Extraordinary Cycling Stability Research Articles

A Trifunctional Hydroxylated Borophene‐Mediated MXene Enabled Super‐Stable and Fast‐Kinetics Interface Storage

AbstractThe high electronic conductivity and tailorable structural properties of MXene materials make them promising candidates for energy storage. However, their poor chemical instability and self‐stacking effect greatly limit their application, especially in aqueous systems. Here, using a eutectic etching approach, hydroxylated borophene is used as a trifunctional mediator to construct robust Ti3C2Tx‐based MXene/B self‐assembled film electrodes for zinc‐ion capacitors (ZICs). Due to this mediator, the as‐formed strong interfacial binding within the heterostructure can give rise to an integrated modification effect and promote high‐efficiency interface energy storage. One is to strengthen the thermodynamic stability of local Ti─O bonds and inhibit the irreversible degradation of MXene; two is to enlarge the interface space of the MXene electrode and boost the ion transport; three is to improve the interfacial Zn2+ trapping ability without affecting Zn2+ migration on the MXene surface. Thus, the MXene/B electrode exhibits a high areal capacitance (537.9 mF cm−2) at a current density of 0.2 mA cm−2 and an extraordinary cycling stability at 1 mA cm−2, with 99.64% retention after 40 000 cycles, which far surpasses that of most previous reports. This work provides a pathway for overcoming the interface storage limit of MXene electrodes to construct high‐performance ZICs.

Facile synthesis and modification of Fe2O3 nanorod arrays on carbon paper as efficient negative electrodes for supercapacitors

In this research, Fe2O3 nanorod arrays grown on carbon fiber paper were studied, and carbon-coated Fe2O3 (Fe2O3 @C) and sulfurized Fe2O3 @C (Fe2O3 @C-S) were fabricated by carbon coating and sulfurization processes. To promote the application of these materials in supercapacitors, their electrochemical properties were systematically investigated. Based on the results, the materials obtained utilized a pseudocapacitive mechanism for energy storage. Specifically, Fe2O3 exhibited a moderate specific capacitance and extraordinary cycling stability, and no degradation was observed after 10,000 cycles. Impressively, sulfurization greatly enhanced the rate capability and specific capacitance of the sample. As a result, Fe2O3 @C-S attained a specific capacitance of 976.4 mF cm–2 at 4 mA cm–2 and a robust rate capability of 97.30% at 20 mA cm–2, outperforming Fe2O3 @C (84.39%) and Fe2O3 (70.55%) and demonstrating good cycling stability (92.9%). Notably, Fe2O3 @C-S was active as a positive electrode material; thus, a symmetric supercapacitor was assembled, which yielded a volumetric energy density of 1.46 mWh cm–3 at 16.71 mW cm–3 and maintained an energy density of 0.91 mWh cm–3 even at 145.63 mW cm–3. Moreover, the device exhibited good cycling stability with a capacity retention of 88.3% after 10,000 cycles at 10 mA cm–2. The integration of Fe2O3 nanorod arrays on conductive substrates, coupled with the above modifications, strongly promoted the material’s energy storage performance. Our study emphasized the significant potential of Fe2O3 @C-S as an efficient electrode material for supercapacitors.

Spongelike Bimetallic Selenides Derived from Prussian Blue Analogue on Layered Ni(II)-Based MOF for High-Efficiency Supercapacitors.

