High capacity Li storage in sulfur and nitrogen dual-doped graphene networks
Introduction
Commercialization of Li ion batteries (LIBs) has been realized since graphite is used as anodes instead of Li discs, due to the excellent cycling stability of graphite. However, the limited Li storage capacity of graphite (up to 375 mAh/g) cannot satisfy ever increasing demand in the fields of electronics, vehicles, and storage of renewable energy. Carbon anodes with both high capacity and excellent cycling stability are in urgent need especially for the next-generation high capacity energy storage devices, such as Li–O2 batteries [1], [2] and Li ion capacitors (LIC) [3], [4].
To obtain high performance anodes, reforming carbon materials by designing nanostructures or heteroatom doping has been widely investigated. It has been demonstrated that reduced graphene oxide (RGO) can exhibit reversible capacity up to 1264 mAh/g [5], [6], [7], [8], [9], which is much higher than the capacity of traditional graphite. However, the irreversible stacking of graphene always occurs during direct thermal annealing due to the strong π-interactions. As the results, RGO usually composes of multi-layered graphene, which delivers a much lower Li storage capacity than the single layer graphene [10]. RGO anodes also suffer from low initial coulombic efficiency and fast capacity fading due to the existence of oxygen-containing functional groups [11], [12], [13], [14], [15]. Among the many efforts to fabricating stable porous graphene assemblies, the three dimensional (3D) graphene networks produced by chemical vapor deposition (CVD) processes have been reported to exhibit a highly porous structure and much higher electronic conductivity as compared to RGO. On the other hand, S or N doping of carbon materials has been found to be capable of significantly promoting the Li storage capacity [16], [17], [18]. Heteroatom doped carbons contain more defects through which Li ions can perpendicularly diffuse from outside to inside graphite layers, thus providing more storage regions [18]. Combining both the elaborate structure control and the heteroatom doping technique in CVD synthesis is promising to achieve a graphene-constructed material with extraordinary electrode performance. However, to be used as an electrode material, a scalable synthesis approach is necessary, which is difficult to be realized by the graphene growth on the limited surfaces of Cu foils or Ni foams.
In previous work, we have realized scalable synthesis of two dimensional nanomesh graphene by a CVD process using porous MgO layers as templates [19]. Here, we further present a scalable CVD synthesis of 3D networks composing of S and N dual-doped graphene (SNG), which exhibit an extraordinarily high Li storage capacity. The SNG was produced by a one-step CVD approach using MgSO4-containing whiskers as both templates and S source, and NH3 as N source. 3D networks composing of few-layered graphene were formed due to carbon deposition on the surface of the porous whisker templates. Energy dispersive spectrometer (EDS) mapping and X-ray photoelectron spectroscopy (XPS) analyses coupled with Raman analysis confirm that the S and N atoms have been evenly incorporated into the graphene frameworks via covalent bonds. As anode for LIBs, the SNG exhibits extremely high Li storage capacity (3525 mAh/g at the current density of 50 mA/g) and excellent cycling stability (remaining a reversible capacity of 400 mAh/g at 10 A/g after 2500 cycles), showing much better electrochemical performance as compared to the undoped graphene networks and the sole N or S-doped graphene networks. The reasons for the promotion are discussed. A full cell configuration with the SNG as anode and LiCoO2 as cathode, exhibits a high reversible capacity (164 mAh/g at 0.2 C) and excellent cycling performance.
Section snippets
Experimental
The as-synthesized basic magnesium sulfate whiskers are calcined at 650 °C and 1100 °C for 1 h to obtain porous MgSO4-containing and porous MgO whiskers, respectively. SNG is synthesized by a CVD approach using C2H4, NH3 and the as-produced porous MgSO4-containing whiskers as C source, N source and templates, respectively. In a typical synthesis, 20 g MgSO4 whiskers are fed into a vertical quartz reactor from the top hopper after the reaction temperature reached 650 °C in Ar flow. Then C2H4 and NH3
Results and discussion
The synthesis process of SNG is illustrated in Fig. 1. Cylindrical MgSO4-containing porous whiskers are prepared by calcining of basic magnesium sulfate whiskers, which serve as both templates and S source in a CVD process. 3D graphene networks are formed on the surface of the porous whiskers by C2H4 cracking, followed by an acid washing to remove the templates. Basic magnesium sulfate (5 Mg(OH)2·MgSO4·3H2O) whiskers were prepared by a previously-reported hydrothermal synthesis [20]. As shown in
Conclusions
In summary, 3D networks composing of S and N duel doped few-layered graphene have been synthesized by a CVD approach using the porous MgSO4-containing whiskers as templates and S source. The as-obtained SNG has a high S doping level (5.2 atom%) with a uniform distribution of S and N atoms in the highly porous networks. As anodes for LIBs, the SNG exhibits ultrahigh reversible capacity (3525 mAh/g at the current density of 50 mA/g), excellent rate performance and a long cycle life (more than 2500
Acknowledgments
This work was supported by the National Natural Science Foundation of China (No. 21206191) and the Science Foundation of China University of Petroleum, Beijing (No. 2462013YXBS007).
References (33)
- et al.
Free-standing single-walled carbon nanotube/SnO2 anode paper for flexible lithium-ion batteries
Carbon
(2012) - et al.
Microwave-assisted hydrothermal synthesis of nanostructured spinel Li4Ti5O12 as anode materials for lithium ion batteries
Electrochim Acta
(2012) - et al.
Three-dimensional core–shell Cu@Cu6Sn5 nanowires as the anode material for lithium ion batteries
J Power Sources
(2012) - et al.
Synthesis of entanglement structure in nanosized Li4Ti5O12/multi-walled carbon nanotubes composite anode material for Li-ion batteries by ball-milling-assisted solid-state reaction
J Power Sources
(2012) - et al.
Large-scale synthesis of macroporous SnO2 with/without carbon and their application as anode materials for lithium-ion batteries
J Alloy Compd
(2011) - et al.
Graphene/Si multilayer structure anodes for advanced half and full lithium-ion cells
Nano Energy
(2012) - et al.
Enhanced electrochemical performance of maghemite/graphene nanosheets composite as electrode in half and full Li-ion cells
Electrochim Acta
(2014) - et al.
Hierarchically porous graphene as a lithium–air battery electrode
Nano Lett
(2011) - et al.
Oxygen reduction reaction using MnO2 nanotubes/nitrogen-doped exfoliated graphene hybrid catalyst for Li–O2 battery applications
J Electrochem Soc
(2012) - et al.
An asymmetric hybrid nonaqueous energy storage cell
J Electrochem Soc
(2001)
Graphene surface-enabled lithium ion-exchanging cells: next-generation high-power energy storage devices
Nano Lett
A binder-free Ge-nanoparticle anode assembled on multiwalled carbon nanotube networks for Li-ion batteries
Chem Commun
Facile synthesis of silicon nanoparticles inserted into graphene sheets as improved anode materials for lithium-ion batteries
Chem Commun
Engineering empty space between si nanoparticles for lithium-ion battery anodes
Nano Lett
Lithium storage in carbon nanostructures
Adv Mater
Three-dimensional nanohybrids of Mn3O4/ordered mesoporous carbons for high performance anode materials for lithium-ion batteries
J Mater Chem
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