Ultrathin Nanoribbons of in Situ Carbon-Coated V₃O₇·H₂O for High-Energy and Long-Life Li-Ion Batteries: Synthesis, Electrochemical Performance, and Charge–Discharge Behavior

The ever-growing demands of Li-ion batteries (LIBs) for high-energy and long-life applications, such as electrical vehicles, have prompted great research interest. Herein, by applying an interesting one-step high-temperature mixing method under hydrothermal conditions, ultrathin V 3 O 7 ·H 2 O@C nanoribbons with good crystallinity and robust configuration are in situ synthesized as promising cathode materials of high-energy, high-power, and long-life LIBs. Their capacity is up to 319 mA h/g at a current density of 100 mA/g. Moreover, the capacity of 262 mA h/g can be delivered at 500 mA/g, and 94% of capacity can be retained after 100 cycles. Even at a large current density of 3000 mA/g, they can still deliver a high capacity of 165 mA h/g, and 119% of the initial capacity can be kept after 600 cycles. Importantly, their energy density is up to 800 Wh/kg, which is 48–60% higher than those of conventional cathode materials (such as LiCoO 2, LiMn 2 O 4, and LiFePO 4 ), and they can maintain an energy density of 355 Wh/kg at a high power density of 8000 W/kg. Furthermore, based on ex situ X-ray diffraction and X-ray photoelectron spectroscopy technology, their exact charge–discharge behavior is reasonably described for the first time. Excitingly, it is found for the first time that the as-synthesized V 3 O 7 ·H 2 O@C nanoribbons are also great promising cathode materials for Na-ion batteries.