Energy Storage Materials Research Articles

Architecting hydrogen-bonded and π–π conjugated MOF@NiPc networks towards enhanced energy storage

High-capacity metal–organic framework materials is constrained by their poor electron transport and unstable in aqueous. Herein, a spherical cobalt–nickel-based metal–organic framework (CoNi-MOF) micro-architecture with 18-π aromatic electron system of nickel phthalocyanine (NiPc) nanorods has been designed. In this system, intermolecular hydrogen (H) bonds between O in CoNi-MOF and H in nickel phthalocyanine (NiPc), along with longitudinal π-π stacking structure, could improve electron transport and structuralstability of MOFs. Benefiting from the 3D electron transport highways and “locking” effect of H bonds along with longitudinal π-π stacking structure, the optimized CoNi-MOF@NiPc electrode exhibits remarkable specific capacity of 807.365C g−1 at current density of 1 A/g, along with great cycling stability with 96.19 % capacity retention after 5000 cycles at 5 A/g, which is superior to the individual components. Besides, CoNi-MOF@NiPc//AC hybrid supercapacitor has been fabricated, which displays a maximum energy density of 130.68 Wh kg−1 at 962.09 W kg−1 and excellent cyclability (93.58 % capacity retention after 10,000 cycles). This study opens a new avenue for the design of organic electrodes and provides a new insight into H bond and π-π stacking structure effect toward advanced energy storage materials.

Hydrophobic composite phase change coating: Preparation, performance and application

The utilization of composite phase change materials in energy storage and solar thermal applications is significantly restrained by their inherent non-hydrophobic surfaces and susceptibility to contamination. This study presents a novel synthesis of modified paraffin (Pa) @ silica (SiO2) nanocapsules through an efficient in situ hydrolysis and polycondensation reaction utilizing tetraethyl orthosilicate (TEOS) as the silicon source, paraffin as the phase change material, and hexamethyldisilazane (HMDS) as the surface modifier. These nanocapsules were then employed to formulate a composite phase change coating (PSC-1) by spraying onto a substrate of lithium silicate (Li2SiO3), a green inorganic binder. This coating combines self-cleaning and energy storage functionalities. The thermal characterization of PSC-1 revealed an enthalpy of phase transition of 92.95 J/g at a core-shell ratio of 1.5:1 and an HMDS to TEOS volume ratio of 1:1. Additionally, the thermal conductivity of PSC-1 was measured at 0.505 W/m∙K, which is approximately 53 % higher than that of pure paraffin. PSC-1 also demonstrated superior hydrophobicity, with a static water contact angle of 132.6°. Enhancing its practicality, the coating was subsequently dyed black and assessed for photothermal conversion efficiency, which was determined to be around 68 %. The integration of robust self-cleaning properties and high-efficiency thermal characteristics renders PSC-1 a highly promising material for broad applications in solar energy conversion and storage.

Design and assessment of a concentrating solar thermal system for industrial process heat with a copper slag packed-bed thermal energy storage

Decarbonising the industrial sector is a key part of climate change mitigation targets, and Solar Heat for Industrial Process (SHIP) is a promising technology to achieve this. However, one of the drawbacks of SHIP systems is that they rely on an intermittent energy source. Therefore, sensible energy storage has emerged as a potential solution. In addition, solid byproducts have been proposed as a low-cost but effective material for thermal energy storage (TES). This work presents a SHIP system model coupled with a copper slag-packed-bed TES (PBTES) model using air as heat transfer fluid. The TES has been implemented to preheat the makeup water of the tank where steam is generated. A system design was carried out using a parametric analysis to find a solar field size and a corresponding TES volume. The resulting system was simulated, and the operating variables were analysed in detail. The results show that it is possible to generate 20% more energy due to the storage system. Additionally, a techno-economic analysis indicates that the SHIP with PBTES system results in a payback period of 14 years and a savings of CO2 emissions of 30tCO2.

