Lithium Difluorophosphate: A Boon for High Voltage Li Ion Batteries and a Bane for High Thermal Stability/Low Toxicity: Towards Synergistic Dual Additives to Circumvent this Dilemma

Autor: Maximilian Kubot, Lars Frankenstein, Elisabeth Muschiol, Sven Klein, Melanie Esselen, Martin Winter, Sascha Nowak, Johannes Kasnatscheew
Rok vydání: 2023
Předmět:
Zdroj: ChemSusChem. 16
ISSN: 1864-564X
1864-5631
Popis: The specific energy/energy density of state-of-the-art (SOTA) Li ion batteries can be increased by raising the upper charge voltage. However, instability of SOTA cathodes, i.e. LiNiyCoxMnyO2 (x + y + z = 1; NCM) triggers electrode crosstalk via enhanced transition metal (TM) dissolution, and contributes to severe capacity fade, in worst case, to a sudden death ("roll-over failure"). Lithium difluorophosphate (LiDFP) as electrolyte additive is able to boost high voltage performance via scavenging of dissolved TMs. However, LiDFP is chemically unstable and rapidly decomposes to toxic (oligo-) organofluorophosphates (OFPs) at elevated temperature; a process which can be precisely analyzed by means of high-performance liquid chromatography - high resolution mass spectroscopy. The toxicity of LiDFP can be proven via the well-known acetylcholinesterase inhibition test. Interestingly, while fluoroethylene carbonate (FEC) is inappropriate for high voltage applications as single electrolyte additive due to rollover failure, it is able to suppress formation of toxic OFPs. Based on this, a synergistic LiDFP/FEC dual-additive approach is suggested in this work, showing characteristic benefits of both individual additives, i.e. good capacity retention at high voltage in the presence of LiDFP and decreased OFP formation/toxicity induced by FEC.
Databáze: OpenAIRE
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