Lithium lanthanum titanium oxide material suitable for negative electrode additive as well as preparation method and application of lithium lanthanum titanium oxide material

Abstract

The invention belongs to the technical field of lithium ion battery materials, and discloses a lithium lanthanum titanium oxide material suitable for a negative electrode additive and a preparation method and application of the lithium lanthanum titanium oxide material. The material comprises an inner core and a coating layer coating the surface of the inner core, and the coating layer is an inorganic lithium salt. A nanoscale inorganic lithium salt coating layer with a low-surface-energy crystal face is constructed on the surface of an LLTO material, when the LLTO material serves as a negative electrode additive to be applied to a negative electrode, inorganic lithium salt serves as a nucleation site of an SEI film preferentially, and the SEI film is induced to grow on the surface of the negative electrode in an oriented mode; meanwhile, the inorganic lithium salt has a large number of lattice defects, a large number of uniformly-distributed nucleation centers are provided for lithium ion deposition, formation of an SEI film on the surface of the negative electrode is promoted, and consistency and integrity of SEI formed on the negative electrode are guaranteed; and in cooperation with the LLTO core material, the quality of the SEI membrane is improved, and meanwhile, a lithium ion rapid diffusion channel is constructed at the negative electrode, so that the dynamic performance and the cycle performance of the lithium ion battery are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery materials, and particularly relates to a lithium lanthanum titanium oxygen material suitable for a negative electrode additive and a preparation method and application thereof. BACKGROUND

[0002] Since the advent of lithium ion batteries in 1991, lithium ion batteries have developed rapidly and gradually penetrated into all aspects of people's life. However, as the application of lithium ion batteries becomes more and more extensive, some safety problems have also gradually emerged. Currently, commercialized lithium ion batteries are mainly prepared by using organic liquid electrolyte and inorganic lithium salt electrolyte. Since the organic liquid solvent is flammable and explosive, it is easy to cause thermal runaway and inevitably brings safety problems. Inorganic solid electrolyte has excellent thermal stability and mechanical properties, and is expected to fundamentally solve the safety performance of lithium ion batteries.

[0003] In the inorganic solid electrolyte system, Li 3x La 2 / 3-x W 1 / 3-2x TiO3(LLTO) has become a research hotspot due to its excellent lithium ion conductivity (10 -4 -10 -3 S / cm). This kind of material not only can be used as the core electrolyte of solid-state batteries, but also can be used as an electrode functional additive, which can significantly improve the rate performance and cycle stability of lithium ion batteries by optimizing the interface ion transmission.

[0004] The SEI film is a passivation film formed on the surface of the negative electrode in the first charging and discharging process of the lithium ion battery through the electrochemical reduction reaction of the electrolyte. As a "selective channel" for lithium ion transmission, it allows Li + to pass through but blocks electron conduction, thereby inhibiting the continuous decomposition of the electrolyte and ensuring the long cycle life of the lithium battery. In the traditional process, the SEI film is mainly generated in situ through the electrolyte reduction reaction, and its morphology and component distribution mainly depend on the spontaneous process of the electrolyte reduction reaction, which has two technical bottlenecks: one is that the reaction is uncontrollable, resulting in uneven product distribution, and the other is that the by-product (such as gaseous C2H4) affects the interface stability. Therefore, how to overcome the problem that the uniformity in the SEI film formation process is difficult to control has become an urgent problem to be solved. SUMMARY

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a lithium lanthanum titanium oxygen material suitable for a negative electrode additive.

[0006] The lithium lanthanum titanium oxygen material of the present application is coated with an inorganic lithium salt coating layer on the surface of the LLTO material. By precisely controlling the composition and thickness of the coating layer of the lithium lanthanum titanium oxygen material of the present application, a material with special structure and performance can be obtained. When the material is applied to a negative electrode fast ion conductor, the nucleation sites of the SEI film can be directionally induced, and ultimately a uniform distribution and enhanced chemical stability interface protection layer can be constructed on the surface of the negative electrode.

[0007] Another object of the present application is to provide a preparation method of the above-mentioned lithium lanthanum titanium oxygen material suitable for negative electrode additives.

[0008] Still another object of the present application is to provide the application of the above-mentioned lithium lanthanum titanium oxygen material in lithium ion batteries, in particular as a negative electrode additive.

[0009] The object of the present application is achieved by the following scheme: A lithium lanthanum titanium oxygen material, comprising an inner core, and a coating layer coated on the surface of the inner core, wherein the coating layer is an inorganic lithium salt.

[0010] Further, the coating layer is a nanoscale inorganic lithium salt.

[0011] Further, the coating layer is a nanoscale inorganic lithium salt with a low surface energy crystal plane.

[0012] Further, the inorganic lithium salt can be selected from at least one of Li2CO3, Li2O, LiOH, Li3N, Li2S, etc.

[0013] Further, the content of the inorganic lithium salt can be 0.05wt.%-0.5wt.%.

