instance, lithium-ion hybrid capacitors (LIHCs) consisting of an activated carbon (AC) cathode and a prelithiated graphite anode have been successfully commercialized and widely applied in small portable electronics. [2a] Nevertheless, the limited reserves and high cost of Li resources likely hinder them from applying in large-scale energy storage devices. As a new class of hybrid capacitors, potassium-ion hybrid capacitors (PIHCs) show great potential as alternative to LIHCs due to the profusion and low cost of potassium resources. [3] In addition, the redox potential of the K + /K (−2.936 V vs standard hydrogen electrode) is quite close to that of Li + /Li (−3.040 V), indicating PIHCs can afford a considerably high working voltage and energy density. [4] Unfortunately, the relatively large radius of K + (1.38 Å) tends to behave sluggish redox reaction kinetics for most of potassium-ion batteries (PIBs) anodes.As compared to LIHCs, the research regarding PIHCs is still in its infant stage and thus calls for extensive exploration on newly favorable electrode materials, in the hope to enhance the kinetics of K + insertion/extraction so that it can match with the fast kinetics of capacitor-style cathodes. To date, various electrode materials, such as carbonaceous materials, [5] metal alloys, [6] oxides, [7] sulfides, [8] and MXene, [9] have been extensively studied as battery-type anodes. Among them, carbon-based material, thanks to the merits of abundant resources, low cost, and high conductivity, has been regarded as one of the most promising electrode materials for the practical application of PIHCs. [10] However, the implementation of carbon-based electrode material for high-performance PIBs requires high conductivity and a rather large interlayer spacing for facilitating insertion and extraction of bulky K + and improving the redox reaction Kinetics. Therefore, it still remains a grand challenge to address the major issues existed in carbon-based anodes, including limited reversible capacities, unsatisfactory cycling stability, and poor rate performance, which result from the large volume change (61% caused by KC 8 vs 10% by LiC 6 ). [5] Heteroatom-doped carbonbased materials have exhibited the enhanced electrochemical properties for potassium-ion storage due to the increased electric conductivity and more active sites for potassium-ion storage by generating extrinsic defects. [11] In comparison with nitrogen, sulfur has a relatively large size but small electronegativity, Potassium-ion hybrid capacitors (PIHCs) hold the advantages of high-energy density of batteries and high-power output of supercapacitors and thus present great promise for the next generation of electrochemical energy storage devices. One of the most crucial tasks for developing a highperformance PIHCs is to explore a favorable anode material with capability to balance the kinetics mismatch between battery-type anodes and capacitortype cathode. Herein, a reliable route for fabricating sulfur and nitrogen codoped 3D porous carbon nanosheets...

Hierarchical porous carbon nanofibers can efficiently eliminate kinetics and capacity mismatches between the anode and cathode of the potassium-ion hybrid capacitor.