Molten-NaNH2 Densified Graphene with In-Plane Nanopores and N-Doping for Compact Capacitive Energy Storage

5 years ago

Molten-NaNH2 Densified Graphene with In-Plane Nanopores and N-Doping for Compact Capacitive Energy Storage

Zhiyong Wang, Shuang Lin, Sheng Dai, Xianbo Jin, Chunyan Zhang

Capacitive carbons are attractive for energy storage on account of their superior rate and cycling performance over traditional battery materials, but they usually suffer from a far lower volumetric energy density. Starting with expanded graphene, a simple, multifunctional molten sodium amide treatment for the preparation of high-density graphene with high capacitive performance in both aqueous and lithium battery electrolytes is reported. The molten sodium amide can condense the expanded graphene, lead to nitrogen doping and, what is more important, create moderate in-plane nanopores on graphene to serve as ion access shortcuts in dense graphene stacks. The resulting high-density graphene electrode can deliver a volumetric capacitance of 522 F cm−3 in a potassium hydroxide electrolyte; and in a lithium-ion battery electrolyte, it exhibits a gravimetric and volumetric energy density of 618 W h kg−1 and 740 W h L−1, respectively, and even outperforms commercial LiFePO4. Highly capacitive graphene is prepared by a molten sodium amide treatment of expanded graphene at about 600 K. The treatment leads to densification and N-doping as well as creating in-plane nanopores to serve as ion transport shortcuts in the resultant dense graphene stacks, which delivers both high gravimetric and volumetric capacitances in both aqueous and lithium battery electrolytes.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201700766