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Hematite (α-Fe 2 O 3) is considered a promising electrode material due to its cost-effectiveness and high theoretical specific capacity. In this paper, we prepared Fe 2 O 3 nanoparticles by hydrothermal method. To improve the drawbacks such as poor conductivity and low practical capacity, NiCo 2 O 4 nanorods and graphene oxide (rGO) are added to Fe 2 O 3 nanoparticles. The composite exhibits a specific capacity of 644 F g−1 at a current density of 1 A g−1. The higher ion diffusion rate can improve the specific capacity and energy density in optimized composites. At a current density of 1 A g−1, compared to Fe 2 O 3 , the specific capacity and energy density of Fe 2 O 3 /NiCo 2 O 4 /rGO were increased by 278.8 % and 304.5 %, respectively. In order to stimulate more potential applications, we encapsulated Fe 2 O 3 /NiCo 2 O 4 /rGO-//Co 3 O 4 asymmetric supercapacitors with binder-free Co 3 O 4 as the counter electrode. Determining the optimal positive and negative active substance mass ratio by controlling the amount of charge, the device can deliver a high specific capacity of 280.6 F g−1 at a current density of 1 A g−1 and power density of 354.8 W Kg−1 while providing a high energy density of 56.1 Wh Kg−1. These results indicate that Fe 2 O 3 /NiCo 2 O 4 /rGO has potential for electrochemical energy storage, which could provide new ideas for new commercial supercapacitors. [ABSTRACT FROM AUTHOR]

The emerging field of wearable electronic devices has propelled the demand for advanced energy storage solutions. Among these, wearable supercapacitors have garnered significant attention due to their intrinsic advantages, including high stability, rapid charging discharging capabilities, and cost-effectiveness. This paper unveils the latest strides in flexible and wearable supercapacitors, placing a spotlight on the exceptional performance of a novel V 2 O 5 -pBOA-Graphene nanocomposite. Synthesized through a straightforward chemical approach, the material is meticulously characterized using X-ray diffraction, scanning electron microscopy, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The electrochemical behavior of the fabricated wearable supercapacitor devices is scrutinized, revealing an outstanding specific capacitance of 986 Fg−1 in a two-electrode system, coupled with an impressive energy density of 49 Whkg−1. The nanocomposite's robust cycling stability is showcased, with a capacitance retention of 93.47 % over 2000 cycles. Moreover, the device's flexibility is assessed by bending it at various angles, and it retains more than 91 % capacitance even at a 90° angle, underscoring its suitability for wearable applications. The choice of electrode materials, encompassing vanadium pentoxide (V 2 O 5), poly benzoxazole aniline (pBOA), and graphene, synergistically contributes to the nanocomposite's remarkable electrochemical performance. V 2 O 5 , with its pseudocapacitive behavior, is complemented by the conductivity and mechanical stability offered by pBOA and graphene. The ternary V 2 O 5 -pBOA-Graphene nanocomposite emerges as a frontrunner for wearable supercapacitor applications, promising enhanced flexibility, efficiency, and practical utility in real-world scenarios. The findings underscore the potential of the V 2 O 5 -pBOA-Graphene nanocomposite as a key player in the future of wearable energy storage, opening avenues for further exploration, optimization, and integration into practical applications. [ABSTRACT FROM AUTHOR]

The accurate estimation of state-of-charge (SOC) is crucial for the supercapacitor (SC) management system of electric vehicles. In this paper, a salp swarm algorithm (SSA)-optimized high and low degree cubature Kalman filters (CKFs) for SC SOC estimation is proposed. Firstly, the key parameters are identified for the Thevenin model by SSA under SC test data. Secondly, a temperature-varied model with temperature uncertainty is constructed by polynomial fitting. Thirdly, an adaptive rule based on SSA is designed to regulate the noise covariance matrix information in real time. Combining this rule and CKFs, SSA-based generalized high-degree CKF (SSA-GHCKF) and SSA-based low-degree CKF (SSA-CKF) are developed with the minimum prediction error as the objective. Finally, the effectiveness of improved CKFs is evaluated by the urban dynamometer driving schedule in varying temperatures. The simulation results show that the root mean square errors of SOC estimation by CKF, GHCKF, and SSA-CKF are kept within 1.4553 %, 1.2880 % and 1.2152 %, while for SSA-GHCKF, this metric is merely 1.1933 %. The proposed SSA-GHCKF enables superior accuracy and robustness for SOC estimation at extreme temperatures. [ABSTRACT FROM AUTHOR]

