Battery-type Electrode Material Research Articles

Battery-type Ni-Co-Se hollow microspheres cathode materials enabled by bifunctional N-doped carbon quantum dots with ultrafast electrochemical kinetics for hybrid supercapacitors

Hybrid supercapacitors (HSCs) with large energy and power density have received increasing concern for their great potential in satisfying the requirements of energy storage systems. Nonetheless, the imbalanced kinetics between the sluggish battery-type cathode and the rapid capacitor-type anode make it difficult for HSCs to achieve high energy density at high power density. Herein, a novel N-doped carbon quantum dots/Ni-Co-Se (N-CQDs/Ni-Co-Se) hollow microspheres composite is synthesized via a facile hydrothermal approach using bifunctional CQDs as size regulators and conductive agents for the first time. Thanks to the synergism of highly conductive N-CQDs with rapid electron transfer and reduced-size hollow micro-/nanostructures contributing to the enhanced ion transport, the as-prepared battery-type N-CQDs/Ni-Co-Se hollow microspheres composite cathode exhibits admirable rate property. In-depth electrochemical kinetic analyses and density functional theory (DFT) calculations are utilized to elucidate the preeminent kinetic properties. Furthermore, a novel HSC is fabricated based on the N-CQDs/Ni-Co-Se hollow microspheres composite cathode with ultrafast electrochemical kinetics, displaying a high energy density of 23.1 Wh kg−1 at a superb power density of 38.3 kW kg−1. This encouraging work provides a good strategy to construct ultrahigh rate battery-type electrode materials with tunable size and component for simultaneously obtaining high energy/power density HSCs.

Facile and Controllable Synthesis of CuS@Ni-Co Layered Double Hydroxide Nanocages for Hybrid Supercapacitors.

The synthesis of battery-type electrode materials with hollow nanostructures for high-performance hybrid supercapacitors (HSCs) remains challenging. In this study, hollow CuS@Ni-Co layered double hydroxide (CuS-LDH) composites with distinguished compositions and structures are successfully synthesized by co-precipitation and the subsequent etching/ion-exchange reaction. CuS-LDH-10 with uniformly dispersed CuS prepared with the addition of 10 mg of CuS shows a unique hollow polyhedral structure constituted by loose nanosphere units, and these nanospheres are composed of interlaced fine nanosheets. The composite prepared with 30 mg of CuS addition (CuS-LDH-30) is composed of a hollow cubic morphology with vertically aligned nanosheets on the CuS shell. The CuS-LDH-10 and CuS-LDH-30 electrodes exhibit high specific capacity (765.1 and 659.6 C g–1 at 1 A g–1, respectively) and superior cycling performance. Additionally, the fabricated HSC delivers a prominent energy density of 52.7 Wh kg–1 at 804.5 W kg–1 and superior cycling performance of 87.9% capacity retention after 5000 cycles. Such work offers a practical and effortless route for synthesizing unique metal sulfide/hydroxide composite electrode materials with hollow structures for high-performance HSCs.

Revealing bulk reaction kinetics of battery-like electrode for pseudocapacitor with ultra-high rate performance

Battery-like electrode materials have a high theoretical capacity but suffer from low electrical conductivity and poor structural stability, which are expected to be solved by revealing bulk reaction kinetics of crystal structure to improve the electrochemical performance. Herein, we grow NiCo-LDH single-crystal nanowires along the [003] crystal plane on the surface of amorphous SiO2 hollow spheres. This heterostructured architecture provides a synergistic effect among different components and enlarges the interlayer spacing of the grown NiCo-LDH single-crystal, offering more reactive sites and improving electrical conductivity. The prepared NiCo-LDH@SiO2/C electrode demonstrates ultra-high rate capability with 78.1 % capacitance retention even after a 40-fold increase in the current density. The asymmetric supercapacitors with NiCo-LDH@SiO2/C cathode and active carbon anode could deliver a maximum energy density of 47.6 Wh/g at 1383 W/kg. This work presents a new method to guide the design of NiCo-LDH electrode materials and opens up a new opportunity to develop high-performance battery-type electrode materials for pseudocapacitors.

