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Doping and compositing are considered to be the effective strategies for improving the performance of supercapacitor electrode materials. In this work, the Al 2 O 3 -doped Co 3 O 4 /graphene nanocomposites (denoted as ACGC) were successfully fabricated by a combination method of hydrothermal and calcination. The phase, composition and morphology of fabricated nanocomposites were characterized via using XRD, XPS, TEM, and SEM, and the electrochemical behavior were examined via CV, GCD, EIS. The results showed that the nanocomposites had more specific capacitance (968 F/g) than that of Al 2 O 3 -doped Co 3 O 4 nanocomposites (denoted as ACC) (682 F/g) and pure Co 3 O 4 (295 F/g), respectively. Moreover, it had good capacitance retention of 96.9% after 2000 cycles at a high current density of 10 A/g. In addition, an asymmetric supercapacitor (ASC) assembled by ACGC and commercial activated carbon (AC) can provide a specific capacitance of 106 F/g at 0.5 A/g and 84.2% capacitance retention after 5000 cycles at 10 A/g. And it is worth noting that this ASC can provide a maximum energy density of 40.1 Wh/kg and power density of 8285.9 W/kg. Significantly, two ASCs in series can light a red light-emitting diode (LED) (2.2 V) for 200 s and a blue LED (3.2 V). Unlabelled Image • The Al 2 O 3 -doped Co 3 O 4 /graphene nanocomposites (ACGC) were successfully fabricated. • The ACGC showed more specific capacitance (968 F/g) than that of Al 2 O 3 -doped Co 3 O 4 (682 F/g) and Co 3 O 4 (295 F/g) at 1 A/g. • The ASC assembled by ACGC and AC can provide a maximum energy and power density of 40.1 Wh/kg and 8285.9 W/kg. • Two ASCs in series can light a red LED (2.2 V) for 200 s and a blue LED (3.2 V). [ABSTRACT FROM AUTHOR]

Novel NiFe 2 O 4 @NiCo 2 O 4 Mott-Schottky heterostructure was constituted with one-pot hydrothermal route. The designed Mott-Schottky heterojunction created strong interfacial interaction and resulted high charges transfer abilities by reducing the energy barriers for redox reactions to realize effective pseudocapacitive energy storage. [Display omitted] • NiFe 2 O 4 @NiCo 2 O 4 Hybrid composite was synthesized via one-pot hydrothermal. • Hollow algae-like microspheres with plenty nanowires were successfully designed. • The Mott-Schottky junction generated powerful interfacial interaction with high charges transfer abilities. • NiFe 2 O 4 @NiCo 2 O 4 based supercapacitor displayed advanced electrochemical performances. Designing hybrid structure of transition metal oxides (TMOs) with controlled morphology can adjust the electronic structure and create more kinetics reactions. Herein, a new kind of NiFe 2 O 4 @NiCo 2 O 4 nanocomposite was synthesized with one pot hydrothermal route. The unique hollow algae-like microspheres with plenty nanowires and the synergistic effect factors promote high electroactive sites and generate a built-in electric field. The constituted Mott-Schottky heterostructure creates strong interfacial interaction, paves the way for the electrolyte ions diffusion and results high charges transfer abilities by reducing the energy barriers in the heterointerfaces. As cathode material, the NiFe 2 O 4 @NiCo 2 O 4 presents satisfactory specific capacity of 996C·g−1 at 0.5 A·g−1 and maintains ultrahigh capacity retention of 81 % at 30 A·g−1 with marvellous stability of only 6 % loss during 20,000 cycles. Interestingly, asymmetric hybrid supercapacitor device based NiFe 2 O 4 @NiCo 2 O 4 //active carbon (AC) provides tremendous energy density of 117.6 Wh·kg−1 at 438 W·kg−1 power density. What's more, all-solid-state device offers ultra-low self-discharge process of 9.5 % through 24 h. Therefore, the combination of NiFe 2 O 4 @NiCo 2 O 4 to form Mott-Schottky heterojunction was a promising strategy to develop electrode material with high energy storage performance. [ABSTRACT FROM AUTHOR]

