However, a wide range of interfacial challenges including dendritic growth, [2] electrolyte consumption, [3] and dead metal formation [4] challenge the performance and safety of Li metal anodes in liquid electrolyte cells. Solid-state batteries (SSBs), that pair the Li metal with an inorganic solid electrolyte (SE) can potentially address these limitations, while offering high energy and power densities. [5] Despite the major advantages of SEs including non-flammability and minimal concentration polarization, the development of practical SSBs still requires overcoming fundamental challenges related to electrochemo-mechanics, interface morphology and transport. [6] Li filament propagation and internal short-circuit has been observed across several SEs (e.g.
Solid-state batteries (SSBs) employing a lithium metal anode are a promising candidate for next-generation energy storage systems, delivering higher power and energy densities. Interfacial instabilities due to non-uniform electrodeposition at the anode−solid electrolyte (SE) interface pose major constraints on the safety and endurance of SSBs. In this regard, non-uniform kinetic interactions at the anode−SE interface which are derived from cathode microstructural heterogeneity can have significant impact on anode stability. In this work, we present a comprehensive insight into microstructural heterogeneity-driven cathode−anode cross-talk and delineate the role of cathode architecture and SE separator design in dictating reaction heterogeneity at the anode−SE interface. We show that intrinsic and extrinsic parameters, such as cathode loading, separator thickness, particle morphologies of active material and SE, and temperature can have significant impact on reaction heterogeneity at the anode−SE interface and thus govern anode stability. Tradeoff between energy density and anode stability while achieving higher cathode loading and thinner SE separators is highlighted, and potential strategies to mitigate this problem are discussed. This work provides fundamental insights into cathode−anode cross-talk involving interfacial heterogeneities and enhancement in energy densities of SSBs via electrode engineering.
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.
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 interaction of electrode/electrolyte interfaces result in non-uniform 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 (SEs) 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. Lastly, 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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