Energy Storage Mechanism Research Articles

Topochemical behavior of ferrocene embedded in V2O5·nH2O with weak hydrogen bonding enhancing ammonium-ion storage

Aqueous ammonium ion batteries (AAIBs) are garnering increasing attention due to their utilization of abundant resources, cost-effectiveness, safety, and unique energy storage mechanism. The pursuit of high-performance cathode materials has become a pressing issue. In this study, we propose and synthesize ferrocene-embedded hydrated vanadium pentoxide (Fer/VOH) for implementation in AAIBs. The inclusion of ferrocene serves to expand the interlayer spacing, mitigate interlayer forces, and introduce the electron-rich environment characteristic of ferrocene. This augmentation facilitates the creation of additional oxygen vacancies, substantially enhancing the capacity and efficiency of ammonium ion storage. Notably, our investigation reveals that the incorporation of ferrocene attenuates the hydrogen bonding interactions associated with ammonium ions, rendering them more amenable to the interlayer embedding and release processes. Building upon these advantages, Fer/VOH exhibits a specific capacity of 313 mAh/g at a current density of 0.2 A/g, representing the highest reported performance among vanadium oxides utilized in AAIBs to date. Even after 2000 charge/discharge cycles at a current density of 2 A/g, Fer/VOH maintains a reversible specific capacity of 89 mAh/g, with a capacity retention rate of 54.8%. This study confirms the viability of Fer/VOH as a cathode material for AAIBs and offers a novel approach to enhancing the electrical conductivity and diminishing the hydrogen bonding forces in vanadium oxide intercalation through the embedding of electron-rich species and positronic groups.

Boosting potassium and sodium-ion storage performance by in-situ self-assembly of a Co-based π-d conjugated coordination polymer on graphene nanosheets

To obtain anode materials with good electrochemical performances in both potassium ion batteries (PIBs) and sodium-ion batteries (SIBs), a Co-based π-d conjugated coordination polymer (Co-HHTP) is in-situ assembled on graphene (G) nanosheets using a facile one-step solvothermal method. The resulting Co-HHTP/G composite shows improved electrochemical performances over pure Co-HHTP. After 300 cycles of using as an anode of PIBs/SIBs for the first time, the reversible specific capacity of the Co-HHTP/G composite is found to be 381/277 mAh g−1 at 100 mA g−1. After undergoing 500 cycles at 1000 mA g−1, the material's reversible specific capacities remain at 234/164 mAh g−1 for PIBs/SIBs. The improved performances of the Co-HHTP/G composite electrode are due to the incorporation of graphene. This incorporation not only reduces structural stacking and promotes active site utilization, but also increases electrical conductivity and structural stability. According to the ex-situ X-ray photoelectron spectrometer (XPS) spectra, the Co-HHTP/G's energy storage mechanism throughout the process of potassisation/depotassisation is found to be linked to the aromatic rings presented in the organic ligands.

Molecular heat transport across a time-periodic temperature gradient.

The time-periodic modulation of a temperature gradient can alter the heat transport properties of a physical system. Oscillating thermal gradients give rise to behaviors such as modified thermal conductivity and controllable time-delayed energy storage that are not present in a system with static temperatures. Here, we examine how the heat transport properties of a molecular lattice model are affected by an oscillating temperature gradient. We use analytical analysis and molecular dynamics simulations to investigate the vibrational heat flow in a molecular lattice system consisting of a chain of particles connected to two heat baths at different temperatures, where the temperature difference between baths is oscillating in time. We derive expressions for heat currents in this system using a stochastic energetics framework and a nonequilibrium Green's function approach that is modified to treat the nonstationary average energy fluxes. We find that emergent energy storage, energy release, and thermal conductance mechanisms induced by the temperature oscillations can be controlled by varying the frequency, waveform, and amplitude of the oscillating gradient. The developed theoretical approach provides a general framework to describe how vibrational heat transmission through a molecular lattice is affected by temperature gradient oscillations.

Comprehensive Insights into Potassium‐Ion Capacitors: Mechanisms, Materials, Devices and Future Perspectives

AbstractAlkali metal‐ion capacitors integrate two electrodes from both batteries and supercapacitors (SCs), combining the advantages of large capacity, high‐rate performance, and long cycle life. Potassium (K) has similar properties to sodium (Na) and lithium (Li), however, the abundance of K in the crust is the same with Na, and much higher than Li. Due to the fast kinetics and low self‐discharge of Potassium‐ion capacitors (PICs), PICs attract more interest from researchers in the field of electrochemical energy storage. The current dilemma is that the research on PICs is more inherited from sodium‐ion capacitors (SICs) and lithium‐ion capacitors (LICs). Despite advancements in electrode materials, there is still a lack of profound understanding of the intrinsic issues and key challenges of PICs. In order to provide a detailed and systematic analysis of the development of PICs, in this review, special attention is given on the following Accordingly, full eight key sections: i) development history, ii) defining equations, iii) energy storage mechanism, iv) device configuration, v) electrode materials, vi) electrolyte design, vii) key technologies, and viii) future perspectives. This review provides an intensive theoretical foundation for the development of PICs and is able to pave the path for the practical application of PICs.

