Graphene coated lithium titanate cathode and preparation method thereof

Abstract

The invention discloses a graphene coated lithium titanate cathode and a preparation method thereof. The graphene coated lithium titanate cathode is prepared from the following components including lithium titanate and flake graphite according to the ratio of 50 to 1-400 to 1, and preferentially, 100 to 1. The preparation method comprises the following steps: soaking the flake graphite with N-methyl pyrrolidone, serving as a solvent, softening by infiltration, then putting a lithium titanate cathode material after softening by infiltration into a mixed solution of the flake graphite and the N-methyl pyrrolidone, then putting the mixed solution of the lithium titanate cathode material after softening by infiltration, the flake graphite and the N-methyl pyrrolidone into a sand mill, grinding with a zirconia ball, serving as a sand milling medium, filtering to remove the N-methyl pyrrolidone solvent, evaporating, drying, completely removing the residual N-methyl pyrrolidone solvent, and thus preparing the graphene coated lithium titanate cathode. According to the graphene coated lithium titanate cathode and the preparation method disclosed by the invention, proved by charge-discharge cycle tests by assembling batteries, the capacity of the graphene coated lithium titanate cathode is increased, and the phenomenon of gas expansion is improved.

Description

Technical field [0001] The invention relates to the field of lithium ion batteries, in particular to graphene-coated lithium titanate negative electrodes and a preparation method thereof. Background technique [0002] Current lithium-ion power batteries usually use lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium spinel manganese oxide as the positive electrode material, and carbon as the negative electrode material. Under abuse conditions, the electrolyte of these batteries will interact with the lithium-intercalated carbon negative electrode. The chemical reaction emits a lot of heat, causing the battery to catch fire and explode. The safety problem of large-capacity and high-power lithium-ion power batteries with carbon as the negative electrode has not been effectively solved, which restricts the development of its industrialization. At the same time, the diffusion coefficient of lithium ions inside the carbon-based electrode is small, the lithium-i...

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Problems solved by technology

[0035] In order to overcome the defects of the existing lithium titanate negative electrode materials such as fast capacity decay and poor rate performance during high-current charge and discharge, a graphene-coated lithium titanate negative electrode and a preparation method thereof are provided. Lithium oxide negative electrode material is coated, and the theoretical specific surface area of ​​graphene is 2600m 2 / g [Fan Yanru et al.: Graphene non-covalent bond functionalization and application research progress, Chemical Industry Progress 2011 Volume 30] is Φ7 ~ 15nm carbon nanotube specific surface area 190 ~ 260m 2 / g more than 10 times that of carbon black Super P Li 62m 2 40 times that of / g, compared with the existing carbon nanotube or carbon black coating, less raw materials can be used to avoid reducing the specific capacity of the material. Graphene is used to coat lithium titanate to improve the capacity during high-current charging and discharging. Defects of fast attenuation and poor rate performance can improve the problem of flatulence. At the same time, in view of the oxidation defects and environmental pollution defects caused by the graphene preparation process in the existing disclosed lithium titanate coating technology, the further optimized scales of the present invention Graphene prepared from graphite and coated with lithium titanate

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