Hierarchically porous nanosheets-constructed 3D carbon network for ultrahigh-capacity supercapacitor and battery...

An advanced hierarchically porous nanosheets-constructed three-dimensional (3D) carbon material (HPNSC) is prepared by using low-cost agricultural waste-nelumbium seed-pods as the precursor, and potassium hydroxide (KOH) as the activator. The as-prepared HPNSC material has a hierarchically porous nanosheets-constructed structure with 3D carbon nanosheet network morphology, which can enable fast and efficient transfer of Li⁺/Na⁺/H⁺ during charge-discharge process. The assembled HPNSC//HPNSC symmetric supercapacitors exhibit an improved energy density of 41.3 W h kg^-1 with a power density of 180 W kg^-1 in 1 mol l^-1 Na₂SO₄ electrolyte. The energy density can still be maintained at 16.3 W h kg^-1 even if the power density is increased to 9000 W kg^-1. When acting as the reversible electrode for lithium ion batteries, this HPNSC material can achieve a high specific capacity of 1246 mA h g^-1 at 0.1 A g^-1. Moreover, sodium ion battery with HPNSC electrode exhibits excellent cycling performance of 161.8 mA h g^-1 maintained even after being cycled 3350 times. The electrochemical performances clearly indicate that the HPNSC developed in this work is a very promising energy storage electrode material, and can further provide new insights for designing and developing highly porous materials for energy storage in other fields.