Fabrication of Polypyrrole Hollow Nanospheres by Hard-Template Method for Supercapacitor Electrode Material.

Conducting polymers like polypyrrole, polyaniline, and polythiophene with nanostructures offers several advantages, such as high conductivity, a conjugated structure, and a large surface area, making them highly desirable for energy storage applications. However, the direct synthesis of conducting polymers with nanostructures poses a challenge. In this study, we employed a hard template method to fabricate polystyrene@polypyrrole (PS@PPy) core-shell nanoparticles. It is important to note that PS itself is a nonconductive material that hinders electron and ion transport, compromising the desired electrochemical properties. To overcome this limitation, the PS cores were removed using organic solvents to create hollow PPy nanospheres. We investigated six different organic solvents (cyclohexane, toluene, tetrahydrofuran, chloroform, acetone, and N,N-dimethylformamide (DMF)) for etching the PS cores. The resulting hollow PPy nanospheres showed various nanostructures, including intact, hollow, buckling, and collapsed structures, depending on the thickness of the PPy shell and the organic solvent used. PPy nanospheres synthesized with DMF demonstrated superior electrochemical properties compared to those prepared with other solvents, attributed to their highly effective PS removal efficiency, increased specific surface area, and improved charge transport efficiency. The specific capacitances of PPy nanospheres treated with DMF were as high as 350 F/g at 1 A/g. And the corresponding symmetric supercapacitor demonstrated a maximum energy density of 40 Wh/kg at a power density of 490 W/kg. These findings provide new insights into the synthesis method and energy storage mechanisms of PPy nanoparticles.

Interfacial bonding enhances MXene/Sb2Se3 composites toward cyclic stability and fast aluminum storage

Metal-chalcogenides have been extensively studied as electrode materials for rechargeable ion batteries due to their high theoretical specific capacity and high abundance. Although promising, these materials face challenges related to slow electrochemical kinetics, pronounced structural distortions, and severe shuttle effects. These issues have seriously hindered the practical application of metal-chalcogenides in ion batteries. This work presents a novel approach to form interfacial binding bonds and in situ generation of antimony selenide (Sb2Se3) on MXene by electrostatic adsorption. This innovative strategy enhances the reversible capacity and cycling stability of Sb2Se3 and effectively improves the electrochemical kinetics and shuttle effect. Ex-situ characterization elucidates the distinctive energy storage mechanism of the Ti3C2/Sb2Se3 cathode and the inhibitory effect of MXene on the dissolution of reaction intermediates into the electrolyte. Additionally, the improvement in charge transfer and ion diffusion due to the introduction of MXene was validated through density functional theory calculations. This work offers new insights into enhancing the stability of metal-chalcogenides and understanding the energy storage mechanism of antimony-based selenides in ion batteries.

Insights into pseudocapacitive mechanism of aqueous ammonium-ion supercapacitors with exceptional energy density and cyclability

Aqueous ammonium-ion (NH4+) supercapacitors (AASCs) have recently garnered increased concerns but are consistently facing the challenge of lower energy density. Herein, a high-performance electrode (CuCo2S4@CP) with pseudocapacitive property has been synthesized and primordially applied to AASCs. The CuCo2S4@CP electrode has an ultrahigh specific capacity of 1512 C g−1 at 1 A g−1 and a distinguished cyclic stability of 87.74 % after 10,000 cycles. When the CuCo2S4@CP electrode is combined with the activated carbon (AC) negative electrode, the CuCo2S4@CP//AC device exhibits a high specific capacity of 547 C g−1 at 1 A g−1, excellent cycle stability (83.28 % at 10 A g−1), high energy density of 74.17 Wh kg−1, and excellent device consistency. In addition, the charge transfer mechanism of CuCo2S4@CP electrode in NH4+electrolyte has been elucidated. The CuCo2S4 surface density functional theory (DFT) elucidates that NH4+ has a minimal contribution to the surface, implying an insertion behavior of NH4+ within the CuCo2S4 lattice. Subsequent ex-situ characterization further confirms the energy storage process, revealing charge transfer to Co atoms following NH4+ insertion into CuCo2S4. The analysis of charge distribution illustrates an energy storage mechanism wherein the hydrogen bond formed between NH4+ and CuCo2S4 serves as the transport channel for charge transfer, facilitating the process of electrons from NH4+ to Co atoms. Therefore, the pseudocapacitive mechanism of CuCo2S4 with NH4+ provides a blueprint for sustainable energy storage with high energy density in aqueous electrolyte.

