Non-Flammable Electrolyte for Large-Scale Ni-Rich Li-Ion Batteries: Reducing Thermal Runaway Risks

Abstract

This research explores the properties and applications of flame-retardant esters (FREs), specifically triethyl phosphate (TEP) and tributyl phosphate (TBP), within electrolyte systems. The investigation assesses their roles as additives (30%v/v) and primary solvents (80%v/v) in conjunction with carbonate-based electrolytes (1.0 M LiPF6 in EC:DEC:EMC) and a novel non-flammable electrolyte formulation (1.2 M LiPF6 in 70%v/v TEP with 30%v/v fluoroethylene carbonate, FEC). Results indicate that incorporating FREs as additives adversely affects cell performance and maintain flammability risks, necessitating alternative strategies for achieving nonflammability. However, utilizing FREs as primary solvents alongside carbonate solvents shows promise for developing non-flammable electrolytes, despite concerns such as reductive decomposition that may limit suitability for certain battery cells. Conversely, the incorporation of 70%v/v FREs with 30%v/v FEC in the new electrolyte formulation yields a stable solid electrolyte interface, inhibiting FRE decomposition and sustaining battery cycling performance. This combination offers a potential solution for producing non-flammable electrolytes, serving as a viable alternative to solid-state electrolytes. The compatibility of the 1.2 M LiPF6 in TEP:FEC, 70:30 %v/v formulation with existing battery manufacturing processes further enhances its applicability. Figure 1