Si-based nanostructure composites have been intensively investigated as anode materials for next-generation lithium-ion batteries because of their ultra-high-energy storage capacity. However, it is still a great challenge to fabricate a perfect structure satisfying all the requirements of good electrical conductivity, robust matrix for buffering large volume expansion, and intact linkage of Si particles upon long-term cycling. Here, we report a novel design of Si-based multicomponent three-dimensional (3D) networks in which the Si core is capped with phytic acid shell layers through a facile high-energy ball-milling method. By mixing the functional Si with graphene oxide and functionalized carbon nanotube, we successfully obtained a homogeneous and conductive rigid silicon-based gel through complexation. Interestingly, this Si-based gel with a fancy 3D cross-linking structure could be writable and printable. In particular, this Si-based gel composite delivers a moderate specific capacity of 2711 mA h g–1 at a current density of 420 mA g–1 and retained a competitive discharge capacity of more than 800.00 mA h g–1 at the current density of 420 mA g–1 after 700 cycles. We provide a new method to fabricate durable Si-based anode material for next-generation high-performance lithium-ion batteries.Keywords: anode materials; carbon nanotube; graphene; high-energy ball milling; hydrogel; Li-ion batteries; Si;

Fe-N-C composite catalyst was prepared by thermal decomposition of chelate precursors based on Fe(III) central ions and o-phenylenediamine ligands. Scanning electron microscopy characterization showed that the crumpled carbon micro- and nano-sheets were intertwined and formed a free-standing tremella-like 3D structure. Notrogen adsorption/desorption experiments revealed that the composite contained ample micro-pores and meso-pores and had a specific surface area of 290 m2 g−1. Graphitic carbon and multi-crystal Fe3C as main components were confirmed by X-ray diffraction, and N-doping in the general form of graphite-N and pyridine-N was also verified by X-ray photoelectron spectroscopy. The electrochemical measurements showed that the tremella-like Fe-N-C composite catalyzed oxygen reduction through a four-electron path in an alkaline solution, and its activity was comparable to that of the commercial Pt/C catalyst. After 2000 cycles, the limiting current density of the Fe-N-C catalytic electrode only decreased less than 5%, and the half-wave potential negatively shifted 5 mV, suggesting that the Fe-N-C composite catalyst had better catalytic stability than the commercial Pt/C catalyst.Graphical abstractThe tremella-like Fe-N-C composite catalyst composed of graphite- and pyridine-N doped graphitic nanosheets and multi-crystal Fe3C nanophases was prepared, and demonstrated equivalent catalytic activity but more durable stability towards oxygen reduction reaction as compared with the commercial Pt/C.Download high-res image (130KB)Download full-size image

A facile hydrothermal fabrication was applied to hybridize in-site grown flower-like Ni–Fe layered double hydroxides (Ni–Fe LDHs) and carbon black (CB) nanoparticles. The well-conductive CB particles were dispersed homogeneously onto the petals of the Ni–Fe LDH flowers via a combination of electrostatic forces and ripening growth, and remarkably promoted the charge-transfer capability of the LDHs. The hybridized Ni–Fe LDH/CB composite electrode exhibited excellent rate performance that retained both a high capacity and steady cycle life at a large charge–discharge current, and was highly competitive serving as a high-rate alkaline battery cathode.

We report a Ni–Al layered double hydroxide (LDH)–graphene superlattice composite via alternating assembly of the exfoliated thin flakes with opposite charges that show stable high-rate performance for alkaline battery cathodes.

Here we illustrate a facile and economical strategy for the bulk production of aqueous graphene dispersions via a simple ball milling process assisted with non-ionic industrial surfactant. Moreover, this surfactant is readily removed using ethanol to acquire high-quality graphene flakes. The fabricated graphene electrode shows excellent high-rate charge–discharge performance suitable for supercapacitor applications.

A facile solvothermal solution has been introduced to hybridize pre-sintered LiMn1/3Ni1/3Co1/3O2 (LMNC) nanocrystals and ethylene glycol reduced graphene oxide (EGRGO) nanosheets. Compared with the liquid-based growth of metallic oxide on graphene sheets, this approach not only ensures a high crystallinity of the LMNC particles from pre-sintering, but also realizes the intimate coupling of RGO with LMNC via covalent metal–oxygen bonds. The as-prepared EGRGO/LMNC nanocomposites have been characterized and confirmed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The fabricated EGRGO/LMNC composite electrodes have been investigated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The results reveal the markedly improved reversibility of the EGRGO/LMNC cathode toward lithium ion intercalation/extraction, which results in a large discharge capacity, high coulombic efficiency, and excellent rate performance. The elevated electrochemical capability of the EGRGO/LMNC cathode material is accounted for the better electrical conduction of the EGRGO nanosheets, highly stable crystal structure of the pre-sintered LMNC particles, and firm construction of the EGRGO/LMNC composite due to solvothermal hybridization.

