Rational Designs for Lithium-Sulfur Batteries with Low Electrolyte/Sulfur Ratio

Lithium-sulfur batteries (LSBs) are considered a promising next-generation energy storage device owing to their high theoretical energy density. However, their overall performance is limited by several critical issues such as lithium polysulfide (PS) shuttles, low sulfur utilization, and unstable Li metal anodes. Despite recent huge progress, the electrolyte/sulfur ratio (E/S) used is usually very high (≥20 µL mg⁻¹), which greatly reduces the practical energy density of devices. To push forward LSBs from the lab to the industry, considerable attention is devoted to reducing E/S while ensuring the electrochemical performance. To date, however, few reviews have comprehensively elucidated the possible strategies to achieve that purpose. In this review, recent advances in low E/S cathodes and anodes based on the issues resulting from low E/S and the corresponding solutions are summarized. These will be beneficial for a systematic understanding of the rational design ideas and research trends of low E/S LSBs. In particular, three strategies are proposed for cathodes: preventing PS formation/aggregation to avoid inadequate dissolution, designing multifunctional macroporous networks to address incomplete infiltration, and utilizing an imprison strategy to relieve the adsorption dependence on specific surface area. Finally, the challenges and future prospects for low E/S LSBs are discussed.     

椰壳活性炭孔结构对Li-S电池性能的影响

以椰壳为原料,采用化学活化法制备不同比表面积和孔结构的活性炭,通过改变制备工艺参数来调节活性炭的比表面积和孔结构。将活性炭负载60%(质量分数)硫后,作为锂硫电池的正极材料,研究活性炭孔结构对锂硫电池性能的影响。结果表明:随着活性炭比表面积的增加,中孔比例增加,锂硫电池比容量逐步提高。其中,当活化剂与炭化料的质量比为4时,活性炭的比表面积达到2900m2/g,中孔率达到15.36%。在电流密度为200mA/g时,首次放电比容量高达1294.5mAh/g,循环100次后的可逆比容量仍然高达809.3mAh/g。     

基于高活性碳纳米管海绵体载硫的锂硫电池

用CVD法制备的碳纳米管(CNTs)之间的相互吸引,将其堆叠成具有网状结构、多孔及高活性等优点的CNT海绵体(CNTS).于是,硫蒸气可在CNTs管束上形核沉积并与其紧密接触,使正极电子的高速传输从而提高电池的倍率性能;用XRD、SEM、拉曼光谱等手段测试CNTS载硫前后的极片,考察了硫在CNTs表面的分布和载硫对其结...     

石墨烯基自支撑夹层材料在锂硫电池中的研究进展

近年来,高比能锂-硫电池作为最具前景的新能源储存装置之一引起了人们的广泛关注。然而,在该电池体系中,中间产物聚硫化物的溶解造成的穿梭效应会明显降低电池的循环性能和硫利用率,严重阻碍锂-硫电池的推广应用。综述了近年来石墨烯和石墨烯基复合自支撑中间层材料在锂-硫电池中的应用,例如,通过物理或化学限域的方法减缓多硫化物的穿梭并改善锂-硫电池电化学性能等,并对石墨烯基复合自支撑中间层材料未来在锂硫电池中的实际应用进行了展望。     

石墨烯在锂硫电池中的应用

锂硫电池具有很高的能量密度[2 600(W·h)/kg],其正极材料硫具有储藏丰富、对环境友好等优点,因此锂硫电池成为下一代二次电池的研发重点。然而,硫的高绝缘性、反应过程中体积的变化以及中间产物多硫离子溶解等难题,使其目前很难实现商品化。石墨烯具有超高的导电性和优异的力学性能,其与硫制成的复合材料作为电池正极材料可以有效地解决上述问题。从石墨烯–硫复合材料、石墨烯–碳–硫复合材料、石墨烯–聚合物–硫复合材料、石墨烯–氧化物–硫复合材料等方面出发,总结了石墨烯在锂硫电池中作为正极材料的最新进展,并且提出了未来石墨烯在锂硫电池中应用的研究主要在探索石墨烯简捷的制备方法、研究石墨烯新的应用方式、开发多种材料复合等方面。     

锂硫电池用气相生长碳纤维增强硫-多壁碳纳米管复合正极的影响(英文)

