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Two-dimensional materials have been considered as novel anode materials for LIBs because of their large surface area, small volume change, and low Li diffusion barrier. Among them, the two-dimensional material SixGey has many excellent properties as an anode. However, Ge is expensive and not suitable for mass production. Therefore, proper Ge doping is of great significance to improve performance and reduce cost. Herein, we systematically study the effect of Ge doping and its concentration on the structure and electrochemical performance of two-dimensional SixGey by density functional theory (DFT) calculations. The incorporation of low concentration Ge can improve the horizontal and vertical diffusion ability of Li atoms compared to silicene. However, excessive Ge will increase the horizontal diffusion energy barrier of Li and reduce the theoretical capacity, where Si6Ge2 has a relatively high theoretical capacity and a low diffusion energy barrier. In addition, fully lithiated 2D SixGey shows poor electrical conductivity and increasing Ge concentration seems to be effective in improving the electrical conductivity of the material. This study will provide significant theoretical guidance for the design and preparation of two-dimensional silicon-based materials. [ABSTRACT FROM AUTHOR]

Potassium-ion batteries (PIBs) are promising as a low-cost and complementary technology to lithium-ion batteries (LIBs) because of the relative abundance of potassium. Electrolyte is a critical component and governs the electrochemical performance of PIBs. Electrolyte engineering has recently resulted in promising results for both the anode and cathode materials of PIBs. However, the performance of current PIBs is still limited for practical applications. A systematic analysis of recent electrolyte engineering research is required for further improvement. In this review, we first summarize the recent electrolyte research progress and design strategies for PIBs. We then discuss the key features of PIB electrolytes such as the K-ion solvation environment and SEI chemistry, and finally propose several design strategies and considerations for future electrolyte development. [ABSTRACT FROM AUTHOR]

Conversion/alloying materials with high theoretical capacity are promising for potassium-ion batteries, although their development is seriously blocked owing to their volume expansion and ineffective solid-electrolyte interphase (SEI) protection. Herein, it is discovered that the performance of the CoSe anode material could be enhanced through a flexibly designed core–shell structure (denoted as CoSe–C@C) and an inorganic compound-rich SEI. The CoSe–C@C electrode exhibits stable cycling performance (432 mA h g−1 at 200 mA g−1) over 1000 cycles and outstanding rate capability (233 mA h g−1 at 10 A g−1). A reversible conversion mechanism for the potassiation/depotassiation in CoSe is revealed by ex situ X-ray diffraction patterns and high-resolution transmission electron microscope images, while the SEI on the CoSe–C@C surface is found to be inorganic-rich (KF-), which is favourable for K ion diffusion and charge transfer dynamics. These findings would shed light on nanostructure design strategies and our fundamental understanding of the SEI formation in electrolyte engineering for potassium-ion batteries. [ABSTRACT FROM AUTHOR]

In order to better resolve the large volume expansion problem of SnO2-based anode materials, a hollow bean-pod-like SiO2-supported-SnO2/C nanostructure with a sufficient internal void space is designed. Dual voids exist in this structure in combination with a SiO2 support in the core and carbon as an outside shell, providing triple guarantees to improve the performance of SnO2-based anode materials for Li and Na storage. As a result, after 550 charge/discharge cycles, a discharge capacity of 649 mA h g−1 can still be obtained for Li storage, and a discharge capacity of 104 mA h g−1 can still be maintained after 1000 charge/discharge cycles for Na storage. [ABSTRACT FROM AUTHOR]

Flexible batteries have attracted much attention in recent years due to their promising applications in flexible displays, portable consumer electronic devices, and thin-film-based electronics. However, their practical applications are still limited by their low active material mass-loading in flexible electrodes and poor lithium storage performances. In this work, we have successfully grown highly crystalline VO2 nanobelt arrays on carbon fiber cloth (CFC) for the first time. The strategy only involves a facile one-pot solvothermal method. As binder-free flexible electrodes for LIBs, even with active material mass loading dramatically reaching up to 5.2 mg per square centimeter, such a novel CFC@VO2 (B) nanobelt array cathode electrode still exhibits a specific capacity of 145 mA h g−1 (90% of theoretical capacity), excellent cyclability with capacity retention over 90% after 200 cycles at ∼9C (1000 mA g−1), and high rate capability at high current densities up to ∼20C (2000 mA g−1). Such an excellent cathode material is very desirable in high-power flexible LIBs. The effective combination of CFC and a high areal mass loading of active materials described in this paper is a feasible and effective solution to design high-performance flexible batteries, especially high-power flexible batteries. [ABSTRACT FROM AUTHOR]