Unveiling TiNb2 O7 as an insertion anode for lithium ion capacitors with high energy and power density

This is the first report of the utilization of TiNb2 O7 as an insertion-type anode in a lithium-ion hybrid electrochemical capacitor (Li-HEC) along with an activated carbon (AC) counter electrode derived from a coconut shell. A simple and scalable electrospinning technique is adopted to prepare one-dimensional TiNb2 O7 nanofibers that can be characterized by XRD with Rietveld refinement, SEM, and TEM. The lithium insertion properties of such electrospun TiNb2 O7 are evaluated in the half-cell configuration (Li/TiNb2 O7 ) and it is found that the reversible intercalation of lithium (≈3.45 mol) is feasible with good capacity retention characteristics. The Li-HEC is constructed with an optimized mass loading based on the electrochemical performance of both the TiNb2 O7 anode and AC counter electrode in nonaqueous media. The Li-HEC delivers very high energy and power densities of approximately 43 Wh kg(-1) and 3 kW kg(-1) , respectively. Furthermore, the AC/TiNb2 O7 Li-HEC delivers a good cyclability of 3000 cycles with about 84% of the initial value.

Hydrogen silsequioxane-derived Si/SiO(x) nanospheres for high-capacity lithium storage materials

Si/SiOx composite materials have been explored for their commercial possibility as high-performance anode materials for lithium ion batteries, but suffer from the complexity of and limited synthetic routes for their preparation. In this study, Si/SiOx nanospheres were developed using a nontoxic and precious-metal-free preparation method based on hydrogen silsesquioxane obtained from sol-gel reaction of triethoxysilane. The resulting Si/SiOx nanospheres with a uniform carbon coating layer show excellent cycle performance and rate capability with high-dimensional stability. This approach based on a scalable sol-gel reaction enables not only the development of Si/SiOx with various nanostructured forms, but also reduced production cost for mass production of nanostructured Si/SiOx.

Highly conducting lyotropic liquid crystalline mesophases of pluronics (P65, P85, P103, and P123) and hydrated lithium salts (LiCl and LiNO₃)

Demand for ionically conducting materials, as membranes and electrodes, is one of the driving forces of current research in chemistry, physics, and engineering. The lithium ion is a key element of these materials, and its assembly into nanostructures and mesophases is important for the membrane and electrode technologies. In this investigation, we show that hydrated lithium salts (such as LiCl·xH2O and LiNO3·xH2O, x is as low as 1.5 and 3.0, respectively) and pluronics (triblock copolymer such as PX where X is 65, 85, 103, and 123) form lyotropic liquid crystalline mesophases (LLCM), denoted as LiY·xH2O-PX-n (Y is Cl(-) or NO3(-), and n is the salt/PX mole ratio). The structure of the mesophase is hexagonal over a broad salt concentration and transforms to a cubic mesophase and then to disordered gel phase with an increasing salt content of the mixtures. The mesophases are unstable at low salt contents and undergo a phase separation into pure pluronics and salt-rich LLCMs. The salt content of the ordered mesophase can be as high as 30 mole ratio for each pluronic, which is a record high for any known salted phases. The mesophases also display high ac ionic conductivities, reaching up to 21 mS/cm at room temperature (RT), and are sensitive to the water content. These mesophases can be useful as ion-conducting membranes and can be used as media for the synthesis of lithium-containing nanoporous materials.

Graphenal polymers for energy storage

A key to improve the electrochemical performance of energy storage systems (e.g., lithium ion batteries and supercapacitors) is to develop advanced electrode materials. In the last few years, although originating from the unique structure and property of graphene, interest has expanded beyond the originally literally defined graphene into versatile integration of numerous intermediate structures lying between graphene and organic polymer, particularly for the development of new electrode materials for energy storage devices. Notably, diverse designations have shaded common characteristics of the molecular configurations of these newly-emerging materials, severely impeding the design, synthesis, tailoring, functionalization, and control of functional electrode materials in a rational and systematical manner. This concept paper highlights all these intermediate materials, specifically comprising graphene subunits intrinsically interconnected by organic linkers or fractions, following a general concept of graphenal polymers. Combined with recent advances made by our group and others, two representative synthesis approaches (bottom-up and top-down) for graphenal polymers are outlined, as well as the structure-property relationships of these graphenal polymers as energy storage electrode materials are discussed.

