阅读说明：本技术 四氯铝酸锂和碳纳米管包覆钛酸锂的复合材料、其制备方法及用途 (Composite material of lithium tetrachloroaluminate and carbon nanotube coated lithium titanate, preparation method and application thereof ) 是由 张弘旭 吴小珍 杨顺毅 杨才德 黄友元 于 2018-06-20 设计创作，主要内容包括：本发明涉及一种四氯铝酸锂和碳纳米管包覆钛酸锂的复合材料、其制备方法及用途。所述复合材料包括由钛酸锂内核和包覆在所述内核表面的四氯铝酸锂包覆层构成的复合颗粒,以及包覆在所述复合颗粒表面的碳纳米管层。所述方法包括：1)采用ALD方法在钛酸锂颗粒的表面交替沉积氯化锂和三氯化铝,在钛酸锂颗粒的表面形成四氯铝酸锂包覆层,得到复合颗粒；2)将复合颗粒和碳纳米管加入到水醇混合溶剂中,球磨,喷雾干燥,得到复合材料。本发明的复合材料为双层包覆结构,其结构稳定,具有克容量高,倍率性能和导电性能好,循环性能优秀,嵌、脱锂能力良好的特点。本发明的方法操作简洁,对环境友好,易于实现工业化生产。(The invention relates to a composite material of lithium tetrachloroaluminate and carbon nanotube-coated lithium titanate, a preparation method and application thereof. The composite material comprises composite particles and a carbon nanotube layer, wherein the composite particles are composed of a lithium titanate inner core, a lithium aluminum tetrachloride coating layer coated on the surface of the inner core, and the carbon nanotube layer is coated on the surface of the composite particles. The method comprises the following steps: 1) depositing lithium chloride and aluminum trichloride on the surface of lithium titanate particles alternately by adopting an ALD method, and forming a lithium aluminum tetrachloride coating layer on the surface of the lithium titanate particles to obtain composite particles; 2) and adding the composite particles and the carbon nano tubes into a water-alcohol mixed solvent, carrying out ball milling, and carrying out spray drying to obtain the composite material. The composite material has a double-layer coating structure, has a stable structure, and has the characteristics of high gram volume, good rate capability and conductivity, excellent cycle performance and good lithium intercalation and deintercalation capability. The method of the invention has simple operation, is environment-friendly and is easy to realize industrial production.)

1. The composite material of lithium tetrachloroaluminate and carbon nanotube-coated lithium titanate is characterized by comprising composite particles and a carbon nanotube layer, wherein the composite particles are composed of a lithium titanate inner core, a lithium tetrachloroaluminate coating layer coated on the surface of the inner core, and the carbon nanotube layer is coated on the surface of the composite particles.

2. The composite material according to claim 1, wherein the composite particles are prepared by a method comprising: and (3) alternately depositing lithium chloride and aluminum trichloride on the surface of the lithium titanate particles by adopting an atomic layer chemical vapor deposition (ALD) method, and forming a lithium aluminum tetrachloride coating layer on the surface of the lithium titanate particles to obtain the composite particles.

3. Composite material according to claim 1 or 2, characterized in that the chemical formula of the lithium titanate core is Li₄Ti₅O₁₂；

Preferably, the lithium titanate core has a D50 of 6-10 μm;

preferably, the chemical formula of the lithium aluminum tetrachloride is LiAlCl₄；

Preferably, the thickness of the lithium aluminum tetrachloride coating layer is 0.5 nm-5 nm;

preferably, the length of the carbon nano tube is 5-15 μm, and the diameter is 10-30 nm;

preferably, the mass percent of the carbon nano tube is 0.5-5% based on the total mass of the composite material as 100%.

4. A method of preparing a composite of lithium tetrachloroaluminate and carbon nanotube coated lithium titanate according to any one of claims 1 to 3, characterized in that it comprises the following steps:

(1) depositing lithium chloride and aluminum trichloride on the surface of lithium titanate particles alternately by adopting an atomic layer chemical vapor deposition (ALD) method, and forming a lithium aluminum tetrachloride coating layer on the surface of the lithium titanate particles to obtain composite particles;

(2) and adding the composite particles and the carbon nano tubes into a water-alcohol mixed solvent, performing ball milling and spray drying to obtain the composite material of lithium aluminum tetrachloride and carbon nano tube coated lithium titanate.

