Stacking Order Induced Anion Redox Regulation for Layer-Structured Na0.75 Li0.2 Mn0.7 Cu0.1 O2 Cathode Materials

Cui Ma; Aierxiding Abulikemu; Jian Bao; Tomoki Uchiyama; Yong-Yao Xia; Xun-Lu Li; Yoshiharu Uchimoto; Yong-Ning Zhou

doi:10.1002/smll.202302332

Stacking Order Induced Anion Redox Regulation for Layer-Structured Na_0.75 Li_0.2 Mn_0.7 Cu_0.1 O₂ Cathode Materials

Small. 2023 Sep;19(37):e2302332. doi: 10.1002/smll.202302332. Epub 2023 May 4.

Authors

Cui Ma¹, Aierxiding Abulikemu², Jian Bao¹, Tomoki Uchiyama², Yong-Yao Xia³, Xun-Lu Li^{1

4}, Yoshiharu Uchimoto², Yong-Ning Zhou¹

Affiliations

¹ Department of Materials Science, Fudan University, Shanghai, 200438, China.
² Department of Interdisciplinary Environment, Kyoto University, Kyoto, 606-8501, Japan.
³ Department of Chemistry, Fudan University, Shanghai, 200438, China.
⁴ Global Institute of Future Technology, Shanghai Jiao Tong University, Shanghai, 200240, China.

PMID: 37140106
DOI: 10.1002/smll.202302332

Abstract

Stacking order plays a key role in defining the electrochemical behavior and structural stability of layer-structured cathode materials. However, the detailed effects of stacking order on anionic redox in layer-structured cathode materials have not been investigated specifically and are still unrevealed. Herein, two layered cathodes with the same chemical formula but different stacking orders: P2-Na_0.75 Li_0.2 Mn_0.7 Cu_0.1 O₂ (P2-LMC) and P3-Na_0.75 Li_0.2 Mn_0.7 Cu_0.1 O₂ (P3-LMC) are compared. It is found that P3 stacking order is beneficial to improve the oxygen redox reversibility compared with P2 stacking order. By using synchrotron hard and soft X-ray absorption spectroscopies, three redox couples of Cu²⁺ /Cu³⁺ , Mn^3.5+ /Mn⁴⁺ , and O^2- /O^- are revealed to contribute charge compensation in P3 structure simultaneously, and two redox couples of Cu²⁺ /Cu³⁺ and O^2- /O^- are more reversible than those in P2-LMC due to the higher electronic densities in Cu 3d and O 2p orbitals in P3-LMC. In situ X-ray diffraction reveals that P3-LMC exhibits higher structural reversibility during charge and discharge than P2-LMC, even at 5C rate. As a result, P3-LMC delivers a high reversible capacity of 190.3 mAh g^-1 and capacity retention of 125.7 mAh g^-1 over 100 cycles. These findings provide new insight into oxygen-redox-involved layered cathode materials for SIBs.

Keywords: P3 structures; cathode materials; oxygen redox; sodium-ion batteries.

Abstract

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