Unraveling the ethylene carbonate effect on the electro-chemical/thermosafety features for practical LiNi_0.9Co_0.05Mn_0.05O₂∥graphite pouch cells

With the continuous development of the electrification industry, the development of high-specific batteries has attracted much attention. However, the safety of lithium-ion batteries is currently unable to meet the market demand due to poor thermal stability. Solving the thermal issues is crucial to improve battery safety. Ethylene carbonate (EC) not only plays an important interfacial film-forming role, but also poses safety risks in terms of reactivity. In this work, we conducted a series of gradient experiments utilizing different EC amounts and verified the effect of reducing EC on battery performance. A strategy is also proposed to design a new electrolyte. Ethyl methyl carbonate (EMC) is used instead of EC as the main solvent to improve the thermal safety of the battery, while salts and additives are used to dominate the film formation to improve the cycling stability of the battery under high voltages (4.5 V, ∼90% after 200 cycles). This work paves a new avenue for the development of novel electrolyte systems.