A helium-doped modified lithium iron phosphate thin film positive electrode material and preparation method thereof

Abstract

The invention discloses a preparation method of a helium-doped modified lithium iron phosphate thin-film positive electrode material. The method comprises the following steps: plating a current collector of a positive plate with a LiFePO<4> thin film through a magnetron sputtering method, and introducing He gas at the same time to dope He into the LiFePO<4> thin film; and performing high-vacuum annealing on an obtained LiFePO<4> / He thin-film positive electrode material in a conventional way, wherein the prepared thin film has a porous structure and a b-axis crystallization preferred orientation characteristic, and the content of He atoms is 8-34 atom percent. A discharge capacity of a button type lithium ion battery assembled with the positive electrode material is 84-141mAh / g at a 0.1C test rate, and an electric capacity attenuation rate of 50 cycles is 14.2-24.0 percent. The prepared thin-film LiFePO<4> positive electrode material has a higher electric conductivity and shorter ion and electron transport paths, thereby improving the discharge capacity, rate performance and cycle performance of the lithium battery, and greatly improving an electrochemical performance of the material. Moreover, a process is simple, mature and easy to grasp and control.

Description

technical field [0001] The invention belongs to the technical field of thin-film cathode materials in lithium ion batteries and their preparation, and in particular relates to a helium-doped modified lithium iron phosphate thin-film cathode material and a preparation method thereof. Background technique [0002] As a new type of chemical power source, lithium-ion batteries have become a hot spot in the field of new energy materials due to their advantages such as high output voltage, high specific energy, long cycle life, small self-discharge, safety, no memory effect, and environmental friendliness. [0003] For thin-film lithium batteries, the cathode material is a key factor affecting the performance of lithium-ion batteries. Currently, the commonly used cathode materials for thin-film lithium-ion batteries include LiCoO 2 , LiMn 2 o 4 、LiFePO 4 Wait. Among them, LiFePO 4 Because of its advantages such as low cost, non-toxicity, long cycle life, and good thermal sta...

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Problems solved by technology

However, there are still deficiencies in this type of modification method: First, although the doping of transition group elements can improve the bulk electronic conductivity of the material, it has little effect on the size of the material, and it is not easy to increase the lithium ion diffusion rate of the material, so it is difficult for The improvement of the electrochemical performance of the material is limited; second, LiFePO 4 The metal ion doping of positive electrode materials often involves basic processes such as batching, mixing (ball milling), heat treatment, and sintering. Among them, only mixing takes 12 to 24 hours, and sintering takes 4 to 6 hours. Longer time reduces the production efficiency of positive electrode materials; third, due to the high cost of some metal cations and the need for long-term high-temperature sintering in an inert gas atmosphere, LiFePO is virtually increased. 4 Preparation cost of cathode material

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