Manipulating the solvationstructure of nonflammable electrolyte and interface to enable uUnprecedented stability of graphite anodes beyond 2 years for safe pPotassium-ion batteries
Date
2021
Authors
Liu, S.
Mao, J.
Zhang, L.
Pang, W.K.
Du, A.
Guo, Z.
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Journal article
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Advanced Materials, 2021; 33(1):2006313-1-2006313-9
Statement of Responsibility
Sailin Liu, Jianfeng Mao, Lei Zhang, Wei Kong Pang, Aijun Du and Zaiping Guo
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Abstract
Potassium-ion batteries (PIBs) are attractive for low-cost and large-scale energy storage applications, in which graphite is one of the most promising anodes. However, the large size and the high activity of K⁺ ions and the highly catalytic surface of graphite largely prevent the development of safe and compatible electrolytes. Here, a nonflammable, moderate-concentration electrolyte is reported that is highly compatible with graphite anodes and that consists of fire-retardant trimethyl phosphate (TMP) and potassium bis(fluorosulfonyl)imide (KFSI) in a salt/solvent molar ratio of 3:8. It shows unprecedented stability, as evidenced by its 74% capacity retention over 24 months of cycling (over 2000 cycles) at the 0.2 C current rate. Electrolyte structure and surface analyses show that this excellent cycling stability is due to the nearly 100% solvation of TMP molecules with K⁺ cations and the formation of FSI⁻ -derived F-rich solid electrolyte interphase (SEI), which effectively suppresses the decomposition of the solvent molecules toward the graphite anode. Furthermore, excellent performance on high-mass loaded graphite electrodes and in a full cell with perylenetetracarboxylic dianhydride cathode is demonstrated. This study highlights the importance of the compatibility of both electrolyte and the interface, and offers new opportunities to design the electrolyte-SEI nexus for safe and practical PIBs.
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