Lithium/sulfur (Li/S) battery has a 3–5 fold higher theoretical energy density than state-of-art lithium-ion batteries, and research has been ongoing for more than three decades. However, the ...commercialization of Li/S battery still cannot be realized due to many problematic issues, including short cycle life, low cycling efficiency, poor safety and a high self-discharge rate. All these issues are related to the dissolution of lithium polysulfide (PS), the series of sulfur reduction intermediates, in liquid electrolyte and to resulting parasitic reactions with the lithium anode and electrolyte components. On the other hand, the dissolution of PS is essential for the performance of a Li/S cell. Without dissolution of PS, the Li/S cell cannot operate progressively due to the non-conductive nature of elemental sulfur and its reduction products. In this review article, we start with the fundamental chemistry of elemental sulfur in order to discuss the problems and solutions of liquid electrolyte Li/S battery.
► Discuss the real problems of Li/S cells from the fundamental chemistry of Li/S battery. ► Review the current efforts on the research and development of Li/S battery. ► Discuss the drawback of the current efforts. ► Suggest the effective approach for the performance improvement of Li/S battery.
► Effect of LiNO3 on the Li anode and cathode of Li/S battery is studied, respectively. ► LiNO3 participates in the formation of a stable passivation film on the Li anode surface. ► LiNO3 may be ...reduced irreversibly on the cathode, affecting Li/S battery performance. ► Discharge mechanism of Li/S battery is explained from the viewpoint of phase transition.
In this work we study the effect of LiNO3 on the Li anode and sulfur cathode, respectively, of Li/S battery by using a Li/Li symmetric cell and a liquid Li/Li2S9 cell. On the Li anode, LiNO3 participates in the formation of a stable passivation film, and the resulting passivation film grows infinitely with the consumption of LiNO3. The passivation film formed with LiNO3 is known to effectively suppress the redox shuttle of the dissolved lithium polysulfides on Li anode. On the cathode, LiNO3 undergoes a large and irreversible reduction starting at 1.6V in the first discharge, and the irreversible reduction disappears in the subsequent cycles. Moreover, the insoluble reduction products of LiNO3 on the cathode adversely affect the redox reversibility of sulfur cathode. These results indicate that both the Li anode and sulfur cathode consume LiNO3, and that the best benefit of LiNO3 to Li/S battery occurs at the potentials higher than 1.6V. By limiting the irreversible reduction of LiNO3 on the cathode, we have shown that the Li/S cell with a 0.2m LiNO3 as the co-salt can provide a stable capacity of ∼500mAhg−1.
Sulfurized polyacrylonitrile (SPAN) is one of the most important sulfurized carbon materials that can potentially be coupled with the carbonaceous anode to fabricate a safe and low cost "all carbon" ...lithium-ion battery. However, its chemical structure and electrochemical properties have been poorly understood. In this discussion, we analyze the previously published data in combination with our own results to propose a more reasonable chemical structure that consists of short -Sx- chains covalently bonded onto cyclized, partially dehydrogenated, and ribbon-like polyacrylonitrile backbones. The proposed structure fits all previous structural characterizations and explains many unique electrochemical phenomena that were observed from the Li/SPAN cells but have not been understood clearly.
Lithium nitrate (LiNO3) is the most studied additive and co-salt for the electrolyte of lithium-sulfur (Li–S) batteries, its known function is to suppress the redox shuttle of soluble lithium ...polysulfide (PS, Li2Sn), which reflects as an increase in the battery’s coulombic efficiency and cycling stability, as well as a reduced self-discharge rate. The current understanding on this function is that LiNO3 reacts with Li to form a robust surface layer that consequently protects the Li anode from reacting with the dissolved PS. However, little is known on the sulfur cathode except that LiNO3 reduces and adversely affects the battery’s performance when the battery is discharged to lower than 1.7 V. In this paper we report a new finding on the role of LiNO3 in enabling the stable cycling of the sulfur cathode. We show that LiNO3 is capable of catalyzing the conversion of high soluble PS to slightly soluble elemental sulfur near the end of charging process, and that the combination of a soluble nitrate in the electrolyte and an insoluble nitrate in the sulfur cathode leads to synergetic improvement. In addition, a possible mechanism is proposed for the catalysis of LiNO3 on the conversion of PS to elemental sulfur.
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•Role of LiNO3 in Li–S batteries is reinvestigated with focus on sulfur cathode.•Nitrate anion catalyzes the conversion of polysulfide to elemental sulfur.•A catalysis mechanism of nitrate anion on the Li2Sn to S8 conversion is proposed.•Combination of a soluble nitrate and an insoluble nitrate leads to synergetic improvement.
