Large-scale fabrication of re duce d graphene oxide-sulfur composite films for flexible lithium-sulfur batteries

The rapid development of flexible electronic devices requires the design of flexible energy-storage devices. Lithium-sulfur(Li-S) batteries are attracting much interest due to their high energy density. Therefore, flexible Li-S batteries with high areal capacity are desired. Herein, we fabricated freestanding reduced graphene oxide-sulfur(RGO@S) composite films with a cross-linked structure using a blade coating technique, followed by a subsequent chemical reduction. The porous cross-linked structure endows the composite films with excellent electrochemical performance. The batteries based on RGO@S composite films could exhibit a high discharge capacity of 1381 m Ah/g at 0.1 C and excellent cycle stability. Furthermore, the freestanding composite film possesses excellent conductivity and high mechanical strength. Therefore, they can be used as the cathodes of flexible Li-S batteries. As a proof of concept, soft-packaged Li-S batteries were assembled and remained stable electrochemical performance under different bending states.

Iron and lead ion adsorption by microbial flocculants in synthetic wastewater and their related carbonate formation

Although microbial treatments of heavy metal ions in wastewater have been studied, the removal of these metals through incorporation into carbonate minerals has rarely been reported. To investigate the removal of Fe^3＋ and Pb^2＋, two representative metals in wastewater, through the precipitation of carbonate minerals by a microbial flocculant （MBF） produced by Bacillus mucilaginosus. MBF was added to synthetic wastewater containing different Fe^3＋ and Pb^2＋ concentrations, and the extent of flocculation was analyzed. CO2 was bubbled into the mixture of MBF and Fe^3＋/Pb^2＋ to initiate the reaction. The solid substrates were analyzed via X-ray diffraction, transmission electron microscopy and energy dispersive spectroscopy. The results showed that the removal efficiency decreased and the MBF adsorption capacity for metals increased with increasing heavy metal concentration. In the system containing MBF, metals （Fe^3＋ and Pb^2＋）, and CO2, the concentrated metals adsorbed onto the MBF combined with the dissolved CO2, resulting in oversaturation of metal carbonate minerals to form iron carbonate and lead carbonates. These results may be used in designing a method in which microbes can be utilized to combine CO2 with wastewater heavy metals to form carbonates, with the aim of mitigating environmental problems.

Bimetal-organic frameworks derived Co/N-doped carbons for lithium-sulfur batteries

Lithium-sulfur(Li-S) batteries have received extensive attention due to their high theoretical specific energy density.However,the utilization of sulfur is seriously reduced by the shuttle effect of lithium polysulfides and the low conductivity of sulfur and lithium sulfide(Li2S).Herein,we introduced bimetalorganic frameworks(Co/Zn-ZIF) derived cobalt and nitrogen-doped carbons(Co/N-C) into Li-S batteries through host design and sepa rator modification.The Co/N-C in Li-S batteries effectively limits the shuttle effect through simultaneously serving as polysulfide traps and chemical catalyst.As a result,the Li-S batteries deliver a high reversible capacity of 1614.5 mAh/g and superior long-term cycling stability with a negligible capacity decay of only 0.04% per cycle after 1000 cycles.Furthermore,they have a high area capacity of 5.5 mAh/cm2.

Smart supercapacitors from materials to devices

The recent development in smart electronic devices has increased the demand for supercapacitors to integrate with other different functions.Recently,many research efforts have been made to fabricate smart components of supercapacitors and to construct them into novel device configurations.In this mini review,we summarize recent progress in smart supercapacitors with the functions of self-healing,shape memory,electrochromism,and photodetection,including the design of electrode materials,the optimization of the configuration,and working mechanism.Furthermore,the perspective and challenges for the development of smart supercapacitors are also discussed deeply.

