N/O co-doped hierarchical porous carbon nanosheets with enhanced Zn-ion storage capability and ultrastability

N/O co-doped hierarchical porous carbon nanosheets were produced from magnolia tree. A capacity of 234.3 mA h g −1 at 0.1 A g −1 with 105.2 mA h g −1 at 50 A g −1 , 181.6 Wh kg −1 energy density and 96.9% ultrastability after 100 000 cycles were gained.