The widespread application of rechargeable batteries in portable electronics, electric vehicles, grid energy, and renewable energy storage necessitates high performance and cost-effective solutions. [1] To date, the vast majority of rechargeable battery products are based on the lithium-ion intercalation chemistry. [2] State-of-the-art commercial lithium-ion cells offer energy densities of %260 Wh Kg À1 (%680 Wh L À1 ), and long cycle life (several thousand cycles). [2] However, the Achilles heel for lithium-ion technology is cost. Lithium is a limited resource on the planet, and its price has reported to have increased by %738% since January 2021. [3] Consequently, lithium-ion battery cost is projected to rise to %$115 per kWh by 2023. [4] As an alternative to lithium, earthabundant, and cheaper metals such as aluminum (Al), calcium (Ca), magnesium (Mg), and zinc (Zn) have been actively researched in battery systems. [5][6][7][8][9][10][11] These metals are multivalent (carry two or more ionic charge) and hence one ion insertion will deliver two or more electrons per ion during battery operation. The main advantage of multivalent ions is that to achieve a certain specific capacity, the number of ions that are required to participate in the redox process is lower for multivalent as compared to monovalent ions. Therefore, multivalent ions offer the promise of improved performance and lower cost. However, the higher ionic charge of multivalent ions presents its own set of unique challenges. One obvious distinction between monovalent and multivalent ions is the difference in charge density (i.e., for similar ionic size, multivalent ions bear double, or triple the amount of monovalent ionic charge). The higher charge density of multivalent ions generates a stronger electric field which causes a bigger solvation sheath in the electrolyte (Figure 1a), which results in a higher "desolvation penalty" before insertion inside the electrode. Moreover, higher charge density multivalent ions strongly interact with ions in the intercalation host resulting in a relatively high migration barrier and slower diffusion kinetics (Figure 1b). It is also a considerable challenge to find durable intercalation materials for multivalent ions. As shown schematically in Figure 1c, often, multivalent ion insertion is responsible for mechanical degradation (stress-induced cracking) of the host, and the material loses its integrity. Owing to the aforementioned reasons, intercalation hosts for multivalent-ion batteries suffer from poor specific capacity (low energy density), sluggish diffusion kinetics (low power density), higher polarization, reduced coulombic and roundtrip efficiency, as well as insufficient cycle life when compared to their monovalent counterparts.Given the problems accompanying multivalent ions, it becomes critical to find high-performing and stable intercalation host materials for multivalent-ion batteries. In this perspective,

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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