Oxygen vacancies enhance lithium storage performance in ultralong vanadium pentoxide nanobelt cathodes

MWCNT synergy for boosting the electrochemical kinetics of V2O5 cathode for lithium-ion batteries

V2O5/MWCNT hybrid system has been developed and investigated as cathode in LIBs. The developed electrode shows superior performance as compare to pristine V2O5 and V2O5/rGO hybrid structure due to the synergy between V2O5 and MWCNT.

Ultrafast and Stable Lithium Storage Enabled by the Electric Field Effect in Layer-Structured Tablet-Like NH4TiOF3 Mesocrystals

Design and synthesis of advanced electrode materials with fast and stable ion storage are of importance for energy storage applications. Herein, we propose that introducing the heterogeneous interface in layer-structured mesocrystals is an efficient way to greatly improve the rate capability and cycle stability of lithium-ion battery (LIB) devices. NH₄TiOF₃ mesocrystals were employed as a typical model system to demonstrate the idea. The NH₄TiOF₃ mesocrystals were obtained via the hydrothermal reaction, and the NH₄TiOF₃/TiO₂ interfaces were generated through calcining at different temperatures under an argon atmosphere. Phase composition, microstructure, and chemical analyses show that the as-prepared NH₄TiOF₃ mesocrystals possess "tablet-like" morphology, and the formation of the NH₄TiOF₃/TiO₂ interface can be controlled by the calcination temperature. When evaluated as the anode for LIBs, the optimized sample (NH₄TiOF₃ calcined at 250 °C, NTF-250) shows excellent, fast, and stable lithium storage properties. Specifically, the NTF-250 electrode holds a reversible capacity of 159.5 mA h g^-1 after 200 cycles at 0.2 A g^-1. At a high current density of 20 A g^-1, the electrode still maintains a reversible capacity of 89.6 mA h g^-1 and reaches a reversible capacity of 128.6 mA h g^-1 at a current density of 1 A g^-1 after 2000 cycles. Theoretical and experimental studies show that the synergistic effects of the heterogeneous NH₄TiOF₃/anatase TiO₂ interface in the layer-structured NH₄TiOF₃ mesocrystals lead to the upgraded electrochemical properties. Especially, the local build-in electric field induced by the nonuniform distribution of charge across the NH₄TiOF₃/anatase TiO₂ interface facilitates the charge transport during the charging and discharging cycling. The current electrode design strategy paves a new way in boosting stable ion storage and thus is of great interest in energy storage and conversion.

Controlled Hydrothermal Growth and Li+ Storage Performance of 1D VOx Nanobelts with Variable Vanadium Valence

One-dimensional (1D) vanadium oxide nanobelts (VO_x NBs) with variable V valence, which include V₃O₇·H₂O NBs, VO₂ (B) NBs and V₂O₅ NBs, were prepared by a simple hydrothermal treatment under a controllable reductive environment and a following calcination process. Electrochemical measurements showed that all these VO_x NBs can be adopted as promising cathode active materials for lithium ion batteries (LIBs). The Li⁺ storage mechanism, charge transfer property at the solid/electrolyte interface and Li⁺ diffusion characteristics for these as-synthesized 1D VO_x NBs were systematically analyzed and compared with each other. The results indicated that V₂O₅ NBs could deliver a relatively higher specific discharge capacity (213.3 mAh/g after 50 cycles at 100 mA/g) and median discharge voltage (~2.68-2.71 V vs. Li/Li⁺) during their working potential range when compared to other VO_x NBs. This is mainly due to the high V valence state and good crystallinity of V₂O₅ NBs, which are beneficial to the large Li⁺ insertion capacity and long-term cyclic stability. In addition, the as-prepared VO₂ (B) NBs had only one predominant discharge plateau at the working potential window so that it can easily output a stable voltage and power in practical LIB applications. This work can provide useful references for the selection and easy synthesis of nanoscaled 1D vanadium-based cathode materials.