WO2019096012A1

WO2019096012A1 - Lithium titanate composite material and preparation method therefor, negative electrode plate, and lithium ion battery

Info

Publication number: WO2019096012A1
Application number: PCT/CN2018/113370
Authority: WO
Inventors: 赖信华; 赵微; 詹世英; 马美品; 李海军; 蔡惠群
Original assignee: 银隆新能源股份有限公司
Priority date: 2017-11-17
Filing date: 2018-11-01
Publication date: 2019-05-23
Also published as: CN107910528A; CN107910528B

Abstract

A lithium titanate composite material and a preparation method therefor, a negative electrode plate, and a lithium ion battery, relating to the technical field of batteries, the preparation method for the lithium titanate composite material comprising the following steps: 1) preparing a ruthenium dioxide/titanium dioxide composite; 2) using the ruthenium dioxide/titanium dioxide composite and a lithium source as raw materials, preparing a lithium titanate composite material. A lithium titanate composite material prepared using said method. A negative electrode plate comprising said lithium titanate composite material. A lithium ion battery comprising said negative electrode plate. Thus, a lithium titanate composite material having good electrical conductivity is provided; when used as the active material of a negative electrode plate of a lithium ion battery, the lithium titanate composite material can improve the rate capability of the battery.

Description

Lithium titanate composite material and preparation method thereof, negative electrode sheet and lithium ion battery

This application claims priority to Chinese Patent Application filed on November 17, 2017, the Chinese Patent Office, Application No. 201711145359.8, entitled "A Lithium Titanate Composite Material and Its Preparation Method, Anode Piece and Lithium Ion Battery" The entire content of which is incorporated herein by reference.

Technical field

The invention relates to the technical field of batteries, in particular to a lithium titanate composite material and a preparation method thereof, a negative electrode sheet and a lithium ion battery.

Background technique

With the gradual depletion of fossil fuels such as coal, oil and natural gas, today's mankind is facing an unprecedented energy crisis. While rationally utilizing and conserving non-renewable resources, it is imperative to find and develop renewable energy. However, recyclable energy storage devices such as lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and lithium-ion batteries are inevitable in the development and utilization of renewable energy sources such as solar energy, wind energy, and geothermal energy. Among many chemical energy storage batteries, lithium ion batteries have attracted attention due to their high working potential, high energy density, long cycle life, small self-discharge, wide temperature range, and no memory effect.

At present, most of the negative electrode materials of lithium ion batteries use various lithium intercalated carbon materials. However, since the potential of the carbon electrode is very close to the potential of the metal lithium, when the battery is overcharged, the surface of the carbon electrode is liable to precipitate metallic lithium, which may form dendrites and cause short circuit. When the temperature is too high, thermal runaway is easily caused. The electrode potential of the spinel Li ₄ Ti ₅ O ₁₂ relative to the metal lithium is 1.55 V, the reaction has a very flat charge and discharge platform, and the safety performance is good; and Li ₄ Ti ₅ O ₁₂ is a “zero strain” insert material. It has extremely stable structure and excellent cycle performance during charge and discharge. Although the theoretical specific capacity of Li ₄ Ti ₅ O ₁₂ is only 175 mA _· h/g, the actual specific capacity is generally maintained at 150-160 mA _· h/g because its reversible lithium ion deintercalation ratio is close to 100%. However, the conductivity of Li ₄ Ti ₅ O ₁₂ material is poor, and it is easy to generate large polarization during high-rate charge and discharge, which restricts its application in lithium ion batteries.

In view of the above shortcomings of lithium titanate (Li ₄ Ti ₅ O ₁₂ ) materials, the prior art mainly uses the following two effective methods to modify lithium titanate materials: first, ion doping modification, current research The doped ions are mainly Mg ²⁺ , Al ³⁺ , Sn ⁴⁺ , W ⁴⁺ , Ni ⁴⁺ , V ⁵⁺ and F ⁻ etc. The introduction of a small amount of metal elements can not only effectively improve the conductivity of lithium titanate materials. Sexuality can also reduce the voltage of redox reaction or cause additional voltage platform under lower potential; however, the prior art mainly uses solid phase method for ion doping; while the traditional solid phase method is simple in operation and requires equipment. It is low, but the synthesized product particles are not uniform, the crystal shape is irregular, the particle size distribution range is wide, and the synthesis cycle is long, and it is difficult to achieve efficient use of the lithium titanate material. Second, carbon coating/composite modification, which mainly uses graphene, acetylene black, multi-walled carbon nanotubes or the like as a carbon source to coat lithium titanate or compound with lithium titanate to improve titanic acid. The electronic conductivity of lithium materials; however, due to the affinity between materials and the limitations of preparation and mixing equipment, the dispersion of carbon sources such as graphene and its composite effect with lithium titanate materials are still poor, so that the preparation The battery capacity and rate performance of the electrodes are not ideal.

