Owing to the lower price and higher safety, developing high‐performance K‐ion batteries (KIBs) is of great significance as an alternative to Li‐ion batteries. High‐energy‐density MoSe2 has been identified as a promising anode material for KIBs; however, its electrochemical reversibility remains a big challenge. Herein, heterogenous MoSe2/N‐doped carbon nanoarrays demonstrate a brilliant performance as KIBs anode materials. The as‐formed hetero‐interface weakens the KSe bond of discharged products (K2Se), the length of KSe bond is stretched by 3.9% with an enlargement of 19.2% in angle compared with pure K2Se, greatly promoting the regeneration of MoSe bond during charge. Moreover, the atomically inter‐overlapping feature leads to an expanded MoSe2 interlayer distance of 1.20 nm that enables a much faster K‐ion diffusion. Consequently, this nanoarray delivers an unprecedented K‐ion storage performance, that is, a capacity of 402 mAh g−1 at 0.2 A g−1 over 200 cycles, and a long cycle life over 1000 cycles at 1.0 A g−1 with 307 mAh g−1 capacity retention.

The earth‐abundant hard carbons have drawn great concentration as potassium‐ion batteries (KIBs) anode materials because of their richer K‐storage sites and wider interlayer distance versus graphite, but suffer from a low electrochemical reversibility. Herein, the novel Se/N co‐doped hard‐carbon nanotubes (h‐CNTs) with localized electron configuration are demonstrated by creating unique NSeC covalent bonds stemmed from the precise doping of Se atoms into carbon edges and the subsequent bonding with pyrrole‐N. The strong electron‐donating ability of Se atoms on d‐orbital provides abundant free electrons to effectively relieve charge polarization of pyrrole‐N‐C bonds, which contributes to balance the K‐ion adsorption/desorption, therefore greatly boosting reversible K‐ion storage capacity. After filtering into self‐standing anodes with weights of 1.5–12.4 mg cm−2, all of them deliver a high reversible gravimetric capacity of 341 ± 4 mAh g−1 at 0.2 A g−1 and a linear increasing areal capacity to 4.06 mAh cm−2. The self‐standing anode can still maintain 209 mAh g−1 at 8.0 A g−1 (93.3% retention) for a long period of 2000 cycles with a constant Se/N content.

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Lithium-sulfur batteries (LSBs) have become one of the most competitive candidates for next generation energy storage systems due to the high theoretical energy density, nevertheless, the severe shuttle effect, volume expansion, and poor electrical conductivity restrict their practical application. Herein, we report a synergistic combination of 3D carbon matrix (CdS@NG-CNT) composed of low-defect carbon nanotubes (CNTs) and nitrogen-doped graphene (NG) decorated with low loading of cadmium sulfide quantum dots as sulfur host and carbon black (CB) as separator layer to collectively solve these issues. Specifically, the developed host material possesses abundant macropores and mesopores and high electrical conductivity, which endow the carbon matrix multifaceted structural properties for polysulfides immobilization, electrons/ Li + transfer, and Li 2 S formation, as well as buffering the volume expansion during cycling. The CB-modified separator can help to enhance the interconversion of intercepted polysulfides. Benefiting from these aspects, the cell equipped with CdS@NG-CNT/S//CB-PP exhibits a superior rate capacity of 1493.6 mA h/g at 0.2 C (1 st ), and maintains a capacity of 479.7 mA h/g after 1050 cycles with an ultralow capacity decay rate of 0.051 % at 1.0 C. This work provides a useful strategy to solve issues of the current LSBs, which may practically be used in the high-energy density.