CN101580273A - High energy density spinel structural lithium titanate material and preparation method thereof - Google Patents

Abstract

The invention relates to a lithium titanate material with a high specific energy spinel structure and a preparation method thereof, belonging to the fields of nanometer material preparation technology and energy. Use cheap industrially produced titanium dioxide as raw material, prepare lithium titanate nanotubes/wires by sonochemical hydrothermal method and heat treatment under reducing atmosphere, or use lithium salt and titanium dioxide as raw materials, and prepare titanium by heat treatment under reducing atmosphere Lithium oxide submicron particles, or heat-treat the prepared spinel lithium titanate in a reducing atmosphere. Compared with lithium titanate materials obtained by heat treatment in air, these high specific energy lithium titanate materials obtained by heat treatment in reducing atmosphere can maintain higher capacity, better cycle stability and longer life under high current. service life. It is suitable for the development of electrode materials for lithium-ion batteries, supercapacitors or hybrid batteries, and is expected to be used in electric vehicles and other aspects.

Description

High specific energy spinel structure lithium titanate material and preparation method thereof

technical field

The invention relates to spinel structure lithium titanate with high charge and discharge rate and high specific energy, and belongs to the field of nano material preparation technology and energy.

Background technique

In recent years, spinel-type lithium titanate has been paid more and more attention as an electrode material for new energy storage batteries. This is because the lattice constant of spinel-type lithium titanate changes little before and after lithium ion insertion and extraction, which is called lithium Ion-intercalated "zero-strain materials" can theoretically have excellent cycle stability. At the same time, spinel lithium titanate has the characteristics of good anti-overcharge performance, thermal stability, good safety and large specific capacity, and is an excellent new lithium-ion battery material. Spinel-type lithium titanate can also be used as an electrode material for supercapacitors, providing it with high power density and energy density, and has broad application prospects in fields such as electric vehicles and hybrid vehicles.

Li ₄ Ti ₅ O ₁₂ is used as the negative electrode material of lithium ion batteries. Although the capacity is smaller than that of carbon negative electrode materials, it has the following advantages ^[127] : (1) The crystal structure can maintain a high degree of stability during the process of lithium ion intercalation and extraction , so that it has excellent cycle performance and stable discharge voltage; (2) has a high electrode voltage, thereby avoiding the decomposition of the electrolyte or the formation of a protective film; (3) the source of raw materials for the preparation of Li ₄ Ti ₅ O ₁₂ Relatively rich. Therefore, Li ₄ Ti ₅ O ₁₂ is an ideal lithium-ion battery anode material that can replace carbon. At present, Li ₄ Ti ₅ O ₁₂ has been widely used in all-solid-state batteries using solid electrolytes.

The initial electronic conductivity of pure spinel lithium titanate is very low, which affects the charge and discharge performance as the electrode material of lithium ion battery, especially the fast charge and discharge performance is very poor. Therefore, the material must be modified in order to achieve a practical level. The modification is mainly carried out in two aspects, one is to improve its electronic conductivity, and the other is to reduce the grain size to shorten the migration path of lithium ions.

In the present invention, low-cost industrial production of titanium dioxide is used as raw material, and lithium titanate nanotubes/wires are prepared by ultrasonic chemical hydrothermal method and heat treatment under reducing atmosphere, or lithium salt and titanium dioxide are used as raw materials, and lithium titanate nanotubes/wires are prepared under reducing atmosphere. Heat treatment is carried out to prepare lithium titanate submicron particles. Compared with lithium titanate materials obtained by heat treatment in air, these high specific energy lithium titanate materials obtained by heat treatment in reducing atmosphere can maintain higher capacity, better cycle stability and longer life under high current. service life. It is suitable for the development of electrode materials for lithium-ion batteries, supercapacitors or hybrid batteries, and is expected to be used in electric vehicles and other aspects.

