MoO3/reduced graphene oxide composites as anode material for sodium ion batteries

MoO₃/reduced graphene oxide (MoO₃/RGO) composites were successfully prepared via a facile one-step hydrothermal method, and evaluated as anode materials for sodium ion batteries (SIBs). The crystal structures, morphologies and electrochemical properties of the as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge tests, respectively. The results show that the introduction of RGO can enhance the electrochemical performances of MoO₃/RGO composites. MoO₃/RGO composite with 6 wt% RGO delivers the highest reversible capacity of ~208 mA h g⁻¹ at 50 mA g⁻¹ after 50 cycles with good cycling stability and excellent rate performance for SIBs. The excellent sodium storage performance of MoO₃/RGO should be attributed to the synergistic effect between MoO₃ and RGO, which offers the increased electrical conductivity, the facilitated electron transfer ability and the buffering of volume expansion.     

Synthesis of CuGeO3/reduced graphene oxide nanocomposite by hydrothermal reduction for high performance Li-ion battery anodes

Nowadays, Lithium-ion batteries (LIBs) are prevalently applied in numerous areas, leading to increasing demand of innovative electrodes with high specific capacities. An advanced CuGeO₃/reduced graphene oxide (rGO) structure is designed and fabricated as the anode material taking the advantage of considerable capacity offered by CuGeO₃ and stable framework constructed by rGO. The as-prepared CuGeO₃ with 30 wt% GO addition exhibits the best electrochemical performance. Specifically, a reversible charge capacity of 909 mAh·g⁻¹ with high coulombic efficiency of 91.49% at the current density of 100 mA g⁻¹ after 200 cycles is demonstrated, and the rate capacity retains 747.6 mAh·g⁻¹ with 91.59% capacity retention. These results indicate that the CuGeO₃/rGO composite holds great potential in next-generation LIBs.     

Hollow ZnSnO3 cubes@carbon/reduced graphene oxide ternary composite as anode of lithium ion batteries with enhanced electrochemical performance

The ternary composite, carbon coated hollow ZnSnO₃ (ZS@C) cubes encapsulated in reduced graphene oxide sheets (ZS@C/rGO), was synthesized via low-temperature coprecipitation and colloid electrostatic self-assembly. The uniform carbon-coating layer not only plays a role in buffering the volume change of ZnSnO₃ cubes in the charging/discharging processes, but also forms three-dimensional network with the cooperation of graphene to maintain the structural integrity and improve the electrical conductivity. The results show that the reduced graphene oxide sheets encapsulated ZS@C microcubes with a typical core-shell structure of ~700 nm in size exhibit an improved electrochemical performance compared with bare ZS@C microcubes. The ZS@C/rGO electrode delivered an initial discharge capacity of 1984 mA h g⁻¹ at a current density of 0.1 A g⁻¹ and maintained a capacity of 1040 mA h g⁻¹ after 45 cycles. High specific capacity and superior cycle stability indicate that the ZS@C/rGO composite has a great potential for the application of lithium-ion anode material.     

Hematite nanoflakes as anode electrode materials for rechargeable lithium-ion batteries

Hematite (α-Fe₂O₃) nanoflakes and nanocubes were synthesized by liquid-solid-solution method and their properties as anode electrode materials for rechargeable Li⁺-ion batteries were measured. When changing the water to ethanol volume ratio in the synthesis system, the nanocrystals can be changed from α-Fe₂O₃ to α-FeOOH, with shapes being tuned from nanoflakes to nanocubes, non-uniform particles and nanowires. When assembled as the anode electrode materials in rechargeable Li⁺-ion batteries, the hematite nanoflakes showed one more plateau in the first discharge progress of the voltage-composition curves than hematite nanocrystals with other shapes in the literature. X-ray diffraction, high-resolution transmission electron microscope and electrochemical data showed that this extra plateau came from the formation of Li₂Fe₃O₄ nanoclusters and amorphous Li₂O. This experiment showed that like sizes, shapes of nanocrystals may also affect the detailed electrochemical progress.     

