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1. In situ characterizations of solid–solid interfaces in solid‐state batteries using synchrotron X‐ray techniques

   https://doi.org/10.1002/cey2.131  

   Lucero, Marcos; Qiu, Shen; Feng, Zhenxing (July 2021, Carbon Energy)

   Abstract The solid–solid electrode–electrolyte interface represents an important component in solid‐state batteries (SSBs), as ionic diffusion, reaction, transformation, and restructuring could all take place. As these processes strongly influence the battery performance, studying the evolution of the solid–solid interfaces, particularly in situ during battery operation, can provide insights to establish the structure–property relationship for SSBs. Synchrotron X‐ray techniques, owing to their unique penetration power and diverse approaches, are suitable to investigate the buried interfaces and examine structural, compositional, and morphological changes. In this review, we will discuss various surface‐sensitive synchrotron‐based scattering, spectroscopy, and imaging methods for the in situ characterization of solid–solid interfaces and how this information can be correlated to the electrochemical properties of SSBs. The goal is to overview the advantages and disadvantages of each technique by highlighting representative examples, so that similar strategies can be applied by battery researchers and beyond to study similar solid‐solid interface systems. 

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2. Particle-hole symmetry and the reentrant integer quantum Hall Wigner solid

   https://doi.org/10.1038/s42005-021-00709-x  

   Shingla, Vidhi; Myers, Sean A.; Pfeiffer, Loren N.; Baldwin, Kirk W.; Csáthy, Gábor A. (December 2021, Communications Physics)

   Abstract The interplay of strong Coulomb interactions and of topology is currently under intense scrutiny in various condensed matter and atomic systems. One example of this interplay is the phase competition of fractional quantum Hall states and the Wigner solid in the two-dimensional electron gas. Here we report a Wigner solid at ν  = 1.79 and its melting due to fractional correlations occurring at ν  = 9/5. This Wigner solid, that we call the reentrant integer quantum Hall Wigner solid, develops in a range of Landau level filling factors that is related by particle-hole symmetry to the so called reentrant Wigner solid. We thus find that the Wigner solid in the GaAs/AlGaAs system straddles the partial filling factor 1/5 not only at the lowest filling factors, but also near ν  = 9/5. Our results highlight the particle-hole symmetry as a fundamental symmetry of the extended family of Wigner solids and paint a complex picture of the competition of the Wigner solid with fractional quantum Hall states. 

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3. Kinetics or Transport: Whither Goes the Solid-State Battery Cathode?

   https://doi.org/10.1021/acsami.2c04962  

   Naik, Kaustubh G.; Vishnugopi, Bairav S.; Mukherjee, Partha P. (June 2022, ACS Applied Materials & Interfaces)

   Solid-state batteries (SSBs) hold the potential to enhance the energy density, power density, and safety of conventional lithium-ion batteries. The theoretical promise of SSBs is predicated on the mechanistic design and comprehensive analysis of various solid–solid interfaces and microstructural features within the system. The spatial arrangement and composition of constituent phases (e.g., active material, solid electrolyte, binder) in the solid-state cathode dictate critical characteristics such as solid–solid point contacts or singularities within the microstructure and percolation pathways for ionic/electronic transport. In this work, we present a comprehensive mesoscale discourse to interrogate the underlying microstructure-coupled kinetic-transport interplay and concomitant modes of resistances that evolve during electrochemical operation of SSBs. Based on a hierarchical physics-based analysis, the mechanistic implications of solid–solid point contact distribution and intrinsic transport pathways on the kinetic heterogeneity is established. Toward designing high-energy-density SSB systems, the fundamental correlation between active material loading, electrode thickness and electrochemical response has been delineated. We examine the paradigm of carbon-binder free cathodes and identify design criteria that can facilitate enhanced performance with such electrode configurations. A mechanistic design map highlighting the dichotomy in kinetic and ionic/electronic transport limitations that manifest at various SSB cathode microstructural regimes is established. 

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4. Electro-Chemo-Mechanical Challenges and Perspective in Lithium Metal Batteries

   https://doi.org/10.1115/1.4057039  

   Naik, Kaustubh G.; Vishnugopi, Bairav S.; Datta, Joy; Datta, Dibakar; Mukherjee, Partha P. (January 2023, Applied Mechanics Reviews)

   Abstract The development of next-generation batteries, utilizing electrodes with high capacities and power densities requires a comprehensive understanding and precise control of material interfaces and architectures. Electro-chemo-mechanics plays an integral role in the morphological evolution and stability of such complex interfaces. Volume changes in electrode materials and the chemical interactions of electrode/electrolyte interfaces result in nonuniform stress fields and structurally different interphases, fundamentally affecting the underlying transport and reaction kinetics. The origin of this mechanistic coupling and its implications on degradation is uniquely dependent on the interface characteristics. In this review, the distinct nature of chemo–mechanical coupling and failure mechanisms at solid–liquid interfaces and solid–solid interfaces is analyzed. For lithium metal electrodes, the critical role of surface/microstructural heterogeneities on the solid electrolyte interphase (SEI) stability and dendrite growth in liquid electrolytes, and on the onset of contact loss and filament penetration with solid electrolytes is summarized. With respect to composite electrodes, key differences in the microstructure-coupled electro-chemo-mechanical attributes of intercalation- and conversion-based chemistries are delineated. Moving from liquid to solid electrolytes in such cathodes, we highlight the significant impact of solid–solid point contacts on transport/mechanical response, electrochemical performance, and failure modes such as particle cracking and delamination. Finally, we present our perspective on future research directions and opportunities to address the underlying electro-chemo-mechanical challenges for enabling next-generation lithium metal batteries. 

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5. Opportunities Using Boron to Direct Reactivity in the Organic Solid State

   https://doi.org/10.1055/s-0040-1707297  

   Campillo-Alvarado, Gonzalo; MacGillivray, Leonard R. (April 2021, Synlett)

   null (Ed.)

   Abstract This Account describes work by our research group that highlights opportunities to utilize organoboron molecules to direct chemical reactivity in the organic solid state. Specifically, we convey a previously unexplored use of hydrogen bonding of boronic acids and boron coordination in boronic esters to achieve [2+2]-photocycloadditions in crystalline solids. Organoboron molecules act as templates or ‘shepherds’ to organize alkenes in a suitable geometry to undergo regio- and stereoselective [2+2]-photocycloadditions in quantitative yields. We also provide a selection of publications that served as an inspiration for our strategies and offer challenges and opportunities for future developments of boron in the field of materials and solid-state chemistry. 1 Introduction 1.1 Template Strategy for [2+2]-Photocycloadditions in the Solid State 2 Boronic Acids as Templates for [2+2]-Photocycloadditions in the Solid State 2.1 Supramolecular Catalysis of [2+2]-Photocycloadditions in the Solid State Using Boronic Acids 3 Boronic Esters as Templates for [2+2]-Photocycloadditions in the Solid State 3.1 Application of Photoproducts: Separation of Thiophene from Benzene through Crystallization 3.2 Crystal Reactivity of B←N-Bonded Adducts: The Case of Styryl­thiophenes 4 Conclusions and Perspectives 

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