阅读说明：本技术 一种硅/碳复合负极材料及其制备方法 (silicon/carbon composite negative electrode material and preparation method thereof ) 是由 翁松清 蒋玉雄 陈梅蓉 杨行 于 2018-07-18 设计创作，主要内容包括：本发明涉及一种硅/碳复合负极材料及其制备方法,硅/碳复合负极材料制备包括以下步骤：将螯合剂、过渡金属盐与水混合,加热并搅拌,获得螯合物将硅材料加入螯合物中获得混合物,混合物边搅拌边加热,使水分蒸发,得到溶胶凝胶,干燥得到干凝胶,干凝胶在惰性气氛下燃烧,退火,破碎即得到所述硅/碳复合负极材料。该材料具有容量高,循环性能稳定的特点,所采用的原料成本低廉且工艺设备简单,生产工艺稳定可靠,易于工业化生产,有较好的市场前景。(The invention relates to silicon/carbon composite cathode materials and a preparation method thereof, wherein the preparation method of the silicon/carbon composite cathode materials comprises the following steps of mixing a chelating agent, a transition metal salt and water, heating and stirring to obtain a chelate, adding a silicon material into the chelate to obtain a mixture, stirring and heating the mixture to evaporate water to obtain sol gel, drying to obtain dry gel, burning the dry gel in an inert atmosphere, annealing and crushing to obtain the silicon/carbon composite cathode material.)

The preparation method of the silicon/carbon composite anode materials is characterized by comprising the following steps:

step 1: mixing a chelating agent, a transition metal salt and water, heating and stirring to obtain a chelate;

step 2: adding a silicon material into the chelate obtained in the step 1 to obtain a mixture;

and step 3: heating the mixture obtained in the step 2 while stirring to evaporate water to obtain sol-gel;

and 4, step 4: drying the sol gel prepared in the step 3 to obtain dry gel;

and 5: and (4) burning the xerogel obtained in the step (4) in an inert atmosphere, and annealing to obtain the silicon/carbon composite cathode material.

2. The method for preparing a silicon/carbon composite anode material according to claim 1, characterized in that: the molar ratio of the chelating agent to the transition metal salt in the step 1 is 1:1-4: 1;

optionally, the chelating agent is any of oxalic acid, acetic acid, citric acid, lauric acid, tartaric acid, gluconic acid, ethylenediamine tetraacetic acid, triethanolamine and ethylenediamine;

optionally, the transition metal salt is selected from any kinds of iron salt, ferrous salt, cobalt salt, manganese salt, nickel salt and copper salt;

optionally, the transition metal salt is kinds of iron nitrate, ferric sulfate, ferric chloride, ferrous nitrate, ferrous sulfate, ferrous chloride, cobalt nitrate, cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt chloride, manganese chloride, nickel nitrate, nickel sulfate, nickel chloride, copper sulfate, copper chloride, copper nitrate and copper fluoride;

optionally, the mass ratio of the silicon material in the step 2 to the chelating agent in the step 1 is 2:1-5: 1;

optionally, the silicon material in step 2 is silicon or silicon oxide.

3. The method for preparing a silicon/carbon composite anode material according to claim 1, characterized in that: the step 3 comprises the following steps: 3a) heating the mixture obtained in the step 2 while stirring, stopping heating when the water is evaporated to the residual water of 40-50 wt%, and 3b) continuously evaporating the water to the residual water of 20-35 wt% by using the residual temperature to obtain the sol-gel.

4. The method for preparing a silicon/carbon composite anode material according to claim 1, characterized in that: in the step 4, the drying temperature is 60-100 ℃, and the drying time is 12-48 h.

5. The method for preparing a silicon/carbon composite anode material according to claim 1, characterized in that: and step 5 comprises 5a) heating the tubular furnace to 200-plus-300 ℃ under an inert atmosphere, closing the inert gas, then pushing the dry gel obtained in step 4 into the tubular furnace, 5b) heating to 450-plus-550 ℃ after no bubble emerges from the tail end of the gas outlet of the tubular furnace, preserving the heat for 40-80min, self-combusting the dry gel, 5c) stopping heating, introducing the inert gas for assisting in cooling, cooling to room temperature, collecting a sample, and crushing to obtain the silicon/carbon composite cathode material.

6, kinds of silicon/carbon composite negative electrode material, which is prepared by the preparation method of the silicon/carbon composite negative electrode material of any of claims 1-5.

7. The silicon/carbon composite anode material according to claim 6, characterized in that: the average pore diameter of the silicon/carbon composite negative electrode material is 2-8 microns, and the porosity is 30-96%.

8, kinds of negative active materials, characterized in that the negative active material contains the silicon/carbon composite negative electrode material according to claim 6 or 7.

9, negative plate of Li-ion battery, comprising negative current collector and active material distributed on the current collector, wherein the active material contains the negative active material of claim 8.