Wood-derived biochar as a matrix for cost-effective and high-performing composite thermal energy storage materials

Wood-derived biochar as a matrix for cost-effective and high-performing composite thermal energy storage materials

Triarylamine-based polyimide COFs for achieving high performance ambipolar multi-color electrochromic energy-storage films

Electrochromic energy storage materials that possess both electrochromic and electrochemical energy-storage properties have attracted significant attention for applications in visual energy-storage, energy-efficient windows, as well as displays. To fulfill their comprehensive applications, electrochromic energy-storage materials require specific characteristics, such as transparency, ambipolarity, multi-color capabilities, and high capacitance. Here, the polyimide covalent-organic framework based on triarylamine (PM-TPI and NT-TPI) COF films were grown successfully on FTO glass through solvothermal polycondensation, and exhibited crystallization, hierarchical porous structures, and ambipolar electrochemical redox activity. Notably, NT-TPI COF film displayed transparent bleached state, ambipolar electrochromism, multi-color (transparent, orange-red, cyan, gray), and high optical contrast. Due to their large specific surface area and efficient electron/ion transport ability, the NT-TPI COF film effectively controlled visible and near-infrared light, achieving optical contrasts of 49.8 % and 70.0 % at 420 and 850 nm, respectively. Moreover, the NT-TPI COF films showed promising electrochemical energy-storage properties and excellent charge–discharge rate performance, with a specific capacitance of 141.0 mAh/g. Additionally, NT-TPI COF/WO3-based ambipolar eclectrochromic energy-storage devices also exhibited high optical contrast from visible to near-infrared regions, and large capacitance. In summary, the NT-TPI COF film effectively combines the electrochromic and electrochemical energy-storage capabilities, making it a promising candidate for electrochromic energy-storage materials with transparency, ambipolarity, high optical contrast, multi-color functionality, and high specific capacitance.

A shape-stable phase change material for high-temperature thermal energy storage based on coal fly ash and Na2SO4-K2SO4

Using coal fly ash (CFA) as the skeleton material and binary sulfates of Na2SO4-K2SO4 as the phase change material (PCM), high-temperature coal fly ash based phase change thermal storage materials (CPCM) were successfully synthesized. The influences of CFA fractions and types on the morphology, physicochemical properties, and thermal characteristics of the composites were intensively investigated. Results show that the heat storage density and thermal conductivity of CPCMs increase with the PCM content. Particularly, the CPCM60-A composite, comprising 60 wt% Na2SO4-K2SO4 eutectic and 40 wt% CFA-A, exhibits excellent chemical compatibility and stable shape retention after sintering. Furthermore, CPCM60-A demonstrates the highest phase change latent heat of 60.43 J/g and thermal conductivity of 0.61 W/(m·K). The influence of CFA types reveals that CFA-A with a higher ratio of SiO2 and Al2O3, lower carbon content, and a rich porous structure is more suitable to fabricate molten salt heat storage materials. This work demonstrates that CFA, a byproduct of coal-fired industry, is a promising skeleton material for the fabrication of high-temperature CPCM composites, offering a novel approach for enhancing the efficiency and cost-competitiveness of solar power and waste heat recovery systems.

Conductive Polymer-Based Electrodes and Supercapacitors: Materials, Electrolytes, and Characterizations.

New materials and the interactions between them are the basis of novel energy storage devices such as supercapacitors and batteries. In recent years, because of the increasing demand for electricity as an energy source, the development of new energy storage materials is among the most actively studied topics. Conductive polymers (CPs), because of their intrinsic electrochemical activity and electrical conductivity, have also been intensively explored. While most of the high capacitance reported in the literature comes from hybrid materials, for example, conductive polymers composed of metal oxides and carbon materials, such as graphene and carbon nanotubes, new chemistry and the 3D structure of conductive polymers remain critical. This comprehensive review focuses on the basic properties of three popular conductive polymers and their composites with carbon materials and metal oxides that have been actively explored as energy storage materials, i.e., polypyrrole (PPy), polyaniline (PANi), and polythiophene (PTh), and various types of electrolytes, including aqueous, organic, quasi-solid, and self-healing electrolytes. Important experimental parameters affecting material property and morphology are also discussed. Electrochemical and analytical techniques frequently employed in material and supercapacitor research are presented. In particular, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are discussed in detail, including how to extract data from spectra to calculate key parameters. Pros and cons of CP-based supercapacitors are discussed together with their potential applications.

