Insights into polymer electrolyte stability and reaction pathways: A first-principle calculations study

To identify suitable polymer candidates for electrolytes in solid-state batteries, this study investigates the electrochemical behavior and decomposition pathways of four monomers involving esters, ethers, and carbonates via first-principles calculations. In particular, we determine the oxidation and reduction potentials of these monomers near different ions (Li+, TFSI-, and [Li]+[TFSI]-) and the corresponding reorganization energies. The latter quantity is central to Marcus theory of electron transfer and, therefore, provides additional kinetic information. Our results reveal notable sensitivity of the monomers to reduction in a Li+-rich regime and to oxidation in a TFSI--rich regime. Additionally, the reactivity and decomposition pathways of the monomers were investigated for various electrochemical environments, focusing on the quantification of gaseous and ionic products during the initial stage of formation of interphasial layers. Based on the electrochemical windows and spontaneous Ab initio molecular dynamics calculations, we observe that monomers containing carbonate groups exhibit greater stability against decomposition caused by reduction, especially in different regimes, when compared to monomers with ester and ether groups.