Contents of the invention

The object of the present invention is to adopt cheap industrial production titanium dioxide as raw material, prepare lithium titanate nanotube/wire through sonochemical hydrothermal method and heat treatment under reducing atmosphere, or take lithium salt and titanium dioxide as raw material, in reducing atmosphere heat treatment under the environment to prepare lithium titanate submicron particles, or heat treatment the prepared spinel structure lithium titanate under reducing atmosphere. Compared with lithium titanate obtained by heat treatment in air, these high specific energy lithium titanate materials obtained by heat treatment in reducing atmosphere can maintain higher capacity, better cycle stability and longer service life under high current. life. Among them, the lithium titanate submicron particles that have been heat-treated in nitrogen can reach a discharge capacity of 107mAh/g at a high rate of 19C (that is, fully discharge within 3.2min), and the discharge capacity can reach 107mAh/g at 85C (that is, fully discharge within 42.4s). The discharge capacity can also reach 60mAh/g and 40mAh/g at the ultra-high rate of 212C (that is, discharge all the electricity within 17s). After 400 cycles at the charge-discharge rates of 6C and 16.3C, 100% capacity was still maintained, which were 135mAh/g and 109mAh/g, respectively. This shows that heat treatment of lithium titanate in a reducing atmosphere, compared with heat treatment in air, can not only improve the high-current charge-discharge performance of the electrode, but also greatly improve its cycle performance at high rates. It is developed as an electrode material for lithium-ion batteries, supercapacitors or hybrid batteries, and is expected to be applied to electric vehicles and other aspects.

The present invention realizes through following technical scheme:

The preparation method of ordinary spinel lithium titanate nanotubes/wires: mix 5g TiO ₂ with 70mL NaOH solution with a concentration of 10M, sonochemically react at a power of 0.2-0.5W/cm ² for 30 minutes, and then transfer into a volume of The hydrothermal reaction was carried out in a 100mL autoclave lined with polytetrafluoroethylene for 24-40h, and the hydrothermal temperature was 150-180°C. After the reaction, take out the reaction kettle, cool to room temperature naturally, filter after opening the lid of the kettle, wash the product of the hydrothermal method with 0.2M concentration of nitric acid under the condition of pH 3 for 30 minutes, and vacuum filter the product through After drying at 80°C, a white fluffy powder product, which is H ₂ Ti ₃ O ₇ nanotubes/wires, was obtained. Mix 1.5g H ₂ Ti ₃ O ₇ nanotubes/wires with 40mL LiOH aqueous solution, stir evenly, then transfer to a 50mL autoclave with Teflon lining for hydrothermal reaction over 24h to prepare nanotubes/wires The hydrothermal temperature is 120-180°C. After the reaction, the reaction kettle was taken out, cooled to room temperature naturally, filtered after opening the lid of the kettle, and washed several times with deionized water. After vacuum filtration, the filter cake was washed several times with absolute ethanol, and the product was vacuum-dried at 80° C. to obtain a white product. The product is heat-treated at 350-600° C. in an air atmosphere to obtain Li ₄ Ti ₅ O ₁₂ nanotubes/wires with a spinel structure.

The above common spinel lithium titanate nanotubes/wires are heat-treated at 300-600° C. in a reducing atmosphere to obtain high specific energy lithium titanate nanotubes/wires. Alternatively, in the final heat treatment step of the above process, the high specific energy lithium titanate nanotubes/wires can be obtained directly by heat treatment at 350-600° C. under a reducing atmosphere.

The preparation method of ordinary spinel lithium titanate submicron particles: dissolve a certain amount of lithium salt in 20-40ml ethanol, add 3g titanium dioxide powder (the molar ratio of lithium element to titanium element is 0.8:1-1.08:1) , stirred for 4 to 6 hours, and then dried at 100°C for 7 to 10 hours. The dried powder is taken out, ground and sieved, then heat-treated in an air atmosphere at 800°C for 3 hours, and cooled with the furnace.

The ordinary spinel lithium titanate submicron particles are heat-treated at 300-400° C. in a reducing atmosphere to obtain high specific energy spinel lithium titanate submicron particles. Alternatively, in the final heat treatment step of the above process, the high specific energy spinel lithium titanate submicron particles can be obtained directly by heat treatment at 800° C. under a reducing atmosphere.