•Nitrogen-doping and graphene-attachment in the carbon material are simultaneously achieved.•A thin layer of graphene attached on the wall of the mesoporous carbon material speeds up the charge transfer.•The graphene-modified nitrogen-doped carbon xerogel shows great potential for supercapacitor application.In this contribution, we report a reduced graphene oxide (rGO)-modified nitrogen-doped carbon xerogel, which could be easily prepared by pyrolysis of melamine-formaldehyde (MF) resins that are polymerized hydrothermally in an aqueous GO dispersion. Scanning electron microscopy, transmission electron microscopy, Fourier-transformed infrared spectrometry, and nitrogen adsorption-desorption method were employed to reveal the morphologies and structures of the prepared carbon xerogel. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge were used to investigate the electrochemical properties. The results showed that the charge transfer barrier of the mesoporous nitrogen-doped carbon xerogel was decreased evidently, owing to the modification of a layer of rGO on its wall, and the xerogel demonstrated a capacitance of as high as 205 F g−1 at the current of 1 A g−1.A facile synthesis of rGO-modified, N-doped carbon material for supercapacitor application.

Here we illustrate a simple and moderate electrochemical strategy to simultaneously harvest high-quality few-layer graphene flakes (<5 layers) from both a graphite anode and a graphite cathode in the protic ionic liquids. Specifically, the graphene flakes detached from cathodic graphite receive a defect healing.

A promising supercapacitor material based on graphene/polypyrrole (PPy) has been successfully synthesized via in situ oxidation polymerization of pyrrole monomers in aqueous graphene oxide (GO) solutions, followed by chemical reduction using ethylene glycol (EG). Unlike the commonly employed hydrazine reduction, the moderate EG reductant does not destruct the PPy conjugative structures, thus facilitating utilization of the electroactive conductive polymer. The morphologies and the structures of the as-prepared materials are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectra, and Fourier transform infrared spectroscopy (FTIR). And the electrochemical performance of the fabricated electrodes was evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The EG-RGO/PPy electrode shows large specific capacitance, high rate performance, and good charge–discharge stability as well. The excellent electrochemical capability is mainly accounted for the sound composite construction that improves the effective utilization of electroactive PPy component, accelerates shuttling the charged carriers, and alleviates the swelling/shrinkage of polymer chains.Highlights► A novel EG-RGO/PPy composite for supercapacitor application is well constructed. ► The well-soluble GO was dispersed in aqueous polymerisable aniline monomer solution to form stable GO/PPy structure. ► The EG reduced RGO/PPy can retain the PPy conductive conjugative frameworks. ► The EG-RGO/PPy electrode exhibits superior electrochemical capability as supercapacitor electrode.

We report a novel and facile synthesis of a high-quality graphene oxide (GO)–polyaniline (PANI) composite by in situ polymerization suitable for supercapacitor application. Unlike the use of the edged carboxyl groups of graphene sheets as linkers, the current work makes the most of the ample oxygenated groups on the basal plane of graphene sheets to combine with the amine nitrogens of the PANI chain. This is tactically realized by a carboxyl-functionalized process of GO with oxalic acid treatment prior to the combination. The as-constructed carboxyl-functionalized graphene oxide–polyaniline (CFGO–PANI) composite was roundly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transformed infrared spectrometry (FTIR), Raman spectrometry, and thermogravimetric analysis (TGA), and a stable, highly efficient charge-transfer configuration was disclosed and confirmed. The fabricated electrode composed of this CFGO–PANI material showed an excellent electrochemical capacitance performance with aqueous H2SO4 electrolytes.

Here we illustrate a simple and moderate electrochemical strategy to simultaneously harvest high-quality few-layer graphene flakes (<5 layers) from both a graphite anode and a graphite cathode in the protic ionic liquids. Specifically, the graphene flakes detached from cathodic graphite receive a defect healing.

We report a Ni–Al layered double hydroxide (LDH)–graphene superlattice composite via alternating assembly of the exfoliated thin flakes with opposite charges that show stable high-rate performance for alkaline battery cathodes.

We report a novel and facile synthesis of a high-quality graphene oxide (GO)–polyaniline (PANI) composite by in situ polymerization suitable for supercapacitor application. Unlike the use of the edged carboxyl groups of graphene sheets as linkers, the current work makes the most of the ample oxygenated groups on the basal plane of graphene sheets to combine with the amine nitrogens of the PANI chain. This is tactically realized by a carboxyl-functionalized process of GO with oxalic acid treatment prior to the combination. The as-constructed carboxyl-functionalized graphene oxide–polyaniline (CFGO–PANI) composite was roundly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transformed infrared spectrometry (FTIR), Raman spectrometry, and thermogravimetric analysis (TGA), and a stable, highly efficient charge-transfer configuration was disclosed and confirmed. The fabricated electrode composed of this CFGO–PANI material showed an excellent electrochemical capacitance performance with aqueous H2SO4 electrolytes.

A facile hydrothermal fabrication was applied to hybridize in-site grown flower-like Ni–Fe layered double hydroxides (Ni–Fe LDHs) and carbon black (CB) nanoparticles. The well-conductive CB particles were dispersed homogeneously onto the petals of the Ni–Fe LDH flowers via a combination of electrostatic forces and ripening growth, and remarkably promoted the charge-transfer capability of the LDHs. The hybridized Ni–Fe LDH/CB composite electrode exhibited excellent rate performance that retained both a high capacity and steady cycle life at a large charge–discharge current, and was highly competitive serving as a high-rate alkaline battery cathode.

Here we illustrate a facile and economical strategy for the bulk production of aqueous graphene dispersions via a simple ball milling process assisted with non-ionic industrial surfactant. Moreover, this surfactant is readily removed using ethanol to acquire high-quality graphene flakes. The fabricated graphene electrode shows excellent high-rate charge–discharge performance suitable for supercapacitor applications.