High energy storage performance of KNN-based relaxor ferroelectrics in multiphase-coexisted superparaelectric state

Although K0.5Na0.5NbO3 (KNN) possesses large maximum polarization and relatively high breakdown strength, the large remnant polarization constrains their practical applications as energy storage materials. In this work, through multi-element doping, (K0.5−0.5xNa0.5−0.5xBix)(Nb1−xSn0.2xZn0.6xTa0.2x)O3 relaxor ferroelectrics were prepared. As the superparaelectric states (SPE) were adjusted to room temperature, orthorhombic, tetragonal, and cubic phases coexisted, accompanied by the highly dynamic polar nanoregions (PNRs). In particular, a high recoverable energy storage density of 4.5 J/cm3 and an energy storage efficiency of 83% were achieved for the x = 0.125 ceramic, with the variations less than 11% and 4%, respectively, in the wide temperature range of 20–180 °C. These results demonstrate that the multiphase PNRs in the SPE state is an effective strategy for improving the energy storage performance of KNN-based ceramics.

Cellulose-reinforced foam-based phase change composites for multi-source driven energy storage and EMI shielding

To address the increasingly serious environmental pollution and energy crisis, there is an urgent need to develop multi-source-driven energy storage materials, the field of new energy sources, such as solar thermal power generation, but electromagnetic pollution has become a primary problem that needs urgent resolution. Therefore, the development of multifunctional phase change composites (CPCMs) with multi-source drive capabilities and excellent electromagnetic shielding integration is crucial. In this study, polypyrrole (PPy)-coated conductive fibers were crosslinked with polyvinyl alcohol (PVA) to form a three-dimensional network, which was then combined with metal foam to prepare Ni–F/PPy@CNF-PVA (PCN) dual-network carriers with high electrical conductivity by vacuum-assisted adsorption and freeze-drying methods. Polyethylene glycol (PEG) was subsequently encapsulated via vacuum impregnation to get the shape-stable PEG/Ni–F/PPy@CNF-PVA (PPCN) phase change composites. The PPCN exhibited good stability and high energy storage density (melt enthalpy up to 126.18 J/g, relative enthalpy efficiency over 99 %). Benefiting from its outstanding electrical conductivity (186680 S/m for PPCN-3), light-absorbing properties, and magnetism, the PPCN also exhibits highly efficient photothermal, electrothermal, and magnetothermal conversion capabilities. The electromagnetic interference shielding efficiency reaches up to 110.37 dB within the X-band frequency range (8.2–12.4 GHz). In conclusion, PPCNs are significant for multi-source-driven energy storage and electromagnetic shielding.

Computational study on single atom anchored on B2C3P monolayer as electrocatalysts for nitrogen reduction reaction

NH3 is an indispensable raw material for the synthesis of life compounds, as well as an intermediate of energy storage materials with high hydrogen content and clean energy carrier. Recently, with the development of electrocatalytic nitrogen reduction reaction (NRR), a new method of green and efficient NH3 synthesis has been found. The key of this method is to design the catalyst with high activity and selectivity. Herein, the catalytic activity of noble metal single atom supported on B2C3P (NM@B2C3P) as electrocatalysts for the NRR was explored by using the first-principles calculation. And the main basis for characterizing the catalyst activity was determined, Ir@B2C3P was successfully screened, which not only have thermodynamic stability, but also exhibit excellent NRR activity with low energy barrier of 0.513 eV and good selectivity. Meanwhile, the analysis of electronic properties also revealed the reason for the high catalytic activity.

NH4Al(SO4)2·12H2O-Na2SO4 eutectic-based phase change materials with excellent light absorbance, enhanced thermal conductivity, and high latent heat performance

A novel eutectic phase change material with light absorption and high thermal conductivity was successfully prepared. The based phase change material was ammonium aluminum sulfate dodecahydrate‑sodium sulfate eutectic phase change materials. The black Ti2O3 after ball milling was selected as light thermal conversion material which can absorb sunlight effectively and simultaneously convert the light to thermal and the expanded graphite was added to further improve the thermal conductivity of phase change materials. The phase change temperature of the eutectic phase change material was effectively regulated to 80 °C compared with 93 °C of pure aluminum sulfate dodecahydrate. The thermal conductivity of eutectic phase change materials with expanded graphite was enhanced to 1.16 W·m−1·K−1 compared with 0.53 W·m−1·K−1 of the pure eutectic phase change material. By adding Ti2O3, the combination material shows the best solar absorbance capacity of 87.96 % compared with the pure eutectic phase change materials of 73.43 %. The latent heat of the novel material was 190.97 kJ/kg. Considering their huge superiority of highly efficient use of solar energy in natural resources, the new novel ammonium aluminum sulfate dodecahydrate‑sodium sulfate eutectic-based phase change material with excellent light absorbance, enhanced thermal conductivity, and high latent heat performance is a very promising material for solar-thermal conversion and energy storage.

