Structural reinforced NaTi₂(PO₄)₃ composite by pillar effects for constructing a high-performance rocking-chair desalination battery

Battery deionization (BDI) technique has attracted great attention as a potential candidate to tackle the freshwater crisis, but its application is plagued by the lack of electrode materials with large desalination capacity and excellent durability. Herein, Mn dopant-reinforced NaTi₂(PO₄)₃ (NT_2–xM_xP) composites with significantly enhanced structural stability and electronic/ionic conductivity were fabricated toward seawater desalination. Especially, the NT_1.5M_0.5P exhibits excellent desalination performance, affording a salt removal capacity (SRC) of 128.5 mg/g with a salt removal rate (SRR) of 18.4 mg g⁻¹ min⁻¹ and almost no capacity attenuation after 500 cycles. Furthermore, the NT_1.5M_0.5P further possesses favorable technical feasibility in different aqueous media, including desalination at various NaCl concentrations, temperature, solution pH, and natural seawater. Mechanism studies reveal that the NT_1.5M_0.5P undergoes a solid-solution reaction based on the reversible electrochemical reaction of the Ti⁴⁺/Ti³⁺ redox pair during the desalination/salination process. A rocking-chair desalination battery consisting of NT_1.5M_0.5P and NaFeHCF demonstrates a favorable desalination ability (average SRC of 49.4 mg/g and SRR of 1.73 mg g⁻¹ min⁻¹), outstanding cycling stability (92 % of capacity retention in 100 cycles), low energy consumption (0.288 kWh/kg-NaCl) and high average charging efficiency (86.9 %). This work sheds light on the rational design of advanced NASICON-type electrodes for seawater desalination with remarkable desalination capacity and long serving life.