Suitable thickness of carbon coating layers for silicon anode

Silicon (Si) is capable of delivering a high theoretical specific capacity as anode in Li ion batteries (LIBs), but suffers from remarkable volume expansion, poor electrical conductivity and unstable solid electrolyte interface (SEI) film. Carbon coating is a facile and effective method to improve the electrochemical stability of Si anode. However, the electrode behavior performance of Si@C anode will be affected by the different thickness of carbon coating layer. Here, core-shell nanostructured Si@C materials with various thickness of carbon coating (around 2-30 layers) are prepared via the chemical vapor deposition with different deposition times. Especially, the Si@C composite with 2-3 carbon coating layers exhibits an outstanding electrical conductivity and strong mechanical strength, which is in favor of buffering the dramatic volume expansion of Si nanoparticles during the repeated lithiation/delithiation processes. As the anode material, the Si@C electrode exhibits a high capacity (3019 mA h g(-1) at 0.2 A g(-1)), excellent rate capability (1647 mA h g(-1) at 5 A g(-1)) and long-term cycling stability. Moreover, the excellent durability is also delivered by the full pouch-cell fabricated with Si@C anode and Ni0.6Co0.2Mn0.2O2 cathode. The huge volume expansion and unstable SEI film can be effectively alleviated by the suitable carbon coating layers. (C) 2021 Elsevier Ltd. All rights reserved.