Biomass-Derived Carbon Paper to Sandwich Magnetite Anode for Long-Life Li-Ion Battery

Metal oxides can deliver high capacity to Li-ion 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 O2-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 \u3e2000 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