Preparation of cobalt sulfide@reduced graphene oxide nanocomposites with outstanding electrochemical behavior for lithium-ion batteries

Cobalt sulfide@reduced graphene oxide composites were prepared through a simple solvothermal method. The cobalt sulfide@reduced graphene oxide composites are composed of cobalt sulfide nanoparticles uniformly attached on both sides of reduced graphene oxide. Some favorable electrochemical performances in specific capacity, cycling performance, and rate capability are achieved using the porous nanocomposites as an anode for lithium-ion batteries. In a half-cell, it exhibits a high specific capacity of 1253.9 mA h g⁻¹ at 500 mA g⁻¹ after 100 cycles. A full cell consists of the cobalt sulfide@reduced graphene oxide nanocomposite anode and a commercial LiCoO₂ cathode, and is able to hold a high capacity of 574.7 mA h g⁻¹ at 200 mA g⁻¹ after 200 cycles. The reduced graphene oxide plays a key role in enhancing the electrical conductivity of the electrode materials; and it effectively prevents the cobalt sulfide nanoparticles from dropping off the electrode and buffers the volume variation during the discharge–charge process. The cobalt sulfide@reduced graphene oxide nanocomposites present great potential to be a promising anode material for lithium-ion batteries.

Cobalt sulfide@reduced graphene oxide nanocomposites obtained through a dipping and hydrothermal process, exhibit ascendant lithium-ion storage properties.     

Rice husk-derived nano-SiO2 assembled on reduced graphene oxide distributed on conductive flexible polyaniline frameworks towards high-performance lithium-ion batteries

By combining rice husk-derived nano-silica and reduced graphene oxide and then polymerizing PANI by in situ polymerization, we created polyaniline-coated rice husk-derived nano-silica@reduced graphene oxide (PANI-SiO₂@rGO) composites with excellent electrochemical performance. ATR-FTIR and XRD analyses confirm the formation of PANI-SiO₂@rGO, implying that SiO₂@rGO served as a template in the formation of composites. The morphology of PANI-SiO₂@rGO was characterized by SEM, HRTEM, and STEM, in which SiO₂ nanoparticles were homogeneously loaded on graphene sheets and the PANI fibrous network uniformly covers the SiO₂@rGO composites. The structure can withstand the large volume change as well as retain electronic conductivity during Li-ion insertion/extraction. Over 400 cycles, the assembled composite retains a high reversible specific capacity of 680 mA h g⁻¹ at a current density of 0.4 A g⁻¹, whereas the SiO₂@rGO retains only 414 mA h g⁻¹ at 0.4 A g⁻¹ after 215 cycles. The enhanced electrochemical performance of PANI-SiO₂@rGO was a result of the dual protection provided by the PANI flexible layer and graphene sheets. PANI-SiO₂@rGO composites may pave the way for the development of advanced anode materials for high-performance lithium-ion batteries.

By combining rice husk-derived nano-silica and reduced graphene oxide and then polymerizing PANI by in situ polymerization, we created polyaniline-coated rice husk-derived nano-silica@reduced graphene oxide composites with excellent electrochemical performance.     

N/O co-enriched graphene hydrogels as high-performance electrodes for aqueous symmetric supercapacitors

In this study, an easy one-pot hydrothermal strategy was used to prepare N/O co-enriched graphene hydrogels (NOGHs) using graphene oxide (GO) solution and n-propylamine as a reactant. The n-propylamine can be used not only as a reductant, nitrogen dopant and structure regulator, but also as a spacer to inhibit the agglomeration of graphene sheets. Benefiting from the synergistic effect between the heteroatoms (N, O), 3D porous structures and high specific surface area, the as-prepared NOGH samples present excellent electrochemical properties. Remarkably, the NOGH-140 based binder-free symmetric supercapacitor shows a high specific capacitance of 268.1 F g⁻¹ at the current density of 0.3 A g⁻¹ and retains 222.5 F g⁻¹ (82.9% of its initial value) at 10.0 A g⁻¹ in 6 M KOH electrolyte. Furthermore, the assembled device also displays a notable energy density (9.3 W h kg⁻¹) and outstanding cycling performance (1.8% increase of its initial specific capacitance after 10 000 cycles at 10 A g⁻¹). The simple preparation method and excellent electrochemical properties indicate that NOGHs can be used as electrode materials for commercial supercapacitors.

