WO2017024902A1

WO2017024902A1 - Preparation method for modified lithium-ion battery lithium titanate negative electrode material

Info

Publication number: WO2017024902A1
Application number: PCT/CN2016/087180
Authority: WO
Inventors: 田东
Original assignee: 田东
Priority date: 2015-08-07
Filing date: 2016-06-25
Publication date: 2017-02-16
Also published as: CN105129844A

Abstract

Disclosed is a preparation method for a modified lithium titanate negative electrode material. The preparation method for the modified lithium titanate negative electrode material, in which raw materials are proportioned according to parts by weight, comprises the following process steps: (1) preparation of lithium titanate; (2) the lithium titanate, a phenolic resin, and tin nanopowder are mixed into a uniform slurry; (3) lithium titanate powder is produced by spray drying; (4) the powder produced in step (3) is mixed evenly with an asphalt powder; and, (5) under the protection of a noble gas, the powder produced in step (4) undergoes a high temperature treatment to produce the modified lithium titanate negative electrode material. The present invention allows preparation of lithium titanate by means of a solid phase method and has the advantages of a simple process, inexpensive manufacturing costs, and a short production cycle.

Description

Preparation method of modified lithium battery lithium titanate anode material

Technical field

The invention relates to a preparation method of a lithium ion battery anode material, in particular to a preparation method of a modified lithium battery lithium titanate anode material.

Background technique

Lithium-ion batteries, which have been widely used in electronic products such as mobile phones and notebook computers, have large specific energy, high specific power, low self-discharge, good cycle characteristics, fast charging and high efficiency, wide operating temperature range, and no environmental pollution. Advantages, the lithium-ion batteries currently used in the market basically use carbon materials as the negative electrode, but the carbon material is the negative electrode in the practical application, there are some insurmountable weaknesses, for example, reacting with the electrolyte during the first discharge to form a surface. The passivation film causes the electrolyte to be consumed and the first coulombic efficiency is low; 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 cause a short circuit, thereby causing a short circuit. The battery exploded. In order to solve the safety problem of lithium batteries, a lot of research has been done. As a new type of lithium ion secondary battery anode material, spinel Li4Ti5O12 has the advantages of good cycle performance, no reaction with electrolyte, high safety performance, stable charge and discharge platform, etc., compared with other commercial materials. One of the most excellent lithium ion battery anode materials that has received much attention in recent years.

Compared with carbon negative electrode materials, lithium titanate has many advantages. Among them, the deintercalation of lithium ions in lithium titanate is reversible, and the crystal form of lithium ion in the process of inserting or extracting lithium titanate is not Changed, volume change is less than 1%, so it is called "zero strain material", which can avoid the structure damage caused by the back and forth expansion of the electrode material in the charge and discharge cycle, thereby improving the cycle performance and service life of the electrode, reducing the The number of cycles increases and the specific capacity is greatly attenuated, which has better cycle performance than the carbon negative electrode; however, since lithium titanate is an insulating material, its electrical conductivity is low, resulting in the rate performance in the application of lithium battery. The problem is poor. At the same time, the theoretical specific capacity of lithium titanate material is 175mAh/g, the actual specific capacity is more than 160mAh/g, and it has the disadvantages of low gram capacity. Therefore, it is necessary to modify lithium titanate.

Tin is one of the most promising anode materials for carbon materials because tin has a high specific gravity capacity of up to 994 mAh/g. In recent years, extensive research has been carried out on such materials and some progress has been made. However, in the process of reversible lithium storage, the volume expansion of metallic tin is remarkable, resulting in poor cycle performance and rapid decay of capacity, so it is difficult to meet the requirements of large-scale production. For this reason, by introducing a non-metallic element such as carbon, the metal tin is stabilized by alloying or compounding, and the volume expansion of tin is slowed down. Carbon can prevent direct contact between tin particles, inhibit the agglomeration and growth of tin particles, and act as a buffer layer.

