Abstract
Direct observation of the lithiation and de-lithiation in lithium batteries on the component and microstructural scale is still difficult. This work presents recent advances in MeV ion-beam analysis, enabling quantitative contact-free analysis of the spatially-resolved lithium content and state-of-charge (SoC) in all-solid-state lithium batteries via 3 MeV proton-based characteristic x-ray and gamma-ray emission analysis. The analysis is demonstrated on cross-sections of ceramic and polymer all-solid-state cells with LLZO and MEEP/LIBOB solid electrolytes. Different SoC are measured ex-situ and one polymer-based operando cell is charged at 333 K during analysis. The data unambiguously show the migration of lithium upon charging. Quantitative lithium concentrations are obtained by taking the physical and material aspects of the mixed cathodes into account. This quantitative lithium determination as a function of SoC gives insight into irreversible degradation phenomena of all-solid-state batteries during the first cycles and locations of immobile lithium. The determined SoC matches the electrochemical characterization within uncertainties. The presented analysis method thus opens up a completely new access to the state-of-charge of battery cells not depending on electrochemical measurements. Automated beam scanning and data-analysis algorithms enable a 2D quantitative Li and SoC mapping on the µm-scale, not accessible with other methods.
Highlights
The development of advanced lithium ion batteries (LIB) with higher energy and power densities and longer cycle- and shelf life while maintaining or even improving safety is a major scientific endeavor with high practical relevance
The analysis is demonstrated on cross-sections of ceramic and polymer all-solid-state cells with LLZO and MEEP/LIBOB solid electrolytes
This section discusses the results of the elemental profiling and the obtained SoCs
Summary
The development of advanced lithium ion batteries (LIB) with higher energy and power densities and longer cycle- and shelf life while maintaining or even improving safety is a major scientific endeavor with high practical relevance. Starting with a similar setup from a former study with conventional Li-ion batteries [36,37], we adapted and improved the equipment and technique to enable ex-situ and operando measurements of polymer and oxide-based ASBs including an absolute quantification of Li at different states of charge (SoC). We compare and discuss the SoC determined via electrochemical measurements with the quantitative IBA This demonstration of the feasibility of 2-D mapping and absolute quantification using micro-beam IBA opens up a completely new era of spatially resolved, ex-situ, in-situ, and operando investigations of future Li batteries and enables a knowledge-driven design and validation of improvements on the microstructural level
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