Charge compensation, electronic structure and interfacial stability of the cathodes

Major Contributions
 

1. Unveiled a Mn-mediated reductive coupling mechanism, activated by Ca doping in P2-Na₀.₆₄Ca₀.₀₃Ni₀.₃₃Mn₀.₆₇O₂, in which uncommon electron transfer from oxygen to Mn enhances the reversibility and kinetics of anionic redox in sodium-ion battery cathodes.

2. Showed by synchrotron XAS and DFT that Ca incorporation lowers the crystal-field splitting of Mn 3d orbitals and facilitates charge transfer from O 2p to Mn eg orbitals at high voltage, suppressing irreversible lattice oxygen loss.

3. Ca²⁺ pillars in the Na layers inhibit the P2–O2 phase transition and reduce lattice strain, giving 80% capacity retention after 800 cycles at 1.0 C with a high cutoff voltage of 4.3 V.

主要貢獻
 

1. 揭示由鈣摻雜啟動的錳媒介還原耦合機制：在 P2-Na₀.₆₄Ca₀.₀₃Ni₀.₃₃Mn₀.₆₇O₂ 正極中，電子由氧轉移至錳離子，提升鈉離子電池陰離子氧化還原的可逆性與動力學。

2. 同步輻射 X 光吸收光譜與 DFT 計算顯示，鈣的引入降低 Mn 3d 軌域的晶體場分裂能，促進高電壓下 O 2p 向 Mn eg 軌域的電荷轉移，抑制不可逆的晶格氧流失。

3. 位於鈉層的 Ca²⁺ 作為剛性支柱，抑制 P2–O2 相變並降低晶格應變；在 4.3 V 高截止電壓、1.0 C 下循環 800 圈後仍保有 80% 容量。