Metallic Li is a promising anode material for high energy density batteries but it suffers from poor stability and formation of unsafe dendrites. Previous studies demonstrated that 3 D metal foams are able to improve ...Metallic Li is a promising anode material for high energy density batteries but it suffers from poor stability and formation of unsafe dendrites. Previous studies demonstrated that 3 D metal foams are able to improve the stability of Li metal but the properties of these foams are inherently limited. Here we report a facile surface modification approach via magnetron sputtering of mixed oxides that effectively modulate the properties of Cu foams for supporting Li metal with remarkable stability. We discovered that hybrid Li anodes with Li metal thermally infused to aluminum-zinc oxides(AZO) coated Cu foams have significantly improved stability and reactivity compared with pristine Li foils and Li infused to unmodified Cu foams. Full cells assembled with a Li Fe PO4 cathode and a hybrid anode maintained low and stable charge-transfer resistance(<50) during 500 cycles in carbonate electrolytes, and exhibited superior rate capability(~100 m Ah g-1 at 20 C) along with better electrochemical reversibility and surface stability. The AZO modified Cu foams had superior mechanical strength and afforded the hybrid anodes with minimized volume change without the formation of dendrites during battery cycling. The rational construction of surface architecture to precisely control Li plating and stripping may have great implications for the practical applications of Li metal batteries.展开更多
To date, most of the research on electrodes for lithium sulfur batteries has been focused on the nanostructured sulfur cathodes and achieves significant success. However, from the viewpoint of manufacturers, the nanos...To date, most of the research on electrodes for lithium sulfur batteries has been focused on the nanostructured sulfur cathodes and achieves significant success. However, from the viewpoint of manufacturers, the nanostructured sulfur cathodes are not so promising, because of the low volumetric energy density and high cost. In this work, we obtained the low-cost, scalable, eco-friendly mass production of edge-functionalized acetylene black-sulfur(FAB-S) composites by high-energy ball-milling technique for lithium sulfur batteries. The as-prepared FAB-S composite can deliver a high initial discharge capacity of 1304 mAh/g and still remain a reversible capacity of 814 mAh/g after 200 cycles at a charge-discharge rate of 0.2 C in the voltage range of 1.7–2.7 V. The observed excellent electrochemical properties demonstrate that the cathodes obtained by the facile high-energy ball-milling method as the cathode for rechargeable Li-S batteries are of great potential because it used the sole conductive additive acetylene black(AB).Such improved properties could be attributed to the partially exfoliation of AB, which not only keeps the AB’s inherent advantage, but also increases the specific surface area and forms chemical bonds between carbon and sulfur, resulting in the accumulation of the polysulfides intermediate through both the physical and chemical routes.展开更多
To date, Wald sequential probability ratio test(WSPRT) has been widely applied to track management of multiple hypothesis tracking(MHT). But in a real situation, if the false alarm spatial density is much larger than ...To date, Wald sequential probability ratio test(WSPRT) has been widely applied to track management of multiple hypothesis tracking(MHT). But in a real situation, if the false alarm spatial density is much larger than the new target spatial density, the original track score will be very close to the deletion threshold of the WSPRT. Consequently, all tracks, including target tracks, may easily be deleted, which means that the tracking performance is sensitive to the tracking environment. Meanwhile, if a target exists for a long time, its track will have a high score, which will make the track survive for a long time even after the target has disappeared. In this paper, to consider the relationship between the hypotheses of the test, we adopt the Shiryayev SPRT(SSPRT) for track management in MHT. By introducing a hypothesis transition probability, the original track score can increase faster, which solves the first problem. In addition, by setting an independent SSPRT for track deletion, the track score can decrease faster, which solves the second problem. The simulation results show that the proposed SSPRT-based MHT can achieve better tracking performance than MHT based on the WSPRT under a high false alarm spatial density.展开更多
石墨烯纳米卷作为石墨烯的一维变体结构,它不仅继承了石墨烯优异的本征性能,还具有独特的开放拓扑结构.在石墨烯纳米卷的阿基米德型螺旋开放的层间内嵌功能组分,可赋予石墨烯新的功能,引领石墨烯在能量存储、环境修复、生物技术以及智...石墨烯纳米卷作为石墨烯的一维变体结构,它不仅继承了石墨烯优异的本征性能,还具有独特的开放拓扑结构.在石墨烯纳米卷的阿基米德型螺旋开放的层间内嵌功能组分,可赋予石墨烯新的功能,引领石墨烯在能量存储、环境修复、生物技术以及智能元器件等领域实现划时代变革.然而,引入功能性组分显著地削弱了石墨烯卷曲的驱动力,因此,制备功能化石墨烯纳米卷仍面临巨大挑战.在本项工作中,将密度泛函理论预测与实验研究相结合,我们提出了一种制备功能化石墨烯纳米卷的普适性策略,即以金属阳离子-π相互作用为驱动力,实现氧化石墨烯在碳纳米管表面的自发卷曲,获得功能化石墨烯纳米卷.并进一步揭示了纳米卷的形成机制和酸度依赖性规则.基于石墨烯纳米卷的特殊分级结构以及金属阳离子的活性吸附,所制备的纳米卷气凝胶表现出优异的吸附性能,其吸附有机溶剂的容量可高达129.9-265.7 g g;.这项工作提供了一种简单有效且具有普适性的功能化石墨烯纳米卷的制备策略,可为其在相关领域的推广与应用提供理论基础和技术支撑.展开更多
基金The financial supports of the National Natural Science Foundation of China(Grant Nos.51572060,51702067 and 51671074)Special Financial Grant from the China Postdoctoral Science Foundation(No.2017T100239)+1 种基金General Financial Grant from the China Postdoctoral Science Foundation(No.2016M590279)the startup grants from Northern Illinois University。
文摘Metallic Li is a promising anode material for high energy density batteries but it suffers from poor stability and formation of unsafe dendrites. Previous studies demonstrated that 3 D metal foams are able to improve the stability of Li metal but the properties of these foams are inherently limited. Here we report a facile surface modification approach via magnetron sputtering of mixed oxides that effectively modulate the properties of Cu foams for supporting Li metal with remarkable stability. We discovered that hybrid Li anodes with Li metal thermally infused to aluminum-zinc oxides(AZO) coated Cu foams have significantly improved stability and reactivity compared with pristine Li foils and Li infused to unmodified Cu foams. Full cells assembled with a Li Fe PO4 cathode and a hybrid anode maintained low and stable charge-transfer resistance(<50) during 500 cycles in carbonate electrolytes, and exhibited superior rate capability(~100 m Ah g-1 at 20 C) along with better electrochemical reversibility and surface stability. The AZO modified Cu foams had superior mechanical strength and afforded the hybrid anodes with minimized volume change without the formation of dendrites during battery cycling. The rational construction of surface architecture to precisely control Li plating and stripping may have great implications for the practical applications of Li metal batteries.