The composition of the test battery electrode diaphragm for electrochemical testing of materials: the positive electrode diaphragm uses spinel lithium titanate nanotubes/wires or submicron particles that have been heat-treated under a reducing atmosphere as the active material, and a certain proportion of conductive agent is added Acetylene black and binder polyvinylidene fluoride (PVDF). Wherein the mass of the active material accounts for 80% in total, and the mass of the conductive agent acetylene black and the binder each accounts for 10%.

The process of assembling the test battery: add the dispersant N-methylpyrrolidone (NMP) to the dispersed active material, the conductive agent acetylene black and the binder PVDF to form a slurry, and stir the slurry for 4 hours to make it completely mixed , and can be placed in an ultrasonic generator for ultrasonication, the ultrasonic power is 0.2-0.5W/cm ² , and the time is 1 hour. Then, it is uniformly coated on the aluminum foil of the conductive current collector by the doctor blade method, dried in vacuum at 85° C. for 1.5 hours, and then punched. Encapsulation of the cells was performed in a glove box under an argon atmosphere. Electrolyte used 1mol/L LiPF ₆ EC:DMC (1:1) mixed solution, diaphragm used Celgard 2400.

Description of drawings

Fig. 1 is the SEM image of the material that has not been heat-treated under a nitrogen atmosphere in Example 1 of this method.

Fig. 2 is the SEM image of the material in Example 1 of this method.

Fig. 3 is a comparison of the specific capacity versus discharge rate variation trend curves of the test batteries of the materials in Example 1 of the method.

Fig. 4 is a comparison of the cycle performance of the test battery with the materials in Example 1 of this method.

Fig. 5 is the cycle performance of the test battery of the material in Example 1 of this method.

Fig. 6 is a TEM image of the material in Example 2 of this method.

Fig. 7 is the trend curve of specific capacity versus discharge rate of the test battery of the material in Example 2 of this method.

FIG. 8 is a SEM image of the material in Example 3 of the method.

Fig. 9 is the trend curve of the specific capacity of the test battery with the material in Example 3 of the method as a function of the discharge rate.

Detailed ways

Using cheap industrially produced titanium dioxide as raw material, lithium titanate nanotubes/wires are prepared by sonochemical hydrothermal method and heat treatment under reducing atmosphere, or lithium acetate or lithium carbonate and titanium dioxide are used as raw materials and carried out under reducing atmosphere Heat treatment to prepare lithium titanate submicron particles, or heat treatment the prepared spinel structure lithium titanate in reducing atmosphere. Compared with lithium titanate materials obtained by heat treatment in air, these high specific energy lithium titanate materials obtained by heat treatment in reducing atmosphere can maintain higher capacity, better cycle stability and longer life under high current. service life. It is suitable for the development of electrode materials for lithium-ion batteries, supercapacitors or hybrid batteries, and is expected to be used in electric vehicles and other aspects.

Example 1

Heat treatment of spinel lithium titanate submicron particles in 350°C nitrogen atmosphere to obtain high specific energy spinel structure lithium titanate submicron particles, test its performance, and compare with spinel structure titanium without nitrogen heat treatment The performance of lithium oxide submicron particles is compared:

Dissolve 3-4g of lithium acetate in 20-40ml of ethanol, add 3g of titanium dioxide powder, stir for 4-6 hours, and then dry at 100°C for 7-10 hours. The dried powder is taken out, ground and sieved, then heat-treated in an air atmosphere at 800°C for 3 hours, and cooled with the furnace. The obtained ordinary spinel lithium titanate submicron particles were heat-treated at 350° C. under a nitrogen atmosphere to obtain high specific energy spinel lithium titanate submicron particles, and their properties were tested. The SEM images of spinel lithium titanate submicron particles and products without nitrogen heat treatment are shown in Figure 1 and Figure 2 .

Take 2.4g of high specific energy spinel lithium titanate submicron particles, 0.3g of binder polyvinylidene fluoride (PVDF) and 0.3g of conductive agent acetylene black. After mixing evenly, add about 15ml of dispersant N-methylpyrrolidone (NMP), and stir for 4 hours. Then cast on the aluminum foil by doctor blade method, and dry in vacuum at 85° C. for 1.5 hours to obtain the positive electrode film.

