VO2 powder was synthesized by a new soft-chemical method using formaldehyde as a reductant. The influences of pyrolysis temperature and time on the phase and morphology of grains were investigated by using thermal gra...VO2 powder was synthesized by a new soft-chemical method using formaldehyde as a reductant. The influences of pyrolysis temperature and time on the phase and morphology of grains were investigated by using thermal gravimeter/differential thermal analysis(TG/DTA), X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy and scanning electron microscope(SEM). The positive electrode discharge performances of Li-B/LiCl-KCl/VO2 thermal battery at 500 ℃ were studied. The results show that the product is mainly non-crystal when the precursor of VO2 is heated below 300 ℃. VO2(B) appears and transits into VO2(R) irreversibly as the heating temperature rises. The open-circle voltage of VO2 is 2.6 V (vs Li-B), and the initial discharge voltage of 100 mA/cm2 at 500 ℃ is 2.52 V. The specific capacities of 100 mA/cm2 and 200 mA/cm2 at cut-off voltage of 1.4 V are 449 A·s/g and 539 A·s/g, respectively.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
基金Project(50002015) supported by the National Natural Science Foundation of China
文摘VO2 powder was synthesized by a new soft-chemical method using formaldehyde as a reductant. The influences of pyrolysis temperature and time on the phase and morphology of grains were investigated by using thermal gravimeter/differential thermal analysis(TG/DTA), X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy and scanning electron microscope(SEM). The positive electrode discharge performances of Li-B/LiCl-KCl/VO2 thermal battery at 500 ℃ were studied. The results show that the product is mainly non-crystal when the precursor of VO2 is heated below 300 ℃. VO2(B) appears and transits into VO2(R) irreversibly as the heating temperature rises. The open-circle voltage of VO2 is 2.6 V (vs Li-B), and the initial discharge voltage of 100 mA/cm2 at 500 ℃ is 2.52 V. The specific capacities of 100 mA/cm2 and 200 mA/cm2 at cut-off voltage of 1.4 V are 449 A·s/g and 539 A·s/g, respectively.
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.