Ultrathin spinel membrane-encapsulated layered lithium-rich cathode material for advanced Li-ion batteries

Lack of high-performance cathode materials has become a technological bottleneck for the commercial development of advanced Li-ion batteries. We have proposed a biomimetic design and versatile synthesis of ultrathin spinel membrane-encapsulated layered lithium-rich cathode, a modification by nanocoating. The ultrathin spinel membrane is attributed to the superior high reversible capacity (over 290 mAh g(-1)), outstanding rate capability, and excellent cycling ability of this cathode, and even the stubborn illnesses of the layered lithium-rich cathode, such as voltage decay and thermal instability, are found to be relieved as well. This cathode is feasible to construct high-energy and high-power Li-ion batteries.

Winding aligned carbon nanotube composite yarns into coaxial fiber full batteries with high performances

Inspired by the fantastic and fast-growing wearable electronics such as Google Glass and Apple iWatch, matchable lightweight and weaveable energy storage systems are urgently demanded while remaining as a bottleneck in the whole technology. Fiber-shaped energy storage devices that can be woven into electronic textiles may represent a general and effective strategy to overcome the above difficulty. Here a coaxial fiber lithium-ion battery has been achieved by sequentially winding aligned carbon nanotube composite yarn cathode and anode onto a cotton fiber. Novel yarn structures are designed to enable a high performance with a linear energy density of 0.75 mWh cm(-1). A wearable energy storage textile is also produced with an areal energy density of 4.5 mWh cm(-2).

Self-assembly of nano/micro-structured Fe3O4 microspheres among 3D rGO/CNTs hierarchical networks with superior lithium storage performances

Nano/micro-structured Fe3O4 microspheres among three-dimensional (3D) reduced graphene oxide (rGO)/carbon nanotubes (CNTs) hierarchical networks (the ternary composite is denoted as rGCFs) have been synthesized using a facile, self-assembled and one-pot hydrothermal approach. The rGCFs composite exhibits superior lithium storage performances: initial discharge and charge capacities of 1452 and 1036 mAh g(-1), respectively, remarkable rate capability at current densities from 100 mA g(-1) to 10 A g(-1) and outstanding cycling performance up to 200 cycles. The highly enhanced electrochemical performances of rGCFs depend heavily on the robust 3D rGO/CNTs hierarchical networks, the stable nano/microstructures of active Fe3O4 microspheres and the positive synergistic effects of building components. The systematic structure characterizations and electrochemical investigations provide insightful understanding towards the relationship between structure/morphology and lithium storage performances, which may pave the way for the rational design of composite materials with desirable goals.

Effect of carbon matrix dimensions on the electrochemical properties of Na3V2(PO4)3 nanograins for high-performance symmetric sodium-ion batteries

Na3V2(PO4)3 nanograins dispersed in different carbon matrices are rationally synthesized and systematically characterized. The acetylene carbon matrix provides the best conductive networks for electrons and sodium ions, which endows Na3V2(PO4)3 stable cyclability and high rate performance. The Na3V2 (PO4)3 -based symmetric sodium-ion batteries show outstanding electrochemical performance, which is promising for large-scale and low-cost energy storage applications.

Fe3O4/carbon hybrid nanoparticle electrodes for high-capacity electrochemical capacitors

Fe3O4/carbon hybrid nanoparticles (FeCHNPs) were fabricated using dual-nozzle electrospraying, vapor deposition polymerization (VDP), and carbonization. FeOOH nanoneedles decorated with polypyrrole (PPy) nanoparticles (FePNPs) were fabricated by electrospraying pristine PPy mixed with FeCl3 solution, followed by heating stirring reaction. A PPy coating was then formed on the FeOOH nanoneedles through a VDP process. FeCHNPs were produced through carbonization of PPy and FeOOH phase transitions. These hybrid carbon nanoparticles (NPs) were used to build electrodes of electrochemical capacitors. The specific capacitance of the FeCHNPs was 455 F g(-1), which is larger than that of pristine PPy NPs (105 F g(-1)) or other hybrid PPy NPs. Furthermore, the FeCHNP-based capacitors exhibited better cycle stability during charge-discharge cycling than other hybrid NP capacitors. This is because the carbon layer on the Fe3 O4 surface formed a protective coating, preventing damage to the electrode materials during the charge-discharge processes. This fabrication technique is an effective approach for forming stable carbon/metal oxide nanostructures for energy storage applications.

