Construction of a secondary conductive and buffer structure towards high-performance Si anodes for Li-ion batteries

Abstract

Nowadays, Silicon (Si) is known as the next generation anode of lithium ion batteries (LIBs), owing to its high theoretical capacity, low lithium storage potential and natural abundance. However, the huge volume expansion and poor conductivity of silicon anodes restrict their practical application due to their poor cyclability and unsatisfied rate performances. Herein, to improve the electrochemical performance of silicon anodes, a facile one-step injection pyrolysis was used to construct a novel secondary conductive and buffer structure where Si nanoparticles are conformally coated by the interconnected onion-like carbon and then are anchored in graphene nanosheets (GNS) skeleton. The synergy of interconnected ordered onion-like carbon coating layer and GNS favors for promoting fast electron transfers and improving electrochemical kinetics, which benefits for achieving an excellent rate performance. Additionally, layer-by-layer strain relaxation by onion-like carbon and flexible GNS hierarchically buffer the substantial variation in volume of Si and then endow the composite with good cyclability. Specifically, the anode of GNS@OLC-Si shows high reversible capacity of 1129.3 mAh g−1 after 300 cycles at a current density of 0.5 A g−1. In rate performance test, the capacity retention of the GNS@OLC-Si is high especially at high current density (66.2% at 2 A g−1). Hence, a new secondary structure is successfully designed to accelerate the diffusion kinetics and buffer the volume change of Si, thereby achieving stable cyclabilities and rate performances.