A 3D structured composite of carbon nanofibers @ MnO2 on copper foil is reported here as a binder free anode of lithium ion batteries, with high capacity, fast charge/discharge rate and good stability. Carbon nanofibe...A 3D structured composite of carbon nanofibers @ MnO2 on copper foil is reported here as a binder free anode of lithium ion batteries, with high capacity, fast charge/discharge rate and good stability. Carbon nanofiber yarns were synthesized directly over copper foil through a floating catalyst method. The growth of carbon nanofiber yarns was significantly enhanced by mechanical polishing of the copper foils, which can be attributed to the increased surface roughness and surface area of the copper foils. MnO2 was then grown over carbon nanofibers through spontaneous reduction of potassium permanganate by the carbon nanofibers. The obtained composites of carbon nanofibers@MnO2 over copper foil were tested as an anode in lithium ion batteries and they show superior electrochemical performance. The initial reversible capacity of carbon nanofibers@MnO2 reaches up to around 998 mAh.g-1 at a rate of 60 mmA.g-l based on the mass of carbon nanofibers and MnO2. The carbon nanofibers @ MnO2 electrodes could deliver a capacity of 630 mAh.g-1 at the beginning and maintain a capacity of 440 mmAh.g-1 after 105 cycles at a rate of 600 mA.g-~. The high initial capacity can be attributed to the presence of porous carbon nanofiber yarns which have good electrical conductivity and the MnO2 thin film which makes the entire materials electrochemically active. The high cyclic stability of carbon nanofibers@MnO2 can be ascribed to the MnO2 thin film which can accommodate the volume expansion and shrinking during charge and discharge and the good contact of carbon nanofibers with MnO2 and copper foil.展开更多
As the anode active substance of lithium ions battery(LIB),the low conductivity/ion diffusivity and large volume changes of tungsten oxide(WO_(3))lead to its serious polarization during the lithiation/delithiation pro...As the anode active substance of lithium ions battery(LIB),the low conductivity/ion diffusivity and large volume changes of tungsten oxide(WO_(3))lead to its serious polarization during the lithiation/delithiation process,decreasing the cycling stability.To address these challenges,a binder-free anode consisting of nitrogen-doped tungsten oxide nanosheets,encapsulated in carbon layers(N-doped WO_(3)@CL)and entangled with carbon nanotubes macro-films(CMF),was successfully synthesized through a combination of hydrothermal and online assembly method.Compared with the pristine tungsten oxide entangled with carbon nanotubes macro-films(WO_(3)@CMF),the synthesized N-doped WO_(3)@CL@CMF as a binder-free LIB anode demonstrated better electrochemical performance,which could be attributed to(1)surface defects of WO_(3)created by N dopant providing more channels to improve Li^(+)diffusion,(2)the N-doped WO_(3)@CL with a flower-like structure shortening the diffusion length of Li^(+)ions and further leading to high Li^(+)incorporation,and(3)carbon layers and carbon nanotubes synergistically alleviating the large volume change of the N-doped WO_(3)@CL@CMF electrode during the charging and discharging process.The present study offers insights into employing nitrogen dopant and a carbon matrix to mediate the conductivity and wrapped structure in the WO_(3)semiconductor powder,which provides an important strategy for large-scale design of the binder-free LIB anode with high performance.展开更多
MoO_2 nanocrystals(NCs) on Ni foam were simply synthesized via a facile hydrothermal method and a dip-coating method. It was worth noting that ultrafine interconnected MoO_2 nanocrystals(about 10 nm) were uniformly an...MoO_2 nanocrystals(NCs) on Ni foam were simply synthesized via a facile hydrothermal method and a dip-coating method. It was worth noting that ultrafine interconnected MoO_2 nanocrystals(about 10 nm) were uniformly anchored on Ni foam to fabricate a particular three-dimensional architecture, which may provide more active sites and shorter transmission pathways for lithium ions. As binder-free anode, MoO_2 NCs on Ni foam deliver a high initial discharge capacity of 990 mAh·g^(-1) and retain a reversible capacity of 924 mAh· g(-1) after 100 cycles at a current density of 0.1 C. More importantly, when the current density returns from 2 C to 0.1 C, the capacity recovers to 910 mAh·g(-1)(about 92% of the original high capacity), suggesting excellent cycling stability and rate capability. The particular 3 D electrode as binder-free anode makes it a promising anode candidate for high-performance lithium-ion batteries.展开更多
