta:Mo:F:P is 1.5:1.0:0.16:0.16:0.16:0.16:0.16:0.16:0.05.

[0050] Example 9 The only difference from Example 1 is that the molar ratio of Li:B:Ti:Nb:Zr:Ta:Mo:F:P is 1.5:1.0:0.16:0.16:0.16:0.16:0.16:0.5:0.4.

[0051] Example 10 The only difference from Example 1 is that the molar ratio of Li:B:Ti:Nb:W:V:Y:F:P is 1.5:1.0:0.16:0.16:0.16:0.16:0.16:0.3:0.2, and the five transition metal alkoxides are tetraethyl titanate, niobium ethoxide, tungsten ethoxide, vanadium ethoxide, and yttrium butoxide.

[0052] Example 11 The only difference from Example 1 is that the molar ratio of Li:B:Ti:Nb:Zr:V:Y:F:P is 1.5:1.0:0.16:0.16:0.16:0.16:0.16:0.3:0.2, and the five transition metal alkoxides are tetraethyl titanate, niobium ethoxide, zirconium n-propoxide, vanadium ethoxide, and yttrium butoxide.

[0053] Example 12 The only difference from Example 1 is that the low-temperature annealing temperature in step (4) is 300°C.

[0054] Example 13 The only difference from Example 1 is that the low-temperature annealing temperature in step (4) is 450°C.

[0055] Example 14 The only difference from Example 1 is that the low-temperature annealing temperature in step (4) is 200°C.

[0056] Example 15 The only difference from Example 1 is that the low-temperature annealing temperature in step (4) is 600°C.

[0057] Comparative Example 1 The only difference from Example 1 is that lithium fluoride (LiF) and tributyl phosphate are not added in step (2).

[0058] Comparative Example 2 The only difference from Example 1 is that lithium fluoride (LiF) is not added in step (2).

[0059] Comparative Example 3 The only difference from Example 1 is that tributyl phosphate is not added in step (2).

[0060] Comparative Example 4 The only difference from Example 1 is that the five transition metal alkoxides are not added in step (1).

[0061] Experimental Example 1 XRD analysis of the modified lithium borate prepared in Example 1 was conducted using an X-ray diffractometer with Cu Kα radiation (λ = 0.15406 nm), a scanning range of 10°–80° (2θ), a step size of 0.02°, and a scanning speed of 2° / min. The results are as follows. Figure 1 As shown.

[0062] from Figure 1 It can be seen that the XRD pattern of modified lithium borate shows amorphous characteristic peaks, indicating that the crystallinity of lithium borate is effectively reduced after co-doping with anions and cations.

[0063] Experimental Example 2 The performance of the modified high-nickel cathode materials prepared in the test examples and comparative examples is as follows: Figure 2 As shown in Table 1.

[0064] Test method: Crystallinity Test: The crystallinity of lithium borate was determined using the X-ray diffraction difference method (peak fitting method). Test conditions: An X-ray diffractometer with Cu Kα radiation (λ=0.15406 nm) was used, with a tube voltage of 40 kV, a tube current of 40 mA, a scanning range of 10°–80° (2θ), a step size of 0.02°, and a scanning speed of 2° / min. After background subtraction, the sharp crystalline peaks and the broad amorphous peaks were separated using peak fitting software. The integrated intensity Ic of the crystalline peak and the integrated intensity Ia of the amorphous peak were obtained by summing them. The crystallinity of lithium borate was then determined as follows:

[0065] Mold battery testing: Assemble the molded battery: Weigh lithium borate modified cathode material, Li6PS5Cl electrolyte and VGCF in a ratio of 70:27:3, grind in a mortar for 30 minutes to obtain composite cathode material powder for later use.

[0066] In an argon-atmospheric glove box, 80 mg of coarse Li6PS5Cl electrolyte powder (particle size 3.5 μm) was weighed and placed in a 10 mm diameter battery mold. It was then pressed into a sheet using a tablet press at 300 MPa for 1 min. 16 mg of the aforementioned ground composite cathode powder was weighed and placed on the surface of the freshly pressed electrolyte sheet. After being flattened, it was pressed into a sheet again using a tablet press at 300 MPa for 1 min. A 10 mm diameter Al foil was placed on the surface of the composite cathode sheet as the cathode current collector. The Li6PS5Cl electrolyte sheet was then placed with Li... 0.5 An In alloy anode and a Cu foil current collector are used. After assembly, a pressure of 100 MPa is applied to obtain a sulfide solid-state mold battery. The mold battery is then held in place by a fixture with a torque of 10 N·m and tested in a cabinet.

[0067] Rate testing: Constant current charging and discharging were performed at 0.1, 0.2, 0.33, 0.5, and 1C on the Blue Electric test cabinet to measure the 0.1C charge / discharge capacity and rate performance.

[0068] Cyclic test: After two cycles of constant current charging and discharging at 0.1C, the circuit was cyclically charged at 0.33C for 50 cycles, and the cycle retention rate was measured.

[0069] Table 1. Performance of the modified high-nickel cathode materials prepared in the examples and comparative examples.

[0070] As shown in Table 1, the appropriate amount of cations entering the crystal lattice or coating layer, generating suitable defects or a second phase, suppresses excessive crystallization and forms a semi-crystalline structure, which can effectively improve the cycle performance of solid-state batteries. Excessively crystalline lithium borate coatings are hard and brittle, lacking plasticity, and cannot adapt to the volume changes of the cathode material during charging and discharging, easily generating microcracks that lead to increased interfacial impedance. Conversely, excessively low crystallinity results in high chemical activity, easily causing side reactions with the solid electrolyte to generate inert products, leading to interfacial passivation.

