Sputtering Coating of Lithium Fluoride Film on Lithium Cobalt Oxide Electrodes for Reducing the Polarization of Lithium-Ion Batteries.

Shasha Qu,Qingshui Xie,Qiulong Wei,Jie Lin,Wenbin Wu,Yanping Zhuang,Dong-Liang Peng,Yunfan Wu,Laisen Wang

doi:10.3390/nano11123393

Abstract

Lithium cobalt oxide (LCO) is the most widely used cathode materials in electronic devices due to the high working potential and dense tap density, but the performance is limited by the unstable interfaces at high potential. Herein, LiF thin film is sputtered on the surface of LCO electrodes for enhancing the electrochemical performance and reducing the voltage polarization. The polarization components are discussed and quantified by analyzing the relationship between electrochemical polarization and charger transfer resistance, as well as that between concentration polarization and Li-ion diffusion coefficients. In addition, the decreased charge transfer resistance, increased lithium-ion diffusion coefficients, and stabilized crystal structure of LiF-coated LCO are confirmed by various electrochemical tests and in-situ XRD experiments. Compared to that of pristine LCO, the capacity and cycling performance of LiF-coated LCO is improved, and the overpotential is reduced upon cycling. This work provides reference for quantifying the various polarization components, and the strategy of coating LiF film could be applied in developing other analogous cathode materials.

Highlights

Lithium-ion batteries (LIBs) are widely used in energy storage equipment due to their high energy density, good cycling stability, and environmental friendliness [1]
The cathodes have been commercialized over the years, Lithium cobalt oxide (LCO) still occupies the dominant position in portable electronics due to the high theoretical capacity, stable cycling performance, high working potential, and facile synthesis [7,8]
The surface morphology characteristics of LCO electrodes with or without LiF coatings were observed by field emission scanning electron microscope (FESEM, HitachiSU-70, Japan Hitachi High-Tech Naka Business, Tokyo, Japan)

Summary

Introduction

Lithium-ion batteries (LIBs) are widely used in energy storage equipment due to their high energy density, good cycling stability, and environmental friendliness [1]. Using layer surface deposition [22],material plasma laser deposition [23], magnetron production of liquid electrolyte, LiF can buffer the further decomposition of liquid sputtering [14], and other physical vapor deposition routes, the uniform and pure thin electrolyte. As a cathodes [24], few reports study about increasing the energy efficiency (charge/discharge result, radio-frequency (RF) magnetron sputtering is utilized to fabricate the LiFenergy) or decreasing the voltage hysteresis (charge/discharge voltage) by coatings. Compared to that of the pristine the LiFpolarization and electrochemical polarization of LCO electrodes, which are LCO, confirmed by coated exhibits higher capacity, better cycling performance, and lower overpotential theoretical analysis and experimental tests. Li-ion diffusion coefficients, LiF-coated exhibits higher capacity, to better performance, and lower overpodecreased charger transfer resistance, and suppressed interfacial reaction by the LiF tential upon cycling. Decreased charger transfer resistance, and suppressed interfacial reaction by the LiF coating

Sample

Materials Characterization

Electrochemical Tests

Results and Discussion

Electrochemical

Conclusions