5. The process of claim 4, wherein the lithium titanate particles of step (1) are prepared by the process of:

(A) mixing an organic additive and water to prepare a mixed solvent;

(B) adding a lithium source and a titanium source into the mixed solvent obtained in the step (A) to obtain slurry;

(C) performing ball milling, drying, sintering and crushing on the slurry obtained in the step (B) to obtain lithium titanate particles;

preferably, the organic additive in step (a) is any one or a combination of at least two of polyethylene glycol, polyacrylamide, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, soluble starch or branched starch, preferably any one or a combination of two of polyethylene glycol or polyacrylamide;

preferably, in the mixed solvent in the step (A), the volume ratio of the organic additive to the water is 0.4-1;

preferably, the lithium source in step (B) is selected from any one or a combination of at least two of lithium hydroxide, lithium carbonate, lithium acetate, lithium sulfate, lithium iodide or lithium phosphate, preferably any one or a combination of two of lithium hydroxide or lithium carbonate;

preferably, the titanium source in step (B) is selected from any one or a combination of at least two of rutile titanium dioxide, anatase titanium dioxide or amorphous titanium dioxide, preferably anatase titanium dioxide;

preferably, the lithium source and the titanium source are added in the step (B) in an amount satisfying a molar ratio Li to Ti of 0.75-0.85;

preferably, the rotation speed of the ball milling in the step (C) is 250 r/min-450 r/min;

preferably, the ball milling time in the step (C) is 2-8 h;

preferably, the drying temperature in the step (C) is 150-250 ℃;

preferably, the drying time in the step (C) is 2-6 h;

preferably, the sintering of step (C) is carried out under an inert atmosphere;

preferably, the conditions for the step (C) sintering are: firstly heating to a first temperature, preserving heat, then continuously heating to a second temperature of 850-1100 ℃, preserving heat;

preferably, in the sintering process, the first temperature is 650 ℃ to 850 ℃, and the heating rate for heating to the first temperature is preferably 1 ℃/min to 5 ℃/min, and more preferably 2 ℃/min;

preferably, in the sintering process, the heat preservation time at the first temperature is 8-15 h, and the heat preservation time at the second temperature is 6-10 h;

preferably, the breaking in step (C) is gas milling.

6. The method of claim 4 or 5, wherein the molar ratio of the lithium chloride to the aluminum trichloride deposited in step (1) is 0.9:1 to 1.1: 1;

preferably, in the step (1), the heating temperature of the lithium chloride is 150-180 ℃;

preferably, in the step (1), the heating temperature of the aluminum trichloride is 120-150 ℃;

preferably, in the step (1), the deposition temperature for forming the lithium aluminum tetrachloride coating layer is 150-350 ℃;

preferably, in the step (1), when lithium chloride and aluminum trichloride are alternately deposited on the surface of the lithium titanate particles by using the ALD method, argon and/or nitrogen are/is used as a carrier gas, and the carrier gas flow is preferably 10sccm to 50 sccm;

preferably, in the step (1), when lithium chloride and aluminum trichloride are alternately deposited on the surface of the lithium titanate particles by using an ALD method, the pulse time of the lithium chloride and the pulse time of the aluminum trichloride are 0.05 s-0.2 s;

preferably, in the step (1), when lithium chloride and aluminum trichloride are alternately deposited on the surface of lithium titanate particles by using the ALD method, after one substance is deposited, the other substance is cleaned and then deposited, and the cleaning time is preferably 5 s-20 s.

7. The method according to any one of claims 4 to 6, wherein the alcohol in the water-alcohol mixed solvent in the step (2) is any one or a mixture of at least two of absolute ethyl alcohol, acetone, isopropanol, ethylene glycol, glycerol or butanediol;

preferably, in the water-alcohol mixed solvent in the step (2), the volume ratio of alcohol to water is 0.5-1.