N/O co-enriched graphene hydrogel based supercapacitors were assembled. Owing to the synergistic effect between the heteroatoms (N, O), 3D porous structures and high specific surface area, they present excellent electrochemical properties.     

Template-assisted synthesis of NiCoO2 nanocages/reduced graphene oxide composites as high-performance electrodes for supercapacitors

Here we reported a coordinating etching and precipitating method to synthesize a complex binary metal oxides hollow cubic structure. A novel NiCoO₂/rGO composite with a structure of NiCoO₂ nanocages anchored on layers of reduced graphene oxide (rGO) were synthesized via a simple template-assisted method and the electrochemical performance was investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy tests as a faradaic electrode for supercapacitors at a graphene weight ratio of 1 wt% (1%). When used as electrode materials for electrochemical capacitors, the NiCoO₂/rGO composites achieved a specific capacity of 1375 F g⁻¹ at the current density of 1 A g⁻¹ and maintained 742 F g⁻¹ at 10 A g⁻¹. After 3000 cycles, the supercapacitor based on these nanocage structures shows long-term cycling performance with a high capacity of 778 F g⁻¹ at a current density of 1 A g⁻¹. These outstanding electrochemical performances are primarily attributed to the special morphological structure and the combination of mixed transition metal oxides and rGO, which not only maintains a high electrical conductivity for the overall electrode but also prevents the aggregation and volume expansion of electrochemical materials during the cycling processes.

Here we reported a coordinating etching and precipitating method to synthesize a complex binary metal oxides hollow cubic structure.     

Synthesis of 1,3-dicarbonyl-functionalized reduced graphene oxide/MnO2 composites and their electrochemical properties as supercapacitors

A novel 1,3-dicarbonyl-functionalized reduced graphene oxide (rDGO) was prepared by N-(4-aminophenyl)-3-oxobutanamide interacting with the epoxy and carboxyl groups of graphene oxide. The high-performance composite supercapacitor electrode material based on MnO₂ nanoparticles deposited onto the rDGO sheet (DGM) was fabricated by a hydrothermal method. The morphology and microstructure of the composites were characterized by field-emission scanning electron microscopy, transmission electron microscopy, Raman microscopy and X-ray photoelectron spectroscopy. The obtained results indicated that MnO₂ was successfully deposited on rDGO surfaces. The formed composite electrode materials exhibit excellent electrochemical properties. A specific capacitance of 267.4 F g⁻¹ was obtained at a current density of 0.5 A g⁻¹ in 1 mol L⁻¹ H₂SO₄, while maintaining high cycling stability with 97.7% of its initial capacitance after 1000 cycles at a current density of 3 A g⁻¹. These encouraging results are useful for potential energy storage device applications in high-performance supercapacitors.

A novel functionalized reduced graphene oxide and MnO₂ composite was prepared as a supercapacitor electrode material.     

Towards sustainable electrochemical energy storage: solution-based processing of polyquinone composites

Continuous adoption of renewable energy sources and the proliferation of electric transportation technologies push towards sustainable energy storage solutions. Consequently, a solution-based up-scalable synthesis approach is developed for polymeric quinone composites with graphene. Cellulose nanocrystals play a vital role in achieving greener processing and improving the composite electrochemical energy storage performance. The synthesis method emphasizes using aqueous reaction media, incorporates low-cost and biomass-derived feedstocks, avoids critical or scarce materials, and maintains temperatures below 200 °C. Stable aqueous graphene dispersions were obtained by hydrothermal reduction of electrochemically exfoliated graphene oxide in the presence of cellulose nanocrystals. Dispersions served as a reaction medium for quinone cationic polymerization, leading to core–shell type structures of polymer-covered mono-to-few layer graphene, thanks to the nanosheet restacking prevention effect provided by cellulose nanocrystal dispersions. A sample consisting of 5 wt% cellulose nanocrystals and 5 wt% graphene achieved storage metrics of 720.5 F g⁻¹ and 129.6 mA h g⁻¹ at 1 A g⁻¹, retaining over 70% of the performance after 1000 charge/discharge cycles.