[0071] Comparing Examples 1 and 12-15, it can be seen that the annealing temperature has a significant impact on the final performance of the solid-state battery. At too low a temperature (200°C), the lithium borate coating layer adheres poorly to the substrate cathode material, while at too high a temperature (600°C), the crystallinity of the final lithium borate coating layer increases further, affecting the coating effect and leading to a deterioration in cycle performance. Co-doping of anions and cations has a significant synergistic effect. When anions and cations are co-doped, the crystallinity of lithium borate can be effectively reduced. At the same time, due to the charge compensation effect of the two, the structure of the modified lithium borate coating can be stabilized, thereby significantly improving the cycle stability of solid-state batteries.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a modified high-nickel cathode material, characterized in that, include: A sol is formed by mixing lithium alkoxide, borate ester, transition metal alkoxide, solvent and complexing agent; wherein the metal element in the transition metal alkoxide is selected from four to six of Ti, Nb, Zr, Ta, Mo, W, V and Y; The sol was mixed with fluoride and phosphate ester, aged, and dried to obtain a dry gel; The dry gel was ground and then sintered to obtain high-entropy multi-anionic lithium borate powder. The high-entropy multi-anion lithium borate powder is mixed with a high-nickel cathode material and then annealed.

2. The preparation method according to claim 1, characterized in that, In the process of preparing the high-entropy multi-anionic lithium borate powder, the molar ratio of Li, B, F and P is controlled to be 1.5:(0.9-1.1):(0.2-0.4):(0.1-0.3), and the crystallinity of the lithium borate powder is 40-70%. And / or, the molar ratio of Li to each transition metal element is 1.5:(0.10-0.25). And / or, the molar ratio of Li to the total amount of transition metals is 1.5:(0.8-1.2).

3. The preparation method according to claim 1 or 2, characterized in that, The transition metal alkoxide is selected from four to six of the following: titanium alkoxide, niobium alkoxide, zirconium alkoxide, tantalum alkoxide, molybdenum alkoxide, tungsten alkoxide, vanadium alkoxide, and yttrium alkoxide. The titanium alkoxide is selected from at least one of tetraethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate; The niobium alkoxide is selected from at least one of niobium ethanol, niobium propoxide, and niobium butoxide. The zirconium alkoxide is selected from at least one of zirconium n-propoxide, zirconium isopropoxide, and zirconium n-butoxide; The tantalum alkoxide is selected from at least one of tantalum ethoxide, tantalum propoxide, tantalum butoxide, and tantalum isopropoxide; The molybdenum alkoxide is molybdenum ethanol; The tungsten alkoxide is selected from at least one of tungsten ethoxide and tungsten isopropoxide; The vanadium alkoxide is selected from at least one of vanadium ethanol and vanadium triisopropoxide; The yttrium alkoxide is selected from at least one of yttrium butoxide and yttrium isopropoxide.

4. The preparation method according to claim 1 or 2, characterized in that, The lithium ethanol is selected from at least one of lithium methoxide, lithium ethanol, lithium isopropoxide, lithium n-butoxide, and lithium tert-butoxide. And / or, the borate ester is selected from at least one of trimethyl borate, triethyl borate, triisopropyl borate and tri-n-butyl borate; And / or, the fluoride is selected from at least one of lithium fluoride, ammonium fluoride and trifluoroacetic acid; And / or, the phosphate ester is selected from at least one of trimethyl phosphate, triethyl phosphate, tributyl phosphate and trioctyl phosphate.

5. The preparation method according to claim 1, characterized in that, The solvent is selected from at least one of methanol, tetrahydrofuran, ethanol, isopropanol, and ethylene glycol monomethyl ether; And / or, the complexing agent is selected from at least one of citric acid, ethylene glycol, oxalic acid, tartaric acid and acrylic acid; the molar ratio of the complexing agent to the metal ion is 0.5:1-4:

1.

6. The preparation method according to claim 1, characterized in that, During the preparation of the sol, the stirring temperature is controlled at 50℃-70℃ and the stirring time is 1h-3h; And / or, during the preparation of the dry gel, the aging time is controlled to be 6h-24h, the drying temperature is 120℃-180℃, and the drying time is 2h-6h; And / or, after grinding the dry gel for 4-8 hours, place it in an oxygen-containing atmosphere and pre-calcine it at 380℃-420℃ for 1-3 hours, then raise the temperature to 480℃-520℃ and hold it for 4-8 hours.

7. The preparation method according to claim 1, characterized in that, The mass ratio of the high-entropy multi-anionic lithium borate powder to the high-nickel cathode material is (0.05-2.00):100; And / or, during the mixing process of the high-entropy multi-anion lithium borate powder and the high-nickel cathode material, the stirring speed is controlled at 800rpm-1500rpm and the stirring time is 15min-30min; And / or, the chemical formula of the high-nickel cathode material is LiNi x Co y Mn z O2, where: x+y+z=1, 0.8≤x<1, 0<y<0.2, 0<z<0.2; And / or, the average particle size of the high-nickel cathode material is 2-15 μm, and the average particle size of the high-entropy multi-anion lithium borate powder is 0.5-3 μm.

8. The preparation method according to claim 7, characterized in that, The high-entropy multi-anionic lithium borate powder was mixed with the high-nickel cathode material and then placed in an oxygen-containing atmosphere for low-temperature annealing at 300℃-450℃ for 4h-8h.

9. A modified high-nickel cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. A lithium-ion battery, characterized in that, Including the modified high-nickel cathode material as described in claim 9.

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