The process of assembling the test battery: the positive electrode diaphragm is punched with a punch with a diameter of 12 mm, the negative electrode is made of a lithium sheet, and the CR2032 button test battery is assembled. Encapsulation of the cells was performed in a glove box under an argon atmosphere. Electrolyte used 1mol/L LiPF ₆ EC:DMC (1:1) mixed solution, diaphragm used Celgard 2400.

Test method for the electrochemical performance of high specific energy spinel lithium titanate submicron particles: charge and discharge the battery at 0.1C, 0.5C, 1C, 6C, 16.3C, 19C, 85C, 103C, 212C and other magnifications , and compared with ordinary spinel lithium titanate submicron particles, the trend chart of specific capacity changing with discharge rate (Figure 3) and cycle performance (Figure 4 and Figure 5) were obtained.

Example 2

Using sonochemical hydrothermal method and heat treatment at 350°C under 3% (volume) hydrogen/argon atmosphere to obtain high specific energy spinel structure lithium titanate nanotubes, and test their properties:

Mix 5g of _TiO2 with 70mL of 10M NaOH solution, sonochemically react for 30 minutes at a power of 0.2-0.5W/ ^cm2 , and then move it into a 100mL autoclave with a Teflon liner for hydrothermal The reaction was carried out for 24 hours, and the hydrothermal temperature was 150°C. After the reaction, take out the reaction kettle, cool to room temperature naturally, filter after opening the lid of the kettle, wash the product of the hydrothermal method with 0.2M concentration of nitric acid under the condition of pH 3 for 30 minutes, and vacuum filter the product through After drying at 80°C, a white fluffy powder product, which is H ₂ Ti ₃ O ₇ nanotubes, was obtained. Mix 1.5g H ₂ Ti ₃ O ₇ nanotubes with 40mL LiOH aqueous solution, stir evenly, and then transfer them into a 50mL autoclave with Teflon lining for hydrothermal reaction for more than 40h. The hydrothermal temperature for preparing nanotubes is 150°C. After the reaction, the reaction kettle was taken out, cooled to room temperature naturally, filtered after opening the lid of the kettle, and washed several times with deionized water. After vacuum filtration, the filter cake was washed several times with absolute ethanol, and the product was vacuum-dried at 80° C. to obtain a white product. The product is heat-treated at 350° C. in a 3% (volume) hydrogen/argon atmosphere to obtain Li ₄ Ti ₅ O ₁₂ nanotubes with a high specific energy spinel structure. The TEM image of the product is shown in Figure 6.

Take 2.4 g of high specific energy spinel lithium titanate nanotubes, 0.3 g of polyvinylidene fluoride (PVDF) as a binder, and 0.3 g of acetylene black as a conductive agent. After mixing evenly, add about 15ml of dispersant N-methylpyrrolidone (NMP), stir for 4 hours, and place in an ultrasonic wave generator for 1 hour of ultrasonic dispersion. Then cast on the aluminum foil by doctor blade method, and dry in vacuum at 85° C. for 1.5 hours to obtain the positive electrode film.

The process of assembling the test battery: the positive electrode diaphragm is punched with a punch with a diameter of 12 mm, the negative electrode is made of a lithium sheet, and the CR2032 button test battery is assembled. Encapsulation of the cells was performed in a glove box under an argon atmosphere. Electrolyte used 1mol/L LiPF ₆ EC:DMC (1:1) mixed solution, diaphragm used Celgard 2400.

The test method for the electrochemical performance of high specific energy spinel lithium titanate nanotubes: charge and discharge the battery at 0.1C, 0.5C, 1C, 2.3C, 6C, 13.7C, 26.7C, 40C and other magnifications , and the specific capacity varies with the discharge rate (Figure 7).