A valid one-pot, low temperature and readily scalable aqueous processing route towards sustainable production of organic electrode-based battery/capacitive systems.     

Reduced graphene oxide promoted assembly of graphene@polyimide film as a flexible cathode for high-performance lithium-ion battery

Organic carbonyl polymers have been gradually used as the cathode in lithium-ion batteries (LIB). However, there are some limits in most organic polymers, such as low reversible capacity, poor rate performance, cycle instability, etc., due to low electrochemical conductivity. To mitigate the limits, we propose a strategy based on polyimide (PI)/graphene electroactive materials coated with reduced graphene oxide to prepare a flexible film (G@PI/RGO) by solvothermal and vacuum filtration processes. As a flexible cathode for LIB, it provides a reversible capacity of 198 mA h g⁻¹ at 30 mA g⁻¹ and excellent rate performance of 100 mA h g⁻¹ at high current densities of 6000 mA g⁻¹, and even a super long cycle performance (2500 cycles, 70% capacity retention). The excellent performance results in a special layer structure in which the electroactive PI was anchored and coated by the graphene. The present synthetic method can be further applied to construct other high-performance organic electrodes in energy storage.

G@PI/RGO is prepared by a combination of solvothermal reaction and carbonization. With good mechanical flexibility and high conductivity, it shows excellent performance when directly used as the cathode for LIB.     

In situ production of a two-dimensional molybdenum disulfide/graphene hybrid nanosheet anode for lithium-ion batteries

A solvent-free, low-cost, high-yield and scalable single-step ball milling process is developed to construct 2D MoS₂/graphene hybrid electrodes for lithium-ion batteries. Electron microscopy investigation reveals that the obtained hybrid electrodes consist of numerous nanosheets of MoS₂ and graphene which are randomly distributed. The MoS₂/graphene hybrid anodes exhibit excellent cycling stability with high reversible capacities (442 mA h g⁻¹ for MoS₂/graphene (40 h); 553 mA h g⁻¹ for MoS₂/graphene (20 h); 342 mA h g⁻¹ for MoS₂/graphene (10 h)) at a high current rate of 250 mA g⁻¹ after 100 cycles, whereas the pristine MoS₂ electrode shows huge capacity fading with a retention of 37 mA h g⁻¹ at 250 mA g⁻¹ current after 100 cycles. The incorporation of graphene into MoS₂ has an extraordinary effect on its electrochemical performance. This work emphasises the importance of the construction of the 2D MoS₂/graphene hybrid structure to prevent capacity fading issues with the MoS₂ anode in lithium-ion batteries.

A solvent-free, low-cost, high-yield and scalable single-step ball milling process is developed to construct 2D MoS₂/graphene hybrid electrodes for lithium-ion batteries.     

Agricultural waste-derived activated carbon/graphene composites for high performance lithium-ion capacitors

Agricultural waste, corncob-derived activated carbon (AC) is prepared by pre-carbonization of the precursors and activation of KOH of the pyrolysis products. The AC oxidized by HNO₃ is called OAC. The OAC/reduced graphene oxide (rGO) composites are prepared by urea reduction (aqueous mixture of OAC and graphene oxide). The influence of the mass ratio of graphene oxide (GO) on the electrochemical properties of OAC/rGO composites as electrode materials for electrochemical capacitors is studied. It is found that the rGO sheets were used as a wrinkled carrier to support the OAC particles. The pore size distribution and surface area are dependent on the GO mass ratio. In addition, the rate capability of OAC is improved by introducing GO. For the OAC/rGO composites prepared from precursors with a GO mass ratio of 5%, the best rate performance was achieved. The lithium ion capacitor, based on OAC/rGO as cathode and Si/C as anode, exhibits a high energy density of 141 W h kg⁻¹ at 1391 W kg⁻¹. 78.98% capacity retention is achieved after 1000 cycles at 0.4 A g⁻¹.