Recently, employing metal-organic frameworks (MOFs) as precursors to prepare various metal oxides, sulfides, and selenides has drawn enormous attention in the field of energy storage. In this paper, the nanosheets of an organophosphate-based Ni-MOF were successfully synthesized and employed as the template to prepare the Prussian blue analogue (PBA) nanoslices and nanoparticles on the nanosheet (PBA/Ni-MOF-NS-x h, x h stands for the reaction time.) by an in situ etching method. After selenization by the solvothermal method, the PBA nanoslices and nanoparticles were transformed into spongelike bimetallic selenides (labeled as PBA/Ni-MOF-NS-x h-Se) decorated with some nanoparticles. All of the characterization results including PXRD, SEM, TEM, EDS, XPS, and BET demonstrated the successful transformation. Impressively, the as-synthesized PBA/Ni-MOF-NS-12 h-Se exhibited a high specific capacitance of 1897.90 F g-1 at a current density of 1 A g-1 and a superior capacitance retention rate of 73.32% as the current density increased to 20 A g-1. In addition, the asymmetric supercapacitor device, PBA/Ni-MOF-NS-12 h-Se//AC, delivered a high energy density of 30.69 W h kg-1 at 0.85 kW kg-1 and extraordinary cycling stability with an 83.00% capacitance retention rate over 5000 cycles.

Investigation on high performance and stabilized surface of AlF3-coated V2O5 micro-flower for zinc energy storage

Vanadium oxide (V2O5) cathode material, possessing abundant reserves and high theoretical capacity, has been extensively researched in aqueous zinc ion batteries (ZIBs). However, its electrochemical performance is significantly hindered by insufficient electronic conductivity, vanadium dissolution into electrolyte, and slow diffusion kinetics. In this study, the V2O5 micro-flower was first synthesized by a solvothermal method, and then modified by coating with AlF3 passivation layer, forming AlF3@V2O5 hybrid material. Impressively, AlF3@V2O5 exhibits excellent electrochemical and kinetic properties due to the special structure of V2O5 and the interfacial protection of AlF3. An exceptional rate property (325 mAh g−1 at 0.1 A g−1, 188 mAh g−1 at 15 A g−1) as well as extraordinary cycling stability with 89.3% capacity retention after 6000 cycles at 10 A g−1 can be attained with 2 wt% AlF3 addition (that is AF-2@V2O5). The computation based on density functional theory (DFT) suggests that AlF3 coating can reduce the interlayer electrostatic interaction and adsorption energy barrier between the intercalated Zn2+ and V2O5 host, thereby enabling fast redox kinetics. This study showcases the efficacy of interfacial modification of passivated coatings and presents an influential approach for material design in ZIBs.

Battery-Type Behavior of Al-Doped CuO Nanoflakes to Fabricate a High-Performance Hybrid Supercapacitor Device for Superior Energy Storage Applications

The ever-increasing energy demands have prompted researchers to develop innovative charge-storage devices. Here, aluminum-doped copper-oxide nanoflakes were fabricated via a simple co-precipitation method to investigate the electrochemical properties, which depicted a novel dominant battery-type charge-storage mechanism, manifested by the porous morphology of the electrodes to enhance the diffusion-controlled process. Copper oxide was chosen as the electroactive material due to its low cost, easy processability, environmental friendliness, and multiple oxidation states, all of which are very important for practical applicability in charge-storage devices. Additionally, aluminum was chosen as a dopant due to its elemental abundance, non-toxicity, and energetically favorable ionic radius for substitutional doping. A maximum 272 C/g (@1 A/g current-density) specific capacity was observed for 5 wt% Al-doped CuO. Evidently, higher Al-doping provided increased defects and doping sites to enhance the redox activity in order to improve the supercapacitive performance. A combinatorial battery−capacitor charge-storage mechanism was proposed in terms of the accumulation and intercalation of charges at the inner electroactive sites of the nanoflakes through a large number of voids and cavities in order to contribute towards dominant battery-type diffusion capacitance, while optimum Al-doping created considerable redox-active sites to promote surface-controlled pseudocapacitance. The optimized Al-CuO electrode revealed extraordinary long-term cycling stability with 99% capacity retention over 5000 charge/discharge cycles. A hybrid two-electrode device, made up of a battery type Al-CuO positrode and capacitor-type activated-carbon negatrode, demonstrated a remarkable energy-power performance with a maximum energy density of 30 Wh/kg and a maximum power density of 7.25 kW/kg, with an excellent cycle life (98% capacity retention over 5000 cycles). This work demonstrates a novel strategy to fabricate high-performance hybrid supercapacitors for the next generation charge-storage devices.