[0014] Further, the inner core is a perovskite type lithium lanthanum titanium oxide compound, with a chemical formula of Li 3x La 2 / 3-x TiO3, 0.04 < x < 0.17.

[0015] Further, the particle size D50 of the lithium lanthanum titanium oxygen material can be 100-800nm.

[0016] Further, the D50 / D10 of the lithium lanthanum titanium oxygen material is ≤2.

[0017] Further, the D90 / D10 of the lithium lanthanum titanium oxygen material is ≤4.

[0018] Further, the moisture content of the lithium lanthanum titanium oxygen material is <500ppm.

[0019] The lithium lanthanum titanium oxide material of the present application constructs a nanoscale inorganic lithium salt coating layer with low surface energy crystal face on the surface of the LLTO material. When the lithium lanthanum titanium oxide material is applied as a negative electrode additive, the inorganic lithium salt with low surface energy crystal face of the coating layer preferentially serves as a nucleation site of the SEI film, and induces the directional growth of the SEI film on the surface of the negative electrode. Meanwhile, the inorganic lithium salt of the coating layer has a large number of lattice defects, which provides a large number of uniformly distributed nucleation centers for lithium ion deposition, promotes the formation of the SEI film on the surface of the negative electrode, and ensures the consistency and integrity of the SEI formed on the negative electrode. By using the lithium lanthanum titanium oxide material of the present application to intervene in the formation of the SEI film, the uniformity of the negative electrode SEI film is improved, and meanwhile, the LLTO core material with high ionic conductivity is used in cooperation, so that the lithium ion rapid diffusion channel is constructed on the negative electrode while the quality of the SEI film is improved, and the kinetic performance and cycle performance of the lithium ion battery are significantly improved.

[0020] Based on the particularity of the structure and performance of the lithium lanthanum titanium oxide material of the present application, the present application also provides the application of the above-mentioned lithium lanthanum titanium oxide material in lithium ion batteries, in particular as a negative electrode additive.

[0021] The present application also provides a preparation method of the above-mentioned lithium lanthanum titanium oxide material, comprising the following steps: adding LLTO material powder into a solvent to prepare a slurry, adding inorganic lithium salt and a dispersing agent, sanding, drying to obtain powder particles; and heat treating the powder particles to obtain the lithium lanthanum titanium oxide material.

[0022] Further, the chemical formula of the LLTO material is Li 3x La 2 / 3-x TiO3, 0.04 < x < 0.17.

[0023] Further, the addition amount of the inorganic lithium salt can be 0.05wt.%-0.5wt.% of the mass of the LLTO material powder.

[0024] Further, the inorganic lithium salt can be selected from at least one of Li2CO3, Li2O, LiOH, Li3N, Li2S, etc.

[0025] Further, the addition amount of the dispersing agent can be 0.1wt.%-0.5wt.% of the mass of the LLTO material powder.

[0026] Further, the dispersing agent can be selected from at least one of PVP, PEG, CMC, etc.

[0027] Further, the temperature of the heat treatment can be 300-600℃, and the heat treatment time can be 2h-6h.

[0028] Further, the heat treatment is carried out in an argon atmosphere.

[0029] Further, the solvent can be selected from at least one of anhydrous ethanol, isopropanol, propanol, etc.

[0030] Further, the solid content of the slurry can be 20 - 50%.

[0031] Further, the slurry is prepared under an inert atmosphere.

[0032] Further, the slurry is preferably dispersed evenly in a disperser.

[0033] Further, the LLTO material powder is preferably the sifted material with a mesh size of 50 or more.

[0034] Further, the preferred set parameters for the sanding are: rotation speed of 1500 - 3000 rpm, particle size control d50 = 100 - 800 nm, D50 / D10 ≤ 2, D90 / D10 ≤ 4.

[0035] Further, the drying can be a conventional drying method, such as drying in a vacuum drying oven, air drying, etc.

[0036] In the preparation process of the method of the present invention, liquid-phase mechanical grinding is adopted. By precisely controlling the grinding process, the LLTO and inorganic lithium salt powder particles are efficiently refined to the nanometer range, and nanometer powders with a narrow particle size distribution are obtained. This nanometer treatment significantly increases the specific surface area of LLTO and inorganic lithium salts, exposes more active sites, and greatly improves the interfacial bonding strength between the coating agent powder particles and the matrix material. At the same time, a dispersant is introduced into the grinding system. Through the steric hindrance effect and electrostatic effect of the dispersant, the agglomeration of nanometer particles is inhibited, and the coating uniformity of the inorganic lithium salt is improved. Thus, a lithium lanthanum titanate material with inorganic lithium salt uniformly coated on the surface of LLTO is prepared.

