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The design of a reasonable heterostructure electrode to achieve enhanced areal performance for supercapacitors remains a great challenge. Here, we constructed hierarchical porous NiCoP/NiO nanocomposites anchored on Ni foam with tunable electronic and structural properties, as well as robust interfacial interaction. In NiCoP/NiO, the interconnected NiO nanosheets serve as a carrier with enriched anchoring sites to confine the NiCoP and improve its stability. Meanwhile, the ultrathin NiCoP nanosheets with bimetallic centers are connected with porous NiO nanosheets to form a reliable heterojunction, enhancing the electrochemical reaction kinetics. Taking advantage of the synergistic contribution of bimetallic centers, phosphides and unique structure, the NiCoP/NiO delivers a high areal specific capacitance (1860 mF cm−2 at 5 mA cm−2), good rate performance of 78.5% at six times the increased current density, and remarkable durability (11.0% decrease after 10,000 cycles). Furthermore, the assembled hybrid supercapacitor NiCoP/NiO//porous-activated carbon (PAC) delivers a high areal energy density of 173.7 μWh cm−2 (116.4 μWh cm−2) at 1.6 mW cm−2 (32 mW cm−2). The results indicate that the design of the heterostructure interface with strong chemical interface and tunable electronic structure is an effective and promising approach to boost the electrochemical performance for advanced supercapacitors. [ABSTRACT FROM AUTHOR]

A supercapacitor features high power density and long cycling life. However, its energy density is low. To ensemble a supercapacitor with high power‐ and energy‐densities, the applied capacitor electrodes play the key roles. Herein, a high‐performance capacitive electrode is designed and grown on a flexible carbon cloth (CC) substrate via a hydrothermal reaction and a subsequent ion exchange sulfuration process. It has a 3D heterostructure, consisting of sulfur‐doped NiMn‐layered double hydroxide (LDH) nanosheets (NMLS) and sulfur‐doped NiCo‐LDH nanowires (NCLS). The electrode with sheet‐shaped NMLS and wire‐shaped NCLS on their top (NMLS@NCLS/CC) increases the available surface area, providing more pseudocapacitive sites. It exhibits a gravimetric capacity of 555.2 C g−1 at a current density of 1 A g−1, the retention rate of 75.1% when the current density reaches up to 20 A g−1, as well as superior cyclic stability. The assembled asymmetric supercapacitor that is composed of a NMLS@NCLS/CC positive electrode and a sulfurized activated carbon negative electrode presents a maximum energy density of 24.2 Wh kg−1 and a maximum power density of 16000 W kg−1. In this study, a facile strategy for designing hierarchical LDH materials is demonstrated as well as their applications in advanced energy storage systems. [ABSTRACT FROM AUTHOR]

The electrochemical performance of hybrid capacitors is seriously affected by the slow charging and discharging of the bulk phase. Here, Co-doped amorphous NiMoS4 modified with reduced graphene oxide (rGO) was prepared by a simple one-step hydrothermal method, and the obtained Co-doped NiMoS4/rGO nanocomposite (Ni1−xCoxMoS4/rGO) exhibits a high specific surface area, realizing the redox reaction from the bulk to the surface. Owing to the doping of Co with abundant redox active sites and the support of rGO sheets with high conductivity and a stable structure, the Ni1−xCoxMoS4/rGO anode assembled with an oxidized needle coke (NCO) cathode shows an excellent energy density of 28.9 W h kg−1 at a power density of 968.3 W kg−1. In addition, the hybrid supercapacitor displays a superior cycling performance with a capacity retention of 92.4% after 10 000 cycles. The construction of the Co-doped NiMoS4/rGO nanocomposite provides an effective strategy to boost the activity and stability of amorphous NiMoS4 for high-performance hybrid supercapacitors. [ABSTRACT FROM AUTHOR]

The porous flower-like microsphere structure composite of gadolinium oxide (Gd2O3), tricobalt tetraoxide (Co3O4) and reduced graphene oxide (rGO) was prepared on the nickel foam (NF) substrate by a hydrothermal synthesis method and annealing process, which can be directly used as an electrode material for supercapacitors without any conductive adhesive or binder. This porous nanostructure not only improves the conductivity of the electrode, but also shortens the migration route of ions and electrons. The innovative electrode of Gd2O3/Co3O4/rGO/NF has a high specific capacitance of 3616 F g−1 (1 A g−1). The supercapacitor is assembled, with a specific capacitance of 442.5 F g−1 (0.5 A g−1) at room temperature (20 °C) and strong multiplicative performance (current density from 0.5 to 20 A g−1, specific capacitance retention of 65.9%). At a power density of 300 W kg−1, the energy density reaches 88.5 Wh kg−1, and the performance stays relatively stable across a large working temperature range of 0 to 60 °C. The specific capacitance is 368.3 F g−1 even at temperatures up to 60 °C and 415.0 F g−1 at temperatures below 0 °C. Even after 40 000 cycles at a high current density of 10 A g−1, the capacity retention is 93.3%, suggesting exceptional cycling stability. This study demonstrates the potential practical application of Gd2O3/Co3O4/rGO/NF electrodes in supercapacitors. [ABSTRACT FROM AUTHOR]

Porous hollow structures of electrode materials can enlarge the surface area in contact with electrolytes, accelerating the transport of ions and electrons during redox reactions to enhance the electrochemical performance of the electrode materials. Herein, this work presents a facile method to synthesize NiCo2Se4 hollow microspheres (NiCo2Se4 HMSs) and BiSe hollow microspheres (BiSe HMSs) based on a self-template and selenide strategy. NiCo2Se4 HMSs deliver a high specific capacitance of 262.0 mA h g−1 (1874.6 F g−1) at a current density of 1 A g−1 and good rate capability (74.9% capacitance retention at 20 A g−1), which is superior to many Ni/Co-based electrode materials. Meanwhile, BiSe HMSs show an amazing capacitance of 360 mA h g−1 (1293 F g−1) at 1 A g−1 and excellent rate capability (62.6% capacitance retention at 40 A g−1). On account of the unique chemical composition and structural features, the assembled NiCo2Se4 HMSs//BiSe HMSs asymmetric supercapacitors (ASCs) exhibit high energy density (76.73 W h kg−1 at 1.79 kW kg−1) and good capacitance retention (93.4%) after 3000 cycles. This study suggests that these unique selenide structures have potential applications in fabricating high-performance ASCs, which is expected to be one of highly prospective energy storage devices. [ABSTRACT FROM AUTHOR]