Ternary layered double hydroxide (LDH) are potential electrode material choices for supercapacitors (SCs) due to their various oxidation states and high theoretical specific capacitance. In this paper, FeCoNi-LDH composite with cross-braided flowers of nanoneedles has been prepared by a single-step hydrothermal method. By highlighting the structural and morphological advantages, the obtained ternary LDH shows lower resistivity in comparison with the binary LDH. As electrode material, the ternary LDH exhibits excellent electrochemical properties, such as superb specific capacitance of 2163.3 F·g−1 at 0.5 A·g−1 and good cycle retention rate of 93.8% after 5000 cycles at 20 A·g−1. Meanwhile, the assembled asymmetric flexible solid-state supercapacitor device can provide 44.8 Wh·kg−1 energy density at 807.5 W·kg−1. Moreover, two devices in series can also light up miniature light bulbs of different hues and maintain them for a long period when they are connected in series. • FeCoNi LDH with unique structure is prepared by one step hydrothermal method. • The unique structure LDH has open-channel nanonetworks for fast charge transport. • FeCoNi-LDH shows excellent properties as electrode material of supercapacitor. [ABSTRACT FROM AUTHOR]

Efficient and novel cobalt doped MnO 2 nanowires decorated with Graphene oxide was successfully synthesized with hydrothermal method and ultrasonic process. The nanocomposite phase was confirmed by XRD and XPS data. TEM and HRTEM analysis showed the good dispersion of MnO 2 nanowires on graphene oxide sheets. Benefiting from the synergistic effect between cobalt-doped MnO 2 nanowires and graphene oxide, the electrode material showed a satisfactory electrochemical performance with high specific capacitance of 397 F g−1 at 0.5 A g−1, high rate capability (328 F g−1 at 20 A g−1), and excellent capacitance retention only 2.5% decay after 4000 cycles at 10 A g−1 current density. As application for asymmetric supercapacitor device, the Cobalt doped MnO 2 decorated with graphene oxide (MCo(0.25)/GO) electrode achieved a wide potential window up to 2.3 V with a high energy density of 35.3 Wh·kg−1 at power density of 590 W kg−1. Moreover, an energy density value of 25.8 Wh·kg−1 is maintained at high power density (5.6 kW kg−1). Therefore, the prepared MCo(0.25)/GO nanocomposite, with outstanding electrochemical performance, is considered as suitable and great potential application for supercapacitor device in the next generation. Image 1 • MCo(0.25)/GO nanocomposite was prepared by hydrothermal and ultrasonic way. • The nanocomposite exhibited a high specific capacitance and high rate capability. • An energy density of 35.3 Wh·Kg−1 was achieved at a potential window of 2.3 V. [ABSTRACT FROM AUTHOR]

The choice of an activator and activation method is crucial to the preparation of high-quality activated carbon. Herein, inspired by a foaming strategy, we selected KMnO 4 as activator, and hierarchical porous framework carbon material was prepared via lily powder being fully foamed and activated in the KMnO 4 hot solution. The Lily-derived Porous Carbon Material (LPCM) possesses the characteristics of in-situ co-doping of N and O. The maximum specific surface area of the obtained sample was 1852.5 m2g-1, and the corresponding total pore volume was 1.11 cm3g-1. Due to the interconnected hierarchical pore network structure and rich O (13.16 at%) & N (3.31 at%) contents, at 600 °C, the specific capacitance of the LPCM was 352 F g−1 at 0.5 A g1 and the cycling reliability was 100% after 10,000 charges and discharges. In addition, the voltage window of All-solid-state Symmetric Flexible Supercapacitor (ASFS) fabricated with PVA-KOH gel electrolyte was 1.4 V. And the fabricated ASFS device had energy density of 23.82 Wh kg−1 at 700 W kg−1. At the same time, two ASFSs in series could light up a small red bulb and maintained for more than 6 min. N, O co-doped porous activated carbon material was prepared by KMnO 4 as a foaming agent and activation reagent. The porous carbon material prepared exhibited superior specific capacitance (352 F g−1 at 0.5 A g−1) and cycle properties (100% after 10,000 charges and discharges). The voltage window was expanded to 1.4 V by PVA-KOH as a solid electrolyte, and had a large energy density (23.82 Wh kg−1) and power density (at 700 W kg−1). Two ASFSs in series could light up a small red bulb and maintained for more than 6 min. [Display omitted] • N/O co-doped porous carbon was prepared from Lily as biomass carbon materials. • KMnO 4 was used as an activator and foaming reagent for high-starch lily. • The porous carbon exhibited superior specific capacitance 352 F g−1 at 0.5 A g−1. • The porous carbon displayed 100% cycle stability after 10,000 charges and discharges. • The voltage window was expanded to 1.4 V by PVA-KOH as a solid electrolyte. [ABSTRACT FROM AUTHOR]