[0037] The LLTO material powder used in the method of the present invention can be a conventional LLTO material in the art, with the chemical formula Li 3x La 2 / 3-x TiO3, 0.04 < x < 0.17. The LLTO material powder of the present invention can be commercially available or prepared by a conventional method. For example, it can be prepared by a method including the following steps: (1) Weigh the lithium source, titanium source, and lanthanum source according to the stoichiometric ratio of the chemical formula Li 3x La 2 / 3-x TiO3, 0.04 < x < 0.17; the lithium source can be selected from at least one of lithium hydroxide, lithium carbonate, lithium phosphate, lithium acetate, lithium nitrate, etc.; the titanium source can be selected from at least one of titanium dioxide, titanium nitrate, titanium oxalate, etc.; the lanthanum source can be selected from at least one of lanthanum hydroxide, lanthanum oxide, lanthanum carbonate, lanthanum nitrate, etc.; (2) mixing the lithium source, the titanium source and the lanthanum source to prepare a slurry with solid content of 20-50%, and performing wet mixing and drying treatment to obtain dry powder a; (3) calcining the dry powder a in an air atmosphere to obtain the LLTO material.

[0038] Further, the heating rate of the calcination can be selected as 3-5 DEG C / min, the calcination temperature can be selected as 900-1300 DEG C, and the calcination duration can be selected as 4-16 h.

[0039] Further, the wet mixing can be selected from high-energy ball milling, sand milling and the like.

[0040] Further, the drying treatment can be performed by spray drying, vacuum drying box drying, air drying and the like.

[0041] If the particle size of the purchased or prepared LLTO material is large, the LLTO material can be crushed by a crusher and screened by a vibrating screen, so that the undersize material with mesh number greater than or equal to 50 is obtained for preparation.

[0042] The LLTO is introduced into the negative electrode in the form of an additive, a uniform inorganic lithium salt is coated on the surface of the LLTO, the inorganic lithium salt is used as a nucleation site of the SEI film, the uniform growth of the SEI film is controlled, a dense and uniform SEI is formed, the deposition of metallic lithium and the corrosion of the electrolyte to the negative electrode are reduced, and the electrochemical performance of the lithium ion battery is improved; the LLTO core material with high ionic conductivity is used in cooperation, the quality of the SEI film is improved, and a lithium ion rapid diffusion channel is constructed in the negative electrode, so that the kinetic performance and the cycle performance of the lithium ion battery are significantly improved.

[0043] The present application has the following advantages: (1) The lithium lanthanum titanium oxide material is used in the negative electrode process in the form of an additive, a uniform inorganic lithium salt is coated on the surface of the LLTO, the inorganic lithium salt can be used as a nucleation site, the uniform growth of the SEI film is controlled, a dense and uniform SEI is formed, the deposition of metallic lithium and the corrosion of the electrolyte to the negative electrode are reduced, and the electrochemical performance of the lithium ion battery is improved; (2) The inorganic lithium salt with a specific low surface energy crystal face is used as the coating layer of the LLTO, and the main role is reflected in the double regulation mechanism: ① the low surface energy crystal face becomes the directional nucleation site of the solid-state electrolyte interface film (SEI) by reducing the interface energy barrier, and induces the growth of the SEI film along the negative electrode surface; ② the specific lattice defect structure of the coating layer provides a large number of uniformly distributed nucleation centers for the deposition of lithium ions, and promotes the formation of the SEI film on the negative electrode surface; (3) The lithium lanthanum titanium oxygen material of the present application has an inorganic lithium salt coating layer cooperated with an LLTO inner core material with high ion conductivity, which improves the quality of SEI film and builds lithium ion rapid diffusion channel in the negative electrode, so that the kinetic performance and cycle performance of the lithium ion battery are significantly improved. DETAILED DESCRIPTION

[0044] The present application will be further described in detail below with reference to examples, but the embodiments of the present application are not limited thereto. The materials involved in the following examples can be obtained from commercial channels if not otherwise specified. The methods are conventional methods if not otherwise specified. The amounts of components are measured by mass parts, volume parts, g and mL. Example 1

[0045] A lithium lanthanum titanium oxygen material suitable for negative electrode additive is of core-shell structure, and the inner core has a structural formula of Li 0.33 La 0.557 TiO3, and the surface is coated with Li3N with a content of 0.1 wt.%.

[0046] (1) Preparation of the inner core LLTO material: According to the structural formula Li 0.33 La 0.557 TiO3, lithium carbonate 138.92 mass parts, lanthanum oxide 1033.30 mass parts and titanium dioxide 910.00 mass parts are weighed respectively; and mixed with anhydrous ethanol to prepare a slurry with a solid content of 40%, the amount of anhydrous ethanol added is 3144.16 mass parts, the rotation speed of the dispersing machine is 2000 rpm, and the mixing time is 0.5 h. The prepared slurry is ground by sand milling, the sand milling speed is 1500 rpm, and the sand milling time is 1 h. After sand milling, the material is placed in a vacuum drying box for drying, the drying box temperature is set to 80℃, the drying time is 12 h, and dry powder a is obtained. The dry powder a is placed in a high-temperature box furnace for sintering, the sintering temperature is 1150℃, the sintering time is 12 h, the heating rate is 3℃ / min, and LLTO material is obtained.