Electrochemical-induced surface reconstruction to NiFe-LDHs-based heterostructure as novel positive electrode for supercapacitors with enhanced performance in neutral electrolyte

Layered double hydroxides (LDHs) are promising battery-type electrode materials for hybrid supercapacitors. However, their poor capacity in neutral electrolyte is the primary limitation for the practical application. Herein, we fabricated a kind of novel NiFe-LDHs-based heterostructure as high-performance electrode materials in neutral electrolyte via a high-voltage electrochemical cycling activation (ECA) strategy. During the high-voltage ECA process, NiFe-LDHs surface was in-situ reconstructed into low-crystalline NiOOH phase, and finally evolved to the unique NiFe-LDHs/NiOOH heterostructures. This surface reconstruction process can generate abundant heterogeneous interface so as to increase the active sites for the reversible adsorption and intercalation of cationic ions, accounting for the significantly improved electrochemical performance in neutral electrolyte. When used as the battery-type electrode material in neutral electrolyte (2 M LiNO3 solution), the obtained ECA (1.2 V-50) electrode exhibits an excellent specific capacity (107 mAh g−1 at a current density of 1 A g−1), which is increased by 50 times compared to the Initial-NiFe-LDHs (2.1 mAh g−1 at a current density of 1 A g−1). By coupling with a MoS2/rGO electrode, the assembled ECA (1.2 V-50)//MoS2/rGO hybrid supercapacitor device depicts a high energy density of 48.1 Wh kg−1 at a power density of 432.9 W kg−1 in neutral electrolyte, which is superior to most of the reported hybrid supercapacitors.

The Increasing Number of Electron Reservoirs in Nonporous, High-Conducting Coordination Polymers Cux BHT (x=3, 4, and 5, BHT=Benzenehexathiol) for Improved Faradaic Capacitance.

Although asymmetric supercapacitors (ASCs) can achieve high energy density, the lifespan and power density are severely suppressed due to the low conductivity of using pseudocapacitive or battery-type electrode materials. Recently, nonporous conductive coordination polymers (c-CPs) have sparked interests in supercapacitors. However, their performance is expected to be limited by the nonporous features, low specific surface area and absence of ion-diffusion channels. Here, it is demonstrated that the capacity of nonporous CPs will be significantly enhanced by maximizing the number of faradaic redox sites in their structures through a comparative investigation on three highly conductive nonporous c-CPs, Cux BHT(x=3, 4, 5.5). They show excellent capacitance of 312.1Fg-1 (374.5Cg-1 ) (Cu3 BHT), 186.7Fg-1 (224.0Cg-1 ) (Cu4 BHT) and 89.2Fg-1 (107.0Cg-1 ) (Cu5.5 BHT) at 0.5Ag-1 in a sequence related to the number of electron storage units in structures and outstanding rate performance and cycle stability. Furthermore, the constructed Cu3 BHT//MnO2 ASC device exhibits capacity retention of 92% (after 1500 cycles at 3Ag-1 ) and delivers a high energy density of 39.1Whkg-1 at power density of 549.6Wkg-1 within a large working potential window of 0-2.2V.

Growth of uniform CuCo2O4 porous nanosheets and nanowires for high-performance hybrid supercapacitors

In this work, uniform CuCo2O4 nanowires (CCO-NWs) and nanosheets (CCO-NSs) were directly grown on the stainless-steel foil via a hydrothermal process with a post calcination treatment in air, and powdered CuCo2O4 materials were obtained once they were peeled off from the stainless-steel substrate. These NWs- and NSs-based powders possessed a huge specific surface area and mesoporous feature. After electrochemical tests, it was found that the CCO-NWs delivered a capacity of 299.12 C g−1 and CCO-NSs could exhibit a capacity of up to 332.18 C g−1. A hybrid supercapacitor (HSC) was assembled with activated carbon (AC) as anode to evaluate the practical applications of CuCo2O4 in energy storage. The CCO-NWs//AC HSC exhibited an energy density of 36.16 W h kg−1 at 1.01 kW kg−1, and as for the CCO-NSs//AC HSC, it delivered 38.46 W h kg−1 at the power density of 1.03 kW kg−1. Both HSCs showed excellent cycling performance over 5000 cycles at 6 A g−1. The superior electrochemical performance of CuCo2O4 NWs and NSs indicates that the battery-type CuCo2O4 electrode materials can serve as advanced cathode for high-performance supercapacitors, and the simple synthetic method can be extended to the preparation of other transition metal oxides (TMOs)-based electrode materials with uniform structure and impressive electrochemical properties.

