Multifunctional Separator Allows Stable Cycling of Potassium Metal Anodes and of Potassium Metal Batteries

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Liu, Pengcheng
Hao, Hongchang
Celio, Hugo
Cui, Jinlei
Ren, Muqing
Wang, Yixian
Dong, Hui
Chowdhury, Aminur Rashid
Hutter, Tanya
Perras, Frédéric A.
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Iowa State University Digital Repository, Ames IA (United States)
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Ames National Laboratory

Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.

For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.

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This is the first report of a multifunctional separator for potassium-metal batteries (KMBs). Here, double-coated tape-cast microscale AlF3 on polypropylene (AlF3@PP) yields state-of-the-art electrochemical performance: symmetric cells are stable after 1000 cycles (2000 h) at 0.5 mA cm–2 and 0.5 mAh cm–2, with 0.042 V overpotential. Stability is maintained at 5.0 mA cm–2 for 600 cycles (240 h), with 0.138 V overpotential. Postcycled plated surface is dendrite-free, while stripped surface contains smooth solid electrolyte interphase (SEI). Conventional PP cells fail rapidly, with dendrites at plating, and “dead metal” and SEI clumps at stripping. Potassium hexacyanoferrate(III) cathode KMBs with AlF3@PP display enhanced capacity retention (91% at 100 cycles vs 58%). AlF3 partially reacts with K to form an artificial SEI containing KF, AlF3, and Al2O3 phases. The AlF3@PP promotes complete electrolyte wetting and enhances uptake, improves ion conductivity, and increases ion transference number. The higher of K+ transference number is ascribed to the strong interaction between AlF3 and FSI– anions, as revealed through 19F NMR. The enhancement in wetting and performance is general, being demonstrated with ester- and ether-based solvents, with K-, Na-, or Li- salts, and with different commercial separators. In full batteries, AlF3 prevents Fe crossover and cycling-induced cathode pulverization.
This is a manuscript of an article published as Liu, Pengcheng, Hongchang Hao, Hugo Celio, Jinlei Cui, Muqing Ren, Yixian Wang, Hui Dong et al. "Multifunctional separator allows stable cycling of potassium metal anodes and of potassium metal batteries." Advanced Materials 34, no. 7 (2022): 2105855. DOI: 10.1002/adma.202105855. Copyright 2021 Wiley-VCH GmbH. DOE Contract Number(s): 89233218CNA000001; AC05-00OR22725; NA0003525; AC02-07CH11358; 1911905. Posted with permission.