[0047] (2) Preparation of the lithium lanthanum titanium oxygen material: ① The sintered LLTO material is coarsely broken by a crusher, and sieved by a vibrating screen, the mesh size of the screen is 50 meshes, and the undersize material with a mesh size greater than or equal to 50 meshes is obtained for preparation; ② The LLTO material powder and anhydrous ethanol are prepared into a slurry with a solid content of 40% in an inert gas glove box, the weight of the powder is 1000 mass parts, the amount of anhydrous ethanol is 1500 mass parts, the rotation speed of the dispersing machine is 2000 rpm, and the mixing time is 0.5 h; ③ 1 mass part of Li3N is added to the slurry and mixed uniformly; and 5 mass parts of PVP are further added and mixed uniformly; (4) The slurry is sand-milled at a speed of 1800 rpm, and the particle size is controlled as follows: d50=300 nm, D50 / D10≤2, and D90 / D10≤4. After the particle size is qualified, the material is dried in a vacuum drying box at a temperature of 80°C for 12 hours; (5) The dried powder sample is heat-treated in an argon atmosphere at a temperature of 400°C for 2 hours to obtain the lithium lanthanum titanium oxide material. Example 2

[0048] A lithium lanthanum titanium oxide material suitable for a negative electrode additive has a core-shell structure, and the inner core has a structure of Li 0.33 La 0.557 TiO3, and is coated with Li2CO3 on the surface, and the content is 0.1 wt.%.

[0049] (1) The preparation of the inner core LLTO material is the same as in Example 1.

[0050] (2) Preparation of the lithium lanthanum titanium oxide material: (1) The preparation of the inner core LLTO material is the same as in Example 1. (2) The LLTO material powder and anhydrous ethanol are prepared into a slurry with a solid content of 40% in an inert gas glove box, the powder is 1000 parts by mass, the anhydrous ethanol is 1500 parts by mass, the speed of the dispersing machine is 2000 rpm, and the mixing time is 0.5 hours; (3) 1 part by mass of Li2CO3 is added to the slurry and mixed uniformly, and then 5 parts by mass of PVP is added and mixed uniformly; (4) The uniformly mixed slurry is sand-milled at a speed of 1800 rpm, and the particle size is controlled as follows: d50=300 nm, D50 / D10≤2, and D90 / D10≤4. After the particle size is qualified, the material is dried in a vacuum drying box at a temperature of 80°C for 12 hours; (5) The dried powder sample is heat-treated in an argon atmosphere at a temperature of 400°C for 2 hours to obtain the lithium lanthanum titanium oxide material. Example 3

[0051] A lithium lanthanum titanium oxide material suitable for a negative electrode additive has a core-shell structure, and the inner core has a structure of Li 0.33 La 0.557 TiO3, and is coated with Li2O on the surface, and the content is 0.1 wt.%.

[0052] (1) The preparation of the inner core LLTO material is the same as in Example 1.

[0053] (2) Preparation of the lithium lanthanum titanium oxide material: ①The sintered LLTO material is coarsely broken by a crusher, and sieved by a vibrating screen, with a mesh size of 50 mesh, to obtain undersize material with a mesh size of 50 or more for preparation; ②The LLTO material powder and anhydrous ethanol are prepared into a slurry with a solid content of 40% in an inert gas glove box, with the powder weighing 1000 parts by mass and the anhydrous ethanol weighing 1500 parts by mass, the disperser rotating at 2000 rpm, and the mixing time being 0.5 h; ③1 part by mass of Li2O is added to the slurry and mixed uniformly, and then 5 parts by mass of PVP is added and mixed uniformly; ④The uniformly mixed slurry is sand-milled at a speed of 1800 rpm, with the particle size controlled as follows: d50=300 nm, D50 / D10≤2, and D90 / D10≤4. After the particle size is qualified, the material is dried in a vacuum drying oven at a temperature of 80°C for 12 h; ⑤The dried powder sample is heat-treated in an argon atmosphere at a temperature of 400°C for 2 h to prepare the lithium lanthanum titanium oxide material. Example 4

[0054] A lithium lanthanum titanium oxide material suitable for a negative electrode additive has a core-shell structure, with the inner core structure being Li 0.33 La 0.557 TiO3, and the surface being coated with LiOH at a content of 0.1 wt.%.

[0055] (1) The preparation of the inner core LLTO material is the same as in Example 1.

