In situ formation of ionically conductive nanointerphase on Si particles for stable battery anode

Silicon (Si) is a promising anode candidate for next-generation lithium-ion batteries (LIBs) due to its high theoretical capacity. Solar Si photovoltaic waste possesses good purity and high output. Using it as the raw material for battery anodes can synchronously solve the problem of solid waste pollution and enable high energy density LIBs. A critical issue impeding the practical application of Si is the undesirable side reactions at the electrolyte-particle interface and the resulting increase in impedance during cycling. Herein, a Si-P core shell structure with chemical bonding at the Si-P interface is fabricated through a simple mechanical alloying reaction between red P and solar Si photovoltaic waste. The P nanoshell with thickness within 15 nm converts to Li3P during the initial lithiation process and maintains its phase on cycling. The as-formed Li3P nanolayer functions as a stable, ionically conductive protective layer that reduces the direct contact between Si and electrolytes, and thus suppresses undesired side reactions. The Si-P nanocomposite exhibits stable electrochemical cycling with a high reversible capacity of 1,178 mAhg−1 after 500 cycles at 1,200 mA g−1, as well as excellent rate capability (912 mAh g−1 at 2 C). With 15 wt% addition to graphite, a graphite/Si-P hybrid electrode shows a high overall reversible specific capacity of 447 mAh g−1 and 88.3% capacity retention after 100 cycles at high areal capacity of 2.64 mAh cm−2 at 100 mA g−1, indicating its promise as a drop-in anode in practical LIBs.