Studies have shown that small-sized tin or its alloys have a great improvement in both capacity and cycle performance. When the particles of the alloy material reach the nanometer level, the volume expansion during charging and discharging is greatly reduced, and the performance is also greatly reduced. It will be improved, but the nanomaterials have a large surface energy and are prone to agglomeration, which in turn will reduce the charge and discharge efficiency and accelerate the attenuation of the capacity, thereby offsetting the advantages of the nanoparticles. Another research trend to improve the performance of tin anodes is to prepare composites or alloys of tin and other materials. Among them, tin/carbon composites prepared by combining the stability of carbon materials with the high specific capacity of tin have shown great application. prospect.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method for preparing a lithium metal titanate negative electrode material of a modified lithium battery to solve the problems raised in the above background art.

In order to achieve the above object, the present invention is implemented by the following technical solutions:

A preparation method of a lithium metal titanate negative electrode material for a modified lithium battery, the raw materials according to the proportion by weight, comprising the following process steps:

(1) The lithium salt and titanium dioxide are weighed according to the ratio of n(Li):n(Ti)=0.84 to 0.87, and the two are ball milled for 4 to 10 hours by a ball mill, and then the uniformly mixed powder is placed in the air. The temperature is raised to 700-850 ° C at a rate of 5 to 10 ° C / min, and then kept for 4 to 6 h, and then naturally cooled to room temperature to obtain a lithium titanate negative electrode material;

(2) Lithium titanate, phenolic resin, and nano tin powder are in a ratio of 100:5 to 20:5 to 10 and a solid content of 20% to 40%. First, a certain amount of nano tin powder is weighed into an alcohol solvent. And ultrasonically dispersed, and then separately added phenolic resin and lithium titanate, while adding 3% to 5% of hexamethylenetetramine as a resin curing agent, stirring constantly, mixing into a uniform slurry;

(3) then mixing the homogeneous slurry of step (2) by spray drying to obtain a lithium titanate powder having a surface coated with a mixture of nano tin and a phenolic resin;

(4) The powder obtained in the step (3) and the asphalt powder are uniformly mixed in a ratio of 100:5 to 20, and then the powder is heated at a rate of 1 to 5 ° C/min under the protection of an inert gas to 800 ~ 1000 ° C, and then keep warm for 1 ~ 5h, naturally cool, after cooling, sieve to obtain high-capacity modified lithium titanate anode material.

Further, the lithium salt described in the step (1) is one of lithium acetate, lithium sulfate, lithium oxalate, lithium carbonate, and lithium hydroxide.

Further, the titanium oxide described in the step (1) is one of anatase type titanium dioxide or a gold stone type titanium dioxide.

Further, the particle size of the nano tin powder described in the step (2) is not more than 100 nm.

Further, the inlet temperature of the spray-dried hot air in the step (3) is 150 ° C to 200 ° C, and the outlet temperature is 40 ° C to 70 ° C.

Further, the asphalt powder according to the step (4) includes one or more of a condensed polycyclic polynuclear hydrocarbon obtained by upgrading coal tar pitch, petroleum pitch, modified pitch, mesophase pitch, and pitch. The powder prepared by the mixture has a softening point of 100 to 280 ° C and an average particle diameter of 2 to 5 μm.

Beneficial effects:

(1) Preparation of lithium titanate by a solid phase method, which has the advantages of simple process, low manufacturing cost, short manufacturing cycle, and the like;

(2) By using nano tin powder, the volume effect of tin powder due to large particle size during charging and discharging is avoided, the stability of the material during charging and discharging is ensured, and composite coating with lithium titanate is carried out. The treatment solves the defects of low capacity of the single lithium titanate anode material;

(3) During the heat treatment of the resin, there are too many small molecules in the resin, which will cause excessive voids on the surface of the coated material during the overflow process. These voids can buffer the volume effect of the tin powder and ensure the material system. Stable

(4) By secondly coating the material with asphalt, the specific surface area of the material is reduced, and the first charge and discharge efficiency of the material is improved;

(5) By adding a resin curing agent, hexamethylenetetramine, in the previous step, the resin is heat-cured in the spray drying step, so it is not melted by the second heat, thereby avoiding the later addition of asphalt. A serious problem of agglomeration after high temperature sintering.

detailed description

In order to make the technical means, the creative features, the workflow, and the method of use of the present invention easy to understand and understand, the present invention will be further described below in conjunction with specific embodiments.