Free-standing 3D core-shell architecture of Ni3S2@NiCoP as an efficient cathode material for hybrid supercapacitors

The design and discovery of free-standing hybrid electrode materials with large absolute capacity and high cycling stability for energy storage become desirable and are still challenging. In this work, we demonstrate that the hybrid supercapacitor (HSC) device is assembled by 3D core–shell hierarchical nanorod arrays of Ni3S2@NiCoP nanocomposite for the first time. The Ni3S2@NiCoP nanocomposite is successfully synthesized through a facile stratagem containing hydrothermal process and the subsequent electrodeposition method. The 3D architecture of Ni3S2@NiCoP hybrid electrode composed of vertically aligned “hyperchannel” 1D Ni3S2 nanorods and highly conductive interconnected 2D nanosheets of NiCoP is beneficial to fast electron transfer kinetics, thus leading to enhancing the ionic and electronic conductivity, kinetics of redox reaction, and synergistic behavior of active species. The fabricated HSC device with Ni3S2@NiCoP electrode delivers outstanding areal capacity of 109 µAh cm−2 at a current density of 1 mA cm−2, brilliant energy density of 74.9 Wh kg−1 at a power density of 700 W kg−1, and prominent cyclic performance of 92% capacity retention even after 144-h floating test. This work demonstrates that the core–shell hierarchical nanorod arrays of Ni3S2@NiCoP can be viewed as one of the novel battery-type electrode materials for high-performance HSCs.

Oxygen-enriched hierarchical porous carbon supported Co-Ni nanoparticles for promising hybrid supercapacitors via one step pyrolysis of polymerized high internal phase emulsion

The urgent demand for high-performance energy storage components has been driving the exploration for superior battery-type electrode materials for hybrid supercapacitors, which is challenging but of considerable significance. In this paper, a one-step pyrolysis route was elaborated to prepare oxygen-enriched hierarchical porous carbon supported Co-Ni nanoparticles Co-Ni/OHPCs) by facile self-crosslinking assisted high internal phase emulsion (HIPE) templating. The oxygen-enriched porous carbon framework provides large specific surface area and structural stability, meanwhile Co doping can significantly reinforce the electrochemical performance of the Co-Ni/OHPCs battery-type electrodes. By optimizing the ratio of Ni2+ to Co2+ ions, the obtained Co-Ni/OHPC electrodes exhibited excellent electrochemical performance of 817.3 F g−1 at a scan rate of 5 mV s−1. Furthermore, coupling with an activated porous carbon anode, the assembled hybrid supercapacitor (HSC) possessed an appreciable energy density of 66.94 Wh kg−1 at 409.9 W kg−1 and a capacitance retention ratio of 73.89% after 5000 cycles, showing considerable application prospects. This structural design strategy provides new inspiration for the reasonable optimization of new electrode materials for promising hybrid supercapacitors.

