In Situ Self-Assembled FeWO₄/Graphene Mesoporous Composites for Li-Ion and Na-Ion Batteries

With the growing demands for large-scale applications, rechargeable batteries with cost-effective and environmental-friendly characteristics have gained much attention in recent years. However, some practical challenges still exist in getting ideal electrode materials. In this work, three-dimensional FeWO 4 /graphene mesoporous composites with incredibly tiny nanospheres of 5–15 nm in diameter have been synthesized by an in situ self-assembled hydrothermal route. First-principles density functional theory has been used to theoretically investigate the crystal structure change and the insertion/extraction mechanism of Li and Na ions. Unlike most graphene-coated materials, which suffer the restacking of graphene layers and experience significant irreversible capacity losses during charge and discharge process, the as-prepared composites have alleviated this issue by incorporating tiny solid nanospheres into the graphene layers to reduce the restacking degree. High capacity and excellent cyclic stability have been achieved for both Li-ion and Na-ion batteries. At the current density of 100 mA g –1, the discharge capacity for Li-ion batteries remains as high as 597 mAh g –1 after 100 cycles. The Na-ion batteries also exhibit good electrochemical performance with a capacity of 377 mAh g –1 at 20 mA g –1 over 50 cycles. The synthetic procedure is simple, cost-effective and scalable for mass production, representing a step further toward the realization of sustainable batteries for efficient stationary energy storage.