Hydrophobic modified lithium aluminum titanium phosphate solid electrolyte, preparation method thereof and lithium ion battery

Abstract

The invention provides a hydrophobic modified titanium aluminum lithium phosphate solid electrolyte, a preparation method thereof and a lithium ion battery. The hydrophobic modified titanium aluminum lithium phosphate solid electrolyte comprises titanium aluminum lithium phosphate and a hydrophobic modified material coated outside the titanium aluminum lithium phosphate, the hydrophobic modified material comprises a siloxane coupling agent. In the hydrophobic modified lithium titanium aluminum phosphate solid electrolyte, the exterior of lithium titanium aluminum phosphate is coated with a siloxane coupling agent, and hydrophobic groups in the siloxane coupling agent perform hydrophobic treatment on hydrophilic groups on the surface of lithium titanium aluminum phosphate, so that the moisture content of lithium titanium aluminum phosphate is reduced, and the risk of corrosion by water and proton hydrogen is reduced; in addition, the stability of the lithium titanium aluminum phosphate in the air is also improved, and the water absorption problem of the lithium titanium aluminum phosphate in the storage and processing processes is relieved.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries and relates to a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, in particular to a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte and a preparation method thereof and a lithium ion battery. Background Art

[0002] Secondary lithium-ion batteries have been used in various fields due to their advantages such as high specific capacity, high voltage, wide temperature range, high coulombic efficiency, high cycle performance, low cost and no memory effect. However, most commercial lithium-ion batteries currently use liquid organic electrolyte solutions, which have low boiling points and are toxic, and are prone to leakage. Improper operation may even cause dangerous events such as battery explosion. Relatively speaking, all-solid-state batteries using solid electrolytes are considered safer, have longer cycle life, and higher energy density, and are a promising battery system.

[0003] Currently common solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes and composite solid electrolytes. Among them, lithium aluminum titanium phosphate solid electrolyte (LATP) has a high ionic conductivity, so it has attracted the attention of many researchers. Lithium aluminum titanium phosphate solid electrolyte can be used to coat, blend and coat positive and negative electrode active materials; it can also be used to coat diaphragms and primer current collectors, both of which can improve the cycle capacity and cycle life of the battery. However, lithium aluminum titanium phosphate solid electrolytes easily absorb moisture in the air, reduce ionic conductivity, and are easily corroded by water and proton hydrogen in quasi-solid-state battery electrolytes, resulting in unstable interfaces and affecting the electrochemical performance of the battery.

[0004] CN117832496A discloses a hydrophobically modified lithium aluminum titanium phosphate powder material and a preparation method and application. The present invention reduces the moisture content of the LATP material and solves the water absorption problem of the LATP material through a hydrophobic modification method. Moisture content is an important indicator in the production process of lithium ion batteries. When the moisture content of the lithium ion battery raw material exceeds the standard or excessive moisture is introduced during the production process, a large amount of HF will be generated in the battery. HF has strong corrosiveness and will seriously reduce the durability and service life of the battery. By hydrophobic modification of the LATP material, on the one hand, the moisture content in the LATP material can be reduced, and on the other hand, the water absorption problem of the LATP material during storage and processing can be alleviated, thereby greatly reducing the dew point requirements for warehouses and workshops, reducing storage and production costs, and improving the durability and life of lithium ion batteries. However, the hydrophobic performance of the hydrophobically modified lithium aluminum titanium phosphate powder material is insufficient, the water blocking effect is limited, and it is difficult to meet the needs of actual applications.

[0005] CN119133773A discloses a method for preparing hydrophobically modified lithium aluminum titanium phosphate powder for diaphragm coating, wherein a sand milling solvent, a polymer dispersant, and a coarse LATP powder are added to a high-speed dispersion tank in proportion for stirring; the mixed solution is subjected to nano-sand milling treatment by a sand mill, and a nano-dispersed liquid having a uniform particle size distribution is prepared by sand milling; the grinding speed of the sand mill is reduced, silicone resin is added for low-speed sand milling treatment, and silicone resin is surface-coated on LATP to obtain a hydrophobically modified LATP dispersion liquid; the hydrophobically modified LATP dispersion liquid is spray-dried, and a hydrophobically modified LATP powder is obtained after drying. The preparation method is suitable for preparing LATP nano-powder for diaphragm coating, and on the one hand, the surface coating of LATP nano-powder with silicone resin can significantly reduce the water content and water absorption rate of the powder. However, the hydrophobic property of the hydrophobically modified lithium aluminum titanium phosphate powder for diaphragm coating still cannot meet the needs in practical applications.

[0006] The lithium aluminum titanium phosphate solid electrolyte disclosed in the prior art has certain defects. The lithium aluminum titanium phosphate solid electrolyte easily absorbs moisture in the air, reduces ionic conductivity, and is easily corroded by water and proton hydrogen, thereby affecting the electrochemical performance of lithium ion batteries. In addition, the hydrophobic performance of the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte provided in the prior art still cannot meet the needs of practical applications. Therefore, it is very important to develop and design a new type of hydrophobically modified lithium aluminum titanium phosphate solid electrolyte and its preparation method and lithium ion battery. Summary of the invention

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte, a preparation method thereof, and a lithium ion battery. In the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte, the outside of the lithium aluminum titanium phosphate is coated with a siloxane coupling agent, and the hydrophobic groups in the siloxane coupling agent hydrophobically treat the hydrophilic groups on the surface of the lithium aluminum titanium phosphate, which not only reduces the moisture content of the lithium aluminum titanium phosphate and reduces the risk of corrosion by water and proton hydrogen; in addition, the stability of the lithium aluminum titanium phosphate in the air is improved, and the water absorption problem of the lithium aluminum titanium phosphate during storage and processing is alleviated.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte, wherein the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte comprises lithium aluminum titanium phosphate, and a hydrophobic modified material coated on the outside of the lithium aluminum titanium phosphate; the hydrophobic modified material is a siloxane coupling agent.