• Partially transformation growth of PBA on NiFe-MOF to obtain dual-MOF heterostructure. • NiFe-MOF/PBAs have an ultra-high specific capacity of 4270.19 c g−1 at 1 a g−1. • NiFe-MOF/PBAs//AC device has a high specific capacity up to 1996.01 c g−1 at 1 a g−1. • The device has excellent cycling stability of only 1.14 % decay rate (20,000 cycles). Metal organic framework (MOF) is considered as an excellent electrode material for supercapacitors due to its low cost and homogeneous nanostructure, but the drawbacks of single MOF, such as low specific capacity and stability, limit its development, so the design of bimetallic MOF structural composites is a challenging but favourable strategy for the development of supercapacitors. In this paper, NiFe-MOF/PBAs heterostructure, a bimetallic MOF material with a granular rod-like structure, is successfully prepared by using bimetallic MOF as a precursor and introducing [Co(CN) 6 ]3− ions to further convert it into PBAs (Prussian blue analogs). Due to the special macroporous structure of PBAs, the composite combines the advantages of the two MOF materials, and the specific capacity is as high as 4270.19 C g−1 at 1 A g−1. The composite still has excellent electrochemical properties when assembled into devices. The specific capacity is 1996.01 C g−1 at 1 A g−1, the energy density reached 749.99 W h kg−1 at a power density of 415.85 W kg−1, and the decay rate is only 1.14 % after 20,000 cycles at 10 A g−1. These results indicate that the designed dual MOFs composite electrodes have good application prospects in the field of electrochemical energy storage. [Display omitted] [ABSTRACT FROM AUTHOR]

• A simple and fast hydrothermal synthesis method was proposed in this paper to synthesize an electrode material with a heterostructure of NiMoO 4 nanoneedles and high-performance flower-shaped NiCoZn-LDH on a foam nickel substrate. • The electrochemical performance of the NiCoZn-LDH@NMO@NF nanoneedle composite electrode material, treated with CTAB, is significantly superior to that of the untreated NiMoO 4 @NF electrode. • It shows excellent electrochemical properties, including a specific capacitance of 3541 mF/cm2 in KOH solution and an outstanding capacity retention of 83.04 % after 10,000 cycles. Transition metal hydroxides have attracted wide attention as promising composite nanomaterials due to their numerous active sites and large specific surface areas. In this study, a two-step hydrothermal synthesis method is proposed to generate a heterostructure (NiCoZn-LDH@NiMoO 4 @NF) consisting of nanoflowers coated with nanoneedles on a foam nickel substrate. The aggregation issue of NiCoZn-LDH is effectively improved by immersing it in CTAB solution after one-step hydrothermal synthesis of NiMoO 4 nanoneedles on Ni Foam (NF). The heterostructure between NiMoO 4 nanoneedles and NiCoZn-LDH significantly enhances the material stability and electrochemical performance. Activated carbon is used as the negative electrode, and the NiCoZn-LDH@NiMoO 4 @NF composite material is used as the positive electrode to assemble an asymmetric supercapacitor (ASC) device for electrochemical testing. The device exhibits a specific capacitance of 3541 mF/cm2 at a current density of 6 mA/cm2. Furthermore, the capacity retention rate remains at 83.04 % after 10,000 cycles of charge and discharge, and a high specific energy density of 0.735 mWh/cm2 is achieved at a power density of 1.6 mW/cm2. The experimental results demonstrate that transition metal hydroxides play a crucial role in enhancing the electrochemical performance of supercapacitors. This study provides new insights into Supercapacitor (SC) active materials and offers a promising experimental approach for synthesizing new nanomaterials. [ABSTRACT FROM AUTHOR]

