Understanding Shelf Life of Electrolytes with LiPF 6 Under Commercially Relevant Storage Conditions

Lithium hexafluorophosphate (LiPF 6 ) salt is the most commonly used lithium salt in commercial Li-ion batteries due to its high conductivity, passivation of Al current collectors for positive electrodes, and participation in SEI layer formation at graphite anodes. 1 However, LiPF 6 suffers from poor thermal stability and poor stability toward protic species (like water) leading to decomposition that can significantly reduce Li-ion battery performance especially under the extreme conditions demanded by today’s industrial applications. Specifically, LiPF 6 decomposition leads to HF generation, especially in the presence of water, 2 which results in multiple negative outcomes in Li-ion cells including dissolution of cathode materials and gas generation. 3 Conditions during electrolyte blending, transport, and/or storage often exacerbate LiPF 6 instability and increase HF generation. To date, efforts to replace LiPF 6 have not proven to be commercially successful, therefore strategies to improve the stability of LiPF 6 electrolytes under relevant storage conditions are critical to support the deployment of Li-ion batteries. Orbia Fluor and Energy Materials has extensively characterized the degradation of LiPF 6 as a function of multiple conditions, including temperature, water content, electrolyte composition, and container materials to inform the design of strategies to improve stability. This poster will illustrate the understanding of LiPF 6 decomposition (and HF generation) under conditions relevant to the Li-ion electrolyte supply chain and will present data showing a series of fluorinated materials that improve the thermal stability of LiPF 6 electrolyte through the elimination of existing HF and suppression of additional formation. In addition, Orbia Fluor and Energy Materials has launched a custom electrolyte blending business to provide high quality, domestically produced lithium-ion battery electrolytes to enable the clean energy transition. References: Sascha Nowak and Martin Winter 2015 J. Electrochem. Soc. 162 A2500 Hui Yang et al 2006 J. Power Sources 161 573 Weishan Li 2020 J. Electrochem. Soc. 167 090514