[0010] In the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte provided by the present invention, the outside of the lithium titanium aluminum phosphate is coated with a siloxane coupling agent, and the hydrophobic groups in the siloxane coupling agent perform hydrophobic treatment on the hydrophilic groups on the surface of the lithium titanium aluminum phosphate, which not only reduces the moisture content of the lithium titanium aluminum phosphate, but also reduces the risk of corrosion by water and proton hydrogen, thereby improving the ionic conductivity and interface stability, thereby improving the electrochemical performance of the lithium ion battery; in addition, the stability of the lithium titanium aluminum phosphate in the air is improved, and the water absorption problem of the lithium titanium aluminum phosphate during storage and processing is alleviated, thereby greatly reducing the dew point requirements for warehouses and workshops, and reducing storage and production costs.

[0011] In a second aspect, the present invention provides a method for preparing the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte according to the first aspect, the preparation method comprising:

[0012] The lithium aluminum titanium phosphate powder, the siloxane coupling agent, the solvent and the acidic pH regulator are mixed and then heat treated to obtain the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

[0013] The hydrophobically modified lithium aluminum titanium phosphate solid electrolyte provided in the present invention is obtained by coating lithium aluminum titanium phosphate with a siloxane coupling agent under acidic conditions; each group (Si-OCH3) of the silane coupling agent is hydrolyzed under acidic conditions to form three silanols (Si-OH), and then one of the Si-OHs is hydrogen-bonded with the hydroxyl group on the surface of the lithium aluminum titanium phosphate, and further undergoes a dehydration condensation reaction by heating to form a -Si-OX covalent bond (X represents the surface of the lithium aluminum titanium phosphate particle); at the same time, the other two Si-OHs undergo a condensation reaction with the Si-OH of the adjacent silane coupling agent to form a network structure, and the film formed by the network structure covers the surface of the lithium aluminum titanium phosphate, thereby making the surface of the lithium aluminum titanium phosphate organic, thereby achieving the purpose of hydrophobic modification.

[0014] Preferably, the D50 particle size of the lithium aluminum titanium phosphate powder is 0.5 to 2 μm, for example, 0.5 μm, 0.7 μm, 1 μm, 1.2 μm, 1.5 μm, 1.7 μm or 2 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] Preferably, the lithium aluminum titanium phosphate powder is dried before the mixing.

[0016] Preferably, the drying temperature is 300-400° C. and the drying time is 2-4 hours.

[0017] The drying temperature in the present invention is 300-400°C, for example, it can be 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C or 400°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] The drying time described in the present invention is 2 to 4 hours, for example, it can be 2 hours, 2.2 hours, 2.5 hours, 2.8 hours, 3 hours, 3.2 hours, 3.5 hours, 3.8 hours or 4 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, the mass ratio of lithium aluminum titanium phosphate powder to siloxane coupling agent in the mixture is 200:(0.1-5), for example, it can be 200:0.1, 200:0.5, 200:1, 200:1.5, 200:2, 200:2.5, 200:3, 200:3.5, 200:4, 200:4.5 or 200:5, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] The mass ratio of lithium aluminum titanium phosphate powder to siloxane coupling agent in the present invention affects the performance of the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte; when the amount of siloxane coupling agent is too low, the hydrophobic effect of the obtained hydrophobically modified lithium aluminum titanium phosphate solid electrolyte is relatively poor; when the amount of siloxane coupling agent is too high, although a good hydrophobic effect can be achieved, excessive siloxane coupling agent will cause polymer aggregation, increase the pores inside the material, and cause the conductivity of the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte to decrease.

[0021] Preferably, the mass ratio of the siloxane coupling agent to the solvent in the mixture is (0.1-5):100, for example, it can be 0.1:100, 0.5:100, 1:100, 2:100, 3:100, 4:100 or 5:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the mixing comprises: first mixing a siloxane coupling agent, a solvent and an acidic pH regulator to obtain an acidic siloxane coupling agent solution, and secondly mixing the obtained acidic siloxane coupling agent solution with lithium aluminum titanium phosphate powder to obtain a remixed solution.

[0023] Preferably, the first mixing comprises: first mixing a solvent with an acidic pH regulator to obtain an acidic solvent, and then mixing the obtained acidic solvent with a siloxane coupling agent to obtain an acidic siloxane coupling agent solution.

[0024] Preferably, the pH of the acidic solvent is between 3 and 5, for example, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8 or 5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, the acidic pH adjuster comprises an acid solution, and the acid solution comprises any one of citric acid solution, glacial acetic acid solution, hydrochloric acid solution or sulfuric acid solution, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of citric acid solution and glacial acetic acid solution, a combination of hydrochloric acid solution and sulfuric acid solution, and a combination of citric acid solution, glacial acetic acid solution and hydrochloric acid solution.

[0026] Preferably, the first mixing method includes stirring.

[0027] Preferably, the second mixing method includes ultrasonic stirring.

[0028] Preferably, the heat treatment comprises water bath heating.

[0029] Preferably, the water bath heating temperature is 60-80° C., and the heating time is 4-8 hours.

[0030] The temperature of the water bath heating in the present invention is 60-80°C, for example, it can be 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] The water bath heating time in the present invention is 4 to 8 hours, for example, it can be 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the heat treatment further includes cooling, solid-liquid separation, drying, grinding and screening in sequence.

[0033] Preferably, the cooling end temperature is 15-30°C, for example, it can be 15°C, 17°C, 19°C, 20°C, 22°C, 25°C, 28°C or 30°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the solid-liquid separation comprises: after pouring out the supernatant, repeating alcohol washing and suction filtration at least once.

[0035] Preferably, the drying method includes vacuum drying.

[0036] Preferably, the vacuum drying is carried out at a temperature of 80 to 150° C. and for a time of 6 to 12 hours.

