Si@C anode materials decorated with higher manganese silicides for enhanced rate capability and cycle stability

Abstract

The poor cycle stability and high price are primary drawbacks of Si-based anode materials to their wide applications. Partially alloying silicon with transition metals together with carbon coating is effective in improving the cycle performance. Herein, higher manganese silicides (HMS) are decorated on carbon coated silicon, denoted as Si@HMS@C, by coating microscale waste Si powders recovered from photovoltaic industry with in situ polymerized resorcinol formaldehyde (RF) resin, followed by absorbing manganese acetate tetrahydrate and thermal pyrolizing in flowing N2 gas. As compared to the carbon coated silicon anode (Si@C), the Si@HMS@C anodes exhibit greatly enhanced cycle performance and rate capability. A reversible capacity of 1070 mAh g−1 is maintained after 400 cycles at 0.4 A g−1. The ex situ XRD measurements as well as microstructure investigation before and after cycle test reveal that the phase and morphology of HMS keep unchanged. Meanwhile, reversible redox reactions associating to the reaction of Li with HMS or with its derivatives induced by the initial irreversible side reaction of HMS with electrolyte are identified. These results suggest that the HMS might have played multifunctional roles on improving the Si anode’s electrochemical performance, including stabilizing the structure, increasing the electronic conductivity and contribute additional capacity.