Articles by Kehua Dai in JoVE
Elemental-sensitive Detection of the Chemistry in Batteries through Soft X-ray Absorption Spectroscopy and Resonant Inelastic X-ray Scattering Jinpeng Wu1,2, Shawn Sallis2,3, Ruimin Qiao2, Qinghao Li2,4, Zengqing Zhuo2,5, Kehua Dai2,6, Zixuan Guo2,7, Wanli Yang2 1Geballe Laboratory for Advanced Materials, Stanford University, 2Advanced Light Source, Lawrence Berkeley National Laboratory, 3Department of Materials Science and Engineering, Binghamton University, 4School of Physics, National Key Laboratory of Crystal Materials, Shandong University, 5School of Advanced Materials, Peking University Shenzhen Graduate School, 6School of Metallurgy, Northeastern University, 7Department of Chemical Engineering, University of California-Santa Barbara Here, we present a protocol for typical experiments of soft X-ray absorption spectroscopy (sXAS) and resonant inelastic X-ray scattering (RIXS) with applications in battery material studies.
Other articles by Kehua Dai on PubMed
Modification of Transition-Metal Redox by Interstitial Water in Hexacyanometalate Electrodes for Sodium-Ion Batteries Journal of the American Chemical Society. | Pubmed ID: 29169239 A sodium-ion battery (SIB) solution is attractive for grid-scale electrical energy storage. Low-cost hexacyanometalate is a promising electrode material for SIBs because of its easy synthesis and open framework. Most hexacyanometalate-based SIBs work with aqueous electrolyte, and interstitial water in the material has been found to strongly affect the electrochemical profile, but the mechanism remains elusive. Here we provide a comparative study of the transition-metal redox in hexacyanometalate electrodes with and without interstitial water based on soft X-ray absorption spectroscopy and theoretical calculations. We found distinct transition-metal redox sequences in hydrated and anhydrated NaMnFe(CN)·zHO. The Fe and Mn redox in hydrated electrodes are separated and are at different potentials, leading to two voltage plateaus. On the contrary, mixed Fe and Mn redox in the same potential range is found in the anhydrated system. This work reveals for the first time how transition-metal redox in batteries is strongly affected by interstitial molecules that are seemingly spectators. The results suggest a fundamental mechanism based on three competing factors that determine the transition-metal redox potentials. Because most hexacyanometalate electrodes contain water, this work directly reveals the mechanism of how interstitial molecules could define the electrochemical profile, especially for electrodes based on transition-metal redox with well-defined spin states.