Thickness-independent capacitance of vertically aligned liquid-crystalline MXenes

Free-standing and flexible sandwich-like MXene/carbon nanotube (CNT) paper, composed of alternating MXene and CNT layers, is fabricated using a simple filtration method. These sandwich-like papers exhibit high volumetric capacitances, good rate performances, and excellent cycling stability when employed as electrodes in supercapacitors.

Electrical energy storage plays a vital role in daily life due to our dependence on numerous portable electronic devices. Moreover, with the continued miniaturization of electronics, integration of wireless devices into our homes and clothes and the widely anticipated ‘Internet of Things', there are intensive efforts to develop miniature yet powerful electrical energy storage devices. This review addresses the cutting edge of electrical energy storage technology, outlining approaches to overcome current limitations and providing future research directions towards the next generation of electrical energy storage devices whose characteristics represent a true hybridization of batteries and electrochemical capacitors.