Amorphous CoS nanoparticle/reduced graphene oxide composite as high-performance anode material for sodium-ion batteries

Transition metal sulfides have been proved as promising candidates of anode materials for sodium-ion batteries (SIBs) due to their high sodium storage capacity, low cost and enhanced safety. In this study, the amorphous CoS nanoparticle/reduced graphene oxide (CoS/rGO) composite has been fabricated by a facile one-step electron beam radiation route to in situ decorate amorphous CoS nanoparticle on the rGO nanosheets. Benefiting from the small particle size (~2 nm), amorphous structure, and electronic conductive rGO nanosheets, the CoS/rGO nanocomposite exhibits high sodium storage capacity (440 mAh g⁻¹ at 100 mA g⁻¹), excellent cycling stability (277 mAh g⁻¹ after 100 cycles at 200 mA g⁻¹, 79.6% capacity retention) and high rate capability (149.5 mAh g⁻¹ at 2 A g⁻¹). The results provide a facile approach to fabricate promising amorphous and ultrafine metal sulfides for energy storage.     

Preparation of manganese monoxide@reduced graphene oxide nanocomposites with superior electrochemical performances for lithium-ion batteries

Manganese monoxide (MnO) nanowire@reduced graphene oxide (rGO) nanocomposites are synthesized using a simple hydrothermal method combined with a calcination process. The structural and morphological characterization of the composites indicates that the MnO nanowires homogeneously anchor on both sides of the cross-linked rGO. The nanocomposites exhibit a high surface area of 126.5?m² g^?1. When employed as an anode material for lithium-ion batteries, the nanocomposites exhibit a reversible capacity of 1195 mAh g^?1 at a current density of 0.1?A?g^?1, with a high charge-discharge efficiency of 99.2% after 150 cycles. The three-dimensional architecture of the present materials exhibits high porosity and electron conductivity, significantly shortening the diffusion path of lithium ions and accelerating their reaction with the electrolyte, which greatly improves the lithium-ion storage properties. These excellent electrochemical performances make the composite a promising electrode material for lithium-ion batteries.     

One-step hydrothermal synthesis of Sb2S3/reduced graphene oxide nanocomposites for high-performance sodium ion batteries anode materials

Sb₂S₃/reduced graphene oxide (SSR) nanocomposites were successfully synthesized through a facile one-step hydrothermal process, as used as anode materials for sodium ion batteries (SIBs). The characterization and electrochemical performance of the as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption isotherms, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge tests, respectively. The results show that the introduction of reduced graphene oxide (RGO) can improve the electrochemical performances of SSR nanocomposites. SSR nanocomposites with 10 wt% RGO exhibits the highest reversible capacity of 581.2 mAh g⁻¹ at the current density of 50 mA g⁻¹ after 50 cycles, and excellent rate performance for SIBs. The improved electrochemical performance is attributed to the smaller Sb₂S₃ nanoparticles dispersed on RGO crumpled structure and synergetic effects between Sb₂S₃ and RGO matrix, which can increase specific surface area and improve electrical conductivity, reduce sodium ion diffusion distance, and effectively buffer volume changes during cycling process.     

Synthesis of reduced graphene oxide/tungsten trioxide nanocomposite electrode for high electrochemical performance

A facile and well-controllable reduced graphene oxide/tungsten trioxide (rGO/WO₃) nanocomposite electrode was successfully synthesized via an electrostatic assembly route at 350 rpm for 24 h. In this study, hexagonal-phase WO₃ (h-WO₃) nanofiber was well distributed on rGO sheets by applying optimal processing parameters. The as-synthesized rGO/WO₃ nanocomposite electrode was compared with pure h-WO₃ electrode. A maximum specific capacitance of 85.7 F g⁻¹ at a current density of 0.7 A g⁻¹ was obtained for the rGO/WO₃ nanocomposite electrode, which showed better electrochemical performance than the WO₃ electrode. The incorporation of WO₃ into rGO could prevent the restacking of rGO and provide favourable surface adsorption sites for intercalation/de-intercalation reactions. The impedance studies demonstrated that the rGO/WO₃ nanocomposite electrode exhibited lower resistance because of the superior conductivity of rGO that improved ion diffusion into the electrode. To evaluate the contribution of WO₃ to the rGO/WO₃ nanocomposite, the influence of mass loading of WO₃ on the capacitance was investigated.     

