Lithium iron phosphate positive electrode material as well as preparation method and application thereof

Abstract

The invention provides a lithium iron phosphate positive electrode material as well as a preparation method and application thereof. The preparation method comprises the steps of (1) mixing a lithium source, an iron source, a phosphorus source and a solvent, and carrying out a hydrothermal reaction to obtain a lithium iron phosphate crystal; (2) grinding the lithium iron phosphate crystal obtained in the step (1), and sieving to obtain lithium iron phosphate particles with a first particle size and lithium iron phosphate particles with a second particle size; and (3) mixing the lithium iron phosphate particles with the first particle size and the lithium iron phosphate particles with the second particle size, which are obtained in the step (2), to obtain the lithium iron phosphate positive electrode material. According to the invention, firstly, the lithium iron phosphate crystal is prepared in a high-pressure heat-insulating ideal environment through a hydrothermal synthesis process, and by doping lithium iron phosphate active materials with different specific particle sizes, the diffusion impedance is reduced, the electrochemical kinetics is improved, and the low-temperature rate discharge performance of the lithium iron phosphate battery is improved.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and relates to a lithium iron phosphate cathode material and a preparation method and application thereof. Background technique [0002] In recent years, with the concept of "carbon peaking and carbon neutrality", new energy vehicles have ushered in an unprecedented market demand heat wave, and the poor low-temperature performance of high-energy lithium-ion batteries restricts their application in cold climates or northern regions. a major flaw. For conventional high-performance lithium iron phosphate batteries, under the same rate discharge conditions, the discharge capacity at 0°C is about 60% to 70% of the room temperature capacity, 40% to 50% at -10°C, and 40% to 50% at -20°C. 20% to 40%, such low-temperature performance obviously cannot meet the requirements of the power supply. Therefore, improving the low-temperature performance of LFP has become a major research hotspot in...

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Problems solved by technology

The compaction density of the lithium iron phosphate cathode material produced by it is high, but the compaction increases, and the infiltration of the electrolyte becomes poor, which will affect the cycle performance and low-temperature performance of the lithium-ion battery

[0004] CN103715452A discloses a low-temperature lithium iron phosphate lithium-ion power battery. The positive electrode active material it adopts is nanometerized lithium iron phosphate coated with a discontinuous graphene structure, wherein the median particle size of the nanometerized lithium iron phosphate is 5 -10nm, graphene is 3-8 layers of multilayer graphene, the coating area accounts for 40%-70% of the total surface area of ​​lithium iron phosphate material, and the positive electrode sheet made by it has a low compaction density, resulting in low energy density

[0005] The above solutions have the problems of poor low-temperature performance and cycle performance or low compaction density. Therefore, it is necessary to develop a lithium iron phosphate cathode material that can achieve a balance between high energy density and good electrical properties.

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