Informed Solid-state Electrochemical Cell Design for Operando X-ray Characterisation

The quest to develop safe, high-energy-density storage devices has led to many innovations in the field of lithium-ion batteries (LIBs), solid-state batteries (SSBs) being a promising development for next-generation energy storage. However, moving to solid-state electrolytes introduces novel degradation modalities, a mixture of chemical/electrochemical and mechanical, that need to be addressed before they will reach mass application. In this work, the degradation of SSBs is investigated with a bespoke SSB cell designed for operando X-ray imaging and tomography. The PEEK in-situ Press (PIP) cell enables unprecedented spatial and temporal resolution during operando X-ray micro-computed tomography (μ-CT) experiments. The PIP cell operates with a 1 mm diameter solid electrolyte pellet, providing a spatial resolution of about 2.4 μm on typical lab-based μ-CT experiments, or 750 nm utilising synchrotron radiation sources. This work takes a correlated experimental and modelling approach to explore the effects of SE pellet formation within the SSB cell and explores the impact of stress gradients in defect propagation. Here, Li| Li6PS5Cl |Li symmetric cells were investigated during various constant current cycling protocols. The degradation of the SE was tracked throughout the entire volume during the experiment and showed spatial variation in crack formation that exemplifies the importance of full volume analysis. Notability, defect propagation and subsequent cell performance is shown to be highly influenced by the cell design thus showcasing the importance of informed cell design in producing representative electrochemical cells.