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1. Coordinated mapping of Li ⁺ flux and electron transfer reactivity during solid-electrolyte interphase formation at a graphene electrode

   https://doi.org/10.1039/c9an02637a  

   Gossage, Zachary T. ; Hui, Jingshu ; Sarbapalli, Dipobrato ; Rodríguez-López, Joaquín ( March 2020 , The Analyst)

   Interphases formed at battery electrodes are key to enabling energy dense charge storage by acting as protection layers and gatekeeping ion flux into and out of the electrodes. However, our current understanding of these structures and how to control their properties is still limited due to their heterogenous structure, dynamic nature, and lack of analytical techniques to probe their electronic and ionic properties in situ . In this study, we used a multi-functional scanning electrochemical microscopy (SECM) technique based on an amperometric ion-selective mercury disc-well (HgDW) probe for spatially-resolving changes in interfacial Li + during solid electrolyte interphase (SEI) formation and for tracking its relationship to the electronic passivation of the interphase. We focused on multi-layer graphene (MLG) as a model graphitic system and developed a method for ion-flux mapping based on pulsing the substrate at multiple potentials with distinct behavior ( e.g. insertion–deinsertion). By using a pulsed protocol, we captured the localized uptake of Li + at the forming SEI and during intercalation, creating activity maps along the edge of the MLG electrode. On the other hand, a redox probe showed passivation by the interphase at the same locations, thus enabling correlations between ion and electron transfer. Our analyticalmore »method provided direct insight into the interphase formation process and could be used for evaluating dynamic interfacial phenomena and improving future energy storage technologies.« less
2. Co-intercalation-free ether electrolytes for graphitic anodes in lithium-ion batteries

   https://doi.org/10.1039/D2EE01489K  

   Ma, Peiyuan ; Mirmira, Priyadarshini ; Eng, Peter J. ; Son, Seoung-Bum ; Bloom, Ira D. ; Filatov, Alexander S. ; Amanchukwu, Chibueze V. ( November 2022 , Energy & Environmental Science)

   Carbonate-based electrolytes are widely used in Li-ion batteries but are limited by a small operating temperature window and poor cycling with silicon-containing graphitic anodes. The lack of non-carbonate electrolyte alternatives such as ether-based electrolytes is due to undesired solvent co-intercalation that occurs with graphitic anodes. Here, we show that fluoroethers are the first class of ether solvents to intrinsically support reversible lithium-ion intercalation into graphite without solvent co-intercalation at conventional salt concentrations. In full cells using a graphite anode, they enable 10-fold higher energy densities compared to conventional ethers, and better thermal stability over carbonate electrolytes (operation up to 60 °C) by producing a robust solvent-derived solid electrolyte interphase (SEI). As single-solvent–single-salt electrolytes, they remarkably outperform carbonate electrolytes with fluoroethylene carbonate (FEC) and vinylene carbonate (VC) additives when cycled with graphite–silicon composite anodes. Our molecular design strategy opens a new class of electrolytes that can enable next generation Li-ion batteries with higher energy density and a wider working temperature window.
3. The effect of local lithium surface chemistry and topography on solid electrolyte interphase composition and dendrite nucleation

   https://doi.org/10.1039/C9TA03371H  

   Meyerson, Melissa L. ; Sheavly, Jonathan K. ; Dolocan, Andrei ; Griffin, Monroe P. ; Pandit, Anish H. ; Rodriguez, Rodrigo ; Stephens, Ryan M. ; Vanden Bout, David A. ; Heller, Adam ; Mullins, C. Buddie ( June 2019 , Journal of Materials Chemistry A)

