Efficient Modulation d/p‐Band Center Proximity in Birnessite‐Type MnO<sub>2</sub> by Cation/Anion Co‐Doping for Enhanced Dual‐Ion Storage
Yuhui Xu, Gaini Zhang, Xiaoxue Wang, Jianhua Zhang, Hang Wen, Dongniu Wang, Yitong Yuan, Qinting Jiang, Huaming Qian, Yukun Xi, Jiaxuan Zuo, Ming Li, Jihu Liu, Huijuan Yang, Yangyang Luo, Jingjing Wang, Wenbin Li, Xifei Li
Abstract
Abstract The wide band gap of δ‐MnO 2 and the restricted regulation of the p‐band center ( p ) of active oxygen atoms hinder electron conduction and ion diffusion during zinc storage. Heteroatom doping has proven effective in improving zinc storage. However, the regulation of p solely through cation doping is comparatively constrained. Herein, a cation/anion co‐doping strategy is proposed to simultaneously adjust the p of oxygen and the d‐band center ( d ) of Mn by establishing Mn–O–Ca and Mn─N bonds in Ca/N co‐doped δ‐MnO 2 (Ca/N‐MnO 2 ). This co‐doping effect induces a shift in the predominant stretching vibration mode of Mn─O bonds in [MnO 6 ] octahedra, resulting in a decreased d/p‐band center proximity (Δ d‐p ) of 1.688 eV (1.750 eV for δ‐MnO 2 ). Consequently, both adsorption capacity and adsorption/desorption rates of Zn 2+ /H + ions are enhanced. Theoretical calculations further reveal that co‐doping significantly triggers the optimization of the band gap, migration energy barrier, and adsorption energy. As a result, Ca/N‐MnO 2 achieves a remarkable reversible capacity of 192.7 mAh g −1 at 1.0 A g −1 after 200 cycles and exceptional rate performance. Furthermore, the energy enhancement mechanisms are thoroughly elucidated. This synergistic d/p‐band center regulation strategy offers significant potential for efficient energy storage applications.