近年来,锌离子电容器(ZIHCs)因其环境友好性和优异的电化学性能而备受关注。然而,ZIHCs的研究体系尚不成熟,为改善ZIHCs的储能动力学和循环稳定性等问题,亟需研发出低成本和高性能的碳基电极材料。本工作以海藻酸钠为碳前驱体,五硼酸铵...近年来,锌离子电容器(ZIHCs)因其环境友好性和优异的电化学性能而备受关注。然而,ZIHCs的研究体系尚不成熟,为改善ZIHCs的储能动力学和循环稳定性等问题,亟需研发出低成本和高性能的碳基电极材料。本工作以海藻酸钠为碳前驱体,五硼酸铵为氮源和硼源,采用一步水热活化策略合成了氮/硼含量较高的分级多孔炭(NBSPC)。这种策略可以有效重塑炭的多孔结构,产生大量的活性位点,贡献额外的赝电容,从而提高其电化学性能。以NBSPC为正极构建了锌离子电容器,其在40 A g^(-1)的超高电流密度下,可以实现85.4 mAh g^(-1)优异的倍率性能,并在10 A g^(-1)的电流密度下可以稳定循环15000次,容量保持率高达94.5%。展开更多
Defect engineering by heteroatom doping gives carbon materials some new characteristics such as a different electronic structure and a high electrochemical activity,making them suitable for high-performance applicatio...Defect engineering by heteroatom doping gives carbon materials some new characteristics such as a different electronic structure and a high electrochemical activity,making them suitable for high-performance applications.N-doping has been widely investigated because of its similar atom radius to carbon,high electronegativity as well as many different configurations.We summarize the preparation methods and properties of N-doped carbon materials,and discuss their possible use in sodium ion storage.The relationships between N content/configuration and crystallinity,electronic conductivity,wettability,chemical reactivity as well as sodium ion storage performance are discussed.展开更多
A transformation of naphthalene-based coalescenced mesophase pitch(NMP)to mesophase microbeads was achieved by heating a mixture of NMP and fullerene(C_(60)).This is different from the conventional process of the liqu...A transformation of naphthalene-based coalescenced mesophase pitch(NMP)to mesophase microbeads was achieved by heating a mixture of NMP and fullerene(C_(60)).This is different from the conventional process of the liquid-phase carbonization of isotropic pitch to the emergence of carbon microbeads in the matrix and finally their growth to form a 100%anisotropic bulk meso-phase,but rather a reverse transformation.The effects of C_(60) loading and reaction temperature on the morphological transformation of mesophase were investigated by polarizing optical and scanning electron microscopies.The physical changes in the NMP induced by C_(60) were characterized by thermogravimetric analysis,Fourier transform infrared spectroscopy,X-ray diffractometry and Raman spectroscopy.The results show that the coalesced NMP can be converted to a spherical type at 300-320℃ with the addition of 5%C_(60),and the size of the mesophase microbeads increases with increasing temperature.Furthermore,a model is established to ex-plain the unique induction effect of C_(60) in the transformation process.This work makes the morphological transformation of MP con-trollable,and provides a new idea for the understanding and research of mesophase pitch.展开更多
石墨是锂离子电池使用最广泛的负极材料,提高石墨的球形度和密度是提高其能量密度的重要方法。本文报道了通过高剪切湿法制粒技术制备具有高振实密度石墨颗粒的一种简单方法,将两种石墨材料致密化为两种石墨颗粒,即湿法制粒的洋葱状碳(W...石墨是锂离子电池使用最广泛的负极材料,提高石墨的球形度和密度是提高其能量密度的重要方法。本文报道了通过高剪切湿法制粒技术制备具有高振实密度石墨颗粒的一种简单方法,将两种石墨材料致密化为两种石墨颗粒,即湿法制粒的洋葱状碳(WG-GOC)和湿法制粒的人造石墨(WG-AG)。结果发现,与制粒前的原始石墨相比,WG-GOC的振实密度提高了约34%,WG-AG的振实密度提高了约44%。当作为锂离子电池负极时,在电流密度为50 mA g^(-1)时,WGGOC和WG-AG的体积容量分别增加了约35%和55%。此外,WG-GOC的倍率性能也得到了明显改善。在电流密度为2000 mA g^(-1)时,WG-GOC的体积比容量增加了169.1%。电化学性能的显著提升得益于所制石墨颗粒具有更高的振实密度。因此,利用湿法制粒法开发了一种制备高振实密度石墨负极的简易方法,这有利于高容量电极的发展。展开更多
