利用一种简易的模板法制成多孔石墨烯框架(pG),将石榴状的钒酸锌(Zn_(3)V_(3)O_(8))纳米球包覆在多孔石墨烯纳米片里,形成独特结构的钒酸锌/多孔石墨烯(Zn_(3)V_(3)O_(8)/p G)纳米复合材料.作为一种锂离子电池负极材料,Zn_(3)V_(3)O_(8)...利用一种简易的模板法制成多孔石墨烯框架(pG),将石榴状的钒酸锌(Zn_(3)V_(3)O_(8))纳米球包覆在多孔石墨烯纳米片里,形成独特结构的钒酸锌/多孔石墨烯(Zn_(3)V_(3)O_(8)/p G)纳米复合材料.作为一种锂离子电池负极材料,Zn_(3)V_(3)O_(8)/p G表现出良好的储锂性能,在1000 mA g^(-1)的电流密度下经过200次循环后达到586 mAh g^(-1)的可逆容量.Zn_(3)V_(3)O_(8)/p G良好的电化学性能主要归因于其独特的多孔网状碳结构为钒酸锌纳米球在充放电循环过程中的体积变化提供缓冲空间,以及石榴状的钒酸锌纳米球与多孔石墨烯之间形成的良好协同效应.展开更多
利用低温液相法合成了钒酸锂-多壁碳纳米管(LiV_3O_8-(w)MWCNTs)(w分别为0、1%、2%、3%、4%和5%)复合正极材料.采用X-射线衍射(X-ray diffraction,XRD)和扫描电镜(scanning electron microscope,SEM)对复合材料的晶型和结构进行了表征....利用低温液相法合成了钒酸锂-多壁碳纳米管(LiV_3O_8-(w)MWCNTs)(w分别为0、1%、2%、3%、4%和5%)复合正极材料.采用X-射线衍射(X-ray diffraction,XRD)和扫描电镜(scanning electron microscope,SEM)对复合材料的晶型和结构进行了表征.XRD分析结果表明,复合材料仍为单斜晶系;SEM图谱显示,LiV_3O_8材料附着在MWCNTs的网状结构上,且使颗粒细化;通过恒流充放电测试、循环伏安(cyclic voltammetry,CV)及交流阻抗谱(electrochemical impedance spectroscopy,EIS)技术对材料的电化学性能进行了研究,结果表明,按LiV_3O_8质量百分比复合3%MWCNTs的LiV_3O_8-(3%)MWCNTs复合材料具有最佳的电化学性能,在0.1 C充放电倍率条件下,其首次放电比容量为364.5 m Ah/g,循环50次后放电比容量仍有292.2 m Ah/g,容量保持率为80.2%,而纯LiV_3O_8材料的首次放电比容量为308.2m Ah/g,循环50次后容量保持率仅为55.4%;采用MWCNTs与LiV_3O_8复合可使锂离子在材料颗粒间的电荷转移阻抗变小,有利于Li+的嵌入和脱出.展开更多
γ-LiV2O5/VO2 composites were synthesized through thermal lithiation reaction of mixed valence (+4, +5) vanadium oxides by lithium bromide. The phase evolution, morphology and discharge behavior at 500 ℃ were investi...γ-LiV2O5/VO2 composites were synthesized through thermal lithiation reaction of mixed valence (+4, +5) vanadium oxides by lithium bromide. The phase evolution, morphology and discharge behavior at 500 ℃ were investigated by thermal gravimeter/differential thermal analysis (TG/DTA), X-ray diffraction(XRD), scanning electron microscopy(SEM) and specific surface analysis(BET). The mixed vanadium oxides are obtained from the pyrolytic decomposition of ammonium metavanadate, with V6O13 as main phase. Results show that the lithiation reaction begins at about 258 ℃, with γ-LiV2O5 and VO2(B) as the product. VO2(B) can transit to VO2(R) in the range of 400-500 ℃, following by grain growth and crystalline development with the increase of temperature and roasting time. The ratio of γ-LiV2O5 to VO2 can be modified by the additive content of lithium bromide. A lattice shearing model about the nucleation and growth of LixV2O5 and VO2(B) inside mixed valence (+4, +5) vanadium oxides (e.g. V6O13, V3O7) is speculated, which is relative to oxygen-/vacancy-diffusion and structural evolution inspired by lithium-insertion. The open-circuit voltage of 2.6 V is observed in the single cell of Li-B/LiCl-KCl/(γ-LiV2O5/VO2) at 500 ℃, and the specific capacities of 146 and 167 mA·h/g (cut-off voltage 1.4 V) are measured for the positive material at 100 mA/cm2 and 200 mA/cm2, respectively.展开更多
采用溶胶-凝胶法制备LiV 3-y Nb y O 8(y=0、0.03、0.06和0.09)正极材料。通过XRD、SEM和电化学性能测试,研究材料的结构、形貌和电化学性能。Nb掺杂不改变钒酸锂(LiV 3O 8)的单斜层状结构,但可增大晶胞体积,掺杂后仍为亚微米颗粒。当y=...采用溶胶-凝胶法制备LiV 3-y Nb y O 8(y=0、0.03、0.06和0.09)正极材料。通过XRD、SEM和电化学性能测试,研究材料的结构、形貌和电化学性能。Nb掺杂不改变钒酸锂(LiV 3O 8)的单斜层状结构,但可增大晶胞体积,掺杂后仍为亚微米颗粒。当y=0.06时,电化学性能最好,在1.8~4.0 V循环具有良好的倍率性能,电流为0.1 A/g、5.0 A/g时的放电比容量分别为396.5 mAh/g、124.9 mAh/g。电化学性能改善的主要原因是:Nb掺杂提高了材料的Li+扩散系数,降低了电荷间的转移电阻。展开更多
文摘利用一种简易的模板法制成多孔石墨烯框架(pG),将石榴状的钒酸锌(Zn_(3)V_(3)O_(8))纳米球包覆在多孔石墨烯纳米片里,形成独特结构的钒酸锌/多孔石墨烯(Zn_(3)V_(3)O_(8)/p G)纳米复合材料.作为一种锂离子电池负极材料,Zn_(3)V_(3)O_(8)/p G表现出良好的储锂性能,在1000 mA g^(-1)的电流密度下经过200次循环后达到586 mAh g^(-1)的可逆容量.Zn_(3)V_(3)O_(8)/p G良好的电化学性能主要归因于其独特的多孔网状碳结构为钒酸锌纳米球在充放电循环过程中的体积变化提供缓冲空间,以及石榴状的钒酸锌纳米球与多孔石墨烯之间形成的良好协同效应.
