In this research, a Stanford, SLAC, and ALS (Advanced Light Source) team developed synchrotron liquid scanning transmission x-ray microscopy (STXM) to probe the spatiotemporal evolution of the lithium composition and insertion rate within lithium battery particles. By combining a microfluidic electrochemical cell with high-energy, synchrotron-generated X-rays, they imaged the lithium composition of single-crystalline, carbon-coated lithium iron phosphate particles as they delithiated (charged) and lithiated (discharged) in an organic liquid electrolyte. They acquired the nanoscale x-ray absorption spectra at the FeL3 edge, from which the local lithium composition (x in LiXFePO4) can be quantified.
Their results show that spatial heterogeneities in reaction rates account for the compositionally nonuniform solid-solution domains during (de)lithiation of LixFePO4. The reaction heterogeneities during delithiation(charge) is amplified but suppressed during lithiation(discharge). These results derived from synchrotron X-ray microscopy highlight the crucial role of surface reaction rate in lithiation, with implications for lithium battery electrode engineering and lithium battery management
J. Lim, Y. Li, D. H. Alsem, H. So, S. Lee, P. Bai, D.A. Cogswell, X. Liu, N. Jin, Y. Yu, N. Salmon, D. Shapiro, M. Z. Bazant, T. Tyliszczak, W. C. Chueh “Origin and Hysteresis of Li Compositional Spatio-Dynamics within Battery Primary Particles”, Science, 2016, 353, 566-571 .