Comparative study on the electronic structures and redox reactions in LiCrX2 and NaCrX2 (X = O and S). Issue 63 (13th November 2019)

• Record Type: Journal Article
• Authors: He, Yuewen; Shi, Xiaohong; Zheng, Meiying; Wu, Shunqing; Yang, Yong; Zhu, Zizhong
• Is Part Of: RSC advances. Volume 9:Issue 63(2019)
• Page Start: 36867
• Page End: 36874
• Publication Date: 2019-11-13
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c9ra08224g
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : A comparative study on the electronic structures and redox reactions in oxides (LiCrO2, NaCrO2 ) and sulfides (LiCrS2, NaCrS2 ) has been performed. All the S, O and Cr participate in the redox reactions. Abstract : LiCrO2 and NaCrO2 have been well-studied as cathode materials in lithium and sodium ion batteries, while the studies on LiCrS2 and NaCrS2 are relatively rare. In this work, a comparative study on the electronic structures and redox reactions in oxides (LiCrO2, NaCrO2 ) and sulfides (LiCrS2, NaCrS2 ) is performed. A first-principles method has been used to calculate the Bader charge transfer, the electronic structures and the magnetic moments during the entire delithiation or desodiation process. The Bader charge analysis suggests that all the S, O and Cr ions in LiCrX2 and NaCrX2 participate in the redox reactions, where the loss of electrons of S ions is clearly larger than that of O ions. Besides, the redox processes of Cr ions are of much less significance. It is noted that, in the sulfides, Cr ions even gain a small portion of electrons rather than losing electrons during the extraction of Li/Na ions. All the charge transfer happens between the S-3p/O-2p and the Cr-3d bands. The redox reactions of O or S ions originate from the energy levels of O/S being pushed towards/across the Fermi surface due to the strong p–d hybridization.