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All-solid-state ionic supercapacitors based ceramic oxides exhibit better characteristics than the conventional liquid-electrolyte supercapacitors in terms of high safety and broad working potential. However, there are rare reports referring to the working mechanism as well as factors impacting the capacities of these solid- state supercapacitors. In this work, Li 3 x La 2/3- x □ 1/3-2 x TiO 3 (LLTO, □ represents vacancy) materials with different lithium contents (nominal 3 x = 0.33∼0.42) are synthesized and fabricated into solid-state supercapacitors, to study the capacity. Results exhibit that the Li 0.33 La 0.56 TiO 3 can release the highest capacitance of 0.28 m F⋅ g−1 among the samples with superior cycling performance under a potential range of 2 V at 300 K, based on an Au∣LLTO∣Au cell configuration. The possible factors to affect the capacity include the lattice structures, ionic conductivity, and working temperature. This study may provide new insights into the design of more stable energy storage devices with better safety. [ABSTRACT FROM AUTHOR]

Structurally distorted MnO 2 is obtained via a simple Ni-doping treatment. The substantially accelerated electronic and ionic transfer kinetics contribute to an enhanced Na+ storage performance for supercapacitors applications. [Display omitted] • Structure distorted MnO 2 was prepared via Ni doping. • The Ni-MnO 2 shows high specific capacity and excellent rate performance. • Ni-MnO 2 exhibits delocalized electron and accelerated ionic transport kinetics. Manganese dioxide is a typical electrode material for supercapacitor due to its high theoretical capacitance and good environmental compatibility. However, the development of MnO 2 as electrode is limited by inferior conductivity, sluggish ionic transfer kinetics and poor cycling stability. Herein, we present a structure distortion strategy via Ni doping in MnO 2 to boost its Na+ storage performance. The as-obtained Ni-MnO 2 can deliver a high specific capacity of 379F g−1 at 1 A g−1, excellent rate performance of 281F g−1 at 20 A g−1, and a significantly enhanced cycling stability. In situ Raman results verify that Ni-MnO 2 with structure distortion can achieve a promising cycling life. Density functional theory results suggest that the structure distortion can efficiently modulate electron configuration by delocalizing electron. Furthermore, the Na+ diffusion energy barrier is remarkedly decreased in Ni-MnO 2 , thus accelerating ionic transport kinetics. An asymmetric supercapacitor based on Ni-MnO 2 cathode exhibits a high energy density of 114.6 Wh kg−1 at a power density of 3600 W kg−1. This work verifies the efficiency of structure distortion strategy on the improvement of Na ion storage performance in MnO 2 , which can be extended for the optimization of other electrode materials for energy storage. [ABSTRACT FROM AUTHOR]

• Efficiency improvements in dc urban tram systems possible by adding energy storage. • EV batteries as lineside storage aid system efficiency. • Demonstrate viable ROI against different ESS capacity. This paper examines the possible placement of Energy Storage Systems (ESS) on an urban tram system for the purpose of exploring potential increases in operating efficiency through the examination of different locations for battery energy storage. Further, the paper suggests the utilisation of Electric Vehicle (EV) batteries at existing Park and Ride (P&R) sites as a means of achieving additional energy storage at these locations. The study achieves this through MATLAB modelling utilising captured GPS data and publically available information. This study examines the scenario of uni-directional substations with no interconnection between the overhead catenary for both directions of travel, and discusses the trade-offs between ESS size and required current limits. The results show the savings in both energy and basic CO 2 emissions alongside the discussion of Return on Investment (RoI) that can be achieved through the potential installation of ESS at identified ideal locations along the tram network. Moreover, this may be extended to the use of EVs as stationary ESS sited at the existing P&R facilities. Further, the model may also be used to inform future infrastructure upgrades and potential improvements to air quality within urban environments. [ABSTRACT FROM AUTHOR]

