WO2017024774A1

WO2017024774A1 - Preparation method for high capacity, high magnification negative electrode material

Info

Publication number: WO2017024774A1
Application number: PCT/CN2016/071956
Authority: WO
Inventors: 田东
Original assignee: 田东
Priority date: 2015-08-07
Filing date: 2016-01-25
Publication date: 2017-02-16
Also published as: CN105140496A

Abstract

A preparation method for a high capacity, high magnification negative electrode material. Preparation steps are as follows: (1) preparation of a superfine tin powder colloidal solution; (2) preparation of a precursor slurry; (3) atomization, drying, granulation, and classification; and (4) heat treatment; the lithium-ion battery negative electrode material is produced after cooling. The present invention prevents the problem of low charging/discharging efficiency and aggravated capacity decay caused by agglomeration of tin nanoparticles due to increased surface energy, thus saving production costs, avoids pollution to the environment easily caused when an organic solvent is used and the potential safety risks of explosion hazard that is prone to occur during spray granulation, and compensates for the insufficiency in the electrical conductivity of amorphous carbon, thus further enhancing electrical conductivity.

Description

Method for preparing high-capacity high-magnification anode material

Technical field

The invention relates to the field of lithium ion batteries, in particular to a preparation method of a high capacity high rate anode material.

Background technique

Since Sony Corporation of Japan took the lead in developing and commercializing lithium-ion batteries in 1990, lithium-ion batteries have developed rapidly. Today, lithium-ion batteries have been widely used in various fields of civil and military applications. With the continuous advancement of technology, people have put forward more and higher requirements for the performance of batteries: the miniaturization and personalized development of electronic devices require batteries with smaller volume and higher specific energy output; aerospace energy requirements The battery has a cycle life, better low temperature charge and discharge performance and higher safety performance; electric vehicles require batteries with high capacity, low cost, high stability and safety performance.

At present, the commercial lithium ion battery anode material is made of graphite-based carbon material, has low lithium insertion/deintercalation potential, suitable reversible capacity, rich resources, and low price, and is an ideal anode material for lithium ion batteries. However, its theoretical specific capacity is only 372 mAh/g, which limits the further improvement of the specific energy of lithium-ion batteries and cannot meet the needs of the increasingly high-energy portable mobile power sources. At the same time, when graphite is used as a negative electrode material, a solid electrolyte membrane (SEI) is formed on the surface during the first charge and discharge process. The solid electrolyte membrane is formed by reacting an electrolyte, a negative electrode material, and lithium ions, and irreversibly consuming lithium ions, which is a major factor in forming an irreversible capacity. The second is that the electrolyte is easily embedded in the lithium ion intercalation process. During the process of eviction, the electrolyte is reduced, and the resulting gas product causes the graphite sheet to peel off. Especially in the electrolyte containing PC, the graphite sheet peels off and a new interface is formed, resulting in further SEI formation, irreversible capacity increase, and circulation. The stability is degraded. The amorphous carbon formed by pyrolysis of the resin-based polymer has a low degree of order and a loose structure, and lithium ions can be relatively freely embedded and extracted therein without a large influence on the structure thereof.

In addition, 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; and has a smooth discharge platform similar to graphite. However, similar to other high-capacity metals, tin has very poor cycle performance and cannot perform normal charge and discharge cycles. 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.

Although the research on tin carbon materials has made great progress, the melting point of metal tin is only 232 ° C, which inevitably causes volume expansion during high temperature heat treatment. At present, when heat treatment of tin carbon materials, the following problems are mainly faced. When the tin-carbon composite is heat treated at a higher temperature, the tin particles are more easily fused together to form a large particle, which is in circulation. During the process, the electrode material is pulverized and detached, resulting in rapid decrease of battery capacity and deterioration of cycle performance; in low-temperature heat treatment, the resistance of the tin-carbon composite material is large and the conductivity is not good.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method for preparing a high-capacity high-magnification anode material to solve the problems raised in the above background art.