• The synthesized ILs were used as novel green electrolytes for supercapacitors. • Among the ILs, the smallest anion, formate, exhibited the highest performance. • The highest value of energy density of 70 Wh kg−1 was related to the farmate anion. Supercapacitors are promising technologies for extremely effective energy storage and power management, which is a critical and major area of worldwide technological advancement. Ionic liquids (ILs) are an environmentally benign promising emerging class of versatile solvent systems. In this paper, for the first time, a new approach to the application of monoethanolamine-based ILs with anions formate, acetate, and propionate ([HEA]F, [HEA]A, and [HEA]P) as eco-friendly, affordable, and easy synthesis electrolytes are proposed for activated carbon (AC)-based supercapacitors. The ionic conductivity and the electrochemical stable potential window (ESPW) of ionic liquids were assessed. The electrochemical performance of synthesized ILs as an electrolyte in AC-based supercapacitors was compared. Electrochemical properties were performed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), linear sweep voltammetry (LSV), and galvanostatic charge-discharge (GCD) methods to evaluate the electrolytic performance of ionic liquids in supercapacitors. The charge transfer resistance (R ct) and solution resistance (R s) decreased with decreasing anion size of ILs. At a scan rate of 10 mVs−1, the prepared supercapacitors using [HEA]F, [HEA]A, and [HEA]P ionic liquids deliver specific capacitance of 114, 95, and 73 F g−1, respectively. The maximum power density 2941 W kg−1 and maximum energy density 70 Wh kg−1 were obtained for the prepared supercapacitor using [HEA]F ionic liquid. The supercapacitors prepared with [HEA]F, [HEA]A and [HEA]P electrolytes show capacitance retention of 96%, 91% and 87% after 5000 charge-discharge cycles, respectively. [ABSTRACT FROM AUTHOR]

• Combination of unilateral solution impregnation with laser induction in one-step process to get manganese-assisted graphene electrodes. • The modifier under the laser is cleverly used to achieve the enhancement of the electric double layer capacitance and the incorporation of pseudocapacitance. • Nitrogen, oxygen and manganese in superhydrophilic graphene with high yield, large surface area and low impedance. • The capacitance of as-prepared device is performing ∼25 times of the control. • Balancing cycling performance and capacity improvement of supercapacitors. Laser-induced graphene (LIG) technology has made it possible to prepare graphene-based supercapacitors on a large scale and at low cost. However, the performance of graphene-based supercapacitors fabricated solely by laser still has a great potential for improvement. In this work, we obtained high-performance supercapacitors based on manganese-assisted laser-induced multi-layer graphene-like carbon (MLIGC) by a simple process. Poly-(m-phenylene isophthalamide) (PMIA) papers treated with modifier (KMnO 4) were used as substrates. Modifier not only deepened the cross-sectional carbonization and achieveed uniform dispersing of manganese oxide nanoparticles, but also changeed the surface properties of MLIGC. Benefit from the hybrid structure of manganese oxide nanoparticles uniformly dispersed inside multi-layer graphene-like carbon (LIGC) prepared by one-step laser process, the combination of electric double-layer capacitance and pseudocapacitance allows for a further breakthrough in capacity while maintaining excellent cycling stability. Specifically, the supercapacitors achieve an area capacity of 72.4 mF cm−2 at 0.2 mA cm−2, which is 25 times higher than the control. In addition to the significant capacity increase, the addition of the modifier also achieveed a significant impedance reduction (almost one ninth of the control) and demonstrateed excellent cycling stability (nearly 100 % capacity retention after 7500 cycles at 10 mA cm−2). More importantly, the method is simple, fast, low-cost and high-efficiency, which provides a new path for the large-scale preparation of planar carbon-based supercapacitors. [Display omitted] [ABSTRACT FROM AUTHOR]