8. The method according to any one of claims 4 to 7, wherein the rotation speed of the ball milling in the step (2) is 250r/min to 450 r/min;

preferably, the ball milling time in the step (2) is 2-8 h;

preferably, in the spray drying process in the step (2), the gas pressure of the sprayer is 0.5MPa to 0.8 MPa;

preferably, in the spray drying process in the step (2), the inlet temperature of the heat source gas of the spray dryer is 200-300 ℃, and the outlet temperature is 100-150 ℃.

9. Method according to any of claims 4-8, characterized in that the method comprises the steps of:

(1) the preparation of lithium titanate particles specifically comprises the following steps:

(A) mixing an organic additive and water to prepare a mixed solvent;

(B) adding a lithium source and a titanium source into the mixed solvent obtained in the step (A) to obtain slurry;

(C) performing ball milling, drying, sintering in an inert atmosphere and crushing on the slurry obtained in the step (B) to obtain lithium titanate particles;

(2) depositing lithium chloride and aluminum trichloride on the surface of lithium titanate particles alternately by adopting an atomic layer chemical vapor deposition (ALD) method, and forming a lithium aluminum tetrachloride coating layer on the surface of the lithium titanate particles to obtain composite particles;

(3) adding the composite particles and the carbon nano tubes into a water-alcohol mixed solvent, carrying out ball milling, and carrying out spray drying to obtain a composite material of lithium aluminum tetrachloride and carbon nano tube-coated lithium titanate;

wherein, the organic additive is any one or the combination of at least two of polyethylene glycol, polyacrylamide, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, soluble starch or branched starch, and the organic additive accounts for 5 to 10 percent of the total mass of the titanium source, the lithium source and the carbon nano tube.

10. A lithium ion battery, characterized in that a negative electrode material of the lithium ion battery comprises the composite material of lithium tetrachloroaluminate and carbon nanotube-coated lithium titanate according to the first aspect.

Technical Field

The invention belongs to the field of lithium ion battery cathode materials, and relates to a composite material of lithium tetrachloroaluminate and carbon nanotube-coated lithium titanate, a preparation method of the composite material, and a lithium ion battery containing the composite material.

Background

The lithium ion battery comprises an electrode material, an electrolyte, a diaphragm, a shell and the like, and compared with other types of batteries, the lithium ion battery is considered to be an excellent power source of a power battery and an energy storage system due to the characteristics of high energy density, high working voltage, long cycle life, no memory effect, environmental friendliness and the like. The electrode material is used as a platform for charging and discharging the battery, and the performance of the electrode material is important for the lithium battery.

The carbon is mainly used as a negative electrode material of a commercial lithium ion battery, and the potential of the carbon negative electrode material is close to that of metal lithium after lithium is embedded, so that when the battery is overcharged, the metal lithium is formed on the carbon negative electrode, a diaphragm is possibly damaged, and the cycle performance and the safety of the battery are influenced.

The spinel Lithium Titanate (LTO) material has a high lithium ion diffusion coefficient, small lattice constant change and a highly stable crystal structure in the process of lithium ion intercalation and deintercalation, and is called a 'zero-strain' material. The theoretical capacity of lithium titanate is 175mAh/g, and the potential of lithium intercalation process is about 1.55V (vs Li/Li)⁺) The method has the advantages of stable platform, good thermal stability and good safety, and the application of the method in power batteries is widely concerned.