制备了锂硫电池用硫-多壁碳纳米管纳米复合材料,并分别采用气相生长碳纤维(VGCFs)和导电炭黑作为复合正极的导电添加剂,通过形貌表征(SEM)、恒流充放电测试和交流阻抗分析(EIS)研究VGCFs对硫-多壁碳纳米管复合正极的影响。结果表明:采用VGCFs作添加剂的硫-多壁碳纳米管复合电极具有三维网状结构,其首次放电比容量为1254 mA·h/g,40次循环后容量保持在716 mA·h/g。与采用导电炭黑为添加剂的电极相比,采用VGCFs为添加剂的电极具有更高的活性物质利用率和更好的循环稳定性。相互搭接的纤维状VGCFs可形成稳定的导电网络,抑制正极材料及残存放电产物的团聚堆积,维持电极的多孔性,从而改善电池的电化学性能。     

常温下真空浸渍制备的LMC/S复合材料

在常温下,采用真空浸渍的方法,将单质硫(S)填充在大介孔炭(LMC)的孔中,制备出LMC/S复合材料。用SEM、XRD和氮吸附等方法对复合材料进行了分析,用恒流放电、循环伏安等方法对复合材料的电化学性能进行了测试。填充在LMC中的硫高度分散,复合材料的循环性能和硫的利用率都较高。当电流密度为0.4 mA/cm2时,LMC/S电极中硫的首次放电比容量达1 215.5 mAh/g,第50次循环的可逆比容量仍有535.3 mAh/g。     

Edge-rich MoS2 nanosheets for high performance self-supporting Li-S batteries

提高硫的电化学活性和抑制多硫离子的溶解是提高锂硫电池性能的关键问题。层状二维金属硫化物的边缘位点相对于平面位点具有更强的吸附多硫离子的能力。然而利用液相法控制合成具有丰富边缘位点的层状二维过渡金属硫化物材料仍是一个挑战。本文以碳布作为导电基体,设计生长了由小尺寸单层S-Mo-S单元通过层层自组装而成的MoS₂多晶纳米片（V-MoS₂/CC）。探究了该复合材料作为活性物质S载体时对锂硫电池倍率性能和循环稳定性的影响。垂直生长的MoS₂纳米片暴露较多的S-Mo-S层边缘活性位点,不仅可以使得随后负载的硫单质的尺寸保持在纳米级（5～10 nm）,而且对多硫化锂的催化转化及抑制溶解具有一定程度的促进作用。同时,基底材料碳布的存在使得电极材料无需添加导电剂和黏结剂且提高了整体导电性。使用V-MoS₂/CC@S复合材料组装而成的半电池,在1 C和2 C下循环400和800圈后比容量维持在857 mA·h/g和579 mA·h/g。     

三维石墨烯包覆的硫掺杂碳负载二硫化硒复合材料的制备及其储锂性能研究

二硫化硒（SeS₂）作为储锂的正极材料,具有硒和硫以外的独特优势。采用硫掺杂介孔碳（sulfur-doped mesoporous carbon, SMC）负载SeS₂,然后用三维石墨烯（three-dimensional grapheme, 3DG）对其进行包覆,制备了双重限定的SeS₂基正极结构。通过透射电子显微镜（transmission electron microscope, TEM）,扫描电子显微镜（scanning electron microscopy, SEM）以及X射线衍射（X-ray diffraction, XRD）对所制备的3DG-SMC-SeS₂纳米复合材料的形态和结构进行表征。结果显示,SeS₂均匀地分布在SMC基体的介孔通道中,3DG良好地包裹SMC-SeS₂复合材料。受益于SeS₂不可或缺的优势和独特设计的主体构架,3DG-SMC-SeS₂正极表现出极好的循环性能和优异的高倍率性能。这种新型SeS₂基正极材料为克服目前锂硫电池的主要瓶颈提供了一种可行的策略。     

Multi-functional TiO2 nanosheets/carbon nanotubes modified separator enhanced cycling performance for lithium-sulfur batteries

TiO₂ nanosheets (TiO₂NSs) have been investigated for lithium-sulfur (Li-S) batteries as strategically designed TiO₂ nanosheet/carbon nanotube (TiO₂NS/CNT) composite modified polypropylene (PP) separator to inhibit the shuttling of the intermediate polysulfides. The modified separator was fabricated by the vacuum filtration method using the exfoliation TiO₂NSs and untreated carbon nanotube (CNT) composites. The multi-functional TiO₂NS/CNT coating not only reduced the electrochemical resistance but also localized the migrating polysulfides by the cooperative effect of physical adsorption and chemical binding. Specifically, the composition ratio of TiO₂NSs/CNTs and the interface character have been studied. It was found that the optimum ratio and perfect electrolyte wettability of the TiO₂NS/CNT layers were all the critical reasons to achieve good battery performance. The high initial discharge capacity of 1247 mA h g⁻¹ at 0.2 C rate, which was 75% of the theoretical capacity of sulfur, 98% average coulombic efficiency, and 627 mA h g⁻¹ discharge capacity retention after 100 cycles were obtained with the TiO₂NS/CNT coating separator.