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Biomass carbon materials, which are environmentally friendly, have received significant attention and rapidly developed in the field of electrochemical devices. In this study, rice husk carbon (RHC) was prepared using calcination and activation methods, and a layer of nickel–cobalt double hydroxide (NiCo-LDH) was grown on the surface of RHC using a hydrothermal method, resulting in the formation of the NiCo-LDH@RHC composite. The open nanoflower structure and the synergistic effect between RHC and NiCo-LDH increased the conductivity and stability of the electrode material, as well as its specific capacitance. The NiCo-LDH@RHC electrode delivered a high specific capacity of 8542.5 mF cm−2 at a current density of 2 mA cm−2 with a good cycling stability of 80.45% across 5000 cycles. Furthermore, a high-performance all-solid-state asymmetric supercapacitor (ASC) was assembled using Fe2O3/CC as the anode material and NiCo-LDH@RHC as the cathode material. It displayed a high energy density of 61.44 μW h cm−2 at a power density of 3.99 mW cm−2 and an excellent cycle retention rate of 86.54% after 10 000 cycles. This research demonstrates that NiCo-LDH@RHC is an environmentally friendly and high performance electrode material with great development potential. [ABSTRACT FROM AUTHOR]

Zn-ion hybrid supercapacitors (ZSC) have shown great potential as energy storage devices as they incorporate the merits of rechargeable batteries and supercapacitors. However, the poor bendability, unsatisfied energy density and cycling stability are still challenging the practical application of ZSC. Herein, Zn-doped MnO 2 nanowires (Zn-MnO 2) binder-free cathodes is synthesized with the aid of a one-step hydrothermal approach, which improves the lattice distortion caused by Zn hydrate ions and provided rich ion transport path. The Zn-MnO 2 cathode was assembled with the active carbon (AC) anode into an axial ZSC, achieving a surface capacitance of 1300 mF cm−2 and an energy density of 722.2 μWh cm−2 at power density of 1.99 mW cm−2. After 20,000 charge/discharge cycles, a capacity retention rate of 83.75% and a coulombic efficiency of 100% were achieved, indicating excellent cycle stability of present device. In addition, this axial ZSC reveals exquisite mechanical flexibility and electrochemical stability, enabling continuously power smartphones under bending conditions. Present work suggests that ZSC devices based on Zn-MnO 2 have excellent doable for business energy storage devices. • A axial ZSC was designed with Zn-doped MnO 2 cathode and carbon material anode. • The axial structure improves the flexibility and stability of the ZSC device. • The ZSC device displays high energy density (722.2 μWh cm−2). • The fiber-type device can be applied as wearable bracelet power supply device. [ABSTRACT FROM AUTHOR]

Porous NiCo2S4 networks have been successfully synthesized by a facile one-pot solvothermal method without the use of any surfactant or template. Crystal structure, morphology, composition and surface area of the as-synthesized samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy and Brunauer-Emmet-Teller techniques. Owing to their porous nature and small crystalline size, the as-prepared NiCo2S4 networks based supercapacitor electrodes showed a high specific capacitance of 1250Fg at 1Ag, and excellent cycling stability with the retention capacity of 70.3% after 5000 cycles in the KOH aqueous solution electrolyte. Porous NiCo2S4 networks have been successfully synthesized by a facile one-pot solvothermal method, without the use of any surfactant or template. Owing to their porous nature and small crystalline size, the as-prepared NiCo2S4 networks-based supercapacitor electrodes showed a high specific capacitance of 1250Fg at 1Ag, and excellent cycling stability with the retention capacity of 70.3% after 5000 cycles in the KOH aqueous solution electrolyte. [ABSTRACT FROM AUTHOR]

To meet the higher requirements for green energy, high-performance renewable energy technology based on earth‑abundant materials is essential. Aqueous zinc-ion hybrid supercapacitors (ZSC) have been regarded as an attractive candidate for sustainable electrochemical energy storage device combining the advantages of batteries and supercapacitors, but their unsatisfactory cycling stability and low energy density remain a problem to be solved. Herein, nitrogen-doped MnO 2 (N-MnO 2) nanowalls were synthesized by in situ deposition, which provides rich ion transport pathway and accelerates the extraction/insertion of zinc ions. As a result, N-MnO 2 anode can be assembled to an aqueous zinc-ion hybrid capacitor with AC cathodes, presenting a high energy density of 712.5 μWh cm−2 at a power density of 1000 μW cm−2 (1 mA cm−2) and excellent cycle stability with a capacity retention rate of 92.9 % in 25,000 charge-discharge cycles. In addition, the flexible hybrid supercapacitor exhibits excellent mechanical flexibility, and the electrochemical performance remains stable under different bending angles. This work shows that ZSC device based on N-MnO 2 nanowalls hold great potential for new energy storage devices. • Preparation of nitrogen-doped MnO2 and commercial activated carbon as electrodes for flexible zinc-ion hybrid capacitors. • The multi-layer sandwich structure improves the flexibility and stability of the asymmetric supercapacitor. • The designed N-doped MnO2 has a capacity retention rate of 92.9 % after 25,000 times of continuous charge and discharge. • The device exhibits good performances in flexibility , showing the potential of wearable energy storage devices. [ABSTRACT FROM AUTHOR]