| Abstract Scope |
In lithium-ion batteries, optimizing the solid electrolyte interphase (SEI) remains a central challenge for durable, high-capacity batteries. Engineering a better SEI is challenging, due to the difficulty in characterizing and modeling its chemical composition and microstructure. Herein, we will present neutron reflectometry and quartz crystal microbalance (QCM) as an operando probe of SEI structure. A dual-layer SEI is observed, with a 3.7 nm thick inner layer and a 15.4 nm thick outer layer, and a mass per area of 1207.2 ng-cm2. QCM provides insight into the SEI formation and evolution dynamics, and Monte Carlo simulations identify SEI chemical compositions consistent with the combined measurements, which are consistent with a primarily inorganic, dense inner layer and a primarily organic, porous outer layer, directly confirming structures proposed in the literature. These experiments provide a platform for validating physical-chemistry based simulations of SEI growth and evolution, using the open source software package Cantera. |