Enhanced electrochemical performance promoted by monolayer graphene and void space in silicon composite anode materials

The high specific capacity battery electrode materials have stimulated great research interest. Silicon (Si) as a low-cost abundant material with a theoretical specific capacity of 4200 mA h g(-1), offers an attractive option for the low-cost next-generation high capacity Li-ion batteries anode. However, successful applications of silicon anode have been impeded by several limitations such as large volume expansion (400%) with lithiation, poor conductivity and unstable solid electrolyte interphase (SEI) with cycles. To address these challenges, we engineered Si nanoparticles by encapsulating them with monolayer graphene (mGra) with empty space generated by melt-self-assembly Cu layer. Here, a new method is introduced to uniform encapsulate the nano-silicon particles. The synthesis process used low-cost Si nanoparticles and Cu foils via chemical vapor deposition methods. The mGra and void space around the Si nanoparticles guaranteed to overcome mentioned problems. The flexibility nature and high conductivity of mGra effectively accommodate the Si volume expansion associated with the lithiation, and function as charges fast channels that allow for ions and electrons transport in fast kinetics. Most important, the crystalized mGra layer served as a flexible protective layer avoiding the SNPs direct exposed to electrolyte, which boosted the formation of stable and thin SEI interface. Our anode demonstrated a high initial coulomb efficiency (CE) 85% with gravimetric capacity similar to 1450 mA h g(-1) (based on the total mass) and long cycle life (500 cycles with 89% capacity retention). Such SNP@void@mGra structure orienting excellent cycle life and high charge capacity provide a promising prospect for the next-generation high specific energy battery. (C) 2016 Elsevier Ltd. All rights reserved.