Preparation method for carbon-coated silicon negative electrode material synthesized by aid of boron-nitrogen-doped polymer
阅读说明：本技术 一种硼氮掺杂聚合物辅助合成碳包覆硅负极材料的制备方法 (Preparation method for carbon-coated silicon negative electrode material synthesized by aid of boron-nitrogen-doped polymer ) 是由 杨立山 周君 李佳阳 于 2018-07-09 设计创作，主要内容包括：本发明为一种硼氮掺杂聚合物辅助合成碳包覆硅负极材料的制备方法,其特征在于按(0.01~5):(0.01~10):(1~10):(0.1~10)质量比称取纳米硅粉、含氮聚合物单体、含硼化合物和引发剂为固体原料,按(0.00001-10)g/mL固液比分散在浓度为0.01~5 mol/L的酸溶液中,控制温度在0oC~30oC反应1~20小时,再通过过滤、干燥得到含氮聚合物-硅前驱体,将此前驱体在不同的温度下保护气氛煅烧,得到硼氮掺杂的碳包覆硅的负极材料。本发明与现有技术相比首次库伦效率大于85%,在500mA/g电流密度下循环45圈后容量大于1500 mAh/g,容量保持率大于70%。该法制备工艺简单、易于操作、成本低廉,适用于高容量型锂离子电池负极材料。(The invention discloses a preparation method of a boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material, which is characterized in that nano silicon powder, a nitrogen-containing polymer monomer, a boron-containing compound and an initiator are weighed according to the mass ratio of (0.01-5) - (0.01-10) - (1-10) (0.1-10) to serve as solid raw materials, the solid raw materials are dispersed in an acid solution with the concentration of 0.01-5 mol/L according to the solid-liquid ratio of (0.00001-10), the temperature is controlled to be 0-30 ℃, the reaction lasts for 1-20 hours, a nitrogen-containing polymer-silicon precursor is obtained through filtration and drying, and the precursor is calcined under different temperatures in a protective atmosphere to obtain the boron-nitrogen doped carbon-coated silicon negative electrode material. Compared with the prior art, the coulombic efficiency is more than 85 percent for the first time, the capacity is more than 1500 mAh/g after the current density of 500mA/g is circulated for 45 circles, and the capacity retention rate is more than 70 percent. The method has simple preparation process, easy operation and low cost, and is suitable for the cathode material of the high-capacity lithium ion battery.)
1. A preparation method of a boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material is characterized by comprising the following steps:
① preparing an acid solution with the pH value of 0-4, uniformly mixing a silicon material, a nitrogen-containing polymer monomer, a boron-containing compound and an initiator according to the mass ratio of (0.01-5) - (0.01-10) - (1-10) - (0.1-10), dispersing in the solution according to the solid-to-liquid ratio of (0.00001-10) g/mL, controlling the temperature at 0-30 ℃, stirring for 1-20 hours, filtering, and drying at 50-200 ℃ for 1-20 hours to obtain the polymer-coated silicon material.
2, ②, annealing the polymer-coated silicon material at 300-850 ℃ for 1-24 hours under an inert atmosphere to obtain the boron-nitrogen-doped carbon-coated silicon negative electrode material, and using the boron-nitrogen-doped carbon-coated silicon negative electrode material as a battery negative electrode.
3. The method for preparing the boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material as claimed in claim 1, wherein the acid in the step ① is one or more mixed solutions of sulfuric acid, hydrochloric acid, nitric acid and oxalic acid, and the concentration of the mixed solution is 0.01-5 mol/L.
4. The preparation method of the boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material as claimed in claim 1, wherein the silicon material in the step ① is one or more mixed powder of nano silicon powder, silicon dendrite and silicon monoxide, and the diameter of the mixed powder is 10 nm-5 μm.
5. The method for preparing the boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material as claimed in claim 1, wherein the nitrogen-containing polymer monomer in the step ① is acrylonitrile (C)3H3N), aniline (C)6H7N), acrylamide (C)3H5NO), pyrrole (C)4H5N), pyromellitic dianhydride, diaminodiphenyl ether (C)12H12N2O) is used.
6. The method for preparing boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material as claimed in claim 1, wherein the boron-containing compound in the step ① is boric acid (H)3BO3) Boron trichloride (BCl)3) Sodium tetraborate (Na)2B4O7·10H2O) and sodium metaborate (NaBO)2) One or a mixture of several.
7. The method for preparing the boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material according to claim 1, wherein the initiator in the step ① is one of azobisisobutyronitrile, potassium permanganate, ammonium persulfate, hydrogen peroxide and potassium dichromate.
8. The method for preparing the boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material as claimed in claim 1, wherein the inert atmosphere in the step ② is nitrogen gas or argon gas, the purity is not less than 99%, or the volume ratio of the mixed gas of argon gas and hydrogen gas is 1 (0.001-0.5), and the flow rate is 0.01-10L/min.
Technical Field
The invention belongs to the field of lithium ion battery cathode materials, and particularly relates to a boron-nitrogen co-doped carbon-coated silicon method.
Background
Lithium ion batteries are widely used in the fields of portable electronic devices, electric vehicles/hybrid vehicles, energy storage systems, and the like, due to their advantages of high open circuit voltage, large energy density, long life, no pollution, small self-discharge, and the like. In order to meet the requirement of the national policy that the energy density of the power battery reaches 300Wh/kg in 2020, the improvement of the energy density of the lithium ion battery becomes a research hotspot. The improvement of the reversible specific capacity of the negative electrode material is one of the keys of improving the energy density of the lithium ion battery. Silicon has the highest theoretical specific capacity, and has the characteristics of rich source, low price, environmental friendliness and the like, so that the silicon is a hot point for researching the lithium ion battery cathode material. Currently, silicon used as a commercial anode still faces the problems of low conductivity, excessive cyclic volume expansion and the like, thereby limiting the popularization thereof.