Electrodeposition of nanoporous conjugated copolymer on functionalized carbon cloth with extraordinary cycling stability for high-performance flexible supercapacitors

Conjugated polymers (CPs) have been widely used as pseudocapacitive materials in supercapacitors owing to their excellent conductivity and low processing costs. However, their low ionic diffusivity, sluggish charge transfer kinetics, and volume shrinkage/expansion during charging/discharging seriously reduce the capacity and cycle stability. Here, electrochemical copolymerization of aniline and 1,5-diaminoanthraquinone (DAA) was conducted on functionalized carbon cloth (FCC) to tune the structure and morphology of CPs for a better application in high-performance flexible supercapacitors. At an optimized feeding ratio, nanoporous conjugated copolymer coated FCC (FCC@PDA-AN-4) was obtained, possessing a high areal specific capacitance of 2847 mF cm−2 at 1 mA cm−2 with superior cycle life of 127.3% of its initial capacitance after 10,000 cycles.

Polymer-in-Salt Electrolyte from Poly(caprolactone)-graft-polyrotaxane for Ni-Rich Lithium Metal Batteries at Room Temperature.

Solid-state lithium batteries with solid polymer electrolytes have recently attracted extensive attention due to their promising potential in high energy density and safety. However, the principal issues plaguing the solid polymer electrolytes are their restricted ionic conductivities at ambient temperature and the limited tolerance to the widely used high-voltage cathodes (such as LiNi0.8Mn0.1Co0.1O2, NCM811), thus limiting their practical applications seriously. In this regard, a superior polymer-in-salt solid electrolyte from poly(caprolactone)-graft-polyrotaxane (PGPE) is developed for high-voltage lithium batteries operated at room temperature. The PGPE displays remarkable electrochemical properties at room temperature, with an exceptional ionic conductivity of 4.89 × 10-4 S cm-1 and a lithium-ion transference number of approximately 0.64, stemming from the rapid segmental motions of PCL sidechains by the enhanced dynamics of the cyclic molecules along the axial polymer chain of polyrotaxane. More importantly, the PGPE demonstrates a high electrochemical oxidation voltage of ∼4.7 V, suggesting the excellent electrochemical stability of PGPE against the NCM811-based cathode. Owing to the dense LiF-rich CEI self-generated on the NCM811 particles in the cathode, the transition metal ion diffusion is successfully constrained and the PGPE is well protected from continuous decomposition. The PGPE also shows superior interfacial stability between the metallic Li and the electrolyte. As a result, the all-solid-state NCM811|PGPE|Li cell exhibits superior discharge capacity (196 mAh g-1) and extraordinary long-term cycling stability (74% capacity retention at 150 cycles) at 30 °C.

Integrated MnO2/PEDOT composite on carbon cloth for advanced electrochemical energy storage asymmetric supercapacitors

Advanced flexible supercapacitors with high energy/power density are an imperative research objective. In this study, a dually activated carbon cloth is designed as the functional current collector for supercapacitors. An electrodeposition technique is used for engineering Manganese Dioxide (MnO2) nanoflakes and profiting from a Poly (3,4 ethylene dioxythiophene; PEDOT) shield layer, a Li+-based neutral electrolyte high-performance freestanding asymmetric supercapacitors is constructed. The activated carbon cloth (ACC) provides an efficient electron-carrying route and the hierarchical nanostructure of the ACC@MnO2@PEDOT electrode. The integrated ACC@MnO2@PEDOT electrode exhibited exceptional capacitance performance of 1882.5 mF cm−2 (current density 1 mA cm−2) in 1.5 M aqueous LiCl electrolyte benefiting from ACC scaffold, the pseudocapacitive activity of MnO2 and substantial conductivity of the PEDOT polymer. Fabricating the structured electrode into an asymmetric supercapacitor revealed an enhanced areal energy density and an areal power density. The fabricated device demonstrated a broad voltage window of 1.8 V and extraordinary cycling stability of 94.6% after 10000 charge-discharge cycles. The unique scaffold, conducting PEDOT polymer, and MnO2 nanoflakes synergistically improved the cyclic performance and rate proficiency of the electrode, resulting in a supercapacitor with bendable electrical energy storage applications.

