All Publications

  • Dissolution of the Solid Electrolyte Interphase and Its Effects on Lithium Metal Anode Cyclability. Journal of the American Chemical Society Sayavong, P., Zhang, W., Oyakhire, S. T., Boyle, D. T., Chen, Y., Kim, S. C., Vilá, R. A., Holmes, S. E., Kim, M. S., Bent, S. F., Bao, Z., Cui, Y. 2023


    At >95% Coulombic efficiencies, most of the capacity loss for Li metal anodes (LMAs) is through the formation and growth of the solid electrolyte interphase (SEI). However, the mechanism through which this happens remains unclear. One property of the SEI that directly affects its formation and growth is the SEI's solubility in the electrolyte. Here, we systematically quantify and compare the solubility of SEIs derived from ether-based electrolytes optimized for LMAs using in-operando electrochemical quartz crystal microbalance (EQCM). A correlation among solubility, passivity, and cyclability established in this work reveals that SEI dissolution is a major contributor to the differences in passivity and electrochemical performance among battery electrolytes. Together with our EQCM, X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) spectroscopy results, we show that solubility depends on not only the SEI's composition but also the properties of the electrolyte. This provides a crucial piece of information that could help minimize capacity loss due to SEI formation and growth during battery cycling and aging.

    View details for DOI 10.1021/jacs.3c03195

    View details for PubMedID 37220230

  • LiH formation and its impact on Li batteries revealed by cryogenic electron microscopy. Science advances Vilá, R. A., Boyle, D. T., Dai, A., Zhang, W., Sayavong, P., Ye, Y., Yang, Y., Dionne, J. A., Cui, Y. 2023; 9 (12): eadf3609


    Little is known about how evolved hydrogen affects the cycling of Li batteries. Hypotheses include the formation of LiH in the solid-electrolyte interphase (SEI) and dendritic growth of LiH. Here, we discover that LiH formation in Li batteries likely follows a different pathway: Hydrogen evolved during cycling reacts to nucleate and grow LiH within already deposited Li metal, consuming active Li. We provide the evidence that LiH formed in Li batteries electrically isolates active Li from the current collector that degrades battery capacity. We detect the coexistence of Li metal and LiH also on graphite and silicon anodes, showing that LiH forms in most Li battery anode chemistries. Last, we find that LiH has its own SEI layer that is chemically and structurally distinct from the SEI on Li metal. Our results highlight the formation mechanism and chemical origins of LiH, providing critical insight into how to prevent its formation.

    View details for DOI 10.1126/sciadv.adf3609

    View details for PubMedID 36961896

  • Revealing the Multifunctions of Li3N in the Suspension Electrolyte for Lithium Metal Batteries. ACS nano Kim, M. S., Zhang, Z., Wang, J., Oyakhire, S. T., Kim, S. C., Yu, Z., Chen, Y., Boyle, D. T., Ye, Y., Huang, Z., Zhang, W., Xu, R., Sayavong, P., Bent, S. F., Qin, J., Bao, Z., Cui, Y. 2023


    Inorganic-rich solid-electrolyte interphases (SEIs) on Li metal anodes improve the electrochemical performance of Li metal batteries (LMBs). Therefore, a fundamental understanding of the roles played by essential inorganic compounds in SEIs is critical to realizing and developing high-performance LMBs. Among the prevalent SEI inorganic compounds observed for Li metal anodes, Li3N is often found in the SEIs of high-performance LMBs. Herein, we elucidate new features of Li3N by utilizing a suspension electrolyte design that contributes to the improved electrochemical performance of the Li metal anode. Through empirical and computational studies, we show that Li3N guides Li electrodeposition along its surface, creates a weakly solvating environment by decreasing Li+-solvent coordination, induces organic-poor SEI on the Li metal anode, and facilitates Li+ transport in the electrolyte. Importantly, recognizing specific roles of SEI inorganics for Li metal anodes can serve as one of the rational guidelines to design and optimize SEIs through electrolyte engineering for LMBs.