Aiming at the above problems of the silicon cathode, a common solution is to perform composite modification on the nano silicon material. The carbon material has good conductivity, easy preparation and stable chemical and electrochemical properties, so the carbon material is gradually developed into a preferred composite material of the silicon cathode. The conductivity of the conductive polymer can be improved by doping, wherein the doping of the B, N element has a significant effect on improving the electron conductivity of the material. The annealed doped conductive polymer is adopted as the carbon for coating, so that the requirements of uniform coating, excellent conductivity, doping of various elements and the like are easily met. Chinese patent publication CN102394287A proposes a preparation method of core-shell silicon-carbon composite material formed by pyrolysis with CVD resin, ethylene oxide and the like as carbon sources; chinese patent ZL201310011798.3 discloses direct carbon coating of nano silicon powder by using water-soluble polymer as a carbon source, and the two methods both have the problem of common conductivity of the prepared coating material. Chinese patent CN106058257A utilizes S to replace graphene to construct a conductive network in a silicon negative electrode, and finally achieves higher conductivity, but this method is tedious in process and cannot achieve stable bonding between graphene and silicon material. For another example, patent CN106941174A discloses a nitrogen-doped silicon-carbon composite negative electrode material obtained by coating silicon with polyacrylamide carbide, and the electrochemical stability of the material obtained by the method needs to be improved. In addition, the Chinese patent CN105958036A carries out double-layer carbon coating on silicon powder, the carbon material relates to graphite, starch, cane sugar, polyvinyl alcohol, polyaniline, reduction/oxidation graphene and the like, the method process is complicated, and the product also has the problems of poor conductivity and stability and the like. Research shows that the electrical conductivity and chemical stability of the carbon material can be obviously improved by doping boron and nitrogen elements. For example, organoboron doping of boron elements into carbon materials has been used in the literature [ j. mater. chem. a, 2016, 5, 6 ] to successfully improve the conductivity thereof; the carbonization of polyaniline to obtain nitrogen-doped composite negative electrode materials is reported in the literature [ ACS appl. mater. interfaces.2015, 4, 14 ]. Research shows that at present, there are no patents and documents for obtaining boron-nitrogen co-doped silicon-carbon composite negative electrode materials by doping and annealing with a simple boron-containing inorganic substance as a boron source and a high-molecular nitrogen-containing compound as a nitrogen source.
Disclosure of Invention
The invention overcomes the defects of harsh conditions and high toxicity of the existing boron-doped technology, and designs a preparation method of a boron-nitrogen-doped polymer-assisted synthetic carbon-coated silicon negative electrode material, which is characterized by comprising the following steps:
① preparing an acid solution with the pH value of 0-4, uniformly mixing a silicon material, a nitrogen-containing polymer monomer, a boron-containing compound and an initiator according to the mass ratio of (0.01-5) - (0.01-10) - (1-10) - (0.1-10), dispersing in the solution according to the solid-to-liquid ratio of (0.00001-10) g/mL, controlling the temperature at 0-30 ℃, stirring for 1-20 hours, filtering, and drying at 50-200 ℃ for 1-20 hours to obtain the polymer-coated silicon material.
② annealing the polymer-coated silicon material at 300-850 ℃ for 1-24 hours under inert atmosphere to obtain the boron-nitrogen doped carbon-coated silicon negative electrode material, and using the boron-nitrogen doped carbon-coated silicon negative electrode material as a battery negative electrode.
The method for preparing the boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material as claimed in
The preparation method of the boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material as claimed in
The method for preparing the boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material as claimed in
The method for preparing boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material as claimed in
The method for preparing the boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material according to
The method for preparing the boron-nitrogen doped polymer assisted synthetic carbon-coated silicon negative electrode material as claimed in
Drawings
Fig. 1 is an XRD pattern of a boron-nitrogen doped carbon-coated silicon negative electrode material prepared in the first embodiment of the present invention;
fig. 2 is an XRD pattern of the boron-nitrogen doped carbon-coated silicon negative electrode material prepared in the fourth embodiment of the present invention;
fig. 3 is a scanning electron microscope low-magnification view of the boron-nitrogen doped carbon-coated silicon negative electrode material prepared in the second embodiment of the present invention;
fig. 4 is a scanning electron microscope high-magnification view of the boron-nitrogen doped carbon-coated silicon negative electrode material prepared in the second embodiment of the present invention;
fig. 5 is an infrared spectrum of a boron-nitrogen doped carbon-coated silicon negative electrode material prepared in the second embodiment of the present invention;
fig. 6 is an XPS chart of a boron-nitrogen doped carbon-coated silicon anode material prepared in the second embodiment of the present invention;
fig. 7 is a Mapping diagram of a boron-nitrogen doped carbon-coated silicon anode material prepared in the fourth embodiment of the present invention;
fig. 8 is a graph of rate performance of a boron-nitrogen doped carbon-coated silicon negative electrode material prepared in example two of the present invention;
fig. 9 is a cycle life diagram of a boron-nitrogen doped carbon-coated silicon negative electrode material prepared in the second embodiment of the present invention;
fig. 10 is a graph of rate performance of a boron-nitrogen doped carbon-coated silicon negative electrode material prepared in the fourth example of the present invention;
fig. 11 is a cycle life diagram of the boron-nitrogen doped carbon-coated silicon negative electrode material prepared in the fourth embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION