Fabrication of 3D MXene@graphene hydrogel with high ion accessibility via Al-induced self-assembly and reduction for high-performance supercapacitors

MXene nanosheets are one of the most promising supercapacitor electrode materials due to their excellent conductivity and redox activity. However, the balance of high capacity and rate performance of MXene nanosheets are still a big challenge due to their easy re-stacking, especially with a high mass loading. Here, the 3D MXene@graphene (MXene@rGO) hydrogel with high ion accessibility is engineered by Al-induced self-assembly of MXene and GO nanosheets. Trace acid solution is used as the initiator to etch the blunted aluminum oxide layer and release the Al3+ ions, which acts as the linker to assemble nanosheets into 3D structure. At the same time, the mechanical strength of the hydrogel is further enhanced via the reduction of GO induced by Al. The MXene@rGO hydrogel exhibits a maximum area capacitance of 4.33 F cm−2 at 10 mA cm−2 and maintains a high area capacitance of 1.76 F cm−2 at 1000 mA cm−2, indicating the high capacitance retention of 40.6%. Remarkably, the constructed asymmetric supercapacitor shows a high cyclic stability with a mere 8.37% decrease after 100,000 cycles, indicating the excellent application prospect.