Activating Stable Multielectron Transfer via High-Frequency Na⁺ Jumping for a Sc-doped Na_3.97VMn_0.97Sc_0.03(PO₄)₃

The Na₄VMn(PO₄)₃ (NVMP) cathode is considered one of the most promising candidates for sodium-ion batteries (SIBs), but it suffers from a low capacity due to the limited kinetics of V³⁺/V⁴⁺ and Mn²⁺/Mn³⁺ in the electrochemical reaction. A higher capacity can be achieved by activating a redox pair with high valence states like V⁴⁺/V⁵⁺. However, activation of those redox pairs in conventional NVMP cathode requires a redox potential beyond 4.0 V (vs Na⁺/Na) and induces serious structural degradation. Herein, a scandium (Sc)-doped Na_3.97VMn_0.97Sc_0.03(PO₄)₃ is designed, which activates multielectron transfer while effectively mitigating reversibility compromises by configuring a rational voltage range. The capacity can be improved by 16.7% to 113.8 mAh g^-1 based on more electron transfer from 1.75e^- to 2.05 e^-, which is mainly attributed to the accelerated redox reactions of V³⁺/V⁴⁺ and Mn²⁺/Mn³⁺ within 2.0-3.8 V (vs Na⁺/Na). The enhanced kinetics are achieved by faster Na⁺ diffusion kinetics via high-frequency Na⁺ jumping, which originates from enriched V_Na' vacancy by Sc doping. The improved kinetics also ameliorate grain uniformity during repeatable charge-discharge cycling, leading to an excellent capacity retention of 80.2% after 1400 cycles at 5C. These findings offer a promising pathway toward facile and controllable multi-electron transfer cathodes.