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Rechargeable aqueous zinc-ion batteries have attracted extensive interest owing to their low cost and high safety. Herein, oxygen-defective potassium vanadate/amorphous carbon nanoribbons (C-KVO|O d) is successfully synthesized through a one-step solid-state sintering process as a high performance cathode material for zinc-ion batteries. This unique 3D interconnected network structure can not only act as continuous conductive path, but also decreases aggregation and provide more adsorption sites for zinc ions. The as-prepared C-KVO|O d exhibites a high capacity of 385 mAh g-1 at 0.2 A g-1 , superior rate performance (166 mAh g-1 even at 20 A g-1) and an outstanding cycling stability with a 95% capacity retention over 1000 cycles. Density functional theory calculations elucidated that the oxygen defects in the C-KVO|O d remarkably reduced Zn 2+ ion adsorption Gibbs free energy and Zn 2+-diffusion barriers. Meanwhile, the amorphous carbon networks enable the rapid electron transfer and provide additional active sites for Zn 2+ storage. This work could facilitate the development of high-performance zinc-ion batteries for large-scale energy storage.

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Silicon has been regarded as an attractive high-capacity anode material for next-generation lithium-ion batteries (LIBs). However, Si anodes suffer from huge volume variation during cycling, which poses a critical challenge for stable battery operation. Compared with Si, Si suboxide (SiO x ) is one of the most promising candidates for high-energy-density LIBs because of its alleviated swelling and highly stable cycling performance. Whereas, the poor electronic conductivity and low (initial) Coulombic efficiency of SiO x anodes severely hinder practical applications for LIBs. Herein, for the first time, these issues are successfully solved through rationally designing hollow-structured SiO x @carbon nanotubes (CNTs)/C architectures with graphitic carbon coatings and in situ growth of CNTs. When applied as anodes in LIBs, the SiO x @CNTs/C anodes exhibit high reversible capacity, high initial Coulombic efficiency (88%), outstanding cycling performance, and extraordinary mechanical strength during the calendaring process (200 MPa). This work paves the way for developing SiO x -based anode materials for high-energy-density LIBs.

Lithium cathode materials have been considered as promising candidates for energy storage applications because of their high power/energy densities, low cost, and low toxicity. However, the Li/Ni cation mixing limits their application as practical electrode materials. The cation mixing of lithium transition-metal oxides, which was first considered only as the origin of performance degeneration, has recently been reconsidered as a way to stabilize the structure of active materials. Here we find that as the duration of the post-synthesis thermal treatment (at 500 °C) of LiNiCoMnO (NCM) was increased, the Li/Ni molar ratio in the final product was found to decrease, and this was attributed to the reduction in nickel occupying lithium sites; the cation mixing subtly changed; and those subtle variations remarkably influence their cycling performance. The cathode material with appropriate cation mixing exhibits a much slower voltage decay and capacity fade during long-term cycling. Combining X-ray diffraction, Rietveld analysis, the Fourier transform infrared technique, field-emission scanning electron microscopy, and electrochemical measurements, we demonstrate that an optimal degree of Ni occupancy in the lithium layer enhances the electrochemical performance of layered NMC materials and that this occurs through a "pillaring" effect. The results provide new insights into "cation mixing" as a new concept for material design utilization of layered cathodes for lithium-ion batteries, thereby promoting their further application in lithium-ion batteries with new functions and properties.