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Hard carbon is considered as the most promising anode material for potassium-ion energy storage devices. Substantial progress has been made in exploring advanced hard carbons to solve the issues of sluggish kinetics and large volume changes caused by the large radius of K+. However, the relationship between their complicated microstructures and the K+charge storage behavior is still not fully explored. Herein, a series of two-dimensional mesoporous carbon microcoins (2D-MCMs) with tunable microstructures in heteroatom content and graphitization degree are synthesized by a facile hard-template method and follow a temperature-controllable annealing process. It is found that high heteroatom content makes for surface-driven K+storage behavior, which increases the capacity-contribution ratio from a high potential region, while a high graphitization degree makes for K+intercalation behavior, which increases the capacity-contribution ratio from a low potential region. Electrochemical results from a three-electrode Swagelok cell demonstrate that a 2D-MCM anode with more capacity contribution from a low working region allows the porous carbon cathode to be operated in a much wider electrochemical window, thus storing more charge. As a result, potassium-ion capacitors based on the optimized 2D-MCM anode deliver a high energy density of 113 Wh kg–1and an exhilarating power density of 51,000 W kg–1.

Taking into consideration the advantages of the highly theoretical capacity of antimony (Sb) and abundant surface redox reaction sites of Na+pre-intercalated 3D porous Ti3C2Tx(Na–Ti3C2Tx) architectures, we elaborately designed the Sb/Na–Ti3C2Txhybrid with Sb nanoparticles homogeneously distributed in 3D porous Na–Ti3C2Txarchitectures through a facile electrostatic attraction and carbothermic reduction process. Na–Ti3C2Txarchitectures with more open structures and larger active specific surface area not only could certainly alleviate volume changes and hinder the aggregation of Sb nanoparticles in the cycling process to improve the structural stability but also significantly strengthen the electron-transfer kinetics and provide unblocked K+diffusion channels to promote ionic/electronic transport rate. Furthermore, the ultrafine Sb nanoparticles could efficiently shorten K+transport distance and expose more accessible active sites to improve capacity utilization. DFT calculations further indicate that the Sb/Na–Ti3C2Txanode effectively decreases the adsorption energy of K+and accelerates the potassiation process. Benefiting from the synergistic effect, it exhibits an outstanding specific capacity of 392.2 mAh g–1at 0.1 A g–1after 450 cycles and a stable capacity reservation with a capacity fading rate of 0.03% per cycle at 0.5 A g–1. Our work may encourage further research on advanced MXene-based hybrid materials for high-performance PIBs.