Tightly confined iodine in surface-oxidized carbon matrix toward dual-mechanism zinc-iodine batteries

The dissolution of iodine species into the aqueous electrolyte is an inevitable issue in zinc-iodine (Zn-I2) battery, leading to its fading capacity and inferior cycle life. Herein, the porous oxidized salt-templated carbon (OSTC) with abundant carbonyl groups is prepared by using H2O and ZnCl2 as gasification agent/oxidant and salt-template, respectively. The synergistic effect of oxygen-containing functional group and unique pore structure in OSTC makes it a promising host to confine iodine tightly, resulting in the extraordinary cycling stability (a high capacitance retention of 85.04% after 10,000 cycles) and excellent rate performance for the as-assembled Zn-I2 battery. Experimental ex-situ and in-situ characterizations, and theoretical calculations (density functional theory calculation and COMSOL Multiphysics simulation) are conducted jointly to reveal its dual energy storage mechanisms: (1) only one-step redox reaction between I2 and I− can be observed without any appearance of I3− intermediates that is beneficial to increasing the utilization of iodine; (2) the abundant C=O groups on the OSTC surface can also react with the Zn2+ ions to form C-O-Zn group and provide extra pseudocapacity for Zn-I2 battery. This work not only presents a high-performance cathode for Zn-I2 battery, but also sheds light on possible strategies for other metal-I2 batteries.

Metal Chelation Enables High-Performance Tea Polyphenol Electrodes for Lithium-Ion Batteries

The application of organic electrode materials can make the whole cycle of the lithium battery operation effective for green sustainability. However, poor electronic conductivity and strong solubility in nonprotonic electrolytes limit the application of organic anodes. Here, a novel organic anode material, TP-Ni, was fabricated through the simple chelation of tea polyphenols with nickel ions. Benefiting from coordination bonds that alter the intrinsic microstructure of TPs and contribute to pseudocapacitive charging, the TP-Ni anode exhibits remarkable electrochemical properties, including a high specific capacity (1163 mAh g−1 at 0.1 A g−1), superb rate capability, and extraordinary cycling stability (5.0 A g−1 over 4000 cycles with a capacity retention of 87.8%). This work can provide guidance for the design and synthesis of new high-performance organic electrode materials in the future and help accelerate the process of organic electrode material applications.

Carbon dots integrated into nickel-cobalt hydroxide as superior electrode for supercapattery

Nickel hydroxide (Ni(OH)2) is one of the most valuable electrode materials for supercapacitors. Owing to the low stability and conductivity of Ni(OH)2 electrode, the preparation of a fast and high-stability Ni(OH)2 electrode is a significant challenge. Nickel hydroxide integrated with cobalt and carbon dots (CDs-Co/Ni(OH)2) as a high performance electrode has been prepared by cathodic electrodeposition for supercapattery in this work. Compared with unintegrated Ni(OH)2 electrode or carbon dots integrated Ni(OH)2 electrode, the introduction of Co greatly improves the stability of the Ni(OH)2 electrode, particularly at high current density. The as-obtained CDs-Co/Ni(OH)2 electrode presents a high specific capacitance of 338.6 mAh/g at 5 A/g and an extraordinary cycling stability with 1000 cycles even under a high current density of 40 A/g (retaining 84.6%). Besides, the CDs-Co/Ni(OH)2 electrode exhibits an energy density of 281.2 Wh/kg at a power density of 57.2 kW/kg. Such a glorious stable CDs-Co/Ni(OH)2 electrode may provide significant insight into future multifarious electronics and electrified vehicle applications.

Water-Stabilized Vanadyl Phosphate Monohydrate Ultrathin Nanosheets toward High Voltage Al-Ion Batteries.