Agricultural waste, corncob-derived activated carbon (AC) is prepared by pre-carbonization of the precursors and activation of KOH of the pyrolysis products.     

Facile preparation of flexible binder-free graphene electrodes for high-performance supercapacitors

A facile two-step strategy to prepare flexible graphene electrodes has been developed for supercapacitors using thermal reduction of graphene oxide (GO) and thermally reduced graphene oxide (TRGO) composite films. The tunable porous structure of the GO/TRGO film provided channels to release the high pressure generated by CO₂ gas. The graphene electrode obtained from reduced-GO/TRGO (1 : 1 in mass ratio) film showed great flexibility and high film density (0.52 g cm⁻³). Using the EMI-BF₄ electrolyte with a working voltage of 3.7 V, the as-fabricated free-standing reduced-GO/TRGO (1 : 1) film achieved a great gravimetric capacitance of 180 F g⁻¹ (delivering a gravimetric energy density of 85.6 W h kg⁻¹), a volumetric capacitance of 94 F cm⁻³ (delivering a volumetric energy density of 44.7 W h L⁻¹), and a 92% retention after 10 000 charge/discharge cycles. In addition, the solid state flexible supercapacitor with the free-standing reduced-GO/TRGO (1 : 1) film as the electrodes and the EMI-BF₄/poly (vinylidene fluoride hexafluopropylene) (PVDF-HFP) gel as the electrolyte also demonstrated a high gravimetric capacitance of 146 F g⁻¹ with excellent mechanical flexibility, bending stability, and electrochemical stability. The strategy developed in this study provides great potentials for the synthesis of flexible graphene electrodes for supercapacitors.

A supercapacitor electrode is developed with a free-standing graphene film by a facile two-step strategy. The graphene electrode achieved a gravimetric capacitance of 180 F g⁻¹ and a volumetric capacitance of 94 F cm⁻³.     

Oxygen functional groups improve the energy storage performances of graphene electrochemical supercapacitors

Graphene is a promising electrode material for supercapacitors due to its superior physical and chemical properties, but the influence of its oxygen functional groups on capacitive performance still remains somewhat uncertain. In this work, graphene sheets with different oxygen content have been prepared through thermal reduction in argon. Furthermore, oxidation and pore-forming treatment of graphene annealed at 800 °C are also performed to explore the important effect of oxygen functional groups. The effects of disorder degree, surface area and oxygen functional groups on the specific capacitance were explored systematically. The content and species of oxygen functional groups are found to be significant factors influencing the electrochemical supercapacitor performance of graphene electrodes. The specific capacitances of graphene annealed at 200, 400 and 800 °C are 201, 153 and 34 F g⁻¹, respectively. However, the specific capacitance of graphene reduced at 800 °C can be increased to 137 F g⁻¹ after nitric acid oxidation treatment, and is only 39 F g⁻¹ after pore forming on graphene surface, demonstrating that the oxygen functional groups can improve the capacitive performances of graphene electrochemical supercapacitors.

The content and species of oxygen functional groups are significant factors influencing the electrochemical supercapacitor performance of graphene electrodes.     

In situ mass change and gas analysis of 3D manganese oxide/graphene aerogel for supercapacitors

Manganese oxide nanoparticles decorated on 3D reduced graphene oxide aerogels (3D MnO_x/rGO_ae) for neutral electrochemical capacitors were successfully produced by a rapid microwave reduction process within 20 s. The symmetric electrochemical capacitor of 3D MnO_x/rGO_ae (Mn 3.0 at%) storing charges via both electric double layer capacitance (EDLC) and pseudocapacitance mechanisms exhibits a specific capacitance of 240 F g⁻¹ as compared with 190 F g⁻¹ of that using the bare 3D rGO_ae at 0.5 A g⁻¹ in 1 M Na₂SO₄ (aq.) electrolyte. It retains 90% of the initial capacitance after 10 000 cycles, demonstrating high cycling stability. In addition, the charge storage mechanism of 3D MnO_x/rGO_ae was investigated using an electrochemical quartz crystal microbalance. In situ gas analysis using differential electrochemical mass spectrometry (DEMS) shows the CO₂ evolution at a cell potential over 1 V indicating that the positive electrode is possibly the voltage limiting electrode in the full cell. This finding may be useful for further development of practical high power and energy supercapacitors.

