Porosity-adjustable MXene film with transverse and longitudinal ion channels for flexible supercapacitors

Ti3C2Tx (a typical MXene) films can be used as free-standing electrodes due to their ultrahigh electrical conductivity, well flexibility and high electrochemical activity. However, inevitable self-restacking issue of Ti3C2Tx nanosheets largely decreases exposed area and impedes the ion transport in Ti3C2Tx film. Herein, hierarchically porous carbon (HPC) introduced into Ti3C2Tx film can not only act as the pillar for adjacent Ti3C2Tx nanosheets to prevent their typical self-restacking and further accelerate rapid ion transport in the transverse direction, but also ensure rapid ion transport in the longitudinal direction by introducing abundant macro/mesopores. By easily changing the amount of HPC (0-60%), the porosity of the film is well controlled, with adjustable specific surface area (SSA) from 8 m(2) g(-1) to 755 m(2) g(-1). The prepared quasi-solid-state supercapacitor fabricated by 60% HPC shows a good stability after different bending angles, high capacitance of 211 mF cm(-2), energy density of 4.68 mu W h cm(-2) at 19.91 mu W cm(-2), and high capacitance retention of 86% after 10,000 charging-discharging cycles. This work will pave a facile route to alleviate the self-restacking phenomenon of Ti3C2Tx film by constructing transverse and longitudinal channels for rapid ion transport.