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Hierarchical c-Si/SnO_2 nanowires and connected Si-Cu alloy nanotubes as anodes for high performance lithium-ion batteries
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摘要
Seeking high rate, high mass-loading and durable anode materials for lithium ion batteries(LIBs) has been a crucial aspect to promote the use of electric vehicles and other portable ele ctronics. Silicon(Si) has been well-known as an outstanding candidate for LIBs, with a high lithium storage capacity of 4200 m Ah/g and a relatively low lithium insertion potential. However, the process of lithium ions(Li-ion) insertion comes with a huge volume change as large as 400% that will cause a radical pulverization/fracture in the Si host and rapid capacity fading. A common strategy to address this issue is to explore various nanostructured Si materials, including nanoparticles, nanowires(NWs) and nanotubes, which can help to accommodate the large volumetric change during charge/discharge cycling. Among them, nanowire core-shell or hierarchical nano-branch structures have attracted particular interests, where the NW-core can be optimized to serve as efficient electric pathway, while the outer sidewall-coated Si thin film shell or Si NW branches enjoy a large interface for fast Li-ion interaction or insertion. Herein, we will first report a novel alloy-forming approach to convert amorphous Si(a-Si) coated copper-oxide(CuO) core-shell nanowires(NWs) into hollow and highly-interconnected Si-Cu alloy(mixture) nanotubes [1, 2]. The conformal coating of a thick a-Si(>120 nm) layer, in a fine-tuned plasma enhanced deposition, helps to forge a beneficial multipath network over the CuO NWs. Upon a simple H_2 annealing, the CuO cores are reduced and diffuse out to alloy with the a-Si shell, producing highly-interconnected hollow Si-Cu alloy nanotubes, which can serve as high capacity and self-conductive anode structures with robust mechanical support. A high specific capacity of 1010 m Ah/g(or 780 m Ah/g) has been achieved after 1000 cycles at 3.4 A/g(or 20 A/g), with a capacity retention rate of ~84%(~ 88%), without the use of any binder or conductive agent. Remarkably, they can survive extremely fast charging rate at 70 A/g for 35 runs(corresponding to one full cycle in 30s) and recover 88% capacity. Then, we propose also a new hierarchical structure of fine-tuned crystalline Si(c-Si) nanowires(NWs) grafted upon ultra-long tin dioxide(SnO_2) NW trunks [3], where the latter frame up a large, conductive and stable architecture i) to host a high mass load of high capacity c-Si NWs medium for Li-ion storage, and ii) to guarantee a good electric contact and fast charging process. The Si NWs branches are produced via a low-temperature vapor-liquid-solid(VLS) growth mediated by Sn catalyst droplets produced by a simple H_2 plasma treatment upon the SnO_2 trunks. Compared to other NW anodes structures, with different nanostructured storage mediums, the c-Si/SnO_2 NWs hierarchical structure demonstrates an outstanding performance with a high mass-load(~1.5 mg/cm~2) and a high areal capacity(~1.8 m Ah/cm~2) after 100 cycles, without the use of any additional polymer, conductive agent or binders.Finally, in this work, we will present our latest progresses in combing the hierarchical nanowire/nanotube structures to achieve simultaneously a high rate, high capacity, high massloading and durable nanostructured anode material to fulfill the true potential of Si-loaded LIB applications.
