Nonfluorinated Antisolvents for Ultrastable Potassium-Ion Batteries

Abstract

A robust interface between the electrode and electrolyte is essential for the long-term cyclability of potassium-ion batteries (PIBs). An effective strategy for achieving this objective is to enhance the formation of an anion-derived, robust, and stable solid−electrolyte interphase (SEI) via electrolyte structure engineering. Herein, inspired by the application of antisolvents in recrystallization, we propose a nonfluorinated antisolvent strategy to optimize the electrolyte solvation structure. In contrast to the conventional localized superconcentrated electrolyte introducing high-fluorinated ether solvent, the anion−cation interaction is considerably enhanced by introducing a certain amount of nonfluorinated antisolvent into a phosphate-based electrolyte, thereby promoting the formation of a thin and stable SEI to ensure excellent cycling performance of PIBs. Consequently, the nonfluorinated antisolvent electrolyte exhibits superior stability in the K||graphite cell (negligible capacity degradation after 1000 cycles) and long-term cycling in the K||K symmetric cell (>2200 h), as well as considerably improved oxidation stability. This study demonstrates the feasibility of optimized electrolyte engineering with a nonfluorinated antisolvent, providing an approach to realizing superior electrochemical energy storage systems in PIBs.

Restructuring Electrolyte Solvation by a Partially and Weakly Solvating Cosolvent toward High-Performance Potassium-Ion Batteries

“…The average CE value of the 2 M KFSI/DEM–DME electrolyte was as high as 99.4%, while the 2 M KFSI/DME electrolyte failed quickly (Figure d). The average CE of this electrolyte also exhibits a relatively high advantage over other reported electrolytes. ,,− The K||Cu cells failed faster in 2 M KFSI/DME electrolytes, probably due to severe growth of potassium dendrites (the question of dendrite growth will be confirmed in subsequent discussions). Upon slicing the potassium metal electrode, its surface exhibits nonuniformity, leading to a disparate current density distribution.…”

“…15 Meanwhile, low-concentration DME-based electrolytes exhibit a serious cointercalation phenomenon on graphite electrodes. 16,17 This can lead to structural damage and rapid degradation of the graphite electrode capacity, limiting their application in PIBs. 18,19 To address this problem with lowconcentration electrolytes (LCEs), several strategies have been proposed regarding the development of high-performance electrolytes, including high-concentration electrolytes (HCEs), 20,21 localized HCEs (LHCEs), 22 and weakly solvating electrolytes (WSEs).…”

“…Unfortunately, the high energy level of the highest occupied molecular orbital (HOMO) of DME results in poor stability at high voltages, constraining DME-based electrolytes to low-voltage batteries . Meanwhile, low-concentration DME-based electrolytes exhibit a serious cointercalation phenomenon on graphite electrodes. , This can lead to structural damage and rapid degradation of the graphite electrode capacity, limiting their application in PIBs. , To address this problem with low-concentration electrolytes (LCEs), several strategies have been proposed regarding the development of high-performance electrolytes, including high-concentration electrolytes (HCEs), , localized HCEs (LHCEs), and weakly solvating electrolytes (WSEs). , These electrolytes preferentially coordinate anions with cations to form contact ion pairs (CIPs) and aggregated ion pairs (AGGs) in bulk electrolytes, which produce a strong inorganic passivation layer on the electrode surface . HCEs, despite their potential benefits, are hindered from commercial deployment due to their prohibitive costs and elevated viscosity.…”

Effect of Antisolvent Additives in Aqueous Zinc Sulfate Electrolytes for Zinc Metal Anodes: The Case of Acetonitrile

“…However, aceto­nitrile does not dissolve ZnSO 4 , making it an anti­solvent in this system. Given that the exact role of anti­solvents in batteries is generally not clear, ,, uncovering their role in improved electro­chemical performance may help the design of stable and durable batteries. Furthermore, there are a growing number of reports on additives in which claims of improved performance are accepted without sufficient experimental evidence for the mechanisms by which these performance improvements are achieved.…”

Non-Flammable Electrolyte Mediated by Solvation Chemistry toward High-Voltage Lithium-Ion Batteries

“…Alternatively, phosphorus-based solvents, such as trimethyl phosphate (TMP) − and triethyl phosphate (TEP), , have also been widely employed as flame-retardant solvents due to their relatively low cost and environmental sustainability. However, these phosphorus-based electrolytes exhibit incompatibility with the graphite anode, leading to graphite exfoliation caused by the cointercalation of Li + and solvents, additionally prone to decomposition on the anode side. − While the strategies of designing high-concentration electrolytes by increasing the lithium salt concentration or creating locally concentrated electrolytes by adding fluorinated ether can help maintain electrode stability and mitigate electrolyte decomposition, − the costs have been elevated, and the uniform control of concentrated electrolytes during battery manipulation, including the injection process, poses significant challenges.…”