阅读说明：本技术 基于硅基氧化物制备的硅基Si-C负极材料及其制法和应用 (Silicon-based Si-C cathode material prepared based on silicon-based oxide and preparation method and application thereof ) 是由 谢宏伟 徐亚男 王锦霞 尹华意 宋秋实 宁志强 于 2019-09-27 设计创作，主要内容包括：一种基于硅基氧化物制备的硅基Si-C负极材料及其制法和应用,属于电池负极材料制备领域。该基于硅基氧化物制备的硅基Si-C负极材料是以硅基氧化物和碳化钙为原料,在氯化钙基熔盐中进行反应制备硅基Si-C负极材料,并将该负极材料制备锂离子电池的负极,其制备的锂离子电池具有良好的比容量和循环性能。通过调控盐组成及比例、合成温度、合成时间、搅拌速率和搅拌时间,调控硅基氧化物与碳化钙反应和产物基于硅基氧化物制备的硅基Si-C负极材料的生成过程。控制反应速率,促进Si-C产物中硅和碳均匀分布和颗粒尺寸控制,有利于有效缓冲作为锂离子电池负极材料硅锂合金化过程的体积膨胀,提高硅材料的电导率,提高电化学性能。(A silicon-based Si-C cathode material prepared based on silicon-based oxide and a preparation method and application thereof belong to the field of preparation of battery cathode materials. The silicon-based Si-C negative electrode material prepared based on the silicon-based oxide is prepared by taking the silicon-based oxide and calcium carbide as raw materials, reacting in calcium chloride-based molten salt to prepare the silicon-based Si-C negative electrode material, and preparing the negative electrode material into the negative electrode of the lithium ion battery, wherein the prepared lithium ion battery has good specific capacity and cycle performance. The reaction of the silicon-based oxide and calcium carbide and the generation process of the silicon-based Si-C negative electrode material prepared by the product based on the silicon-based oxide are regulated and controlled by regulating and controlling the salt composition and proportion, the synthesis temperature, the synthesis time, the stirring rate and the stirring time. The reaction rate is controlled, the uniform distribution of silicon and carbon in the Si-C product and the control of the particle size are promoted, the volume expansion of the silicon-lithium alloying process serving as the lithium ion battery cathode material is effectively buffered, the conductivity of the silicon material is improved, and the electrochemical performance is improved.)

1. A preparation method of a silicon-based Si-C anode material prepared based on a silicon-based oxide is characterized by comprising the following steps:

step 1: preparation of

(1) Drying the calcium chloride-based molten salt raw material to obtain a calcium chloride-based molten salt raw material with water removed;

(2) under the protection of inert gas, weighing silicon-based oxide, calcium carbide and calcium chloride-based molten salt raw materials according to a ratio, grinding and uniformly mixing to obtain a mixed material, and sealing;

wherein, the silicon-based oxide is one or more of calcium silicate, silicon dioxide or Si-C-O compound;

in terms of mole ratio, the silicon-based compound: calcium carbide 1: (2-2.5); according to the mol ratio, calcium chloride in the raw materials of the calcium chloride-based molten salt is as follows: calcium carbide is more than or equal to 5: 1;

(3) placing the mixed material in an embedded crucible of a reactor, and sealing the reactor;

(4) introducing inert gas into the reactor, maintaining the inert atmosphere of the reactor and ensuring the reactor to be in positive pressure; heating the reactor while introducing inert gas;

step 2: synthesis of

After the temperature of the reactor is raised to the synthesis temperature, keeping the temperature for 1-5 hours to obtain a reaction mixture; the synthesis temperature is 600-800 ℃;

and step 3: post-treatment

And taking out the reaction mixture, cooling, grinding, pickling to remove salt, filtering, washing with water, and drying to obtain the silicon-based Si-C negative electrode material prepared based on the silicon-based oxide.

2. The method for preparing the silicon-based Si-C anode material based on the silicon-based oxide, according to claim 1, wherein in the step 1(1), the calcium chloride-based molten salt is prepared from the following raw materials: calcium chloride, or a mixed salt of calcium chloride and chloride; the chloride is one or more of sodium chloride, potassium chloride and magnesium chloride.

