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Corresponding Author

Kang-hua CHEN(kanghuachen@csu.edu.cn)

Abstract

Positive material Li2MnO3 shows the highest ratio of lithium to manganese among lithium-rich materials and exhibites the theoretical capacity up to 458 mAh·g -1, making it one of the most promising cathode materials. However, this material has the intrinsic low electrical conductivity and poor cycle stability. In this paper, Li2MnO3, the lithium-rich positive material, was prepared by sol-gel method using acetate as raw material and citric acid as a complexing agent. By using SnC2O4 as a tin source, Sn 4+ instead of Mn 4+ was introduced to obtain the materials with different doping amounts. The resultant solution was evaporated at 80 °C under vigorous stirring to get a viscous gel. Next, the resulting gel was dried at 120 °C for 12 h. Finally, the gathered precursor was calcined at 600 °C for 6 h under an air atmosphere to obtain the target material. It was found that the proper content of Sn 4+ doping could increase the specific discharge capacity of the material, obtaining as high as 256.3 mAh·g -1 at low current, but had a detrimental influence on the rate performance. On this basis, SnCl2 was used for doping modification, and the Sn 4+ and Cl - co-doping into Li2MnO3 revealed a better developed layered structure with high conductivity. The intensity of super lattice peak formed between 2θ = 20° and 30° was increased by Cl-doping, indicating the ordered Li/Mn in the TM layer. Especially, this Sn-Cl co-doped Li2MnO3 sample delivered the relatively high specific discharge capacity of approximate 160 mAh·g -1 after 80 cycles at 20 mA·g -1. At the high current density of 400 mA·g -1, this material provided the specific discharge capacity of 116 mAh·g -1, which is about twice that of the undoped sample.

Graphical Abstract

Keywords

lithium ion battery, positive electrode material, Li2MnO3, SnC2O4, SnCl2, Sn-Cl co-doping

Publication Date

2020-02-28

Online Available Date

2019-06-29

Revised Date

2019-06-28

Received Date

2019-03-13

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