Seeking high rate, high mass-loading and durable anode materials for lithium ion batteries(LIBs) has been a crucial aspect to promote the use of electric vehicles and other portable ele ctronics. Silicon(Si) has been well-known as an outstanding candidate for LIBs, with a high lithium storage capacity of 4200 m Ah/g and a relatively low lithium insertion potential. However, the process of lithium ions(Li-ion) insertion comes with a huge volume change as large as 400% that will cause a radical pulverization/fracture in the Si host and rapid capacity fading. A common strategy to address this issue is to explore various nanostructured Si materials, including nanoparticles, nanowires(NWs) and nanotubes, which can help to accommodate the large volumetric change during charge/discharge cycling. Among them, nanowire core-shell or hierarchical nano-branch structures have attracted particular interests, where the NW-core can be optimized to serve as efficient electric pathway, while the outer sidewall-coated Si thin film shell or Si NW branches enjoy a large interface for fast Li-ion interaction or insertion. Herein, we will first report a novel alloy-forming approach to convert amorphous Si(a-Si) coated copper-oxide(CuO) core-shell nanowires(NWs) into hollow and highly-interconnected Si-Cu alloy(mixture) nanotubes [1, 2]. The conformal coating of a thick a-Si(>120 nm) layer, in a fine-tuned plasma enhanced deposition, helps to forge a beneficial multipath network over the CuO NWs. Upon a simple H_2 annealing, the CuO cores are reduced and diffuse out to alloy with the a-Si shell, producing highly-interconnected hollow Si-Cu alloy nanotubes, which can serve as high capacity and self-conductive anode structures with robust mechanical support. A high specific capacity of 1010 m Ah/g(or 780 m Ah/g) has been achieved after 1000 cycles at 3.4 A/g(or 20 A/g), with a capacity retention rate of ~84%(~ 88%), without the use of any binder or conductive agent. Remarkably, they can survive extremely fast charging rate at 70 A/g for 35 runs(corresponding to one full cycle in 30s) and recover 88% capacity. Then, we propose also a new hierarchical structure of fine-tuned crystalline Si(c-Si) nanowires(NWs) grafted upon ultra-long tin dioxide(SnO_2) NW trunks [3], where the latter frame up a large, conductive and stable architecture i) to host a high mass load of high capacity c-Si NWs medium for Li-ion storage, and ii) to guarantee a good electric contact and fast charging process. The Si NWs branches are produced via a low-temperature vapor-liquid-solid(VLS) growth mediated by Sn catalyst droplets produced by a simple H_2 plasma treatment upon the SnO_2 trunks. Compared to other NW anodes structures, with different nanostructured storage mediums, the c-Si/SnO_2 NWs hierarchical structure demonstrates an outstanding performance with a high mass-load(~1.5 mg/cm~2) and a high areal capacity(~1.8 m Ah/cm~2) after 100 cycles, without the use of any additional polymer, conductive agent or binders.Finally, in this work, we will present our latest progresses in combing the hierarchical nanowire/nanotube structures to achieve simultaneously a high rate, high capacity, high massloading and durable nanostructured anode material to fulfill the true potential of Si-loaded LIB applications.
引文
[1]Adv.Funct.Mater.,2016,26,524-531,Highly-connected silicon-copper alloy mixture nanotubes as high rate and durable anode materials for lithium ion batteries,Hucheng Song,Hong Xiang Wang,Zixia Lin,Xiaofan Jiang,Linwei Yu,Jun Xu,Zhongwei Yu,Xiaowei Zhang,Yijie Liu,Ping He,Lijia Pan,Yi Shi,Haoshen Zhou and Kunji Chen
    [2]Nanoscale,2016,8,2613-2619,Highly cross-linked Cu/a-Si core–shell nanowires for ultralong cycle life and high rate lithium batteries,Hongxiang Wang,Hucheng Song,Zixia Lin,Xiaofan Jiang,Xiaowei Zhang,Linwei Yu,Jun Xu,Lijia Pan,Junzhuan Wang,Mingbo Zheng,Yi Shi and Kunji Chen
    [3]Nano Energy 2016,19,511-521,Hierarchical Nano-branched c-Si/Sn O2 Nanowires for High Areal Capacity and Stable Lithium-Ion Battery,Hucheng Song,Hong Xiang Wang,Zixia Lin,Linwei Yu,Xiaofan Jiang,Zhongwei Yu,Jun Xu,Lijia Pan,Mingbo Zheng,Yi Shi,and Kunji Chen

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