Soil total organic carbon/total nitrogen ratio as a key driver deterministically shapes diazotrophic community assemblages during the succession of biological soil crusts

The diazotrophic community in biological soil crusts(biocrusts)is the key supplier of nitrogen in dryland.To date,there is still limited information on how biocrust development influences the succession of diazotrophic community,and what are the most important factors mediating diazotrophic communities during biocrust succession.Using the high throughput nifH amplicon sequencing,the diazotrophs in soils at different developmental stages of biocrust were comparatively studied.The results evidenced the decreases of TOC/TN ratio and pH value with biocrust development.Nostoc and Scytonema were the most dominant diazotrophic genera at all biocrust stages,while Azospirillum and Bradyrhizobium were abundant only in bare soil.Diazotrophic co-occurrence networks tended to be less complex and less connected with biocrust succession.The soil TOC/TN ratio was the most dominant factor mediating diazotrophic diversity,community composition and assembly processes,while diazotrophic-diversity and NO3–-N/NH4+-N ratio were positively correlated with the nitrogenase activity during biocrust succession.This study provided novel understandings of nitrogen fixation and succession patterns of diazotrophic community,by showing the effects of biocrust succession on diazotrophic diversity,community composition,community assembly and co-occurrence networks,and recognizing TOC/TN ratio as the most dominant factor mediating diazotrophs during biocrust succession.

基于耐低温、保湿多功能凝胶电解质的柔性水系锌离子电池

水系锌离子电池由于具有安全性高、成本低的特点,在柔性储能领域得到广泛关注.然而,传统柔性水系锌离子电池处于零下温度时,由于其电解质的凝固,电池容量会发生严重衰减.此外,当电池承受大幅度的形变后,其外包装易发生破损,造成电解质中水分的挥发,最终导致器件失效.在本文中,我们开发了一种基于聚丙烯酰胺(PAM)和甘油(Gly)的耐低温、保湿凝胶电解质.PAM和Gly与水分子之间的强氢键作用不仅抑制了凝胶电解质在低温时的凝固,而且限制了电解质中自由水的挥发.基于该电解质的柔性水系锌离子电池在-40℃时仍具有优良的电化学性能,并且无封装的电池在30天后仍保持了初始容量的98%.该工作提供了一种设计水系储能器件用耐低温、保湿凝胶电解质的新思路.

Activated carbon felts with exfoliated graphene nanosheets for flexible all-solid-state supercapacitors

The recent development of portable electronics promotes the growing demand for flexible energy storage devices. Supercapacitors are promising candidates due to their high power density. Therefore, flexible supercapacitors are desired. Here, the porous activated carbon felts(ACFs) with exfoliated graphene nanosheets and rich oxygen-containing groups were fabricated by a facile thermal treatment strategy.Such ACFs can act as the flexible electrodes of all-solid-state supercapacitors directly without the use of binder and conductive materials. They exhibit excellent electrochemical properties, such as high specific areal capacitance, superior rate ability and long-term cycling stability. Moreover, the fabricated flexible all-solid-state supercapacitors based on ACFs deliver stable electrochemical performance under different bending states.

Sulfur nanoparticles encapsulated in reduced graphene oxide nanotubes for flexible lithium-sulfur batteries

Rapid development of flexible electronic devices is promoting the design of flexible energy-storage devices. Lithium-sulfur （Li-S） batteries are considered as promising candidates for high energy density energy-storage devices. Therefore, flexible Li-S batteries are desired. In this study, we fabricated composite films of freestanding reduced graphene oxide nanotubes wrapped sulfur nanoparticles （RGONTs@S） by pressing RGONTs@S composite foams, which were synthesized by combining cold quenching with freeze-drying and a subsequent reduction process. These RGONTs@S composite films can serve as self-supporting cathodes for Li-S batteries without additional binders and conductive agents. Their interconnected tubular structure allows easy electron transport throughout the network and helps to confine the polysulfides produced during the charge/ discharge process. As a result, the RGONTs@S composite films exhibited a high initial specific capacity, remarkable cycling stabilit36 and excellent rate capability. More importantly, the RGONTs@S composite films can serve as electrodes in flexible Li-S batteries. As a proof of concept, soft-packaged Li-S batteries were assembled using these electrodes and they displayed stable electrochemical performance at different bending states.

柔性一体化储能器件在弯曲状态下的力学有限元模拟分析

近年来,关于柔性储能器件设计的研究越来越多,然而对其在弯曲状态下力学行为的研究还不够系统,人们对于器件结构所带来的力学行为影响的认识也不够全面.在本文中,我们通过有限元模拟的方法系统全面地研究了柔性一体化储能器件在弯曲状态下的力学行为.本文主要研究了电极和电解质的厚度,模量以及泊松比对整个器件在弯曲状态下应变能以及应力应变分散的影响,所得到的分析结果将为设计拥有更优异力学性能的一体化储能器件提供指导.