Example 3

Heat treatment in a nitrogen atmosphere at 800°C by a solid-state method to obtain submicron particles of lithium titanate with high specific energy spinel structure, and test its properties:

Dissolve 3-4g of lithium acetate in 20-40ml of ethanol, add 3g of titanium dioxide powder, stir for 4-6 hours, and then dry at 100°C for 7-10 hours. The dried powder was taken out, ground, sieved, and then heat-treated in a nitrogen atmosphere at 800°C for 3 hours, then cooled in the furnace to obtain high specific energy spinel lithium titanate submicron particles, and its properties were tested. The SEM image of the product is shown in Figure 8.

Take 2.4g of high specific energy spinel lithium titanate submicron particles, 0.3g of binder polyvinylidene fluoride (PVDF) and 0.3g of conductive agent acetylene black. After mixing evenly, add about 15ml of dispersant N-methylpyrrolidone (NMP), and stir for 4 hours. Then cast on the aluminum foil by doctor blade method, and dry in vacuum at 85° C. for 1.5 hours to obtain the positive electrode film.

The process of assembling the test battery: the positive electrode diaphragm is punched with a punch with a diameter of 12 mm, the negative electrode is made of a lithium sheet, and the CR2032 button test battery is assembled. Encapsulation of the cells was performed in a glove box under an argon atmosphere. Electrolyte used 1mol/L LiPF ₆ EC:DMC (1:1) mixed solution, diaphragm used Celgard 2400.

The test method for the electrochemical performance of high specific energy spinel lithium titanate submicron particles: charge and discharge the battery at 0.1C, 0.5C, 1C, 3C, 7C, 15C, 30C, 80C, 100C, etc. The change trend of specific capacity with discharge rate was obtained (Fig. 9).

Example 4

The spinel-structured lithium titanate submicron particles were heat-treated at 300°C under a nitrogen atmosphere to obtain high specific energy spinel-structured lithium titanate submicron particles and their properties were tested.

Dissolve 3-4g of lithium acetate in 20-40ml of ethanol, add 3g of titanium dioxide powder, stir for 4-6 hours, and then dry at 100°C for 7-10 hours. The dried powder is taken out, ground and sieved, then heat-treated in an air atmosphere at 800°C for 3 hours, and cooled with the furnace. The obtained ordinary spinel lithium titanate submicron particles were heat-treated at 300°C in a nitrogen atmosphere to obtain high specific energy spinel lithium titanate submicron particles, and their properties were tested.

Take 2.4g of high specific energy spinel lithium titanate submicron particles, 0.3g of binder polyvinylidene fluoride (PVDF) and 0.3g of conductive agent acetylene black. After mixing evenly, add about 15ml of dispersant N-methylpyrrolidone (NMP), and stir for 4 hours. Then cast on the aluminum foil by doctor blade method, and dry in vacuum at 85° C. for 1.5 hours to obtain the positive electrode film.

The process of assembling the test battery: the positive electrode diaphragm is punched with a punch with a diameter of 12 mm, the negative electrode is made of a lithium sheet, and the CR2032 button test battery is assembled. Encapsulation of the cells was performed in a glove box under an argon atmosphere. Electrolyte used 1mol/L LiPF ₆ EC:DMC (1:1) mixed solution, diaphragm used Celgard 2400.

The test method for the electrochemical performance of high specific energy spinel lithium titanate submicron particles: charge and discharge the battery at 0.1C, 0.5C, 1C, 5C, 10C, 20C, 50C, 100C, 200C, etc. The obtained specific capacities are 157mAh/g, 156mAh/g, 155mAh/g, 135mAh/g, 117mAh/g, 100mAh/g, 80mAh/g, 52mAh/g, 32mAh/g.

Example 5

The spinel-structured lithium titanate submicron particles were heat-treated at 400° C. under 3% (volume) hydrogen/argon atmosphere to obtain high specific energy spinel-structured lithium titanate submicron particles and their properties were tested.

Dissolve 3-4g of lithium acetate in 20-40ml of ethanol, add 3g of titanium dioxide powder, stir for 4-6 hours, and then dry at 100°C for 7-10 hours. The dried powder is taken out, ground and sieved, then heat-treated in an air atmosphere at 800°C for 3 hours, and cooled with the furnace. The obtained ordinary spinel lithium titanate submicron particles were heat-treated at 400° C. under 3% (volume) hydrogen/argon atmosphere to obtain high specific energy spinel lithium titanate submicron particles, and their properties were tested.

