In the search for new Li-ion battery electrodes that provide the best compromise between capacity, power, charge rates, and long-term stability, increasingly complex composite materials and reaction mechanisms have emerged. To develop an understanding of the fundamental phenomena that govern performance and failure of next-generation batteries, one must be able to probe and ultimately decouple electronic, chemical and structural transformations that span broad length and time scales. Only through the development and application of a suite of complementary characterization tools sensitive to aspects of structure, chemistry, electronic state and dynamics on appropriate scales, can we develop the comprehensive understanding of the electrode performance needed to design improved systems. These dynamic processes and multi-scale complexities are most ideally interrogated under simulated operating conditions within an electrochemical cell. For any operando experiment however, there is an implicit expectation that the data provides an accurate representation of the reaction behavior found under normal operating conditions. That is, the reactivity is not altered by the measurement itself or by changes to the sample environment required to enable the measurement. Yet, designing an electrochemical device that satisfies requirements for uncompromised X-ray measurements while delivering reliable electrochemical performance is nontrivial. Many of the separate requirements for high-quality X-ray data and electrochemical testing are largely incompatible.
This talk will focus on the potential impacts of the experimental design on the electrochemical reactivity and the main design features of a reliable operando electrochemical cell, using the example of Argonne’s multi-purpose in situ X-ray (AMPIX) cell. The AMPIX cell enables experiments providing greater insight into the complex processes that occur in operating batteries by allowing the electrochemical reactions to be probed at fine reaction intervals with remarkable consistency. The suitability of the AMPIX cell for a broad range of synchrotron-based X-ray scattering and spectroscopic measurements has been demonstrated over recent few years with a plethora of studies carried out at the APS and other light sources, resulting in multitude of high-impact publications.