Effects of vinylene carbonate and 1,3-propane sultone on high-rate cycle performance and surface properties of high-nickel layered oxide cathodes

The high-rate half-cell performance of LiNi_0.3Co_0.3Mn_0.3O₂ (NCM333), LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622), and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode materials is investigated with the base electrolyte of LiPF₆/ethylene carbonate (EC):ethylmethyl carbonate (EMC) and the additives of vinylene carbonate (VC) and 1,3-propane sultone (PS). The effects of these additives on the cathode surfaces are particularly examined in terms of the reduction products of the electrolyte components and the formation of solid electrolyte interphase (SEI) on cathode surfaces. The cathode SEI appears less after formation for all NCM materials, but it accumulates with repeated charging/discharging at a high rate. Of these, the addition of VC + PS to the base electrolyte sufficiently provides stable cathode SEI with suppressed thickness under cycling at a high rate by inhibiting the further decomposition of reduction products. The synergy of VC + PS may be originated by the combination of vinyl and sulfone functional groups to provide passivation film with cross-linked protective networks on Ni-rich NCM cathode materials. Thus, superior cycle performance is achieved, especially for NCM811.