Al ion batteries (AIBs) are attracting considerable attention owing to high volumetric capacity, low cost, and high safety. However, the strong electrostatic interaction between Al3+ and host lattice leads to discontented cycling life and inferior rate capability. Herein, a new strategy of employing water molecules contained VOPO4 ·H2 O to boost Al3+ migration via the charge shielding effect of water is reported. It is revealed that VOPO4 ·H2 O with water lubrication effect and smaller steric hindrance owns high capacity and fast Al3+ diffusion, while the loss of unstable water upon cycling leads to a rapid performance degradation. To address this problem, ultrathin VOPO4 ·H2 O@MXene nanosheets are fabricated via the formed TiOV bond between VOPO4 ·H2 O and MXene. The MXene aided exfoliation results in enhanced VOwater bond strength between H2 O and VOPO4 that endows the obtained composite with strong water holding ability, contributing to the extraordinary cycling stability. Consequently, the VOPO4 ·H2 O@MXene delivers a high discharge potential of 1.8V and maintains discharge capacities of 410 and 374.8 mAh g-1 after 420 and 2000 cycles at the current densities of 0.5 and 1.0 A g-1 , respectively. This work provides a new understanding of water-contained AIBs cathodes and vital guidance for developing high-performance AIBs.

Bowl-shaped hollow carbon wrapped in graphene grown in situ by chemical vapor deposition as an advanced anode material for sodium-ion batteries

Sodium-ion batteries (SIBs) are expected to be ideal alternatives to lithium-ion batteries (LIBs) in the future due to their abundant and low-cost resource advantages. A key challenge in SIBs is the development of anodes capable of insertion/extraction of sodium ions (Na+) with large radii. Here, hollow bowl-shaped porous carbon materials are uniformly modified with vertically grown graphene (denoted as HBC/VGSs) demonstrating a large specific surface area and three-dimensional structure, which are employed as a viable high-performance anode for SIBs. HBC/VGSs anodes are highly effective at storing sodium because of their structural features. As a result, the HBC/VGSs electrodes provide a high reversible capacity of 409 mAh g−1 after 100 cycles at 0.1 A g−1, as well as outstanding rate capability (301.6 mAh g−1 at 5 A g−1). Moreover, it also shows extraordinary cycling stability (230.3 mAh g−1 after 2500 cycles at a high current density of 5 A g−1) that is significantly better than the pristine hollow bowl-shaped porous carbon (HBC). Cyclic Voltammetry (CV) and Galvanostatic Intermittent Titration Technique (GITT) were used to analyze the pseudocapacitance and sodium storage kinetics. It was found that high electrical conductivity and large surface area can improve Na+ adsorption and diffusion, enhance the electronic conductivity, and deliver superior capacity and rate. The results, taken as a whole, provide new insight into the creation of long-lasting carbon anodes that deliver optimal performance in SIBs.

Yolk-Shell Sb@Void@Graphdiyne Nanoboxes for High-Rate and Long Cycle Life Sodium-Ion Batteries.

Antimony (Sb) has been pursued as a promising anode material for sodium-ion batteries (SIBs). However, it suffers from severe volume expansion during the sodiation-desodiation process. Encapsulating Sb into a carbon matrix can effectively buffer the volume change of Sb. However, the sluggish Na+ diffusion kinetics in traditional carbon shells is still a bottleneck for achieving high-rate performance in Sb/C composite materials. Here we design and synthesize a yolk-shell Sb@Void@graphdiyne (GDY) nanobox (Sb@Void@GDY NB) anode for high-rate and long cycle life SIBs. The intrinsic in-plane cavities in GDY shells offer three-dimensional Na+ transporting channels, enabling fast Na+ diffusion through the GDY shells. Electrochemical kinetics analyses show that the Sb@Void@GDY NBs exhibit faster Na+ transport kinetics than traditional Sb@C NBs. In situ transmission electron microscopy analysis reveals that the hollow structure and the void space between Sb and GDY successfully accommodate the volume change of Sb during cycling, and the plastic GDY shell maintains the structural integrity of NBs. Benefiting from the above structural merits, the Sb@Void@GDY NBs exhibit excellent rate capability and extraordinary cycling stability.