Manganese oxide nanoparticles decorated on 3D reduced graphene oxide aerogels (3D MnO_x/rGO_ae) for neutral electrochemical capacitors were successfully produced by a rapid microwave reduction process within 20 s.     

Electrochemical performance of graphene-coated activated mesocarbon microbeads as a supercapacitor electrode

Hybrid activated carbon/graphene materials are prospective candidates for use as high performance supercapacitor electrode materials, since they have the superior characteristics of high surface area, abundant micro/mesoporous structure due to the presence of activated carbon and good electrical conductivity as a result of the presence of graphene. In this work, the electrochemical performance of facile and low-cost graphene-coated activated mesocarbon microbeads (g-AM) is carefully studied. The results show that g-AM can only be formed at a very high temperature over a long activation time, resulting in the formation of a large pore size and low specific surface area, further resulting in poor electrochemical performance (110 F g⁻¹ at 0.1 A g⁻¹ in 6 M KOH solution). Ball milling for a short time is an effective way to improve the electrochemical performance (191 F g⁻¹ at 0.1 A g⁻¹ in 6 M KOH solution). Moreover, due to the strong resistance to aggregation and good electrical conductivity of graphene flowers, the g-AM had nearly 100% rate capability when increasing the current density from 5 to 50 A g⁻¹. The as-assembled two-electrode symmetric supercapacitor exhibits a high energy and power density (5.28 W h kg⁻¹ at 10 000 W kg⁻¹) in organic LiPF₆ electrolyte, due to its better electrical conductivity. It is expected that this type of hybrid structure holds great potential for scalable industrial manufacture as supercapacitor electrodes.

Activated carbon/graphene materials are prospective candidates as high performance supercapacitor electrodes, due to the presence of aggregation resisted graphene on the surface of activated carbon.     

Pentafluoropyridine functionalized novel heteroatom-doped with hierarchical porous 3D cross-linked graphene for supercapacitor applications

The fabrication with high energy density and superior electrical/electrochemical properties of hierarchical porous 3D cross-linked graphene-based supercapacitors is one of the most urgent challenges for developing high-power energy supplies. We facilely synthesized a simple, eco-friendly, cost-effective heteroatoms (nitrogen, phosphorus, and fluorine) co-doped graphene oxide (NPFG) reduced by hydrothermal functionalization and freeze-drying approach with high specific surface areas and hierarchical pore structures. The effect of different heteroatoms doping on the energy storage performance of the synthesized reduced graphene oxide is investigated extensively. The electrochemical analysis performed in a three-electrode system via cyclic voltammetry (CV), galvanostatic charging–discharging (GCD), and electrochemical impedance spectroscopy (EIS) demonstrates that the nitrogen, phosphorous, and fluorine co-doped graphene (NPFG-0.3) synthesized with the optimum amount of pentafluoropyridine and phytic acid (PA) exhibits a notably enhanced specific capacitance (319 F g⁻¹ at 0.5 A g⁻¹), good rate capability, short relaxation time constant (τ = 28.4 ms), and higher diffusion coefficient of electrolytic cations (Dk⁺ = 8.8261 × 10⁻⁹ cm² s⁻¹) in 6 M KOH aqueous electrolyte. The density functional theory (DFT) calculation result indicates that the N, F, and P atomic replacement within the rGO model could increase the energy value (G_T) from −673.79 eV to −643.26 eV, demonstrating how the atomic level energy could improve the electrochemical reactivity with the electrolyte. The improved performance of NPFG-0.3 over NFG, PG, and pure rGO is mainly ascribed to the fast-kinetic process owing to the well-balanced electron/ion transport phenomenon. A symmetric coin cell supercapacitor device fabricated using NPFG-0.3 as the anode and cathode material with 6 M KOH aqueous electrolyte exhibits maximum specific energy of 38 W h kg⁻¹, a maximum specific power of 716 W kg⁻¹, and ∼88.2% capacitance retention after 10 000 cycles. The facile synthesis approach and promising electrochemical results suggest this synthesized NPFG-0.3 material has high potential for future supercapacitor application.