[0056] (2) Preparation of the lithium lanthanum titanium oxide material: ①The sintered LLTO material is coarsely broken by a crusher, and sieved by a vibrating screen, with a mesh size of 50 mesh, to obtain undersize material with a mesh size of 50 or more for preparation; ②The LLTO material powder and anhydrous ethanol are prepared into a slurry with a solid content of 40% in an inert gas glove box, with the powder weighing 1000 parts by mass and the anhydrous ethanol weighing 1500 parts by mass, the disperser rotating at 2000 rpm, and the mixing time being 0.5 h; ③1 part by mass of LiOH is added to the slurry and mixed uniformly, and then 5 parts by mass of PVP is added and mixed uniformly; ④The uniformly mixed slurry is sand-milled at a speed of 1800 rpm, with the particle size controlled as follows: d50=300 nm, D50 / D10≤2, and D90 / D10≤4. After the particle size is qualified, the material is dried in a vacuum drying oven at a temperature of 80°C for 12 h; ⑤The dry powder sample is placed in an argon atmosphere for heat treatment, the heat treatment temperature is 400℃, and the heat treatment time is 2h, to prepare the lithium lanthanum titanium oxide material. Example 5

[0057] A lithium lanthanum titanium oxide material suitable for negative electrode additives is a core-shell structure, the inner core structure is Li 0.33 La 0.557 TiO3, and the surface is coated with Li3N with a content of 0.05wt.%.

[0058] (1) The preparation of the inner core LLTO material is the same as in Example 1.

[0059] (2) Preparation of the lithium lanthanum titanium oxide material: ①The sintered LLTO material is coarsely broken by a crusher, and sieved by a vibrating screen, the mesh size of the screen is 50 meshes, to obtain undersize material with a mesh size greater than or equal to 50 meshes for preparation; ②The LLTO material powder and anhydrous ethanol are prepared into a slurry with a solid content of 40% in an inert gas glove box, the powder is 1000 parts by mass, the anhydrous ethanol is 1500 parts by mass, the rotational speed of the dispersing machine is 2000rpm, and the mixing time is 0.5h; ③0.5 parts by mass of Li3N is added to the slurry and mixed uniformly, and then 5 parts by mass of PVP is added and mixed uniformly; ④The above mixed uniform slurry is sand milled, the sand milling speed is 1800rpm, the particle size control is d50=300nm, D50 / D10≤2, and D90 / D10≤4. After the particle size is qualified, the material is placed in a vacuum drying oven for drying, the drying temperature is 80℃, and the drying time is 12h; ⑤The dry powder sample is placed in an argon atmosphere for heat treatment, the heat treatment temperature is 400℃, and the heat treatment time is 2h, to prepare the lithium lanthanum titanium oxide material. Example 6

[0060] A lithium lanthanum titanium oxide material suitable for negative electrode additives is a core-shell structure, the inner core structure is Li 0.33 La 0.557 TiO3, and the surface is coated with Li3N with a content of 0.3wt.%.

[0061] (1) The preparation of the inner core LLTO material is the same as in Example 1.

[0062] (2) Preparation of the lithium lanthanum titanium oxide material: ①The sintered LLTO material is coarsely broken by a crusher, and sieved by a vibrating screen, the mesh size of the screen is 50 meshes, to obtain undersize material with a mesh size greater than or equal to 50 meshes for preparation; ② The LLTO material powder and anhydrous ethanol were prepared into a slurry with a solid content of 40% in an inert gas glove box. The powder weighed 1000 parts by weight and the anhydrous ethanol weighed 1500 parts by weight. The speed of the disperser was 2000 rpm and the mixing time was 0.5 h. ③ Add 3 parts by weight of Li3N to the slurry and mix well; then add 5 parts by weight of PVP and mix well. ④ The above-mentioned uniformly mixed slurry is milled at a speed of 1800 rpm. The particle size is controlled as follows: d50 = 300 nm, D50 / D10 ≤ 2, D90 / D10 ≤ 4. After the particle size is qualified, the material is placed in a vacuum drying oven for drying at a temperature of 80℃ for 12 hours. ⑤ The dried powder sample was placed in an argon atmosphere for heat treatment at a temperature of 400℃ for 2 hours to prepare lithium lanthanum titanium oxide material. Example 7

[0063] A lithium lanthanum titanium oxide material suitable for use as an anode additive has a core-shell structure, with the core structure being Li 0.33 La 0.557 TiO3 with Li3N coating, content 0.5 wt.%.

[0064] (1) The preparation of the core LLTO material is the same as in Example 1.

[0065] (2) Preparation of lithium lanthanum titanium oxide materials: ① The LLTO material obtained by sintering is coarsely crushed using a crusher; then it is screened using a vibrating screen with a mesh size of 50. The undersize material with a mesh size of 50 or greater is used for preparation. ② The LLTO material powder and anhydrous ethanol were prepared into a slurry with a solid content of 40% in an inert gas glove box. The powder weighed 1000 parts by weight and the anhydrous ethanol weighed 1500 parts by weight. The speed of the disperser was 2000 rpm and the mixing time was 0.5 h. ③ Add 5 parts by weight of Li3N to the slurry and mix well; then add 5 parts by weight of PVP and mix well. ④ The above-mentioned uniformly mixed slurry is milled at a speed of 1800 rpm. The particle size is controlled as follows: d50 = 300 nm, D50 / D10 ≤ 2, D90 / D10 ≤ 4. After the particle size is qualified, the material is placed in a vacuum drying oven for drying at a temperature of 80℃ for 12 hours. ⑤ The dried powder sample was placed in an argon atmosphere for heat treatment at a temperature of 400℃ for 2 hours to prepare lithium lanthanum titanium oxide material. Example 8

[0066] A lithium lanthanum titanium oxide material suitable for use as an anode additive has a core-shell structure, with the core structure being Li0.18 La 0.607 TiO3, surface coated with Li2CO3, content 0.1 wt.%.

