▎ 摘　　要

NOVELTY - Preparation of sandwich structure porous carbon/graphene/porous carbon composite carbon nanosheet comprises mixing graphene oxide, resorcinol, and formaldehyde for 140-160 minutes; adding oxalic acid and reacting for 200-260 minutes; and separating solid-liquid system, drying solid, and carbonizing for 2-3 hours at 700-850 degrees C. USE - The method is used for preparation of sandwich structure porous carbon/graphene/porous carbon composite carbon nanosheet for preparing manganese(II) oxide-reduced graphene oxide-manganese(II) oxide composite nanosheet material (claimed). ADVANTAGE - The composite carbon nanosheet can be used as cathode material for zinc ion batteries. The method is simple and has low cost. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of manganese(II) oxide-reduced graphene oxide-manganese(II) oxide composite nanosheet material comprising mixing porous carbon/graphene/porous carbon composite carbon nanosheet and potassium permanganate in water and reacting for 12-72 hours.