On the Interface Design of Si and Multilayer Graphene for a High-Performance Li-Ion Battery Anode

Si/multilayer graphene (mG) is a promising candidate for the next-generation Li-ion battery anode. The highly ordered mG shows intrinsic good stability against the liquid electrolyte and its flexibility to accommodate volume change. Until now, reducing the growth temperature and thus engineering the interphase are a very important research area, but only few studies have been reported. Herein, for the first time, the mG is grown with the Al₂O₃ catalyst at a relatively low temperature of 750 °C, while the thickness is controlled to 2 nm. The growth of mG obeys the Stranski-Krastanov mechanism. Applying a rapid cooling process, a silicon oxycarbide (SiOC) interlayer is in situ-fabricated between the mG coating layer and Si core. The SiOC interlayer is demonstrated to accommodate the volume change of Si and enable faster lithium ion transportation than mG. Taking synergetic advantages of the mG coating layer and SiOC interphase, the cycling stability significantly improved, and a high specific capacity of 990 mA h/g is obtained at 1 A/g after 500 cycles in half cells. A high rate performance of 1164.5 mA h/g at 4 A/g is achieved. Tested in a 1.8 A h pouch cell with LiNi_0.5Mn_0.3Co_0.2O₂ (NMC532) as the cathode, the cell delivers a specific energy of ∼380 W h/kg. The capacity retentions are 93% and 78% after 100 cycles and 200 cycles, respectively. Our work highlights the importance of the interphase design of Si/mG composite anodes, which could also be extended to various core-shell materials in energy storage materials.