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

Ti 3 C 2 T x (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 Ti 3 C 2 T x nanosheets largely decreases exposed area and impedes the ion transport in Ti 3 C 2 T x film. Herein, hierarchically porous carbon (HPC) introduced into Ti 3 C 2 T x film can not only act as the pillar for adjacent Ti 3 C 2 T x 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 μW h cm −2  at 19.91 μW 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 Ti 3 C 2 T x film by constructing transverse and longitudinal channels for rapid ion transport.