Correlating (Chemo-)Mechanical Coupling in TiS ₂ during Li ⁺ Intercalation across Liquid and Solid Electrolytes Via <i>Operando</i> Analysis

The analysis of (chemo-)mechanical characteristics of electrode materials for rechargeable batteries is of prime importance to understand intercalation chemistries and related degradation phenomena from an atomistic toward an electrode level. Particularly operando methods are indispensable as they offer real-time insights into such (chemo-)mechanical processes which are usually difficult to capture with ex situ methods. In this context, we have studied the (chemo-)mechanical behavior of the model layered cathode active material TiS2 during Li+ intercalation in liquid and solid electrolytes (SEs). Via employing operando dilatometry in a liquid electrolyte and operando monitoring of uniaxial pressure evolution in solid-state cells, we show a perfect qualitative alignment of both methods. This validates the approach for the in-depth study of other electrode materials in various battery chemistries and a broad range of liquid-, hybrid, and SEs. Moreover, our results prove that even (chemo-)mechanical responses related to unique stages of Li+ intercalation and related volume changes of TiS2 can be captured with both methods in both electrolyte systems, emphasizing broad applicability. The operando techniques are macroscopic and quantitatively underestimate the actual (chemo-)mechanical changes on the crystallographic level, a limitation we discuss in detail.