Demonstration of the effect of Gibbs free energy (G_T = −643.26 eV) on N, P, F co-doped graphene, simulated via density functional theory (DFT).     

Hexadecyl trimethyl ammonium bromide assisted growth of NiCo2O4@reduced graphene oxide/ nickel foam nanoneedle arrays with enhanced performance for supercapacitor electrodes

NiCo₂O₄@reduced graphene oxide (rGO)/nickel foam (NF) composites were prepared via a hydrothermal method followed by annealing assisted by hexadecyl trimethyl ammonium bromide (CTAB). NiCo₂O₄@rGO/NF nanoneedle arrays grew directly on Ni foam (NF) without using a binder. The effect of graphene oxide (GO) concentration on the electrochemical properties of the composite was studied. When the GO concentration was 5 mg L⁻¹, the as-prepared NiCo₂O₄@rGO/NF reaches the highest specific capacitance of 1644 F g⁻¹ at a current density of 1 A g⁻¹. Even at 15 A g⁻¹, the specific capacitance is still 1167 F g⁻¹ and the capacitance retention rate is 89% after 10 000 cycles at 10 A g⁻¹. Furthermore, a NiCo₂O₄@rGO/NF//graphene hydrogel (GH) asymmetric supercapacitor cell (ASC) device was assembled and exhibits a high specific capacitance of 84.13 F g⁻¹ at 1 A g⁻¹ and excellent cycle stability (113% capacitance retention) after 10 000 charge/discharge cycles at 10 A g⁻¹. This provides potential for application in the field of supercapacitors due to the outstanding specific capacitance, rate performance and cycle stability of NiCo₂O₄@rGO/NF.

Anisotropic NiCo₂O₄ nanoneedle arrays grew directly on Ni foam in the presence of rGO via the hydrothermal method followed by annealing assisted by hexadecyl trimethyl ammonium bromide (CTAB).     

ZnSe nanoparticles dispersed in reduced graphene oxides with enhanced electrochemical properties in lithium/sodium ion batteries

A ZnSe-reduced graphene oxide (ZnSe-rGO) nanocomposite with ZnSe dispersed in rGO is prepared via a one-step hydrothermal method and applied as the anode materials for both lithium and sodium ion batteries (LIBs/SIBs). The as-prepared composite exhibits greatly enhanced reversible capacity, excellent cycling stability and rate capability (530 mA h g⁻¹ after 100 cycles at 500 mA g⁻¹ in LIBs, 259.5 mA h g⁻¹ after 50 cycles at the current density of 100 mA g⁻¹ in SIBs) compared with bare ZnSe in both lithium and sodium storage. The rGO plays an influential role in enhancing the conductivity of the nanocomposites, buffering the volume change and preventing the aggregation of ZnSe particles during the cycling process, thus securing the high structure stability and reversibility of the electrode.

ZnSe-rGO nanocomposite with ZnSe dispersed in reduced graphene oxides is studied as an anode for lithium and sodium ion batteries (LIBs/SIBs).     

