Session: 09-03-01: Advanced Electrochemical Energy Materials: Characterization, Modeling, and Theoretical Analysis

Paper Number: 167108

Ionic Interdiffusion at the Cathode/solid-Electrolyte Interface in All Solid State Batteries 

All solid state lithium ion batteries are expected to dramatically enhance the energy density of next generation energy storage devices through the realization of lithium metal anodes. All solid state batteries are also expected to be safer than their conventional counterparts due to the absence of the volatile liquid electrolytes. Successful implementation of all solid state batteries requires the cathode active materials to operate successfully with mechanically stiff solid electrolytes. Majority of the existing solid electrolytes demonstrate limited domain of stability and tend to react with the cathode materials either during the high temperature synthesis process, or when charged to higher voltages. Ionic interdiffusion between the cathode and the solid electrolyte leads to the formation of passivating interlayers, which not only lead to an increase in the cell resistance but also consume cyclable lithium resulting in significant capacity fade. Various protective interphase layers (such as, lithium borate, lithium niobate, lithium phosphate, lithium niobium tantalum oxide, etc.) are implemented in between the cathode and the solid electrolytes, which can effectively minimize the interdiffusion process. However, the existing technologies demonstrate limited success in eliminating the interdiffusion induced bottlenecks over long periods of time.

In the present context, a mathematical framework is developed to predict the extent of ionic intermixing between the cathode and the solid electrolytes, and estimate the evolution of the thickness of the detrimental interphase region. A combination of mass and momentum balance is implemented to capture the interdiffusion of ions and corresponding evolution of stresses. Self-diffusion coefficients of individual species are extracted from atomistic simulations. Mesoscale level simulations indicate that the interdiffusion induced mixing of ionic species initiate at a rapid pace, but eventually slow down due to the generation of compressive stresses. A mechano-electrochemical model is also developed at the mesoscale level to understand the impact of the passivating interphase layer on the voltage vs capacity response of the cathode active materials. Charge, mass, and momentum balance relations are solved for estimating the performance of the cathode active materials. The developed framework is capable of delineating the impact of interfacial delamination and resistance growth on the overall cathode performance. It has been observed that interfacial resistance growth cannot entirely explain the experimental trends; the decrease in lithium diffusivity and loss of active material needs to be incorporated to successfully predict the voltage vs. capacity relations. Finally, some strategies will be discussed that can help to design protective interphases layers between the cathode and solid electrolytes and effectively minimize the interdiffusion induced challenges in all solid state lithium ion batteries.

Presenting Author: Pallab Barai Argonne National Laboratory

Presenting Author Biography: Dr. Pallab Barai is a Computational Scientist at the Applied Materials Division in Argonne National Lab. He mostly focuses on developing computational capabilities for analyzing the synthesis and performance of various materials used in lithium ion batteries. He received his PhD in Mechanical Engineering from Texas A&M University and worked as postdoc in different national labs before starting his present appointment at Argonne. Dr. Barai has published more than 50 articles in peer reviewed journals and presented his research activities in various international conferences through contribution as well as invitation.

Authors:

Pallab Barai Argonne National Laboratory