Synthesis of Mn3O4/N-doped graphene hybrid and its improved electrochemical performance for lithium-ion batteries

Mn₃O₄/N-doped graphene (Mn₃O₄/NG) hybrids were synthesized by a simple one-pot hydrothermal process. The scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray powder diffraction (XRD), Thermogravimetric analysis (TG), Raman Spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the microstructure, crystallinity and compositions. It is demonstrated that Mn₃O₄ nanoparticles are high-dispersely anchored onto the individual graphene nanosheets, and also found that, in contrast with pure Mn₃O₄ obtained without graphene added, the introduction of graphene effectively restricts the growth of Mn₃O₄ nanoparticles. Simultaneously, the anchored well-dispersed Mn₃O₄ nanoparticles also play a role as spacers in preventing the restacking of graphene sheets and producing abundant nanoscale porous channels. Hence, it is well anticipated that the accessibility and reactivity of electrolyte molecules with Mn₃O₄/NG electrode are highly improved during the electrochemical process. As the anode material for lithium ion batteries, the Mn₃O₄/NG hybrid electrode displays an outstanding reversible capacity of 1208.4 mAh g⁻¹ after 150 cycles at a current density of 88 mA g⁻¹, even still retained 284 mAh g⁻¹ at a high current density of 4400 mA g⁻¹ after 10 cycles, indicating the superior capacity retention, which is better than those of bare Mn₃O₄, and most other Mn₃O₄/C hybrids in reported literatures. Finally, the superior performance can be ascribed to the uniformly distribution of ultrafine Mn₃O₄ nanoparticles, successful nitrogen doping of graphene and favorable structures of the composites.     

A review study on the recent advances in developing the heteroatom-doped graphene and porous graphene as superior anode materials for Li-ion batteries

Graphene materials, with their distinctively fascinating physicochemical properties, have been receiving great attention as favorable anode materials for use in Li-ion batteries (LIBs). However, the high affinity of graphene nanosheets to restack and agglomerate during electrode assembly reduces the deliverable specific capacity due to the limited available surface area and active sites for Li-ion storage. Furthermore, the high aspect ratio of graphene nanosheets could result in long transport pathways for Li-ions and consequently limiting the rate performance. These drawbacks can be significantly improved via the functionalization of graphene by various heteroatoms and also the formation of porous graphene, adding unique beneficial properties to the inherent characteristics of graphene. Here, a comprehensive review of porous and/or heteroatom doped graphene anode materials for LIBs is presented, which summarizes in detail the main recent literature from their procedure, optimum synthesis parameters, relevant mechanisms, and the obtained morphology/structure to their electrochemical performance as the LIBs anode. Finally, the research gaps are proposed. This review will promote the basic understanding and further development of porous and/or doped graphene materials as anodes for LIBs.     

High reversible capacity of SnO2/graphene nanocomposite as an anode material for lithium-ion batteries

A gas–liquid interfacial synthesis approach has been developed to prepare SnO₂/graphene nanocomposite. The as-prepared nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller measurements. Field emission scanning electron microscopy and transmission electron microscopy observation revealed the homogeneous distribution of SnO₂ nanoparticles (2–6 nm in size) on graphene matrix. The electrochemical performances were evaluated by using coin-type cells versus metallic lithium. The SnO₂/graphene nanocomposite prepared by the gas–liquid interface reaction exhibits a high reversible specific capacity of 1304 mAh g⁻¹ at a current density of 100 mA g⁻¹ and excellent rate capability, even at a high current density of 1000 mA g⁻¹, the reversible capacity was still as high as 748 mAh g⁻¹. The electrochemical test results show that the SnO₂/graphene nanocomposite prepared by the gas–liquid interfacial synthesis approach is a promising anode material for lithium-ion batteries.     

In-situ synthesis of reduced graphene oxide wrapped Mn3O4 nanocomposite as anode materials for high-performance lithium-ion batteries

We report a novel in-situ symbiosis method to prepare reduced graphene oxide wrapped Mn₃O₄ nanoparticles (rGO/Mn₃O₄) with uniform size about 50 nm as anodes for lithium-ion batteries (LIBs), which can simplify the preparation process and effectively reduce pollution. The rGO/Mn₃O₄ nanocomposite exhibited a reversible specific capacity of 795.5 mAh g^?1 at 100 mA g^?1 after 200 cycles (capacity retention: 87.4%), which benefits from the unique structural advantages and the synergistic effect of rGO and Mn₃O₄. The Mn₃O₄ nanoparticles encapsulated among the rGO nanosheets exhibited good electrochemical activity, and the multilayer wrinkled rGO sheets provided a stable 3D conduction channel for Li⁺/e^? transport. The rGO/Mn₃O₄ nanocomposite is a promising anode candidate for advanced LIBs with excellent cycling performance and rate performance. Furthermore, this new preparation method can be extended to green and economical synthesis of advanced graphene/manganese-based nanocomposites.     