基金supported by the National Natural Science Foundation of China(Grant Nos.51671074,51602079,51572060,and 51502062)the Fundamental Research Funds for the Central Universities(No.HIT.BRETIII.201224 and 201312)+1 种基金Program for Innovation Research of Science in Harbin Institute of Technology(PIRS of HIT-No.201506)support from the Excellent Youth Foundation of Heilongjiang Scientific Committee(No.JC2015010)
文摘To date, most of the research on electrodes for lithium sulfur batteries has been focused on the nanostructured sulfur cathodes and achieves significant success. However, from the viewpoint of manufacturers, the nanostructured sulfur cathodes are not so promising, because of the low volumetric energy density and high cost. In this work, we obtained the low-cost, scalable, eco-friendly mass production of edge-functionalized acetylene black-sulfur(FAB-S) composites by high-energy ball-milling technique for lithium sulfur batteries. The as-prepared FAB-S composite can deliver a high initial discharge capacity of 1304 mAh/g and still remain a reversible capacity of 814 mAh/g after 200 cycles at a charge-discharge rate of 0.2 C in the voltage range of 1.7–2.7 V. The observed excellent electrochemical properties demonstrate that the cathodes obtained by the facile high-energy ball-milling method as the cathode for rechargeable Li-S batteries are of great potential because it used the sole conductive additive acetylene black(AB).Such improved properties could be attributed to the partially exfoliation of AB, which not only keeps the AB’s inherent advantage, but also increases the specific surface area and forms chemical bonds between carbon and sulfur, resulting in the accumulation of the polysulfides intermediate through both the physical and chemical routes.
基金supported by National Natural Science Foundation of China (Grant Nos. 61471019, 61501011)
文摘To date, Wald sequential probability ratio test(WSPRT) has been widely applied to track management of multiple hypothesis tracking(MHT). But in a real situation, if the false alarm spatial density is much larger than the new target spatial density, the original track score will be very close to the deletion threshold of the WSPRT. Consequently, all tracks, including target tracks, may easily be deleted, which means that the tracking performance is sensitive to the tracking environment. Meanwhile, if a target exists for a long time, its track will have a high score, which will make the track survive for a long time even after the target has disappeared. In this paper, to consider the relationship between the hypotheses of the test, we adopt the Shiryayev SPRT(SSPRT) for track management in MHT. By introducing a hypothesis transition probability, the original track score can increase faster, which solves the first problem. In addition, by setting an independent SSPRT for track deletion, the track score can decrease faster, which solves the second problem. The simulation results show that the proposed SSPRT-based MHT can achieve better tracking performance than MHT based on the WSPRT under a high false alarm spatial density.
基金jointly supported by the National Natural Science Foundation of China(U2067216)Heilongjiang Touyan Team(HITTY-20190033)。
文摘石墨烯纳米卷作为石墨烯的一维变体结构,它不仅继承了石墨烯优异的本征性能,还具有独特的开放拓扑结构.在石墨烯纳米卷的阿基米德型螺旋开放的层间内嵌功能组分,可赋予石墨烯新的功能,引领石墨烯在能量存储、环境修复、生物技术以及智能元器件等领域实现划时代变革.然而,引入功能性组分显著地削弱了石墨烯卷曲的驱动力,因此,制备功能化石墨烯纳米卷仍面临巨大挑战.在本项工作中,将密度泛函理论预测与实验研究相结合,我们提出了一种制备功能化石墨烯纳米卷的普适性策略,即以金属阳离子-π相互作用为驱动力,实现氧化石墨烯在碳纳米管表面的自发卷曲,获得功能化石墨烯纳米卷.并进一步揭示了纳米卷的形成机制和酸度依赖性规则.基于石墨烯纳米卷的特殊分级结构以及金属阳离子的活性吸附,所制备的纳米卷气凝胶表现出优异的吸附性能,其吸附有机溶剂的容量可高达129.9-265.7 g g;.这项工作提供了一种简单有效且具有普适性的功能化石墨烯纳米卷的制备策略,可为其在相关领域的推广与应用提供理论基础和技术支撑.