The technical problem solved by the present invention is implemented by the following technical solutions:

A preparation method of a high-capacity high-magnification anode material, the preparation steps are as follows:

(1) Preparation of ultrafine tin powder colloid solution: adding large-sized tin powder to deionized water containing dispersant according to solid content of 15% to 30%, then adding grinding balls, stirring and grinding until the average particle diameter of tin powder D50 reaches 0.1~1μm, and a colloidal solution containing ultrafine tin powder is obtained;

(2) Preparation of precursor slurry: According to the ratio of water-soluble resin: tin powder: conductive carbon black: 1:0.05-0.15: 0.02-0.05, the water-soluble resin and conductive carbon black are added to the step (1). Ultrafine tin powder colloidal solution, and adding a certain amount of deionized water, adjusting the solid content to 25% to 45%, and then continuously stirring to obtain a precursor slurry;

(3) atomization, drying, granulation and classification: the precursor slurry prepared in the step (2) is subjected to atomization, drying and granulation, and then subjected to powder classification to obtain an average particle diameter of 5 to 35 μm. Powder

(4) Heat treatment: the powder obtained in the step (3) is heated to 500-700 ° C at a rate of 1 to 5 ° C / min under the protection of an inert gas, and then kept for 1 to 5 hours, naturally cooled, and cooled. That is, a lithium ion battery anode material is obtained.

Further, the large-sized tin powder has a particle diameter of 1 μm to 3 mm.

Further, in the step (1), the large-diameter tin powder: dispersant: deionized water: the mass ratio of the grinding balls is 1:0.02 to 0.05:5 to 10:2 to 5.

Further, the dispersing agent is one or more of polyvinyl alcohol, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, alcohol, and sodium carboxymethylcellulose.

Further, the grinding ball is a zirconia ball, and one or more of the ball diameters are selected from 2 mm to 40 mm; the rotation speed of the agitating ball mill used is 60-350 rpm.

Further, the water-soluble resin is a thermosetting resin, and includes a water-soluble phenol resin, a water-soluble epoxy resin, a water-soluble alkyd resin, a water-soluble polyester resin, a water-soluble acrylic resin, a water-soluble polybutadiene resin, and a water-soluble solution. One or more mixtures of cationic resins.

Further, the inlet temperature of the spray-dried hot air in the step (3) is 150 ° C to 250 ° C, and the outlet temperature is 40 ° C to 90 ° C.

Compared with the prior art, the beneficial effects of the present invention are as follows:

1. A method for preparing ultrafine tin powder having a particle diameter of 0.1 to 1 μm by using large-diameter tin powder, thereby avoiding the volume effect of tin powder due to large particle size during charge and discharge; and also avoiding nano tin due to large Surface energy, agglomeration causes a decrease in charge and discharge efficiency and accelerates capacity reduction, saving production costs;

2. The use of water-soluble resin avoids the environmental pollution caused by the use of organic solvents, and also avoids the safety hazard that is prone to explosion hazard when spray granulation;

3. The amorphous carbon formed by the water-soluble resin after high-temperature carbonization has strong anti-corrosion ability to the electrolyte. At the same time, the interlayer spacing of the amorphous carbon is large, and the lithium ion can enter and exit quickly to meet the high magnification of the lithium ion battery. The requirements of charge and discharge, secondly, the pores and voids formed by carbonization of the water-soluble resin can buffer the volume effect of the tin powder during charging and discharging, and ensure the overall stability of the material;

4. The conductive carbon black is added to form a conductive network in the material system, which compensates for the lack of conductivity of the amorphous carbon and further enhances the electrical conductivity.

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 is further explained below.

Example 1

Weigh a certain amount of 1Kg of tin powder with a particle size of 2mm, add it to 8Kg of deionized water, then add 25g of sodium carboxymethylcellulose as a dispersing agent, then add 4Kg of zirconia grinding ball (1Kg of diameter 2mm, diameter of 5mm After 2Kg, 1Kg with a diameter of 10mm, the ball milling was started. After 6h, the powder particle size D50 was 0.76μm. According to the ratio of water-soluble resin: tin powder: conductive carbon black: 1:0.1:0.03, 10Kg water was added. Epoxy resin and 30g conductive carbon black, add 25Kg deionized water, adjust the solid content to 25%, start stirring and mixing until uniform, then spray dry granulation, collect powder with average particle size between 5 ~ 35μm Then, it was heated to 650 ° C under nitrogen atmosphere, kept for 3 hours, and then cooled to room temperature to finally obtain a lithium ion battery anode material.

The performance of the negative electrode material of the lithium ion battery of Example 1 was examined and tested by the half-cell test method. The negative electrode material of the lithium ion battery prepared in Example 1 was: acetylene black: PVDF (polyvinylidene fluoride) weight ratio of 93:3:4 Add appropriate amount of NMP (N-methylpyrrolidone) to make a slurry, apply it on copper foil, and dry it at 110 ° C for 8 hours to make a negative electrode sheet; use lithium metal sheet as the counter electrode, and the electrolyte is 1 mol/L. LiPF6/EC+DEC+DMC=1:1:1, the polypropylene microporous membrane is a membrane and assembled into a battery. The charge-discharge voltage is 0-2.0V, and the charge-discharge rate is 0.2C. The battery performance can be tested. The initial discharge capacity of the electrode material is 445mAh/g, and the capacity after 100 cycles is still 392mAh/g. 88.1%.