Summary of the invention

In view of the above, the present invention provides a lithium titanate composite material, a preparation method thereof, a negative electrode sheet and a lithium ion battery, and the main purpose thereof is to provide a lithium titanate composite material with good electrical conductivity, and the lithium titanate composite material is used. When the negative electrode active material of a lithium ion battery is used, the rate performance of the lithium ion battery can be improved.

In order to achieve the above object, the present invention mainly provides the following technical solutions:

In one aspect, an embodiment of the present invention provides a method for preparing a lithium titanate composite material, comprising the steps of:

1) preparing a ceria/titanium dioxide composite;

2) A lithium titanate composite material is prepared by using a cerium oxide/titanium dioxide composite and a lithium source as raw materials.

The object of the present invention and solving the technical problems thereof can be further achieved by the following technical measures.

Preferably, the step 2) comprises:

21) reacting the ceria/titanium dioxide composite with a lithium source to obtain a cerium-doped lithium titanate composite;

22) The erbium-doped lithium titanate composite is adsorbed to cerium ions to obtain a lithium titanate composite material.

Preferably, the step 2) comprises reacting the ceria/titanium dioxide composite with a lithium source to obtain a lithium titanate composite.

Preferably, the step 1) comprises:

11) modifying the cerium oxide with a surfactant;

12) mixing the modified cerium oxide with a solvent to prepare a dispersion;

13) Mixing the dispersion, the buffer, and the tetra-n-butyl titanate solution to prepare a mixture containing the ceria/titanium dioxide composite.

Preferably, the step 11) is specifically:

Dispersing the cerium oxide powder in the surfactant solution;

Separating the modified cerium oxide from the solution;

Wherein, the size of the cerium oxide powder is 10-15 nm.

Preferably, the surfactant solution is a polyvinylpyrrolidone solution; wherein the mass ratio of the cerium oxide to the polyvinylpyrrolidone is 1: (5-300); the mass fraction of the polyvinylpyrrolidone solution is 10-40g/L.

Preferably, in said step 12):

The solvent includes anhydrous ethanol and water; wherein the mass ratio of the modified cerium oxide, absolute ethanol, and water is (2-50): (5-20):1.

Preferably, the step 13) is specifically:

First, a buffer solution is first added to the dispersion, and then a tetra-n-butyl titanate solution is added, stirred, and uniformly mixed.

Preferably, in the step 13): the volume ratio of the buffer to the dispersion is 1: (400-800); the volume ratio of the tetra-n-butyl titanate solution to the dispersion is 1: (40-90);

Wherein, the buffer is selected from a tetramethylammonium hydroxide solution, and the volume fraction of the tetramethylammonium hydroxide solution is 5-15%; and/or the tetra-n-butyl titanate solution is selected from titanate A n-butyl ester ethanol solution, and the volume fraction of the tetra-n-butyl titanate solution is 1-20%.

Preferably, the step 21) is specifically: reacting the ceria/titanium dioxide composite with a lithium source by a sol-gel method to obtain a cerium-doped lithium titanate composite.

Preferably, when the step 1) includes the step 13), the step 21) is specifically:

Adding a lithium source to the mixture containing the cerium oxide/titanium dioxide composite, and continuously stirring for a set time to obtain a wet gel;

The wet gel is subjected to aging treatment and drying treatment to obtain a xerogel; wherein the dry gel is an antimony-doped lithium titanate composite material.

Preferably, the lithium source is selected from a lithium acetate ethanol solution; wherein the lithium acetate ethanol solution has a concentration of 0.4-1 mol/L; and the lithium acetate ethanol solution is in a solution of lithium acetate and tetra-n-butyl titanate. The molar ratio of tetra-n-butyl titanate was (0.8-0.9):1.

Preferably, the conditions for aging the wet gel are: an aging temperature of 25-50 ° C, an aging time of 3-5 hours; and/or

The conditions for drying the wet gel are: drying temperature 50-100 ° C, drying time 10-30 hours.

Preferably, the step 22) includes:

The cerium-doped lithium titanate complex is reacted with a cerium salt solution to obtain a precipitate;

After the precipitate is subjected to a calcination treatment, a lithium titanate composite material is obtained.

Preferably, the strontium salt solution is selected from a cerium nitrate solution having a concentration of 0.5-2 g/L; and the mass ratio of cerium nitrate to the cerium-doped lithium titanate complex in the cerium nitrate solution is 1: (20- 100); and/or the erbium-doped lithium titanate complex reacts with the cerium salt solution in an ultrasonic microwave mixing reaction system; and the ultrasonic microwave reaction conditions are: power 50-100 W, reaction temperature 500-1000 °C, the reaction time is 6-12 hours.