[0037] The vacuum drying temperature in the present invention is 80-150°C, for example, it can be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] The vacuum drying time in the present invention is 6 to 12 hours, for example, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, a sieve of 200 to 400 mesh is used for the screening, for example, it can be 200 mesh, 220 mesh, 250 mesh, 280 mesh, 300 mesh, 320 mesh, 350 mesh, 380 mesh or 400 mesh, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the chemical formula of lithium aluminum titanium phosphate in the lithium aluminum titanium phosphate powder is Li 1+x Al x Ti 2-x (PO4)3、Li 1.3 Al 0.3 M1 y Ti 1.7-y (PO4)3、Li 1.3+z Al 0.3-z M2 z Ti 1.7 (PO4)3, or Li 1.3 Al 0.3-j M3 j Ti 1.7 Any one or a combination of at least two of (PO4)3;

[0041] Among them, 0.1≤x≤0.5; 0≤y≤0.2, M1 is Zr and / or Hf; 0≤z≤0.2, M2 is any one of Ca, Mg or Sr or a combination of at least two; 0≤j≤0.2, M3 is any one of Y, Ga or Sc or a combination of at least two.

[0042] In the present invention, 0.1≤x≤0.5, and the value of x may be, for example, 0.1, 0.2, 0.3, 0.4 or 0.5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] In the present invention, 0≤y≤0.2, and the value of y can be, for example, 0, 0.02, 0.05, 0.07, 0.1, 0.12, 0.15, 0.18 or 0.2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In the present invention, 0≤z≤0.2, and the value of z can be, for example, 0, 0.02, 0.05, 0.07, 0.1, 0.12, 0.15, 0.18 or 0.2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] In the present invention, 0≤j≤0.2, the value of j can be, for example, 0, 0.02, 0.05, 0.07, 0.1, 0.12, 0.15, 0.18 or 0.2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In the present invention, M2 is any one of Ca, Mg or Sr or a combination of at least two of them. Typical but non-limiting combinations include a combination of Ca and Mg, a combination of Mg and Sr, or a combination of Ca, Mg and Sr.

[0047] In the present invention, M3 is any one of Y, Ga or Sc or a combination of at least two of them. Typical but non-limiting combinations include a combination of Y and Ga, a combination of Ga and Sc, and a combination of Y, Ga and Sc.

[0048] Preferably, the siloxane coupling agent includes any one of an alkyl siloxane coupling agent, a fluorinated siloxane coupling agent, an amino siloxane coupling agent, a vinyl siloxane coupling agent or a methacryloxy siloxane coupling agent, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of an alkyl siloxane coupling agent and a vinyl siloxane coupling agent, a combination of a fluorinated siloxane coupling agent and an amino siloxane coupling agent, a combination of a vinyl siloxane coupling agent and a methacryloxy siloxane coupling agent, or a combination of an alkyl siloxane coupling agent, an amino siloxane coupling agent and a fluorinated siloxane coupling agent.

[0049] Preferably, the alkyl coupling agent includes any one of octadecyltrimethoxysilane, octadecyltriethoxysilane, hexadecyltrimethoxysilane, octyltrimethoxysilane or octyltriethoxysilane, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of octadecyltrimethoxysilane and octadecyltriethoxysilane, a combination of hexadecyltrimethoxysilane and octyltrimethoxysilane, a combination of octyltrimethoxysilane and octyltriethoxysilane, or a combination of octadecyltrimethoxysilane, octadecyltriethoxysilane and hexadecyltrimethoxysilane.

[0050] Preferably, the fluorinated siloxane coupling agent includes any one of heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltriethoxysilane or trifluoropropylmethylcyclotrisiloxane, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of heptadecafluorodecyltrimethoxysilane and tridecafluorooctyltriethoxysilane, a combination of tridecafluorooctyltriethoxysilane and trifluoropropylmethylcyclotrisiloxane, or a combination of heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltriethoxysilane and trifluoropropylmethylcyclotrisiloxane.

[0051] Preferably, the aminosiloxane coupling agent includes γ-aminopropyltriethoxysilane.

[0052] Preferably, the vinyl siloxane coupling agent includes any one of vinyl triethoxysilane, vinyl trimethoxysilane or vinyl tri(β-methoxyethoxy)silane or a combination of at least two thereof, and a typical but non-limiting combination includes a combination of vinyl triethoxysilane and vinyl trimethoxysilane, a combination of vinyl trimethoxysilane and vinyl tri(β-methoxyethoxy)silane, or a combination of vinyl triethoxysilane, vinyl trimethoxysilane and vinyl tri(β-methoxyethoxy)silane.

[0053] Preferably, the methacryloxysiloxane coupling agent includes methacryloxypropyltrimethoxysilane.

[0054] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises:

[0055] (1) firstly mixing a solvent and an acidic pH adjusting agent by stirring to obtain an acidic solvent with a pH of 3 to 5, and then mixing the obtained acidic solvent with a siloxane coupling agent by stirring to obtain an acidic siloxane coupling agent solution, wherein the mass ratio of the solvent to the siloxane coupling agent is (0.1 to 5):100;

[0056] (2) drying lithium aluminum titanium phosphate powder having a D50 particle size of 0.5 to 2 μm at 300 to 400° C. for 2 to 4 hours, and then mixing the acidic siloxane coupling agent solution obtained in step (1) with the dried lithium aluminum titanium phosphate powder by ultrasonic stirring to obtain a remixed solution, wherein the mass ratio of the dried lithium aluminum titanium phosphate powder to the siloxane coupling agent in the acidic siloxane coupling agent solution is 200:(0.1 to 5);

[0057] (3) The remixed liquid obtained in step (2) is heated in a water bath at 60 to 80° C. for 4 to 8 hours, cooled to 15 to 30° C., and the supernatant is poured out, and the alcohol washing and suction filtration are repeated at least once, and then vacuum drying is performed at 80 to 150° C. for 6 to 12 hours. The dried solid is then ground and sieved using a 200 to 400 mesh sieve to obtain a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

[0058] In a third aspect, the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises a positive electrode sheet, a solid electrolyte layer and a negative electrode sheet;

[0059] The positive electrode active material layer on the positive electrode sheet includes the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte described in the first aspect, and the main component of the solid electrolyte layer is the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte described in the first aspect.