• Impact of installation locations and ESS capacity on tram network energy balance. • Economic feasibility study of ESS considering payback period, NPV and IRR. • Demonstrate energy and economic benefit of using EV battery as ESSs. Separate and common overhead catenary systems (OCS) are widely utilised on urban light-rail systems. This paper applies Simulink modelling to investigate differences in energy efficiency between two OCS systems, applied to a typical urban tram system. Results suggest common OCS reduces energy demand by 14%, as availability of regenerative braking increases by 297%. This paper predicts number, capacity and best installation locations for energy storage systems (ESSs) on an example system. Greater energy efficiency is achieved by installing ESS on centre stops between adjacent substations, rather than substation stops. Further, an economic study considers net present value, internal rate of return and payback period for a given ESS capacity; and a sensitivity analysis identifies capital cost and battery life as the most influential parameters to economic viability. Finally, using parked EVs as ESS for a tram system is explored to improve the economics. [ABSTRACT FROM AUTHOR]

• Ni, Co bimetallic selenides microspheres and BiSe nanosheets are synthesized. • The (Ni, Co)Se 2 demonstrate enhanced capacitive performances than pure NiSe 2 and CoSe 2. • A novel asymmetric supercapacitor based on all-metal selenides electrodes is proposed. • (Ni, Co)Se 2 //BiSe ASC possesses extended operating voltage and high energy density. Transition metal chalcogenides (TMCs) are considered as one of the most promising electrode materials for energy storage and conversion due to their unique intrinsic properties, but their electrochemical performance is largely limited by its poor conductivity. Thus, it is a feasible strategy to develop TMCs with hierarchical and ordered nanostructure to guide the electronic transport ways thereby enhance the electrical conductivity. Herein, a facile one-step solvothermal method has been designed and employed to synthesize uniform Ni, Co bimetallic selenides (termed as (Ni, Co)Se 2) microspheres and BiSe nanosheets. The (Ni, Co)Se 2 demonstrate enhanced capacitive performances of 106 mAh g−1 at 1 A g−1, which are more than two times of pure NiSe 2 and five times of pure CoSe 2 at the same current densities. Similarly, the BiSe nanosheets also exhibits a high specific capacity of 104 mAh g−1 at 1 A g−1 and good rate capability. Interestingly, a novel asymmetric supercapacitor is fabricated by using (Ni, Co)Se 2 nanospheres as the positive electrode and BiSe nanosheets as the negative electrode, which possesses extended operating voltage of 1.65 V, high energy density of 34.4 Wh·kg−1 at a power density of 373 W·kg−1, and an acceptable cycling stability of 85% capacity retention after 5000 cycles. A facile one-step solvothermal method has been designed and employed to synthesize uniform (Ni, Co)Se 2 microspheres and BiSe nanosheets. Based on high electrochemical properties and complementary operating voltage of (Ni, Co)Se 2 and BiSe materials, a novel (Ni, Co)Se 2 //BiSe asymmetric supercapacitor is fabricated from both metal selenides, which possesses extended operating voltage, high energy density, and good cycling stability. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Herein, a nickel nitrate-assisted polymer (gelatin), in situ substrate-free chemical blowing pyrolysis and subsequent low-temperature phosphorization method are used to prepare nickel phosphide nanoparticle self-inlaid carbon nanosheet frameworks (Ni 2 P-CNFs). The presence of CNFs in the Ni 2 P-CNFs structure can not only provide fast electrically conductive channels but also prevents the aggregation of the Ni 2 P nanoparticles, which results in maximum utilization of the reactive sites. Therefore, the as-fabricated Ni 2 P-CNFs used as a positive electrode for the supercapacitor shows a high specific capacity of 145 mAh g−1 at a current density of 0.5 A g−1, an excellent rate capability with 70% capacity retention as the current density increases in 20 times. To highlight, a novel aqueous asymmetric supercapacitor based on a positive Ni 2 P-CNFs electrode and a negative CNFs electrode is assembled, achieving a large operating voltage of 1.65 V, high energy density of 42 Wh kg−1 at a power density of 413 W kg−1, and outstanding cycling stability with 88% capacity retention after 6000 cycles. This study provides a top-down strategy for designing integrated and robust metallic self-decorated porous carbon nanomaterials, which may inspire further development for electrochemical energy storage and conversion applications. Image 1 • Asymmetric supercapacitor is assembled based on novel Ni 2 P-CNFs and CNFs electrodes. • Ni 2 P nanoparticles uniformly and tightly inlaid on carbon nanosheet frameworks. • Ni 2 P-CNFs//CNFs with an extended operating voltage of 1.65 V in aqueous electrolyte. • The ASC device exhibits a high energy density, high rate ability and excellent cycle stability. [ABSTRACT FROM AUTHOR]

