Effective stabilization of NCM622 cathodes in aqueous/non-aqueous hybrid electrolytes by adding a phosphazene derivate as Co-solvent

• Published in: Journal of power sources Vol. 541; p. 231670
• Main Authors: Du, Leilei, Hou, Xu, Zhao, Wenguang, Haneke, Lukas, Wang, Jun, Ju, Xiaokang, Liu, Xiangsi, Yang, Yong, Wrogemann, Jens Matthies, Künne, Sven, Winter, Martin, Placke, Tobias, Li, Jie
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-09-2022
• Subjects: Aqueous electrolytes; Ethoxy-(pentafluoro)-cyclotriphosphazene (PFN); High concentration; High energy density aqueous lithium ion batteries; Hybrid electrolytes; Aqueous electrolytes; High concentration; Ethoxy-(pentafluoro)-cyclotriphosphazene (PFN); Hybrid electrolytes; High energy density aqueous lithium ion batteries
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2022.231670

Recent progress in “water-in-salt” electrolytes (WiSEs) and “hybrid aqueous/non-aqueous electrolytes (HANEs)” made broader choices of active material in aqueous Li-ion batteries (ALIBs), because of their compared to standard aqueous electrolytes expanded electrochemical stability windows (ESWs). Exploring high energy density ALIBs is a consequently meaningful research topic. However, the formation of an ineffective interphase layer on the cathode surface in aqueous electrolyte obstructs the utilization of layered high energy cathode materials. Herein, a new organic compound, ethoxy-(pentafluoro)-cyclotriphosphazene (PFN) is introduced into HANEs as co-solvent. The addition of PFN can decrease the viscosity of highly concentrated HANEs and influence the solvation structure of Li+, facilitating the formation of uniform cathode electrolyte interphase (CEI). PFN forms the CEI component monoester phosphate, which betters the performance of ALIBs based on NCM622 || TiO2@LiTi2(PO4)3 (P:N = 1.5:1) that exhibit enhanced cycling stability with 79.3% capacity retention after 200 cycles at 1 C in the voltage range of 1.1–2.7 V, indicating that PFN can be a useful species to stabilize NCM622 operation in HANEs.
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•PFN was firstly studied as a co-solvent in aqueous electrolyte.•The ESW of hybrid electrolytes can be expanded to 4.9 V by introducing PFN.•PFN participates in the Li + solvation sheath.•Stable cycling of full cells was achieved with PFN as electrolyte co-solvent.