High performance biochar derived from mycelium-based leather composites waste for energy storage applications

The mycelial waste generated during the production of mycelium-based leather composites presents both opportunities and challenges in maximizing biomass resource efficiency. In this study, we synthesized mesoporous biochar (AGLM-5) with a specific surface area of 3151.9 m2/g through the KOH activation method using Ganoderma lucidum mycelium waste as the precursor material. AGLM-5 exhibited exceptional performance in a three-electrode system test, demonstrating a specific capacitance of 303.5 F/g. In a two-electrode system test, it achieved an energy density of 45.5 Wh/kg at a power density of 450.7 W/kg. The symmetric supercapacitor assembled using AGLM-5 demonstrated outstanding cycling stability over 10,000 cycles, exhibiting a capacitance loss of less than 4 % throughout the entire testing period. Additionally, we employed a hydrothermal method to synthesize composite electrode sheets (δ-MnO2/AGLM-5), which not only supported the layered structure of δ-MnO2 but also significantly improved the cycling stability and electrical conductivity of aqueous zinc ion batteries (AZIB). This study presents an environmentally friendly and sustainable approach for utilizing Ganoderma lucidum mycelial biomass, with particular emphasis on the potential application of mycelial carbon materials in battery energy storage.

Fabrication and characterization of zinc anode on nickel conductive cloth for high-performance zinc ion battery applications

The development of advanced materials for energy storage is critical to addressing global energy challenges. Zinc-ion batteries offer a promising solution due to their safety, cost-effectiveness, and environmental friendliness. In this study, we enhanced the conductivity of cotton by coating it with electroless nickel, followed by zinc electroplating, to create a flexible material suitable for zinc-ion battery applications. Cotton was coated with electroless nickel at temperatures ranging from 40°C to 60°C for 1 min to 13 min. Subsequently, zinc electroplating was performed with current densities of 0.02 A·cm‒2 for 60 min, 0.03 A·cm‒2 for 40 min, and 0.04 A·cm‒2 for 30 min. The resulting material was used to assemble a battery with an (NH4)2V10O25·8H2O (NVO) cathode. The Scanning Electron Microscope (SEM) confirms the electroless nickel-coating on cotton fabric at 50°C for 9 min resulted in a low electrical resistance of 15 ohms. Subsequent zinc electroplating at 0.03 A·cm‒2 for 40 min fully interconnected zinc particles. This research demonstrates the significant potential for further development in the field of textile materials for electrical conductivity. It also makes it possible to incorporate materials like silk cloth and other materials in battery components, which will help build more sustainable energy sources in the future.

Coordination and Hydrogen Bond Chemistry in Tungsten Oxide@Polyaniline Composite toward High-Capacity Aqueous Ammonium Storage.

Aqueous ammonium ion batteries (AAIBs) have garnered significant attention due to their unique energy storage mechanism. However, their progress is hindered by the relatively low capacities of NH4 + host materials. Herein, the study proposes an electrodeposited tungsten oxide@polyaniline (WOx@PANI) composite electrode as a NH4 + host, which achieves an ultrahigh capacity of 280.3 mAh g-1 at 1 A g-1, surpassing the vast majority of previously reported NH4 + host materials. The synergistic interaction of coordination chemistry and hydrogen bond chemistry between the WOx and PANI enhances the charge storage capacity. Experimental results indicate that the strong interfacial coordination bonding (N: →W6+) effectively modulates the chemical environment of W atoms, enhances the protonation level of PANI, and thus consequently the conductivity and stability of the composites. Spectroscopy analysis further reveals a unique NH4 +/H+ co-insertion mechanism, in which the interfacial hydrogen bond network (N-H···O) accelerates proton involvement in the energy storage process and activates the Grotthuss hopping conduction of H+ between the hydrated tungsten oxide layers. This work opens a new avenue to achieving high-capacity NH4 + storage through interfacial chemistry interactions, overcoming the capacity limitations of NH4 + host materials for aqueous energy storage.

