Defined Poly(borosiloxane) as an Artificial Solid Electrolyte Interphase Layer for Thin-Film Silicon Anodes

Solid electrolyte interphase (SEI) formation in Li-ion batteries is essential for good long-term performance of the cell. However, for electrodes exhibiting high volume expansion (like Si and Sn), continuous SEI formation can not only deplete electrolyte content but also increase cell impedance and hence mediocre performance. This is particularly detrimental in the case of thin-film electrodes where there is a minute amount of active materials loading. In the current work, defined poly(borosiloxane) (PBS) as an artificial polymeric SEI having self-healing, anion-trapping properties, and electron-deficient boron moiety is investigated. Studies on thin-film Si electrodes show excellent enhancement with polymeric coating in terms of cycling stability. These improvements are attributed to a combination of factors including the anion-trapping effect of tricoordinate boron, self-healing ability of PBS, and adherence to the electrode surface.