10, lithium ion battery, which comprises a positive plate, a negative plate, a separation film between the positive plate and the negative plate, and electrolyte, wherein the negative plate is the lithium ion battery negative plate of claim 9.

Technical Field

The invention relates to the field of lithium ion batteries, in particular to silicon/carbon composite negative electrode materials and a preparation method thereof.

Background

Because the extraction of non-renewable resources (such as natural gas, coal and oil) is kept in energy crisis for a long time without control, and the transitional use of the non-renewable resources causes series pollution to the environment, along with the aggravation of energy shortage and environmental pollution, the development of electric automobiles is more and more rapid, and the lithium ion battery with high capacity, high power and long cycle life is also urgently important.

The graphite material has been widely used in because of the advantages of stable structure and cycle performance, high conductivity and the like, but the capacity requirement of the lithium ion battery is higher and higher with the continuous development of the society, and the theoretical specific capacity of the traditional graphite material is only 372mAh/g, which cannot meet the market requirement, so that the search for high-capacity materials to replace the traditional graphite material is favored.

Silicon-based materials have attracted the attention of researchers successfully due to their theoretical specific capacity as high as 4200mAh/g and abundant resources, and silicon is considered to be the next generation of lithium ion battery materials after traditional graphite, but in Li⁺In addition, of SEI film formed in the process of lithium intercalation of silicon can lead the silicon surface to be exposed and directly contacted with electrolyte due to the cracking and the pulverization of the silicon structure, and the SEI film is formed again, finally the SEI film is thicker and the electrolyte is continuously consumed, and the defects of the silicon material limit the large scale of the silicon material in the lithium ion battery industryAnd (4) applying the model. Therefore, researchers have attempted to overcome these drawbacks of silicon materials by means of nanocrystallization, carbon coating, silicon-carbon compounding, and silicon alloying.

Due to the fact that the silicon material is in the process of lithium removal/lithium insertion Li⁺Researchers improve the defect of silicon by compounding silicon and a carbon material to form a silicon/carbon composite material, wherein generally comprises the steps of simply coating carbon to cover a silicon surface with carbon layers, using the carbon layers as a buffer layer and a protective layer, and then fusing the silicon coated with the carbon layers and graphite to form the silicon/carbon composite material.

Chinese patent application CN107785560A discloses high-performance silicon-carbon negative electrode materials and a preparation method thereof, wherein the preparation method comprises the steps of mixing silicon nanocrystallization and graphite, coating the mixture with asphalt, and sintering the mixture to obtain the high-performance silicon-carbon composite negative electrode material.

Disclosure of Invention

The invention aims to solve the problems of low capacity and unstable electrochemical performance of the conventional silicon-carbon negative electrode material, and provides silicon/carbon composite negative electrode materials and a preparation method thereof.

The specific scheme is as follows:

A preparation method of silicon/carbon composite anode material, comprising the following steps:

step 1: mixing a chelating agent, a transition metal salt and water, heating and stirring to obtain a chelate;

step 2: adding a silicon material into the chelate obtained in the step 1 to obtain a mixture;

and step 3: heating the mixture obtained in the step 2 while stirring to evaporate water to obtain sol-gel;

and 4, step 4: drying the sol gel prepared in the step 3 to obtain dry gel;

and 5: and (4) burning the xerogel obtained in the step (4) in an inert atmosphere, and annealing to obtain the silicon/carbon composite cathode material.

, the mole ratio of the chelating agent to the transition metal salt in step 1 is 1:1-4: 1;

optionally, the chelating agent is any of oxalic acid, acetic acid, citric acid, lauric acid, tartaric acid, gluconic acid, ethylenediamine tetraacetic acid, triethanolamine and ethylenediamine;

optionally, the transition metal salt is selected from any kinds of iron salt, ferrous salt, cobalt salt, manganese salt, nickel salt and copper salt;

optionally, the transition metal salt is kinds of iron nitrate, ferric sulfate, ferric chloride, ferrous nitrate, ferrous sulfate, ferrous chloride, cobalt nitrate, cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt chloride, manganese chloride, nickel nitrate, nickel sulfate, nickel chloride, copper sulfate, copper chloride, copper nitrate and copper fluoride;

optionally, the mass ratio of the silicon material in the step 2 to the chelating agent in the step 1 is 2:1-5: 1;

optionally, the silicon material in step 2 is silicon or silicon oxide.

, step 3 includes 3a) heating the mixture obtained in step 2 while stirring, stopping heating when the water content is evaporated to the residual 40-50 wt% of water, and 3b) continuing to evaporate the water content to the residual 20-35 wt% of water by using the residual temperature to obtain the sol-gel.

And , drying at 60-100 deg.C for 12-48h in step 4.

, step 5 includes 5a) heating the tube furnace to 200-300 ℃ under inert atmosphere, closing the inert gas, then pushing the dry gel obtained in step 4 into the tube furnace, 5b) heating to 450-550 ℃ when no bubble emerges from the end of the gas outlet of the tube furnace, keeping the temperature for 40-80min, self-burning the dry gel, 5c) stopping heating, introducing inert gas for assisting cooling, cooling to room temperature, collecting a sample, and crushing to obtain the silicon/carbon composite cathode material.