[0060] Preferably, the solid electrolyte layer is attached to the surface of the positive electrode sheet.

[0061] Preferably, the positive electrode active material layer on the positive electrode sheet includes the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, battery active materials, electronic conductive materials and binder; the solid electrolyte layer includes the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte and binder; and the negative electrode sheet includes a metallic lithium negative electrode.

[0062] In a fourth aspect, the present invention further provides a process for preparing the lithium-ion battery according to the third aspect, the process comprising:

[0063] (I) Preparation of electrode slurry: The hydrophobically modified lithium aluminum titanium phosphate solid electrolyte described in the first aspect is mixed with a battery active material, an electronic conductive material, a binder and a solvent in a mass ratio of (5-10):(70-90):(1-5):(0.5-2):(100-150) in a planetary stirrer at a speed of 400-1200 r / min for 30-60 min to form an electrode slurry;

[0064] (II) Preparation of electrolyte slurry: The hydrophobically modified lithium aluminum titanium phosphate solid electrolyte, the binder and the solvent described in the first aspect are mixed in a mass ratio of (70-90): (0.5-5): (100-150) in a planetary stirrer at a speed of 400-1200 r / min for 30-60 min to obtain an electrolyte slurry;

[0065] (III) The electrode slurry is coated on a carbon-coated aluminum foil, followed by drying and rolling to obtain a positive electrode sheet containing a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte in the solid positive electrode active material layer; the electrolyte slurry is then coated on the positive electrode sheet, followed by drying and rolling to form a solid electrolyte layer after compaction to obtain a layered structure having a solid electrolyte layer bonded to the surface of the positive electrode sheet; metallic lithium is used as the negative electrode sheet, the negative electrode sheet and the obtained layered structure are assembled to obtain a button battery, and then a liquid electrolyte accounting for 1 to 5 wt% of the total mass of the battery is poured into the positive electrode sheet to obtain a full battery.

[0066] Preferably, the battery active material comprises lithium iron phosphate and / or lithium nickel cobalt manganese oxide;

[0067] Preferably, the electronically conductive material comprises conductive carbon black and / or carbon nanotubes.

[0068] Preferably, the binder comprises polymethylpyrrolidone and / or polyvinylidene fluoride.

[0069] Preferably, the solvent comprises isopropanol and / or methanol.

[0070] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] (1) In the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte provided by the present invention, the outside of the lithium titanium aluminum phosphate is coated with a siloxane coupling agent, and the hydrophobic groups in the siloxane coupling agent hydrophobically treat the hydrophilic groups on the surface of the lithium titanium aluminum phosphate, which not only reduces the moisture content of the lithium titanium aluminum phosphate, but also reduces the risk of corrosion by water and proton hydrogen, thereby improving the ionic conductivity and interface stability, thereby improving the electrochemical performance of the battery;

[0073] (2) In the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte provided by the present invention, the hydrophobic groups in the siloxane coupling agent hydrophobically treat the hydrophilic groups on the surface of the lithium aluminum titanium phosphate, thereby improving the stability of the lithium aluminum titanium phosphate in the air and alleviating the water absorption problem of the lithium aluminum titanium phosphate during storage and processing, thereby greatly reducing the dew point requirements for warehouses and workshops and reducing storage and production costs. DETAILED DESCRIPTION

[0074] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0075] Example 1

[0076] This embodiment provides a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, wherein the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte comprises lithium titanium aluminum phosphate, and methacryloxypropyltrimethoxysilane coated on the outside of the lithium titanium aluminum phosphate;

[0077] The chemical formula of the lithium aluminum titanium phosphate is Li 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0078] The preparation method of the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte comprises:

[0079] (1) in a drying room, firstly mixing anhydrous ethanol and glacial acetic acid solution by stirring to obtain an acidic solvent with a pH of 3.5, and then mixing the obtained acidic solvent with methacryloxypropyltrimethoxysilane by stirring to obtain an acidic methacryloxypropyltrimethoxysilane solution, wherein the mass ratio of anhydrous ethanol to methacryloxypropyltrimethoxysilane is 1:100;

[0080] (2) In a drying room, the lithium aluminum titanium phosphate powder having a D50 particle size of 0.6 μm is dried at 400° C. for 4 h, and then the acidic methacryloxypropyl trimethoxysilane solution obtained in step (1) and the dried lithium aluminum titanium phosphate powder are mixed by ultrasonic stirring to obtain a remixed solution, wherein the mass ratio of the dried lithium aluminum titanium phosphate powder to the methacryloxypropyl trimethoxysilane in the acidic methacryloxypropyl trimethoxysilane solution is 200:1;

[0081] (3) In a drying room, the remixed liquid obtained in step (2) is heated in a water bath at 80° C. for 6 h, cooled to 25° C., and the supernatant is poured out, and then the alcohol washing and suction filtration are repeated three times, and then vacuum drying is performed at 120° C. for 8 h. The dried solid is then ground and sieved with a 200-mesh sieve to obtain a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

[0082] This embodiment also provides a lithium-ion battery, which includes a positive electrode sheet, a solid electrolyte layer and a negative electrode sheet, wherein the solid electrolyte layer is attached to the surface of the positive electrode sheet;

[0083] The positive electrode active material layer on the positive electrode sheet includes the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, lithium iron phosphate, carbon nanotubes and polymethyl pyrrolidone in this embodiment; the solid electrolyte layer includes the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte and polymethyl pyrrolidone in this embodiment; the negative electrode sheet is a metallic lithium negative electrode.

