Insights into Structural and Chemical Evolution in Novel Energy Storage Materials Using Hard X-Rays

Reversible electrochemical conversion reactions represent a potential path towards exceptionally high energy density batteries. Although promising from fundamental energy perspectives, conversion electrodes still face challenges related to reversibility and cycle life, which limit widespread technological implementation. In contrast to current intercalation-based technologies where the electrode host structure is only minimally perturbed by Li-insertion and extraction, during conversion an electrode material completely restructures at the atomic level, expanding the scope of potential processes that can degrade reversibility, reduce cycle life and contribute to failure. Identifying how the electrochemical performance characteristics emerge from the complex correlation of atomic and electronic constituents is a significant characterization challenge magnified by the nanoscale nature and chemical heterogeneity of the electrode and reaction products. Using Pair Distribution Function measurements applied operando, during electrochemical cycling, we can gain insight into these complex multiphase behaviors and identify transient intermediates to develop a full understanding of the processes governing energy storage in these materials.