Power-to-gas (P2G) technology is considered as a new approach for clean energy consumption and energy conversion. However, because this technology must be combined with other energy systems to build a stable energy system, a reasonable income distribution method is necessary to guarantee this integration. Firstly, the operation optimization model of the park integrated energy system (PIES) and park independent energy system (PINES) with P2G are constructed for the first stage optimization, with the objective of maximizing net income. Secondly, the energy system performance evaluation indicators are developed to assess the system quantitatively in terms of the economic and environmental aspects. Thereafter, the income distribution models based on Shapley value and the improved Shapley value with operational risk factor are created, and the total income is optimally distributed at the second stage based on the first-stage optimization results. Finally, an industrial park in a province of China is selected for case analysis. The results show that (1) PIES can complement different systems, integrate the demands in heat, electricity, and gas, while realizing the electricity-gas-heat/electricity conversion and heat-electricity complementarity. (2) Income distribution using an improved Shapely value method is proposed, it overcomes the one-sidedness of transaction volume and lack of differences among participants, reflects the actual operational risk and the degree of contribution of participants to the whole system, and promotes the incentives of cooperation. (3) Based on the improved income distribution model, the income of the PS, P2G, and HS are redistributed. The income of P2G increased by ¥7,450, which reflects the important collaborative value of P2G. The willingness of system cooperation increased by 742.392%. Therefore, the proposed operation optimization and income distribution model can enhance the incentives of participants want to cooperate under the premise of ensuring the maximum net income of the PIES. Moreover, it can be used as reference for the formulation of an optimal operation plan and income distribution of the complex energy system and it can provide a way to promote clean energy production. • The role of P2G as a new energy conversion way is studied. • The two-stage optimization model is constructed. • The first stage is operational optimization. • The second stage is income distribution. • The improved Shapley value method is applied in park integrated energy system. [ABSTRACT FROM AUTHOR]

Competitive costs and eco-friendliness have prompted solid waste-based recycling to become a hot topic of sustainability for energy storage devices. The closed-loop model, which combines the efficient recovery of solid waste with the preparation of energy storage materials, is considered as a tremendous potential sustainable development strategy. However, large-scale issues including environmental hazards, valuable ingredients, quantity and distribution remain due to the complex nature of solid waste properties, resulting in delays in its industrial applications. This review provides a systematic overview of the regeneration of various solid wastes into energy storage materials from the point of view of processing techniques and value-varying approaches. First, a summary of the solid waste classification and disposal procedures is provided, and the pros and cons of the disposal procedures are analyzed considering the resources and the environment. Moreover, the reactivation process of the resource cycle is detailed according to the regeneration of different battery energy storage materials (lithium-ion battery, sodium-ion battery, lithium-sulfur battery, supercapacitor, fuel cell, etc.), including waste recycling and high-value material regenerated processes. In addition, a comprehensive evaluation of various types of energy storage batteries is carried out from the perspectives of economy, environment, technological difficulty, application status, and development potential, to provide a feasible reference for the future regeneration of suitable energy storage batteries. Finally, the main challenges of recycling solid wastes into energy storage materials are summarized as "two Highs and four Lows". This review has systematically reviewed and summarized research from technological feasibility and potential advantages in the regeneration of energy storage materials from multiple solid waste sources. A comprehensive analysis was conducted, involving the classifications, technologies, environmental impact, economic benefit and the main challenges, which concentrated on the disposal of solid waste (industrial wastes, municipal wastes, and natural wastes) and the resynthesize of energy storage materials (lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, supercapacitors, and fuel cells). Based on the obtained insights, this regeneration model is thought to alleviate resources famine, but in the future, the government and appropriate researchers should focus on solving current problems, including high secondary pollution, high technological difficulty, low material performance, low economic benefit, low industrialized application, and low policy support. [Display omitted] • The current status and disposal method of solid wastes is summarized. • Regenerating energy storage materials from solid wastes are classified. • The advantages and disadvantages of regenerating different materials are compared. • The main challenges are summarized as "two Highs and four Lows". [ABSTRACT FROM AUTHOR]

