Lithium iron phosphate/carbon composite electrode material and preparation method thereof

Abstract

The invention relates to a novel lithium iron phosphate / C composite electrode material and a method for preparing the same, which belong to the technical field of lithium ion secondary batteries. The lithium iron phosphate / C composite electrode material is prepared by using iron phosphate as an iron source and a phosphonium source, using a macromolecular carboxylic acid lithium salt as a lithium source, using a carbon skeleton split product of the macromolecular carboxylic acid lithium salt as a carbon source, and performing solid phase reaction on the mixture of the iron phosphate and the macromolecular carboxylic acid lithium salt at a temperature of between 500 and 900 DEG C, wherein the mol ratio of lithium to iron to phosphate radical is 1-1.5:1:1, and the C content is 1 to 10 percent in percentage by weight. The carbon in-situ doping generated by the thermal decomposition of the macromolecular carboxylic acid lithium salt improves the electrical conductivity of lithium iron phosphate, and simultaneously the high viscosity of the macromolecular carboxylic acid lithium salt and the framework barrier effect of a thermal decomposition product can prevent component segregation, inhibit crystal grain growth, and are advantageous for improving the multiplying factor and the discharge performance of the material. The preparation method is simple and has good reproduction quality, and the lithium iron phosphate / C composite electrode material prepared by the method is black powder and has even granularity and high electrical conductivity.

Description

technical field [0001] The invention relates to a positive electrode material used as a lithium battery, a lithium ferrous phosphate lithium titanate / C composite electrode material and a preparation method thereof, belonging to the technical field of lithium ion secondary batteries. Background technique [0002] Lithium-ion secondary batteries have attracted people's attention due to their high voltage, no memory effect, high energy density, and good cycle performance. The positive electrode materials that determine the performance of lithium-ion batteries have always been a hot topic for researchers from all over the world. At present, lithium-ion battery cathode materials mainly include lithium cobaltate, lithium nickelate and lithium manganate. Due to the toxicity of cobalt and limited resources, the difficulty in preparing lithium nickelate, and the poor cycle performance and high-temperature performance of lithium manganate, it cannot meet the requirements of lithium-ion...

AI Technical Summary

Problems solved by technology

At present, the synthesis methods of lithium iron phosphate mainly include high-temperature solid-phase method, co-precipitation method, sol-gel method, etc. The high-temperature solid-phase method is prone to large particle size and component segregation; although the co-precipitation method solves the segregation phenomenon, the particle size Difficult to control; the reaction process of sol-gel method is difficult to control and takes a long time

[0003] However, the conductivity and ion diffusion rate of pure-phase lithium iron phosphate are low, which limits its application. In order to overcome the defect of low conductivity, many scholars adopt appropriate methods, such as patent CN1925195A, which uses lithium salt, ferrous oxalate and phosphorus salt as The main raw material, by adding additives to coat carbon on the surface to increase conductivity

However, the conventional method is to add an external carbon source (glucose, etc.), and the iron source and phosphorus source generally come from two kinds of compounds, which is not conducive to the dispersion of raw materials, and at the same time increases the reaction phase, making the performance difference of different batches of materials comparable. Large, not very reproducible