Elucidation of the Jahn-Teller effect in a pair of sodium isomer. (November 2020)

• Record Type: Journal Article
• Authors: Wang, Peng-Fei; Jin, Ting; Zhang, Jiaxun; Wang, Qin-Chao; Ji, Xiao; Cui, Chunyu; Piao, Nan; Liu, Sufu; Xu, Jijian; Yang, Xiao-Qing; Wang, Chunsheng
• Is Part Of: Nano energy. Volume 77(2020)
• Publication Date: 2020-11
• Subjects: Sodium-ion batteries -- Cathode -- Jahn-Teller effect -- Sodium isomer -- Electrochemistry; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2020.105167
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Jahn-Teller distorted Mn(III) (t2g 3 eg 1 ) ions play a key role in the performance of manganese-based layered oxides. Here we show that there is an obvious relationship between the Jahn-Teller distortion of a trivalent manganese and the electrochemistry in a pair of Na isomer, namely orthorhombic and hexagonal P2-type Na2/3 Mn0.9 Ti0.1 O2 having the same composition. It is found that more reversible phase transformations, higher working voltage and faster Na diffusion correlated with Jahn-Teller effect are found for distorted P′2-Na2/3 Mn0.9 Ti0.1 O2 upon Na + ions extraction/insertion. Such Jahn-Teller distorted Mn assisted Na migration enables that the orthorhombic Na2/3 Mn0.9 Ti0.1 O2 delivers a high specific capacity of 204.0 mA h g −1 with a 2.7 V average working voltage, reaching 550 Wh Kg −1 with both better cycle stability (a capacity retention of 82.3% after 100 cycles) and enhanced rate capability (97.8 mA h g −1 cycled at 10C) in Na cell in contrast with undistorted Na2/3 Mn0.9 Ti0.1 O2 . This strategy for understanding the Jahn-Teller effect of P2-type compounds at orbital energy level grasps new insight into designing high energy density positive electrode materials for Na-ion batteries. Graphical abstract: A pair of sodium isomer with stoichiometric Na 2/3 Mn 0.9 Ti 0.1 O 2 composition are reported as high-energy cathode for Na-ion batteries. The orthorhombic phase demonstrates more reversible phase transformations, higher working voltage and faster Na diffusion correlated with Jahn-Teller effect than hexagonal one upon Na + ions extraction/insertion. Image 1 Highlights: A pair of sodium isomer with different Jahn-Teller distortion are reported as high-energy cathode for Na-ion batteries. The orthorhombic Na2/3 Mn0.9 Ti0.1 O2 delivers a high specific capacity of 204.0 mA h g −1 with a 2.7 V average working voltage, reaching 550 Wh Kg −1 . The orthorhombic phase demonstrates more reversible phase transformations, higher working voltage and faster Na diffusion than hexagonal one.