Na+ intercalation pseudocapacitance in graphene-coupled titanium oxide enabling ultra-fast sodium storage and long-term cycling

TLDR

Sodium‑ion batteries are promising for large‑scale energy storage, yet developing anodes that combine long‑term cycling stability with high‑rate capability remains a major challenge. The authors aim to demonstrate that a graphene‑titanium dioxide composite anode can achieve excellent electrochemical performance via sodium‑ion intercalation pseudocapacitance. First‑principle calculations reveal that graphene integration with TiO₂ reduces the Na⁺ diffusion barrier, boosting intercalation pseudocapacitance, which the authors exploit in their composite anode. The TiO₂/graphene composite delivers a specific capacity above 90 mAh g⁻¹ at 12,000 mA g⁻¹ (~36 C) and remains highly reversible for over 4,000 cycles, representing the longest‑lasting, high‑power sodium‑ion anode reported to date.

Abstract

Sodium-ion batteries are emerging as a highly promising technology for large-scale energy storage applications. However, it remains a significant challenge to develop an anode with superior long-term cycling stability and high-rate capability. Here we demonstrate that the Na+ intercalation pseudocapacitance in TiO2/graphene nanocomposites enables high-rate capability and long cycle life in a sodium-ion battery. This hybrid electrode exhibits a specific capacity of above 90 mA h g−1 at 12,000 mA g−1 (∼36 C). The capacity is highly reversible for more than 4,000 cycles, the longest demonstrated cyclability to date. First-principle calculations demonstrate that the intimate integration of graphene with TiO2 reduces the diffusion energy barrier, thus enhancing the Na+ intercalation pseudocapacitive process. The Na-ion intercalation pseudocapacitance enabled by tailor-deigned nanostructures represents a promising strategy for developing electrode materials with high power density and long cycle life. There are intensive efforts in developing anode materials for sodium-ion batteries. Here, the authors present a graphene-titanium dioxide composite as an anode material and show that sodium ion intercalation pseudocapacitance charge storage leads to excellent electrochemical properties.