Mn-doped TiO2 nanosheet-based spheres as anode materials for lithium-ion batteries with high performance at elevated temperatures

Novel Mn(2+)-doped TiO2 nanosheet-based spheres have been successfully prepared via a simple hydrothermal and ion-exchange process. After hydrothermal growth, flowerlike nanosheet-based spheres of protonated dititanate were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The hierarchical nanostructure was obtained via a dissolution-recrystallization process starting from a precursor of homogenous TiO2 nanospheres. Moreover, as-prepared protonated dititanate was converted to Mn-doped nanosheet-based spheres via the ion-exchange method. Then, both the doped and undoped protonated dititanate were calcined and tested as anode materials for lithium-ion battery applications at elevated temperatures. The undoped sample showed an initial capacity of 201 mAh g(-1) but only had 44.1% of the initial capacity retained after 50 cycles at mixed current densities of 30, 150, and 500 mA g(-1) at 55 °C, while the Mn-doped one exhibited an initial capacity of 190 mAh g(-1) and 91.4% capacity retention with superior reversible capacity under the same test conditions. Comparisons between different samples suggest that manganese ions on the surface of TiO2 nanosheet-based spheres are responsible for the enhanced electrochemical performance.

Confined iron fluoride@CMK-3 nanocomposite as an ultrahigh rate capability cathode for Li-ion batteries

A facile and advanced architecture design of FeF3·0.33H2O impregnated CMK-3 nanocomposite (FeF3·0.33H2O@CMK-3) is presented. In the FeF3·0.33H2O@CMK-3 nanocomposite, mesoporous carbon CMK-3 can provide enough passageways for electron and Li(+) transport to the confined nanosized FeF3·0.33H2O. The intimate conductive contact between the FeF3·0.33H2O nanoparticles and the carbon framework not only provides an expressway of electron transfer for Li(+) insertion/extraction but also suppresses the growth and agglomeration of FeF3·0.33H2O during the crystallization process. As expected, the nanostructured materials exhibit impressive rate capability and excellent cyclicity. Remarkably, even under an ultrahigh charge/discharge rate of 50 C (the charge or discharge process takes a mere 72 s), the confined FeF3·0.33H2O@CMK-3 still shows a high specific capacity of 78 mAh g(-1). By combining confined nanosized active material, high electron conductivity, and open framework, the FeF3·0.33H2O@CMK-3 nanocomposite demonstrates excellent high-rate capability and good cycling properties.

Electrospun Na3V2(PO4)3/C nanofibers as stable cathode materials for sodium-ion batteries

Sodium-ion batteries are considered as prime alternatives to lithium-ion batteries for large-scale renewable energy storage units due to their low cost and the abundance of sodium bearing precursors in the earth's mineral deposits. In the current work, a 3D NASICON framework Na3V2(PO4)3/carbon cathode electrode with 20-30 nm Na3V2(PO4)3 nanoparticles uniformly encapsulated interconnecting one-dimensional carbon nanofibers was fabricated using a simple and scalable electrospinning method. The Na3V2(PO4)3/C cathode showed an initial charge capacity of 103 mA h g(-1) and a discharge capacity of 101 mA h g(-1) (calculated on the total mass of Na3V2(PO4)3 and carbon) at 0.1C rate, and retained stable discharge capacities of 77, 58, 39 and 20 mA h g(-1) at high current densities of 2C, 5C, 10C and 20C, respectively. Moreover, because of the efficient 1D sodium-ion transport pathway and the highly conductive network of Na3V2(PO4)3/C, the electrode exhibited high overall capacities even when cycled at high currents, extending its usability to high power applications.

Self-supported Li4Ti5O12-C nanotube arrays as high-rate and long-life anode materials for flexible Li-ion batteries

Self-supported Li4Ti5O12-C nanotube arrays with high conductivity architectures are designed and fabricated for application in Li-ion batteries. The Li4Ti5O12 nanotube arrays grow directly on stainless steel foil by a facile template-based solution route, further enhancing electronic conductivity by uniform carbon-coating on the inner and outer surfaces of Li4Ti5O12 nanotubes. Owing to the shortened Li(+) diffusion distance, high contact surface area, sufficient conductivity, and very good structure stability of the nanotube arrays, the self-supported Li4Ti5O12-C nanotube arrays exhibit remarkable rate capability (a reversible capability of 135 mA h g(-1), 105 mA h g(-1), and 80 mA h g(-1) at 30C, 60C, and 100C, respectively) and cycling performance (approximate 7% capacity loss after 500 cycles at 10C with a capacity retention of 144 mA h g(-1)).

