Boostinggravimetric and volumetric energy density via engineering macroporousMXene films for supercapacitors

MengyaoYao^*,Yaoyan Chen, Zhe Wang, Chengmin Shao, Jie Dong, Qinghua Zhang, LiliZhang, Xin Zhao^*

ChemicalEngineering Journal, 2020, 124057, 1385-8947.

https://doi.org/10.1016/j.cej.2020.124057

Thenew family of 2D MXene materials has garnered considerable interestfor future energy storage. However, the sluggish ionic kineticswithin the compact and dense MXene films are still the fundamentallimitation to their electrochemical performance. Here, flexible andfree-standing macroporous MXene thin films were fabricated by afacile strategy of incorporating polystyrene (PS) microspheres ofvarious sizes as soft sacrificial templates, followed by calcination.The obtained material possesses high macroporosity withthree-dimensional interconnected porous channels to promote electrontransport within the electrode and to facilitate electrolyteaccessibility without significantly affecting the density of theMXene films. Through appropriate engineering design and optimization,the modified macroporous MXene films could not only achieve a highgravimetric capacitance of 506 F g⁻¹and a volumetric value of 759 F cm⁻³at a current density of 0.5 A g⁻¹,but also delivers a satisfactory gravimetric capacitance of 380 F g⁻¹under a high current density of 20 A g⁻¹.Furthermore, the assembled symmetric supercapacitor demonstrates agravimetric energy density of 9.65 Wh kg⁻¹and a volumetric energy density of 15.1 Wh L⁻¹at a power density of 67.5 W L⁻¹,illustrating its great potential as a flexible electrode forhigh-performance supercapacitors.