Stanford Advisors

  • Yi Cui, Postdoctoral Faculty Sponsor

All Publications

  • Progressive and instantaneous nature of lithium nucleation discovered by dynamic and operando imaging SCIENCE ADVANCES Feng, G., Shi, Y., Jia, H., Risal, S., Yang, X., Ruchhoeft, P., Shih, W., Fan, Z., Xu, W., Shan, X. 2023; 9 (21): eadg6813


    The understanding of lithium (Li) nucleation and growth is important to design better electrodes for high-performance batteries. However, the study of Li nucleation process is still limited because of the lack of imaging tools that can provide information of the entire dynamic process. We developed and used an operando reflection interference microscope (RIM) that enables real-time imaging and tracking the Li nucleation dynamics at a single nanoparticle level. This dynamic and operando imaging platform provides us with critical capabilities to continuously monitor and study the Li nucleation process. We find that the formation of initial Li nuclei is not at the exact same time point, and Li nucleation process shows the properties of both progressive and instantaneous nucleation. In addition, the RIM allows us to track the individual Li nucleus's growth and extract spatially resolved overpotential map. The nonuniform overpotential map indicates that the localized electrochemical environments substantially influence the Li nucleation.

    View details for DOI 10.1126/sciadv.adg6813

    View details for Web of Science ID 001009447100006

    View details for PubMedID 37224260

    View details for PubMedCentralID PMC10208563

  • Imaging solid-electrolyte interphase dynamics using operando reflection interference microscopy NATURE NANOTECHNOLOGY Feng, G., Jia, H., Shi, Y., Yang, X., Liang, Y., Engelhard, M. H., Zhang, Y., Yang, C., Xu, K., Yao, Y., Xu, W., Shan, X. 2023; 18 (7): 780-+


    The quality of the solid-electrolyte interphase is crucial for the performance of most battery chemistries, but its formation dynamics during operation are not well understood due to a lack of reliable operando characterization techniques. Herein, we report a dynamic, non-invasive, operando reflection interference microscope to enable the real-time imaging of the solid-electrolyte interphase during its formation and evolution processes with high sensitivity. The stratified structure of the solid-electrolyte interphase formed during four distinct steps includes the emergence of a permanent inner inorganic layer enriched in LiF, a transient assembly of an interfacial electrified double layer and a consequent emergence of a temporary outer organic-rich layer whose presence is reversible with electrochemical cycling. Reflection interference microscope imaging reveals an inverse correlation between the thicknesses of two interphasial subcomponents, implying that the permanent inorganic-rich inner layer dictates the organic-rich outer layer formation and lithium nucleation. The real-time visualization of solid-electrolyte interphase dynamics provides a powerful tool for the rational design of battery interphases.

    View details for DOI 10.1038/s41565-023-01316-3

    View details for Web of Science ID 000931744100001

    View details for PubMedID 36759704

  • Three-dimensional Zn-based alloys for dendrite-free aqueous Zn battery in dual-cation electrolytes NATURE COMMUNICATIONS Tian, H., Feng, G., Wang, Q., Li, Z., Zhang, W., Lucero, M., Feng, Z., Wang, Z., Zhang, Y., Zhen, C., Gu, M., Shan, X., Yang, Y. 2022; 13 (1): 7922


    Aqueous zinc-ion batteries, in terms of integration with high safety, environmental benignity, and low cost, have attracted much attention for powering electronic devices and storage systems. However, the interface instability issues at the Zn anode caused by detrimental side reactions such as dendrite growth, hydrogen evolution, and metal corrosion at the solid (anode)/liquid (electrolyte) interface impede their practical applications in the fields requiring long-term performance persistence. Despite the rapid progress in suppressing the side reactions at the materials interface, the mechanism of ion storage and dendrite formation in practical aqueous zinc-ion batteries with dual-cation aqueous electrolytes is still unclear. Herein, we design an interface material consisting of forest-like three-dimensional zinc-copper alloy with engineered surfaces to explore the Zn plating/stripping mode in dual-cation electrolytes. The three-dimensional nanostructured surface of zinc-copper alloy is demonstrated to be in favor of effectively regulating the reaction kinetics of Zn plating/stripping processes. The developed interface materials suppress the dendrite growth on the anode surface towards high-performance persistent aqueous zinc-ion batteries in the aqueous electrolytes containing single and dual cations. This work remarkably enhances the fundamental understanding of dual-cation intercalation chemistry in aqueous electrochemical systems and provides a guide for exploring high-performance aqueous zinc-ion batteries and beyond.

