4 years ago

Flexible MXene/Graphene Films for Ultrafast Supercapacitors with Outstanding Volumetric Capacitance

Flexible MXene/Graphene Films for Ultrafast Supercapacitors with Outstanding Volumetric Capacitance
Babak Anasori, Asya Sarycheva, Christine B. Hatter, Chang E. Ren, Kathleen Maleski, Jun Yan, Yury Gogotsi, Patrick Urbankowski
A strategy to prepare flexible and conductive MXene/graphene (reduced graphene oxide, rGO) supercapacitor electrodes by using electrostatic self-assembly between positively charged rGO modified with poly(diallyldimethylammonium chloride) and negatively charged titanium carbide MXene nanosheets is presented. After electrostatic assembly, rGO nanosheets are inserted in-between MXene layers. As a result, the self-restacking of MXene nanosheets is effectively prevented, leading to a considerably increased interlayer spacing. Accelerated diffusion of electrolyte ions enables more electroactive sites to become accessible. The freestanding MXene/rGO-5 wt% electrode displays a volumetric capacitance of 1040 F cm−3 at a scan rate of 2 mV s−1 , an impressive rate capability with 61% capacitance retention at 1 V s−1 and long cycle life. Moreover, the fabricated binder-free symmetric supercapacitor shows an ultrahigh volumetric energy density of 32.6 Wh L−1, which is among the highest values reported for carbon and MXene based materials in aqueous electrolytes. This work provides fundamental insight into the effect of interlayer spacing on the electrochemical performance of 2D hybrid materials and sheds light on the design of next-generation flexible, portable and highly integrated supercapacitors with high volumetric and rate performances. MXene/reduced graphene oxide (rGO) hybrid films are prepared through electrostatic self-assembly of negatively charged MXene nanosheets and positively charged rGO nanosheets. rGO nanosheets are inserted in between MXene layers as conductive spacers, efficiently alleviating the self-restacking of both rGO and MXene. As a result, the hybrid films exhibit ultrahigh volumetric capacitance and an impressive rate capability.

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

DOI: 10.1002/adfm.201701264

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