Flexible MXene/holey graphene films as multifunctional electrodes for high-performance energy storage and pressure sensing

Abstract

Two-dimensional MXenes are promising electrodes for high-rate electrochemical energy storage, yet severe restacking of nanosheets and sluggish through-thickness ion transport limit active-site utilization, particularly in practical thick films. Here, we report a freestanding Ti₃CNT_x/reduced holey graphene oxide (rHGO) composite film with a sandwich-like lamellar architecture fabricated by vacuum-assisted filtration and thermal annealing. Holey rHGO acts as an efficient spacer to enlarge the Ti₃CNT_x interlayer galleries and, critically, its intrinsic nanopores provide direct through-plane ion transport pathways that shorten diffusion distances and reduce transport tortuosity. The optimized film delivers an ultrahigh volumetric capacitance of 1118 F cm⁻³ with excellent rate capability and improved performance retention at increased electrode thickness. In addition to energy storage, the same film exhibits stable piezoresistive sensing with rapid response, enabling multifunctional integration. This work demonstrates a simple structural design strategy that couples interlayer expansion with through-plane ionic highways to advance MXene-based thick-film electrodes for compact, high-performance microenergy and sensing systems.