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Lithium-sulfur (Li-S) batteries are one of the most promising alternative energy storage systems beyond Li-ion batteries. However, the sluggish kinetics of the nucleation and growth of the solid discharge product of Li2S/Li2S2 in the lower discharge plateau has been recently identified as a critical hurdle for attaining high specific capacity in Li-S batteries with high sulfur loadings under lean electrolyte conditions. Herein, a new strategy of breaking the charge-transport bottleneck by successful generation of experimentally verified stable Li2S2 and a reservoir of quasi-solid lithium polysulfides within the micropores of activated carbon fiber cloth as a high-sulfur-loading host is proposed. The developed Li-S cell is capable of delivering a highly sustainable areal capacity of 6.0 mAh cm-2 under lower electrolyte to sulfur ratios (<3.0 mLE gS -1). Micropore confinement leads to generation of solid Li2S2 that enables high utilization of the entire electroactive area by its inherent self-healing capacity. This strategy opens a new avenue for rational material designs for Li-S batteries under lean electrolyte condition. [ABSTRACT FROM AUTHOR]

Abstract: Lithium‐sulfur (Li–S) batteries are one of the most promising alternative energy storage systems beyond Li‐ion batteries. However, the sluggish kinetics of the nucleation and growth of the solid discharge product of Li2S/Li2S2 in the lower discharge plateau has been recently identified as a critical hurdle for attaining high specific capacity in Li–S batteries with high sulfur loadings under lean electrolyte conditions. Herein, a new strategy of breaking the charge‐transport bottleneck by successful generation of experimentally verified stable Li2S2 and a reservoir of quasi‐solid lithium polysulfides within the micropores of activated carbon fiber cloth as a high‐sulfur‐loading host is proposed. The developed Li–S cell is capable of delivering a highly sustainable areal capacity of 6.0 mAh cm−2 under lower electrolyte to sulfur ratios (<3.0 mLE gS−1). Micropore confinement leads to generation of solid Li2S2 that enables high utilization of the entire electroactive area by its inherent self‐healing capacity. This strategy opens a new avenue for rational material designs for Li–S batteries under lean electrolyte condition. [ABSTRACT FROM AUTHOR]

Abstract: Lithium (Li) metal is an ideal anode material for high energy density batteries. However, the low Coulombic efficiency (CE) and the formation of dendrites during repeated plating and stripping processes have hindered its applications in rechargeable Li metal batteries. The accurate measurement of Li CE is a critical factor to predict the cycle life of Li metal batteries, but the measurement of Li CE is affected by various factors that often lead to conflicting values reported in the literature. Here, several parameters that affect the measurement of Li CE are investigated and a more accurate method of determining Li CE is proposed. It is also found that the capacity used for cycling greatly affects the stabilization cycles and the average CE. A higher cycling capacity leads to faster stabilization of Li anode and a higher average CE. With a proper operating protocol, the average Li CE can be increased from 99.0% to 99.5% at a high capacity of 6 mA h cm−2 (which is suitable for practical applications) when a high‐concentration ether‐based electrolyte is used. [ABSTRACT FROM AUTHOR]

In the search for improved energy storage, rechargeable metal-oxygen batteries are very attractive owing to their reliance on molecular oxygen, which forms oxides on discharge that decompose reversibly on charge. Much focus has been directed at aprotic Li-O2 cells, but the aprotic Na-O2 system is of equal interest because of its better reversibility. We report here on the critical role and mechanism of phase-transfer catalysis in Na-O2 batteries. We find that it is solely responsible for the growth and dissolution of micrometre-sized cubic NaO2 crystals and for the reversible cell capacity. In the absence of phase-transfer catalysis, quasi-amorphous NaO2 films are formed and cells exhibit negligible capacity. Electrochemical investigations provide a measure of the transportation of superoxide from the carbon electrode to the electrolyte phase by the phase transfer catalyst. This leads to a new understanding of the mechanism of Na-O2 batteries that, significantly, extends to Li-O2 cells and explains their different behaviour. [ABSTRACT FROM AUTHOR]

A new lithium-ether-derived chelate ionic liquid is synthesized to serve as an electrolyte for the Li-O2 battery that is stable to metallic lithium, and whose ethereal framework is much more inherently stable to superoxide-initiated hydrogen abstraction than the simple glyme, dimethoxyethane (DME). Reactions of chemically generated superoxide with this electrolyte show that virtually no decomposition products such as lithium formate are generated. When the electrolyte is employed in a Li-O2 battery, a ten-fold decrease in CO2 evolution is evident on charge by comparison to DME and greatly enhanced cycling stability is observed with TiC as a cathode support. A mechanism is proposed to account for the lowered reactivity, offering new insight into the stability of organic electrolytes in Li-O2 batteries. This approach for electrolyte design is presented here for the first time, and it can be extended to other organic systems to provide a platform for the design of advanced electrolyte systems. [ABSTRACT FROM AUTHOR]