    View details for DOI 10.1021/acsnano.2c12470

    View details for PubMedID 36700841

  • Correlating the Formation Protocols of Solid Electrolyte Interphases with Practical Performance Metrics in Lithium Metal Batteries ACS ENERGY LETTERS Oyakhire, S. T., Zhang, W., Yu, Z., Holmes, S. E., Sayavong, P., Kim, S., Boyle, D. T., Kim, M., Zhang, Z., Cui, Y., Bent, S. F. 2023: 869-877
  • Investigating the Cyclability and Stability at the Interfaces of Composite Solid Electrolytes in Li Metal Batteries. ACS applied materials & interfaces Holmes, S. E., Liu, F., Zhang, W., Sayavong, P., Oyakhire, S. T., Cui, Y. 2022


    Despite the fact that much work has been dedicated to finding the ideal additive for composite solid electrolytes (CSEs) for lithium-based solid-state batteries, little is known about the properties of a CSE that enable stable cycling with a lithium metal anode. In this work, we use three CSEs based on lithium nitride (Li3N), a fast lithium-ion conductor, and lithium hydroxide (LiOH) to investigate the properties and interfacial interactions that impact the cyclability of CSEs. We present a method for stabilizing Li3N with a shell of LiOH, and we incorporate Li3N, core-shell particles, and LiOH into CSEs using polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide. Through improved interfacial chemistry, CSEs with core-shell particles have superior electrochemical cycling performance compared to those with unprotected Li3N in symmetric Li-Li cells. This CSE features a high ionic conductivity of 0.66 mS cm-1 at 60 °C, a high critical current density of 1.2 mA cm-2, and a wide voltage window of 0-5.1 V. Full cells with the core-shell CSE and lithium iron phosphate cathodes exhibit stable cycling and high reversible specific capacities in cells as high as 2.5 mAh cm-2. We report that the improved ionic conductivity and amorphous PEO content have a limited effect on the solid-state electrolyte performance, while improving the electrolyte-Li metal anode interface is key to cycling longevity.

    View details for DOI 10.1021/acsami.2c14677

    View details for PubMedID 36416366

  • Correlating Kinetics to Cyclability Reveals Thermodynamic Origin of Lithium Anode Morphology in Liquid Electrolytes. Journal of the American Chemical Society Boyle, D. T., Kim, S. C., Oyakhire, S. T., Vila, R. A., Huang, Z., Sayavong, P., Qin, J., Bao, Z., Cui, Y. 2022


    The rechargeability of lithium metal batteries strongly depends on the electrolyte. The uniformity of the electroplated Li anode morphology underlies this dependence, so understanding the main drivers of uniform plating is critical for further electrolyte discovery. Here, we correlate electroplating kinetics with cyclability across several classes of electrolytes to reveal the mechanistic influence electrolytes have on morphology. Fast charge-transfer kinetics at fresh Li-electrolyte interfaces correlate well with uniform morphology and cyclability, whereas the resistance of Li+ transport through the solid electrolyte interphase (SEI) weakly correlates with cyclability. These trends contrast with the conventional thought that Li+ transport through the electrolyte or SEI is the main driver of morphological differences between classes of electrolytes. Relating these trends to Li+ solvation, Li nucleation, and the charge-transfer mechanism instead suggests that the Li/Li+ equilibrium potential and the surface energy─thermodynamic factors modulated by the strength of Li+ solvation─underlie electrolyte-dependent trends of Li morphology. Overall, this work provides an insight for discovering functional electrolytes, tuning kinetics in batteries, and explaining why weakly solvating fluorinated electrolytes favor uniform Li plating.

    View details for DOI 10.1021/jacs.2c08182

    View details for PubMedID 36318744

  • Resolving Current-Dependent Regimes of Electroplating Mechanisms for Fast Charging Lithium Metal Anodes. Nano letters Boyle, D. T., Li, Y., Pei, A., Vila, R. A., Zhang, Z., Sayavong, P., Kim, M. S., Huang, W., Wang, H., Liu, Y., Xu, R., Sinclair, R., Qin, J., Bao, Z., Cui, Y. 2022


    Poor fast-charge capabilities limit the usage of rechargeable Li metal anodes. Understanding the connection between charging rate, electroplating mechanism, and Li morphology could enable fast-charging solutions. Here, we develop a combined electroanalytical and nanoscale characterization approach to resolve the current-dependent regimes of Li plating mechanisms and morphology. Measurement of Li+ transport through the solid electrolyte interphase (SEI) shows that low currents induce plating at buried Li||SEI interfaces, but high currents initiate SEI-breakdown and plating at fresh Li||electrolyte interfaces. The latter pathway can induce uniform growth of {110}-faceted Li at extremely high currents, suggesting ion-transport limitations alone are insufficient to predict Li morphology. At battery relevant fast-charging rates, SEI-breakdown above a critical current density produces detrimental morphology and poor cyclability. Thus, prevention of both SEI-breakdown and slow ion-transport in the electrolyte is essential. This mechanistic insight can inform further electrolyte engineering and customization of fast-charging protocols for Li metal batteries.

    View details for DOI 10.1021/acs.nanolett.2c02792

    View details for PubMedID 36214378