Mitigating voltage fade in cathode materials by improving the atomic level uniformity of elemental distribution

Lithium- and manganese-rich (LMR) layered-structure materials are very promising cathodes for high energy density lithium-ion batteries. However, their voltage fading mechanism and its relationships with fundamental structural changes are far from being well understood. Here we report for the first time the mitigation of voltage and energy fade of LMR cathodes by improving the atomic level spatial uniformity of the chemical species. The results reveal that LMR cathodes (Li[Li0.2Ni0.2M0.6]O2) prepared by coprecipitation and sol-gel methods, which are dominated by a LiMO2 type R3̅m structure, show significant nonuniform Ni distribution at particle surfaces. In contrast, the LMR cathode prepared by a hydrothermal assisted method is dominated by a Li2MO3 type C2/m structure with minimal Ni-rich surfaces. The samples with uniform atomic level spatial distribution demonstrate much better capacity retention and much smaller voltage fade as compared to those with significant nonuniform Ni distribution. The fundamental findings on the direct correlation between the atomic level spatial distribution of the chemical species and the functional stability of the materials may also guide the design of other energy storage materials with enhanced stabilities.

Controlling SEI formation on SnSb-porous carbon nanofibers for improved Na ion storage

Porous carbon nanofiber (CNF)-supported tin-antimony (SnSb) alloys are synthesized and applied as a sodium-ion battery anode. The chemistry and morphology of the solid electrolyte interphase (SEI) film and its correlation with the electrode performance are studied. The addition of fluoroethylene carbonate (FEC) in the electrolyte significantly reduces electrolyte decomposition and creates a very thin and uniform SEI layer on the cycled electrode surface, which an promote the kinetics of Na-ion migration/transportation, leading to excellent electrochemical performance.

Construction of high-energy-density supercapacitors from pine-cone-derived high-surface-area carbons

Very high surface area activated carbons (AC) are synthesized from pine cone petals by a chemical activation process and subsequently evaluated as an electrode material for supercapacitor applications in a nonaqueous medium. The maximum specific surface area of ∼3950 m(2)  g(-1) is noted for the material treated with a 1:5 ratio of KOH to pine cone petals (PCC5), which is much higher than that reported for carbonaceous materials derived from various other biomass precursors. A symmetric supercapacitor is fabricated with PCC5 electrodes, and the results showed enhanced supercapacitive behavior with the highest energy density of ∼61 Wh kg(-1). Furthermore, outstanding cycling ability is evidenced for such a configuration, and ∼90 % of the initial specific capacitance after 20,000 cycles under harsh conditions was observed. This result revealed that the pine-cone-derived high-surface-area AC can be used effectively as a promising electrode material to construct high-energy-density supercapacitors.

Stable, high voltage Li0.85Ni0.46Cu0.1Mn1.49O4 spinel cathode in a lithium-ion battery using a conversion-type CuO anode

We report in this work a copper-doped Li0.85Ni0.46Cu0.1Mn1.49O4 spinel-structured compound prepared by an easy, two-steps coprecipitation and solid state process and used in a lithium-ion battery in combination with a CuO-based anode. We show that the spinel-type cathode adopts unique morphology, characterized by well-developed, crystalline and aggregated microparticles, that considerably reduces the occurrence of side reactions. This cathode material can operate in a lithium cell at voltages as high as 5.3 V without sign of electrolyte decomposition, delivering a capacity of about 100 mA h g(-1) with high retention and high Coulombic efficiency over prolonged cycling. The combination of the Li0.85Ni0.46Cu0.1Mn1.49O4 cathode with a conversion-type, CuO-MCMB anode results in a new type of lithium ion battery characterized by a voltage value of 3.4 V, a stable capacity of 100 mA h g(-1) and a high Coulombic efficiency (exceeding 95%). Expected low cost, safety, and environmental compatibility are additional advantages of the lithium-ion cell reported here.