Metal-N/P coordination assisted construction of robust heterointerface for stable and superior-rate electrodes in battery-type supercapacitors

Holding ultralong cycle life and superior rate capability with high specific capacity is an inevitable requirement for the practical applications of transition metal compounds battery-type supercapacitor electrode materials. In this paper, a novel class of transition metal phosphide (TMP) nanostructures evenly bonded on N/P co-doped graphene nanotubes (N/P-GNTs@b-TMP) is firstly built via one-step in-situ growth procedure. The N, P elements as substitutions of C in GNTs skeleton introduce rich electronic centers, further change the surface electronic structures of the skeleton, inducing the TMPs to anchor the surface of N/P-GNTs through metal-N and metal-P bonds, which is demonstrated by the characterizations and Density functional theory (DFT) calculation. The unique chemical bonding can not only reinforce the integration of the hybrid electrode materials during durable cycling, but also generate the typical internal electric field and greatly reduce the free energy of the reaction system, endowing a superior rate capacity and easy redox process relating to high specific capacity. Moreover, ex-situ impedance and capacitive/diffusion control analysis suggest the fast ions diffusion behavior and reaction kinetics. Benefiting from the unique architecture, the achieved N/P-GNTs@b-NiCoP positive electrode possesses high specific capacity of 250 mAh g−1 (1800 F g−1) at 2 A g−1 and 166 mAh g−1 (1200 F g−1) at 50 A g−1. Meanwhile, the N/P-GNTs@b-Fe2NiP and N/P-GNTs@b-FeCoP negative electrodes constructed by the same approach can also own a high specific capacity of 151.9, 159.7 mAh g−1 (547, 575 F g−1) at 1A g−1 and 63.6, 73.6 mAh g−1 (229, 265 F g−1) at 50 A g−1, respectively. More significantly, they all can present ∼90% capacity retention after 75000 cycles, which can be comparable to all of the reported transition metal compound electrodes even commercial carbonaceous materials. In addition, an asymmetric supercapacitor (ASC) using the achieved N/P-GNTs@b-NiCoP as electrode expresses a remarkable energy density of 77.8 Wh kg−1 and cycling stability. This work provides an innovative structural design strategy for obtaining battery-type supercapacitor electrode materials with commercial application prospects.

Influence of heat-treatment temperature on the improvement of the electrochemical performance of CoMoO4 nanomaterials for hybrid supercapacitor application

The rational design and construction of nanostructured materials have a great impact on the development of high-performance advanced electrode materials, which has attracted extensive attention to improve reliable and efficient energy storage devices. Herein, we report vertically aligned CoMoO4 nanoflakes with interconnected network-like porous structures as Faradic battery-type electrode materials for the advancement of supercapacitors (SCs). The nanoarchitecture CoMoO4 electrode materials were effectively fabricated through simple hydrothermal method and subsequent heat-treatment under different temperatures. Further, the effect of heat-treatment on the electrodes materials’ structural, morphological, and electrochemical properties were investigated by utilizing various characterization techniques. The unique nanoarchitecture of the 400 °C heat-treated CoMoO4 (CMO1) endows a facile pathway for the fast diffusion of the electrolyte ions and mass transfer reaction. Interestingly, the CMO1 (400 °C) electrode exhibits the specific capacity of 499 C g−1, which is higher than those of the CMO2 (500 °C) of 385 C g−1 and CMO3 (600 °C) of 260 C g−1, respectively. Furthermore, the hybrid supercapacitor (HSC) tailored with CMO1 as a positrode and activated carbon as a negatrode delivers a high specific capacitance of 102 F g−1 with excellent energy and power densities of 31.61 W h kg−1 and 19.29 kW kg−1, respectively.

Electrospun NiO/C nanofibers as electrode materials for hybrid supercapacitors with superior electrochemical performance

In this work, the porous NiO/C nanofibers (NFs) were rationally designed and prepared by a convenient electrospinning method, and followed with a calcination conversion of the precursor in air. The NiO/C composite exhibited a net-like structure that was composed of many intertwined NFs with an average diameter of about 200 nm. The electrochemical measurements demonstrated that the porous NiO/C NFs exhibited an electrochemical feature of battery-type electrode material, and delivered a specific capacity as high as 461.26 C g−1 under 1 A g−1 and an excellent rate capability with 82.7% capacity retention at 10 A g−1. A hybrid supercapacitor (NiO/C NFs//AC HSC) was assembled with NiO/C NFs as positive electrode and activated carbon (AC) as negative electrode, which delivered an energy density of 31.82 W h kg−1 under a power density of 816.36 W kg−1 along with an outstanding cyclic stability of 90.9% capacity retention over 5000 cycles at 5 A g−1. This simple synthetic method can be extended to the fabrication of other transition metal oxides (TMOs)-based NFs for their further applications in high-performance electrochemical energy storage devices such as hybrid supercapacitors, batteries, and so on.