Preferably, before the step of reacting the erbium-doped lithium titanate complex with the cerium salt solution, further comprising the step of grinding the cerium-doped lithium titanate complex into a powder; and/or

The conditions for calcining the precipitate are as follows: calcination temperature is 500-1000 ° C, and calcination time is 6-12 h.

In another aspect, an embodiment of the present invention provides a lithium titanate composite material, wherein the lithium titanate composite material is prepared by the method for preparing a lithium titanate composite material according to any one of the above.

In another aspect, an embodiment of the present invention provides a negative electrode sheet, wherein the negative electrode sheet comprises the above-described carbon-silicon composite material.

In another aspect, embodiments of the present invention provide a lithium battery, wherein the lithium battery includes the negative electrode sheet described above.

Compared with the prior art, the lithium titanate composite material of the invention, the preparation method thereof, the negative electrode sheet and the lithium ion battery have at least the following beneficial effects:

In one aspect, an embodiment of the present invention provides a method for preparing a lithium titanate composite material, which mainly comprises preparing a ceria/titanium dioxide composite, and preparing the internal doping by using a ceria/titanium dioxide composite and a lithium source as raw materials. The lithium titanate composite material of the crucible; the lithium titanate composite material prepared by the method is doped with antimony, thereby improving the conductivity of the lithium titanate composite material and improving the rate performance of the battery.

Further, after the preparation method of the lithium titanate composite material provided by the embodiment of the present invention, after the internal lithium-doped lithium titanate composite is prepared, the cerium ion is further introduced outside the lithium titanate composite to further improve the lithium titanate composite material. The conductivity and improve the rate performance of the battery.

Further, in the preparation method of the lithium titanate composite material provided by the embodiment of the present invention, in the preparation of the ceria/titanium dioxide composite, the ceria is first modified with PVP, which can promote the coating of the ceria by the titanium dioxide. Moreover, when the tetra-n-butyl titanate is hydrolyzed, a buffer solution is added to make the cerium oxide/titanium dioxide composite particles uniform, and a lithium titanate composite material is prepared by a sol-gel method, and finally the lithium titanate composite material has a relatively large particle size. Uniform, can be used more efficiently.

On the other hand, an embodiment of the present invention further provides a lithium titanate composite material prepared by the above method, and the lithium titanate composite material is applied to a negative electrode sheet and a lithium ion battery, thereby finally improving the rate performance of the battery.

The above description is only an overview of the technical solutions of the present invention, and the technical means of the present invention can be more clearly understood and can be implemented in accordance with the contents of the specification. Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

DRAWINGS

1 is a flow chart showing the preparation of a method for preparing a lithium titanate composite material according to an embodiment of the present invention;

2 is an XRD chart of a lithium titanate composite material obtained in Example 1 and Example 2 of the present invention;

3 is a 1C charge and discharge curve of a lithium titanate composite material obtained in Example 1 of the present invention;

4 is a 2C charge and discharge curve of the lithium titanate composite material obtained in Example 1 of the present invention;

Figure 5 is a graph comparing the rate discharge performance of a lithium titanate composite material and a pure phase lithium titanate material prepared in an embodiment of the present invention.

Detailed ways

In order to further explain the technical means and functions of the present invention for achieving the intended purpose of the present invention, the specific embodiments, structures, features and functions according to the present application will be described in detail below with reference to the accompanying drawings and preferred embodiments. . In the following description, different "an embodiment" or "an embodiment" does not necessarily mean the same embodiment. Furthermore, the particular features, structures, or characteristics of one or more embodiments can be combined in any suitable form.

In one aspect, an embodiment of the present invention provides a method for preparing a lithium titanate composite material. As shown in FIG. 1 , the preparation method includes the following steps:

1. Preparation of a cerium oxide/titanium dioxide composite. Specifically, the steps mainly include:

11) Modifying cerium oxide with a surfactant.

The cerium oxide powder is dispersed in the surfactant solution; after sufficient reaction, the modified cerium oxide is separated from the solution. The size of the cerium oxide powder is 10-15 nm.

Preferably, the surfactant solution is a polyvinylpyrrolidone solution (PVP solution); wherein the mass ratio of cerium oxide to polyvinylpyrrolidone is 1: (5-300); the mass fraction of the polyvinylpyrrolidone solution is 10-40 g. /L.

The step is specifically as follows: the nano powder cerium oxide is dispersed in a PVP (polyvinylpyrrolidone) solution, and the reaction is sufficiently carried out; and the formed PVP-modified cerium oxide precipitate is separated.

Here, the purpose of surface modification of the cerium oxide by a surfactant in this step is to promote the coating of cerium oxide by the titanium dioxide in the step 13).

12) The modified cerium oxide is mixed with a solvent to prepare a dispersion.