3. The method for preparing the silicon-based Si-C anode material prepared from the silicon-based oxide according to claim 1, wherein in the step 2, the temperature of the reactor is raised by a resistance wire furnace, and the heating rate of the reactor when the reactor is raised to the synthesis temperature is 3-10 ℃/min.

4. The method for preparing the silicon-based Si-C anode material based on the silicon-based oxide, according to claim 1, wherein the synthesis temperature in the step 2 is higher than the melting temperature of the raw material of the calcium chloride-based molten salt + (10-20) DEG C.

5. The method for preparing the silicon-based Si-C anode material prepared based on the silicon-based oxide according to claim 1, wherein in the step 2, when the temperature of the reactor is raised to the synthesis temperature and the temperature is kept constant until the molten salt is melted into a liquid state, the stirring paddle is inserted into the molten salt, and stirring is maintained during the constant-temperature reaction, wherein the rotating speed v of the stirring paddle is 0< v ≤ 700 r/min.

6. The method for preparing the silicon-based Si-C anode material prepared based on the silicon-based oxide according to claim 1, wherein in the step 3, the salt is removed by acid washing, and the acid is 0.1-0.2 mol/L hydrochloric acid; the drying is vacuum drying, and the drying temperature is 50-80 ℃.

7. A silicon-based Si-C anode material prepared based on a silicon-based oxide is characterized by being prepared by the preparation method of any one of claims 1 to 6; the particle size of the prepared silicon-based Si-C negative electrode material is 50nm-50 mu m.

8. An anode material, characterized by comprising the silicon-based Si-C anode material prepared based on the silicon-based oxide according to claim 7; the negative electrode material further comprises a conductive agent, a binder and a solvent.

9. An electrode sheet, characterized by comprising the negative electrode material according to claim 8.

10. A lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, and is characterized in that the negative electrode adopts the electrode slice of claim 9;

the particle diameter of the statically prepared silicon-based Si-C negative electrode material is 1-50 mu m, and the prepared lithium ionThe battery has a first charge-discharge coulombic efficiency of 77-81%, a first discharge capacity of 2730-3100 mAh/g, in 0.2 A.g^-1The specific capacity of 1180-1400 mAh/g is realized after the current density is circulated for 400 circles; when the particle size of the silicon-based Si-C negative electrode material prepared by stirring and dynamic preparation is 50nm-500nm, the first charge-discharge-coulombic efficiency of the prepared lithium ion battery is 75% -81%, the first discharge capacity is 2670-3000 mAh/g, and the first discharge capacity is 0.2 A.g^-1The specific capacity of the current density circulation is 500 circles, and the specific capacity is 1260-1900 mAh/g.

Technical Field

The invention relates to the field of preparation of battery cathode materials, in particular to a silicon-based Si-C cathode material prepared based on silicon-based oxide, and a preparation method and application thereof.

Background

As the use of portable electronic devices and electric vehicles increases, the development of high energy density lithium ion batteries is urgently required. Graphite is a current commercialized lithium ion battery cathode material, the theoretical capacity of the graphite is 372mAh/g, and the high capacity requirement of the next generation lithium ion battery cannot be met. Therefore, there is an urgent need to develop a high-capacity, high-power-density negative electrode material instead of graphite. Silicon is used as a lithium ion battery cathode material, has the theoretical capacity up to 4200mAh/g, is rich in reserve and low in price, has the advantages of low lithium intercalation/deintercalation potential and the like, and is concerned. However, when the volume change of silicon exceeds 300% during charging and discharging, the silicon material itself is broken and pulverized to lose electrical contact activity, which causes problems of deterioration of charge and discharge rate performance, reduction of coulombic efficiency, and the like. In addition, silicon is a semiconductor and does not have good conductivity.

