Overcoming Ion Transport Barrier by Plasma Heterointerface Engineering: Epitaxial Titanium Carbonitride on...

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 (TiC_x N_{1- x} /N-TiO₂ ) heterostructure. Owing to the fast plasma effects and metastable hybrid phases, the TiC_x N_{1- 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 TiC_x N_{1- 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.