In this step, the solvent includes anhydrous ethanol and water. The mass ratio of the modified cerium oxide, anhydrous ethanol and water is: (2-50): (5-20): 1.

The step is specifically: adding the PVP-modified ceria precipitate separated in the step 11) to anhydrous ethanol, adding water, and dispersing uniformly to obtain a dispersion.

The step is specifically: after the buffer is added to the dispersion, the tetra-n-butyl titanate solution is added, stirred, and uniformly mixed.

Preferably, the volume ratio of the buffer to the dispersion is 1: (400-800); the volume ratio of the tetra-n-butyl titanate solution to the dispersion is 1: (40-90);

Wherein, the buffer solution is a tetramethylammonium hydroxide solution, and the volume fraction of the tetramethylammonium hydroxide solution is 5-15%, preferably 10%. The tetra-n-butyl titanate solution is a tetra-n-butyl titanate ethanol solution, and the volume fraction of the tetra-n-butyl titanate solution is 1-20%.

In this step, the purpose of adding the buffer is as follows: since the tetra-n-butyl titanate solution is hydrolyzed after being mixed with the dispersion, and the hydrolysis is severe, the buffer is added to moderate the speed of hydrolysis to form a uniform size. Ceria/titanium dioxide composite particles.

Second, a lithium titanate composite material is prepared by using a cerium oxide/titanium dioxide composite and a lithium source as two raw materials.

This step mainly includes the following two options:

The first scheme: reacting a cerium oxide/titanium dioxide composite and a lithium source to directly prepare a lithium titanate composite material.

The solution is that the finally obtained lithium titanate composite is only doped internally.

The second option includes the following steps:

21) The cerium oxide/titanium dioxide composite is reacted with a lithium source to obtain a cerium-doped lithium titanate composite (corresponding to the final product of the first scheme).

In the second scheme, on the basis of obtaining an internal erbium-doped lithium titanate composite, cerium ions are introduced outside the cerium-doped lithium titanate material to obtain a lithium titanate composite material which is internally and externally doped with cerium.

Preferably, the step 21) is specifically: reacting the ceria/titanium dioxide composite with a lithium source by a sol-gel method to obtain a cerium-doped lithium titanate composite. Preferably, when the step 1) includes the step 13), the step 21) is specifically: adding a lithium source to the mixture containing the ceria/titanium dioxide composite, and continuously stirring for a set time to obtain a wet gel. The wet gel is subjected to aging treatment and drying treatment to obtain a dry gel; wherein the dry gel is an erbium-doped lithium titanate composite material. Preferably, the lithium source in the embodiment of the invention is preferably a lithium acetate ethanol solution (alternatively, a lithium carbonate solution or a lithium oxalate solution may also be used). Wherein the concentration of the lithium acetate ethanol solution is 0.4-1 mol/L; the molar ratio of lithium acetate in the lithium acetate ethanol solution to tetra-n-butyl titanate in the tetra-n-butyl titanate solution is (0.8-0.9) :1. Preferably, the conditions for aging the wet gel are: an aging temperature of 25-50 ° C, and an aging time of 3-5 hours. Preferably, the conditions for drying the wet gel are: drying temperature 50-100 ° C, drying time 10-30 hours. The preparation step of the first scheme can be referred to step 21).

Step 21) Specifically, after the dispersion liquid, the buffer solution, and the tetra-n-butyl titanate solution of the step 13) were uniformly mixed, a lithium acetate ethanol solution was added dropwise thereto, and the mixture was continuously stirred for 2 hours to obtain a wet gel. The wet gel is aged in an oven for a period of time, and then dried to obtain a dry gel.

Step 22) specifically includes:

221) A cerium-doped lithium titanate complex (xerogel) is reacted with a cerium salt solution to obtain a precipitate.

Preferably, the cerium salt solution is selected from a cerium nitrate solution having a concentration of 0.5-2 g/L; and the mass ratio of cerium nitrate to the cerium-doped lithium titanate complex in the cerium nitrate solution is 1: (20-100).

Preferably, the erbium-doped lithium titanate complex is reacted with the cerium salt solution in an ultrasonic microwave mixing reaction system; and the ultrasonic microwave reaction conditions are: power of 50-100 W, reaction temperature of 500-1000 ° C, reaction time It is 6-12 hours.

Preferably, prior to the step of reacting the erbium-doped lithium titanate complex with the cerium salt solution, the step of grinding the erbium-doped lithium titanate complex into a powder is further included.

222) After the precipitate is subjected to calcination treatment, a lithium titanate composite material is obtained.

Preferably, the conditions for calcining the precipitate are: in air, the calcination temperature is 500-1000 ° C, and the calcination time is 6-12 h. Since the precipitate obtained in the step 221) has water and ethanol, the step 222) calcination is mainly for removing ethanol, water, and increasing the crystallinity of the lithium titanate composite.