硅是目前已知比容量(4200 m Ah·g-1)最高的锂离子电池负极材料,但由于其巨大的体积效应(>300%),硅电极材料在充放电过程中会粉化而从集流体上剥落,使得活性物质与活性物质、活性物质与集流体之间失去电接触,同时不断形成新的固...硅是目前已知比容量(4200 m Ah·g-1)最高的锂离子电池负极材料,但由于其巨大的体积效应(>300%),硅电极材料在充放电过程中会粉化而从集流体上剥落,使得活性物质与活性物质、活性物质与集流体之间失去电接触,同时不断形成新的固相电解质层(SEI),最终导致电化学性能的恶化。本文介绍了硅作为锂离子电池负极材料的储能及容量衰减机理,总结了通过硅材料的选择和结构设计来解决充放电过程中巨大体积效应的相关工作,并讨论了一些具有代表性的硅基复合材料的制备方法、电化学性能和相应机理,重点介绍了硅炭复合材料。另外,介绍了一些电极的处理方法和其提高硅基负极材料电化学性能的可能机理。最后,对硅基负极材料存在的问题进行了分析,并展望了其研究前景。展开更多
文摘近年来,锌离子电容器(ZIHCs)因其环境友好性和优异的电化学性能而备受关注。然而,ZIHCs的研究体系尚不成熟,为改善ZIHCs的储能动力学和循环稳定性等问题,亟需研发出低成本和高性能的碳基电极材料。本工作以海藻酸钠为碳前驱体,五硼酸铵为氮源和硼源,采用一步水热活化策略合成了氮/硼含量较高的分级多孔炭(NBSPC)。这种策略可以有效重塑炭的多孔结构,产生大量的活性位点,贡献额外的赝电容,从而提高其电化学性能。以NBSPC为正极构建了锌离子电容器,其在40 A g^(-1)的超高电流密度下,可以实现85.4 mAh g^(-1)优异的倍率性能,并在10 A g^(-1)的电流密度下可以稳定循环15000次,容量保持率高达94.5%。
文摘Defect engineering by heteroatom doping gives carbon materials some new characteristics such as a different electronic structure and a high electrochemical activity,making them suitable for high-performance applications.N-doping has been widely investigated because of its similar atom radius to carbon,high electronegativity as well as many different configurations.We summarize the preparation methods and properties of N-doped carbon materials,and discuss their possible use in sodium ion storage.The relationships between N content/configuration and crystallinity,electronic conductivity,wettability,chemical reactivity as well as sodium ion storage performance are discussed.
文摘A transformation of naphthalene-based coalescenced mesophase pitch(NMP)to mesophase microbeads was achieved by heating a mixture of NMP and fullerene(C_(60)).This is different from the conventional process of the liquid-phase carbonization of isotropic pitch to the emergence of carbon microbeads in the matrix and finally their growth to form a 100%anisotropic bulk meso-phase,but rather a reverse transformation.The effects of C_(60) loading and reaction temperature on the morphological transformation of mesophase were investigated by polarizing optical and scanning electron microscopies.The physical changes in the NMP induced by C_(60) were characterized by thermogravimetric analysis,Fourier transform infrared spectroscopy,X-ray diffractometry and Raman spectroscopy.The results show that the coalesced NMP can be converted to a spherical type at 300-320℃ with the addition of 5%C_(60),and the size of the mesophase microbeads increases with increasing temperature.Furthermore,a model is established to ex-plain the unique induction effect of C_(60) in the transformation process.This work makes the morphological transformation of MP con-trollable,and provides a new idea for the understanding and research of mesophase pitch.
文摘石墨是锂离子电池使用最广泛的负极材料,提高石墨的球形度和密度是提高其能量密度的重要方法。本文报道了通过高剪切湿法制粒技术制备具有高振实密度石墨颗粒的一种简单方法,将两种石墨材料致密化为两种石墨颗粒,即湿法制粒的洋葱状碳(WG-GOC)和湿法制粒的人造石墨(WG-AG)。结果发现,与制粒前的原始石墨相比,WG-GOC的振实密度提高了约34%,WG-AG的振实密度提高了约44%。当作为锂离子电池负极时,在电流密度为50 mA g^(-1)时,WGGOC和WG-AG的体积容量分别增加了约35%和55%。此外,WG-GOC的倍率性能也得到了明显改善。在电流密度为2000 mA g^(-1)时,WG-GOC的体积比容量增加了169.1%。电化学性能的显著提升得益于所制石墨颗粒具有更高的振实密度。因此,利用湿法制粒法开发了一种制备高振实密度石墨负极的简易方法,这有利于高容量电极的发展。
文摘硅是目前已知比容量(4200 m Ah·g-1)最高的锂离子电池负极材料,但由于其巨大的体积效应(>300%),硅电极材料在充放电过程中会粉化而从集流体上剥落,使得活性物质与活性物质、活性物质与集流体之间失去电接触,同时不断形成新的固相电解质层(SEI),最终导致电化学性能的恶化。本文介绍了硅作为锂离子电池负极材料的储能及容量衰减机理,总结了通过硅材料的选择和结构设计来解决充放电过程中巨大体积效应的相关工作,并讨论了一些具有代表性的硅基复合材料的制备方法、电化学性能和相应机理,重点介绍了硅炭复合材料。另外,介绍了一些电极的处理方法和其提高硅基负极材料电化学性能的可能机理。最后,对硅基负极材料存在的问题进行了分析,并展望了其研究前景。