Polypyrrole-coated V2O5 nanobelts arrays on carbon cloth for high performance zinc energy storage

V2O5 is considered as a promising cathode material for zinc ion batteries due to its abundance, low-cost, layered structure and high capacity. However, low electronic conductivity, vanadium dissolution accompanied with sluggish ion transport kinetics, severely limit its electrochemical performance. Herein, the polypyrrole-coated V2O5 nanobelts arrays grown on carbon cloth (PPy@V2O5/CC) are rationally designed and prepared by combination of solvothermal and vapor-phase polymerization process. The resultant flexible PPy@V2O5/CC electrode delivers a high specific capacity of 276 mAh g−1 at 0.1 A g−1, an excellent rate capability of 185 mAh g−1 at 10 A g−1, and extraordinary long-term cycling stability with 76% capacity retention after 8000 cycles at 5 A g−1, better than V2O5/CC. The significant enhancement can be attributed to the PPy protective layer, which can simultaneously achieve higher electronic conduction, suppressed vanadium dissolution, enhanced surface pseudocapacitive behavior, and faster Zn2+ diffusion rate. This work offers a novel strategy for constructing high-performance micro/nano functional composites for electrochemical energy storage system.

Phase transformation controlled Co1−xS-CoS2 heterostructures embedded in S-doped carbon nanofibers for superior Sodium-Ion storage

Cobalt-based sulfides are considered as a promising anode material for sodium-ion batteries (SIBs) due to its various chemical formulations and high theoretical capacity. However, slow kinetics and structural instability lead to unsatisfactory electrochemical performance. Herein, ultrafine particles with Co1−xS-CoS2 heterostructures precisely controlled by phase transformation has been integrated with the encapsulation with S-doped carbon nanofiber through the one-stone-two-birds strategy. Due to the abundant heterointerfaces, unique yolk-shell structure and increased carbon interlayer spacing in Co1−xS-CoS2/carbon nanofibers (Co1−xS-CoS2/CNF), the reaction kinetics and the diffusion rate of Na+ have been significantly improved. As expected, the as-prepared Co1−xS-CoS2/CNF anode exhibits extraordinary rate performance (495.3 mAh/g at 10 A/g) and cycling stability (380.1 mAh/g at 5 A/g after 5,000 cycles), outperforming most reported TMS materials. A sodium-ion full cell with a Co1−xS-CoS2/CNF anode and Na3V2(PO4)3 cathode also show excellent electrochemical performance. The electrochemical reaction mechanism of Co1−xS-CoS2/CNF is revealed by ex-situ XRD and ex-situ HRTEM. Hence, it is hoped that our work can provide constructive ideas for the design of electronic or morphological structures for building high-performance energy storage materials.

Sulfur-Doped Carbon for Potassium-Ion Battery Anode: Insight into the Doping and Potassium Storage Mechanism of Sulfur.

The sulfur doping strategy has been attracting extensive interest in potassium-ion battery carbon anodes for the dual potential of improving the capacity and kinetics of carbon anodes. Understanding the doping and potassium storage mechanism of sulfur is crucial to guide the structural design and optimization of high-performance sulfur-doped carbon anodes. Herein, presenting a laboratory-synthesized sulfur-doped hard carbon (SHC) with a sulfur content of 6.4 at. % as an example, we clarify the sulfur doping mechanism and reveal the role of sulfur in potassium storage. The high sulfur content of SHC stems from the selective substitution of sulfur for carbon and the residual trace of sulfur molecular fragments after sulfurization. As a result, thanks to the multifaceted roles of doped sulfur in potassium storage, about twice as much capacity, rate capability, and cycling stability is achieved for SHC against S-free hard carbon at the same test conditions. Furthermore, potassium-ion hybrid capacitors assembled based on an SHC anode demonstrate high energy/power density (139 Wh kg-1/7.3 kW kg-1), along with an extraordinary cycling stability.