Take 2.4g of high specific energy spinel lithium titanate submicron particles, 0.3g of binder polyvinylidene fluoride (PVDF) and 0.3g of conductive agent acetylene black. After mixing evenly, add about 15ml of dispersant N-methylpyrrolidone (NMP), and stir for 4 hours. Then cast on the aluminum foil by doctor blade method, and dry in vacuum at 85° C. for 1.5 hours to obtain the positive electrode film.

The process of assembling the test battery: the positive electrode diaphragm is punched with a punch with a diameter of 12 mm, the negative electrode is made of a lithium sheet, and the CR2032 button test battery is assembled. Encapsulation of the cells was performed in a glove box under an argon atmosphere. Electrolyte used 1mol/L LiPF ₆ EC:DMC (1:1) mixed solution, diaphragm used Celgard 2400.

The test method for the electrochemical performance of high specific energy spinel lithium titanate submicron particles: charge and discharge the battery at 0.1C, 0.5C, 1C, 5C, 10C, 20C, 50C, 100C, 200C, etc. The obtained specific capacities are 157mAh/g, 154mAh/g, 154mAh/g, 133mAh/g, 115mAh/g, 102mAh/g, 81mAh/g, 52mAh/g, 33mAh/g.

Example 6

The spinel-structured lithium titanate submicron particles were heat-treated at 450°C under a nitrogen atmosphere to obtain high specific energy spinel-structured lithium titanate submicron particles and their properties were tested.

Dissolve 3-4g of lithium acetate in 20-40ml of ethanol, add 3g of titanium dioxide powder, stir for 4-6 hours, and then dry at 100°C for 7-10 hours. The dried powder is taken out, ground and sieved, then heat-treated in an air atmosphere at 800°C for 3 hours, and cooled with the furnace. The obtained ordinary spinel lithium titanate submicron particles were heat-treated at 450° C. in a nitrogen atmosphere to obtain high specific energy spinel lithium titanate submicron particles, and their properties were tested.

Take 2.4g of high specific energy spinel lithium titanate submicron particles, 0.3g of binder polyvinylidene fluoride (PVDF) and 0.3g of conductive agent acetylene black. After mixing evenly, add about 15ml of dispersant N-methylpyrrolidone (NMP), and stir for 4 hours. Then cast on the aluminum foil by doctor blade method, and dry in vacuum at 85° C. for 1.5 hours to obtain the positive electrode film.

The process of assembling the test battery: the positive electrode diaphragm is punched with a punch with a diameter of 12 mm, the negative electrode is made of a lithium sheet, and the CR2032 button test battery is assembled. Encapsulation of the cells was performed in a glove box under an argon atmosphere. Electrolyte used 1mol/L LiPF ₆ EC:DMC (1:1) mixed solution, diaphragm used Celgard 2400.

The test method for the electrochemical performance of high specific energy spinel lithium titanate submicron particles: charge and discharge the battery at 0.1C, 0.5C, 1C, 5C, 10C, 20C, 50C, 100C, 200C, etc. The obtained specific capacities are 156mAh/g, 156mAh/g, 155mAh/g, 132mAh/g, 116mAh/g, 101mAh/g, 81mAh/g, 51mAh/g, 34mAh/g.

Example 7

High specific energy spinel structure lithium titanate nanotubes were obtained by sonochemical hydrothermal method and heat treatment under 3% (volume) hydrogen/argon atmosphere at 400°C, and their properties were tested:

Mix 5g of _TiO2 with 70mL of 10M NaOH solution, sonochemically react for 30 minutes at a power of 0.2-0.5W/ ^cm2 , and then move it into a 100mL autoclave with a Teflon liner for hydrothermal The reaction was carried out for 24 hours, and the hydrothermal temperature was 150°C. After the reaction, take out the reaction kettle, cool to room temperature naturally, filter after opening the lid of the kettle, wash the product of the hydrothermal method with 0.2M concentration of nitric acid under the condition of pH 3 for 30 minutes, and vacuum filter the product through After drying at 80°C, a white fluffy powder product, which is H ₂ Ti ₃ O ₇ nanotubes, was obtained. Mix 1.5g H ₂ Ti ₃ O ₇ nanotubes with 40mL LiOH aqueous solution, stir evenly, and then transfer them into a 50mL autoclave with Teflon lining for hydrothermal reaction for more than 40h. The hydrothermal temperature for preparing nanotubes is 150°C. After the reaction, the reaction kettle was taken out, cooled to room temperature naturally, filtered after opening the lid of the kettle, and washed several times with deionized water. After vacuum filtration, the filter cake was washed several times with absolute ethanol, and the product was vacuum-dried at 80° C. to obtain a white product. The product is heat-treated at 400° C. in a 3% (volume) hydrogen/argon atmosphere to obtain Li ₄ Ti ₅ O ₁₂ nanotubes with a high specific energy spinel structure. The TEM image of the product is shown in Figure 6.

Take 2.4 g of high specific energy spinel lithium titanate nanotubes, 0.3 g of polyvinylidene fluoride (PVDF) as a binder, and 0.3 g of acetylene black as a conductive agent. After mixing evenly, add about 15ml of dispersant N-methylpyrrolidone (NMP), stir for 4 hours, and place in an ultrasonic wave generator for 1 hour of ultrasonic dispersion. Then cast on the aluminum foil by doctor blade method, and dry in vacuum at 85° C. for 1.5 hours to obtain the positive electrode film.

The process of assembling the test battery: the positive electrode diaphragm is punched with a punch with a diameter of 12 mm, the negative electrode is made of a lithium sheet, and the CR2032 button test battery is assembled. Encapsulation of the cells was performed in a glove box under an argon atmosphere. Electrolyte used 1mol/L LiPF ₆ EC:DMC (1:1) mixed solution, diaphragm used Celgard 2400.

The test method for the electrochemical performance of high specific energy spinel lithium titanate nanotubes: the battery is charged and discharged at 0.1C, 0.5C, 1C, 2C, 5C, 10C, 30C, 50C and other magnifications, and its The specific capacities are 165mAh/g, 154mAh/g, 151mAh/g, 148mAh/g, 145mAh/g, 138mAh/g, 128mAh/g, 124mAh/g.

Example 8

High specific energy spinel structure lithium titanate nanotubes were obtained by sonochemical hydrothermal method and heat treatment under nitrogen atmosphere at 450°C, and their properties were tested:

Mix 5g of _TiO2 with 70mL of 10M NaOH solution, sonochemically react for 30 minutes at a power of 0.2-0.5W/ ^cm2 , and then move it into a 100mL autoclave with a Teflon liner for hydrothermal The reaction was carried out for 24 hours, and the hydrothermal temperature was 150°C. After the reaction, take out the reaction kettle, cool to room temperature naturally, filter after opening the lid of the kettle, wash the product of the hydrothermal method with 0.2M concentration of nitric acid under the condition of pH 3 for 30 minutes, and vacuum filter the product through After drying at 80°C, a white fluffy powder product, which is H ₂ Ti ₃ O ₇ nanotubes, was obtained. Mix 1.5g H ₂ Ti ₃ O ₇ nanotubes with 40mL LiOH aqueous solution, stir evenly, and then transfer them into a 50mL autoclave with Teflon lining for hydrothermal reaction for more than 40h. The hydrothermal temperature for preparing nanotubes is 150°C. After the reaction, the reaction kettle was taken out, cooled to room temperature naturally, filtered after opening the lid of the kettle, and washed several times with deionized water. After vacuum filtration, the filter cake was washed several times with absolute ethanol, and the product was vacuum-dried at 80° C. to obtain a white product. The product was heat-treated at 450°C in a nitrogen atmosphere to obtain Li ₄ Ti ₅ O ₁₂ nanotubes with a high specific energy spinel structure. The TEM image of the product is shown in Figure 6.

