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  1. Abstract

    Solid‐state lithium metal batteries with garnet‐type electrolyte provide several advantages over conventional lithium‐ion batteries, especially for safety and energy density. However, a few grand challenges such as the propagation of Li dendrites, poor interfacial contact between the solid electrolyte and the electrodes, and formation of lithium carbonate during ambient exposure over the solid‐state electrolyte prevent the viability of such batteries. Herein, an ultrathin sub‐nanometer porous carbon nanomembrane (CNM) is employed on the surface of solid‐state electrolyte (SSE) that increases the adhesion of SSE with electrodes, prevents lithium carbonate formation over the surface, regulates the flow of Li‐ions, and blocks any electronic leakage. The sub‐nanometer scale pores in CNM allow rapid permeation of Li‐ions across the electrode–electrolyte interface without the presence of any liquid medium. Additionally, CNM suppresses the propagation of Li dendrites by over sevenfold up to a current density of 0.7 mA cm−2and enables the cycling of all‐solid‐state batteries at low stack pressure of 2 MPa using LiFePO4cathode and Li metal anode. The CNM provides chemical stability to the solid electrolyte for over 4 weeks of ambient exposure with less than a 4% increase in surface impurities.

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  3. Lithium metal as an anode has been widely accepted due to its higher negative electrochemical potential and theoretical capacity. Nevertheless, the existing safety and cyclability issues limit lithium metal anodes from practical use in high-energy density batteries. Repeated Li deposition and dissolution processes upon cycling lead to the formation of dendrites at the interface which results in reduced Li availability for electrochemical reactions, disruption in Li transport through the interface and increased safety concerns due to short circuiting. Here, we demonstrate a novel strategy using Ionic Liquid Crystals (ILCs) as the electrolyte cum pseudo-separator to suppress dendrite growth with their anisotropic properties controlling Li-ion mass transport. A thermotropic ILC with two-dimensional Li-ion conducting pathways was synthesized and characterized. Microscopic and spectroscopic analyses elucidate that the ILC formed with a smectic A phase, which can be utilized for wide temperature window operation. The results of electrochemical studies corroborate the efficacy of ILC electrolytes in mitigating dendrite formation even after 850 hours and it is further substantiated by numerical simulation and the mechanism involved in dendritic suppression was deduced. 
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    The lithium-sulfur (Li-S) redox battery system is considered to be the most promising next-generation energy storage technology due to its high theoretical specific capacity (1673 mAh g−1), high energy density (2600 Wh kg−1), low cost, and the environmentally friendly nature of sulfur. Though this system is deemed to be the next-generation energy storage device for portable electronics and electric vehicles, its poor cycle life, low coulombic efficiency and low rate capability limit it from practical applications. These performance barriers were linked to several issues like polysulfide (LiPS) shuttle, inherent low conductivity of charge/discharge end products, and poor redox kinetics. Here, we review the recent developments made to alleviate these problems through an electrocatalysis approach, which is considered to be an effective strategy not only to trap the LiPS but also to accelerate their conversion reactions kinetics. Herein, the influence of different chemical interactions between the LiPS and the catalyst surfaces and their effect on the conversion of liquid LiPS to solid end products are reviewed. Finally, we also discussed the challenges and perspectives for designing cathode architectures to enable high sulfur loading along with the capability to rapidly convert the LiPS. 
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  6. Abstract

    Suppressing Li dendrite growth has gained research interest due to the high theoretical capacity of Li metal anodes. Traditional Celgard membranes which are currently used in Li metal batteries fall short in achieving uniform Li flux at the electrode/electrolyte interface due to their inherent irregular pore sizes. Here, the use of an ultrathin (≈1.2 nm) carbon nanomembrane (CNM) which contains sub‐nanometer sized pores as an interlayer to regulate the mass transport of Li‐ions is demonstrated. Symmetrical cell analysis reveals that the cell with CNM interlayer cycles over 2x longer than the control experiment without the formation of Li dendrites. Further investigation on the Li plating morphology on Cu foil reveals highly dense deposits of Li metal using a standard carbonate electrolyte. A smoothed‐particle hydrodynamics simulation of the mass transport at the anode–electrolyte interface elucidates the effect of the CNM in promoting the formation of highly dense Li deposits and inhibiting the formation of dendrites. A lithium metal battery fabricated using the LiFePO4cathode exhibits a stable, flat voltage profile with low polarization for over 300 cycles indicating the effect of regulated mass transport.

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