Lithium–sulfur batteries have been recognised as highly promising next-generation batteries, due to their low cost and high theoretical energy density. Despite numerous advances in this technology over the last decad...Lithium–sulfur batteries have been recognised as highly promising next-generation batteries, due to their low cost and high theoretical energy density. Despite numerous advances in this technology over the last decade, its commercialisation is still a challenge that has not yet been achieved. Many efforts have been made to improve the problems that these batteries present, mainly by investigating different cathode manufacturing strategies, testing novel Li anodes, new additives in the electrolytes, and modified separators or interlayers. However, the characteristics of the current collectors used in the preparation of the electrodes have been rarely addressed. Three commercial collectors are commonly used in basic research on Li–S batteries: Al foil, carbon coated Al foil (Al-C), and carbon paper (gas diffusion layer, GDL). In this work, a detailed study of the electrochemical response of these commercial collectors has been carried out. The tests were carried out on two S composites formed by carbons of a different natures, commercial carbon black and synthetic N-doped graphene. In addition, the S impregnation method was different, using either melt diffusion at 155 ℃ or ethylenediamine as S solvent, respectively. In both systems, the results were similar – the electrodes supported on GDL delivered higher specific capacities than those supported on Al and Al-C, with minimal differences between the two. Of the different collector properties examined to explain this behaviour, namely Al corrosion, electrical conductivities, surface-level composition, and surface texture, only the latter had a significant effect in the performance of GDL-based electrodes. SEM images revealed a rough and cracked surface formed by the agglomerated carbon particles that give rise to a complex pore system, predominantly consisting of macropores. All of these features are beneficial for a better anchoring of the active material on the collector surface, in addition to enhancing the wettability of the electrolyte and favouring reaction kinetics. In contrast, the Al-based collector possesses a very smooth and non-porous surface, detrimental to both the active material-substrate interface and the active material impregnation by the electrolyte.展开更多
A C/Ni composite was prepared via thermal decomposition of a nickel oleate complex at 700℃,yielding disperse Ni nanocrystals with an average size of 20 nm,encapsulated by carbon nanosheets as deduced from transmissio...A C/Ni composite was prepared via thermal decomposition of a nickel oleate complex at 700℃,yielding disperse Ni nanocrystals with an average size of 20 nm,encapsulated by carbon nanosheets as deduced from transmission electron microscopy(TEM)images and confirmed from X-ray photoelectron spectroscopy(XPS).Furthermore,the X-ray diffraction pattern revealed a good ordering of the carbon layers,forced by the Ni encapsulation to adopt a bending structure.Considering the close interaction between the graphitized framework and the metallic nanoparticles we have studied the properties of the composite as an anode for Li-ion batteries.Compared with other nanostructured synthetic carbons,this carbon composite has a low voltage hysteresis and a modest irreversible capacity value,properties that play a significant role in its behaviour as electrodes in full cell configuration.At moderate rate values,0.25 C,the electrode delivers an average capacity value around 723 mAh·g^−1 on cycling,among the highest values so far reported for this carbon type.At higher rate values,1 C,the average capacity values delivered by the cell on cycling decrease,around 205 mAh·g^−1,but it maintains good capacity retention,a coulombic efficiency close to 100%after the first cycles and recovery of the capacity values when the rate is restored from 3 to 0.1 C.展开更多
基金This work was supported by Ministerio de Economia y Compet-itividad(Project MAT2017-87541-R)Junta de Andalucfa(Group FQM-175).
文摘Lithium–sulfur batteries have been recognised as highly promising next-generation batteries, due to their low cost and high theoretical energy density. Despite numerous advances in this technology over the last decade, its commercialisation is still a challenge that has not yet been achieved. Many efforts have been made to improve the problems that these batteries present, mainly by investigating different cathode manufacturing strategies, testing novel Li anodes, new additives in the electrolytes, and modified separators or interlayers. However, the characteristics of the current collectors used in the preparation of the electrodes have been rarely addressed. Three commercial collectors are commonly used in basic research on Li–S batteries: Al foil, carbon coated Al foil (Al-C), and carbon paper (gas diffusion layer, GDL). In this work, a detailed study of the electrochemical response of these commercial collectors has been carried out. The tests were carried out on two S composites formed by carbons of a different natures, commercial carbon black and synthetic N-doped graphene. In addition, the S impregnation method was different, using either melt diffusion at 155 ℃ or ethylenediamine as S solvent, respectively. In both systems, the results were similar – the electrodes supported on GDL delivered higher specific capacities than those supported on Al and Al-C, with minimal differences between the two. Of the different collector properties examined to explain this behaviour, namely Al corrosion, electrical conductivities, surface-level composition, and surface texture, only the latter had a significant effect in the performance of GDL-based electrodes. SEM images revealed a rough and cracked surface formed by the agglomerated carbon particles that give rise to a complex pore system, predominantly consisting of macropores. All of these features are beneficial for a better anchoring of the active material on the collector surface, in addition to enhancing the wettability of the electrolyte and favouring reaction kinetics. In contrast, the Al-based collector possesses a very smooth and non-porous surface, detrimental to both the active material-substrate interface and the active material impregnation by the electrolyte.
基金Ministerio de Economíay Competitividad(No.MAT2017-87541-R)and Junta de Andalucía(Group FQM-175).F.J.S.UCO for fellowship“Universidad de Córdoba.Becas Semillero de Investigación”.E.R.C.thanks to project RTI2018-099668-BC22 of Ministerio de Ciencia,Innovacióny Universidades+1 种基金UMA18-FEDERJA-126 of Junta de Andalucía and FEDER funds.J.C.V.Support from UCLM through the 2019-GRIN-27165 grant.
文摘A C/Ni composite was prepared via thermal decomposition of a nickel oleate complex at 700℃,yielding disperse Ni nanocrystals with an average size of 20 nm,encapsulated by carbon nanosheets as deduced from transmission electron microscopy(TEM)images and confirmed from X-ray photoelectron spectroscopy(XPS).Furthermore,the X-ray diffraction pattern revealed a good ordering of the carbon layers,forced by the Ni encapsulation to adopt a bending structure.Considering the close interaction between the graphitized framework and the metallic nanoparticles we have studied the properties of the composite as an anode for Li-ion batteries.Compared with other nanostructured synthetic carbons,this carbon composite has a low voltage hysteresis and a modest irreversible capacity value,properties that play a significant role in its behaviour as electrodes in full cell configuration.At moderate rate values,0.25 C,the electrode delivers an average capacity value around 723 mAh·g^−1 on cycling,among the highest values so far reported for this carbon type.At higher rate values,1 C,the average capacity values delivered by the cell on cycling decrease,around 205 mAh·g^−1,but it maintains good capacity retention,a coulombic efficiency close to 100%after the first cycles and recovery of the capacity values when the rate is restored from 3 to 0.1 C.