[0067] (1) The preparation method of the inner core LLTO material is the same as in Example 1, except that the structure Li 0.18 La 0.607 TiO3, respectively, lithium carbonate 73 parts by mass, lanthanum oxide 1090 parts by mass, and titanium dioxide 881 parts by mass are weighed for preparation.

[0068] (2) Preparation of lithium lanthanum titanium oxide material: ①The sintered LLTO material is coarsely broken by a crusher, and sieved by a vibrating screen, with a mesh size of 50 meshes, to obtain undersize material with a mesh size greater than or equal to 50 meshes for preparation; ②The LLTO material powder and anhydrous ethanol are prepared into a slurry with a solid content of 40% in an inert gas glove box, with 1000 parts by mass of powder and 1500 parts by mass of anhydrous ethanol, a disperser speed of 2000 rpm, and a mixing time of 0.5 h; ③1 part by mass of Li2CO3 is added to the slurry and mixed uniformly; then 5 parts by mass of PVP is added and mixed uniformly; ④The above uniformly mixed slurry is sand milled at a speed of 1800 rpm, with a particle size control of d50=300 nm, D50 / D10≤2, and D90 / D10≤4. After the particle size is qualified, the material is placed in a vacuum drying oven for drying, with a drying temperature of 80°C and a drying time of 12 h; ⑤The dried powder sample is placed in an argon atmosphere for heat treatment, with a heat treatment temperature of 400°C and a heat treatment time of 2 h, to prepare the lithium lanthanum titanium oxide material. Example 9

[0069] A lithium lanthanum titanium oxide material suitable for negative electrode additives is of a core-shell structure, with the structure of the inner core being Li 0.24 La 0.587 TiO3, surface coated with Li2CO3, content 0.1 wt.%.

[0070] (1) The preparation method of the inner core LLTO material is the same as in Example 1, except that the structure Li 0.24 La 0.587 TiO3, respectively, lithium carbonate 73 parts by mass, lanthanum oxide 1090 parts by mass, and titanium dioxide 881 parts by mass are weighed for preparation.

[0071] (2) Preparation of lithium lanthanum titanium oxide material: ①The sintered LLTO material is coarsely broken by a crusher, and sieved by a vibrating screen, with a mesh size of 50 meshes, to obtain undersize material with a mesh size greater than or equal to 50 meshes for preparation; 2. The LLTO material powder and anhydrous ethanol are prepared into a slurry with a solid content of 40% in an inert gas glove box, the powder weight is 1000 parts by mass, anhydrous ethanol is 1500 parts by mass, the rotation speed of the dispersing machine is 2000 rpm, and the mixing time is 0.5 h; 3. 1 part by mass of Li2CO3 is added to the slurry and uniformly mixed; then 5 parts by mass of PVP is added and uniformly mixed; 4. The uniformly mixed slurry is subjected to sand milling, the sand milling rotation speed is 1800 rpm, the particle size control is d50=300 nm, D50 / D10≤2, and D90 / D10≤4. After the particle size is qualified, the material is placed in a vacuum drying oven for drying, the drying temperature is 80°C, and the drying time is 12 h; 5. The dried powder sample is placed in an argon atmosphere for heat treatment, the heat treatment temperature is 400°C, and the heat treatment time is 2 h, to prepare a lithium lanthanum titanium oxide material. Example 10

[0072] A lithium lanthanum titanium oxide material suitable for a negative electrode additive is in a core-shell structure, the inner core structure is Li 0.48 La 0.507 TiO3, and the surface is coated with Li2CO3 with a content of 0.1 wt.%.

[0073] (1) The preparation method of the inner core LLTO material is the same as that in Example 1, except that according to the structure Li 0.48 La 0.507 TiO3, lithium carbonate 209 parts by mass, lanthanum oxide 973 parts by mass, and titanium dioxide 942 parts by mass are respectively weighed and used for preparation.