As an electrochemical energy storage material, transition metal layered double hydroxides (MLDHs) have attracted attention due to tunable two‐dimensional structure and low cost. In this study, NiMn‐LDH@MWCNT composites with hierarchical structure have been successfully synthesized with simple and economical one‐step hydrothermal method. The hierarchical structure of composites was formed by NiMn‐LDH nanosheets growing directly on multiwall carbon nanotubes (MWCNTs). This design not only can maintain excellent network conductive channels, but also increase active sites, enlarge specific surface area, and reduce internal resistance. Our results show that the NiMn‐LDH‐4 composite exhibits an excellent electrochemical performance with an ultrahigh specific capacitance of 1863 F g−1 at a current density of 1 A g−1 and 1164 F g−1 when the current density goes up 10 times. This may be attributed to the synergy effect of the hierarchical structure and introduction MWCNT. Moreover, the assembled NiMn‐LDH‐4//AC device can provide a relatively high specific energy density of 51.5 Wh kg−1 at a high energy density of 455.7 W kg−1 and possess great cycling stability (83.9 % capacitance retention after 5000 cycles). [ABSTRACT FROM AUTHOR]

Co9S8 and transition metal hydroxides are both potential pseudo-capacitance electrode materials for supercapacitors. Co9S8 has a large specific capacitance and electrochemical activity, and transition metal hydroxides have the advantages of high capacitance and redox activity due to their multiple valence metals and open layered structure. In this study, Co9S8 and NiCoLDH are used to form a Co9S8–aCNT–NiCoLDH composite electrode material by twining acidified carbon nanotubes (aCNTs) around hollow Co9S8 rods and then compounding nickel cobalt hydroxide (NiCoLDH) on the outside. aCNTs provide more electronic channels, which bring more active electrochemical reactions and absorb the volume expansion of Co9S8. The hollow Co9S8 rods and flower-like NiCoLDH structures ensure that the electrode has a highly open structure, which increases the contact area with the electrolyte and is beneficial for ion transport. The outer NiCoLDH can also reduce the volume expansion of Co9S8. These advantages ensure the high specific capacitance and rate performance of the Co9S8–aCNT–NiCoLDH electrode material. Co9S8–aCNT–NiCoLDH was used as the positive material to fabricate asymmetric supercapacitors with attractive energy density and power density, which further proved its excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

In this work, honeycomb‐like Yb‐doped V2O5 ⋅ nH2O binder‐free thin film electrodes are synthesized via a simple and convenient sol‐gel method. Benefiting from the synergy of V2O5 ⋅ nH2O and rare‐earth metal ion Yb3+, thin‐layer honeycomb‐like morphology formed upon the introduction of Yb3+ into the V2O5 ⋅ nH2O, which markedly promotes the electrochemical performance of the V2O5 ⋅ H2O thin‐film electrode. After the condition optimization, 8 % Yb−V2O5 ⋅ H2O exhibits superior electrochemical performance with a specific capacitance of 703 F g−1 (at 1 A g−1) and outstanding cycling stability. Besides, owing to the ultra‐high conductivity of oxide super‐P (OSP) nanoparticles, the V2O5 ⋅ H2O@OSP‐4 binder‐free film electrode shows a high specific capacitance of 627 F g−1, which was prepared by the same simple sol‐gel strategy. The assembled 8 % Yb−V2O5 ⋅ nH2O//V2O5 ⋅ nH2O@OSP‐4 device delivers a high specific energy density and excellent cycling stability. This study may have certain inspirations for the fabrication of thin‐film electrodes for high‐efficiency energy storage systems. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional (3D) hierarchical Co3O4@NiS core–shell heterostructure supported on nickel foam (NF) has been constructed. This Co3O4@NiS/NF can directly serve as a binder-free electrode for a pseudocapacitor, which could achieve a high specific capacitance of 1395.3 F g−1 at a current density of 1 A g−1 in 6 M KOH electrolyte, and an ideal rate capability of 711 F g−1 at a current density of 10 A g−1. Additionally, the electrode has a high capacitance retention of 89.9% after 5000 cycles. The asymmetric supercapacitor exhibits the maximum energy density of 61.34 W h kg−1 at a power density of 800 W kg−1, as well as an excellent cycling life of 89.3% capacitance retention. The enhanced electrochemical performance can be mainly ascribed to the special 3D core–shell nanowire arrays nanostructure with great conductivity, enlarged surface area, abundant accessible active sites and intrinsic stability. We anticipate that the present Co3O4@NiS/NF could be a promising electrode material for energy storage applications. [ABSTRACT FROM AUTHOR]

Metallic 1T MoS2 greatly benefits the supercapacitance of MoS2 due to its considerably higher conductivity as compared to semiconducting 2H MoS2. Alkali metals, such as Li, Na and K, are always used to prepare 1T MoS2 through intercalation of alkali metal ions into the interlayer of 2H MoS2. Nevertheless, the influences of the alkali-earth metals as the guest in the interlayer of MoS2 on its structure and electrochemical capacitor performance are rarely investigated. Herein, we introduced hydrated Mg ions as the guest into MoS2 nanosheets. The interlayer spacing was increased to 1.144 nm after the introduction of hydrated Mg ions, larger than that of the pristine MoS2 (0.620 nm) and restacking MoS2 (0.626 nm). The enlarged interlayer spacing can accommodate more ions during intercalation process. Moreover, the 1T phase concentration after the introduction of hydrated Mg ions was as high as ~ 90%, which benefits the charge transfer during the charging/discharging processes. Consequently, the specific capacitance of the MoS2 with Mg guest ions as well as the energy densities and power densities was greatly improved as compared to those of the restacking MoS2 or pristine MoS2 counterparts. The present work not only demonstrated a new strategy for engineering the physical properties and improving the electrochemical performance of MoS2 supercapacitor electrode through pre-intercalation of alkali-earth metal ions in the interlayer of MoS2, but also has directive significance for the design of other layered electrode materials for energy storage systems. [ABSTRACT FROM AUTHOR]

