Boosting lithium storage behavior of TiO₂@C nanocomposites via polyphosphazene-derived P/S/N triple-doping and carbon coating

Heteroatom doping and carbon coating are essential techniques for improving the conductivity and reaction kinetics of intercalation-type anode materials in lithium-ion batteries. However, it is difficult to achieve heteroatom doping and carbon coating at the same time through simple processes. Here, we propose a simple method to simultaneously achieve carbon-coating and P/S/N triple-doping by introducing polyphosphazene (PZS) as precursor. We first prepare PZS-coated titanium-based metal-organic frameworks (MIL-125), which can be readily converted into phosphorus/sulfur/nitrogen (P/S/N) co-doped carbon-coated titanium dioxide (TiO₂) nanocomposites (PSN-C@TiO₂@C) by simple calcination under an inert atmosphere. The heteroatom doping and carbon hybridization synergistically enhance the conductivity and ion diffusion of the PSN-C@TiO₂@C, which not only change the local charge density of the nanocomposite, but also generate more active sites. Benefiting from the above advantages, the well-designed PSN-C@TiO₂@C anode exhibits significantly improved specific capacity and rate performance, maintaining high reversible specific capacities of 272.2 mA h g⁻¹ after 1000 cycles at 1000 mA g⁻¹ and 141.1 mA h g⁻¹ after 2000 cycles at 5000 mA g⁻¹. This study presents a novel simplified method for multi-element-doping and carbon-coating, which can be generally applied for developing advanced electrode materials for energy storage application.