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Lithium metal batteries (LMBs) with extremely high energy densities have several advantages among energy storage equipment. However, the uncontrolled growth of dendrites and the flammable liquid electrolytes (LEs) often cause safety accidents. All solid‐state batteries seem to be the ultimate choice, but solvent‐free electrolytes usually fail in terms of conductivity at room temperature. Therefore, gel polymer electrolytes (GPEs) with a simple manufacturing process and high ionic conductivity are considered as the most competitive candidates to resolve the present difficulties. Herein, we design a polymeric network structure via esterification and amidation reactions between polyethylene glycol (PEG) and carbon dots (CDs). After incorporation with polyvinylidene fluoride and some LEs, the as‐prepared PEG–CDs composite electrolytes (PCCEs) show a high ionic conductivity of 5.5 mS/cm and an ion transference number of 0.71 at room temperature, as well as good flexibility and thermostability. When the PCCEs are assembled with lithium metal anodes and LiFePO4 or LiCoO2 cathodes, both the cycling stability and the retention rate of these LMBs show excellent performance at room temperature. [ABSTRACT FROM AUTHOR]

Mn3O4 is a promising cathode material for aqueous zinc ion batteries (ZIBs) which is a new type of low cost, eco‐friendly, high security energy storage system, while those previously reported electrochemical capacities of Mn3O4 are far from its theoretical value. In this work, Mn3O4 nanoparticles and nitrogen‐doped carbon dots (NCDs) are synthesized together through an in‐situ hydrothermal route, and then calcined to be a nanocomposite in which Mn3O4 nanoparticles are anchored on a nitrogen‐doped carbon skeleton (designated as Mn3O4/NCDs). Although the carbon content is only 3.9 wt.% in the Mn3O4/NCDs, the NCDs‐derived carbon skeleton provides an electrically conductive network and a stable structure. Such a special nanocomposite has a large specific surface area, plenty of active sites, excellent hydrophilicity and good electronic conductivity. Owing to these structural merits, the Mn3O4/NCDs electrode exhibits a preeminent specific capacity of 443.6 mAh g−1 and 123.3 mAh g−1 at current densities of 0.1 and 1.5 A g−1 in ZIBs, respectively, which are far beyond the bare Mn3O4 nanoparticles synthesized under the similar condition. The electrochemical measurement results prove that carbon dots, as a new type of carbon nanomaterials, have strong ability to modify and improve the performance of existing electrode materials, which may push these electrode materials forward to practical applications. [ABSTRACT FROM AUTHOR]

Lithium‐ion battery (LIB) is a dominating power source in the market owing to its high energy density, good cycling stability and environmental benignity. However, technical challenges remain after years' optimization and commercialization, which are detrimental to the expected performance and lifespan of LIBs. For instance, many cathode materials of LIBs suffer from rapid capacity fading and poor high‐rate performance, which are ascribed to self‐aggregation, dissolution and fast increased charge transfer resistances during cycles. In terms of the anode materials, low coulombic efficiency, electrolyte depletion and safety issues are common. In addition, the liquid electrolyte systems trigger safety concerns because flammable and volatile organic solvents are necessary. Recently, carbon dots (CDs) emerge as a sound material to address those challenges of LIBs, and also present promising applications in bioimaging, fluorescence sensing, photo/electro‐catalysis, and electroluminescence. This review will overlook the state‐of‐the‐art advances in the employment of CDs based composites to build cathode/anode materials and electrolytes in LIBs, through tailoring the internal structures and the surface states of electrode materials, and being additives in electrolyte, to improve the performances of the next‐generation LIBs. The major challenges and opportunities in front of CDs in LIBs will be outlined and discussed in detail. [ABSTRACT FROM AUTHOR]