Constructing a 3D hierarchical structure of electrode materials is a fast-developing technology to meet the increasing demand of high-rate electrochemical capacitors. Here, hierarchical CoNi2S4 nanofibers with pompom-like morphology are successfully synthesized via a two-step anion exchange reaction. The obtained CoNi2S4 nanofibers interweave densely with each other from inner core to external surface, constructing a stable 3D nanostructure. The pompom-like CoNi2S4 nanofibers have a high specific surface area of 169.7 m2 g−1 and a uniform nanopore size distribution in the range of 1–10 nm. Benefiting from these structural features, the pompom-like CoNi2S4 nanofibers provide more effective charge transport during electrochemical reactions compared with other 3D hierarchical structured CoNi2S4, such as flower-like nanosheets and urchin-like nanoneedles prepared by conventional methods. When evaluated as electrode materials in electrochemical tests, CoNi2S4 nanofibers with pompom-like hierarchical structure deliver a high specific capacitance of 2078.9 F g−1 at 0.5 A g−1 and an excellent rate capability of 844.4 F g−1 at 50 A g−1. The assembled CoNi2S4 nanofibers//activated carbon asymmetric electrochemical capacitor exhibits a good energy density of 48.2 W h kg−1 at a power density of 850 W kg−1, and a good cycling stability with 92.6% of its capacitance retained after 1000 cycles, suggesting that the pompom-like CoNi2S4 nanofibers can be applied as promising electrode materials for high-rate electrochemical capacitors. [ABSTRACT FROM AUTHOR]

Holey Fe-Anderson-type polyoxometalate/polyaniline/graphene (PPG) hybrid materials were first prepared by anchoring Anderson-type polyoxometalates [FeMo6O 2 4 H6] 3 − (FeMo 6) onto graphene modified with polyaniline via a facile hydrothermal treatment. The as-prepared materials exhibited an excellent electrochemical performance with a high specific capacitance of 1366 F g − 1 at 1 A g − 1 and outstanding cycling stability (97.6% capacitance retention after 5000 cycle times). The uptake of polyaniline/FeMo6 nanoparticles on graphene not only provided the pseudocapacitance but also weakened the aggregation between the graphene layers, resulting in a higher surface area compared with pure graphene. In addition, the AC//PPG-15 asymmetric supercapacitor device showed a high energy density of 24.65 W h kg − 1 at a low power density of 326.25 W kg − 1 and good cycling stability (94.82% capacitance retention after 5000 cycles). Hence, the as-prepared PPG hybrid materials in this work possess tremendous potential as electrodes for high-performance supercapacitors. Holey Fe-Anderson-type PPG hybrid materials were prepared via a facile hydrothermal treatment and subsequent freeze-drying process. Polyaniline/FeMo6 nanoparticles were well doped in graphene layers, which is favorable for improving ion and electron transport circumstances, resulting in high performance on the application of supercapacitor. [ABSTRACT FROM AUTHOR]

CoNi2S4/graphene nanocomposites were synthesized by a simple solvothermal method and used as supercapacitor electrodes. CoNi2S4 nanoparticles were doped in graphene layers, which is favorable for improving electrochemical performances of the as-prepared materials. The resulting electrochemical performance of CoNi2S4/graphene nanocomposite electrodes possessed pseudocapacitive behavior with high specific capacitance (1621 F g−1 at 0.5 A g-1), good rate capability (76.7% capacitance retention when reaching 10 A g-1) and outstanding cycling stability (no capacitance loss after 2500 charge-discharge cycles at 5 A g-1). In addition, as the positive electrode of an asymmetric supercapacitor, the material also shows a high specific capacitance of 126.6 F g-1 at 0.5 A g-1, good cycle stability with capacitance retention of 87.4% after 5000 cycles and the highest energy density of 39.56 W h kg-1 at the power density of 374.8 W kg-1. [ABSTRACT FROM AUTHOR]

The article discusses the fabrication of high-power lithium (Li)-ion supercapacitors (Li-HSCs) from the prospective of single electrodes and devices. It says that magnesium oxide (MnO)-graphene composite (MnO@GNS) was devised as the anode, while three-dimensional (3D) hierarchical porous nitrogen (N)-doped carbon (HNC) was used as the cathode. It states that the hybrid devices with high power and energy density were fabricated by enhancing the exterior surface charge storage.

[Display omitted] • Amorphous/crystalline H-NiMoS 4 /NiS 2 hollow sphere was successfully constructed. • A high specific capacitance and good cycling performance was obtained. • The capacity retention of HSC was 83.7% after 20,000 cycles. • The HSC displayed a high energy density of 38.6 Wh kg−1 at 958.6 W kg−1. Phase engineering offers a promising strategy to tailor the physiochemical properties to further improve their electrochemical performance toward energy storage. However, it remains a challenge to fabricate well-defined amorphous/crystalline hetero-phase metal sulfides with high-density heterointerfaces. Herein, the synthesis of hetero-phase combination of amorphous NiMoS 4 and crystalline NiS 2 that possesses hollow nanosphere structure decorated by nanosheets (named as H-NiMoS 4 /NiS 2) is reported. Benefiting from the construction of the hollow nanosphere coated by nanosheets, amorphous/crystalline hetero-phase junction, and strong Ni-S hybridization, H-NiMoS 4 /NiS 2 electrode exhibits high specific capacity, outstanding rate capability and excellent cycling stability. Moreover, an all-solid-state supercapacitor was assembled with H-NiMoS 4 /NiS 2 as cathode and needle coke oxide (NCO) as anode, which can achieve remarkably high energy density of 38.6 Wh kg−1 at a power density of 958.6 W kg−1 and outstanding capacity retention of 83.7% after 20,000 cycling. The preparation of novel H-NiMoS 4 /NiS 2 nanomaterial with a hetero-phase of amorphous and crystalline provides a new solution for improving the structural stability and capacitor storage performance as electrodes for supercapacitors. [ABSTRACT FROM AUTHOR]

