Surface Modifications of LiMn2O4 electrode for Aqueous Lithium Ion Batteries

Abstract

1. Introduction The rechargeable lithium-ion batteries (LIBs) have been considered as the power sources for the various applications from portable devices to high power applications such as electric vehicles and power storage for renewable energy [1]. However, their safety concerns and high cost are issues restricting their field for large scale energy storage system because the conventional LIBs contain the large energy and dangerous carbonate electrolyte. In this regards of safety and cost, the aqueous electrolyte can be the best candidate [2]. However, its practical application was limited due to its decreasing cycle life from poor electrochemical stability window. Here, we have shown that surface modifications of LiMn2O4 showed highly improved rate and cycle life in aqueous electrolyte. 2. Results and discussion The effect of the surface coating on the electrochemical properties of LiMn2O4 cathode in aqueous electrolyte solution was investigated by systematic electrochemical and instrumental analyses. The electrochemical performance of pristine LiMn2O4 and coated LiMn2O4 is presented. Despite the high ionic conductivity of the aqueous electrolyte (1 M Li2SO4 in water), the pristine LiMn2O4 did not show the high rate capabilities. In detail, the pristine and coated LiMn2O4 by 1,2, and 3wt.% AlF3 in aqueous electrolyte deliver the initial discharge capacity of 109.7, 106.6, 103.4 and 99.0 mAh g−1 at 1 C, respectively. The AlF3 coating has a dual role of surface stabilizer and resistance for lithium transportation. Based on these results, it is confirmed that the resistance from the surface failure mode of LiMn2O4 could be a main hurdle for cycle decaying especially in the aqueous electrolyte. After the surface modification of the electrochemically stable inorganic species, the rate capability and the cycle life are further improved. This coating enhance the surface stability to the aqueous solution and presents very promising cycle and rate capabilities for the development of ARLBs. Furthermore, they are investigated in detail by using XPS, SEM and TEM analyses. Acknowledgments This research was supported by the Post-Doctor Research Program (2014-2015) through the Incheon National University (INU) and the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Science, ICT & Future Planning (NRF-2014R1A1A1038248). Reference [1] M.R. Palacin, Recent advances in rechargeable battery materials: a chemist’s perspective, Chem. Soc. Rev. 38 (2009) 2565-2575. [2] W. Li, J.R. Dahn, D.S. Wainwright, Rechargeable Lithium Batteries with Aqueous Electrolytes, Science 264 (1994) 1115-1118.