[0084] The preparation process of the lithium ion battery comprises:

[0085] (I) Preparation of electrode slurry: The hydrophobically modified lithium titanium aluminum phosphate solid electrolyte of this embodiment is mixed with lithium iron phosphate, carbon nanotubes, polymethyl pyrrolidone and isopropanol in a mass ratio of 5:90:5:1:120 in a planetary stirrer at a speed of 1000 r / min for 30 min to form an electrode slurry;

[0086] (II) Preparation of electrolyte slurry: The hydrophobically modified lithium aluminum titanium phosphate solid electrolyte, polymethyl pyrrolidone and isopropanol in this embodiment are mixed in a planetary stirrer at a speed of 1000 r / min for 30 min in a ratio of 85:5:120 by mass to obtain an electrolyte slurry;

[0087] (III) The electrode slurry is coated on a carbon-coated aluminum foil, followed by drying and rolling to obtain a positive electrode sheet containing a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte in the solid positive electrode active material layer; the electrolyte slurry is then coated on the positive electrode sheet, followed by drying and rolling to form a solid electrolyte layer after compaction to obtain a layered structure having a solid electrolyte layer bonded to the surface of the positive electrode sheet; metallic lithium is used as the negative electrode sheet, the negative electrode sheet and the obtained layered structure are assembled to obtain a button battery, and then a liquid electrolyte accounting for 2 wt% of the total mass of the battery is poured into the positive electrode sheet to obtain a full battery.

[0088] Example 2

[0089] This embodiment provides a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, wherein the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte comprises lithium titanium aluminum phosphate, and methacryloxypropyltrimethoxysilane coated on the outside of the lithium titanium aluminum phosphate;

[0090] The chemical formula of the lithium aluminum titanium phosphate is Li 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0091] The preparation method of the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte comprises:

[0092] (1) in a drying room, firstly mixing anhydrous ethanol and glacial acetic acid solution by stirring to obtain an acidic solvent with a pH of 3.5, and then mixing the obtained acidic solvent with methacryloxypropyltrimethoxysilane by stirring to obtain an acidic methacryloxypropyltrimethoxysilane solution, wherein the mass ratio of anhydrous ethanol to methacryloxypropyltrimethoxysilane is 0.5:100;

[0093] (2) In a drying room, the lithium aluminum titanium phosphate powder having a D50 particle size of 0.6 μm is dried at 400° C. for 4 h, and then the acidic methacryloxypropyl trimethoxysilane solution obtained in step (1) and the dried lithium aluminum titanium phosphate powder are mixed by ultrasonic stirring to obtain a remixed solution, wherein the mass ratio of the dried lithium aluminum titanium phosphate powder to the methacryloxypropyl trimethoxysilane in the acidic methacryloxypropyl trimethoxysilane solution is 200:0.5;

[0094] (3) In a drying room, the remixed liquid obtained in step (2) is heated in a water bath at 80° C. for 6 h, cooled to 25° C., and the supernatant is poured out, and then the alcohol washing and suction filtration are repeated three times, and then vacuum drying is performed at 120° C. for 8 h. The dried solid is then ground and sieved with a 200-mesh sieve to obtain a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

[0095] This embodiment also provides a lithium-ion battery, which is the same as Embodiment 1 except that the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in the lithium-ion battery is replaced with the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in this embodiment.

[0096] Example 3

[0097] This embodiment provides a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, wherein the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte comprises lithium titanium aluminum phosphate, and methacryloxypropyltrimethoxysilane coated on the outside of the lithium titanium aluminum phosphate;

[0098] The chemical formula of the lithium aluminum titanium phosphate is Li 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0099] The preparation method of the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte comprises:

[0100] (1) in a drying room, firstly mixing anhydrous ethanol and glacial acetic acid solution by stirring to obtain an acidic solvent with a pH of 3.5, and then mixing the obtained acidic solvent with methacryloxypropyltrimethoxysilane by stirring to obtain an acidic methacryloxypropyltrimethoxysilane solution, wherein the mass ratio of anhydrous ethanol to methacryloxypropyltrimethoxysilane is 5:100;

[0101] (2) In a drying room, the lithium aluminum titanium phosphate powder having a D50 particle size of 0.6 μm is dried at 400° C. for 4 h, and then the acidic methacryloxypropyl trimethoxysilane solution obtained in step (1) and the dried lithium aluminum titanium phosphate powder are mixed by ultrasonic stirring to obtain a remixed solution, wherein the mass ratio of the dried lithium aluminum titanium phosphate powder to the methacryloxypropyl trimethoxysilane in the acidic methacryloxypropyl trimethoxysilane solution is 200:5;

[0102] (3) In a drying room, the remixed liquid obtained in step (2) is heated in a water bath at 80° C. for 6 h, cooled to 25° C., and the supernatant is poured out, and then the alcohol washing and suction filtration are repeated three times, and then vacuum drying is performed at 120° C. for 8 h. The dried solid is then ground and sieved with a 200-mesh sieve to obtain a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

[0103] This embodiment also provides a lithium-ion battery, which is the same as Embodiment 1 except that the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in the lithium-ion battery is replaced with the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in this embodiment.

[0104] Example 4

[0105] This embodiment provides a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, wherein the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte comprises lithium titanium aluminum phosphate, and γ-aminopropyltriethoxysilane coated on the outside of the lithium titanium aluminum phosphate;

[0106] The chemical formula of the lithium aluminum titanium phosphate is Li 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0107] The preparation method of the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte comprises:

[0108] (1) in a drying room, firstly mixing anhydrous ethanol and glacial acetic acid solution by stirring to obtain an acidic solvent with a pH of 3.5, and then mixing the obtained acidic solvent with γ-aminopropyltriethoxysilane by stirring to obtain an acidic γ-aminopropyltriethoxysilane solution, wherein the mass ratio of anhydrous ethanol to γ-aminopropyltriethoxysilane is 1:100;

