Tris(trimethylsilyl) phosphite has been known as one of the state-of-the-art electrolyte additives for the high-voltage electrodes, especially for LiMO2 (M=Ni, Co, and Mn) electrodes. Tris(trimethylsilyl) phosphite is known not only to form low resistance solid-electrolyte interphase (SEI) layers on the positive electrode’s surface but also to eliminate HF. HF is usually formed by hydrolysis of LiPF6, and then, it reacts with SEI with increasing resistance and promotes the M-dissolution from the electrode materials. Tris(trimethylsilyl) phosphite is also known to scavenge O2 gas. O2 gas can be evolved due to the poor interfacial stability of the LiMO2 electrode at high operating voltages, and O2 exposed in the cell degrades the electrolytes components. We performed an ab initio-based screening model calculation with considering following phenomena in electrolytes : Li and M-cluster formation in solution, reduction of Li/M-cluster, M-binding on the electrode surface, redox-driven intermolecular H+-transport, small molecule’s binding such as O2 and HF, etc. Based on our calculations, we present profound understanding of tris(trimethylsilyl) phosphite-HF reactions and their electrochemical aspects, and provide an insight to tune their chemical and electrochemical characteristics based on the P-O-Si structures towards further designing and developing functional electrolyte additives.

Computational study of the operation mechanism of tris(trimethylsilyl) phosphite as a multi-functional additive for lithium-ion batteries

253rd National Meeting (2017)

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