Crystallined hybrid carbon was synthesized by the catalytic carbonization of biomass(Pinus kesiya sawdust)at1100℃and in-situ growth of carbon nanofibers(CNFs)at 750℃from acetylene.The microstructure of the composite was characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),transmission electron microscopy(TEM)and high-resolution transmission electron microscopy(HRTEM).It was found that highly crystallined carbon composed of well-aligned graphene layers with interlayer spacing of 0.34 nm can be formed by catalytic carbonization of biomass.However,the structure of the in-situ growing CNFs is lessaligned.Based on the results of the investigation,the formation mechanism of the crystallined hybrid carbon was discussed.Owning to synergistic effect of the highly crystallined carbon and the conductive network formed by CNFs,the crystallined hybrid carbon shows 32.6%lower electrical resistivity than biocarbon.When being used as anode material of lithium-ion batteries(LIBs),the crystallined hybrid carbon and the biocarbon have nearly the same first coulombic efficiencies(CEs),however,the former has a discharge capacity of 67%higher than the latter since the second cycle.
Shuhe LiuShuchun ZhaoYaochun YaoPeng DongChao Yang
以稻壳为原料,采用镁热还原方法制备孔隙和孔壁主要为纳米尺度的多孔硅材料.作为锂离子电池负极材料,在30 m A/g恒流充放下,多孔硅具有首次充电容量为2 387 m Ah/g,50次充放循环后,充电容量保持率为23.3%.考虑到稻壳的资源丰富、廉价易得和可持续利用特点,镁热还原工艺的低成本性以及稻壳制备的多孔硅具有较好的电化学性能,此法有望制备实用的优质锂离子电池多孔硅负极材料.
Two kinds of porous silicon(PS) were synthesized by magnesiothermic reduction of rice husk silica(RHS) derived from the oxidization of rice husks(RHs). One was obtained from oxidization/reduction at 500 ℃ of the unleached RHs, the other was synthesized from oxidization/reduction at 650 ℃ of the acidleached RHs. The structural difference of the above PS was compared: the former had a high pore volume(PV, 0.31 cm3/g) and a large specific surface area(SSA, 45.2 m^2/g), 138 % and 17 % higher than the latter, respectively. As anode materials for lithium ion batteries, the former had reversible capacity of 1 400.7 m Ah/g, 987 m Ah/g lower than the latter; however, after 50 cycles, the former had 64.5 % capacity retention(907 m Ah/g), which was 41.2 % higher than the latter(555.7 m Ah/g). These results showed that the electrochemical performance of PS was significantly affected by its pore structures, and low reduction temperature played the key role in increasing its porosity, and therefore improving its cycling performance.
