Interfacial Control for Enhanced Cycling Performance of Li-Ion Battery with Silicon-Based Anode and High-Voltage Layered Oxide Cathode

Advanced portable electronics, electric vehicles and energy storage systems need more than doubled energy density lithium-ion battery than current one consisting of graphite anode and LiCoO₂ cathode. High-capacity silicon-based anode materials and high-voltage three-components layered oxide cathode materials have been actively researched for higher energy density batteries. Various methods for improving the cycling performance of silicon-based anode have been developed but mostly evaluated using a half-cell configuration.^1,2 Just few reports on the performance of high-energy full-cells with silicon-based anode together with high-voltage cathode have been reported.^3–5 This is associated with poor cycling ability of silicon-based anodes and continuous oxidative electrolyte decomposition above 4.3 V vs. Li/Li⁺. Nonetheless, interfacial reaction mechanisms for performance fade or enhancement of full-cells have not been studied in depth. Interfacial control with electrolyte components and surface structural stabilization of both anode and cathode are promising approaches for enhancement of full-cell performance.^6,7 In this presentation, we report the enhanced cycling performance of high-energy full-cell with silicon-carbon composite anode and high-voltage layered LiNi_0.5Co_0.2Mn_0.3O₂ cathode (NCM) by interfacial control and the role of electrolyte component in enhancing the performance.

The 2016 coin full-cells of NCM//silicon-carbon composite were assembled with different electrolyte compositions. Cycling performance of full-cells was tested between 3.0 and 4.55 V at the rate of C/3 (330 mAg^-1) for 100 cycles. Impedance spectroscopy, Raman spectroscopy, FT infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscope have been used to analyze electrochemical behaviors depending on electrolyte composition and surface chemistry of both cathode and anode.

Figure 1a-b compare the cycling performance of NCM//silicon-carbon composite full-cells in the conventional electrolyte of 1M LiPF₆/EC:EMC (3:7) and a new electrolyte consisting of new solvents and additives. With the conventional electrolyte, the full-cell shows a rapid capacity fade and a low coulombic efficiency over 100 cycles. In contrary, the full-cell with a new electrolyte exhibits a significant performance enhancement; capacity retention is 71 % at the 100th cycle, and coulombic efficiency is maintained as higher than 99 %. Surface analyses of cathode and anode reveal that with new electrolyte a stable solid electrolyte interphase (SEI) layer forms at both surfaces of cathode and anode and a metal dissolution event from cathode is inhibited. Further discussion on interfacial control-performance relationship would be presented in the meeting.

Acknowledgements

This research was supported partly by the Korean Ministry of Education (2012026203) and partly by the Korean Ministry of Trade, Industry & Energy (A0022-00725 & 10049609).

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