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For lithium-ion capacitors, electrode potential tuning has been widely regarded as an efficient technology to improve their performance where the anode is usually pre-lithiated for desired potentials. However, the attention on the cathode is quite rare which denies the further excavation of this promising strategy. Herein, we reported the precious regulation of the potential of a cathode made of nitrogen-doped carbon nanosheets to fully leverage the merit of the electrode materials and the electrolyte potential window. Specifically, the nitrogen-doped carbon nanosheets in the optimized potential range of 1.6–4.5 V vs Li/Li+ show a specific capacity of around 150 mA h g−1 at 0.2 A g−1, which is four-time higher than that of the typical activated carbon cathode without potential tuning, and could be stably cycled for over 10 000 cycles without obvious decay. After pairing with a pre-lithiated anode, the as-assembled lithium-ion capacitors based on such a cathode can lead to simultaneously optimize the specific capacitance and voltage window of the device that contributes to a 17-fold increase in energy density, large power density, and long-term stability. The simple and effective strategy demonstrated here may inspire an alternative avenue to regulate the real performance of hybrid energy storage devices. The elaborately regulated carbon cathode is capable of working in a reasonable potential window for stably delivering a large specific capacity. After carefully pairing with the pre-lithiated anode, the device based on these electrodes exhibits high energy, large power, and long cyclic life. [Display omitted] [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]