Mixed conductor composite material LiFePO4-MXy and preparation method thereof

Abstract

The invention discloses a mixed conductor composite material LiFePO4-MXy. The mixed conductor composite material LiFePO4-MXy is prepared by synthesizing LiFePO4 from the oxides or sulfides of transition metals by a solid state method, and performing high-energy ball-milling and annealing on the transition metals to obtain the mixed conductor composite material LiFePO4-MXy. In the mixed conductor composite material (MCM) LiFePO4-MXy, MXy is not only a conductor of lithium ions but also a conductor of electrons, LiFePO4 particles are uniformly dispersed in the MXy, and the surface of the mixed conductor composite material in a lithium ion battery comprises a carbon material which is added in size mixing and electrolyte which is impregnated in the carbon material. The LiFePO4-MXy has the advantages of high electron conductivity, high ion conductivity, high high-rate charge and discharge capacity, high cycle performance, relatively higher tap density, simple and practical production process, cleanness, no pollution, low cost and the like, and is suitable for large-scale production.

Description

technical field [0001] The invention belongs to the field of preparation of lithium ion battery cathode materials, in particular to a LiFePO 4 -MX y Mixed conductor composite material and method for its preparation. Background technique [0002] The energy problem is a common problem faced by mankind in the 21st century, and electric energy is the most convenient form of energy. Among them, lithium-ion batteries have become a global research and development hotspot due to their outstanding advantages such as light weight, high energy density, long cycle life, low self-discharge rate, no memory effect, and environmental protection. At the same time, the demand for power in the electronics industry, IT industry, communication industry and other fields has soared. Lithium-ion batteries have become portable electrical appliances and The first choice for power supply of electronic instruments. [0003] The main components of lithium-ion batteries are positive electrode, negat...

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Problems solved by technology

However, lithium iron phosphate has two obvious disadvantages: one is low electrical conductivity, of which the electronic conductivity is only 10 -10 On the order of S / cm, the lithium ion diffusion rate is only 10 -14 cm 2 / s order of magnitude, leading to poor high-rate discharge performance and low actual specific capacity, especially when discharging with a large current, the electrode polarization is serious, resulting in increased irreversibility of charge and discharge, and serious loss of electrochemical capacity; second, the low bulk density leads to The volume specific capacity is low, which brings certain difficulties to the application of lithium iron phosphate

However, the compounds added in the above invention only have high electronic conductivity or the ability of compounds that are beneficial to lithium ion transport, and can only improve electronic conductivity or lithium ion diffusion rate capabilities, so the electrochemical performance of lithium iron phosphate cannot be greatly improved.

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