The invention also protects silicon/carbon composite anode materials, which are prepared by the preparation method of the silicon/carbon composite anode material.

, the average pore diameter of the silicon/carbon composite negative electrode material is 2-8 microns, and the porosity is 30-96%.

The invention also protects negative active materials, which comprise the silicon/carbon composite negative electrode material.

The invention also protects lithium ion battery negative plates, which comprise a negative current collector and active materials distributed on the negative current collector, wherein the active materials comprise the negative active materials.

The invention also protects lithium ion batteries, which comprises a positive plate, a negative plate, an isolating membrane arranged between the positive plate and the negative plate, and electrolyte, wherein the negative plate is the negative plate of the lithium ion battery.

Has the advantages that:

the invention utilizes the method of combining complexation, mechanical mixing, low-temperature drying and burning-annealing to prepare the silicon/carbon composite cathode material, has less process equipment, simple process flow and low manufacturing cost, is beneficial to pushing , and the obtained silicon/carbon composite cathode material has higher capacity and cycle stability, the invention forms carbon solid through burning-annealing, embeds the silicon material in carbon material by using of loose porous carbon solid, coats layers of carbon material on the surface of silicon material in , and well overcomes the problems of low conductivity of silicon material and volume expansion of silicon material in the process of de-embedding⁺Therefore, the coulombic efficiency of the battery is improved, favorable conditions are created for the performance of the high-capacity lithium ion battery, the capacity of the silicon-based material is truly exerted, conditions are created for application of the silicon-based negative electrode material, and the prepared silicon-carbon composite material has broad application value in the field of the high-energy-density lithium ion battery.

According to preferred embodiments of the invention, in the process of preparing silicon/carbon composite anode materials, a method combining a sol-gel method, a self-combustion method and a mechanical mixing method is adopted, so that the raw material cost is low, the process equipment is simple, the production process is stable and reliable, the industrial production is easy, and the market prospect is good.

Drawings

In order to illustrate the technical solution of the present invention more clearly, the drawings will be briefly described, and it is obvious that the drawings in the following description relate to embodiments of the present invention only, and are not intended to limit the present invention.

FIG. 1 is an image of embodiments of the present invention providing a chelate xerogel before self-combustion annealing;

FIG. 2 is an image of a chelate xerogel provided by embodiments of the present invention after self-combustion annealing;

fig. 3 is an SEM image of a silicon/carbon composite anode material provided by examples of the present invention;

FIG. 4 is a charge-discharge curve of the silicon/carbon composite anode material provided by the invention under different cycle times;

fig. 5 is a curve of the charge-discharge cycle performance of the battery provided by the present invention.

Detailed Description

Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.

In the present invention, the related terms are defined as follows:

the silicon-based material is used as a battery negative electrode material, wherein the silicon is mainly used as an active substance to provide capacity, and the carbon is used as a dispersing matrix to limit the volume change of silicon particles and is used as a conductive network.

The chelating agent provided by the invention is a reagent which contains two or more than two coordination atoms and can generate a complex with a cyclic structure with other ions, and is preferably any kinds of oxalic acid, acetic acid, citric acid, lauric acid, tartaric acid, gluconic acid, ethylene diamine tetraacetic acid, triethanolamine and ethylenediamine.

The transition metal salt in the invention is a salt formed by series metal elements in d region of the periodic table, the transition metal can easily form a complex with the chelating agent in the invention due to the existence of the empty d orbit, and the transition metal salt in the invention is preferably a salt of iron, titanium, cobalt, manganese, copper and nickel, such as iron nitrate, iron sulfate, ferric chloride, ferrous nitrate, ferrous sulfate, ferrous chloride, cobalt nitrate, cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt chloride, manganese chloride, nickel nitrate, nickel sulfate, nickel chloride and copper fluoride, wherein kinds of the transition metal salt are arbitrary.

The silicon material in the invention is silicon or silicon oxide, and the preferable molecular formula is SiO_x(x is 0-2), and more preferably at least silicon materials among metal silicon powder, silicon oxide and silicon dioxide, wherein the silicon materials provide silicon sources, and in order to ensure the mixing effect with the chelate, solid inorganic silicon sources are preferred, and the uniform mixing can be realized through mechanical mixing.

For example, in the inert atmosphere, the tube furnace is firstly heated to 200-.

The present invention will be described in detail below by way of examples. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

The test methods used below included:

testing of the battery: charging and discharging tests are carried out by adopting a Wuhan blue battery test system under the multiplying power of 1C, the battery is tested at the constant temperature of 25 ℃, and the test voltage interval is 0.001-1.5V.

And (4) SEM test: scanning electron microscope JEOL, ZEISS EVO50, acceleration voltage 20KV, working distance 8 mm.