Preparation method and application of carbon or transition metal doped iron-sulfur compound composite material

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method and application of a carbon or transition metal doped iron-sulfur compound composite material. The preparation method comprises the following steps: full mixing an organic solvent and an inorganic solvent to obtain a mixed solvent, adding an iron source, a transition metal source or a carbon source into the mixed solvent, heating to carry out organic-inorganic hybridization reaction, filtering, washing a filter cake, drying, and calcining the dried filter cake in a sulfur source environment to obtain the target product. The prepared carbon or transition metal doped iron-sulfur compound composite material is used as an active substance of a positive electrode material in an alkali metal ion battery.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, in particular to a preparation method and application of an iron-sulfur compound composite material doped with carbon or transition metal. Background technique [0002] With the advancement of technology and the improvement of people's living standards, more and more high-tech products appear in our daily life, such as Bluetooth headsets, mobile chargers, remote control aircraft, robots and electric lock access control, etc. One of the commonly used chemical power sources for these products is lithium-ion batteries due to their advantages of no memory effect, environmental friendliness and long life. However, at present, ternary materials, lithium iron phosphate, lithium cobalt oxide, etc. are commonly used commercially as positive electrode materials for lithium-ion batteries, and their theoretical specific capacity is low (<300mAh g -1 ), these have been unable to meet people'...

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Problems solved by technology

But FeS Z (Z≥1) The conductivity is poor, and the problem of volume expansion is prone to occur during charging and discharging, which affects the capacity decline, cycle performance and rate performance of the battery

There are two reasons for this: on the one hand, once the lithiation reaction occurs in the battery, the electron migration speed on the surface of the element Li is much faster than the electron migration speed inside the element, and the electron migration speed of FeS Z (Z≥1) The material cannot bear such a large volume change at all, and finally cracks appear from the bottom, and the material appears pulverized; on the other hand, some studies have shown that FeS Z (Z≥1) After the first cycle of charge and discharge, free iron ions and sulfur ions will be generated, both of which are easily soluble in the electrolyte to bring about the "double shuttle effect", causing capacity decline, and iron ions are also easy to deposit on the surface of the positive electrode , which hinders the contact between the SEI film on the surface of the positive electrode and the electrolyte, and the free iron ions and FeS 2 A reaction occurs that lowers the potential of the battery

[0004] For this reason, some researchers proposed to combine carbon network structure or transition metal oxide (Fe x o y ) and FeS Z (Z≥1) materials are recombined by means of compounding, doping or coating to alleviate the FeS Z (Z≥1) volume change, but still unable to relieve FeS Z (Z≥1) The problem caused by the generation of free iron ions after charging and discharging, and Fe x o y Medium Fe will aggravate the existence of this problem

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