Nano-spatially stable Si2O composite and its balanced electrochemical performance for Li rechargeable batteries

Abstract

Si-based materials are being actively investigated for use in high-capacity anodes as an alternative to commercial graphite electrodes for Li-ion rechargeable batteries. Among these materials, Si suboxides (SiOx) are considered to be good candidates because their cycling stability is better than that of pure Si-based materials. However, their initial Coulombic efficiency (ICE) is still a major obstacle. In this study, we propose a SixO composite (x = ∼2) to overcome the ICE shortfall while achieving superior cycle performance. The material is simply synthesized via high-energy mechanical milling to meet the requirements of a facile commercial mass-production method. Material characterization results demonstrate that the composite is almost amorphous by X-ray diffraction and that Si nanocrystallites (<10 nm) are uniformly distributed in the SiOx matrix. Electrochemical tests show that a reversible capacity of 2157 mAh g−1 is obtained with an ICE of 82%. The cycle performance is excellent after carbon incorporation. These results can be attributed to nano-spatially and uniformly distributed Si in the SiOx matrix. To examine commercial feasibility, full cells are tested with a high-Ni cathode (LiNi0.8Co0.1Mn0.1O2) and exhibit excellent performance in terms of cycle and rate capabilities.