Rapid and reversible sodium-ion cathode materials for NASICON Na₃MnTiP_3-xB_xO₁₂ achieved through Boron-substitution

Na₃MnTi(PO₄)₃ is a promising sodium-ion cathode material due to its relatively high specific capacity, excellent thermodynamic stability and low cost. However, unfavorable electron conductivity and slow kinetics limit its practical application. Here, a strategy of hetero and multivalent anion substitution is proposed to achieve high-rate performance and good capacity retention. Specifically, Na₃MnTiP_3-xB_xO₁₂ (x = 0.1, 0.2, and 0.3) doped with boron (B) at the phosphorus (P) site is prepared through sol-gel method. B-doping enhances the continuity of the electron density distribution and induces structural distortions that expand the diffusion channel for Na⁺, thereby improving electronic conductivity and ionic conductivity. Moreover, due to the differences in coordination and bond strength between BO and PO bonds, B doping mitigates the irreversible structural distortion during changing and discharging, thus enhancing cycle stability. The modified cathode material Na₃MnTiP_2.8B_0.2O₁₂ exhibits impressive rate performance, achieving 77.39 mAh g^-1 at 20C, significantly higher than undoped Na₃MnTi(PO₄)₃ (42.35 mAh g^-1). Its specific capacity is 126.48 mAh g^-1 with a capacity retention of 82.77 % after 1000 cycles at rate of 5C. Importantly, the assembled Na₃MnTiP_2.8B_0.2O₁₂//hard carbon (HC) full battery provides both high capacity and excellent cycling performance, offering valuable insights for the development of high-performance sodium superionic conductor (NASICON) structural cathode materials.