In Situ N-Doped Carbon Coating on NaTi ₂ (PO ₄ ) ₃ for Aqueous Hybrid-Ion Batteries Mitigating Hydrogen Evolution Reactions and Material Dissolution

Aqueous Li + /Na + hybrid-ion batteries (AIBs) have emerged as a promising alternative to address concerns regarding lithium resource scarcity and the safety issues associated with organic electrolytes. However, the development of NaTi 2 (PO 4 ) 3 (NTP) as a high-performance anode material for AIBs is hindered by intrinsic challenges, including material dissolution and the competitive hydrogen evolution reaction (HER) at the electrode–electrolyte interface. Meanwhile, the scalable synthesis of NTPs remains constrained by the complexity of conventional preparation methods. In this work, the N-doped carbon-coated NaTi 2 (PO 4 ) 3 (NTP@NC) as an advanced AIB anode material is synthesized. The carbon coating effectively suppresses HER and material dissolution while maintaining electrolyte pH stability. Remarkably, the NTP@NC demonstrates a high-capacity retention of 66% after 1000 cycles, and the assembled pouch cell retains stable performance over 300 cycles. The large-scale production of the material is successfully achieved with a batch mass of 4 kg. This work establishes a clear correlation among the microstructure, composition, and electrochemical performance, facilitating the practical development of anode materials for high-safety aqueous battery technologies.