Professional Education

  • B.S., Nanjing University, Physics (2014)
  • Ph.D., Northwestern University, Applied Physics (2019)

Stanford Advisors

Current Research and Scholarly Interests

Dr. Xu's research focuses on a fundamental understanding of charge transport and the related electro-chemo-mechanical mechanism in mixed electronic and ionic conductors via methods of operando local multimodal characterization. This encompasses a broad class of systems in the fields such as solid oxide fuel cells, solid state batteries and memristors, with research areas including charge transport theory, interface characterization, and novel device fabrication.


  • Failure Mechanism in Solid State Batteries, Stanford University (11/1/2019 - Present)


    Stanford, CA

  • Charge Transport across Single Grain Boundaries in Oxide Electrolytes, Northwestern University (9/1/2014 - 9/6/2019)


    Evanston, IL

All Publications

  • Author Correction: Mechanical regulation of lithium intrusion probability in garnet solid electrolytes [Jan, 10.1038/s41560-022-01186-4, 2023] NATURE ENERGY McConohy, G., Xu, X., Cui, T., Barks, E., Wang, S., Kaeli, E., Melamed, C., Gu, X., Chueh, W. C. 2023
  • Applied stress can control lithium intrusions in solid electrolytes NATURE ENERGY McConohy, G., Xu, X. 2023
  • Mechanical regulation of lithium intrusion probability in garnet solid electrolytes NATURE ENERGY McConohy, G., Xu, X., Cui, T., Barks, E., Wang, S., Kaeli, E., Melamed, C., Gu, X., Chueh, W. C. 2023
  • Persistent and partially mobile oxygen vacancies in Li-rich layered oxides NATURE ENERGY Csernica, P. M., Kalirai, S. S., Gent, W. E., Lim, K., Yu, Y., Liu, Y., Ahn, S., Kaeli, E., Xu, X., Stone, K. H., Marshall, A. F., Sinclair, R., Shapiro, D. A., Toney, M. F., Chueh, W. C. 2021
  • Local Multimodal Electro-Chemical-Structural Characterization of Solid-Electrolyte Grain Boundaries ADVANCED ENERGY MATERIALS Xu, X., Carr, C., Chen, X., Myers, B. D., Huang, R., Yuan, W., Choi, S., Yi, D., Phatak, C., Haile, S. M. 2021; 11 (10)
  • Quantifying leakage fields at ionic grain boundaries using off-axis electron holography JOURNAL OF APPLIED PHYSICS Xu, X., Barrows, F., Dravid, V. P., Haile, S. M., Phatak, C. 2020; 128 (21)

    View details for DOI 10.1063/5.0031233

    View details for Web of Science ID 000597309900001

  • Variability and origins of grain boundary electric potential detected by electron holography and atom-probe tomography NATURE MATERIALS Xu Xin, Liu Yuzi, Wang Jie, Isheim, D., Dravid, V. P., Phatak, C., Haile, S. M. 2020; 19 (8): 887-+


    A number of grain boundary phenomena in ionic materials, in particular, anomalous (either depressed or enhanced) charge transport, have been attributed to space charge effects. Developing effective strategies to manipulate transport behaviour requires deep knowledge of the origins of the interfacial charge, as well as its variability within a polycrystalline sample with millions of unique grain boundaries. Electron holography is a powerful technique uniquely suited for studying the electric potential profile at individual grain boundaries, whereas atom-probe tomography provides access to the chemical identify of essentially every atom at individual grain boundaries. Using these two techniques, we show here that the space charge potential at grain boundaries in lightly doped, high-purity ceria can vary by almost an order of magnitude. We further find that trace impurities (<25 ppm), rather than inherent thermodynamic factors, may be the ultimate source of grain boundary charge. These insights suggest chemical tunability of grain boundary transport properties.

    View details for DOI 10.1038/s41563-020-0656-1

    View details for Web of Science ID 000526218500002

    View details for PubMedID 32284599

  • Chemical surface exchange of oxygen on CeO2-delta in an O-2/H2O atmosphere PHYSICAL CHEMISTRY CHEMICAL PHYSICS Ji, H., Xu, X., Haile, S. M. 2017; 19 (43): 29287-29293


    The chemical surface reaction rate constant controlling the change of oxidation state of undoped ceria, kChem, was measured at 1400 °C in the range of (∼0 ≤ (pH2O/atm) ≤ 0.163(9)) and (10-3.85 ≤ (pO2/atm) ≤ 10-2.86) via the electrical conductivity relaxation method. In humidified atmospheres, kChem is fully described as the sum of kChem,O2 and kChem,H2O, which are, respectively, the rate constants for oxidation by O2 and by H2O alone. Using measurements under appropriately controlled gas conditions, the total rate constant is found to follow the correlation kChem/cm s-1 = 10-(1.35±0.07) × (pO2/atm)0.72±0.02 + 10-(3.85±0.03) × (pH2O/atm)0.36±0.03 where the pO2 and pH2O values of relevance are explicitly those of the final gas condition. The results suggest that at such high temperatures, the concentrations of surface adsorbed species are too low to influence the independent reaction pathways.

    View details for DOI 10.1039/c7cp05969h

    View details for Web of Science ID 000414773100030

    View details for PubMedID 29071321