Graphene nanowalls conformally coated with amorphous/nanocrystalline Si as high-performance binder-free nanocomposite anode for lithium-ion batteries

Silicon, one of the most promising candidates to replace graphite anodes in lithium-ion batteries (LIB), suffers from large volume change, structural instability, pulverization, shedding, and low conductivity. Here we present a LIB anode made of graphene nanowall (GNW) - Si nanocomposite (GNWs@Si). The GNWs featuring stable structure, large specific surface area, flexibility and excellent conductivity are grown by plasma-enhanced deposition directly on a Ni foam current collector. A mixed-phase silicon nano-layer is conformally and uniformly coated over the three-dimensional nanowall network, forming the GNWs@Si nanocomposite. Compared with conventional anodes, the GNWs@Si shows higher specific capacity, and better rate performance and capacity retention. The discharge specific capacities of the anodes made of pure Si and the GNWs@Si nano composite are 704.2 and 1116.2 mAh g(-1), respectively. The GNWs@Si outperforms pure Si in the corresponding capacity retention (relative to the discharge specific capacity in the 4th cycle) by showing 79.1% after 200 cycles as opposed to 50.4% for Si. The GNWs@Si anode features large electrochemical reaction areas, short and fast transport paths for Li+ and electrons, relieved internal stress caused by Si volume expansion, and excellent electrochemical performance.