Abstract A green and low-cost method is presented to fabricate graphene fibre electrodes by electrochemical exfoliation of thin strips of graphite foil. When assembled into micro-supercapacitors, the graphene fibres achieved an excellent electrochemical capacitance (∼247.6 mF cm−2 at ∼2 mA cm−2) and low equivalent series resistance (∼2.4 Ω), a significant improvement over the typically used graphene oxide based fibres. This excellent capacitive performance indicates these graphene-based energy storage devices could be ideal for microelectronics applications. Additionally, an all-solid-state flexible micro-supercapacitor was fabricated using a gel electrolyte (H 3 PO 4 /PVA) and exhibited a high areal capacitance of 70.6 mF cm−2 and a superior cycling stability of ∼96% capacitance retention after 2400 cycles, suggesting possible applications for flexible energy storage. The easily scalable and facile single step strategy presented here outperforms the conventionally used graphene oxide based methods, which typically require harmful chemicals and involve a more complex synthesis procedure. [ABSTRACT FROM AUTHOR]

• Conducting polymer (polypyrrole)-intercalated V 2 O 5 is synthesized by a simple hydrothermal technique. • Polypyrrole enlarges the layer spacing of V 2 O 5 and forming a highway for ion diffusion. • Charge storage mechanism of Zn2+ and H+ co-intercalation layer is confirmed. • The electrode exhibits excellent electrochemical performance in aqueous zinc-ion batteries. Aqueous secondary zinc-ion batteries are promising candidates to replace lithium-ion batteries for large-scale energy storage, due to their high safety and low cost. However, the developed cathodes materials are facing low capacity or low cycle life due to sluggish diffusion kinetics. Therefore, the design of a cathode with ultrafast ion diffusion kinetics remains a great challenge. Here, we propose an in-situ intercalation strategy of polypyrrole to improve the cation diffusion kinetics of V 2 O 5. The polypyrrole as a guest significantly enlarges the interlayer spacing, paving the "superhighway" for cation diffusion. In addition, thanks to the unique π-conjugated structure, polypyrrole can shield the electrostatic force of Zn2+ and the host oxygen-sublattice. The energy storage mechanism of the cathode was shown to be a stepwise H+/Zn2+co-intercalation by means of galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS) and ex situ X-ray diffraction (XRD). Based on the above advantages, the polypyrrole-intercalated V 2 O 5 demonstrates high capacities and excellent cycling performance (220 mA h g−1 after 2000 cycles at 10 A g−1). We report an in-situ intercalation strategy of polypyrrole to improve the cation diffusion kinetics of V 2 O 5. The polypyrrole as a guest significantly enlarges the layer spacing, paving the "superhighway" for Zn2+ and H+ diffusion. [Display omitted] [ABSTRACT FROM AUTHOR]