At present, methods for solving the volume expansion of silicon include nanocrystallization, porosification, doping modification and the like. And the side effect brought by the nanocrystallization is relieved through coating. Among them, combining silicon and carbon to form silicon-carbon composite materials with various structures is a common way. In the silicon-carbon composite material, carbon can effectively improve the conductivity of the electrode, and can buffer the volume change of silicon particles in the circulating process, thereby prolonging the circulating life of the electrode. However, most of the existing silicon-carbon composites are prepared by simply mechanically mixing silicon particles with carbon or by dispersing silicon in an organic carbon source such as phenol resin, PVA, citric acid, stearic acid, glucose, sucrose, polyvinyl alcohol, polyvinyl chloride, or polyethylene glycol and calcining and coating the mixture. The amorphous carbon formed after calcination isolates the contact between silicon and electrolyte, improves the stability of the material, but still has the problems of uneven silicon-carbon distribution, easy agglomeration of silicon particles, insufficient conductivity, easy ohmic polarization and the like. Meanwhile, the preparation process of the silicon-carbon composite material is complex in process and high in production cost.

Silicon-based oxides, such as silica and calcium silicate, are readily available, are large in scale, are low in cost, and are readily available as Si-C-O materials, such as silicon-containing biomass, carbonized products.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a silicon-based Si-C negative electrode material prepared based on a silicon-based oxide, a preparation method and an application thereof.

The invention relates to a preparation method of a silicon-based Si-C cathode material prepared based on a silicon-based oxide, which comprises the following steps:

step 1: preparation of

(1) Drying the calcium chloride-based molten salt raw material to obtain a calcium chloride-based molten salt raw material with water removed;

(2) under the protection of inert gas, weighing silicon-based oxide, calcium carbide and calcium chloride-based molten salt raw materials according to a ratio, grinding and uniformly mixing to obtain a mixed material, and sealing;

wherein, the silicon-based oxide is one or more of calcium silicate, silicon dioxide or Si-C-O compound;

in terms of mole ratio, the silicon-based compound: calcium carbide 1: (2-2.5); according to the mol ratio, calcium chloride in the raw materials of the calcium chloride-based molten salt is as follows: calcium carbide is more than or equal to 5: 1;

(3) placing the mixed material in an embedded crucible of a reactor, and sealing the reactor;

(4) introducing inert gas into the reactor, maintaining the inert atmosphere of the reactor and ensuring the reactor to be in positive pressure; heating the reactor while introducing inert gas;

step 2: synthesis of

After the temperature of the reactor is raised to the synthesis temperature, keeping the temperature for 1-5 hours to obtain a reaction mixture; the synthesis temperature is 600-800 ℃;

and step 3: post-treatment

And taking out the reaction mixture, cooling, grinding, pickling to remove salt, filtering, washing with water, and drying to obtain the silicon-based Si-C negative electrode material prepared based on the silicon-based oxide.

Wherein, in the step 1(1), the calcium chloride-based molten salt is prepared from the following raw materials: calcium chloride, or a mixed salt of calcium chloride and chloride; the chloride is one or more of sodium chloride, potassium chloride and magnesium chloride.

In the step 1(2), the inert gas is nitrogen, argon or a nitrogen-argon mixed gas.

In the step 1(3), the embedded crucible is a graphite crucible or a nickel crucible.

In the step 1(4), the inert gas is argon or argon-nitrogen mixed gas, and when the inert gas is argon-nitrogen mixed gas, the volume ratio of argon: nitrogen is more than or equal to 1: 1.

in the step 2, the reactor is heated by a resistance wire furnace, and the heating rate of heating to the synthesis temperature is 3-10 ℃/min.

In the step 2, the synthesis temperature is preferably higher than the melting temperature of the raw material of the calcium chloride-based molten salt plus (10 to 20) ° c.

In the step 2, after the temperature of the reactor is raised to the synthesis temperature, the stirring paddle can be inserted into the molten salt, stirring is maintained in the constant-temperature reaction process, and the rotating speed v of the stirring paddle is more than 0 and less than or equal to 700 r/min.

In the step 2, the stirring paddle is completely immersed in the molten salt, and the stirring paddle is driven to rotate by a frequency modulation motor.

In the step 3, a stainless steel crucible is used for cooling.

In the step 3, the salt is removed by acid washing, and the used acid is 0.1-0.2 mol/L hydrochloric acid.

In the step 3, the drying is vacuum drying, and the drying temperature is 50-80 ℃.

A silicon-based Si-C cathode material prepared based on silicon-based oxide is prepared by the preparation method.