Example 2

Weigh 1Kg of tin powder with a particle size of 5mm, add it to 10Kg of deionized water, and then add 30g of methylol fiber. After sodium sulphide grinding ball was added as a dispersing agent, 5 kg of a zirconia grinding ball (2 kg of a diameter of 2 mm, 2 kg of a diameter of 5 mm, and 1 kg of a diameter of 10 mm) was added, and the ball milling was started. After 10 hours, the powder had a particle diameter D50 of 0.54 μm. According to water-soluble resin: tin powder: conductive carbon black = 1:0.09:0.04, add 11Kg of water-soluble epoxy resin and 40g of conductive carbon black, while adding 20Kg of deionized water, adjust the solid content to 30%, start stirring and mixing until uniform Then, spray-drying granulation, collecting powder having an average particle diameter of 10 to 35 μm, heating to 700 ° C under nitrogen atmosphere, holding for 4 hours, and then cooling to room temperature, finally obtaining a lithium ion battery anode material.

The performance of the negative electrode material of the lithium ion battery of Example 2 was examined by the same detection method as in Example 1. The initial discharge capacity of the motor material was 469 mAh/g, and the capacity after 100 cycles was still 405 mAh/g. 86.3%.

The basic principles, main features, and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited by the foregoing embodiments, and that the present invention is only described in the foregoing description and the description of the present invention, without departing from the spirit and scope of the invention. Various changes and modifications are intended to be included within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and their equivalents.

Claims

A method for preparing a high-capacity high-magnification anode material, characterized in that the preparation steps are as follows:

(1) Preparation of ultrafine tin powder colloid solution: adding large-sized tin powder to deionized water containing dispersant according to solid content of 15% to 30%, then adding grinding balls, stirring and grinding until the average particle diameter of tin powder D50 reaches 0.1~1μm, and a colloidal solution containing ultrafine tin powder is obtained;

(2) Preparation of precursor slurry: According to the ratio of water-soluble resin: tin powder: conductive carbon black: 1:0.05-0.15: 0.02-0.05, the water-soluble resin and conductive carbon black are added to the step (1). Ultrafine tin powder colloidal solution, and adding a certain amount of deionized water, adjusting the solid content to 25% to 45%, and then continuously stirring to obtain a precursor slurry;

(3) atomization, drying, granulation and classification: the precursor slurry prepared in the step (2) is subjected to atomization, drying and granulation, and then subjected to powder classification to obtain an average particle diameter of 5 to 35 μm. Powder

(4) Heat treatment: the powder obtained in the step (3) is heated to 500-700 ° C at a rate of 1 to 5 ° C / min under the protection of an inert gas, and then kept for 1 to 5 hours, naturally cooled, and cooled. That is, a lithium ion battery anode material is obtained.
The method for preparing a high-capacity high-magnification anode material according to claim 1, wherein the large-diameter tin powder has a particle diameter of 1 μm to 3 mm and a large-diameter tin in the step (1). Powder: Dispersant: Deionized water: The mass ratio of the grinding balls is 1:0.02 to 0.05:5 to 10:2 to 5.
The method for preparing a high-capacity high-magnification anode material according to claim 1 or 2, wherein the dispersing agent in the step (1) is polyvinyl alcohol, sodium dodecylbenzenesulfonate, and twelve One or more of sodium alkyl sulfate, alcohol, and sodium carboxymethylcellulose.
The method for preparing a high-capacity high-magnification anode material according to claim 1, wherein the grinding ball in the step (1) is a zirconia ball, and one or more of a ball diameter of 2 mm to 40 mm is selected. Use together.
The method for preparing a high-capacity high-magnification anode material according to claim 4, wherein the stirring ball mill has a rotation speed of 60 to 350 rpm.
The method for preparing a high-capacity high-magnification anode material according to claim 1, wherein the water-soluble resin in the step (2) is a thermosetting resin, including a water-soluble phenol resin, a water-soluble epoxy resin, and a water-soluble resin. One or a mixture of one or more of an alkyd resin, a water-soluble polyester resin, a water-soluble acrylic resin, a water-soluble polybutadiene resin, and a water-soluble cationic resin.
The method for preparing a high-capacity high-magnification anode material according to claim 1, wherein the inlet temperature of the hot air during the spray drying in the step (3) is 150 ° C to 250 ° C, and the outlet temperature is 40 ° C to 90 ° °C.