In another aspect, an embodiment of the present invention further provides a lithium titanate composite material, wherein the lithium titanate composite material is prepared by the above method for preparing a lithium titanate composite material.

On the other hand, an embodiment of the present invention further provides a lithium battery, wherein the lithium battery includes the above negative electrode sheet.

The following is further illustrated by the experimental examples.

Example 1

In this embodiment, a lithium titanate composite material is prepared, and the specific steps are as follows:

1) Disperse 0.02 g of nano cerium oxide powder into 100 ml of a 20 g/L PVP solution, stir the reaction for 10 h, and separate the resulting pale yellow PVP-modified cerium oxide powder, and then add 100 ml of absolute ethanol. In addition, 10 ml of deionized water was added, and after ultrasonic dispersion for 5 minutes, a dispersion was obtained.

2) 200 μl of a volume fraction of 10% TMAH solution was added dropwise to the dispersion, and then 200 ml of a volume fraction of 5% tetra-n-butyl titanate in ethanol was added thereto, stirred for 15 min, and uniformly mixed to obtain a dioxide-containing solution. A mixture of cerium/titanium dioxide composites.

3) 80 ml of a 0.4 mol/L lithium acetate ethanol solution was added dropwise to the mixture obtained in the step 2), and stirred for 2 hours to obtain a yellow colloid. The yellow gel was placed in an oven at 35 ° C for 3 h to give a white gel. The white gel was dried in an oven at 80 ° C for 20 h to obtain a dry gel. Among them, the xerogel is an antimony-doped lithium titanate composite.

4) After grinding the dry gel into powder, add it to 100 ml of 0.5 g/L lanthanum nitrate solution, place it in an ultrasonic microwave mixing reaction system at 50 W, and react at 60 ° C for 1 h to separate the precipitate and place it in a tube. The air atmosphere in the furnace was calcined at 800 ° C for 8 h to obtain a lithium titanate composite material.

1.2 g of the lithium titanate composite material prepared in Example 1 was weighed, and a certain amount of a conductive agent, a binder and N-methylpyrrolidone were added, and the ball-milled powder was ball-milled for 3 hours by a planetary ball mill. The film was coated with a 152 um thick film, and after vacuum drying, it was cut into a disk having a diameter of 12 mm. After drying, the mass of the pole piece was accurately weighed and the active material content was calculated. The lithium metal sheet is selected as the counter electrode and the reference electrode, the membrane is made of polypropylene microporous membrane, and the electrolyte is an organic mixed solution of 1 mol/L EC (ethylene carbonate) and DEC (diethyl carbonate) (VEC: VDEC= 1:1), a button-type battery is assembled in a vacuum glove box, and a button-type battery sealing machine is used for sealing to obtain a button battery.

Example 2

1) Disperse 0.01 g of nano cerium oxide powder into 100 ml of 20 g/L PVP solution, stir the reaction for 10 h, and separate the resulting pale yellow PVP modified cerium oxide powder, and then add 100 ml of absolute ethanol. In addition, 15 ml of deionized water was added, and after ultrasonic dispersion for 5 minutes, a dispersion was obtained.

2) 180 ul of a 10% volume of TMAH solution was added dropwise to the dispersion, and 120 ml of a 10% by volume solution of tetra-n-butyl titanate in ethanol was added thereto, stirred for 15 min, and uniformly mixed to obtain a dioxide-containing solution. A mixture of cerium/titanium dioxide composites.

3) 80 ml of a 0.5 mol/L lithium acetate ethanol solution was added dropwise to the mixture obtained in the step 2), and stirred for 2 hours to obtain a yellow colloid. The yellow gel was placed in an oven at 40 ° C for 3 h to give a white gel. The white gel was dried in an oven at 90 ° C for 20 h to obtain a dry gel. Among them, the xerogel is an antimony-doped lithium titanate composite.

4) After grinding the dry gel into a powder, it is added to 100 ml of 1 g/L lanthanum nitrate solution, placed in an ultrasonic microwave mixing reaction system at 50 W, and reacted at 70 ° C for 1 h, and the precipitate is separated and placed in a tube furnace. The medium air atmosphere was calcined at 800 ° C for 10 h to obtain a lithium titanate composite material.

1.2 g of the lithium titanate composite material prepared in Example 2 was weighed, a certain amount of conductive agent, binder and N-methylpyrrolidone were added, and the ball-milled powder was ball-milled on an aluminum foil by ball milling for 3 hours. The film was coated with a 152 um thick film, and after vacuum drying, it was cut into a disk having a diameter of 12 mm. After drying, the mass of the pole piece was accurately weighed and the active material content was calculated. The lithium metal sheet is selected as the counter electrode and the reference electrode, the membrane is made of polypropylene microporous membrane, and the electrolyte is an organic mixed solution of 1 mol/L EC (ethylene carbonate) and DEC (diethyl carbonate) (VEC: VDEC= 1:1), a button-type battery is assembled in a vacuum glove box, and a button-type battery sealing machine is used for sealing to obtain a button battery.

