A Trifunctional Hydroxylated Borophene‐Mediated MXene Enabled Super‐Stable and Fast‐Kinetics Interface Storage

Abstract The high electronic conductivity and tailorable structural properties of MXene materials make them promising candidates for energy storage. However, their poor chemical instability and self‐stacking effect greatly limit their application, especially in aqueous systems. Here, using a eutectic etching approach, hydroxylated borophene is used as a trifunctional mediator to construct robust Ti 3 C 2 T x ‐based MXene/B self‐assembled film electrodes for zinc‐ion capacitors (ZICs). Due to this mediator, the as‐formed strong interfacial binding within the heterostructure can give rise to an integrated modification effect and promote high‐efficiency interface energy storage. One is to strengthen the thermodynamic stability of local Ti─O bonds and inhibit the irreversible degradation of MXene; two is to enlarge the interface space of the MXene electrode and boost the ion transport; three is to improve the interfacial Zn 2+ trapping ability without affecting Zn 2+ migration on the MXene surface. Thus, the MXene/B electrode exhibits a high areal capacitance (537.9 mF cm −2 ) at a current density of 0.2 mA cm −2 and an extraordinary cycling stability at 1 mA cm −2 , with 99.64% retention after 40 000 cycles, which far surpasses that of most previous reports. This work provides a pathway for overcoming the interface storage limit of MXene electrodes to construct high‐performance ZICs.