Stanford Advisors

  • Yi Cui, Postdoctoral Faculty Sponsor
  • Yi Cui, Postdoctoral Research Mentor

All Publications

  • Electrolyte-Resistant Dual Materials for the Synergistic Safety Enhancement of Lithium-Ion Batteries. Nano letters Chou, L., Ye, Y., Lee, H. K., Huang, W., Xu, R., Gao, X., Chen, R., Wu, F., Tsung, C., Cui, Y. 2021


    Safety issues associated with lithium-ion batteries are of major concern, especially with the ever-growing demand for higher-energy-density storage devices. Although flame retardants (FRs) added to electrolytes can reduce fire hazards, large amounts of FRs are required and they severely deteriorate battery performance. Here, we report a feasible method to balance flame retardancy and electrochemical performance by coating an electrolyte-insoluble FR on commercial battery separators. By integrating dual materials via a two-pronged mechanism, the quantity of FR required could be limited to an ultrathin coating layer (4 mum) that rarely influences electrochemical performance. The developed composite separator has a four-times better flame retardancy than conventional polyolefin separators in full pouch cells. Additionally, this separator can be fabricated easily on a large scale for industrial applications. High-energy-density batteries (2 Ah) were assembled to demonstrate the scaling of the composite separator and to confirm its enhanced safety through nail penetration tests.

    View details for DOI 10.1021/acs.nanolett.0c04568

    View details for PubMedID 33596654

  • Computational Modeling of Heterogeneity of Stress, Charge, and Cyclic Damage in Composite Electrodes of Li-Ion Batteries JOURNAL OF THE ELECTROCHEMICAL SOCIETY Liu, P., Xu, R., Liu, Y., Lin, F., Zhao, K. 2020; 167 (4)
  • Charge distribution guided by grain crystallographic orientations in polycrystalline battery materials. Nature communications Xu, Z., Jiang, Z., Kuai, C., Xu, R., Qin, C., Zhang, Y., Rahman, M. M., Wei, C., Nordlund, D., Sun, C., Xiao, X., Du, X., Zhao, K., Yan, P., Liu, Y., Lin, F. 2020; 11 (1): 83


    Architecting grain crystallographic orientation can modulate charge distribution and chemomechanical properties for enhancing the performance of polycrystalline battery materials. However, probing the interplay between charge distribution, grain crystallographic orientation, and performance remains a daunting challenge. Herein, we elucidate the spatially resolved charge distribution in lithium layered oxides with different grain crystallographic arrangements and establish a model to quantify their charge distributions. While the holistic "surface-to-bulk" charge distribution prevails in polycrystalline particles, the crystallographic orientation-guided redox reaction governs the charge distribution in the local charged nanodomains. Compared to the randomly oriented grains, the radially aligned grains exhibit a lower cell polarization and higher capacity retention upon battery cycling. The radially aligned grains create less tortuous lithium ion pathways, thus improving the charge homogeneity as statistically quantified from over 20 million nanodomains in polycrystalline particles. This study provides an improved understanding of the charge distribution and chemomechanical properties of polycrystalline battery materials.

    View details for DOI 10.1038/s41467-019-13884-x

    View details for PubMedID 31913275

  • Heterogeneous damage in Li-ion batteries: Experimental analysis and theoretical modeling JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS Xu, R., Yang, Y., Yin, F., Liu, P., Cloetens, P., Liu, Y., Lin, F., Zhao, K. 2019; 129: 160–83
  • Quantification of Heterogeneous Degradation in Li-Ion Batteries ADVANCED ENERGY MATERIALS Yang, Y., Xu, R., Zhang, K., Lee, S., Mu, L., Liu, P., Waters, C. K., Spence, S., Xu, Z., Wei, C., Kautz, D. J., Yuan, Q., Dong, Y., Yu, Y., Xiao, X., Lee, H., Pianetta, P., Cloetens, P., Lee, J., Zhao, K., Lin, F., Liu, Y. 2019; 9 (25)
  • High-Voltage Charging-Induced Strain, Heterogeneity, and Micro-Cracks in Secondary Particles of a Nickel-Rich Layered Cathode Material ADVANCED FUNCTIONAL MATERIALS Mao, Y., Wang, X., Xia, S., Zhang, K., Wei, C., Bak, S., Shadike, Z., Liu, X., Yang, Y., Xu, R., Pianetta, P., Ermon, S., Stavitski, E., Zhao, K., Xu, Z., Lin, F., Yang, X., Hu, E., Liu, Y. 2019; 29 (18)
  • Oxygen Release Induced Chemomechanical Breakdown of Layered Cathode Materials NANO LETTERS Mu, L., Lin, R., Xu, R., Han, L., Xia, S., Sokaras, D., Steiner, J. D., Weng, T., Nordlund, D., Doeff, M. M., Liu, Y., Zhao, K., Xin, H. L., Lin, F. 2018; 18 (5): 3241–49


    Chemical and mechanical properties interplay on the nanometric scale and collectively govern the functionalities of battery materials. Understanding the relationship between the two can inform the design of battery materials with optimal chemomechanical properties for long-life lithium batteries. Herein, we report a mechanism of nanoscale mechanical breakdown in layered oxide cathode materials, originating from oxygen release at high states of charge under thermal abuse conditions. We observe that the mechanical breakdown of charged Li1- xNi0.4Mn0.4Co0.2O2 materials proceeds via a two-step pathway involving intergranular and intragranular crack formation. Owing to the oxygen release, sporadic phase transformations from the layered structure to the spinel and/or rocksalt structures introduce local stress, which initiates microcracks along grain boundaries and ultimately leads to the detachment of primary particles, i.e., intergranular crack formation. Furthermore, intragranular cracks (pores and exfoliations) form, likely due to the accumulation of oxygen vacancies and continuous phase transformations at the surfaces of primary particles. Finally, finite element modeling confirms our experimental observation that the crack formation is attributable to the formation of oxygen vacancies, oxygen release, and phase transformations. This study is designed to directly observe the chemomechanical behavior of layered oxide cathode materials and provides a chemical basis for strengthening primary and secondary particles by stabilizing the oxygen anions in the lattice.

    View details for DOI 10.1021/acs.nanolett.8b01036

    View details for Web of Science ID 000432093200071

    View details for PubMedID 29667835