Example 3

1) Disperse 0.01 g of nano cerium oxide powder into 100 ml of 25 g/L PVP solution, stir the reaction for 10 h, and separate the resulting pale yellow PVP modified cerium oxide powder, and then add 100 ml of absolute ethanol. Then, 20 ml of deionized water was further added, and after ultrasonic dispersion for 5 minutes, a dispersion liquid was obtained.

2) 200 μl of a volume fraction of 10% TMAH solution was added dropwise to the dispersion, and 150 ml of a 5% by volume solution of tetra-n-butyl titanate in ethanol was added thereto, stirred for 15 min, and uniformly mixed to obtain a dioxide-containing solution. A mixture of cerium/titanium dioxide composites.

3) To the mixture obtained in the step 2), 50 ml of a 0.5 mol/L lithium acetate ethanol solution was added dropwise, and after stirring for 2 hours, a yellow colloid was obtained. The yellow gel was placed in an oven at 45 ° C for 3 h to give a white gel. The white gel was dried in an oven at 70 ° C for 15 h to obtain a dry gel. Among them, the xerogel is an antimony-doped lithium titanate composite.

4) After grinding the dry gel into powder, add it to 100 ml of 0.8 g/L lanthanum nitrate solution, place it in an ultrasonic microwave mixing reaction system at 50 W, and react at 60 ° C for 2 h to separate the precipitate and place it in a tube. The air atmosphere in the furnace was calcined at 900 ° C for 10 h to obtain a lithium titanate composite material.

1.2 g of the lithium titanate composite material prepared in Example 3 was weighed, and a certain amount of a conductive agent, a binder and N-methylpyrrolidone were added, and the ball-milled powder was ball-milled on an aluminum foil by ball milling for 3 hours. The film was coated with a 152 um thick film, and after vacuum drying, it was cut into a disk having a diameter of 12 mm. After drying, the mass of the pole piece was accurately weighed and the active material content was calculated. The lithium metal sheet is selected as the counter electrode and the reference electrode, the membrane is made of polypropylene microporous membrane, and the electrolyte is an organic mixed solution of 1 mol/L EC (ethylene carbonate) and DEC (diethyl carbonate) (VEC: VDEC= 1:1), a button-type battery is assembled in a vacuum glove box, and a button-type battery sealing machine is used for sealing to obtain a button battery.

Example 4

1) Disperse 0.01 g of nano cerium oxide powder into 100 ml of 30 g/L PVP solution, stir the reaction for 10 h, and separate the resulting pale yellow PVP modified cerium oxide powder, and then add 100 ml of absolute ethanol. In addition, 5 ml of deionized water was added, and after ultrasonic dispersion for 5 minutes, a dispersion was obtained.

2) 230 ul of a 10% volume of TMAH solution was added dropwise to the dispersion, and then 200 ml of a 5% volume of tetra-n-butyl titanate in ethanol was added thereto, stirred for 15 min, and uniformly mixed to obtain a dioxide-containing solution. A mixture of cerium/titanium dioxide composites.

3) To the mixture obtained in the step 2), 45 ml of a 0.7 mol/L lithium acetate ethanol solution was added dropwise, and after stirring for 2 hours, a yellow colloid was obtained. The yellow gel was placed in an oven at 40 ° C for 4 h to give a white gel. The white gel was dried in an oven at 80 ° C for 25 h to obtain a dry gel. Among them, the xerogel is an antimony-doped lithium titanate composite.

4) After grinding the dry gel into a powder, it is added to 100 ml of a 0.9 g/L lanthanum nitrate solution, placed in an ultrasonic microwave mixing reaction system at 60 W, and reacted at 80 ° C for 1 h, and the precipitate is separated and placed in a tube type. The air atmosphere in the furnace was calcined at 800 ° C for 8 h to obtain a lithium titanate composite material.

1.2 g of the lithium titanate composite material prepared in Example 4 was weighed, and a certain amount of a conductive agent, a binder and N-methylpyrrolidone were added, and the ball-milled powder was ball-milled for 3 hours by a planetary ball mill. The film was coated with a 152 um thick film, and after vacuum drying, it was cut into a disk having a diameter of 12 mm. After drying, the mass of the pole piece was accurately weighed and the active material content was calculated. The lithium metal sheet is selected as the counter electrode and the reference electrode, the membrane is made of polypropylene microporous membrane, and the electrolyte is an organic mixed solution of 1 mol/L EC (ethylene carbonate) and DEC (diethyl carbonate) (VEC: VDEC= 1:1), a button-type battery is assembled in a vacuum glove box, and a button-type battery sealing machine is used for sealing to obtain a button battery.

