Sodium‐ion batteries (SIBs) have gained tremendous interest for grid scale energy storage system and power energy batteries. However, the current researches of anode for SIBs still face the critical issues of low areal capacity, limited cycle life, and low initial coulombic efficiency for practical application perspective. To solve this issue, a kind of hierarchical 3D carbon‐networks/Fe7S8/graphene (CFG) is designed and synthesized as freestanding anode, which is constructed with Fe7S8 microparticles well‐welded on 3D‐crosslinked carbon‐networks and embedded in highly conductive graphene film, via a facile and scalable synthetic method. The as‐prepared freestanding electrode CFG represents high areal capacity (2.12 mAh cm−2 at 0.25 mA cm−2) and excellent cycle stability of 5000 cycles (0.0095% capacity decay per cycle). The assembled all‐flexible sodium‐ion battery delivers remarkable performance (high areal capacity of 1.42 mAh cm−2 at 0.3 mA cm−2 and superior energy density of 144 Wh kg−1), which are very close to the requirement of practical application. This work not only enlightens the material design and electrode engineering, but also provides a new kind of freestanding high energy density anode with great potential application prospective for SIBs.

A novel method to adjust the composition of a material while maintaining its morphology was described in this study. Nickel sulfide, the material investigated in this work, was found to be useful as a high surface area electrode material for supercapacitor applications. First, a nest-like Ni 3 S 2 @NiS composite electrode with 1D nanorod as structural unit was synthesized by simultaneously using Ni foam as template and Ni as a source through a one-step in situ growth method. Co and Se ions, which respectively acted as beneficial cation and anion, were successfully introduced into the nest-like Ni 3 S 2 @NiS material, resulting in the formation of Ni 3 S 2 @Co 9 S 8 and NiS@NiSe 2 composite electrodes with structures similar to those of the parent materials. The material structure was virtually retained and single-crystal-to-single-crystal transformation was achieved in the process. Introducing the cation and anion into the same type of material while maintaining topology could be important for the field of material synthesis and preparation of supercapacitor electrodes. Moreover, the electrochemical properties of these three materials were studied by cyclic voltammetry measurements and galvanostatic charge−discharge tests. The results indicated that the rate performance was improved significantly by ion exchange. In particular, the derived electrode with Se still showed superior oxidation and reduction ability at high scan rate of 10000 mV s −1 . In addition, the second charge−discharge specific capacity also increased from 516 F g −1 to 925 F g −1 and 1412 F g −1 at the current density of 0.5 A g −1 and by Co and Se exchange, respectively. This work contributes to the knowledge on electrode materials for supercapacitors and can provide good reference for the fabrication of desired materials.

High‐energy batteries with low cost are urgently needed in the field of large‐scale energy storage, such as grid systems and renewable energy sources. Sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs) with alloy‐based anodes provide huge potential due to their earth abundance, high capacity, and suitable working potential, and are recognized as attractive alternatives for next‐generation batteries system. Although some important breakthroughs have been reported, more significant improvements are still required for long lifetime and high energy density. Herein, the latest progress for alloy‐based anodes for SIBs and PIBs is summarized, mainly including Sn, Sb, Ge, Bi, Si, P, and their oxides, sulfides, selenides, and phosphides. Specifically, the material designs for the desired Na+/K+ storage performance, phase transform, ionic/electronic transport kinetics, and specific chemical interactions are discussed. Typical structural features and research strategies of alloy‐based anodes, which are used to facilitate processes in battery development for SIBs and PIBs, are also summarized. The perspective of future research of SIBs and PIBs is outlined.

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High initial coulombic efficiency is highly desired because it implies effective interface construction and few electrolyte consumption, indicating enhanced batteries life and power output. In this work, ah igh-capacity sodium storage material with FeS 2 nanoclusters ( % 1-2 nm) embedded in N, Sdoped carbon matrix (FeS 2 /N,S-C) was synthesized, the surface of which displays defects-repaired characteristic and detectable dot-matrix distributed Fe-N-C/Fe-S-C bonds.A fter the initial discharging process,t he uniform ultra-thin NaF-rich ( % 6.0 nm) solid electrolyte interphase was obtained, thereby achieving verifiable ultra-high initial coulombic efficiency ( % 92 %). The defects-repaired surface provides perfect platform, and the catalysis of dot-matrix distributed Fe-N-C/Fe-S-Cb onds to the rapid decomposing of NaSO 3 CF 3 and diethylene glycol dimethyl ether successfully accelerate the building of two-dimensional ultra-thin solid electrolyte interphase.D FT calculations further confirmed the catalysis mechanism. As ar esult, the constructed FeS 2 /N,S-C provides high reversible capacity (749.6 mAh g À1 at 0.1 Ag À1 )a nd outstanding cycle stability (92.7 %, 10 000 cycles,1 0.0 Ag À1 ). Especially,a tÀ15 8 8C, it also obtains ar eversible capacity of 211.7 mAh g À1 at 10.0 Ag À1 .A ssembled pouch-type cell performs potential application. The insight in this work provides abright way to interface design for performance improvement in batteries.