The preparation method of lithium titanate mainly comprises a solid-phase reaction method, a hydrothermal method, a sol-gel method, a chemical precipitation method and the like. The solid-phase reaction method is that solid raw materials are subjected to ball milling and mixing and then sintered at high temperature, and all components in the raw materials are subjected to solid-phase reaction at high temperature to obtain a lithium titanate product. The solid phase method has the advantages of simple process, low requirement on equipment, low cost and easy realization of large-scale industrial production; according to the hydrothermal method, raw materials are firstly reacted in a hydrothermal reaction kettle to obtain a precursor, and then the precursor is calcined at high temperature, but the requirements on the raw materials and equipment are high, and the large-scale production is not easy to realize; compared with the former two methods, the performance of the sample obtained by the sol-gel method and the chemical precipitation method is improved, but the process flow is longThe material cost is high, and the large-scale production is not easy to realize; therefore, the solid-phase reaction method is more suitable for industrial production. However, the conductivity of the lithium titanate negative electrode material is poor, so that the rate performance of the battery prepared by the lithium titanate negative electrode material is low, and meanwhile, the lithium battery taking the lithium titanate as the negative electrode has the problem of flatulence in use, namely Yanbin He, Baohua Li, Ming Liu and the like in Gassing in Li₄Ti₅O₁₂The reasons are analyzed in detail in the based batteries and its remedy, and the flatulence is mainly generated by the reaction of the lithium titanate particle surface with the electrolyte to generate H₂、CO₂And CO. Therefore, the solid-phase reaction of the lithium titanate material needs to be optimized, and the surface of the lithium titanate material is coated and modified, so that the conductivity of the lithium titanate is improved, and the problem of flatulence in the use of the battery is effectively relieved.

Disclosure of Invention

In view of the above problems in the prior art, the present invention is directed to a composite material of lithium tetrachloroaluminate and carbon nanotube-coated lithium titanate, which has high conductivity, high capacity, and high rate discharge performance, and a preparation method and use thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a composite material of lithium tetrachloroaluminate and carbon nanotube-coated lithium titanate, which comprises a composite particle composed of a lithium titanate core and a lithium tetrachloroaluminate coating layer coated on the surface of the core, and a carbon nanotube layer coated on the surface of the composite particle.

In the composite material, lithium tetrachloroaluminate is uniformly coated on the surface of lithium titanate particles, and the carbon nanotube coating layer is coated on the surface of the lithium tetrachloroaluminate.

The composite material of lithium tetrachloroaluminate and carbon nanotube-coated lithium titanate is also called lithium tetrachloroaluminate/carbon nanotube-coated lithium titanate.

The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.

Preferably, the composite particles are prepared by the following method: and (2) alternately depositing lithium chloride and aluminum trichloride on the surface of the lithium titanate particles by adopting an Atomic Layer Chemical Vapor Deposition (ALD) method, and forming a lithium aluminum tetrachloride coating Layer on the surface of the lithium titanate particles to obtain the composite particles. By adopting the method, the lithium aluminum tetrachloride coating layer is formed on the surface of the lithium titanate particles, and the lithium titanate particles are isolated from the electrolyte, so that the side reaction on the surface of the lithium titanate is effectively inhibited, the flatulence of the battery is relieved, and the cycle performance is improved.

Preferably, the chemical formula of the lithium titanate core is Li₄Ti₅O₁₂。

Preferably, the lithium titanate core has a D50 of 6 to 10 μm, such as 6, 6.5, 7, 8, 8.5, 9, or 10 μm.

Preferably, the chemical formula of the lithium aluminum tetrachloride is LiAlCl₄。

Preferably, the lithium tetrachloroaluminate coating has a thickness of 0.5nm to 5nm, such as 0.5nm, 0.8nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, or 5 nm. If the thickness is less than 0.5nm, an effective coating layer cannot be formed; if the thickness is more than 5nm, the material resistance is increased and the conductivity is reduced.

Preferably, the carbon nanotubes have a length of 5 μm to 15 μm, such as 5 μm, 6 μm, 6.5 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11.5 μm, 12 μm, 13 μm, 14 μm, 15 μm, or the like; the diameter is 10nm to 30nm, for example, 10nm, 15nm, 18nm, 20nm, 25nm, 27nm, 28nm or 30 nm.

Preferably, the mass percentage of the carbon nanotubes is 0.5% to 5%, such as 0.5%, 1%, 1.5%, 2%, 3%, 3.5%, 4%, 5%, or the like, based on 100% of the total mass of the composite material.

