Achieving fully reversible conversion in Si anode for lithium-ion batteries by design of pomegranate-like Si@C structure

• The pomegranate-like Si@C microspheres were successfully prepared with inexpensive AlSi alloy by surface modification, coating with resin, carbonization, and acid etching processes. • The distinctive pomegranate-like Si@C structure stabilizes the porous structure of Si particle and improves the electrochemical property. • As high as 84.98% ICE and 100% Coulombic efficiency were obtained for the sample (Si40@C3), which provide a helpful guide to synthesize the Si/C anode with high ICE and Coulombic efficiency and stable cycling. Si/C materials are considered as the most promising anodes for the next generation lithium ion batteries. However, the Si/C anodes with high Coulombic efficiency are still a challenge. Here, pomegranate-like Si@C microspheres are successfully prepared with inexpensive AlSi alloy by surface modification, coating with resin, carbonization and acid etching processes. As high as 84.98% initial Coulombic efficiency (ICE) and 100% Coulombic efficiency are obtained for the sample (Si 40 @C3), and the specific capacity still maintained over 620 mAh g −1 with capacity retention of 70.4% over 250 cycles. The excellent electrochemical performance could be attributed to the distinctive pomegranate-like Si@C structure, which either stabilizes the porous structure of Si particle by inhibiting the volume expansion and pulverization or improves the electrochemical property by the appropriate carbon coating layer. This would provide a helpful guide to synthesize the Si/C anode with high ICE and Coulombic efficiency and stable cycling.