Activating Stable Multielectron Transfer via High-Frequency Na

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 Na3.97VMn0.97Sc0.03(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 VNa' 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.