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Fe2O3 with high theoretical capacity (1007 mA h g−1) and low cost is a potential anode material for lithium‐ion batteries (LIBs), but its practical application is restricted by its low electrical conductivity and large volume changes during lithiation/delithiation. To solve these problems, Fe2O3@Ti3C2Tx composites were synthesized by a mussel‐like modification method, which relies on the self‐polymerization of dopamine under mild conditions. During polymerization, the electronegative group (−OH) on dopamine can easily coordinate with Fe3+ ions as well as form hydrogen bonds with the −OH terminal group on the surface of Ti3C2Tx, which induces a uniform distribution of Fe2O3 on the Ti3C2Tx surface and mitigates self‐accumulation of MXene nanosheets. In addition, the polydopamine‐derived carbon layer protects Ti3C2Tx from oxidation during the hydrothermal process, which can further improve the electrical conductivity of the composites and buffer the volume expansion and particle agglomeration of Fe2O3. As a result, Fe2O3@Ti3C2Tx anodes exhibit ~100 % capacity retention with almost no capacity loss at 0.5 A g−1 after 250 cycles, and a stable capacity of 430 mA h g−1 at 2 A g−1 after 500 cycles. The unique structural design of this work provides new ideas for the development of MXene‐based composites in energy storage applications. [ABSTRACT FROM AUTHOR]

Low Coulombic efficiency and significant capacity decay resulting from an unstable solid electrolyte interphase (SEI) and dendritic growth pose challenges to the practical application of lithium‐metal batteries. In this study, a highly efficient protection layer induced by octaphenylsilsesquioxane (OPS) with LiFSI salt is investigated. The OPS exhibits a strong adsorption energy with lithium, its multi‐site gradient adsorption ability enables the simultaneous capture of 8 Li+ and the uniform regulation of Li ion flux. Moreover, the mechanical strength and electronic insulation of the OPS layer induces Li deposition under the protection layer and effectively inhibits lithium dendrite growth. Such a protection layer contributes to the stable and dendrite‐free performance of a lithium‐metal battery employing LiNi0.8Co0.1Mn0.1O2 (NCM811) as a cathode and an ultrathin OPS‐protected lithium foil (20 µm) as the anode. A remarkable capacity retention of 91.4% is achieved after 300 cycles at 1C. The OPS‐protected Li anodes and NCM811 are also tested in combination with a Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte, showing extended cyclability up to 300 cycles with an average Coulombic efficiency of 99.58% and capacity retention of 85.7%. [ABSTRACT FROM AUTHOR]

Polythiophene-coated porous silicon core-shell nanospheres (Si@PTh) composite are synthesized by a simple chemical oxidative polymerization approach. The polythiophene acts as a flexible layer to hold silicon grains when they are repeatedly alloying/dealloying with lithium during the discharge/charge process. The long lifespan and high-current-density rate ­capability (at a current of 8 A g−1) of the Si@PTh composite are vastly improved compared with as-prepared Si spheres. Typically, these Si@PTh composite electrodes achieve a reversible capacity of 1130.5 mA h g−1 at 1 A g−1 current density after 500 cycles, and can even possess a discharge capacity up to 451.8 mA h g−1 at 8 A g−1. The improved electrochemical performance can be ascribed to the synergy effects of the flexible PTh coating and the distinctive core-shell nanospheres with porous structure, which can largely alleviate the volume expansion of the Si during alloying with lithium. [ABSTRACT FROM AUTHOR]

Lithium‐ion batteries (LIBs) with outstanding energy and power density have been extensively investigated in recent years, rendering them the most suitable energy storage technology for application in emerging markets such as electric vehicles and stationary storage. More recently, sodium, one of the most abundant elements on earth, exhibiting similar physicochemical properties as lithium, has been gaining increasing attention for the development of sodium‐ion batteries (SIBs) in order to address the concern about Li availability and cost—especially with regard to stationary applications for which size and volume of the battery are of less importance. Compared with traditional intercalation reactions, conversion reaction‐based transition metal oxides (TMOs) are prospective anode materials for rechargeable batteries thanks to their low cost and high gravimetric specific capacities. In this review, the recent progress and remaining challenges of conversion reactions for LIBs and SIBs are discussed, covering an overview about the different synthesis methods, morphological characteristics, as well as their electrochemical performance. Potential future research directions and a perspective toward the practical application of TMOs for electrochemical energy storage are also provided. [ABSTRACT FROM AUTHOR]