Example 5

1) Disperse 0.02 g of nano cerium oxide powder into 100 ml of a 30 g/L PVP solution, stir the reaction for 10 h, and separate the resulting pale yellow PVP-modified cerium oxide powder, and then add 100 ml of absolute ethanol. In addition, 15 ml of deionized water was added, and after ultrasonic dispersion for 5 minutes, a dispersion was obtained.

2) 150 ul of a 10% volume of TMAH solution was added dropwise to the dispersion, and 150 ml of a 12% volume fraction of tetra-n-butyl titanate in ethanol was added thereto, stirred for 15 min, and uniformly mixed to obtain a dioxide-containing solution. A mixture of cerium/titanium dioxide composites.

3) To the mixture obtained in the step 2), 60 ml of a 1 mol/L lithium acetate ethanol solution was added dropwise, and after stirring for 2 hours, a yellow colloid was obtained. The yellow gel was placed in an oven at 35 ° C for 5 h to give a white gel. The white gel was dried in an oven at 90 ° C for 25 h to obtain a dry gel. Among them, the xerogel is an antimony-doped lithium titanate composite.

4) After grinding the dry gel into powder, add it to 100 ml of 2 g/L lanthanum nitrate solution, place it in an ultrasonic microwave mixing reaction system at 60 W, and react at 80 ° C for 2 h. Separate the precipitate and place it in a tube furnace. The medium air atmosphere was calcined at 100 ° C for 9 h to obtain a lithium titanate composite material.

1.2 g of the lithium titanate composite material prepared in Example 5 was weighed, and a certain amount of a conductive agent, a binder and N-methylpyrrolidone were added, and the ball-milled powder was ball-milled for 3 hours by a planetary ball mill. The film was coated with a 152 um thick film, and after vacuum drying, it was cut into a disk having a diameter of 12 mm. After drying, the mass of the pole piece was accurately weighed and the active material content was calculated. The lithium metal sheet is selected as the counter electrode and the reference electrode, the membrane is made of polypropylene microporous membrane, and the electrolyte is an organic mixed solution of 1 mol/L EC (ethylene carbonate) and DEC (diethyl carbonate) (VEC: VDEC= 1:1), a button-type battery is assembled in a vacuum glove box, and a button-type battery sealing machine is used for sealing to obtain a button battery.

Comparative example

Weigh 1.2g pure phase lithium titanate composite material, add a certain amount of conductive agent, binder and N-methylpyrrolidone, ball milled for 3h by planetary ball mill, and spray the ball milled powder on aluminum foil to 152um The thick film is vacuum-dried and cut into discs with a diameter of 12 mm. After drying, the mass of the pole pieces is accurately weighed and the active material content is calculated. The lithium metal sheet is selected as the counter electrode and the reference electrode, the membrane is made of polypropylene microporous membrane, and the electrolyte is an organic mixed solution of 1 mol/L EC (ethylene carbonate) and DEC (diethyl carbonate) (VEC: VDEC= 1:1), a button-type battery is assembled in a vacuum glove box, and a button-type battery sealing machine is used for sealing to obtain a button battery.

Perform the performance test below:

The lithium titanate composite prepared in Example 1 was subjected to an X-ray diffraction test (XRD test), and the test pattern is shown in FIG.

The diffraction peak of the metal ruthenium was not observed from the XRD pattern of Fig. 2 because the amount of ruthenium in the lithium titanate composite material prepared in Example 1 was very small.

The 1C charge and discharge curve of the button battery prepared in Example 1 is shown in FIG. 3 . The 2C charge and discharge cycle curve of the button cell prepared in Example 1 is shown in FIG. The ratio of the discharge performance of the lithium titanate material prepared in Example 1 to the pure phase lithium titanate material is shown in FIG. As can be seen from FIG. 3 to FIG. 5, the lithium titanate composite material prepared in Example 2 has good conductivity and battery rate performance.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes and modifications made to the above embodiments in accordance with the technical spirit of the present invention are still in the present invention. Within the scope of the inventive solution.