Self-Exfoliating Benzotristriazine Macrocyclic Network: A New 2D Material for High-Performance Electrochemical Energy Storage.

Aza-fused aromatic π-conjugated networks are an important class of 2D graphitic analogs, which are generally constructed using aromatic precursors. Herein, the study describes a new synthetic approach and electrochemical properties of a self-exfoliating benzotristriazine 2D network (BTTN) constructed using aliphatic precursors, under relatively mild conditions. The obtained BTTN exhibits a nanodisc-like morphology, the self-exfoliation tendency of which is ascribed to the presence of structurally different macrocycles with high electronic repulsion between the layers. The benzotristriazine repeat units of BTTN is electroactive and holds higher carbon/nitrogen ratio when compared with the conventional graphitic aza-fused π-conjugated networks. The self-exfoliated BTTN nanodiscs show excellent electrochemical energy storage of 485 and 333 F g-1 at 1 A g-1 in three-electrode and two-electrode measurements, respectively. BTTN in a symmetric coin-cell architecture exhibits a high specific energy value of 46Wh kg-1 at a power density of 1kW kg-1 and shows excellent cyclic stability of 96% for 10000 and 90% for 30000 charge-discharge cycles at a higher current density of 5 A g-1, surpassing the device performance of most of the reported all-organic pseudocapacitive 2D networks.

Upcycling drinking bottle waste to intercalated 2D-0D carbon architectures and its supercapacitor applications

Despite its many benefits to our modern life, plastic contributes a large volume of solid waste that increasingly threatens our environment and health. Through a hydrothermal depolymerization and carbonization process that involves nitric acid and ethanol, drinking bottles that are made of polyethylene terephthalate are successfully converted into carbon quantum dots (CDs) and thin carbon nanosheets simultaneously with the former intercalated between layers of the latter to form a unique ball-sheet architecture. When used as electrode material, the stacking carbon nanosheets in this plastic-derived, ball-sheet carbon (PBSC) structure create a conductive network to allow rapid transport of ions and electrons while the well-dispersed CDs offer a large surface area and numerous sites to host them. The supercapacitors made of these PBSC electrodes exhibit double-layer capacitor behaviors with a specific capacity reaching 237 F/g at a charge rate of 1 A/g and excellent cycling stability. Our efforts offer a new route to upcycle plastic waste as valuable energy storage materials, which may help boost its recycling and the sustainable deployment of various clean energy resources.

Oxygen-rich 3D hierarchical porous MXene prepared by Zn powder reduction for flexible supercapacitors

Ti3C2Tx MXene is highly compelling as an energy storage material, but 2D MXene sheets experience significant stacking due to hydrogen bonding and van der Waals forces. This blocks active sites and impedes fast electrolyte ion transport. The pseudocapacitance of MXene materials is highly reliant on their terminal groups. Therefore, an effective strategy was designed herein to prepare an oxygen-rich 3D hierarchical porous MXene (P-OR-Ti3C2Tx). First, Zn powder was used as a template to construct three-dimensional hierarchical porous structures that spanned the microporous, mesoporous, and macroporous scales. Second, Zn powder was used as a metal reducing agent in a reaction at 500 °C to eliminate most −F terminal groups on the MXene. Then, a subsequent acid washing step was used to introduce numerous −O terminal groups. The energy storage process of the prepared MXene was investigated by in situ Raman. More redox active sites (−O terminal groups) are exposed by the constructed oxygen-rich 3D hierarchical porous MXene structure, which also provides a shorter pathway for electrolyte ion transport. P-OR-Ti3C2Tx displays superb rate performance (88.19 % retention at 100Ag−1) and ultra-high capacitance (676.7F/g at 2 mV/s and 698.7Fg−1 at 1 Ag−1) when used as a supercapacitor electrode. Moreover, a symmetric flexible supercapacitor device prepared using P-OR-Ti3C2Tx and carbon cloth achieves a superb energy density of 32.8Whkg−1 at a power density of 236.5Wkg−1. This study offers insight into the design of MXenes that exhibit both high capacity and excellent rate performance.

