Nanometer lithium zirconate-modified lithium iron phosphate composite material and preparation method thereof

Abstract

The invention provides a preparation method of a nanometer lithium zirconate-modified lithium iron phosphate composite material. The preparation method comprises the steps of (1) dissolving cocamidopropyl betaine in water to form a solution A; (2) mixing and adding lithium hydrate, ferrous sulfate and phosphoric acid to form a mixed liquid B under protection of nitrogen atmosphere; (3) adding themixed liquid B into a hydrothermal kettle, and performing reaction in advance to obtain a middle product C; (4) adding an aqueous solution containing the cocamidopropyl betaine and polyvinyl pyrrolidone into the middle product C under the nitrogen atmosphere, adding zirconium nitride and excessive amount of lithium hydrate to form a mixed liquid E; (5) performing hydrothermal reaction to obtain amiddle product F; and (6) adding sorbitan laurate into the intermediate product F, and obtaining the composite material after calcination. In the composite material, lithium iron phosphate is used asa core, a nanometer lithium zirconate layer and a carbon layer are sequentially coated from inside to outside, the discharging capacity specific value is 78% or above at -20 DEG C to 25 DEG C, and thecapacity retention ratio after circulation for 1,000 times at 5C is 94% or above.

Description

technical field [0001] The invention relates to the technical field of cathode materials for lithium ion batteries, in particular to a lithium iron phosphate composite material modified with nanometer lithium zirconate and a preparation method thereof. Background technique [0002] Lithium iron phosphate (LiFePO 4 ) is an emerging cathode material for lithium-ion batteries that has great potential and has attracted widespread attention in recent years. LiFePO 4 It has the advantages of wide source of raw materials, relatively low price (about 1 / 5 of lithium cobalt oxide), non-toxic, environmentally friendly, high theoretical specific capacity (about 170mAh / g), and moderate working voltage (3.4V vs. Li+ / Li). What is more prominent is that it has very good thermal stability, superior safety performance (equal to nickel-cadmium batteries), good cycle performance and high specific energy. This also becomes LiFePO 4 The reason why it stands out among many cathode materials. ...

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Problems solved by technology

[0003] Although LiFePO 4 There are many advantages, but since LiFePO 4 Its own structural characteristics, its ion diffusion coefficient is only 10 -16 ~10 -14 cm 2 / s, the electron conductivity is only 10 -10 -10 -9 S / cm, which determines that it is not suitable for high-current charging and discharging, and its practical application is also greatly restricted.

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