In a second aspect, the present invention provides a method for preparing a composite of lithium tetrachloroaluminate and carbon nanotube-coated lithium titanate as described in the first aspect, the method comprising the steps of:

(1) depositing lithium chloride and aluminum trichloride on the surface of lithium titanate particles alternately by adopting an atomic layer chemical vapor deposition (ALD) method, and forming a lithium aluminum tetrachloride coating layer on the surface of the lithium titanate particles to obtain composite particles;

(2) and adding the composite particles and the carbon nano tubes into a water-alcohol mixed solvent, performing ball milling and spray drying to obtain the composite material of lithium aluminum tetrachloride and carbon nano tube coated lithium titanate.

As a preferred technical scheme of the method, the lithium titanate particles in the step (1) are prepared by the following method:

(A) mixing an organic additive and water to prepare a mixed solvent;

(B) adding a lithium source and a titanium source into the mixed solvent obtained in the step (A) to obtain slurry;

(C) and (C) carrying out ball milling, drying, sintering and crushing on the slurry obtained in the step (B) to obtain lithium titanate particles.

By adopting the method disclosed by the preferred technical scheme to prepare the lithium titanate, the lithium titanate material with uniform particles and good appearance can be obtained, and the processing performance of the material is favorably improved.

Preferably, the organic additive in step (a) is any one or a combination of at least two of polyethylene glycol, polyacrylamide, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, soluble starch or branched starch, preferably any one or a combination of two of polyethylene glycol or polyacrylamide. By introducing the organic additive, the lithium source and the titanium source can be mixed more uniformly, so that the lithium titanate with uniform components is prepared, and the electrical property of the material is improved.

Preferably, the volume ratio of the organic additive to the water in the mixed solvent of step (a) is 0.4-1, such as 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.

Preferably, the lithium source in step (B) is selected from any one or a combination of at least two of lithium hydroxide, lithium carbonate, lithium acetate, lithium sulfate, lithium iodide or lithium phosphate, preferably any one or a combination of two of lithium hydroxide or lithium carbonate.

Preferably, the titanium source in step (B) is selected from any one of rutile titanium dioxide, anatase titanium dioxide or amorphous titanium dioxide or a combination of at least two thereof, preferably anatase titanium dioxide.

Preferably, the lithium source and the titanium source are added in step (B) in such amounts that the molar ratio Li: Ti is 0.75 to 0.85, such as 0.75, 0.78, 0.8, 0.82, or 0.85.

Preferably, the rotation speed of the ball milling in the step (C) is 250r/min to 450r/min, such as 250r/min, 300r/min, 325r/min, 350r/min, 370r/min, 385r/min, 400r/min, 415r/min, 425r/min or 450 r/min.

Preferably, the ball milling time in step (C) is 2h to 8h, such as 2h, 2.5h, 3h, 4h, 5h, 6h, 6.5h, 7h or 8 h.

Preferably, the temperature for drying in step (C) is 150-250 deg.C, such as 150 deg.C, 165 deg.C, 180 deg.C, 200 deg.C, 210 deg.C, 220 deg.C, 235 deg.C, 245 deg.C or 250 deg.C.

Preferably, the drying time in step (C) is 2h to 6h, such as 2h, 3h, 4h, 4.5h, 5h or 6 h.

Preferably, the sintering of step (C) is carried out under an inert atmosphere;

preferably, the conditions for the step (C) sintering are: the temperature is raised to the first temperature, the temperature is preserved, and then the temperature is raised to the second temperature of 850-1100 ℃, and the temperature is preserved.

In this preferred embodiment, the second temperature is 850 ℃ to 1100 ℃, for example 850 ℃, 880 ℃, 900 ℃, 925 ℃, 950 ℃, 1000 ℃, 1050 ℃, or 1100 ℃.

Preferably, the first temperature during the sintering is 650 ℃ to 850 ℃, such as 650 ℃, 680 ℃, 700 ℃, 720 ℃, 730 ℃, 750 ℃, 775 ℃, 800 ℃, 825 ℃, 850 ℃ and the like; the rate of temperature rise to the first temperature is preferably 1 ℃/min to 5 ℃/min, for example, 1 ℃/min, 1.5 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, or 5 ℃/min, and more preferably 2 ℃/min.