Magnesium(II) bis(trifluoromethane sulfonyl) imide-based electrolytes with wide electrochemical windows for rechargeable magnesium batteries

We present a promising electrolyte candidate, Mg(TFSI)2 dissolved in glyme/diglyme, for future design of advanced magnesium (Mg) batteries. This electrolyte shows high anodic stability on an aluminum current collector and allows Mg stripping at the Mg electrode and Mg deposition on the stainless steel or the copper electrode. It is clearly shown that nondendritic and agglomerated Mg secondary particles composed of ca. 50 nm primary particles alleviating safety concern are formed in glyme/diglyme with 0.3 M Mg(TFSI)2 at a high rate of 1C. Moreover, a Mg(TFSI)2-based electrolyte presents the compatibility toward a Chevrel phase Mo6S8, a radical polymer charged up to a high voltage of 3.4 V versus Mg/Mg(2+) and a carbon-sulfur composite as cathodes.

In situ three-dimensional synchrotron X-Ray nanotomography of the (de)lithiation processes in tin anodes

The three-dimensional quantitative analysis and nanometer-scale visualization of the microstructural evolutions of a tin electrode in a lithium-ion battery during cycling is described. Newly developed synchrotron X-ray nanotomography provided an invaluable tool. Severe microstructural changes occur during the first delithiation and the subsequent second lithiation, after which the particles reach a structural equilibrium with no further significant morphological changes. This reveals that initial delithiation and subsequent lithiation play a dominant role in the structural instability that yields mechanical degradation. This in situ 3D quantitative analysis and visualization of the microstructural evolution on the nanometer scale by synchrotron X-ray nanotomography should contribute to our understanding of energy materials and improve their synthetic processing.

Contribution to the understanding of capacity fading in graphene nanosheets acting as an anode in full Li-ion batteries

Graphene nanosheets (GNS) were used as anodes in full Li-ion cells and LiFePO4 (LFPO) was used as the cathode. A rapid decrease in capacity was observed following the first cycle, the origin of which was assigned to Li consumption in the solid-electrolyte interface (SEI) formation. A reduction of the irreversible capacity from 120 to a value as low as 20 mAh g(-1), similar to a commercial graphite anode, was possible through a prelithiation treatment prior to cell assembling. However, the GNS electrode barely delivered a capacity ca. 40 mAh g(-1) at the end of cycle 50, notably lower than that of the graphite electrode (ca. 100 mAh g(-1)). X-ray photoelectron spectroscopy spectra of the pristine electrodes at the end of 6th and 22nd charges, combined with depth profile analysis, supplied valuable information on the thickness and composition of the SEI. The spectra revealed that the SEI formed on the graphite electrode was much thicker than that formed on the GNS electrode and that its composition was controlled mainly by Li2CO3. The strength and the stability of Li2CO3 are two requisites for establishing a good SEI, which is the reason why the cell made from graphite performed better.

Li(+)-conductive polymer-embedded nano-Si particles as anode material for advanced Li-ion batteries

Si has been considered as a promising alternative anode for next-generation lithium ion batteries (LIBs), but the commercial application of Si anodes is still limited due to their poor cyclability. In this paper, we propose a new strategy to enhance the long-term cyclability of Si anode by embedding nano-Si particles into a Li(+)-conductive polymer to form a Si/polymer composite with core-shell structure, in which nano-Si cores act as active Li-storage phase and the polymeric matrix serves not only as a strong buffer to accommodate the volume change, but also as a protection barrier to prevent the direct contact of Si surface with electrolyte, so as to maintain the mechanical integrity of Si anode and suppress the repeated destruction and construction of solid electrolyte interphase (SEI) on the Si surface. To realize this strategy, we synthesize a Si/PPP (polyparaphenylene) composite simply by ball-milling the Si nanoparticles with PPP polymer that has n-doping activity. Our experimental results demonstrate that the thus-prepared Si/PPP composite exhibits a high capacity of 3184 mA h g(-1) with an initial coulombic efficiency of 78%, an excellent rate capability with a considerably high capacity of 1670 mA h g(-1) even at a very high rate of 16 A g(-1), and a long-term cyclability with 60% capacity retention over 400 cycles, showing a great prospect for battery application. In addition, this structural design could be adopted to other Li-storable metals or alloys for developing cycle-stable anode materials for Li-ion batteries.

