Abstract
Metal oxides can deliver high capacity to Liion batteries, surpassing conventional graphite, but they suffer from a huge volume change during charging-discharging and poor cycle life. Herein, we merge the dual strategies of 3D-network support and sandwiching design to tackle such issue. We develop a skillful O-2-NH3 reactive pyrolysis of cellulose, where the preoxidation and the aminolysis result in the spatially separated charring of cellulose chains. A cellulose fiber is wonderfully converted into several ultrathin twisted graphenic sheets instead of a dense carbon fiber, and consequently, a cellulose paper is directly transformed into a porous flexible carbon paper with high surface area and conductivity (denoted as CP). CP is further fabricated as a 3D-network support into the hybrid CP@Fe3O4@RGO, where RGO is reduced graphene oxide added for sandwiching Fe3O4 particles. As a binder-free free-standing anode, CP@Fe3O4@RGO effectively fastens Fe3O4 and buffers the volume changes on cycling, which stabilizes the passivating layer and lifts the Coulombic efficiency. The anode thus presents an ultralong cycle life of >2000 running at a high capacity level of 1160 mAh g(-1). It additionally facilitates electron and ion transports, boosting the rate capability. CP and CP@Fe3O4@RGO represent a technological leap underpinning next-generation long-life high-capacity high-power batteries.