    View details for DOI 10.1038/s41467-022-35618-2

    View details for Web of Science ID 000984474000019

    View details for PubMedID 36564385

    View details for PubMedCentralID PMC9789050

  • Probe the Localized Electrochemical Environment Effects and Electrode Reaction Dynamics for Metal Batteries using In Situ 3D Microscopy ADVANCED ENERGY MATERIALS Feng, G., Guo, J., Tian, H., Li, Z., Shi, Y., Li, X., Yang, X., Mayerich, D., Yang, Y., Shan, X. 2022; 12 (3)
  • Electrochemical Impedance Imaging on Conductive Surfaces ANALYTICAL CHEMISTRY Shi, Y., Feng, G., Li, X., Yang, X., Ghanim, A. H., Ruchhoeft, P., Jackson, D., Mubeen, S., Shan, X. 2021; 93 (36): 12320-12328


    Electrochemical impedance spectroscopy (EIS) is a powerful tool to measure and quantify the system impedance. However, EIS only provides an average result from the entire electrode surface. Here, we demonstrated a reflection impedance microscope (RIM) that allows us to image and quantify the localized impedance on conductive surfaces. The RIM is based on the sensitive dependence between the materials' optical properties, such as permittivity, and their local surface charge densities. The localized charge density variations introduced by the impedance measurements will lead to optical reflectivity changes on electrode surfaces. Our experiments demonstrated that reflectivity modulations are linearly proportional to the surface charge density on the electrode and the measurements show good agreement with the simple free electron gas model. The localized impedance distribution was successfully extracted from the reflectivity measurements together with the Randles equivalent circuit model. In addition, RIM is used to quantify the impedance on different conductive surfaces, such as indium tin oxide, gold film, and stainless steel electrodes. A polydimethylsiloxane-patterned electrode surface was used to demonstrate the impedance imaging capability of RIM. In the end, a single-cell impedance imaging was obtained by RIM.

    View details for DOI 10.1021/acs.analchem.1c02040

    View details for Web of Science ID 000696518100024

    View details for PubMedID 34460223

  • Stable, high-performance, dendrite-free, seawater-based aqueous batteries NATURE COMMUNICATIONS Tian, H., Li, Z., Feng, G., Yang, Z., Fox, D., Wang, M., Zhou, H., Zhai, L., Kushima, A., Du, Y., Feng, Z., Shan, X., Yang, Y. 2021; 12 (1): 237


    Metal anode instability, including dendrite growth, metal corrosion, and hetero-ions interference, occurring at the electrolyte/electrode interface of aqueous batteries, are among the most critical issues hindering their widespread use in energy storage. Herein, a universal strategy is proposed to overcome the anode instability issues by rationally designing alloyed materials, using Zn-M alloys as model systems (M = Mn and other transition metals). An in-situ optical visualization coupled with finite element analysis is utilized to mimic actual electrochemical environments analogous to the actual aqueous batteries and analyze the complex electrochemical behaviors. The Zn-Mn alloy anodes achieved stability over thousands of cycles even under harsh electrochemical conditions, including testing in seawater-based aqueous electrolytes and using a high current density of 80 mA cm-2. The proposed design strategy and the in-situ visualization protocol for the observation of dendrite growth set up a new milestone in developing durable electrodes for aqueous batteries and beyond.

    View details for DOI 10.1038/s41467-020-20334-6

    View details for Web of Science ID 000630190600001

    View details for PubMedID 33431888

    View details for PubMedCentralID PMC7801520

  • Gold-nanorod-enhanced Raman spectroscopy encoded micro-quartz pieces for the multiplex detection of biomolecules ANALYTICAL AND BIOANALYTICAL CHEMISTRY Wang, B., Guan, T., Jiang, J., He, Q., Chen, X., Feng, G., Lu, B., Zhou, X., He, Y. 2019; 411 (21): 5509-5518


