Quantum Chemical Characteristics of Additives That Enable the Use of Propylene Carbonate-Based Electrolytes

초록

Propylene carbonate- (PC-) based electrolytes are gaining attention as electrolytes in next-generation batteries because of their high stability and excellent temperature characteristics at high voltages. Lithium-ion batteries using PC-based electrolytes with 3-methyl-1,4,2-dioxazol-5-one (MDO) showed excellent capacity retention and lifetime characteristics. Here, quantum chemical methods are used to examine the molecular characteristics of MDO, and they suggest the unique molecular properties of this additive. Our calculations reveal that MDO is reduced prior to ethylene carbonate (EC) and PC solvents and undergoes a remarkably fast reduction decomposition process while producing thermodynamically stable reduction reaction products compared to vinylene carbonate (VC) and fluoroethylene carbonate (FEC) additives. This implies that a thermodynamically stable solid-electrolyte interphase (SEI) can form on the anode surface through a very rapid reaction. Upon reduction, the most preferred thermodynamic reaction between MDO and PC forms Li2CO3, a major SEI component. These reaction characteristics are unique and not observed with VC or FEC. The binding energy with Li+ is lower for MDO than for VC, FEC, or the solvents, making MDO the best choice for desolvation. We demonstrate that the molecular characteristics derived from quantum chemical calculations for MDO can also be applied to various previously reported PC-based electrolyte additives.

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