Free-standing monolithic nanoporous graphene foam as a high performance aluminum-ion battery cathode

Aluminum-ion batteries (AIBs) are emerging as an attractive new electrical energy storage system. Despite the recent breakthroughs in AIB technology, state-of-the-art cathode materials suffer from mediocre volumetric capacity (∼0.74 mA h cm^-3) and AIBs in the widely used coin-cell configuration are rarely reported. Here, we present the synthesis of free-standing monolithic nanoporous graphene foam with a high density and a new strategy to stabilize coin-cell type AIBs. Our designed coin-cell AIBs demonstrate a volumetric capacity up to 12.2 mA h cm^-3, a gravimetric capacity of 151 mA h g^-1 and good low temperature performance.