Composite silicate and carbon composite material, preparation method of composite material, and lithium ion battery containing composite material

Abstract

The invention discloses a composite silicate and carbon composite material, a preparation method of the composite material, and a lithium ion battery containing the composite material. The general formula of the composite silicate prepared by using the method is Li2FexMn(1-x)SiO4, wherein x is greater than or equal to 0 and smaller than or equal to 1. The preparation method comprises the following steps: (1) mixing a lithium compound, a ferrum compound, a manganese compound, a silicon compound and a carbon source; and (2) carrying out firing under inert atmosphere, so as to obtain Li2FexMn(1-x)SiO4 and carbon composite material. The preparation method is simple in technology and the cost is low. By using the method, both the surfaces of the composite silicate and the interiors of gaps of the composite silicate can be coated with the carbon. A conductive network can be formed in the way that the carbon is coated on the surface and in the gaps of the composite silicate, so that the conductivity of the composite material of the composite silicate and the carbon is enhanced; in addition, the composite material of the composite silicate and the carbon can be prevented from being dissolved and corroded by electrolyte; and the volume change resulting from a jahnteller effect of Mn<3+> is relieved.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a composite material of composite silicate and carbon, a preparation method thereof, and a lithium ion battery containing the material. Background technique [0002] With the advancement of science and technology, the requirements for energy storage equipment in the fields of electronic products (mobile phones, digital products, notebook computers, etc.), electric vehicles, medical equipment, and aerospace are increasing. At present, polyanionic cathode materials have been developed. , mainly phosphate cathode materials (LiMPO 4 ) and silicate cathode material (Li 2 MSiO 4 ) (where M=Mn, Fe, Co, etc.). Compared with phosphate cathode materials, silicate cathode materials can theoretically allow two lithiums to be deintercalated, thus having a higher theoretical specific capacity. Moreover, silicon has the highest content among the elements on the ear...

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Problems solved by technology

Silicate cathode materials synthesized by the sol-gel method generally have fine particles, uniform particle size distribution, good crystallization performance, and high initial capacity, but the synthetic raw materials generally use organic reagents, which are expensive and difficult for practical application

The solid-phase method synthesizes silicate cathode materials, and the operation process is simple, but the synthesized silicate cathode materials have large particles and poor uniformity. These factors will affect the electrochemical performance of silicate cathode materials.

In addition, silicate cathode materials have low conductivity and poor rate performance, so they need to be modified. At present, carbon coating or doping is generally used to improve their conductivity by solid-state methods.

The solid-phase method for the carbon coating of silicate cathode materials is often used in the preparation process, which needs to prepare the silicate cathode material by burning at high temperature first, and then burn the silicate cathode material and carbon source at high temperature for carbon coating. After a two-step high-temperature sintering process, carbon can only be coated on the surface of the silicate positive electrode material, and there is no carbon in the gaps of the silicate positive electrode material. The process is more complicated and the cost is high.

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