Example 1

According to n(Li):n(Ti)=0.84, 1000g of lithium carbonate and 2572g of titanium dioxide were weighed and placed in a ball mill for ball-milling for 8 hours. Then, the uniformly mixed powder was heated in air at a rate of 10 ° C/min. 800 ° C, and then kept at 4 h, and then naturally cooled to room temperature to obtain a lithium titanate negative electrode material; the above lithium titanate powder was weighed 2000 g, according to lithium titanate, phenolic resin, nano tin powder according to 100:10:5 , the solid content is 30%, weigh 100g of nano tin powder into 5366g of alcohol solvent, and ultrasonically disperse, then add 200g of phenolic resin and lithium titanate, respectively, while adding 3% of the resin 6g of tetraamine, continuously stirred, mixed into a uniform slurry; then spray-drying the slurry to obtain lithium titanate powder coated with a mixture of nano tin and phenolic resin, and then powder and asphalt powder according to 100: After the ratio of 5 is evenly mixed, under the protection of inert gas, the temperature is raised to 1000 ° C at a rate of 5 ° C / min, and then kept for 3 h, and the temperature is naturally lowered. After cooling, the modified lithium titanate negative electrode material is obtained by sieving.

Example 2

According to n(Li):n(Ti)=0.87, 1000g of lithium carbonate and 2484g of titanium dioxide were weighed and placed in a ball mill for ball milling for 8 hours. Then, the uniformly mixed powder was heated in air at a rate of 10 ° C/min. 800 ° C, and then kept at 4 h, and then naturally cooled to room temperature to obtain a lithium titanate negative electrode material; the above lithium titanate powder was weighed 2000 g, according to lithium titanate, phenolic resin, nano tin powder according to 100:10:5 , the solid content is 30%, weigh 100g of nano tin powder into 5366g of alcohol solvent, and ultrasonically disperse, then add 200g of phenolic resin and lithium titanate, respectively, while adding 3% of the resin 6g of tetraamine, continuously stirred, mixed into a uniform slurry; then spray-drying the slurry to obtain lithium titanate powder coated with a mixture of nano tin and phenolic resin, and then powder and asphalt powder according to 100: After the ratio of 5 is evenly mixed, under the protection of inert gas, the temperature is raised to 850 ° C at a rate of 3 ° C / min, and then kept for 4 h, and the temperature is naturally lowered. After cooling, the modified lithium titanate negative electrode material is obtained by sieving.

Example 3

According to n(Li):n(Ti)=0.87, 1000g of lithium carbonate and 2161g of titanium dioxide were weighed and placed in a ball mill for ball milling for 8 hours. Then, the uniformly mixed powder was heated in air at a rate of 10 ° C/min. 800 ° C, and then kept at 4 h, and then naturally cooled to room temperature to obtain a lithium titanate negative electrode material; the above lithium titanate powder was weighed 2000 g, according to lithium titanate, phenolic resin, nano tin powder according to 100:15:5 , the solid content is 30%, weigh 100g of nano tin powder into 5600g of alcohol solvent, and ultrasonically dispersed, then add 300g of phenolic resin and lithium titanate, respectively, while adding 3% of the resin 6g of tetraamine, continuously stirred, mixed into a uniform slurry; then spray-drying the slurry to obtain lithium titanate powder coated with a mixture of nano tin and phenolic resin, and then powder and asphalt powder according to 100: After the ratio of 5 is evenly mixed, under the protection of inert gas, the temperature is raised to 900 ° C at a rate of 5 ° C / min, and then kept for 3 h, and the temperature is naturally lowered. After cooling, the modified lithium titanate negative electrode material is obtained by sieving.

Comparative example 1

According to n(Li):n(Ti)=0.87, 1000g of lithium carbonate and 2161g of titanium dioxide were weighed and placed in a ball mill for ball milling for 8 hours. Then, the uniformly mixed powder was heated in air at a rate of 10 ° C/min. After 800 ° C, and then kept for 4 h, and then naturally cooled to room temperature, a lithium titanate negative electrode material was obtained.

Electrochemical performance test

In order to test the performance of the lithium niobate negative electrode material of the modified lithium battery prepared by the method of the present invention, the test was carried out by a half-cell test method using the negative electrode material of the above examples and comparative examples: acetylene black: PVDF (polyvinylidene fluoride) = 93 : 3:4 (weight ratio), add appropriate amount of NMP (N-methylpyrrolidone) to make a slurry, apply on copper foil, dry at 110 ° C for 8 hours to make a negative electrode sheet; use lithium metal sheet as the counter electrode The electrolyte is 1 mol/L LiPF6/EC+DEC+DMC=1:1:1, and the polypropylene microporous membrane is a separator, which is assembled into a battery. The charge-discharge voltage is 1.0-2.5V, and the charge-discharge rate is 0.5C. The battery performance can be tested. The test results are shown in Table 1.

Table 1 compares the performance of negative electrode materials in different examples and comparative examples.

The basic principles and main features of the present invention and the advantages of the present invention are shown and described above, and those skilled in the art should understand that the present invention is not limited by the above embodiments, and the descriptions in the above embodiments and descriptions are only illustrative. The present invention is not limited to the spirit and scope of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention. The scope of the claims is defined by the appended claims and their equivalents.

Claims

A preparation method of a lithium metal titanate negative electrode material for a modified lithium battery, wherein the raw material is in a proportion by weight, and the method comprises the following steps:

(1) The lithium salt and titanium dioxide are weighed according to the ratio of n(Li):n(Ti)=0.84 to 0.87, and the two are ball milled for 4 to 10 hours by a ball mill, and then the uniformly mixed powder is placed in the air. The temperature is raised to 700-850 ° C at a rate of 5 to 10 ° C / min, and then kept for 4 to 6 h, and then naturally cooled to room temperature to obtain a lithium titanate negative electrode material;

(2) Lithium titanate, phenolic resin, and nano tin powder are in a ratio of 100:5 to 20:5 to 10 and a solid content of 20% to 40%. First, a certain amount of nano tin powder is weighed into an alcohol solvent. And ultrasonically dispersed, and then separately added phenolic resin and lithium titanate, while adding 3% to 5% of hexamethylenetetramine as a resin curing agent, stirring constantly, mixing into a uniform slurry;

(3) then mixing the homogeneous slurry of step (2) by spray drying to obtain a lithium titanate powder having a surface coated with a mixture of nano tin and a phenolic resin;

(4) The powder obtained in the step (3) and the asphalt powder are uniformly mixed in a ratio of 100:5 to 20, and then the powder is heated at a rate of 1 to 5 ° C/min under the protection of an inert gas to 800 ~ 1000 ° C, and then keep warm for 1 ~ 5h, naturally cool, after cooling, sieved to obtain modified lithium titanate anode material.
The method for preparing a lithium iron titanate negative electrode material for a modified lithium battery according to claim 1, wherein the lithium salt in the step (1) is lithium acetate, lithium sulfate, lithium oxalate or lithium carbonate. One of lithium hydroxide.
The method for preparing a lithium iron titanate negative electrode material for a modified lithium battery according to claim 1, wherein the titanium dioxide in the step (1) is one of an anatase type titanium dioxide or a gold stone type titanium dioxide.
The method for preparing a lithium iron titanate negative electrode material for a modified lithium battery according to claim 1, wherein the particle size of the tin powder in the step (2) is not more than 100 nm.
The method for preparing a lithium iron titanate negative electrode material for a modified lithium battery according to claim 1, wherein the inlet temperature of the spray-dried hot air in the step (3) is 150 ° C to 200 ° C, and the outlet temperature is 40. °C ~ 70 °C.
The method for preparing a lithium iron titanate negative electrode material for a modified lithium battery according to claim 1, wherein the asphalt powder according to the step (4) comprises a coal pitch, a petroleum pitch, a modified asphalt, and a mesophase. The powder prepared from one or more of the condensed polycyclic polynuclear aromatic hydrocarbons obtained by upgrading the pitch and the pitch has a softening point of 100 to 280 ° C and an average particle diameter of 2 to 5 μm.