Influence of Tris(trimethylsilyl)phosphite Additive on the Electrochemical Performance of Lithium-ion Batteries Using Thin-film Ni-rich Cathodes (Supporting Information)

The characteristics of the interface between Ni-rich cathode materials and carbonate-based electrolytes are crucial for stability in charge-discharge cycles. In this study, we used tris(trimethylsilyl)phosphite (TMSPi) as an additive for film formation and investigated the properties of the layer formed on a LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) thin-film electrode. This layer can act as a barrier to mitigate the underlying attack at the oxygen sites of the layered Ni-rich structure. Moreover, this layer mainly consists of Li-rich organic components, leading to a decreased activation energy with a rapid Li-ion transfer process.