Tin disulphide/nitrogen-doped reduced graphene oxide/polyaniline ternary nanocomposites with ultra-high capacitance properties for high rate performance supercapacitor

In this work, tin disulfide/nitrogen-doped reduced graphene oxide/polyaniline ternary composites are synthesized via in situ polymerization of aniline monomers on the surface of tin disulfide/nitrogen-doped reduced graphene oxide nanosheets binary composites with different loading of the conducting polymers. The tin disulfide/nitrogen-doped reduced graphene oxide/polyaniline ternary composites electrode shows much higher specific capacitance, specific energy and specific power values than those of pure polyaniline and tin disulfide/nitrogen-doped reduced graphene oxide binary composites. The highest specific capacitance, specific energy and specific power values of 1021.67 F g⁻¹, 69.53 W h kg⁻¹ and 575.46 W kg⁻¹ are observed for 60% polyaniline deposited onto tin disulfide/nitrogen-doped reduced graphene oxide composites at a current density of 1 A g⁻¹. The above composites also show superior cyclic stability and 78% of the specific capacitance can be maintained after 5000 galvanostatic charge–discharge cycles. The good charge-storage properties of tin disulfide/nitrogen-doped reduced graphene oxide/polyaniline ternary composites is ascribed to the organic–inorganic synergistic effect. This study paves the way to consider tin disulfide/nitrogen-doped reduced graphene oxide/polyaniline ternary composites as excellent electrode materials for energy storage applications.

In this work, SnS₂/NRGO/PANI ternary composites are synthesized via in situ polymerization of aniline monomers on the surface of SnS₂/NRGO nanosheets binary composites with different loading of the conducting polymers.     

FeNb2O6/reduced graphene oxide composites with intercalation pseudo-capacitance enabling ultrahigh energy density for lithium-ion capacitors

Lithium-ion capacitors (LICs), which combine the characteristics of lithium-ion batteries and supercapacitors, have been well studied recently. Extensive efforts are devoted to developing fast Li⁺ insertion/deintercalation anode materials to overcome the discrepancy in kinetics between battery-type anodes and capacitive cathodes. Herein, we design a FeNb₂O₆/reduced graphene oxide (FNO/rGO) hybrid material as a fast-charge anode that provides a solution to the aforementioned issue. The synergetic combination of FeNb₂O₆, whose unique structure promotes fast electron transport, and highly conductive graphene shortens the Li⁺ diffusion pathways and enhances structural stability, leading to excellent electrochemical performance of the FNO/rGO anode, including a high capacity (770 mA h g⁻¹ at 0.05 A g⁻¹) and long cycle stability (95.3% capacitance retention after 500 cycles). Furthermore, the FNO/rGO//ACs LIC achieves an ultrahigh energy density of 135.6 W h kg⁻¹ (at 2000 W kg⁻¹) with a wide working potential window from 0.01 to 4 V and remarkable cycling performance (88.5% capacity retention after 5000 cycles at 2 A g⁻¹).

FeNb₂O₆/reduced graphene oxide (FNO/rGO) hybrid material as a fast charge anode for LICs that provides a solution to overcome the discrepancy in kinetics between battery-type anodes and capacitive cathodes.     

Flexible solid-state supercapacitor based on tin oxide/reduced graphene oxide/bacterial nanocellulose

We demonstrate a flexible and light-weight supercapacitor based on bacterial nanocellulose (BNC) incorporated with tin oxide (SnO₂) nanoparticles, graphene oxide (GO) and poly(3,4-ethylenedioxyiophene)-poly(styrenesulfonate) (PEDOT:PSS). The SnO₂ and GO flakes are introduced into the fibrous nanocellulose matrix during bacteria-mediated synthesis. The flexible PEDOT:PSS/SnO₂/rGO/BNC electrodes exhibited excellent electrochemical performance with a capacitance of 445 F g⁻¹ at 2 A g⁻¹ and outstanding cycling stability with 84.1% capacitance retention over 2500 charge/discharge cycles. The flexible solid-state supercapacitors fabricated using PEDOT:PSS/SnO₂/rGO/BNC electrodes and poly(vinyl alcohol) (PVA)-H₂SO₄ coated BNC as a separator exhibited excellent energy storage performance. The fabrication method demonstrated here is highly scalable and opens up new opportunities for the fabrication of flexible cellulose-based energy storage devices.

A novel, simple and scalable method for the incorporation of tin oxide (SnO₂) and graphene oxide (GO) into bacterial nanocellulose during its growth for the fabrication of a flexible, scalable and environmental-friendly energy storage device was reported.