Preparation method of nitrogen and phosphorus co-doped carbon-coated graphite anode material

Abstract

The invention discloses a preparation method of a nitrogen and phosphorus co-doped carbon-coated graphite anode material, which comprises the following steps of: (1) coating, i.e. weighing graphite and ionic liquid, adding the graphite and the ionic liquid into a high-speed stirrer, carrying out dispersion for 1 to 4h at a rotating speed of 500 to 5,000r/min, and after completing processing, obtaining graphite coated with the phosphorus-containing ionic liquid; and (2) carbonization, i.e. placing the graphite coated with the phosphorus-containing ionic liquid in an atmosphere protection furnace to carry out sintering, heating to a temperature of 400 to 1,000 DEG C at a heating rate of 2 to 25 DEG C per min and carrying out heat preservation for 4 to 18 hours to obtain the nitrogen and phosphorus co-doped carbon-coated graphite anode material. By the structure, the electrical conductivity and the activity of a surface coating layer are greatly strengthened, not only the electronic conductivity of the nitrogen and phosphorus co-doped carbon-coated graphite anode material is effectively improved, but also diffusivity of lithium ions is greatly improved, and the obtained material has excellent rate capability and low-temperature discharge performance.

Description

technical field [0001] The invention relates to the technology in the field of negative electrode materials for lithium ion batteries, and in particular provides a preparation method for nitrogen and phosphorus co-doped carbon-coated graphite negative electrode materials. Background technique [0002] With the deepening of the global energy crisis, the depletion of oil resources and the increasing harm of air pollution and global temperature rise, it is imperative to develop clean energy. In the development of new energy, lithium-ion batteries, which have the advantages of high working voltage, high energy density, stable discharge voltage, long cycle life and environmental friendliness, are widely used. Anode materials are one of the key factors to evaluate the overall performance of lithium-ion batteries. At present, the commercially used lithium battery anode material is mainly graphite, which has the characteristics of low lithium extraction / intercalation potential (0-0...

AI Technical Summary

Problems solved by technology

However, at low temperatures, the ion diffusion capacity in the electrolyte in lithium-ion batteries has dropped by an order of magnitude. The industrially produced pitch-coated graphite coating is an amorphous carbon layer formed by high-temperature carbonization of pitch, which has low activity. The ability to intercalate lithium at low temperature decreases, which seriously affects the low-temperature charging ability of the overall battery, and ultimately leads to low-temperature performance and rate performance not meeting the requirements for use

At present, additives are usually added to the electrolyte to improve the interface between the electrolyte and graphite, which cannot effectively solve the problem of low-temperature lithium intercalation of graphite, and cannot meet the requirements of low-temperature operation and high-rate performance of lithium-ion batteries.

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