文摘利用低温液相法合成了钒酸锂-多壁碳纳米管(LiV_3O_8-(w)MWCNTs)(w分别为0、1%、2%、3%、4%和5%)复合正极材料.采用X-射线衍射(X-ray diffraction,XRD)和扫描电镜(scanning electron microscope,SEM)对复合材料的晶型和结构进行了表征.XRD分析结果表明,复合材料仍为单斜晶系;SEM图谱显示,LiV_3O_8材料附着在MWCNTs的网状结构上,且使颗粒细化;通过恒流充放电测试、循环伏安(cyclic voltammetry,CV)及交流阻抗谱(electrochemical impedance spectroscopy,EIS)技术对材料的电化学性能进行了研究,结果表明,按LiV_3O_8质量百分比复合3%MWCNTs的LiV_3O_8-(3%)MWCNTs复合材料具有最佳的电化学性能,在0.1 C充放电倍率条件下,其首次放电比容量为364.5 m Ah/g,循环50次后放电比容量仍有292.2 m Ah/g,容量保持率为80.2%,而纯LiV_3O_8材料的首次放电比容量为308.2m Ah/g,循环50次后容量保持率仅为55.4%;采用MWCNTs与LiV_3O_8复合可使锂离子在材料颗粒间的电荷转移阻抗变小,有利于Li+的嵌入和脱出.
基金supported by the National Key Research and Development Program of China(2016YFB0100204)National Natural Science Foundation of China(21373028)+1 种基金Joint Funds of the National Natural Science Foundation of China(U1564206)Major achievements Transformation Project for Central University in Beijing,Beijing Science and Technology Project(D151100003015001)~~
文摘以海藻酸为碳源,采用流变相法制备出碳包覆改性的Li_3V_2(PO_4)_3/C(LVP/C)正极材料。X射线衍射(XRD)结果显示所合成样品均为标准的单斜结构Li_3V_2(PO_4)_3。扫描电子显微镜(SEM)和透射电子显微镜(TEM)图像显示所合成的LVP/C活性材料颗粒尺寸较均匀。海藻酸质量分数为10%的LVP/C样品展现出最优的循环稳定性。0.1C放电电流下,首次放电容量为117.5 m Ah?g^(-1),50周循环后容量保持在116.5m Ah?g^(-1)。LVP/C-10%材料在3.0–4.3 V和3.0–4.8 V电压范围内循环50周后的容量保持率分别为99.1%和76.8%,明显优于未包覆的LVP材料。海藻酸基碳包覆层可以有效增加材料的电子导电性、缓冲活性材料在脱嵌锂过程产生的机械损伤,进而提高材料的电化学性能。
基金Project(2003AA05510) supported by the National High-Tech Research and Development Program of China
文摘γ-LiV2O5/VO2 composites were synthesized through thermal lithiation reaction of mixed valence (+4, +5) vanadium oxides by lithium bromide. The phase evolution, morphology and discharge behavior at 500 ℃ were investigated by thermal gravimeter/differential thermal analysis (TG/DTA), X-ray diffraction(XRD), scanning electron microscopy(SEM) and specific surface analysis(BET). The mixed vanadium oxides are obtained from the pyrolytic decomposition of ammonium metavanadate, with V6O13 as main phase. Results show that the lithiation reaction begins at about 258 ℃, with γ-LiV2O5 and VO2(B) as the product. VO2(B) can transit to VO2(R) in the range of 400-500 ℃, following by grain growth and crystalline development with the increase of temperature and roasting time. The ratio of γ-LiV2O5 to VO2 can be modified by the additive content of lithium bromide. A lattice shearing model about the nucleation and growth of LixV2O5 and VO2(B) inside mixed valence (+4, +5) vanadium oxides (e.g. V6O13, V3O7) is speculated, which is relative to oxygen-/vacancy-diffusion and structural evolution inspired by lithium-insertion. The open-circuit voltage of 2.6 V is observed in the single cell of Li-B/LiCl-KCl/(γ-LiV2O5/VO2) at 500 ℃, and the specific capacities of 146 and 167 mA·h/g (cut-off voltage 1.4 V) are measured for the positive material at 100 mA/cm2 and 200 mA/cm2, respectively.
文摘采用溶胶-凝胶法制备LiV 3-y Nb y O 8(y=0、0.03、0.06和0.09)正极材料。通过XRD、SEM和电化学性能测试,研究材料的结构、形貌和电化学性能。Nb掺杂不改变钒酸锂(LiV 3O 8)的单斜层状结构,但可增大晶胞体积,掺杂后仍为亚微米颗粒。当y=0.06时,电化学性能最好,在1.8~4.0 V循环具有良好的倍率性能,电流为0.1 A/g、5.0 A/g时的放电比容量分别为396.5 mAh/g、124.9 mAh/g。电化学性能改善的主要原因是:Nb掺杂提高了材料的Li+扩散系数,降低了电荷间的转移电阻。