作为电池的重要组成部分,电极材料直接影响电池的能量密度。电极材料在制作过程中往往会添加粘结剂以稳定极片结构,但粘结剂的加入会降低电极材料的比容量,影响其离子迁移速率。通过在经水热反应刻蚀的钛箔/网上原位生长二氧化钛(TiO 2...作为电池的重要组成部分,电极材料直接影响电池的能量密度。电极材料在制作过程中往往会添加粘结剂以稳定极片结构,但粘结剂的加入会降低电极材料的比容量,影响其离子迁移速率。通过在经水热反应刻蚀的钛箔/网上原位生长二氧化钛(TiO 2)得到无粘结剂TiO 2/Ti纳米线阵列电极,并系统地研究不同钛基底及水热反应温度对TiO 2/Ti纳米线阵列电极物理性能和电化学性能的影响。结果表明,不同钛基底及水热反应温度均对生长的TiO 2纳米线的形貌和电化学性能有重要影响。其中通过220℃水热反应生长在钛网(0.15 mm)上的TiO 2纳米线呈蛛网状,具有较大的比表面积,属于锐钛矿型TiO 2,储钠过程主要由赝电容效应控制,且具有优秀的电化学性能:首周放电比容量为986 mAh g^-1,库伦效率为21.7%;随后放电比容量逐渐稳定在240 mAh g^-1左右;循环200周后放电比容量仍能达到228 mAh g^-1,库伦效率稳定在99.3%左右;即使在3200 mA g^-1的超大电流密度下,放电比容量仍能达到152 mAh g^-1。无粘结剂电极材料极大可以有限地提升电极材料的比容量,对未来高能量密度电池体系的设计具有一定的理论意义和参考价值。展开更多
Eliminating the usage of metal current collectors and binders in traditional battery electrode configuration is an effective strategy to significantly improve the capacities of lithium ion batteries (LIBs). Herein, we...Eliminating the usage of metal current collectors and binders in traditional battery electrode configuration is an effective strategy to significantly improve the capacities of lithium ion batteries (LIBs). Herein, we demonstrate the construction of porous vanadium nitride (VN) nanosheet network in situ grown on nitrogen-rich (N-rich) carbon textile (N-C@P-VN) as lightweight and binder-free anode for LIBs. The N-rich carbon textile is used both as the current collector and host to store Li^(+), thus improving the specific capacities of binder-free VN anode and meanwhile reducing the inert mass of the whole cell. Moreover, the open spaces in carbon textile and vertically aligned pores in VN nanosheet network can not only provide an expressway for Li+ and e− transport, but also afford more active sites. As a result, the binder-free N-C@P-VN anode maintains a specific capacity of 1,040 mAh·g^(−1) (or an areal capacity of 2.6 mAh·cm^(−2)) after 100 cycles at 0.1 mA·cm^(−2) in half cell. Moreover, in an assembled N-C@P-VN//LiFePO4 full cell, it exhibits an areal capacity of 1.7 mAh·cm^(−2) after 300 cycles at 0.1 C. The synergistic strategy of N-C substrate and porous VN network could be applied to guide rational design of similar N-C@nitride or sulfide hybrid systems with corresponding sulfur-doped carbon textile as the substrate.展开更多
基金VISTA-a basic research program funded by Statoil,conducted in close collaboration with The Norwegian Academy of Science and Letters which is gratefully acknowledged
文摘A 3D structured composite of carbon nanofibers @ MnO2 on copper foil is reported here as a binder free anode of lithium ion batteries, with high capacity, fast charge/discharge rate and good stability. Carbon nanofiber yarns were synthesized directly over copper foil through a floating catalyst method. The growth of carbon nanofiber yarns was significantly enhanced by mechanical polishing of the copper foils, which can be attributed to the increased surface roughness and surface area of the copper foils. MnO2 was then grown over carbon nanofibers through spontaneous reduction of potassium permanganate by the carbon nanofibers. The obtained composites of carbon nanofibers@MnO2 over copper foil were tested as an anode in lithium ion batteries and they show superior electrochemical performance. The initial reversible capacity of carbon nanofibers@MnO2 reaches up to around 998 mAh.g-1 at a rate of 60 mmA.g-l based on the mass of carbon nanofibers and MnO2. The carbon nanofibers @ MnO2 electrodes could deliver a capacity of 630 mAh.g-1 at the beginning and maintain a capacity of 440 mmAh.g-1 after 105 cycles at a rate of 600 mA.g-~. The high initial capacity can be attributed to the presence of porous carbon nanofiber yarns which have good electrical conductivity and the MnO2 thin film which makes the entire materials electrochemically active. The high cyclic stability of carbon nanofibers@MnO2 can be ascribed to the MnO2 thin film which can accommodate the volume expansion and shrinking during charge and discharge and the good contact of carbon nanofibers with MnO2 and copper foil.
基金This study was financially supported by the National Natural Science Foundation of China[Grant No.22062008]Supported by the program of Qingjiang Excellent Young Talents,Jiangxi University of Science and Technology[Grant No.JXUSTQJBJ2020008]+2 种基金the Special Fund for Postgraduate Innovation of Jiangxi Province[Grant No.YC2020-S458 and YC2021-S569]National Training Program for College Students’Innovation and Entrepreneurship[Grant No.202110407005X]the Postdoctoral Science Foundation of Jiangxi Province[Grant No.2019KY56 and 2018RC02].