The particle size of the prepared silicon-based Si-C negative electrode material particles prepared based on the silicon-based oxide is 50nm-50 mu m.

The negative electrode material comprises the silicon-based Si-C negative electrode material prepared on the basis of the silicon-based oxide.

The negative electrode material also comprises a conductive agent, a binder and a solvent.

An electrode plate comprises the anode material.

A lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the negative electrode adopts the electrode plate.

The particle size of the statically prepared silicon-based Si-C negative electrode material is 1-50 mu m, the first charge-discharge coulombic efficiency of the prepared lithium ion battery is 77-81%, the first discharge capacity is 2730-3100 mAh/g, and the first discharge capacity is 0.2 A.g^-1The specific capacity of 1180-1400 mAh/g is realized after the current density is circulated for 400 circles; when the particle size of the silicon-based Si-C negative electrode material prepared by stirring and dynamic preparation is 50nm-500nm, the first charge-discharge-coulombic efficiency of the prepared lithium ion battery is 75% -81%, the first discharge capacity is 2670-3000 mAh/g, and the first discharge capacity is 0.2 A.g^-1The specific capacity of the current density circulation is 500 circles, and the specific capacity is 1260-1900 mAh/g.

The invention relates to a silicon-based Si-C cathode material prepared based on silicon-based oxide, a preparation method and application thereof, wherein the silicon-based Si-C cathode material comprises the following raw materials: thermodynamic calculations show that: chemical reaction 2CaC₂+CaSiO₃＝Si+4C+3CaO，2CaC₂+SiO₂Si +4C +3CaO can proceed spontaneously. And the growth of product particles can be controlled by taking calcium chloride molten salt as a solvent, and the synthesis process of the silicon-based Si-C cathode material prepared based on the silicon-based oxide can be controlled, so that the Si-C cathode material of the lithium ion battery with excellent performance can be obtained through the reaction.

According to the invention, the reaction of the silicon-based oxide and calcium carbide and the generation process of the silicon-based Si-C negative electrode material prepared from the product based on the silicon-based oxide are regulated and controlled by regulating and controlling the salt composition and proportion, the synthesis temperature, the synthesis time, the stirring rate and the stirring time. The reaction rate is controlled, the uniform distribution of silicon and carbon in the Si-C product and the control of the particle size are promoted, the volume expansion of the silicon-lithium alloying process serving as the lithium ion battery cathode material is effectively buffered, the conductivity of the silicon material is improved, and the electrochemical performance is improved. The method uses low-cost silicon-based oxide and calcium carbide as raw materials to synthesize materials in calcium chloride-based molten salt, realizes low-cost, regulation and control preparation of the Si-C cathode material of the lithium ion battery, and has simple operation process. The prepared Si-C cathode material has uniform silicon and carbon distribution, moderate silicon particle size, and good specific capacity and cycle performance.

Detailed Description

The present invention will be described in further detail with reference to examples.

In the embodiment of the invention, the raw materials and equipment are commercially available and the purity is analytically pure or higher unless otherwise specified; in particular to the adopted calcium carbide, calcium silicate and silicon dioxide which are commercial products. The adopted ceramic mortar, nickel crucible and stainless steel crucible are commercially available products. The salts used were calcium chloride, potassium chloride, sodium chloride and magnesium chloride, the purity of which was analytically pure.

In the embodiment of the invention, the step of drying the calcium chloride-based salt to remove water is to place the calcium chloride-based salt in a high-temperature vacuum drying furnace, dry the calcium chloride-based salt for 12 hours at the temperature of 300 ℃ and under the pressure of-0.1 MPa, and remove adsorbed water and part of crystal water.

In the embodiment of the invention, the silicon-based oxide, the calcium carbide and the calcium chloride-based salt are ground and mixed uniformly in a ceramic mortar under the protection of inert gas.

In the embodiment of the invention, the gas outlet of the reactor extends to the lower part of the liquid level in the water tank outside the reactor through the pipeline, and bubbles emerge when argon gas continuously circulates.

In the embodiment of the invention, the temperature of the resistance wire furnace is heated by heating a reactor in the resistance wire furnace.

In the embodiment of the invention, the synthesis temperature is 10-20 ℃ higher than the melting temperature of the molten salt.