Among the negative electrode materials for potassium ion batteries, carbon is very promising because of its low cost and environmental benignity. However, the relatively low storage capacity and sluggish kinetics still hinder its practical application. Herein, a large scalable sulfur/nitrogen dual‐doped hard carbon is prepared via a facile pyrolysis process with low‐cost sulfur and polyacrylonitrile as precursors. The dual‐doped hard carbon exhibits hierarchical structure, abundant defects, and functional groups. The material delivers a high reversible potassium storage capacity and excellent rate performance. In particular, a high reversible capacity of 213.7 and 144.9 mA h g−1 can be retained over 500 cycles at 0.1 A g−1 and 1200 cycles at 3 A g−1, respectively, demonstrating remarkable cycle stability at both low and high rates, superior to the other carbon materials reported for potassium storage, to the best of the authors' knowledge. Structure and kinetics studies suggest that the dual‐doping enhances the potassium diffusion and storage, profiting from the formation of a hierarchical structure, introduction of defects, and generation of increased graphitic and pyridinic N sites. This study demonstrates that a facile and scalable pyrolysis strategy is effective to realize hierarchical structure design and heteroatom doping of carbon, to achieve excellent potassium storage performance.

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Lithium-ion batteries (LIBs) have changed modern life-enabling mobile communication and electric vehicles. They are the most widespread energy storage devices but they are not totally suitable for sustainable development due to the limited lithium resources in countries often with underlying political disputes. [3][4][5] As alternative candidates, sodium-ion batteries (SIBs) have drawn increasing attention by both academic and industrial communities on account of the high abundance of sodium resources. [6,7] Of great promise are inexpensive, high-energy, long-lifespan, and fast-charging SIBs in order to improve on LIBs. [8] However, a key bottleneck in commercializing SIBs is to identify competitive cathodes with long lifespan, negligible volume change, cost-effectiveness, as well as high capacity. [9][10][11] Until now, several families of cathode materials have been developed for use such as layered oxides, [12,13] Prussian blues analogs, [14] and polyanion oxides. [15][16][17] Among these, sodium superionic conductor (NASICON)-structured Na x MeMe′(PO 4 ) 3 (Me/Me′ refers to transition metals) are capable of satisfying the above requirements in terms of high ionic conductivity (3D open frameworks), limited volume change (strong Sodium super-ionic conductor (NASICON)-structured phosphates are emerging as rising stars as cathodes for sodium-ion batteries. However, they usually suffer from a relatively low capacity due to the limited activated redox couples and low intrinsic electronic conductivity. Herein, a reduced graphene oxide supported NASICON Na 3 Cr 0.5 V 1.5 (PO 4 ) 3 cathode (VC/C-G) is designed, which displays ultrafast (up to 50 C) and ultrastable (1 000 cycles at 20 C) Na + storage properties. The VC/C-G can reach a high energy density of ≈470 W h kg −1 at 0.2 C with a specific capacity of 176 mAh g −1 (equivalent to the theoretical value); this corresponds to a three-electron transfer reaction based on fully activated V 5+ /V 4+ , V 4+ /V 3+ , V 3+ /V 2+ couples. In situ X-ray diffraction (XRD) results disclose a combination of solid-solution reaction and biphasic reaction mechanisms upon cycling. Density functional theory calculations reveal a narrow forbiddenband gap of 1.41 eV and a low Na + diffusion energy barrier of 0.194 eV. Furthermore, VC/C-G shows excellent fast-charging performance by only taking ≈11 min to reach 80% state of charge. The work provides a widely applicable strategy for realizing multi-electron cathode design for high-performance SIBs.

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An acetylene black modified gel polymer electrolyte was prepared to simultaneously solve the problems of shuttle effect and lithium dendrite growth for high-performance Li–S batteries.

Low-cost supercapacitors with high energy densities have attracted great research attention, since it would broaden the application of capacitors. Increasing the capacitance is one principle to obtain a high energy density of a supercapacitor. In this study, a low cost aqueous Zn-based hybrid supercapacitor (AZHS) with high energy density is achieved using an actived carbon derived from corncob (denoted as ACC) as the positive electrode, zinc metal as the negative electrode, and the 2 M ZnSO 4 electrolyte. The actived carbon is prepared with a facile calcination-activation process, and it exhibits high specific surface area (2619 m 2 g −1 ). Though without extra heteroatom doping, ACC demonstrates a superb specific capacitance in acidic, alkaline and neutral electrolytes. The assembled AZHS exhibits a high energy density of 94 W h kg −1 at 68 W kg −1 in a potential window of 0.2−1.8 V, and an excellent cycle stability with only 1.8% capacitance decay is obtained after 10 000 cycles at 5 A g −1 . These results suggest that a low cost supercapacitor with high energy density can be achieved by a hybrid system design using electrodes with high capacitance.

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A proof-of-concept lithium ion capacitor comprising LiMn2O4 nanorods as the cathode, a nitrogen-rich biomass carbon anode and a stable alkaline–neutral electrolyte was designed and fabricated.