文摘As the anode active substance of lithium ions battery(LIB),the low conductivity/ion diffusivity and large volume changes of tungsten oxide(WO_(3))lead to its serious polarization during the lithiation/delithiation process,decreasing the cycling stability.To address these challenges,a binder-free anode consisting of nitrogen-doped tungsten oxide nanosheets,encapsulated in carbon layers(N-doped WO_(3)@CL)and entangled with carbon nanotubes macro-films(CMF),was successfully synthesized through a combination of hydrothermal and online assembly method.Compared with the pristine tungsten oxide entangled with carbon nanotubes macro-films(WO_(3)@CMF),the synthesized N-doped WO_(3)@CL@CMF as a binder-free LIB anode demonstrated better electrochemical performance,which could be attributed to(1)surface defects of WO_(3)created by N dopant providing more channels to improve Li^(+)diffusion,(2)the N-doped WO_(3)@CL with a flower-like structure shortening the diffusion length of Li^(+)ions and further leading to high Li^(+)incorporation,and(3)carbon layers and carbon nanotubes synergistically alleviating the large volume change of the N-doped WO_(3)@CL@CMF electrode during the charging and discharging process.The present study offers insights into employing nitrogen dopant and a carbon matrix to mediate the conductivity and wrapped structure in the WO_(3)semiconductor powder,which provides an important strategy for large-scale design of the binder-free LIB anode with high performance.
基金Funded by the National Natural Science Foundation of China(51506155)
文摘MoO_2 nanocrystals(NCs) on Ni foam were simply synthesized via a facile hydrothermal method and a dip-coating method. It was worth noting that ultrafine interconnected MoO_2 nanocrystals(about 10 nm) were uniformly anchored on Ni foam to fabricate a particular three-dimensional architecture, which may provide more active sites and shorter transmission pathways for lithium ions. As binder-free anode, MoO_2 NCs on Ni foam deliver a high initial discharge capacity of 990 mAh·g^(-1) and retain a reversible capacity of 924 mAh· g(-1) after 100 cycles at a current density of 0.1 C. More importantly, when the current density returns from 2 C to 0.1 C, the capacity recovers to 910 mAh·g(-1)(about 92% of the original high capacity), suggesting excellent cycling stability and rate capability. The particular 3 D electrode as binder-free anode makes it a promising anode candidate for high-performance lithium-ion batteries.
文摘作为电池的重要组成部分,电极材料直接影响电池的能量密度。电极材料在制作过程中往往会添加粘结剂以稳定极片结构,但粘结剂的加入会降低电极材料的比容量,影响其离子迁移速率。通过在经水热反应刻蚀的钛箔/网上原位生长二氧化钛(TiO 2)得到无粘结剂TiO 2/Ti纳米线阵列电极,并系统地研究不同钛基底及水热反应温度对TiO 2/Ti纳米线阵列电极物理性能和电化学性能的影响。结果表明,不同钛基底及水热反应温度均对生长的TiO 2纳米线的形貌和电化学性能有重要影响。其中通过220℃水热反应生长在钛网(0.15 mm)上的TiO 2纳米线呈蛛网状,具有较大的比表面积,属于锐钛矿型TiO 2,储钠过程主要由赝电容效应控制,且具有优秀的电化学性能:首周放电比容量为986 mAh g^-1,库伦效率为21.7%;随后放电比容量逐渐稳定在240 mAh g^-1左右;循环200周后放电比容量仍能达到228 mAh g^-1,库伦效率稳定在99.3%左右;即使在3200 mA g^-1的超大电流密度下,放电比容量仍能达到152 mAh g^-1。无粘结剂电极材料极大可以有限地提升电极材料的比容量,对未来高能量密度电池体系的设计具有一定的理论意义和参考价值。
基金This work was supported by the National Natural Science Foundation of China(No.21872008)the Natural Science Foundation of Beijing,China(No.2212019)Beijing Institute of Technology Research Fund Program for Young Scholars(Nos.3100011182019 and 3100011182128).We would also thank the Analysis&Testing Center of Beijing Institute of Technology measurements.
文摘Eliminating the usage of metal current collectors and binders in traditional battery electrode configuration is an effective strategy to significantly improve the capacities of lithium ion batteries (LIBs). Herein, we demonstrate the construction of porous vanadium nitride (VN) nanosheet network in situ grown on nitrogen-rich (N-rich) carbon textile (N-C@P-VN) as lightweight and binder-free anode for LIBs. The N-rich carbon textile is used both as the current collector and host to store Li^(+), thus improving the specific capacities of binder-free VN anode and meanwhile reducing the inert mass of the whole cell. Moreover, the open spaces in carbon textile and vertically aligned pores in VN nanosheet network can not only provide an expressway for Li+ and e− transport, but also afford more active sites. As a result, the binder-free N-C@P-VN anode maintains a specific capacity of 1,040 mAh·g^(−1) (or an areal capacity of 2.6 mAh·cm^(−2)) after 100 cycles at 0.1 mA·cm^(−2) in half cell. Moreover, in an assembled N-C@P-VN//LiFePO4 full cell, it exhibits an areal capacity of 1.7 mAh·cm^(−2) after 300 cycles at 0.1 C. The synergistic strategy of N-C substrate and porous VN network could be applied to guide rational design of similar N-C@nitride or sulfide hybrid systems with corresponding sulfur-doped carbon textile as the substrate.
