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Abstract Nonaqueous sodium-based batteries are ideal candidates for the next generation of electrochemical energy storage devices. However, despite the promising performance at ambient temperature, their low-temperature (e.g., < 0 °C) operation is detrimentally affected by the increase in the electrolyte resistance and solid electrolyte interphase (SEI) instability. Here, to circumvent these issues, we propose specific electrolyte formulations comprising linear and cyclic ether-based solvents and sodium trifluoromethanesulfonate salt that are thermally stable down to −150 °C and enable the formation of a stable SEI at low temperatures. When tested in the Na||Na coin cell configuration, the low-temperature electrolytes enable long-term cycling down to −80 °C. Via ex situ physicochemical (e.g., X-ray photoelectron spectroscopy, cryogenic transmission electron microscopy and atomic force microscopy) electrode measurements and density functional theory calculations, we investigate the mechanisms responsible for efficient low-temperature electrochemical performance. We also report the assembly and testing between −20 °C and −60 °C of full Na||Na 3 V 2 (PO 4 ) 3 coin cells. The cell tested at −40 °C shows an initial discharge capacity of 68 mAh g −1 with a capacity retention of approximately 94% after 100 cycles at 22 mA g −1 . 

Lithium metal and lithium-rich alloys are high-capacity anode materials that could boost the energy content of rechargeable batteries. However, their development has been hindered by rapid capacity decay during cycling, which is driven by the substantial structural, morphological, and volumetric transformations that these materials and their interfaces experience during charge and discharge. During these transformations, the interplay between chemical/structural changes and solid mechanics plays a defining role in determining electrochemical degradation. This Perspective discusses how chemistry and mechanics are interrelated in influencing the reaction mechanisms, stability, and performance of both lithium metal anodes and alloy anodes. Battery systems with liquid electrolytes and solid-state electrolytes are considered because of the distinct effects of chemo-mechanics in each system. Building on this knowledge, we present a discussion of emerging ideas to control and mitigate chemo-mechanical degradation in these materials to enable translation to commercial systems, which could lead to the development of high-energy batteries that are urgently needed to power our increasingly electrified world.