Investigation of Delamination-Induced Performance Decay at the Cathode/LLZO Interface
Pallab Barai, Tomás Rojas, Badri Narayanan, Anh T. Ngo, Larry A. Curtiss, Venkat Srinivasan
Abstract
The growing interest in solid-state batteries has resulted in increased focus on the issue of delamination at the cathode/solid-state electrolyte (SSE) interface. The extent of delamination, and its impact on impedance rise and capacity fade, is determined by a number of material properties, including cathode molar volume change and state-of-charge dependence, mechanical properties of the cathode and SSE, SSE grain boundary microstructure, fracture threshold of the interface, and interfacial exchange current density. The goal of this paper is to develop multiscale mathematical models to link these material properties to performance and provide guidance on possible approaches to minimize delamination, impedance rise, and capacity fade. We examine two cathodes, namely, LiNi0.8Mn0.1Co0.1O2 with a positive molar volume change and LiCoO2 with a negative molar volume change against a Li7La3Zr2O12 (LLZO) SSE. Density functional theory (DFT) is used to determine fundamental material properties at the interface, while mesoscale models are used to link these properties to macroscopic performance. Model results suggest that SSEs with smaller grains and low Young's modulus and cathodes with low molar volume changes provide opportunities for minimizing delamination.