Boosting gravimetric and volumetric energy density via engineering macroporous MXene films for supercapacitors

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