Reduced graphene oxide anchored with δ-MnO2 nanoscrolls as anode materials for enhanced Li-ion storage

We developed a one-pot in situ synthesis procedure to form nanocomposite of reduced graphene oxide (RGO) sheets anchored with 1D δ-MnO₂ nanoscrolls for Li-ion batteries. The as-prepared products were characterized by X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The electrochemical performance of the δ-MnO₂ nanoscrolls/RGO composite was measured by galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy. The results show that the δ-MnO₂ nanoscrolls/RGO composite displays superior Li-ion battery performance with large reversible capacity and high rate capability. The first discharge and charge capacities are 1520 and 810 mAh g⁻¹, respectively. After 50 cycles, the reversible discharge capacity is still maintained at 528 mAh g⁻¹ at the current density of 100 mAh g⁻¹. The excellent electrochemical performance is attributed to the unique nanostructure of the δ-MnO₂ nanoscrolls/RGO composite, the high capacity of MnO₂ and superior electrical conductivity of RGO.     

Strontium incorporated hydroxyapatite/hydrothermally reduced graphene oxide nanocomposite as a cytocompatible material

Hydroxyapatite (HA)/reduced graphene oxide (rGO) composites with different mol% of strontium and 1?wt% of GO were fabricated through a green hydrothermal reduction method and this combination has been reported for the first time. All the synthesized composites had strontium incorporated onto the crystal structure of HA as can be substantiated from XRD and FTIR. This paper also discusses a possible role of surface and pore characteristics on the in vitro cytocompatibility and the contribution of graphene oxide in directing the nucleation points resulting in dispersed strontium incorporated hydroxyapatite (SHA) based on P-31 NMR and TEM studies. In addition, a reasonable speculation also has been made to correlate the cytocompatibility with the selective occupancy of strontium ions in the apatite lattice. The in vitro cytocompatibility of SHA/rGO composites (SHAG) has been evaluated using cell proliferation tests with MG-63 cells, under a wider range of concentrations (1000–7.8?µg/ml) and by varying Sr/(Ca+Sr) molar ratio. SHAG with strontium substitution of 10?mol% exhibited the maximum viability among the samples tested. These results suggest that the SHAG composites will be a promising material for biomedical application.     

One-step microwave-assisted synthesis of Sb2O3/reduced graphene oxide composites as advanced anode materials for sodium-ion batteries

Sb₂O₃/reduced graphene oxide (RGO) composites were prepared through a facile microwave-assisted reduction of graphite oxide in SbCl₃ precursor solution, and investigated as anode material for sodium-ion batteries (SIBs). The experimental results show that a maximum specific capacity of 503 mA h g⁻¹ is achieved after 50 galvanostatic charge/discharge cycles at a current density of 100 mA g⁻¹ by optimizing the RGO content in the composites and an excellent rate performance is also obtained due to the synergistic effect between Sb₂O₃ and RGO. The high capacity, superior rate capability and excellent cycling performance of Sb₂O₃/RGO composites demonstrate their excellent sodium-ion storage ability and show their great potential as electrode materials for SIBs.     

Hybrid CuO-Co3O4 nanosphere/RGO sandwiched composites as anode materials for lithium-ion batteries

Hybrid CuO-Co₃O₄ nanosphere building blocks have been embedded between the layered nanosheets of reduced graphene oxides with a three dimensional (3D) hybrid architecture (CuO-Co₃O₄-RGO), which are successfully applied as enhanced anodes for lithium-ion batteries (LIBs). The CuO-Co₃O₄-RGO sandwiched nanostructures exhibit a reversible capacity of~847 mA·h·g^-1 after 200 cycles' cycling at 100 mA·g^-1 with a capacity retention of 79%. The CuO-Co₃O₄-RGO compounds show superior electrochemical properties than the comparative CuO-Co₃O₄, Co₃O₄ and CuO anodes, which may be ascribed to the following reasons:the hybridizing multicomponent can probably give the complementary advantages; the mutual benefit of uniformly distributing nanospheres across the layered RGO nanosheets can avoid the agglomeration of both the RGO nanosheets and the CuO-Co₃O₄ nanospheres; the 3D storage structure as well as the graphene wrapped composite could enhance the electrical conductivity and reduce volume expansion effect associated with the discharge-charge process.     