Take 2.4 g of high specific energy spinel lithium titanate nanotubes, 0.3 g of polyvinylidene fluoride (PVDF) as a binder, and 0.3 g of acetylene black as a conductive agent. After mixing evenly, add about 15ml of dispersant N-methylpyrrolidone (NMP), stir for 4 hours, and place in an ultrasonic wave generator for 1 hour of ultrasonic dispersion. Then cast on the aluminum foil by doctor blade method, and dry in vacuum at 85° C. for 1.5 hours to obtain the positive electrode film.

The process of assembling the test battery: the positive electrode diaphragm is punched with a punch with a diameter of 12 mm, the negative electrode is made of a lithium sheet, and the CR2032 button test battery is assembled. Encapsulation of the cells was performed in a glove box under an argon atmosphere. Electrolyte used 1mol/L LiPF ₆ EC:DMC (1:1) mixed solution, diaphragm used Celgard 2400.

The test method for the electrochemical performance of high specific energy spinel lithium titanate nanotubes: the battery is charged and discharged at 0.1C, 0.5C, 1C, 2C, 5C, 10C, 30C, 50C and other magnifications, and its The specific capacities are 161mAh/g, 152mAh/g, 151mAh/g, 145mAh/g, 142mAh/g, 135mAh/g, 124mAh/g, 120mAh/g.

Claims (7)

1. High specific energy spinel structure lithium titanate material, characterized in that the material is a high specific energy spinel structure lithium titanate nanotube or wire prepared by heat treatment under a reducing atmosphere . 2. The method for preparing the high specific energy spinel structure lithium titanate material as claimed in claim 1, the method comprising the following steps: (1) Mix _TiO2 with NaOH solution, perform ultrasonic chemical reaction, and then perform hydrothermal reaction, the hydrothermal temperature is 150-180°C: (2) After the reaction, the product of the hydrothermal method is washed with dilute acid, vacuum filtered, and the product is dried to obtain a white fluffy powder product, which is H ₂ Ti ₃ O ₇ nanotubes or wires; (3) Mixing H ₂ Ti ₃ O ₇ nanotubes or wires with LiOH aqueous solution for hydrothermal reaction to prepare nanotubes or wires at a hydrothermal temperature of 120-180°C; (4) After the reaction, the product was washed with deionized water, and after vacuum filtration, the filter cake was washed with absolute ethanol, and the product was vacuum-dried to obtain a white product; It is characterized in that, (5) After the above-mentioned white product is heat-treated at 350-600° C. in a reducing atmosphere, Li ₄ Ti ₅ O ₁₂ nanotubes or wires with a spinel structure are obtained. 3. The high specific energy spinel structure lithium titanate material, characterized in that the material is a high specific energy spinel structure lithium titanate submicron particle prepared by a solid phase method and heat treatment in a reducing atmosphere. 4. The method for preparing the high specific energy spinel structure lithium titanate submicron particles as claimed in claim 4, the method comprises the following steps: (1) Lithium salt is dissolved in 20～40ml ethanol, and titanium dioxide powder is added, and the molar ratio of described lithium element and titanium element is 0.8:1～1.08:1; (2) stirring and drying; (3) The dried powder is taken out, ground and sieved, then heat-treated in a reducing atmosphere at 800°C for 3 hours, and cooled in the furnace. 5. The preparation method according to claim 5, characterized in that, the method is to heat-treat common spinel lithium titanate submicron particles at 300-400°C in a reducing atmosphere to obtain high specific energy spinel titanate Lithium submicron particles. 6. The preparation method according to claim 4, wherein the lithium salt is an organic lithium salt or an inorganic lithium salt, including lithium hydroxide, lithium oxide, lithium carbonate, lithium nitrate, lithium sulfate, lithium phosphate, chlorine Lithium chloride, lithium chlorate or lithium acetate, lithium oxalate, lithium benzoate, lithium acrylate. 7. The preparation method according to claim 2, 3, 4 or 5, characterized in that the reducing atmosphere in which the material is heat-treated includes nitrogen, hydrogen, or argon, or a mixture thereof.

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