Dynamic Chemical X-Ray Microscopy on Energy Storage Materials

The shift from fossil fuels toward clean, renewable energy will require significant improvements in rechargeable battery technology for electric vehicles. Current battery technology limits electric vehicles to a short travel range, slow recharge, and costly price tag. Li-ion batteries promise the high specific capacity required to replace the internal combustion engine with a number of possible earth abundant electrode materials; however, setbacks such as capacity fading hinder the full capability of these rechargeable batteries. In the search for better electrode materials, high resolution chemical imaging during typical battery operation is vital in understand and overcoming the failure mechanisms of these materials. By combining X-ray absorption spectroscopy with high resolution, hard X-ray transmission microscopy (TXM), we have tracked the chemical changes of electrode material in real time during typical battery operation (Figure). [1, 2] We will discuss recent results tracking electrochemical and morphological changes in cathode materials during cycling, including LiFePO4,[3] LiCoO2, and Li2Cu0.5Ni0.5O2. Finally, we will discuss how ptychography, an emerging X-ray microscopy technique that promises sub-5 nm resolution, has the potential to image batteries during cycling at resolutions that rival in situ TEM with liquid cells. [1] J.N. Weker, X. Huang, M.F. Toney, 2 (2016) 14-21. [2] J. Nelson Weker, M.F. Toney, Advanced Functional Materials, 25 (2015) 1622-1637. [3] J. Nelson Weker, Y. Li, R. Shanmugam, W. Lai, W.C. Chueh, ChemElectroChem, 2 (2015) 1576-1581. Figure 1