Insight into the composition effect of nickel cobalt layered double hydroxide nanoarrays with the enhanced synergistic effect for supercapacitor electrode

Rational post-treatment of Ni/Co-based electrode with high mass-loading in term of the increase of surface active sites and the enhancement of the synergistic effect is facile to achieve desirable electrochemical performances for energy storage. In this work, the composition effects on the structure and capacitive performance of NiCo layered double hydroxide (NiCo LDH) nanostructured is discussed, and subsequently the structural diversity of NiCo LDH is regulated via an alkali conversion. The result suggests that bimetallic synergistic effect can be enhanced via the charge exchange during alkali conversion, resulting in gradual increase surface content of Ni3+ and Co3+ cations. Such evolution endows Ni0.60Co0.40 LDH nanoarrays with outstanding performance as a battery-type Faradaic electrode material for supercapacitor, with areal capacity of 5.15 C cm−2 at 5 mA cm−2, excellent rate capability and high cyclic stability. The presented work not only provides a promising electrode material for supercapacitor, but also offers a new route toward understand the composition effect, bimetallic synergistic effect and the activation of Ni/Co-based electrode materials for energy storage and conversion.

Zeolitic imidazolate framework-L-assisted synthesis of inorganic and organic anion-intercalated hetero-trimetallic layered double hydroxide sheets as advanced electrode materials for aqueous asymmetric super-capacitor battery

Fine-tuning the interlayer space and composition of the layered double hydroxide (LDH) is a promising strategy to obtain high-performance battery-type electrode materials for super-capacitor battery. In this work, a series of two-dimensional (2D) porous hetero-trimetallic Zinc-Nickel-Cobalt LDHs sheets intercalated with nitrate anion and different Zn/Ni ratios (ZnxNi1-xCo-LDH-NO3–, x = 0, 0.25, 0.5, 0.75, and 1.0) are firstly synthesized through a Zeolitic imidazolate framework-L (ZIF-L)-assisted co-precipitation reaction and ion etching procedure. Among which, the Zn0.25Ni0.75Co-LDH-NO3– electrode, with a Zn/Ni ratio of 1:3, provides a high specific capacity (275 mAh g−1 at 1 A g−1). To further tune the interlayer space, Zn0.25Ni0.75Co-LDH-BA–/AA– (BA– = benzoate anion and AA– = acetate anion) sheets intercalated with BA– or AA– are synthesized by an anion-exchange method. A super-capacitor battery device (Zn0.25Ni0.75Co-LDH-BA–//activated carbon) using Zn0.25Ni0.75Co-LDH-BA– as the positive electrode can achieve a high energy density (51.8 Wh kg−1 at 789 W kg−1) and superb durability (94.6% over 10,000 cycles). This work can shed light on regulating the interlayer space of LDHs for advanced electrochemical energy storage applications.

Over-heating triggered thermal runaway characteristic of lithium ion hybrid supercapacitor based lithium nickel cobalt manganate oxide/activated carbon cathode and hard carbon anode

The energy density increase and the application of battery-type electrode materials and organic electrolyte for lithium ion hybrid supercapacitors (Li-HSCs) inevitably accompany the rising of thermal runaway. Herein, we fabricated a large-format pouch cell Li-HSC with activated carbon (AC) and lithium nickel cobalt manganate oxide (NCM) composite cathode, hard carbon (HC) anode, and ceramic polyethylene terephthalate (PET) nonwoven separator. The as-prepared Li-HSC delivers a capacitance of 34,476 F and a high energy density of 126 Wh kg−1 (based on the mass of device). The thermal runaway characteristic and gas release of this large-format Li-HSC are analyzed. Thermal runaway occurs for fully charged NCM/AC//HC Li-HSC at 249 °C, but not for fully charged AC//HC Li-HSC. The O2 releasing by NCM component accelerates the self-heating reactions, and the introduction of NCM into cathode is proved to contribute on triggering thermal runaway of NCM/AC//HC Li-HSC. The Li-HSC displays the highest runaway temperature (Tpeak) of 490.9 °C with smoke spurting out and does not catch fire or explode during thermal runaway. The main gas components at thermal runaway are C2H4, O2 C3H6 and C4H8, produced by the reaction between anode and electrolyte, and decomposition of NCM and electrolyte. The ratio of hydrocarbon gases and O2 decreases, while that of CO and CO2 increases at the Tpeak.