Claims

A method for preparing a lithium titanate composite material, comprising the steps of:

1) preparing a ceria/titanium dioxide composite;

2) A lithium titanate composite material is prepared by using a cerium oxide/titanium dioxide composite and a lithium source as raw materials.
The method for preparing a lithium titanate composite material according to claim 1, wherein the step 2) comprises:

21) reacting the ceria/titanium dioxide composite with a lithium source to obtain a cerium-doped lithium titanate composite;

22) The erbium-doped lithium titanate composite is adsorbed to cerium ions to obtain a lithium titanate composite material.
The method for preparing a lithium titanate composite material according to claim 1, wherein the step 2) comprises:

The ceria/titanium dioxide composite is reacted with a lithium source to obtain a lithium titanate composite.
The method for preparing a lithium titanate composite material according to any one of claims 1 to 3, wherein the step 1) comprises:

11) modifying the cerium oxide with a surfactant;

12) mixing the modified cerium oxide with a solvent to prepare a dispersion;

13) Mixing the dispersion, the buffer, and the tetra-n-butyl titanate solution to prepare a mixture containing the ceria/titanium dioxide composite.
The method for preparing a lithium titanate composite material according to claim 4, wherein the step 11) is specifically:

Dispersing the cerium oxide powder in the surfactant solution;

Separating the modified cerium oxide from the solution;

Wherein, the size of the cerium oxide powder is 10-15 nm.
The method for preparing a lithium titanate composite material according to claim 5, wherein

The surfactant solution is selected from the group consisting of polyvinylpyrrolidone solution; wherein the mass ratio of the cerium oxide to the polyvinylpyrrolidone is 1: (5-300); the mass fraction of the polyvinylpyrrolidone solution is 10-40 g /L.
The method of preparing a lithium titanate composite according to claim 4, wherein in the step 12):

The solvent includes anhydrous ethanol and water; wherein the mass ratio of the modified cerium oxide, absolute ethanol, and water is (2-50): (5-20):1.
The method for preparing a lithium titanate composite material according to claim 4, wherein the step 13) is specifically:

First, a buffer solution is first added to the dispersion, and then a tetra-n-butyl titanate solution is added, stirred, and uniformly mixed.
The method for preparing a lithium titanate composite according to claim 4, wherein in the step 13), the volume ratio of the buffer to the dispersion is 1: (400-800); The volume ratio of the tetra-n-butyl titanate solution to the dispersion is 1: (40-90);

Wherein, the buffer is selected from a tetramethylammonium hydroxide solution, and the volume fraction of the tetramethylammonium hydroxide solution is 5-15%; and/or the tetra-n-butyl titanate solution is selected from titanate A n-butyl ester ethanol solution, and the volume fraction of the tetra-n-butyl titanate solution is 1-20%.
The method for preparing a lithium titanate composite material according to any one of claims 2 to 4, wherein the step 21) is specifically: using a sol-gel method to make a ceria/titanium dioxide composite and The lithium source is reacted to obtain a cerium-doped lithium titanate complex.
The method for preparing a lithium titanate composite material according to claim 10, wherein when the step 1) comprises the step 13), the step 21) is specifically:

Adding a lithium source to the mixture containing the cerium oxide/titanium dioxide composite, and continuously stirring for a set time to obtain a wet gel;

The wet gel is subjected to aging treatment and drying treatment to obtain a xerogel; wherein the dry gel is an antimony-doped lithium titanate composite.
The method for preparing a lithium titanate composite material according to claim 11, wherein the lithium source is selected from a lithium acetate ethanol solution; wherein the lithium acetate ethanol solution has a concentration of 0.4-1 mol/L; The molar ratio of lithium acetate and tetra-n-butyl titanate in the lithium-ethanol solution was (0.8-0.9):1.
The method for preparing a lithium titanate composite material according to claim 11, wherein the condition for aging the wet gel is: an aging temperature of 25 to 50 ° C, and an aging time of 3-5 hours; and / or

The conditions for drying the wet gel are: drying temperature 50-100 ° C, drying time 10-30 hours.
The method for preparing a lithium titanate composite material according to claim 2, wherein the step 22) comprises:

The cerium-doped lithium titanate complex is reacted with a cerium salt solution to obtain a precipitate;

After the precipitate is subjected to a calcination treatment, a lithium titanate composite material is obtained.
The method for preparing a lithium titanate composite material according to claim 14, wherein the cerium salt solution is selected from a cerium nitrate solution having a concentration of 0.5-2 g/L; and the cerium nitrate solution is cerium nitrate and The mass ratio of the erbium-doped lithium titanate composite is 1: (20-100); and/or

The erbium-doped lithium titanate complex reacts with the strontium salt solution in an ultrasonic microwave mixing reaction system; and the ultrasonic microwave reaction conditions are: power of 50-100 W, reaction temperature of 500-1000 ° C, reaction time of 6 -12 hours.
The method for preparing a lithium titanate composite according to claim 14, wherein before the step of reacting the erbium-doped lithium titanate complex with the cerium salt solution, the cerium-doped lithium titanate is further included a step of grinding the composite into a powder; and/or

The conditions for calcining the precipitate are as follows: calcination temperature is 500-1000 ° C, and calcination time is 6-12 h.
A lithium titanate composite material, which is prepared by the method for preparing a lithium titanate composite material according to any one of claims 1 to 16.
A negative electrode sheet comprising the carbon-silicon composite material according to claim 17.
A lithium battery comprising the negative electrode sheet of claim 18.