A Novel Strategy for the Synthesis of Hard Carbon Spheres Encapsulated with Graphene Networks as a Low-Cost and Large-Scalable Anode Material for Fast Sodium Storage with an Ultralong Cycle Life
Carbon materials have drawn remarkable consideration as promising anode materials for high performance sodium ion batteries (SIBs). Developing the carbon-based anode is important for practical utilization of SIBs in energy storage technologies. Herein, hard carbon spheres encapsulated with graphene networks are prepared by a large‐scalable and low‐cost method, which delivers the better electrochemical performance, such as the rate capability and long-cycling life with respect to the ever reported hard carbon materials. The electrochemical test indicates that the as-prepared hard carbon anode exhibits a reversible capacity of 140 mA h g-1 under a current density up to 10 A g-1. Of special interest is that the capacity of 122 mA h g-1 is maintained after 4000 cycles, corresponding to the high capacity retention of 87.1%. The robust and flexible structure of the G-HCS material could facilitate the fast electrons and sodium ions transport rate, and sustain the fast sodium storage under high current rate owing to the construction of conductive graphene networks with outstanding electrical conductivity, enabling good contact between hard carbon spheres particles and graphene nanosheets. These results provide a rewarding avenue to design and optimize the advanced carbon anode materials for next‐generation SIBs.