Method of preparing lithium iron phosphate cathode material through hydrothermal method, and the cathode material

Abstract

The application discloses a method of preparing a lithium iron phosphate cathode material through a hydrothermal method, and the cathode material. The method includes the steps of preparing carbon-coated LiFePO4 through the hydrothermal method and coating the carbon-coated LiFePO4 with a conductive polymer, wherein the preparation of the carbon-coated LiFePO4 through the hydrothermal method includes a step of only adding a lithium source, an iron source, a phosphorus source and a natural neutral water-soluble high molecular substance to a reaction system solution to prepare the carbon-coated LiFePO4; and the conductive polymer coating step includes the operations of 1) uniformly mixing the carbon-coated LiFePO4 with a resin-type high molecular substance through ball milling; and 2) performing high-temperature calcination to the mixture under a nitrogen atmosphere to obtain the lithium iron phosphate which is coated by both the conductive polymer and the carbon in a double-layer manner. In the application, the lithium iron phosphate is coated by both the conductive polymer and the carbon in a double-layer manner for the first time, wherein not only is excellent electric conductive efficiency ensured but also carbon is prevented from stripping off, so that the cathode material is improved in performance, is high in specific discharge capacity, is good in cycle performance and is low in cost, and establishes a basis for application of lithium ion batteries in the field of industrial macrocells.

Description

technical field [0001] The present application relates to the field of preparation of positive electrode materials for batteries, in particular to a method for preparing lithium iron phosphate positive electrode materials by using a hydrothermal method, and the prepared lithium iron phosphate positive electrode materials. Background technique [0002] Lithium-ion batteries were introduced to the market by Sony Corporation of Japan in the 1990s. Because of their high operating voltage, high energy density, and long cycle life, they are widely used in mobile phones, laptops and other small mobile power fields. With the further improvement of the energy density and power density of lithium-ion batteries, it has been regarded as an ideal power source for hybrid electric vehicles and pure electric vehicles, and is a type of energy storage device with broad application prospects; it has been further developed into aerospace applications. [0003] LiFePO 4 As a high-capacity lithi...

AI Technical Summary

Problems solved by technology

[0004] However, pure LiFePO 4 There are two major disadvantages of low electronic conductivity and small diffusion coefficient of lithium ions. Researchers have improved LiFePO by coating carbon layers or conductive polymers, and doping high-valence cations. 4 Electronic conductivity; and by reducing the particle size, thereby shortening the lithium ion transport path distance, in order to improve the LiFePO 4 Li-ion diffusion coefficient of

Coating invisible carbon is the simplest and most reliable improvement method, but there are also some shortcomings. During the charging and discharging process, the volume of the positive electrode material changes with the deintercalation of lithium ions, and the expansion and contraction of the volume will lead to the coating on the particles. The invisible carbon on the surface is easy to fall off, and the improvement effect cannot be continued

Coating conductive polymers can effectively solve the drop problem, but the conductivity of conductive polymers is lower than that of invisible carbon, which cannot significantly improve the electronic conductivity of lithium iron phosphate cathode materials

Images