• Well-aligned MOF array on Ni foam was prepared by a template-directed growth strategy. • The chemical compositions of active materials were facile regulated by controlling the hydrolysis time. • The unique hierarchical structure contributes to high specific capacity of active materials. • The electrodes demonstrate excellent performance for NiCo-Zn batteries and supercapacitors. We report a novel strategy for preparing nickel-cobalt double hydroxide (NiCo-DH) array on nickel foam with template-directed growth of MOF array as the precursor. The obtained sample that inherits the many advantages of MOF can be directly applied to both Ni-Zn aqueous secondary battery and hybrid supercapacitor. [Display omitted] Rational design of self-supporting and well-aligned MOF-derived electrode materials is a great challenge. In this work, we report a novel strategy for preparing nickel-cobalt double hydroxide (NiCo-DH) array on nickel foam with template-directed growth of MOF array as the precursor. The obtained sample can be directly applied to both Ni-Zn aqueous secondary battery and hybrid supercapacitor. Due to the many advantages inherited from the MOFs material, the NiCo-DH array displays an ultrahigh reversible specific capacitance (325.6 mAh g−1 at 2 mA cm−2) and excellent rate performance (75.5% of initial capacity retention under 40 mA cm−2). As a cathode for NiCo-Zn batteries, the NiCo-DH electrode exhibits a high specific capacity of 329 mAh g−1 and satisfactory cycling stability. Moreover, the assembled NiCo-DH //active carbon asymmetric supercapacitor exhibited a remarkable capacity of 0.359 mAh cm−1 at 0.5 mA cm−1 and exhibited excellent durability (capacitance retention of 91% after 5 000 cycles). Furthermore, the hybrid device exhibited an impressive energy density of 50.5 Wh kg−1 at a power density of 750 W kg−1. The presented strategy for controlled design and synthesis of MOF-derived self-supported electrode offers prospects in developing highly electrochemical active electrode materials in energy storage devices. [ABSTRACT FROM AUTHOR]

Freestanding CuV 2 O 6 /reductive acidified carbon nanotube (CVO/RCNTs) composite films with excellent flexibility and conductivity were prepared via a vacuum filtration strategy and made into the aqueous Zn//CVO/RCNTs gel battery, which exhibited stable electrochemical properties under different bending conditions. [Display omitted] • Free-standing CuV 2 O 6 /RCNTs composite films with high flexibility were achieved. • RCNTs provided a 2 µm conductive substrate for the film as a current colletor. • The aqueous Zn//CVO/RCNTs gel battery exhibited stable electrochemical properties. • Great potential as flexible wearable energy storage devices. Rechargeable aqueous zinc-ion batteries (ZIBs) have become a key research object in the field of new generation energy storage devices due to their high safety, low cost and eco-friendliness, and show a promising potential application. In this work, CuV 2 O 6 nanobelts were synthesized by the hydrothermal method and freestanding CuV 2 O 6 /reductive acidified carbon nanotube (CVO/RCNTs) composite film without any binder was synthesized by vacuum filtration. The aqueous Zn//CVO/RCNTs batteries presented a admirable reversible capacity of 353 mAh g−1 at 0.1 A g−1 and the cycling performance with a high reversible capacity of 174.7 mAh g−1 and 61.5% capacity retention after 1400 cycles at 5 A g−1,making rings round the vast majority reported zinc ion batteries.More importantly, the CVO/RCNTs composite films had stable electrochemical properties under different bending degrees after preparation into flexible gel batteries, demonstrating great potential in the field of flexible wearable zinc ion batteries. [ABSTRACT FROM AUTHOR]