• The δ-MnO 2 @Fe-CNFs with various morphology were fabricated by varying pH and Fe ratio. • The δ-MnO 2 @Fe-CNF-5% at pH = 2 shows tubular structure with uniform MnO 2 nanosheet assembly. • The δ-MnO 2 @Fe-CNF-5% has excellent supercapacitor performance. • The δ-MnO 2 @Fe-CNF-5% achieves a high salt adsorption of 20 mg/g in CDI device. • The δ-MnO 2 @Fe-CNF-5% has high stability, superior to δ-MnO 2 @CNF. Birnessite-type MnO 2 (δ-MnO 2) nanosheet assembly with various structures were achieved by redox reaction of KMnO 4 under acidic condition with Fe regulation on Fe-doping carbon nanofibers (Fe-CNFs). The Fe-CNFs with various Fe contents were conveniently obtained by carbonization of the electrospun ferric acetylacetonate-polyacrylonitrile (AAI-PAN) fiber with various AAI ratios. X-ray diffraction and transmission electron microscopy demonstrated the formation of δ-MnO 2 on the Fe-CNFs. pHs of KMnO 4 solution and Fe content in the fiber affected the morphology of δ-MnO 2. At pH = 2, the uniform δ-MnO 2 nanosheet assembly was transferred into a tubular structure by adjusting Fe content in the Fe-CNFs template (AAI = 5%, mass ratio). The obtained δ-MnO 2 @Fe-CNF-5% exhibited the highest aspect ratio, large surface area and best charge-transfer behavior. The δ-MnO 2 @Fe-CNF-5% electrode delivered a specific capacitance of 210 F/g (0.3 A/g) and a superior cycling stability with 94% capacitance retention in 4500 cycles. The δ-MnO 2 @Fe-CNF-5%, as a negative electrode presented an excellent performance both in supercapacitor with high energy density (20 Wh/kg) and in capacitive deionization cell with the salt adsorption capacity of 20 mg/g. The unique nanostructure and excellent electrochemical performance render the δ-MnO 2 @Fe-CNF-5% composite as a much promising material for charge storage and deionization applications. [ABSTRACT FROM AUTHOR]

Yarn-shaped supercapacitors with great flexibility are highly anticipated for smart wearable devices. Herein, a device for continuously producing oriented nanofiber yarn based on solution blowing was invented, which was important for the nanofiber yarn electrode to realize mass production. Further, the yarn-shaped supercapacitor was assembled by the yarn electrode with the polypyrrole (PPy) grown on aligned carbon fiber bundles@Polyacrylonitrile nanofibers (CFs@PAN NFs). Electrical conductivity and mechanical properties of the yarn electrode can be improved by the carbon fiber bundles. The specific surface area of the yarn electrode can be enlarged by PPy. The yarn-shaped supercapacitors assembled by the PVA/LiCl/H3PO4 gel electrolyte showed high areal specific capacitance of 353 mF cm−2 at a current density of 0.1 A g−1, and the energy density was 48 μWh cm−2 when the power density was 247 μW cm−2. The supercapacitors also exhibited terrific cycle stability (82% after 20,000 cycles). We also proved that this yarn-shaped supercapacitor could easily power up the light emitting diode. This yarn-shaped supercapacitor was meaningful for the development of the smart wearable devices, especially when combined with clothing or fabrics. [ABSTRACT FROM AUTHOR]

• Porous carbons with tailored graphitization degree and pore size distribution are prepared. • Semi-graphitized microporous carbon shows a balance between capacitance and rate capability. • More than 86.9% of initial capacitance is retained under 100 A g−1. • More than 87.8% of energy density is kept under a high power density of 29.1 kW kg−1. It is extraordinarily valuable to develop the supercapacitor with high capacitance retention under ultra-high current density to meet the requirement of fast charging. Herein, porous carbons with tailored graphitization degree and pore size distribution are facilely prepared via controlling the activation temperature of biomass-derived pyrolytic carbon when employing potassium ferrate (K 2 FeO 4) as catalyst and activation agent. The obtained semi-graphitized microporous carbon with a large specific surface area (2208 m2 g−1), high proportion of large micropores (more than 71.8%) and high conductivity (2.38 S cm−1) exhibits a perfect balance between the charge storage capacity and rate capability, which specific capacitance reaches 254 and 273 F g−1 at a current density of 0.5 A g−1 in KOH and H 2 SO 4 aqueous electrolyte, respectively. Surprising capacitance retention of 86.9% is obtained under an ultra-large current density of 100 A g−1 for the symmetrical supercapacitor based on the semi-graphitized microporous carbon, and no apparent attenuation was observed after 10,000 cycles. Furthermore, energy density of the assembled symmetrical supercapacitor reaches 7.4 Wh kg−1 at a power density of 151.4 W kg−1, and more than 87.8% of energy density is kept even under an ultra-large power density of 29.1 kW kg−1. [ABSTRACT FROM AUTHOR]

[Display omitted] It is a great challenge to design electrode materials with good stability and high specific capacitance for supercapacitors. Herein, a three-dimensional (3D) hydrangea-like NiMoO 4 micro-architecture with Ag nanoparticles anchored on the surface has been designed by adding EDTA-2Na, which was assembled with reduced graphene oxide (rGO) and named as NiMoO 4 -Ag/rGO composite. Benefiting from the synergetic contributions of structural and componential properties, NiMoO 4 -Ag/rGO composite exhibits a high specific capacitance of 566.4 C g−1 at 1 A g−1, and great cycling performance with 90.5% capacitance retention after 1000 cycles at 10 A g−1. The NiMoO 4 -Ag/rGO electrode shows an enhanced cycling stability due to the two-dimensional towards two-dimensional (2D-2D) interface coupling between rGO and NiMoO 4 nanosheets, and the stable 3D hydrangea-like micro-architecture. Moreover, NiMoO 4 -Ag/rGO with 5–15 nm pore structure and enhanced conductivity exhibits improved charge transfer and ions diffusion. Besides, NiMoO 4 -Ag/rGO//AC capacitor displays an outstanding energy density of 40.98 Wh kg−1 at 800 kW kg−1, and an excellent cycling performance with 73.3% capacitance retention at 10 A g−1 after 8000 cycles. The synthesis of NiMoO 4 -Ag/rGO composite can provide an effective strategy to solve the poor electrochemical stability and slow electron/ion transfer of NiMoO 4 material as supercapacitors electrode. [ABSTRACT FROM AUTHOR]

Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks is prepared as electrode material for supercapacitors. AAEMs 1 in rice husks and CO 2 promote the development of pores, which act as pore-forming agent and catalyst respectively. The rice husks carbon is used as the substrate and the SiO 2 in rice husks is converted into Ni–Si compound by loading Ni. The C/NiSi-600-1 shows remarkable electrochemical performance with 237.07 F/g at 0.5 A/g. The performance declines with crystalline SiO 2 formed above 900 °C. A high-performance asymmetric water-system supercapacitor device is fabricated by C/NiSi-600-1 and activated carbon. This device shows capacitance of 142 mF/cm2 at 4 mA/cm2, the energy density of 25.24 Wh/kg at 551.4 W/kg and great cycle stability with 90% after 10,000 cycles. This work provides new insights into the green application of rice husks and promotes the development of electrode materials for supercapacitors. Hierarchically porous rice husks-based nickel-silicon hydroxide composites are prepared by hydrothermal method. Alkali and alkaline earth metals in rice husks and CO 2 promote the development of pores. The SiO 2 anchored on the carbon is converted into Ni-Si compound. The C/NiSi-600-1 shows remarkable electrochemical performance with 237.07 F/g at 0.5 A/g. The C/NiSi-600-1//activated carbon asymmetric supercapacitor device achieves excellent electrochemical performance with energy density of 5.04 m Wh/cm3 at power density of 110.1 mW/cm3 and cycle stability with 90% after 10,000 cycles. [Display omitted] • Hierarchically porous rice husks-based nickel-silicon hydroxide was prepared. • The AAEMs and CO 2 promote the production of hierarchical pores. • The optimal Ni-Si ratio at different carbonization temperature is investigated. • The best temperature is 600 °C, and C/NiSi-600-1 performs 237.07 F/g at 0.5 A/g. • The electrochemical performance declines above 900 °C when crystalline SiO 2 formed. [ABSTRACT FROM AUTHOR]

Porous carbons have recently drawn extensive attention in energy conversion and storage devices. Boosting energy densities of carbon family is still a challenge due to their limited surface area and accessible active sites. In this work, porous carbons with hierarchically structures were prepared from natural Juncus effuses (CJE) and homogeneous MnO 2 layer was successfully incorporated on their surfaces without changing their original porous structure. The CJE/MnO 2 composite showed large specific capacitance (283 F/g at 1 A/g), which was on account of high specific surface area (1283 m2/g) and abundant active sites for pseudocapacitance, particularly, resulted from the introduction of MnO 2. Significantly, the assembled symmetric supercapacitor from CJE/MnO 2 in Na 2 SO 4 aqueous electrolyte delivered high energy/power densities (19.13 Wh/kg at 225 W/kg and 13.73 Wh/kg at 8984 W/kg) and good cyclic performance (86.2% capacitance retention over 5000 cycles at 10.0 A/g). These results demonstrate the CJE/MnO 2 composite can be a potential candidate for supercapacitors. • The surfaces of porous carbons from Juncus effuses are functioned. • Oxygen-containing functional groups facilitate the formation of MnO 2 layer. • Prepared CJE/MnO 2 composites show high specific surface area and capacitance. • The supercapacitor from CJE/MnO 2 delivers excellent energy-power output. [ABSTRACT FROM AUTHOR]

[Display omitted] • The "inner-outer synergistic" strategy for carbon fibers was proposed and successfully demonstrated. • Synchronous realization of the full utilization of the structure and the dual introduction of Faraday capacitance. • Enhanced power density (4004.3 W kg−1) and energy density (31.2 Wh kg−1). Carbon fibers consistently suffer from low specific capacitance due to underutilized structure, severely hindering their application in high-performance supercapacitors. In this work, a novel and scalable "inner-outer synergistic strategy" is developed for superior electrode materials via embedding NiS nanoflakes in electrospun carbon fibers containing NiS nanoparticles (NiS NF /CF@NiS NP). Uniformly sized NiS nanoparticles are encapsulated in the inner region of the carbon fibers as redox active agent, which impart additional Faraday capacitance to the electrode while efficiently avoiding the aggregation of the nanoparticles. Simultaneously, the evenly distributed NiS nanoflakes firmly immobilized on the outer surface of the carbon fibers by the impregnating-sulfurization procedure significantly expand the accessible area of ions and alleviate the volume expansion by preventing stacking. Profiting from the felicitous designed architecture, the NiS NF /CF@NiS NP -3 electrode delivers a reversible specific capacitance of 1691.1F g−1 at 1 A g−1 and remarkable coulombic efficiency of 98.5 %. Furthermore, the hybrid supercapacitor demonstrates a maximum energy density of 31.2 Wh kg−1 and a power density of 4004.3 W kg−1 along with impressive cycling durability of 87.8 % retention for up to 5000 cycles. This demonstrated "inner-outer simultaneous exploitation" engineering provides an appealing and instructive insight for enhanced electrochemical performance of fibrous materials, and can be extended to a variety of energy material systems. [ABSTRACT FROM AUTHOR]

[Display omitted] Realizing both high gravimetric and volumetric specific capacitances (noted as C W and C V , respectively) is an essential prerequisite for the next-generation, high performance supercapacitors. However, the need of electronic/ionic transport for electrochemical reactions causes a "trade-off" between compacted density and capacitance of electrode, thereby impairing gravimetric or volumetric specific capacitances. Herein, we report a high-performance, film-based supercapacitor via a thermal reduction of graphene oxide (GO) in air. The reduced, layer-structured graphene film ensures high electrode density and high electron conductivity, while the hierarchical channels generated from reduction-induced gas releasing process offer sufficient ion transport pathways. Note that the resultant graphene film is employed directly as electrodes without using any additives (binders and conductive agents). As expected, the as-prepared electrodes perform particularly well in both C W (420F g−1) and C V (360F cm−3) at a current density of 0.5 A g−1. Even at an ultrahigh current density of 50 A g−1, C W and C V maintain in 220F g−1 and 189F cm−3, respectively. Furthermore, the corresponding symmetric two-electrode supercapacitor achieves both high gravimetric energy density of 54 W h kg−1 and high gravimetric power density of 1080 W kg−1, corresponding to volumetric energy density of 46 W h L-1 and volumetric power density of 917 W L-1. [ABSTRACT FROM AUTHOR]