Spatially selective firing of place cells, grid cells, boundary vector/border cells and head direction cells constitutes the basic building blocks of a canonical spatial navigation system centered on ...the hippocampal-entorhinal complex. While head direction cells can be found throughout the brain, spatial tuning outside the hippocampal formation is often non-specific or conjunctive to other representations such as a reward. Although the precise mechanism of spatially selective firing activity is not understood, various studies show sensory inputs, particularly vision, heavily modulate spatial representation in the hippocampal-entorhinal circuit. To better understand the contribution of other sensory inputs in shaping spatial representation in the brain, we performed recording from the primary somatosensory cortex in foraging rats. To our surprise, we were able to detect the full complement of spatially selective firing patterns similar to that reported in the hippocampal-entorhinal network, namely, place cells, head direction cells, boundary vector/border cells, grid cells and conjunctive cells, in the somatosensory cortex. These newly identified somatosensory spatial cells form a spatial map outside the hippocampal formation and support the hypothesis that location information modulates body representation in the somatosensory cortex. Our findings provide transformative insights into our understanding of how spatial information is processed and integrated in the brain, as well as functional operations of the somatosensory cortex in the context of rehabilitation with brain-machine interfaces.
A liquid electrolyte lithium/sulfur (Li/S) cell is a liquid electrochemical system. In discharge, sulfur is first reduced to highly soluble Li2S8, which dissolves into the organic electrolyte and ...serves as the liquid cathode. In solution, lithium polysulfide (PS) undergoes a series of complicated disproportionations, whose chemical equilibriums vary with the PS concentration and affect the cell’s performance. Since the PS concentration relates to a certain electrolyte/sulfur (E/S) ratio, there is an optimized E/S ratio for the cyclability of each Li/S cell system. In this work, we study the optimized E/S ratio by measuring the cycling performance of Li/S cells, and propose an empirical method for determination of the optimized E/S ratio. By employing an electrolyte of 0.25 m LiSO3CF3-0.25 m LiNO3 dissolved in a 1:1 (wt:wt) mixture of dimethyl ether (DME) and 1,3-dioxolane (DOL) in an optimized E/S ratio, we show that the Li/S cell with a cathode containing 72% sulfur and 2 mg cm−2 sulfur loading is able to retain a specific capacity of 780 mAh g−1 after 100 cycles at 0.5 mA cm−2 between 1.7 V and 2.8 V.
Macrophages play an important role in a wide variety of physiologic and pathologic processes. Plasticity and functional polarization are hallmarks of macrophages. Macrophages commonly exist in two ...distinct subsets: classically activated macrophages (M1) and alternatively activated macrophages (M2). M2b, a subtype of M2 macrophages, has attracted increasing attention over the past decade due to its strong immune‐regulated and anti‐inflammatory effects. A wide variety of stimuli and multiple factors modulate M2b macrophage polarization in vitro and in vivo. M2b macrophages possess both protective and pathogenic roles in various diseases. Understanding the mechanisms of M2b macrophage activation and the modulation of their polarization might provide a great perspective for the design of novel therapeutic strategies. The purpose of this review is to discuss current knowledge of M2b macrophage polarization, the roles of M2b macrophages in a variety of diseases and the stimuli to modulate M2b macrophage polarization.
Review outlines the current knowledge of the stimuli of M2b macrophage polarization and the roles of these cells in diseases.
This paper reviews the separators used in liquid electrolyte Li-ion batteries. According to the structure and composition of the membranes, the battery separators can be broadly divided as three ...groups: (1) microporous polymer membranes, (2) non-woven fabric mats and (3) inorganic composite membranes. The microporous polymer membranes are characterised by their thinness and thermal shutdown properties. The non-woven mats have high porosity and a low cost, while the composite membranes have excellent wettability and exceptional thermal stability. The manufacture, characteristics, performance and modifications of these separators are introduced and discussed. Among numerous battery separators, the thermal shutdown and ceramic separators are of special importance in enhancing the safety of Li-ion batteries. The former consists of either a polyethylene (PE)–polypropylene (PP) multilayer structure or a PE–PP blend which increases safety by allowing meltdown of the PE to close the ionic conduction pathways at a temperature below that at which thermal runway occurs. Whereas the latter comprises nano-size ceramic materials coated on two sides of a flexible and highly porous non-woven matrix which enhances the safety by retaining extremely stable dimensions even at very high temperatures to prevent the direct contact of the electrodes.
Evaluation of airborne infection risk with spatial and temporal resolutions is indispensable for the design of proper interventions fighting infectious respiratory diseases (e.g., COVID-19), because ...the distribution of aerosol contagions is both spatially and temporally non-uniform. However, the well-recognized Wells-Riley model and modified Wells-Riley model (i.e., the rebreathed-fraction model) are limited to the well-mixed condition and unable to evaluate airborne infection risk spatially and temporally, which could result in overestimation or underestimation of airborne infection risk. This study proposes a dilution-based evaluation method for airborne infection risk. The method proposed is benchmarked by the Wells-Riley model and modified Wells-Riley model, which indicates that the method proposed is a thorough expansion of the Wells-Riley model for evaluation of airborne infection risk with both spatial and temporal resolutions. Experiments in a mock hospital ward also demonstrate that the method proposed effectively evaluates the airborne infection risk both spatially and temporally. The proposed method is convenient to implement for the development of healthy built environments.
•Dilution-based evaluation of airborne infection risk is proposed.•It is benchmarked with Wells-Riley model for well-mixed and steady condition.•It is benchmarked with rebreathed-fraction model for well-mixed and dynamic condition.•It has spatial and temporal resolutions.•It is a thorough expansion of Wells-Riley model.
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