High tap-density lithium iron phosphate composite material and preparation method and application thereof

Abstract

The invention discloses a high tap-density lithium iron phosphate composite material and a preparation method and application thereof. The method includes the following steps: (1) phosphorus source, iron source, lithium source and a solvent are mixed and undergo wet ball-milling, the solid content is controlled at 15 to20 percent by weight, drying is carried out, and the mixture is then mixed withcane sugar and / or glucose and sanded until granularity D50 is equal to 0.2mu m to 0.3mu m; (2) presintering is carried out, so that a lithium iron phosphate precursor is obtained; (3) the lithium iron phosphate precursor is added into a mixed solution of lithium sulfite and lithium ascorbate, the solid content is controlled at 30 to 40 percent by weight, soaking and agitation are carried out, andspray drying is then carried out, so that spherical powder is obtained; (4) the spherical powder and acetylene black are mixed and undergo dry ball-milling until granularity D50 is equal to 1mu m to3mu m; (5) the mixed powder is sintered, so that the lithium iron phosphate composite material is obtained. Not only is the tap density of the lithium iron phosphate composite material disclosed by the invention high, but also produced batteries have high specific capacity and excellent cycle performance.

Description

technical field [0001] The invention relates to the technical field of electrode material preparation, in particular to a lithium iron phosphate composite material, a preparation method and use thereof, and in particular to a high tap density lithium iron phosphate composite material, its preparation method and use in lithium ion batteries. Background technique [0002] With the enhancement of people's awareness of environmental protection, new energy vehicles have attracted more and more attention, and the performance optimization of power lithium-ion batteries, which are important components of new energy vehicles, is particularly important and critical. Lithium iron phosphate is highly valued for its advantages of high charge-discharge efficiency, good cycle stability, high safety and environmental friendliness, and has been widely studied and applied. However, due to its low conductivity and low tap density, it is greatly limited. The zero-pollution cathode material is a...

AI Technical Summary

Problems solved by technology

Lithium iron phosphate has attracted much attention due to its high charge and discharge efficiency, good cycle stability, high safety and environmental friendliness, and has been widely studied and applied. However, due to its low electrical conductivity and small tap density, it greatly limits The zero-pollution cathode material application

[0003] However, compared with other battery materials, lithium iron phosphate also has the following disadvantages, mainly in two aspects: poor conductivity and low tap density

For the problem of poor conductivity, the main solution at present is metal ion doping and carbon coating. However, while solving the problem of poor conductivity, there are also problems of poor stability of the coating structure and the coating layer is easy to fall off. Some methods When the conductivity is improved, it will even lead to a further reduction in the tap density. For example, in the process of preparing carbon-coated lithium iron phosphate by means of solid-state reaction, most of them involve carbon coating or carbothermal reduction technology. During the reaction process, it hinders the growth of lithium iron phosphate grains. At the same time, most of the pyrolytic carbon of organic matter has a loose and porous form. Both of these effects reduce the tap density of lithium iron phosphate to a certain extent.

[0004] CN 103618083A discloses a production method of high-capacity and high-pressure compacted lithium iron phosphate positive electrode material, including: using a high-speed mixer to mix raw materials; primary tableting and sintering; secondary tableting and sintering; third tableting and sintering; After sintering, mixing and other steps, this method involves multiple processes of mechanical pulverizer crushing, ball milling, and high-pressure tabletting. The operation is cumbersome, and the compacted density, capacity, and cycle performance of the obtained product still need to be further improved

[0005] To sum up, it can be seen that the lithium iron phosphate prepared by the method of the prior art has the problem of relatively low compaction density, and the effect of improving the specific capacity and cycle performance needs to be further improved to meet the needs of practical applications.