Micro-nano architecture with carbonaceous shell enables ultra-long cycling life of battery-type electrode materials in supercapacitors

In Faraday supercapacitors, battery-type materials despite their high theoretical capacity have not shown prospect yet in application primarily due to their especially low cycling stability (< 10,000 cycles), sharp contrast to the carbon materials in electrical double layer capacitors (>> 100,000 cycles). The so far materials structure-stabilizing strategies, established on the acknowledged structure-destabilizing mechanism under electrochemical stress, seem not significantly effective or practical. Actually, the misunderstanding on structure-destabilizing mechanism leads to the slow progress of battery-type materials in application. In this work, the intrinsic structure-destabilizing mechanism is revealed as the agglomeration of materials originating from their dissolution-recrystallization behavior instead of from electrochemical stress. Based on the as-proposed mechanism, a rod-like micro-nano architecture with a thin carbonaceous shell is designed and built deliberately for Ni(OH)2 notorious in its especially low stability as a demonstration for stabilizing the structure of battery-type materials. The carbonaceous shell blocks the interflow of dissolved species between Ni(OH)2 rods, significantly reducing their agglomeration. This structure-stabilizing effect enables Ni(OH)2 ultra-long cycling life of > 100,000 cycles, thus verifying the as-proposed structure-destabilizing mechanism. The positive results in this work suggest that the significance of battery-type materials in supercapacitors should be revalued.

Reduced-graphene-oxide-modified self-supported NiSe2 nanospheres on nickel foam as a battery-type electrode material for high-efficiency supercapacitors

Self-supported NiSe2 nanospheres have been successfully synthesized by a one-step microwave method, and then coated with a layer of reduced graphene oxide (rGO) by a simple dip-coating method. Due to the excellent conductivity and high surface area of rGO, as a battery-type electrode material, the as-prepared NiSe2@rGO composite exhibited an excellent specific capacity of 224.75 mAh g−1 at 1 A g−1, far exceeding that of the NiSe2 nanospheres (72.5 mAh g−1 at 1 A g−1). NiSe2@rGO showed good cycling performance, with 78.13% retention of its initial capacity after 5000 cycles. Furthermore, an NiSe2@rGO//activated carbon (AC) asymmetric supercapacitor (ASC) showed a high energy density (E) of 25.85 Wh kg−1 at a power density (P) of 730 W kg−1. The NiSe2@rGO//AC showed good capacity retention, maintaining 85.45% of the original value after 10000 cycles.

A strategy of combination reaction to improve electrochemical performance in two-dimensional Mo1-xWxSe2 battery-type electrode materials

We report here a case of combination reaction between MoSe2 and WSe2 in certain proportions to improve electrochemical performance of Mo1-xWxSe2 compound materials. Two-dimensional (2D) Mo1-xWxSe2 flower-like crystals (x = 0, 0.25, 0.5, 0.75, 1) were synthesized using a solution synthesis method, and then Mo1-xWxSe2-based electrodes were prepared using a powder pellet method. Their structure and electrochemical performance were respectively measured by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectrometer (XPS), scanning electron microscope (SEM), and electrochemical workstation. The results indicate that only Mo0.25W0.75Se2-based electrode (x = 0.75), compared with other electrodes, delivers excellent specific capacity and stability with the capacity retention of 74.4% after 5000 charging-discharging deep cycles at the current density of 2 A g−1 in 1.0 mol/L KOH aqueous electrolyte, and exhibits a Coulombic efficiency almost 100% after 5000 cycles. This phenomenon is attributed to a situation that Mo0.25W0.75Se2 active material has a quite different electronic band structure from the other remaining materials. It is therefore concluded that the combination reaction enables Mo1-xWxSe2 composite materials to realize their potential in electrochemical energy storage.

