Exploring the Charge Compensation Mechanism of P2-Type Na 0.6 Mg 0.3 Mn 0.7 O 2 Cathode Materials for Advanced Sodium-Ion Batteries

Chen Cheng, Manling Ding, Tianran Yan, Kehua Dai, Jing Mao, Nian Zhang, Liang Zhang and Jinghua Guo
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Chen Cheng: Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, 199 Ren’ai Road, Suzhou 215123, China
Manling Ding: Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, 199 Ren’ai Road, Suzhou 215123, China
Tianran Yan: Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, 199 Ren’ai Road, Suzhou 215123, China
Kehua Dai: College of Chemistry, Tianjin Normal University, Tianjin 300387, China
Jing Mao: School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
Nian Zhang: State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
Liang Zhang: Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, 199 Ren’ai Road, Suzhou 215123, China
Jinghua Guo: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA

Energies, 2020, vol. 13, issue 21, 1-12

Abstract: P2-type sodium layered transition metal oxides have been intensively investigated as promising cathode materials for sodium-ion batteries (SIBs) by virtue of their high specific capacity and high operating voltage. However, they suffer from problems of voltage decay, capacity fading, and structural deterioration, which hinder their practical application. Therefore, a mechanistic understanding of the cationic/anionic redox activity and capacity fading is indispensable for the further improvement of electrochemical performance. Here, a prototype cathode material of P2-type Na 0.6 Mg 0.3 Mn 0.7 O 2 is comprehensively investigated, which presents both cationic and anionic redox behaviors during the cycling process. By a combination of soft X-ray absorption spectroscopy and electroanalytical methods, we unambiguously reveal that only oxygen redox reaction is involved in the initial charge process, then both oxygen and manganese participate in the charge compensation in the following discharge process. In addition, a gradient distribution of Mn valence state from surface to bulk is disclosed, which could be mainly related to the irreversible oxygen activity during the charge process. Furthermore, we find that the average oxidation state of Mn is reduced upon extended cycles, leading to the noticeable capacity fading. Our results provide deeper insights into the intrinsic cationic/anionic redox mechanism of P2-type materials, which is vital for the rational design and optimization of advanced cathode materials for SIBs.

Keywords: sodium-ion batteries; P2-tpye oxides; charge compensation mechanism; X-ray absorption spectroscopy; electronic structure (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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