Graphenothermal reduction synthesis of MnO/RGO composite with excellent anodic behaviour in lithium ion batteries

Mn(II) oxide/graphene oxide (MnO/RGO) composites were synthesized by an easy and cost-effective graphenothermal reduction method. The surface morphology, structure, chemical composition and electrochemical behaviour of the resulting composites were investigated in detail. The MnO/RGO composite exhibited a high surface area (115.7 m²/g), which led to the high discharge capacity, enhanced cycling stability, and outstanding rate capability as anode in Li-ion batteries (LIBs). The MnO/RGO composite exhibited an higher initial discharge capacity of 1607 mA h/g at a current density of 100 mA/g and maintained 94% of its reversible capacity over 100 consecutive cycles. Furthermore, MnO/RGO composite could preserve a significantly higher capacity of 847 mA h/g for 150 cycles even at a high current density of 250 mA/g. The excellent electrochemical properties result from the existence of highly conductive RGO and a short transportation span for both Li-ions and electrons. The developed MnO/RGO composite materials hold highly promising prospects in LIBs.     

A biomass-derived biochar-supported NiS/C anode material for lithium-ion batteries

Nickel sulfides are perfect anode materials for high-capacity and low-cost lithium-ion batteries (LIBs); however, with the shortcoming of polysulfide intermediate dissolution, volume expansion exceeding the limit during cycling also restricts their development. Herein, NiS/C composite materials are successfully anchored on chestnut shell fluff (CSF)-derived biochar by a glucose-auxiliary hydrothermal method along with an annealing treatment. The CSF biochar acts as an effective electron transmission channel for the rapid lithiation/delithiation of NiS and as a fixed sulfur carrier for inhibiting the dissolution of polysulfide. Glucose restrains the accumulation of NiS particles and then transforms into uniform amorphous carbon during annealing, which is more effective in buffering for rapid volume variation. Moreover, the CSF-NiS/C electrode exhibits a remarkable specific capacity of 1522.8 mAh g^-1 (0.1 A g^-1) and distinguished rate performance with 295 mAh g^-1 capacity (3 A g^-1), which are better than those of the pure NiS/C anode material displays. Researchers may be inspired by both of these reasonable design and synthesis strategies that are beneficial for the development of high-performance nickel-based sulfide anode materials for LIBs.     

Nano-sized cobalt oxide/mesoporous carbon sphere composites as negative electrode material for lithium-ion batteries

A new type of nano-sized cobalt oxide compounded with mesoporous carbon spheres (MCS) as negative electrode material for lithium-ion batteries was synthesized. The composite containing about 20 wt.% cobalt oxide exhibits a reversible capacity of 703 mAh/g at a constant current density of 70 mA/g between 0.01 and 3.0 V (vs. Li⁺/Li), and remains a capacity retention of 77% after the 30th cycle. The improvement could be attributed to that the MCS had a good electronic conductivity and severed as dispersing medium to prevent cobalt oxide nanoparticles from aggregating, and the mesopores (cobalt oxide not fully occupied) can provide the enough space to buffer the volume change during the Li-ion insertion and extraction reactions in cobalt oxide nanoparticles.     

Fabrication of NiO-ZnO/RGO composite as an anode material for lithium-ion batteries

NiO-ZnO/RGO composite was obtained by the annealing of an Ni (OH)₂-Zn (OH)₂/RGO precursor, which has been fabricated by in situ ultrasonic agitation. Moreover, the NiO-ZnO nanoflakes are evenly distributed on the RGO sheets based on the scanning electron microscope (SEM) and transmission electron microscope (TEM) characterization results. When the NiO-ZnO/RGO composite was used as an anode material in lithium-ion batteries (LIBs), the electrodes exhibited a high reversible capacity of 1017 mA h/g at a current density of 100 mA/g after 200 cycles and a specific capacity of 458 mA h/g at 500 mA/g even after 400 cycles. The electrode even reached a capacity of 185 mA h/g at a current density of 2000 mA/g. The excellent electrochemical properties of the NiO-ZnO/RGO composite might be attributable to the NiO-ZnO nanoflakes offering rich electrochemical reaction sites and shortening the diffusion length for lithium ion (Li⁺), as well as the RGO sheets improving the transfer rates of Li⁺ and electron during the charge-discharge process.