[0074] (2) Preparation of the lithium lanthanum titanium oxide material: 1. The sintered LLTO material is coarsely broken by a crusher; and is sieved by a vibrating screen, the mesh size of the screen is 50 meshes, to obtain undersize material with a mesh size greater than or equal to 50 meshes for preparation; 2. The LLTO material powder and anhydrous ethanol are prepared into a slurry with a solid content of 40% in an inert gas glove box, the powder weight is 1000 parts by mass, anhydrous ethanol is 1500 parts by mass, the rotation speed of the dispersing machine is 2000 rpm, and the mixing time is 0.5 h; 3. 1 part by mass of Li2CO3 is added to the slurry and uniformly mixed; then 5 parts by mass of PVP is added and uniformly mixed; 4. The uniformly mixed slurry is subjected to sand milling, the sand milling rotation speed is 1800 rpm, the particle size control is d50=300 nm, D50 / D10≤2, and D90 / D10≤4. After the particle size is qualified, the material is placed in a vacuum drying oven for drying, the drying temperature is 80°C, and the drying time is 12 h; ⑤ The dried powder sample was placed in an argon atmosphere for heat treatment at a temperature of 400℃ for 2 hours to prepare lithium lanthanum titanium oxide material. Example 11

[0075] A lithium lanthanum titanium oxide material suitable for use as an anode additive has a core-shell structure, with the core structure being Li 0.33 La 0.557 TiO3 with Li2CO3 coating on the surface, content 0.1 wt.%.

[0076] (1) The preparation of the core LLTO material is the same as in Example 1.

[0077] (2) The preparation of lithium lanthanum titanium oxide material is the same as in Example 2, except that the particle size control is set in step ④: d50=150 nm. Example 12

[0078] A lithium lanthanum titanium oxide material suitable for use as an anode additive has a core-shell structure, with the core structure being Li 0.33 La 0.557 TiO3 with Li2CO3 coating on the surface, content 0.1 wt.%.

[0079] (1) The preparation of the core LLTO material is the same as in Example 1.

[0080] (2) The preparation of lithium lanthanum titanium oxide material is the same as in Example 2, except that the particle size control is set in step ④: d50=600 nm. Example 13

[0081] A lithium lanthanum titanium oxide material suitable for use as an anode additive has a core-shell structure, with the core structure being Li 0.33 La 0.557 TiO3 with Li2CO3 coating on the surface, content 0.1 wt.%.

[0082] (1) The preparation of the core LLTO material is the same as in Example 1.

[0083] (2) The preparation of lithium lanthanum titanium oxide material is the same as in Example 2, except that the particle size control is set in step ④: d50=800 nm. Example 14

[0084] A lithium lanthanum titanium oxide material suitable for use as an anode additive has a core-shell structure, with the core structure being Li 0.33 La 0.557 TiO3, with Li2O coated on the surface, content 0.1 wt.%.

[0085] (1) The preparation of the core LLTO material is the same as in Example 3.

[0086] (2) The lithium lanthanum titanium oxide material is prepared according to the method of Example 3, except that the dispersant in step (3) is replaced by PEG. Example 15

[0087] A lithium lanthanum titanium oxide material suitable for use as a negative electrode additive is in a core-shell structure, and the core structure is Li 0.33 La 0.557 TiO3, and the surface is coated with Li2O, with a content of 0.1 wt.%.

[0088] (1) The core LLTO material is prepared according to the method of Example 3.

[0089] (2) The lithium lanthanum titanium oxide material is prepared according to the method of Example 3, except that the dispersant in step (3) is replaced by CMC. Comparative Example 1

[0090] A lithium lanthanum titanium oxide material is prepared, with a structure of Li 0.33 La 0.557 TiO3, and the surface is not coated with an inorganic lithium salt: (1) The LLTO material is prepared according to the method of Example 1.

[0091] (2) The preparation method is the same as that of Example 1, except that 1 part by mass of Li3N is not added for the reaction. Comparative Example 2

[0092] A lithium lanthanum titanium oxide material is in a core-shell structure, and the core structure is Li 0.48 La 0.507 TiO3, and the surface is coated with Li3N, with a content of 0.03 wt.%.

[0093] (1) The core LLTO material is prepared according to the method of Example 1.

[0094] (2) The lithium lanthanum titanium oxide material is prepared according to the method of Example 1, except that 0.3 parts by mass of Li3N is added for the reaction. Comparative Example 3

[0095] A lithium lanthanum titanium oxide material is in a core-shell structure, and the core structure is Li 0.48 La 0.507 TiO3, and the surface is coated with Li3N, with a content of 0.8 wt.%.

[0096] (1) The core LLTO material is prepared according to the method of Example 1.

[0097] (2) The lithium lanthanum titanium oxide material is prepared according to the method of Example 1, except that 8 parts by mass of Li3N is added for the reaction. Comparative Example 4

[0098] A lithium lanthanum titanium oxide material is in a core-shell structure, and the core structure is Li 0.33La 0.557 TiO3, coated with Li2CO3 on the surface, content 0.1 wt.%.

[0099] (1) The preparation method of the inner core LLTO material is the same as in Example 1.

[0100] (2) The preparation of the lithium lanthanum titanium oxide material is the same as in Example 2, except that the particle size control is set in step IV: d50 = 50 nm. Comparative Example 5

[0101] A lithium lanthanum titanium oxide material, which is a core-shell structure, the inner core structure is Li 0.33 La 0.557 TiO3, coated with Li2CO3 on the surface, content 0.1 wt.%.