    The rapid analysis and detection of biomolecules has become increasingly important in biological research. Hence, here we propose a novel suspension array method that is based on gold nanorod (AuNR)-enhanced Raman spectroscopy and uses micro-quartz pieces (MQPs) as microcarriers. AuNRs and Raman reporter molecules are coupled together by Au-S bonds to obtain surface-enhanced Raman scattering labels (SERS labels). The SERS labels are then assembled on the surfaces of the MQPs via electrostatic interactions, yielding encoded MQPs. Experimental results showed that the encoded MQPs could be decoded using a Raman spectrometer. A multiplex immunoassay experiment demonstrated the validity and specificity of these encoded MQPs when they were used for bioanalysis. In concentration gradient experiments, the proposed method was found to give a linear concentration response to the target biomolecule at target concentrations of 0.46875-30 nM, and the detection limit was calculated to be 1.78 nM. The proposed method utilizes MQPs as carriers rather than conventional microbeads, which allows the interference caused by the background fluorescence of microbeads to be eliminated. The fluorescence of the encoded MQPs can be simply, rapidly, and inexpensively quantified using fluorescence microscopy. By dividing the quantitative and qualitative detection of biomolecules into two independent channels, crosstalk between the encoded signal and the labeled signal is averted and high decoding accuracy and detection sensitivity are guaranteed. Graphical abstract.

    View details for DOI 10.1007/s00216-019-01929-5

    View details for Web of Science ID 000479055200017

    View details for PubMedID 31280475

  • Spectral-optical-tweezer-assisted fluorescence multiplexing system for QDs-encoded bead-array bioassay BIOSENSORS & BIOELECTRONICS He, Q., Chen, X., He, Y., Guan, T., Feng, G., Lu, B., Wang, B., Zhou, X., Hu, L., Cao, D. 2019; 129: 107-117


    As an efficient tool in the multiplexed detection of biomolecules, bead-array could achieve separation-free detection to multiple targets, making it suitable to analyze valuable and scarce samples like antigen and antibody from living organism. Herein, we propose a spectral-optical-tweezer-assisted fluorescence multiplexing system to analyze biomolecule-conjugated bead-array. Using optical tweezer, we trapped and locked beads at the focus to accept stimulation, offering a stable and optimized analysis condition. Moving the system focus and scanning the sample slide, we achieved emissions collection to QDs-encoded bead-array after the multiplexed detection. The emission spectra of fluorescence were collected and recorded by the spectrometer. By recognizing locations of decoding peaks and counting the intensities of label signals of emission spectra, we achieved qualitative and quantitative detection to targets. As proof-of-concept studies, we use this system to carry out multiplexed detection to various types of anti-IgG in the single sample and the detection limit reaches 1.52 pM with a linear range from 0.31 to 10 nM. Through further optimization of experimental conditions, we achieved specific detection to target IgG with sandwich method in human serum and the detection limit reaches as low as 0.23 pM with a linear range from 0.88 to 28 pM, validating the practical application of this method in real samples.

    View details for DOI 10.1016/j.bios.2019.01.004

    View details for Web of Science ID 000459524100016

    View details for PubMedID 30685705

  • Dual-spectra encoded suspension array using reversed-phase microemulsion UV curing and electrostatic self-assembling RSC ADVANCES Feng, G., He, Q., Xie, W., He, Y., Chen, X., Wang, B., Lu, B., Guan, T. 2018; 8 (38): 21272-21279


    The rapid growth of demand for high-throughput multiplexed biochips from modern biotechnology has led to growing interest in suspension array based on multi-channel encoded microbeads. We prepare dual-spectra encoded PEGDA microbeads (DSEPM) by reversed-phase microemulsion UV curing method and layer-by-layer electrostatic self-assembly method. Excitation of the synthesized DSEPM results in two spectra, including fluorescence spectra from quantum dots and laser induced breakdown spectra from nanoparticles with specific elements. With further surface modification and bio-probes grafting, we use DSEPM to carry a series of detection experiments of biomolecules. The adsorption experiment to two types of anti-IgG in mixture sample has demonstrated the availability of DSEPM in multiplexing. Then, the contrast experiment has verified the specificity of DSEPM in detection. Finally, we carry out the concentration gradient experiment and obtain the response curve to show the performance of DSEPM in quantitative analysis. The results indicate our method provide an effective way to improve multiplexed biochips with more coding capacity, accuracy and stability.

    View details for DOI 10.1039/c8ra02410c

    View details for Web of Science ID 000435576500022

    View details for PubMedID 35539940

    View details for PubMedCentralID PMC9080948