In situ decoration of 0D-nickel boride on 2D-vanadium MXene composites: An advanced electrode material for high energy density supercapacitors

Vanadium carbide-MXene (V2CTx) is considered a rising star among 2D materials and is an ideal electrode material for energy storage due to its unique features. However, oxidation and layer restacking can impair specific capacity (Cs) and cycling performance. Considering this challenge, we have developed a composite material consisting of amorphous nickel boride (NixB NPs) and V2CTx. To prevent oxidation and restacking of the layers and to improve the performance of the supercapacitor, NixB was decorated between the gaps and the surface. The V2CTx and its composites were prepared by simple etching and direct liquid-phase methods. Under the optimized conditions, the NixB/V2CTx modified nickel foam exhibited an improved Cs value of 705.9 C g−1 and a rate capability of 53.8 % at a current density of 10 A g−1; the excellent cycling stability was 120.5 % after 10,000 cycles at 10 A g−1 in 3 M KOH. The improved Cs values, shortened ion diffusion paths, swift electron transfer, and excellent cycling stability of the composites are due to the V2CTx layers surface entrapped/gaps filled by the NixB NPs. For practical application, an asymmetric device with NixB/V2CTx and reduced graphene oxide (rGO) as positive and negative electrodes was fabricated. The NixB/V2CTx//rGO device achieved a maximum energy density of 50.22 Wh kg−1 at 800 W kg−1 and 26 Wh kg−1 at 16000 W kg−1. The capacity retention was 89.98 % and the Coulombic efficiency was 99.9 % after 20,000 continuous cycles at 8 A g−1. These results emphasized that the developed 0D/2D NixB/V2CTx electrode materials with novel composite architecture are suitable for advanced energy storage applications.

Effects of pore characteristics on CO2 adsorption performance of coal slime with different metamorphic degrees

With the rapid development of Carbon Capture, Utilization and Storage (CCUS) technology, it is necessary to explore the feasibility of coal slime as a porous carbon material for CO2 capture. In this paper, scanning electron microscopy (SEM) was used to observe the morphological characteristics of coal slime samples with different metamorphic degrees, and the pore structure of coal slime was explored by low temperature N2 adsorption and low-pressure CO2 adsorption experiments. The pore distribution characteristics were analyzed, and the adsorption law of different metamorphic degrees were summarized through CO2 isothermal adsorption experiments. The results showed that: The specific surface area (SSA) and pore volume (PV) of the mesopores of the coal slime exhibited a U-shaped distribution with coal rank, and are much smaller than that of its micropores. Micropores less than 2 nm are the main adsorption space of coal slime, its PV accounted for 59%, 60%, 71%, and SSA accounted for 92%, 93%, 95%, obviously, which are dominant at all stages. The linear correlation fitting coefficients R2 between the limiting adsorbed amount a of CO2 and the micropores PV and the SSA were up to 0.830 and 0.887, respectively. The coal slime has good adsorption performance for CO2. Based on the Langmuir model to fit the limit adsorption amount, a-value can reach 41.774 cm3 g−1, 32.072 cm3 g−1, 38.457 cm3 g−1 at 303 K with the increase of Rmax. Studying the impact of coal slime on CO2 adsorption performance provides a theoretical basis for the subsequent preparation of energy storage materials and is of great significance for the safe, efficient and economic capture and sequestration of CO2, to alleviate the serious situation of the environment and realizing the dual-carbon goal.

Porous Carbon Electrode from Starch Soluble for Realizing High‐Performance Supercapacitor

AbstractOrganic potassium salts are the promising green activators for synthesizing porous carbon materials for energy storage. Herein, we report the synthesis of hierarchical porous carbon material derived from the mixture of soluble starch and ethylenediaminetetraacetic acid dipotassium salt dihydrate (EDTA‐2K) via carbonization and activation strategy. The sample is used as supercapacitors electrode, which exhibits superior mass specific capacitance (307.3 F g−1 at 1 A g−1), good rate performance (255.0 F g−1 at 10 A g−1), and excellent stability (retaining 83 % after 15000 cycles). This enhanced electrode performance is mainly due to the high specific surface area, the heteroatom co‐doping providing pseudo‐capacitance and the improved electronic conductivity. In addition, the asymmetric supercapacitor device shows a high energy density of 15 Wh kg−1 at the power density of 800 W kg−1 and capacitance retention of 90 % after 12000 cycles.