Boosting the Pseudocapacitive and High Mass‐Loaded Lithium/Sodium Storage through Bonding Polyoxometalate Nanoparticles on MXene Nanosheets

Abstract Achieving rate‐capable and high mass‐loaded lithium/sodium storage plays a pivotal role in promoting real world applications of many emerging electrode materials. Herein, such an electrode material is reported made of Mo and Fe‐based polyoxometalates firmly bonded on MXene nanosheets through a mild in situ growth procedure. The polyoxometalate nanoparticles can efficiently prevent the restacking of the MXene nanosheets, enabling an electrolyte‐permeable architecture at high mass loadings while the metallic conductivity of MXenes allows rapid electron transfer contributing to the full exploration of the rich redox capability of polyoxometalates even at high rates. The optimal structure delivers a high capacity of 297 and 191 mA h g –1 at 1.0 A g –1 for lithium and sodium storage, respectively, even after a thousand of cycles. The kinetic analysis suggests high capacitive contributions of 81.6% and 67.4% for lithium and sodium uptake/release at 1.0 mV s –1 , respectively. Moreover, a decent capacity remains even after 13.5‐fold increase of loading mass. The lithium/sodium‐ion hybrid supercapacitors based on this composite deliver remarkable energy density and power capability. The results demonstrated in this work may offer an alternative selection of electrodes based on rationally designed polyoxometalates and MXenes.