Understanding the Predominant Potassium-Ion Intercalation Mechanism of Single-Phased Bimetal Oxides by in Situ Magnetometry

The electrochemical performance of electrode materials is largely dependent on the structural and chemical evolutions during the charge-discharge processes. Hence, revealing ion storage chemistry could enlighten mechanistic understanding and offer guidance for rational design for energy storage materials. Here, we investigate the mechanisms of potassium (K)-ion storage in the promising bimetal oxide materials by in situ magnetometry. We focus on a single-phased hollow FeTiO3 (SPH-FTO) hexagonal prism synthesized through a complexing-reagent assisted approach and find that the K-ion storage in this compound occurs predominantly with an intercalation mechanism and fractionally a conversion mechanism. We also demonstrate a K-ion hybrid capacitor assembled with the prepared SPH-FTO hexagonal prism anode and activated carbon cathode, delivering a high energy density and high power density as well as extraordinary cycling stability. This new understanding is used to showcase the inherently high K-ion storage properties from the earth-abundant FeTiO3.

Chemical-etching strategy tailoring hollow carbon confined highly dispersed CoP nanoparticles for durable potassium storage

Implanting nano-scaled CoP particles into hollow carbon is usually regarded as an effective strategy to improve structural stability for potassium ion batteries (PIBs). Hence, we employ tannic acid (TA) as the chemical-etching agent to elaborately synthesize a novel hollow hybrid composite composed of highly dispersed CoP nanoparticles (10-20 nm) embedded in well-developed carbon shell (CoP/C-2). The nano-sized CoP significantly shortens the diffusion distance of K-ions within electrode, while the highly dispersed features can expose more active surface to electrolyte by avoiding self-agglomeration, endowing improved reaction kinetics. Besides, the presence of carbon shell provides sufficient buffer space for volume variation, all of which are conducive to maintaining structural integrity against pulverization upon repeated cycling. When used as an anode for PIBs, the optimized CoP/C-2 exhibits an extraordinary cycling stability by keeping a high reversible capacity of 103.4 mAh g−1 after 1000 cycles at 2 A g−1, outperforming most previously reported literatures. The strategy presented in this work may provide a reference for constructing other advanced CoP-based abodes for PIBs.

Construction of hierarchical sugar gourd-like (Ni,Co)Se2/(Ni,Co)Se2/CC nanostructure with enhanced performance for hybrid supercapacitor

Transitional metal selenides are regarded as promising electrode materials for battery-type electrodes on account of their superior electrical conductivity and high redox activity. It is expected to further improve their electrochemical performance by reasonable designing of the metal selenides’ components and construction of novel nanostructures. Thus, in this article, self-supported sugar gourd-like (Ni,Co)Se2/(Ni,Co)Se2 composites on carbon cloth are prepared by a facile approach. The theoretical calculations indicate that the (Ni,Co)Se2 has higher conductivity and larger adsorption energy of OH- than that of NiSe2 and CoSe2, thus effectively improving the kinetics of their electrochemical reactions. Thanks to synergetic effects from the active materials and their hierarchical nanostructures, the prepared sugar gourd-like (Ni,Co)Se2/(Ni,Co)Se2/CC nanoarrays achieve a high areal specific capacity of 1.278 mAh/cm2 (220.34 mAh/g) at 2 mA/cm2 and 88.9 % capacity retention after 5000 cycles. Furthermore, the flexible hybrid supercapacitor based on the designed nanocomposite demonstrates a high energy density of 0.7051 mWh cm−2 at the power density of 1.6303 mW cm−2 with extraordinary cycling stability. Such eminent energy storage performances strongly certificate that the obtained (Ni,Co)Se2/(Ni,Co)Se2/CC electrode is a potential battery-type electrode material for supercapacitor application.