Preferably, the temperature is maintained at the first temperature for 8h to 15h, such as 8h, 10h, 11h, 12h, 13h, 14h or 15h, during the sintering process; the time for keeping the temperature at the second temperature is 6h to 10h, such as 6h, 7h, 7.5h, 8h, 9h or 10 h.

Preferably, the breaking in step (C) is gas milling.

In a preferred embodiment of the method of the present invention, the molar ratio of the lithium chloride and the aluminum trichloride deposited in step (1) is 0.9:1 to 1.1:1, for example, 0.9:1, 1:1 or 1.1: 1.

Preferably, in step (1), the heating temperature of lithium chloride is 150 ℃ to 180 ℃, for example 150 ℃, 155 ℃, 160 ℃, 165 ℃, 170 ℃, 175 ℃ or 180 ℃, etc.

Preferably, in step (1), the heating temperature of aluminum trichloride is 120 to 150 ℃, for example, 120 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃ or 150 ℃, etc.

The above-mentioned limitation of the heating temperature of lithium chloride and aluminum trichloride is intended to convert lithium chloride and aluminum trichloride into a gaseous state for chemical vapor deposition.

Preferably, in step (1), the deposition temperature for forming the lithium aluminum tetrachloride coating layer is 150 to 350 ℃, for example, 150 ℃, 175 ℃, 200 ℃, 215 ℃, 230 ℃, 245 ℃, 265 ℃, 280 ℃, 300 ℃, 325 ℃, or 350 ℃, etc.

Preferably, in the step (1), when lithium chloride and aluminum trichloride are alternately deposited on the surface of the lithium titanate particles by the ALD method, argon and/or nitrogen are used as a carrier gas, and the flow rate of the carrier gas is preferably 10sccm to 50sccm, for example, 10sccm, 20sccm, 30sccm, 35sccm, 40sccm, or 50 sccm.

Preferably, in the step (1), when lithium chloride and aluminum trichloride are alternately deposited on the surface of the lithium titanate particle by the ALD method, the pulse time of the lithium chloride and the aluminum trichloride is 0.05s to 0.2s, such as 0.05s, 0.08s, 0.1s, 0.12s, 0.15s, 0.17s, or 0.2 s. The pulse time refers to: the time for alternately depositing the lithium chloride and the aluminum trichloride is 0.05 s-0.2 s, and the other substance is deposited at intervals of one pulse.

Preferably, in the step (1), when lithium chloride and aluminum trichloride are alternately deposited on the surface of the lithium titanate particles by using the ALD method, after one substance is deposited, the other substance is cleaned and then deposited, and the cleaning time is preferably 5 s-20 s, such as 5s, 10s, 15s or 20 s.

In a preferred embodiment of the method of the present invention, the alcohol in the water-alcohol mixed solvent in step (2) is any one or a mixture of at least two of absolute ethyl alcohol, acetone, isopropyl alcohol, ethylene glycol, glycerol, and butylene glycol.

Preferably, in the water-alcohol mixed solvent in the step (2), the volume ratio of alcohol to water is 0.5-1, such as 0.5, 0.6, 0.8, 0.9 or 1.

Preferably, the rotation speed of the ball milling in the step (2) is 250r/min to 450r/min, such as 250r/min, 275r/min, 300r/min, 310r/min, 325r/min, 335r/min, 350r/min, 360r/min, 380r/min, 400r/min or 450 r/min.

Preferably, the ball milling time in step (2) is 2h to 8h, such as 2h, 3h, 4h, 5h, 6h, 6.5h, 7h or 8 h.

Preferably, in the spray drying process in step (2), the gas pressure of the sprayer is 0.5MPa to 0.8MPa, such as 0.5MPa, 0.6MPa, 0.7MPa or 0.8 MPa.

Preferably, in the spray drying process in the step (2), the inlet temperature of the heat source gas of the spray dryer is 200 to 300 ℃, for example, 200 ℃, 220 ℃, 230 ℃, 240 ℃, 260 ℃, 275 ℃, 280 ℃ or 300 ℃, etc.; the outlet temperature is from 100 ℃ to 150 ℃, for example 100 ℃, 110 ℃, 120 ℃, 125 ℃, 135 ℃, 140 ℃ or 150 ℃.