[0102] (1) The preparation method of the inner core LLTO material is the same as in Example 1.

[0103] (2) The preparation of the lithium lanthanum titanium oxide material is the same as in Example 2, except that the particle size control is set in step IV: d50 = 1000 nm.

[0104] The materials prepared in the above examples and comparative examples were tested for performance, the method is as follows, and the test results are shown in Table 1: (1) Ion conductivity test: the material to be tested was cold isostatic pressed at 200-250 MPa, sintered at 1200-1350°C for 12-24h, and then polished and gold sprayed to test EIS to obtain the ion conductivity; (2) Battery cycle test: the material to be tested was added to the slurry when the graphite negative electrode slurry was uniformly grinded, the addition amount was 0.5wt.%-1.5wt.%, and then the prepared negative electrode sheet and the positive electrode sheet of the ternary material were assembled into a battery. Formation process: first 0.01C-0.03C constant current charging for 1-2h, and then 0.1C constant current charging to 4.0V; (3) Cycle test: the battery was placed in a 25°C constant temperature box, and the battery was subjected to 1C charging and discharging, the charging cutoff voltage was 4.2V, the discharging cutoff voltage was 3.0V, the capacity retention rate was the percentage ratio of the discharging capacity of the Nth cycle to the initial cycle discharging capacity, and the test was stopped when the capacity retention rate decreased to 80%.

[0105] Table 1

[0106] As shown in the table, the lithium lanthanum titanium oxygen material of the present application is coated with a layer of inorganic lithium salt with low surface energy crystal surface on the surface of LLTO, and when applied to the negative electrode, the cycle performance of the battery is obviously improved, mainly due to the improvement of the SEI film, and within the coating amount range adopted in the present application, the surface coating modification basically has no effect on the ionic conductivity of the core LLTO material; however, with the increase of the coating amount, the ionic conductivity of LLTO will decrease, therefore, the coating amount is preferably controlled within 0.05wt.%-0.5wt.%. According to the comparison, the ionic conductivity of LLTO material with different x values has differences, but has no obvious effect on the cycle performance of the battery, therefore, the LLTO material within the x value range of the present application meets the application requirements.

[0107] At the same time, the comparison shows that different particle sizes have an effect on the cycle performance of the LLTO ceramic sheet machine battery. For the ionic conductivity of the ceramic sheet: too small particle size can easily cause particle agglomeration, resulting in a decrease in the density of the ceramic sheet and the ionic conductivity; too large particle size can cause too many residual pores, and the density of the ceramic sheet is still decreased, and the ionic conductivity is also decreased. For the cycle performance of the battery: particle agglomeration and too large particle size can affect the distribution of the LLTO composite material in the negative electrode, resulting in the failure to improve the SEI film of the negative electrode and improve the cycle performance of the battery. Therefore, the use of a suitable range of particle size is beneficial to the lithium lanthanum titanium oxygen material to play a role in improving the cycle performance of the battery.

[0108] The above embodiments are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A lithium lanthanum titanium oxide material, characterized in that The lithium lanthanum titanium oxide material comprises an inner core and a coating layer coated on the surface of the inner core, and the coating layer is an inorganic lithium salt.

2. The lithium lanthanum titanium oxide material of claim 1, wherein: The inorganic lithium salt is at least one selected from Li2CO3, Li2O, LiOH, Li3N and Li2S.

3. The lithium lanthanum titanium oxide material of claim 1, wherein: The content of the inorganic lithium salt is 0.05wt.%-0.5wt.%.

4. The lithium lanthanum titanium oxide material of claim 1, wherein: The inner core is a perovskite lithium lanthanum titanium oxide compound, chemical formula is Li 3x La 2 / 3-x TiO3, 0.04 < x < 0.

17.

5. The lithium lanthanum titanium oxide material of claim 1, wherein: The particle size D50 of the lithium lanthanum titanium oxide material is 100-800nm.

6. Use of the lithium lanthanum titanium oxide material according to any one of claims 1-5 as a negative electrode additive in a lithium ion battery.

7. A process for the preparation of a lithium lanthanum titanium oxide material as claimed in any one of claims 1 to 5, characterised in that The method comprises the following steps: The LLTO material powder is added into a solvent to prepare a slurry, an inorganic lithium salt and a dispersant are added, sanding and drying are performed to obtain powder particles, and the powder particles are subjected to heat treatment to obtain the lithium lanthanum titanium oxide material.

8. The method of claim 7, wherein: The addition amount of the inorganic lithium salt is 0.05wt.%-0.5wt.% of the mass of the LLTO material powder, and the addition amount of the dispersant is 0.1wt.%-0.5wt.% of the mass of the LLTO material powder.

9. The method of claim 7, wherein: The dispersant is at least one selected from PVP, PEG and CMC.

10. The method of claim 7, wherein: The temperature of the heat treatment is 300-600℃, and the heat treatment time is 2h-6h.

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