A composite graphite negative electrode material and a preparation method thereof, and a lithium ion battery

Abstract

The invention belongs to the technical field of lithium battery and relates to a preparation method of a composite graphite negative electrode material, comprising the steps of: 1) coating the surfaceof graphite powder with a metal oxide layer by an atomic layer deposition method; 2) uniformly mixing with that lithium salt powder, performing sintering at 300-1200 DEG C for 9-12h, reacting the metal oxide with the lithium salt to form a lithium ion conductor layer, and simultaneously allowing the metal oxide and the lithium salt to enter the graphite layered structure to form doping; 3) performing washing with water and drying. The invention also provides a composite graphite negative electrode material prepared by adopting the preparation method. The invention also provides a lithium ionbattery, wherein the negative electrode current collector surface is coated with the negative electrode material. The invention adopts ALD to coat graphite surface with the metal oxide, and then formsdense lithium ion conductor layer coating and doping of lithium ion and metal ion through high-temperature sintering, avoiding side reaction with organic electrolyte contact, facilitating lithium iontransmission, and improving lithium ion battery cycle stability and rate performance.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a composite graphite negative electrode material, a preparation method thereof and a lithium ion battery. Background technique [0002] At present, graphite, as the main anode material of lithium batteries, has attracted widespread attention due to its abundant resources, low price, high reversible capacity, low charge and discharge voltage platform, no voltage hysteresis, and excellent conductivity. [0003] However, graphite materials also have some disadvantages. For example, the graphite layers are combined by van der Waals force, the interlayer force is small and the interlayer spacing is small, so that the graphite interlayer spacing changes during the charging and discharging process, causing graphite flakes to peel off, Pulverization leads to unsatisfactory electrical cycle performance; moreover, the structural defects of graphite itself cause ma...

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Problems solved by technology

[0003] However, graphite materials also have some disadvantages. For example, the graphite layers are combined by van der Waals force, the interlayer force is small and the interlayer spacing is small, so that the graphite interlayer spacing changes during the charging and discharging process, causing graphite flakes to peel off, Pulverization leads to unsatisfactory electrical cycle performance; moreover, the structural defects of graphite itself cause many active groups on its surface, which are prone to side reactions with organic electrolytes, so the cycle life is poor and the battery is severely flattened, especially at high temperatures. and poor storage capacity

[0004] At present, some oxides are used to coat graphite powder. Although it can avoid side reactions of defects and functional groups on the surface of natural graphite in contact with organic electrolytes, it will make it very difficult to deintercalate lithium ions and export electrons, which will affect the reversible capacity of the electrode.

For doping graphite negative electrode materials with metal cations, the general method is to mix graphite with doping ion sources to achieve doping. This kind of doping cannot enter the graphite structure, it is easy to peel off, and the doping is uneven.