[0109] (2) In a drying room, drying lithium aluminum titanium phosphate powder having a D50 particle size of 0.6 μm at 400° C. for 4 h, and then mixing the acidic γ-aminopropyl triethoxysilane solution obtained in step (1) with the dried lithium aluminum titanium phosphate powder by ultrasonic stirring to obtain a remixed solution, wherein the mass ratio of the dried lithium aluminum titanium phosphate powder to the γ-aminopropyl triethoxysilane in the acidic γ-aminopropyl triethoxysilane solution is 200:1;

[0110] (3) In a drying room, the remixed liquid obtained in step (2) is heated in a water bath at 80° C. for 6 h, cooled to 25° C., and the supernatant is poured out, and then the alcohol washing and suction filtration are repeated three times, and then vacuum drying is performed at 120° C. for 8 h. The dried solid is then ground and sieved with a 200-mesh sieve to obtain a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

[0111] This embodiment also provides a lithium-ion battery, which is the same as Embodiment 1 except that the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in the lithium-ion battery is replaced with the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in this embodiment.

[0112] Example 5

[0113] This embodiment provides a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, wherein the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte comprises lithium titanium aluminum phosphate, and trifluoropropylmethylcyclotrisiloxane coated on the outside of the lithium titanium aluminum phosphate;

[0114] The chemical formula of the lithium aluminum titanium phosphate is Li 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0115] The preparation method of the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte comprises:

[0116] (1) in a drying room, firstly mixing anhydrous ethanol and glacial acetic acid solution by stirring to obtain an acidic solvent with a pH of 3.5, and then mixing the obtained acidic solvent with trifluoropropyl methyl cyclotrisiloxane by stirring to obtain an acidic trifluoropropyl methyl cyclotrisiloxane solution, wherein the mass ratio of anhydrous ethanol to trifluoropropyl methyl cyclotrisiloxane is 1:100;

[0117] (2) In a drying room, drying lithium aluminum titanium phosphate powder having a D50 particle size of 0.6 μm at 400° C. for 4 h, and then mixing the acidic trifluoropropyl methyl cyclotrisiloxane solution obtained in step (1) with the dried lithium aluminum titanium phosphate powder by ultrasonic stirring to obtain a remixed solution, wherein the mass ratio of the dried lithium aluminum titanium phosphate powder to the trifluoropropyl methyl cyclotrisiloxane in the acidic trifluoropropyl methyl cyclotrisiloxane solution is 200:1;

[0118] (3) In a drying room, the remixed liquid obtained in step (2) is heated in a water bath at 80° C. for 6 h, cooled to 25° C., and the supernatant is poured out, and then the alcohol washing and suction filtration are repeated three times, and then vacuum drying is performed at 120° C. for 8 h. The dried solid is then ground and sieved with a 200-mesh sieve to obtain a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

[0119] This embodiment also provides a lithium-ion battery, which is the same as Embodiment 1 except that the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in the lithium-ion battery is replaced with the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in this embodiment.

[0120] Example 6

[0121] This embodiment provides a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, wherein the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte comprises lithium titanium aluminum phosphate, and octadecyltrimethoxysilane coated on the outside of the lithium titanium aluminum phosphate;

[0122] The chemical formula of the lithium aluminum titanium phosphate is Li 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0123] The preparation method of the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte comprises:

[0124] (1) in a drying room, firstly mixing anhydrous ethanol and glacial acetic acid solution by stirring to obtain an acidic solvent with a pH of 3, and then mixing the obtained acidic solvent with octadecyltrimethoxysilane by stirring to obtain an acidic octadecyltrimethoxysilane solution, wherein the mass ratio of anhydrous ethanol to octadecyltrimethoxysilane is 0.1:100;

[0125] (2) In a drying room, drying lithium aluminum titanium phosphate powder with a D50 particle size of 0.5 μm at 300° C. for 4 h, and then mixing the acidic octadecyl trimethoxysilane solution obtained in step (1) with the dried lithium aluminum titanium phosphate powder by ultrasonic stirring to obtain a remixed solution, wherein the mass ratio of the dried lithium aluminum titanium phosphate powder to the octadecyl trimethoxysilane in the acidic octadecyl trimethoxysilane solution is 200:1;

[0126] (3) In a drying room, the remixed liquid obtained in step (2) is heated in a water bath at 60° C. for 8 h, cooled to 15° C., and the supernatant is poured out, and then the alcohol washing and suction filtration are repeated twice, and then vacuum drying is performed at 150° C. for 6 h. The dried solid is then ground and sieved with a 200-mesh sieve to obtain a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

[0127] This embodiment also provides a lithium-ion battery, which is the same as Embodiment 1 except that the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in the lithium-ion battery is replaced with the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in this embodiment.

[0128] Example 7

[0129] This embodiment provides a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, wherein the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte comprises lithium titanium aluminum phosphate, and heptadecafluorodecyltrimethoxysilane coated on the outside of the lithium titanium aluminum phosphate;

[0130] The chemical formula of the lithium aluminum titanium phosphate is Li 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0131] The preparation method of the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte comprises:

[0132] (1) in a drying room, firstly mixing anhydrous ethanol and glacial acetic acid solution by stirring to obtain an acidic solvent with a pH of 5, and then mixing the obtained acidic solvent with heptadecafluorodecyltrimethoxysilane by stirring to obtain an acidic heptadecafluorodecyltrimethoxysilane solution, wherein the mass ratio of anhydrous ethanol to heptadecafluorodecyltrimethoxysilane is 1:100;

[0133] (2) In a drying room, drying lithium aluminum titanium phosphate powder with a D50 particle size of 2 μm at 400° C. for 2 h, and then mixing the acidic heptadecafluorodecyltrimethoxysilane solution obtained in step (1) with the dried lithium aluminum titanium phosphate powder by ultrasonic stirring to obtain a remixed solution, wherein the mass ratio of the dried lithium aluminum titanium phosphate powder to the heptadecafluorodecyltrimethoxysilane in the acidic heptadecafluorodecyltrimethoxysilane solution is 200:1;

[0134] (3) In a drying room, the remixed liquid obtained in step (2) is heated in a water bath at 80° C. for 4 h, cooled to 30° C., and the supernatant is poured out, and then the alcohol washing and suction filtration are repeated 5 times, and then vacuum drying is performed at 80° C. for 12 h. The dried solid is then ground and sieved with a 400-mesh sieve to obtain a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

[0135] This embodiment also provides a lithium-ion battery, which is the same as Embodiment 1 except that the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in the lithium-ion battery is replaced with the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in this embodiment.

[0136] Example 8

[0137] This embodiment provides a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, which is the same as Example 1 except that the water bath heating temperature is 40° C. in step (3) of the preparation method of the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte.

[0138] Example 9

[0139] This embodiment provides a hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, which is the same as that of Embodiment 1 except that in step (3) of the method for preparing the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, the water bath heating temperature is 150°C.

[0140] Comparative Example 1

[0141] This comparative example provides a lithium aluminum titanium phosphate solid electrolyte, wherein the lithium aluminum titanium phosphate solid electrolyte has a chemical formula of Li 1.3 Al 0.3 Ti 1.7 Lithium aluminum titanium phosphate (PO4)3;

[0142] The preparation method of the lithium aluminum titanium phosphate solid electrolyte is:

[0143] In a drying room, lithium aluminum titanium phosphate powder with a D50 particle size of 0.6 μm was dried at 400° C. for 4 h to obtain a lithium aluminum titanium phosphate solid electrolyte.

[0144] This comparative example also provides a lithium-ion battery, which is the same as Example 1 except that the hydrophobic modified lithium aluminum titanium phosphate solid electrolyte in the lithium-ion battery is replaced with the lithium aluminum titanium phosphate solid electrolyte in this comparative example.

[0145] Comparative Example 2

[0146] This comparative example provides a lithium-ion battery, except that the solid electrolyte layer attached to the surface of the positive electrode sheet is replaced with a polyethylene separator;

[0147] That is, the entire step (II) of the preparation process of the lithium-ion battery is omitted, and the step (III) "coating the electrolyte slurry on the positive electrode sheet and then drying and rolling it in sequence, compacting it to form a solid electrolyte layer, thereby obtaining a layered structure with a solid electrolyte layer bonded to the surface of the positive electrode sheet; using metallic lithium as the negative electrode sheet, assembling the negative electrode sheet with the obtained layered structure to obtain a button battery" is replaced by "using metallic lithium as the negative electrode sheet, assembling the negative electrode sheet with the obtained positive electrode sheet and a polyethylene separator to obtain a button battery", and the rest is the same as Example 1.

[0148] The hydrophobically modified lithium aluminum titanium phosphate solid electrolyte provided in Examples 1 to 9 and the lithium aluminum titanium phosphate solid electrolyte provided in Comparative Example 1 were placed in a constant temperature and humidity chamber at a temperature of 25°C and a humidity of 20% for 7 days. Moisture content was tested using a 831 coulomb moisture meter and an 860 heating furnace. The heating furnace temperature was set to 180°C and the gas flow rate was 60 mL / min. The moisture content obtained by the test is shown in Table 1.

[0149] The hydrophobic modified lithium aluminum titanium phosphate solid electrolytes provided in Examples 1 to 9 and the lithium aluminum titanium phosphate solid electrolyte provided in Comparative Example 1 were tested by an electrochemical workstation. The diameter of the tableting mold was 17 mm, the pressure was 200 MPa, and the holding time was 10 min. The ionic conductivity was calculated according to the formula conductivity = electrolyte sheet thickness L / electrolyte sheet area S×electrolyte impedance R. The ionic conductivity obtained by the test is shown in Table 1.

[0150] The lithium ion batteries provided in the above-mentioned Examples 1 to 7 and the comparative example were left to stand for 12 hours, and then subjected to electrochemical testing, and cycled once at a rate of 0.1C, and then subjected to a cycle performance test at 1C. The test results show that the first-cycle discharge specific capacity at 0.1C is shown in Table 1, the first-cycle coulomb efficiency is shown in Table 1, and the capacity retention rate after 100 cycles is shown in Table 1.

[0151] Table 1

[0152]

[0153] From Table 1, we can get:

[0154] (1) The hydrophobically modified lithium aluminum titanium phosphate solid electrolytes provided in Examples 1 to 7 all have lower moisture content, higher electrical conductivity, higher 0.1C first cycle discharge specific capacity, higher first cycle coulombic efficiency and higher cycle retention rate;

[0155] (2) By comparing Example 1 with Examples 8 and 9, it can be seen that when the water bath heating temperature is 60-80°C, the hydrophobic modification effect on the lithium aluminum titanium phosphate solid electrolyte is better; this is because when the temperature is low, the chemical energy required for bond breaking during the grafting reaction is insufficient; and when the temperature is too high, the probability of collision between silane coupling agent molecules is relatively large, resulting in a large proportion of the self-polymerization reaction of the silane coupling agent, and the hydrophobic modification effect will be relatively reduced;

[0156] (3) By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that in the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte provided by the present invention, the outside of the lithium titanium aluminum phosphate is coated with a siloxane coupling agent, and the hydrophobic groups in the siloxane coupling agent hydrophobically treat the hydrophilic groups on the surface of the lithium titanium aluminum phosphate, which not only reduces the moisture content of the lithium titanium aluminum phosphate, but also reduces the risk of corrosion by water and proton hydrogen, thereby improving the ionic conductivity and interface stability, thereby improving the electrochemical performance of the battery; in addition, it also improves the stability of the lithium titanium aluminum phosphate in the air, alleviates the water absorption problem of the lithium titanium aluminum phosphate during storage and processing, thereby greatly reducing the dew point requirements for warehouses and workshops, and reducing storage and production costs.

[0157] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A hydrophobically modified lithium aluminum titanium phosphate solid electrolyte, characterized in that: The hydrophobically modified lithium titanium aluminum phosphate solid electrolyte comprises lithium titanium aluminum phosphate and a hydrophobic modified material coated on the outside of the lithium titanium aluminum phosphate; the hydrophobic modified material is a siloxane coupling agent.

2. A method for preparing the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte according to claim 1, characterized in that: The preparation method comprises: The lithium aluminum titanium phosphate powder, the siloxane coupling agent, the solvent and the acidic pH regulator are mixed, and then heat treated to obtain the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

3. The preparation method according to claim 2, characterized in that: The D50 particle size of the lithium aluminum titanium phosphate powder is 0.5 to 2 μm; Preferably, the mass ratio of lithium aluminum titanium phosphate powder to siloxane coupling agent in the mixture is 200:(0.1-5); Preferably, the mass ratio of the siloxane coupling agent to the solvent in the mixture is (0.1-5):

100.

4. The preparation method according to claim 2 or 3, characterized in that: The mixing comprises: first mixing a siloxane coupling agent, a solvent and an acidic pH adjusting agent to obtain an acidic siloxane coupling agent solution, and secondly mixing the obtained acidic siloxane coupling agent solution with lithium aluminum titanium phosphate powder to obtain a remixed solution; Preferably, the first mixing comprises: first mixing a solvent with an acidic pH regulator to obtain an acidic solvent, and then mixing the obtained acidic solvent with a siloxane coupling agent to obtain an acidic siloxane coupling agent solution; Preferably, the pH of the acidic solvent is 3-5.

5. The preparation method according to any one of claims 2 to 4, characterized in that: The heat treatment method includes water bath heating; Preferably, the water bath heating temperature is 60-80°C and the time is 4-8h; Preferably, the heat treatment further includes cooling, solid-liquid separation, drying, grinding and screening in sequence.

6. The preparation method according to any one of claims 2 to 5, characterized in that: The chemical formula of lithium aluminum titanium phosphate in the lithium aluminum titanium phosphate powder is Li 1+x Al x Ti 2-x (PO4)3、Li 1.3 Al 0.3 M1 y Ti 1.7-y (PO4)3、Li 1.3+z Al 0.3-z M2 z Ti 1.7 (PO4)3, or Li 1.3 Al 0.3-j M3 j Ti 1.7 Any one or a combination of at least two of (PO4)3; Among them, 0.1≤x≤0.5; 0≤y≤0.2, M1 is Zr and / or Hf; 0≤z≤0.2, M2 is any one of Ca, Mg or Sr or a combination of at least two; 0≤j≤0.2, M3 is any one of Y, Ga or Sc or a combination of at least two.

7. The preparation method according to any one of claims 2 to 6, characterized in that: The siloxane coupling agent includes any one of an alkyl siloxane coupling agent, a fluorine-containing siloxane coupling agent, an amino siloxane coupling agent, a vinyl siloxane coupling agent or a methacryloxy siloxane coupling agent, or a combination of at least two thereof; Preferably, the alkylsiloxane coupling agent includes any one or a combination of at least two of octadecyltrimethoxysilane, octadecyltriethoxysilane, hexadecyltrimethoxysilane, octyltrimethoxysilane or octyltriethoxysilane; Preferably, the fluorinated siloxane coupling agent includes any one of heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltriethoxysilane or trifluoropropylmethylcyclotrisiloxane, or a combination of at least two thereof; Preferably, the aminosiloxane coupling agent includes γ-aminopropyltriethoxysilane; Preferably, the vinyl siloxane coupling agent includes any one of vinyl triethoxy silane, vinyl trimethoxy silane or vinyl tri (β-methoxyethoxy) silane or a combination of at least two thereof; Preferably, the methacryloxysiloxane coupling agent includes methacryloxypropyltrimethoxysilane.

8. The preparation method according to any one of claims 2 to 7, characterized in that: The preparation method comprises: (1) firstly mixing a solvent and an acidic pH adjusting agent by stirring to obtain an acidic solvent with a pH of 3 to 5, and then mixing the obtained acidic solvent with a siloxane coupling agent by stirring to obtain an acidic siloxane coupling agent solution, wherein the mass ratio of the solvent to the siloxane coupling agent is (0.1 to 5):100; (2) drying lithium aluminum titanium phosphate powder having a D50 particle size of 0.5 to 2 μm at 300 to 400° C. for 2 to 4 hours, and then mixing the acidic siloxane coupling agent solution obtained in step (1) with the dried lithium aluminum titanium phosphate powder by ultrasonic stirring to obtain a remixed solution, wherein the mass ratio of the dried lithium aluminum titanium phosphate powder to the siloxane coupling agent in the acidic siloxane coupling agent solution is 200:(0.1 to 5); (3) The remixed liquid obtained in step (2) is heated in a water bath at 60 to 80° C. for 4 to 8 hours, cooled to 15 to 30° C., and the supernatant is poured out, and the alcohol washing and suction filtration are repeated at least once, and then vacuum drying is performed at 80 to 150° C. for 6 to 12 hours. The dried solid is then ground and sieved using a 200 to 400 mesh sieve to obtain a hydrophobically modified lithium aluminum titanium phosphate solid electrolyte.

9. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode sheet, a solid electrolyte layer and a negative electrode sheet; The positive electrode active material layer on the positive electrode sheet includes the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte according to claim 1, and the main component of the solid electrolyte layer is the hydrophobically modified lithium aluminum titanium phosphate solid electrolyte according to any one of claim 1.

10. The lithium-ion battery according to claim 9, characterized in that: The solid electrolyte layer is attached to the surface of the positive electrode sheet; Preferably, the positive electrode active material layer on the positive electrode sheet includes the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte, battery active materials, electronic conductive materials and binder; the solid electrolyte layer includes the hydrophobically modified lithium titanium aluminum phosphate solid electrolyte and binder; and the negative electrode sheet includes a metallic lithium negative electrode.

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