Hybrid supercapacitor-battery materials for fast electrochemical charge storage

High energy and high power electrochemical energy storage devices rely on different fundamental working principles--bulk vs. surface ion diffusion and electron conduction. Meeting both characteristics within a single or a pair of materials has been under intense investigations yet, severely hindered by intrinsic materials limitations. Here, we provide a solution to this issue and present an approach to design high energy and high power battery electrodes by hybridizing a nitroxide-polymer redox supercapacitor (PTMA) with a Li-ion battery material (LiFePO4). The PTMA constituent dominates the hybrid battery charge process and postpones the LiFePO4 voltage rise by virtue of its ultra-fast electrochemical response and higher working potential. We detail on a unique sequential charging mechanism in the hybrid electrode: PTMA undergoes oxidation to form high-potential redox species, which subsequently relax and charge the LiFePO4 by an internal charge transfer process. A rate capability equivalent to full battery recharge in less than 5 minutes is demonstrated. As a result of hybrid's components synergy, enhanced power and energy density as well as superior cycling stability are obtained, otherwise difficult to achieve from separate constituents.

3D amorphous silicon on nanopillar copper electrodes as anodes for high-rate lithium-ion batteries

We present an amorphous Si anode deposited on a Cu nanopillar current collector, fabricated using a thermal roll-to-roll process followed by electroformation and LPCVD, for application in high-rate Li-ion batteries. Cu nanopillar current collectors with diameters of 250 and 500 nm were patterned periodically with 1 μm pitch and 2 μm height to optimize the diameters of the pillars for better electrochemical performance. Void spaces between Cu nanopillars allowed not only greater effective control of the strain caused by the Si expansion during lithiation than that allowed by a nonpatterned electrode but also significantly improved cycle performance even at 20 C measured after the same rate test: After 100 cycles at 0.5 C, the patterned electrodes with 250 and 500 nm diameter nanopillars showed high capacity retentions of 86% and 84%, respectively. These electrodes retained discharge capacities of 1057 and 780 mAh/g even at 20 C, respectively.

High performance LiMn2O4 cathode materials grown with epitaxial layered nanostructure for Li-ion batteries

Tremendous research works have been done to develop better cathode materials for a large scale battery to be used for electric vehicles (EVs). Spinel LiMn2O4 has been considered as the most promising cathode among the many candidates due to its advantages of high thermal stability, low cost, abundance, and environmental affinity. However, it still suffers from the surface dissolution of manganese in the electrolyte at elevated temperature, especially above 60 °C, which leads to a severe capacity fading. To overcome this barrier, we here report an imaginative material design; a novel heterostructure LiMn2O4 with epitaxially grown layered (R3̅m) surface phase. No defect was observed at the interface between the host spinel and layered surface phase, which provides an efficient path for the ionic and electronic mobility. In addition, the layered surface phase protects the host spinel from being directly exposed to the highly active electrolyte at 60 °C. The unique characteristics of the heterostructure LiMn2O4 phase exhibited a discharge capacity of 123 mAh g(-1) and retained 85% of its initial capacity at the elevated temperature (60 °C) after 100 cycles.

Multilayered Si nanoparticle/reduced graphene oxide hybrid as a high-performance lithium-ion battery anode

Multilayered Si/RGO anode nanostructures, featuring alternating Si nanoparticle (NP) and RGO layers, good mechanical stability, and high electrical conductivity, allow Si NPs to easily expand between RGO layers, thereby leading to high reversible capacity up to 2300 mAh g(-1) at 0.05 C (120 mA g(-1) ) and 87% capacity retention (up to 630 mAh g(-1) ) at 10 C after 152 cycles.

Electrostatic induced stretch growth of homogeneous β-Ni(OH)2 on graphene with enhanced high-rate cycling for supercapacitors

Supercapacitors, as one of alternative energy devices, have been characterized by the rapid rate of charging and discharging, and high power density. But they are now challenged to achieve their potential energy density that is related to specific capacitance. Thus it is extremely important to make such materials with high specific capacitances. In this report, we have gained homogenous Ni(OH)2 on graphene by efficiently using of a facile and effective electrostatic induced stretch growth method. The electrostatic interaction triggers advantageous change in morphology and the ordered stacking of Ni(OH)2 nanosheets on graphene also enhances the crystallization of Ni(OH)2. When the as-prepared Ni(OH)2/graphene composite is applied to supercapacitors, they show superior electrochemical properties including high specific capacitance (1503 F g(-1) at 2 mV s(-1)) and excellent cycling stability up to 6000 cycles even at a high scan rate of 50 mV s(-1).