Preparation method for lithium ion fast conductor modified lithium iron phosphate material

Abstract

The invention relates to a lithium ion battery positive material, in particular to a preparation method for a lithium ion fast conductor modified lithium phosphate material. The preparation method is characterized by comprising the following steps: (1) according to the components of the lithium ion fast conductor, covering raw materials including a lithium source, an A source, a B source, an N source, a silicon source and a phosphorus source are mixed with lithium iron phosphate to be covered to form a precursor, and then the precursor is dried; (2) the obtained precursor is sintered in an inert atmosphere, the sintering temperature is 400-1,000 DEG C, and the soaking time is 2-20 hrs. In the preparation method, a layer of lithium ion fast conductor film is compound on the surface of a nano lithium iron phosphate, so as to greatly improve the power performance of the nano lithium iron phosphate; particularly, the glass state lithium ion fast conductor is a well-know favorable and stable lithium conductor, at the same time, favorable conductivity is acquired by adulterating a transition metal; and adopting the material prepared by the invention to manufacture batteries, more than 40 c high current charging / discharging can be achieved.

Description

technical field [0001] The invention relates to a lithium ion battery cathode material, in particular to a preparation method of a lithium ion fast conductor modified lithium iron phosphate material. Background technique [0002] Since the advent of lithium-ion batteries in 1991, their cathode materials have been a hot spot in material research. The current research mainly focuses on transition metal oxides containing lithium, and the transition metals are mainly nickel, cobalt, and manganese. In recent years, due to the abundance of iron in the earth's crust, its cheap price, and environmental friendliness, based on Fe 2+ / Fe 3+ Redox-coupled substances have aroused great interest, so people are racing to study iron-containing lithium salts to replace current cathode materials. [0003] In the prior art, the positive electrode active material LiFePO is generally prepared by solid phase method or wet chemical method. 4 , such as CN 1401559A discloses a lithium iron phosp...

AI Technical Summary

Problems solved by technology

However, when using the solid-phase method, it is difficult to mix various solid components fully, so the various components in the obtained lithium iron phosphate positive electrode active material, especially the conductive agent, are not uniformly dispersed, which directly affects the conductivity of the positive electrode active material.

[0004] So far, there have been many reports on the synthesis methods of materials. The most researched and most likely to realize industrialization is the high-temperature solid-phase method, but lithium iron phosphate has its inherent shortcomings, such as low lithium ion diffusion coefficient and poor conductivity. etc. Therefore, the materials prepared by the conventional method have disadvantages such as poor electrochemical performance, uneven particle size distribution, and low tap density.

In order to improve the performance of the material, it is generally doped or coated, such as C coating (CN101172599, CN101442117, CN101764205A, CN101777636A), transition metal doping (CN1785799), rare earth doping (CN1830764, CN101630738), etc., The above methods can improve the performance of lithium iron phosphate to a certain extent, but the performance improvement is not too significant

Especially in the selection of rare earth elements, which are usually common rare earths, but the valence changes a lot, resulting in easy disproportionation during the reaction and product charging and discharging, and the performance of its lithium iron phosphate is significantly reduced