As a further preferred technical solution of the method of the present invention, the method comprises the steps of:

(1) the preparation of lithium titanate particles specifically comprises the following steps:

(A) mixing an organic additive and water to prepare a mixed solvent;

(B) adding a lithium source and a titanium source into the mixed solvent obtained in the step (A) to obtain slurry;

(C) performing ball milling, drying, sintering in an inert atmosphere and crushing on the slurry obtained in the step (B) to obtain lithium titanate particles;

(2) depositing lithium chloride and aluminum trichloride on the surface of lithium titanate particles alternately by adopting an atomic layer chemical vapor deposition (ALD) method, and forming a lithium aluminum tetrachloride coating layer on the surface of the lithium titanate particles to obtain composite particles;

(3) adding the composite particles and the carbon nano tubes into a water-alcohol mixed solvent, carrying out ball milling, and carrying out spray drying to obtain a composite material of lithium aluminum tetrachloride and carbon nano tube-coated lithium titanate;

wherein, the organic additive is one or the combination of at least two of polyethylene glycol, polyacrylamide, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, soluble starch or branched starch, and the organic additive accounts for 5-10% of the total mass of the titanium source, the lithium source and the carbon nano tube, such as 5%, 5.5%, 6%, 7%, 7.5%, 8%, 9% or 10%.

In a third aspect, the present invention provides a lithium ion battery, and a negative electrode material of the lithium ion battery includes the composite material of lithium tetrachloroaluminate and carbon nanotube-coated lithium titanate described in the first aspect.

Compared with the prior art, the invention has the following beneficial effects:

(1) the lithium titanate material coated with the lithium aluminum tetrachloride/the carbon nano tube prepared by the invention has a double-layer coating structure and a stable structure, the lithium aluminum tetrachloride is uniformly coated on the surface of lithium titanate particles to form composite particles, the carbon nano tube coating layer is uniformly coated outside the composite particles, and chemical bonding is formed between the composite particles coated with the lithium titanate by the lithium aluminum tetrachloride and the carbon nano tube at high temperature, so that the agglomeration of the particles can be effectively prevented; meanwhile, because the lithium aluminum tetrachloride has high lithium ion diffusion coefficient and electrochemical stability, after the coating layer is formed, the conductivity, the capacity and the rate capability of the lithium aluminum tetrachloride are obviously improved, lithium titanate particles are isolated from electrolyte in the lithium aluminum tetrachloride coating layer, and the high-efficiency transmission of lithium ions is ensured, so that the problem of gas expansion of the lithium ion battery taking lithium titanate as a negative electrode is effectively relieved, and the electrochemical performance of the lithium titanate material is greatly improved.

(2) The invention makes full use of lithium aluminum tetrachloride (LiAlCl)₄) The carbon nanotube composite material has the characteristics of stable electrochemical performance, good lithium ion conductivity, good electron conductivity of the carbon nanotube and the like under the condition of 3.0-4.5 eV, and can be compounded with lithium aluminum tetrachloride coated lithium titanate at high temperatureThe lithium aluminum tetrachloride/carbon nanotube-coated lithium titanate negative electrode material has the characteristics of high gram capacity, good rate capability and conductivity, excellent cycle performance and good lithium insertion and removal capability, and the gram capacity of discharging at the rate of 0.5C can reach 161 mAh/g.

(3) The method is simple to operate, environment-friendly and easy to realize industrial production.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments.

The lithium titanate particle size detection is carried out by adopting a MASTERSIZER2000 type laser particle size analyzer of the British Marvin company, the refractive index is 2.6, and the double-distilled water medium is subjected to wet dispersion and ultrasonic wave assisted dispersion.

The lithium titanate disclosed by the invention is subjected to constant-current charge and discharge test on a simulated battery by adopting a LAND CT2001A battery test system, and the voltage test range is 1-2.5V.