   With more than 10 times the capacity of the graphite used in current commercial batteries, lithium metal is ideal for a high-capacity battery anode; however, lithium metal electrodes suffer from safety and efficiency problems that prevent their wide industrial adoption. Their intrinsic high reactivity towards most liquid organic electrolytes leads to lithium loss and dendrite growth, which result in poor efficiency and short circuiting. However, the multitude of factors that contribute to dendrite formation make determining a nucleation mechanism extremely difficult. Here, we study the intricate science of dendrite nucleation on metallic lithium by using an array of analytical techniques that provide simultaneous ultra-high spatial sensitivity and chemical selectivity. Our results reveal a 3D picture of the chemical make-up of the native Li surface and the resulting solid electrolyte interphase (SEI) with better than 200 nm resolution. We find that, contrary to the general understanding, the initial surface chemistry, not the topography, is the dominant factor leading to dendrite nucleation. Specifically, inhomogeneously distributed organic material in the native surface leads to inhomogeneously dispersed LiF-rich SEI regions where dendrite nucleation is favored. This has significant implications for battery research as it elucidates a mechanism for inhomogeneous SEI formation, something that ismore »accepted, but not well understood, and highlights the importance of Li surface preparation for experimental studies, which is implicit in battery research, but not directly addressed in the literature. By homogenizing the initial lithium surface composition, and thus the SEI composition, we increase the number of dendrite nucleation sites and thereby decrease the dendrite size, which significantly increases the electrode lifetime.« less
4. The role of the solid electrolyte interphase layer in preventing Li dendrite growth in solid-state batteries

   https://doi.org/10.1039/c8ee00540k  

   Wu, Bingbin ; Wang, Shanyu ; Lochala, Joshua ; Desrochers, David ; Liu, Bo ; Zhang, Wenqing ; Yang, Jihui ; Xiao, Jie ( January 2018 , Energy & Environmental Science)

   Lithium (Li) metal anodes have regained intensive interest in recent years due to the ever-increasing demand for next-generation high energy battery technologies. Li metal, unfortunately, suffers from poor cycling stability and low efficiency as well as from the formation of dangerous Li dendrites, raising safety concerns. Utilizing solid-state electrolytes (SSEs) to prevent Li dendrite growth provides a promising approach to tackle the challenge. However, recent studies indicate that Li dendrites easily form at high current densities, which calls for full investigation of the fundamental mechanisms of Li dendrite formation within SSEs. Herein, the origin and evolution of Li dendrite growth through SSEs have been studied and compared by using Li 6.1 Ga 0.3 La 3 Zr 2 O 12 (LLZO) and NASICON-type Li 2 O–Al 2 O 3 –P 2 O 5 –TiO 2 –GeO 2 (LATP) pellets as the separators. We discover that a solid electrolyte interphase (SEI)-like interfacial layer between Li and SSE plays a critical role in alleviating the growth of dendritic Li, providing new insights into the interface between SSE and Li metal to enable future all solid-state batteries.
5. Nernstian Li ⁺ intercalation into few-layer graphene and its use for the determination of K ⁺ co-intercalation processes

   https://doi.org/10.1039/D0SC03226C  

   Hui, Jingshu ; Nijamudheen, A. ; Sarbapalli, Dipobrato ; Xia, Chang ; Qu, Zihan ; Mendoza-Cortes, Jose L. ; Rodríguez-López, Joaquín ( January 2021 , Chemical Science)

   Alkali ion intercalation is fundamental to battery technologies for a wide spectrum of potential applications that permeate our modern lifestyle, including portable electronics, electric vehicles, and the electric grid. In spite of its importance, the Nernstian nature of the charge transfer process describing lithiation of carbon has not been described previously. Here we use the ultrathin few-layer graphene (FLG) with micron-sized grains as a powerful platform for exploring intercalation and co-intercalation mechanisms of alkali ions with high versatility. Using voltammetric and chronoamperometric methods and bolstered by density functional theory (DFT) calculations, we show the kinetically facile co-intercalation of Li + and K + within an ultrathin FLG electrode. While changes in the solution concentration of Li + lead to a displacement of the staging voltammetric signature with characteristic slopes ca. 54–58 mV per decade, modification of the K + /Li + ratio in the electrolyte leads to distinct shifts in the voltammetric peaks for (de)intercalation, with a changing slope as low as ca. 30 mV per decade. Bulk ion diffusion coefficients in the carbon host, as measured using the potentiometric intermittent titration technique (PITT) were similarly sensitive to solution composition. DFT results showed that co-intercalation of Li + and Kmore »+ within the same layer in FLG can form thermodynamically favorable systems. Calculated binding energies for co-intercalation systems increased with respect to the area of Li + -only domains and decreased with respect to the concentration of –K–Li– phases. While previous studies of co-intercalation on a graphitic anode typically focus on co-intercalation of solvents and one particular alkali ion, this is to the best of our knowledge the first study elucidating the intercalation behavior of two monovalent alkali ions. This study establishes ultrathin graphitic electrodes as an enabling electroanalytical platform to uncover thermodynamic and kinetic processes of ion intercalation with high versatility.« less