Two-dimensional Ti 3 C 2 MXene with high bulk density can act as prospective electrode material to construct high volumetric energy density supercapacitors. Herein, a series of nitrogen-doped Ti 3 C 2 (N-Ti 3 C 2) films are successfully synthesized by adjusting the quantity of urea using a facile solvothermal method. The incorporation of nitrogen atoms can enlarge interlayer spacing and diminish -F terminal groups of Ti 3 C 2 to promote the diffusion and intercalation of electrolyte ions, and bring about defect sites to provide more electrochemical reactive sites, thus improving the specific capacitance of N-Ti 3 C 2. As a result, the 2.0 N-Ti 3 C 2 film shows the highest volumetric capacitance of 2898.5 F cm−3 at scan rate of 2 mV s−1 in 3 M H 2 SO 4 solution, which is mainly attributed to its high pyridinic N content and low -F terminal groups. Density functional theory (DFT) calculations indicate that the doped N atoms have a higher adsorption energy for protons to enhance the pseudocapacitance of 2.0 N-Ti 3 C 2 electrode, and the increased density of states demonstrate the improvement of its electric conductivity after N doping, which promotes the rate performance of 2.0 N-Ti 3 C 2 electrode. The assembled symmetric supercapacitor based on 2.0 N-Ti 3 C 2 film delivers a high volumetric energy density of 40.8 Wh L−1 and good cycling stability. Our work provides an effective and alternative strategy to improve capacitance of other MXenes for high-performance supercapacitors. [Display omitted] • Flexible nitrogen-doped Ti 3 C 2 films are synthesized by a solvothermal method. • Nitrogen atoms can enlarge interlayer spacing and generate defect sites in Ti 3 C 2. • High pyridinic N can act as electron-donors to absorb more electrolyte ions of H+. • Low -F terminal groups are beneficial to enhance pseudocapacitance of N-Ti 3 C 2. • Optimal 2.0 N-Ti 3 C 2 shows a volumetric capacitance of 2898.5 F cm−3 at 2 mV s−1. [ABSTRACT FROM AUTHOR]

Vacancy defects have important impacts on the physical-chemical properties of metal oxides. In the present work, two types of Bi 2 O 3 powders with different morphologies were synthesized for supercapacitor electrodes by calcination (denoted as c-Bi 2 O 3) and two-step hydrothermal methods (donated as h-Bi 2 O 3). Vacancy clusters of V B i ‴ V O · · V B i ‴ with different concentrations were observed in these two samples by positron annihilation lifetime spectroscopy. The results of electrochemistry revealed that the charge storage behavior of h-Bi 2 O 3 with more V B i ‴ V O · · V B i ‴ defects obeyed both semi-infinite diffusion-controlled battery-type mechanism and surface-controlled pseudo-capacitance mechanism, while that of the calcined c-Bi 2 O 3 electrode with a lower concentration of V B i ‴ V O · · V B i ‴ defects followed only the semi-infinite diffusion-controlled battery-type mechanism. The pseudo-capacitance of h-Bi 2 O 3 could be attributed to the insertion/extraction process of more K+ ions in the V B i ‴ V O · · V B i ‴ surface defects. Due to the partial pseudo-capacitance and improved conductivity caused by more V B i ‴ V O · · V B i ‴ defects, the h-Bi 2 O 3 electrode had a larger capacitance (1043 F g-1 at 1 A g-1), a higher rate performance (560 F g-1 at 60 A g-1), and better cycle stability (93% retention at 50 A g-1 after 2000 cycles). Furthermore, because of the high-concentration of V B i ‴ V O · · V B i ‴ defects, the Ni/Co-MOF//h-Bi 2 O 3 asymmetric supercapacitor delivered a relatively higher specific energy density of 47 Wh kg-1 at 1125 W kg-1. Taken together, these results indicate that surface vacancy clusters play an important role in boosting the electrochemical performance of metal oxide electrodes. [ABSTRACT FROM AUTHOR]

A composite containing self-assembled MoO 2 nanoparticles and functional carbon nanosheets was obtained via a facile and controllable strategy. Two-dimensional functional carbon nanosheets as matrices have close contact with MoO 2 nanoparticles, which assists in the improvement of electronic conductivity, provides efficient pathways and accelerates electron transfer. The carbon nanosheets have functional groups on the surface, which could serve as the nucleation sites for MoO 2. The MC-0.12 composite shows optimal specific capacitance (190.9 F g-1 at 1 A g-1) and excellent cycle stability between monomers and composites with different constituents. The assembled symmetrical coin cell supercapacitor using MC-0.12 possesses the maximum energy density of 10.3 Wh kg-1 at a power density of 378 W kg-1 and still maintains the energy density of 7.9 Wh kg-1 at 1682 W kg-1 with a larger potential window. The capacitance retention (92%) of the assembled device is maintained after 2000 cycles, showing outstanding cycle life. Therefore, the integration of self-assembled MoO 2 nanoparticles with 2D functional carbon nanosheets provides the composite superior electrochemical performance for supercapacitor applications. [ABSTRACT FROM AUTHOR]

In this work, it was presented to prepare N, S co-doped porous carbons derived from Juncus effuses (NSPC) by carbonization, KOH activation, and heteroatoms doping using thiourea as dopant. Microstructures and physicochemical properties of the obtained carbon samples were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), adsorption/desorption of nitrogen (BET), X-ray diffraction (XRD), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and electrochemical workstation. The NSPC showed outstanding electrochemical performance because of hierarchical porous structures and N, S co-doping. The specific capacitance of the NSPC was 233 F/g at 0.5 A/g, and the capacitance retention reaches 82% for the current density up to 10 A/g, showing a good rate capability. Moreover, symmetric supercapacitor assembled from NSPC revealed high energy density of 15.97 Wh/kg at 500 W/kg. The capacitance of the NSPC still kept about 97% after 5000 cycles at 1.0 A/g. These results confirm that the NSPC is a potential material for high performance supercapacitors. Unlabelled Image • Hierarchical porous carbons were derived from Juncus effuses. • Thiourea was successfully used for one-step N, S co-doping in porous carbons. • The supercapacitor from NSPC delivers excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

The synergetic combination of double-layer capacitor carbon nanosheets and pseudocapacitive CuO particles with enhanced electrochemical properties had been proposed. Herein, CuO/carbon nanosheets electrode material with outstanding electrochemistry performance was successfully synthesized via a low-cost and controllable strategy. Such rational architecture integrates high-conductivity carbon nanosheets with rich-chemical-activity CuO particles. The surface-functional carbon nanosheets serve as a conductive substrate, provide an efficient pathway and accelerate the fast diffusion of electrons. This electrode material depicts high specific capacitance up to 183.9 and 371.1 F g−1 at 1 A g−1 in Na 2 SO 4 and KOH electrolyte using three-electrode tests, respectively. Moreover, two symmetric devices using this CuO/carbon nanosheets electrode material were assembled with different electrolytes. The as-fabricated device with KOH electrolyte delivers remarkable energy density of 19.36 W h kg−1 at power density of 355.6 W kg−1 and still maintains 12.06 W h kg−1 at 1750.7 W kg−1. The as-fabricated device with Na 2 SO 4 electrolyte achieves the maximum energy density of 12.46 W h kg−1 at 355.6 W kg−1. The capacitance retention rate is maintained at 94.4% after 2000 cycles in the as-fabricated coin cell supercapacitor with Na 2 SO 4 electrolyte, showing outstanding long-cycling life. Herein, the strategic integration of CuO particles with two-dimensional functional carbon nanosheets as the electrode material provides superior electrochemical performance for supercapacitors. [ABSTRACT FROM AUTHOR]

