Ultrathin paper-like boron-doped carbon nanosheet electrodes combined with boron-enriched gel polymer electrolytes for high-performance energy storage

Flexible energy storage devices that can function under considerable physical deformation have shown great promise for applications in portable electronics. In this work, we report for the first time a novel design of all-solid-state symmetric supercapacitors (SCs) based on free-standing ultrathin boron-doped graphene paper (B-GP) electrodes with boron-enriched gel polymer electrolytes (GPEs). Specifically, the B-GP electrodes integrated with B-containing GPEs not only introduce more electrochemically active sites for absorption/desorption of electrolyte ions, but also facilitate diffusion of the electrolyte during charging/discharging processes. The novel design of B-GP with B-containing GPEs endows our symmetric SC with a voltage of 2.5 V, an unprecedented energy density of 39.31 W h kg(-1) (with a power density of 1.44 kW kg(-1)), a stable cycling performance (a capacity retention of 90% after 3000 continuous charge/discharge cycles), good rate capability, distinguished mechanical flexibility and temperature resistant stability. This work provides a promising candidate to design a new generation of electrochemical SCs for energy storage devices.