Binder-free Co–Ni hexacyanoferrate as a battery-type electrode material for hybrid supercapacitors

In this study, Co–Ni hexacyanoferrate (CoxNi3-xHCF) electrodes with different Co and Ni ratios were directly synthesized on Ni foam (NF) via a simple and cost-effective hydrothermal approach, and their physical and electrochemical properties were studied. The binder-free CoxNi3-xHCF@NF composites exhibited battery-like electrochemical storage mechanisms. Among them, the CoNi2HCF@NF composite exhibited the better charge storage properties with a specific capacity of 817 C g−1 at 1 A g−1. Furthermore, a hybrid supercapacitor (HSC) device with a CoNi2HCF@NF composite as the battery type and activated carbon as supercapacitor electrodes delivered a high energy density of 36 Wh Kg−1 at a power density of 1056 W kg−1 along with good cycling performance. This study introduces a feasible method to design such binder-free materials with optimized synergetic effects that are beneficial for designing next-generation HSC devices.

A flexible Zinc-ion hybrid supercapacitor constructed by porous carbon with controllable structure

The demand for developing sustainable energy storage renders biomass-based electrode materials a timely and important goal. However, the desirable electrochemical performance of the supercapacitor has still been hindered by insufficient contact chance between the active material and the electrolyte when both energy density and power density are required. Herein, the porous bamboo carbons were managed and used as the cathode to construct a flexible and high-performance Zn-ion hybrid supercapacitor (ZHSC) by combining the merit of capacitor-type and battery-type electrode materials. The porous material with high porosity is obtained via a controllable structural optimization. Consequently, the as-constructed hybrid supercapacitor delivers a superior specific capacitance of 321.3F g−1 at 1 A g−1 together with a high energy density of 114.2 Wh kg−1 when the power density is 800.0 W kg−1. Meanwhile, the assembled flexible hybrid supercapacitor displays remarkable cycling stability with 78% capacitance retention after 20,000 cycles and enough to suffer various deformations with no noticeable degradation of capacitance. Finally, the potential practical value of the flexible hybrid supercapacitor is demonstrated by an eye-catching orbital diagram. This work reveals that the flexible supercapacitor mainly constructed by porous biomass carbon is a promising candidate for energy storage devices.

NiAlP@Cobalt substituted nickel carbonate hydroxide heterostructure engineered for enhanced supercapacitor performance

Transitional metal phosphides with high electrical conductivity and superb physicochemical features have been recognized as ideal battery-type electrode materials for outstanding performance supercapacitors. However, their specific capacities and structural stability are needed to be enhanced for large-scale practical applications. To overcome these shortcomings, we fabricated heterostructured NiAlP@cobalt substituted nickel carbonate hydroxide (Co-NiCH) nanosheet arrays by sequential a hydrothermal reaction, a phosphorization treatment, and a second hydrothermal reaction. Profiting from its core–shell porous nanostructure and synergistic effect of NiAlP with high electrical conductivity and Co-NiCH with high redox reactivity, the resultant NiAlP@Co-NiCH electrode delivers a large specific capacity of 825.7C g−1 at 1 A g−1, excellent rate capability with 78.9% capacity retention and long lifespan, superior to those of pure NiAlP and Co-NiCH electrodes. Additionally, an aqueous asymmetric supercapacitor device is constructed by NiAlP@Co-NiCH and lotus pollen-derived hierarchical porous carbon, which demonstrates a large energy density of 82.3 Wh kg−1 at a power density of 739.8 W kg−1, and wonderful cycle stability with 88.2% capacity retention after 10,000 cycles. This work proposes a feasible strategy on construction of transitional metal phosphide-based heterojunctions for advanced asymmetric supercapacitor devices.