Metallic 1T MoS2 greatly benefits the supercapacitance of MoS2 due to its considerably higher conductivity as compared to semiconducting 2H MoS2. Alkali metals, such as Li, Na and K, are always used to prepare 1T MoS2 through intercalation of alkali metal ions into the interlayer of 2H MoS2. Nevertheless, the influences of the alkali-earth metals as the guest in the interlayer of MoS2 on its structure and electrochemical capacitor performance are rarely investigated. Herein, we introduced hydrated Mg ions as the guest into MoS2 nanosheets. The interlayer spacing was increased to 1.144 nm after the introduction of hydrated Mg ions, larger than that of the pristine MoS2 (0.620 nm) and restacking MoS2 (0.626 nm). The enlarged interlayer spacing can accommodate more ions during intercalation process. Moreover, the 1T phase concentration after the introduction of hydrated Mg ions was as high as ~ 90%, which benefits the charge transfer during the charging/discharging processes. Consequently, the specific capacitance of the MoS2 with Mg guest ions as well as the energy densities and power densities was greatly improved as compared to those of the restacking MoS2 or pristine MoS2 counterparts. The present work not only demonstrated a new strategy for engineering the physical properties and improving the electrochemical performance of MoS2 supercapacitor electrode through pre-intercalation of alkali-earth metal ions in the interlayer of MoS2, but also has directive significance for the design of other layered electrode materials for energy storage systems. [ABSTRACT FROM AUTHOR]

• The hierarchical M-ZCOH/NPG/NF heterostructures were successfully constructed. • The BIEF in the heterointerface enhanced electronic/ionic transport dynamics. • A high capacity reaching ∼1247.1C g−1 (∼2771.3 F g−1) at 1 A g−1 was obtained. • The HSC displayed ultrahigh energy density of ∼78.3 Wh kg−1 at ∼800 W kg−1. The superior electronic/ionic transport dynamics of electrode materials have been crucial to achieve appealing high performance for supercapacitors. Herein, a fascinating one-dimensional (1D) zinc cobalt hydroxide nanobelts/0D irregular manganese dioxide nanoparticles (M-ZCOH) have been vertically loaded into the 3D Ni foam (NF) substrate wrapped by nitrogen-doped graphene (NPG) (M-ZCOH/NPG/NF) for supercapacitors. The ingeniously designed M-ZCOH/NPG/NF composites feature powerful built-in electric field (BIEF) introduced by well-defined heterointerface with abundant oxygen vacancies defects. The formed electron accumulation triggering strong interfacial interaction verified by the differential charge density analysis may endow M-ZCOH/NPG/NF with the extra driving force to increase the diffusion/adsorption of electrolyte ions, thereby facilitating electron/ion transfer kinetics. Also, the qualitative negative shift of the d band center for M-ZCOH composites further evidences a lower electron/ion transfer barrier compared with the monomers. Obviously, the penetrating understanding of heterointerface on the improved properties is manifestly interpreted by combining theoretical and experimental analysis. Moreover, the ingenious strategy of engineering the heterointerfaces in unique heterostructure with rich defects may provide a new prospect for optimizing other advanced materials in sustainable energy storage systems. [ABSTRACT FROM AUTHOR]

We have prepared the CoMoO 4 nanorods (NR) electrode with a specific capacitance (89.5 F g − 1 ) at a current density of 1 mA cm −2 . Moreover, the asymmetric supercapacitor (ASC) has been fabricated by using CoMoO 4 NR as positive electrode and activated carbon (AC) as negative electrode. At a power density of 80 mW cm −3 , the ASC can deliver an energy density of 0.226 mW h cm −3 in the voltage range of 0–1.6 V. In addition, the CoMoO 4 NR-based ASC device still remains a high energy density (84.07%) after 5000 cycles, demonstrating that one-dimensional nanostructures could be promising to achieve the high-energy-density materials. [ABSTRACT FROM AUTHOR]

The Mo-doped NiS/rGO composite was obtained by vulcanization of NiMoO 4 and morphology adjustment by GO. A nanosheet-like structure was demonstrated in the composite, which was assembled by double-phase Mo-doped NiS (Mo-NiS) nanodots loading on reduced graphene oxide (rGO) nanosheets. The doping of Mo and the resultant synergistic effect between Mo and Ni can offer the bimetallic sulfide of Mo-NiS with higher capacity output and enhanced cycle stability. The surface oxygen-containing functional groups of GO provide abundant nucleation centers for the uniform loading of Mo-NiS nanodot during synthesis, and the resultant rGO sheets in the final composite ensures continuous electron transport and promoted ionic exchange for Mo-NiS. Besides, the Mo-NiS nanoparticles loaded on the surface of rGO can also inhibit its stacking and form a highly integrated composite structure. The synergistic effect of Mo-doping, double-phase NiS and conductive rGO substrates attributed to the high specific capacity output (1664.7 C g−1 at 1 A g−1), long cycle life and excellent rate performance in the final composite. The Mo-NiS/rGO composite was also applied as a battery-type electrode in asymmetric supercapacitors (ASCs), which showed acceptable performance for potential practicability, including attractable energy densities and power densities, as well as impressive cyclic ability with large capacity retention of 90.3% in 7000 cycles. Graphical Abstract [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A nitrilotriacetic acid-assisted strategy for controllable synthesis of NiS/carbon hexahedrons was proposed. • Synchronous realization of the combination of carbon with NiS and morphology controlled in one step. • Formation mechanism and determinants of NiS/carbon composites are revealed. • Enhanced power density (4187.2 W kg−1) and energy density (30.8 Wh kg−1). Effective adjustment of structure and morphology is considered to be an available strategy to improve the energy storage performance of supercapacitor electrode materials. Herein, a series of hierarchical NiS/carbon hexahedrons consist of self-assembling nanoplates or nanorods were synthesized via nitrilotriacetic acid (NTA)-assisted hydrothermal strategy. This study demonstrates that the micro-morphology of the unit structure constituting the hexahedrons can be controlled by adjusting the concentration of NTA. Benefiting from synergetic effect of high void space, hierarchical assembly mode and integrated composite structure, NiS/carbon hexahedrons promote adequate exposure of abundant active sites and enhance the structural stability, donating superior energy storage performance. As expected, the optimized NiS/carbon electrode (NiS/NTA-2) exhibits superb capacitive performance, including excellent specific capacitance of 1530.4 F g−1 at 1.0 A g−1 and remarkable cycle stability with 85.6% after 5000 cycles. Employing the as-prepared NiS/NTA-2 composites as positive electrode, the hybrid supercapacitor device with spectacular capacity of maximum energy density and power density up to 35.1 Wh kg−1 and 4509.3 W kg−1 and impressive long-term stability of 87.2% retention after 5000 cycles is assembled. Moreover, a light-emitting diode (LED) is successfully illuminated for up to 12 min by two devices connected in series. Based on this strategy, high-performance energy storage devices can be further developed through utilizing the modulation effect of metal complexes to design morphology controlled electrode materials. [ABSTRACT FROM AUTHOR]