Heterostructures of manganese oxides (MnO x , i.e., MnO and Mn 3 O 4) with carbon nitride (CN@MnO x) are prepared to boost the Na + storage capability of MnO x. Two different interfacial electric fields originated from the electronic redistribution at the interfaces of CN@MnO and CN@Mn 3 O 4 endow CN@MnO x with high reversible capacity of 305 F g−1 at 1 A g−1, ultrahigh rate capability of 223 F g−1 at 20 A g−1, and exceptional long-term cycling lifespan without significant capacity decay up to 5000 cycles at 1 A g−1. An asymmetric supercapacitor based on CN@MnO x electrode materials delivers a high energy density of 46.7 Wh kg−1 at a power density of 1000 W kg−1. Mechanism studies showed that the enhanced sodium ion storage performance in CN@MnO x is attributed to a dual-directional electronic modulation of MnO x , which simultaneously improve the electronic conductivity and accelerate the Na+ transfer kinetics. This work opens up a unique strategy to regulate the electronic structure of multi-phase electrode materials, and meanwhile provides new clues for the energy storage mechanism in multi-phase electrode materials. [Display omitted] • The electronic structure of multi-phase CN@MnO x is successfully regulated. • Dual electric fields are induced by dual-directional redistribution of charges. • The resultant CN@MnO x displays high capacity and significant rate capability. [ABSTRACT FROM AUTHOR]

Prussian blue is considered as a promising zinc ion battery material because of its advantages such as stable structure, large lattice gap and simple preparation process. However, the poor conductivity seriously hinders the application of Prussian blue electrode materials. Herein we report a simple and interesting strategy to grow Prussian blue nanoparticle on expanded graphite electrode through a facile electrochemical method. Thanks to the synergy between Prussian blue analogue nanoparticles and self-supporting graphite flakes, the composite electrode with unique architectural structure possess both battery and capacitor characteristics. What's even more interesting is that the defects of Prussian blue crystals are gradually reduced during the extraction and insertion of zinc ions, and then the increasingly perfect crystal structure result in excellent cycling performance (120% capacitance retention after 12,000 cycles). [ABSTRACT FROM AUTHOR]

Conductive polymers (CPs) have potential for commercial energy storage applications because of their high electrochemical activity and low cost. However, one of the obstacles in developing CPs based supercapacitors is to overcome the capacitance degradation during the charge-discharge process, along with the poor rate performance. In this work, a unique bowl-shaped graphene/polypyrrole (PPy) nanostructure is uniformly grown on a graphite substrate by two facile electrochemical steps. The graphene is uniformly coated by PPy layers, while the thickness of the PPy layer depends on deposition time. The unique structural design for the PPy layer exhibits a significant influence on its electrochemical properties, and competitive performance is achieved by the GP-1200 based supercapacitor devices. It exhibits a maximum energy density of 5.18 mWh·cm−3 and a maximum power density of 250.5 mW cm−3, which are both comparable to values obtained from other solid-state supercapacitor devices. Image 1 • A novel bowl-shaped polypyrrole/graphene as flexible all-solid-state electrode. • Polypyrrole/graphene electrode exhibits a large areal capacitance of 3.00 F cm−2. • The device delivers outstanding energy density of 5.18 mWh·cm−3. • 96.8% capacitance retention even after 10,000 cycles. [ABSTRACT FROM AUTHOR]

Herein, a facile simultaneously activation and catalytic carbonization of the rare earth metal lanthanum-organic frameworks precursor strategy is developed to prepare a novel three-dimensional (3D) mesoporous interconnected carbon nanosheets (LMCN) with large surface area and high graphitization degree. During the synthesizing process, the ZnCl 2 and FeCl 3 act as activation and catalysis, respectively, to promote the formation of mesoporous carbon nanosheets with developed pores structure. The typical LMCN-1 prepared by high percentage of ZnCl 2 and FeCl 3 holds an interconnected mesoporous framework composed of ultrathin nanosheets and abundant porosity, displaying high specific capacitance of 251 F g−1 at a current density of 0.5 A g−1 and holding an excellent rate performance. Moreover, a symmetric supercapacitor assembled based on LMCN electrodes exhibits a prospective high energy density of 20.7 Wh kg−1 at a power density of 228 W kg−1 with a wide working voltage of 1.8 V in 0.5 M Na 2 SO 4 aqueous solution, along with the suitable capacity retention of 90.7% after 10,000 cycles. Image 1 [ABSTRACT FROM AUTHOR]