Overcoming Ion Transport Barrier by Plasma Heterointerface Engineering: Epitaxial Titanium Carbonitride on Nitrogen‐Doped TiO2 for High‐Performance Sodium‐Ion Batteries

Anatase TiO2 is a promising anode material for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) due to its high specific capacity, low cost, and excellent cycle stability. However, low electrical conductivity and poor Na+ ion transport in TiO2 limit its practical applications. Here, substantially boosted Na+ ion transport and charge transfer kinetics are demonstrated by constructing a near‐ideal non‐rectifying titanium carbonitride/nitrogen‐doped TiO2 (TiCxN1–x/N‐TiO2) heterostructure. Owing to the fast plasma effects and metastable hybrid phases, the TiCxN1–x is epitaxially grown on TiO2. Energy band engineering at the interface induces high electron densities and a strong built‐in electric field, which lowers the Na+ diffusion barrier by a factor of 1.7. As a result, the TiCxN1–x/N‐TiO2 electrode exhibits excellent electrochemical performance. The reversible specific capacities at rates of 0.1 and 10 C reach 312.3 and 173.7 mAh g−1, respectively. After 600 cycles of charge and discharge at 10 C, the capacity retention rate is 98.7%. This work discovers an effective non‐equilibrium plasma‐enabled process to construct heterointerfaces that can enhance Na+ ion transport and provides generic guidelines for the design of heterostructures for a broader range of energy storage, separation, and other devices that rely on controlled ionic transport. Plasma discharge enables fast construction of near‐ideal band engineering of TiCxN1–x/N‐TiO2 heterostructure, which induces an extraordinary electron concentration at the heterointerface, thereby substantially improving the conductivity of TiO2 and accelerating the diffusion kinetics of sodium ions. The resulting negative electrode of sodium‐ion battery exhibits outstanding performance. This inspires a feasible method for fabricating advanced energy storage materials.