To well satisfy the newly emerging personalized electronics, it is urgent to develop durable and reliable flexible energy storage devices having a favorable match with them. However, conventional polymer matrixs based hydrogel electrolytes inevitably limit the development of desired supercapacitors due to their poor stretchable, healable as well as electrochemical properties. Here, a novel multifunctional hydrogel polyelectrolyte (VHSNPs-PAA/H 2 SO 4 /ARS) is developed comprising the alizarin red S (ARS) redox mediator and the double cross-linked polyacrylic acid (PAA) by the vinyl hybrid silica nanoparticles (VHSNPs) and hydrogen bonds, which realized the combination of ultrahigh stretchability (~2400% strain), robust mechanical toughness (lift up the 500 g weights), favorable self-healability (~92% efficiency during 10 cutting/healing cycles), high ionic conductivity (33 mS cm−1), powerful self-adhesiveness and superior redox activity within a single hydrogel structure. The facilely fabricated carbon-based supercapacitor using the obtained hrdrogel as the electrolyte can achieve large electrode specific capacitance of 248 F g−1 and high mass energy density of 16.7 W h kg−1, which are much larger than the recently reported stretchable and self-healing hydrogel electrolytes based flexible supercapacitors. Meanwhile, as-fabricated device also exhibits the excellent cycling stability and superior durability against physical deformation after 5000 charge-discharge cycles and 200 bending-releasing cycles, respectively. Image 1 • A novel multifunctional hydrogel (VHSNPs-PAA/H 2 SO 4 /ARS) is designed and prepared. • The hydrogel possesses 3D network structure and high ionic conductivity of 33 mS cm−1. • The hydrogel demonstrates outstanding stretchability, self-healability, and redox activity. • As-fabricated supercapacitor exhibits high energy density and superior durability. [ABSTRACT FROM AUTHOR]

Large micropore with a pore size of 1–2 nm can allow high charge storage capability while ensure fast ions transport, which serves to improve the energy density of supercapacitors without sacrificing high power density. Herein, we report a large micropore dominant microporous carbon derived from a biomass waste, flaxseed residue from the edible oil industry, for high-performance supercapacitors. The reported material exhibits a large specific surface area of up to 3230 m2 g−1, and more than 70.1% of micropore volume is contributed by large micropores. The specific capacitance of the obtained material reaches up to 369 and 398 F g−1 in KOH and H 2 SO 4 electrolyte, respectively. Meanwhile, the assembled supercapacitor device based on the obtained material exhibits excellent rate and cycle performance. Over 92.7% of the initial capacitance is retained even under a large current density of 20 A g−1 and the capacitance retention is more than 98.1% after 10000 times cycle in KOH electrolyte. The energy density of the assembled supercapacitor device reaches 61.2 Wh kg−1 at a power density of 468.8 W kg−1, and a high energy density of 43.5 Wh kg−1 is retained at a large power density of 13.3 kW kg−1 in ionic liquid EMIMBF 4 electrolyte. Image 1 • A large micropore (1 nm < d < 2 nm) dominant microporous carbon was reported. • More than 70.1% of micropore volume is contributed by the large micropores. • Specific capacitance reaches 369 and 398 F g−1 in KOH and H 2 SO 4 electrolyte. • Excellent rate and cycle performance are observed. • A high energy density of 61.2 Wh kg−1 is observed in ionic liquid. [ABSTRACT FROM AUTHOR]

Pomelo peel is a popular biomass material that is eco-friendly and widely distributed worldwide. However, a large amount of pomelo peel is directly discarded instead of being utilized. This study synthesizes nitrogen/sulfur dual-doped porous carbon materials using pomelo peel and ammonium persulfate, followed by potassium hydroxide (KOH) activation at 600 °C, which is lower than most average activation temperature. The as-obtained products are electrode materials applied in supercapacitors. Results indicate that the as-prepared nitrogen/sulfur dual-doped porous carbon material (NSC-600) has high nitrogen (5.89%) and sulfur (0.46%) contents, and a large surface area (1193 m2 g−1). As the current density is 0.5 A g−1, the specific capacitance of the NSC-600 material up to 310 F g−1. After 10,000 cycles, the capacity retention is approximately 98.8% at a current density of 2 A g−1 in 6 M KOH, which indicates outstanding cycling performance. Moreover, the assembled symmetric electrochemical capacitor exhibits a high energy density of 21.4 Wh kg−1 at a power density of 259.9 W kg−1. Therefore, the nitrogen/sulfur dual-doped porous carbon materials synthesized at comparatively low temperatures exhibit promising applications in superior-performance supercapacitors. • Porous carbon materials are synthesized at 600 °C, which is lower than most average activation temperatures. • Porous carbon materials have high nitrogen (5.89%) and sulfur (0.46%) contents. • The carbon source of the materials is pomelo peel. • Outstanding cycling performance of 98.8% is retained after 10,000 cycles at a current density of 2 A g−1. • The NSC-600 material achieves a large surface area of 1193 m2 g−1 at 600 °C. [ABSTRACT FROM AUTHOR]