• Five Basic Carbonate Composites with different morphologies were obtained. • Just by adjusting the element Co:Ni ratio, the composite has excellent performance. • The sample Co1Ni1 exhibited specific capacitance of 1682 F g−1 at 1 A g−1. • The prepared ASC has good flexibility and charge & discharge performance. [Display omitted] Under the high current density, high cyclability and good rate performance are two major challenges for the applications of supercapacitor. How to control the composition and structure of the electrode materials is the key factor to solve these two problems. In this work, the controllable morphology Co/Ni Basic Carbonate Composites (CNBCC) were synthesized by one-step hydrothermal regulating the ratio of Co to Ni. Impressively, benefiting to its special sea urchin structure, the composite with the 1:1 ratio of Co to Ni exhibited remarkable electrochemical performance with specific capacitance (at 1 A g−1, 1682 F g−1), superior rate capability (at 1–30 A g−1, 79.3%) and cycling stability (2000 cycles, 96%). Further, a solid-state asymmetric supercapacitor Co1Ni1//AC (ASC) was constructed with a high voltage window (1.7 V). The ASC displayed a high energy density of 42.5 Wh kg−1 at power density 849.7 W kg−1, while still remained at 20.6 Wh kg−1 at a power density of 25511 W kg−1. In addition, the ASC had good flexibility, and their CV curves hardly changed after being bent into different angles; the two ASC in series could light a yellow LED for 25 min. [ABSTRACT FROM AUTHOR]

Plant-based carbon materials have been used for electrode materials of supercapacitor due to their low price and developed pore structure. In this work, a kind of Activated Carbon derived from Barbary Figs Husk (ACBFH) was prepared by direct carbonization followed by KOH activation. TEM and BET analysis showed that the obtained ACBFH at 700 °C had the well hierarchical structure with uniform micropores and mesopores distribution. Due to the hetero-atom doping (N and O) and high specific surface area (1480 m2·g−1), the specific capacitance of the ACBFH electrode reached up to 497 F·g−1 in three electrode configuration with excellent capacitance retention of 96.5% after 10,000 cycles. Furthermore, all-solid-state symmetric ACBFH700//ACBFH700 device exhibited superb energy density value of 35.8 Wh·kg−1 at power density of 478.6 W·kg−1. Importantly, two symmetric devices in series could light yellow and blue LEDs for 16 and 8 mins, respectively. Therefore, the ACBFH opened the way for supercapacitor device with an efficient and sustainable electrode material in energy storage devices. [Display omitted] • Hierarchical porous carbon material derived from Barbary figs husk was synthesized. • The ACBFH700 sample exhibited ultrahigh specific capacitance and superb rate capability. • All solid-state symmetric device delivered ultrahigh energy density of 35.8 Wh.kg−1 in PVA/KOH gel electrolyte. • Two assembled all solid-state supercapacitor devices in series illuminated yellow and blue LEDs. [ABSTRACT FROM AUTHOR]