Reassembly of MXene Hydrogels into Flexible Films towards Compact and Ultrafast Supercapacitors

• Published in: Advanced functional materials 2021-10, Vol.31 (41), p.n/a
• Main Authors: Wu, Zhitan, Liu, Xiaochen, Shang, Tongxin, Deng, Yaqian, Wang, Ning, Dong, Ximan, Zhao, Juan, Chen, Derong, Tao, Ying, Yang, Quan‐Hong
• Format: Article
• Language: English
• Subjects: Aqueous electrolytes; Energy storage; Flux density; Hydrogels; Ion transport; Mass ratios; Materials science; Microgels; Morphology; MXenes; rate capability; reassembly strategy; Supercapacitors; volumetric capacitance
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202102874

The freestanding MXene films are promising for compact energy storage ascribing to their high pseudocapacitance and density, yet the sluggish ion transport caused by the most densely packed structure severely hinders their rate capability. Here, a reassembly strategy for constructing freestanding and flexible MXene‐based film electrodes with a tunable porous structure is proposed, where the Ti3C2Tx microgels disassembled from 3D structured hydrogel are reassembled together with individual Ti3C2Tx nanosheets in different mass ratios to form a densely packed 3D network in microscale and a film morphology in macroscale. The space utilization of produced film can be maximized by a good balance of the density and porosity, resulting in a high volumetric capacitance of 736 F cm−3 at an ultrahigh scan rate of 2000 mV s−1. The fabricated supercapacitor yields a superior energy density of 40 Wh L−1 at a power density of 0.83 kW L−1, and an energy density of 21 Wh L−1 can be still maintained even when the power density reaches 41.5 kW L−1, which are the highest values reported to date for symmetric supercapacitors in aqueous electrolytes. More promisingly, the reassembled films can be used as electrodes of flexible supercapacitors, showing excellent flexibility and integrability. A reassembly strategy for producing a flexible MXene‐based electrode with tunable porosity is proposed, in which the volumetric capacitance under ultrahigh rate is maximized by balancing the density and porosity. The assembled symmetric device delivers the highest energy density of 40 Wh L−1 and the highest power density of 41.5 kW L−1.