A Si@SiOC@Li2Si2O5 anode derived from pyrolysis of polysiloxane enables lithium-ion batteries to exhibit high electrochemical performance and high initial coulombic efficiency

Silicon oxycarbide (SiOC) is an attractive anode material for lithium-ion batteries (LIBs) because of its good thermodynamic stability and high theoretical specific capacity, but is limited by its low initial coulombic efficiency (ICE) and poor cycling stability. Herein, a Si@SiOC@Li2Si2O5 (SSL) anode was synthesized for the first time. Si not only increases the specific capacity but also improves the ICE of the SSL anode. Li2Si2O5 serves as an inert phase to accommodate volume changes of Si, thus effectively improving the electrochemical stability of SSL. Additionally, density functional theory calculations prove that the many Li–O ionic bonds and O–H hydrogen bonds between SiOC, Li2Si2O5, and PAA binder highly enhance the adhesion strength of the SSL anode. Therefore, the SSL anode shows a high ICE of 73.05% and a high specific capacity of 733 mA h g−1 with a capacity retention of 91.5% after 500 cycles at 0.5 A g−1. In addition, SSL exhibits a rate performance of 393 mA h g−1 even at a high rate of 4 A g−1. This work provides a new direction for the development of silicon-based anode materials for high-capacity, high ICE, and long-life LIBs.