Possible crosstalk between the Arabidopsis TSPO-related protein and the transcription factor WRINKLED1

This study uncovers a regulatory interplay between WRINKLED1 (WRI1), a master transcription factor for glycolysis and lipid biosynthesis, and Translocator Protein (TSPO) expression in Arabidopsis thaliana seeds. We identified potential WRI1-responsive elements upstream of AtTSPO through bioinformatics, suggesting WRI1's involvement in regulating TSPO expression. Our analyses showed a significant reduction in AtTSPO levels in wri1 mutant seeds compared to wild type, establishing a functional link between WRI1 and TSPO. This connection extends to the coordination of seed development and lipid metabolism, with both WRI1 and AtTSPO levels decreasing post-imbibition, indicating their roles in seed physiology. Further investigations into TSPO's impact on fatty acid synthesis revealed that TSPO misexpression alters WRI1's post-translational modifications and significantly enhances seed oil content. Additionally, we noted a decrease in key reserve proteins, including 12 S globulin and oleosin 1, in seeds with TSPO misexpression, suggesting a novel energy storage strategy in these lines. Our findings reveal a sophisticated network involving WRI1 and AtTSPO, highlighting their crucial contributions to seed development, lipid metabolism, and the modulation of energy storage mechanisms in Arabidopsis.

Boosting interfacial reaction kinetics in yarn-shaped zinc-V2O5·nH2O batteries through carbon nanotube intermediate layer integration

Flexible yarn-shaped batteries are promising candidates for the wearable electronics owing to their good flexibility, tiny volume, compatibility with textiles. However, their practical applications are hindered by low capacity, active material mass loading, and energy density. Herein, we develop a coaxially wrapping strategy to fabricate an advanced yarn-shaped aqueous zinc-ion batteries (AZIBs) incorporating core-sheath carbon nanotube (CNT)/V2O5·nH2O composite yarns as cathodes and zinc wire as anodes. The as-wrapped CNT intermediate layer not only enhances the surface's conductivity, but the nano-array porous layer can also accelerate the mixing of ion concentration between the electrode surface and the electrolyte fluid through the turbulence effect, thereby improving the interfacial ion/electron kinetics. As a result, the energy storage mechanism of CNT/V2O5·nH2O yarn AZIBs transformed from capacitive-dominant to diffusion-controlled process, and the batteries demonstrate exceptional discharge capacity of 566.7 mAh g−1 at 0.1 A g−1, surpassing the state-of-art yarn-based AZIBs and approaching the theoretical zinc storage capacity (589 mAh g−1). In addition, they exhibit a high energy density of 471 Wh kg−1 at 25.5 W kg−1 and excellent cycling performance. This work opens a new and efficient avenue for the structure design of high-performance electrode materials for flexible yarn-based batteries.

Planning of wind-photovoltaic-storage-hydrogen-water for a zero-carbon microgrid on an independent island

Due to low daily demand and the remote location from the shoreline, diesel generators dominate the energy supply on these islands, resulting in significant emissions of harmful gases. In this paper, a collaborative planning approach is proposed for a zero-carbon microgrid incorporating wind turbines (WTs), photovoltaic modules (PVs), electrochemical energy storages(EESs), hydrogen energy storages(HESs), and sea water desalination on an independent island. Long-term and short-term energy storage mechanisms, represented by HESs and EESs, respectively, are coordinated to harness the abundant wind and solar energy resources. Additionally, consideration is given to the requirement for sea water desalination to achieve a self-sustained equilibrium of zero-carbon water and electricity for the island’s inhabitants. Illustrative analysis demonstrates that the proposed planning method accounts for the stability and environmental preservation in terms of the planning and operation. This has profound implications for advancing the transformation of the island’s microgrid energy infrastructure, enhancing the utilization of renewable energy, and bolstering the self-sustaining capacity of hydropower resources.

Integrated Simulation Research of Multi-natural Energy-driven Unmanned Surface Vehicle

In response to the limitations of existing unmanned surface vehicles in complex marine environments, where they often fail to meet the requirements for extended endurance, broad operational range, offshore missions, and prolonged operational durations, an autonomous Unmanned Surface Vehicle (NUSV) has been designed and developed. The NUSV is propelled by wind, solar, and wave energy sources. Concerning wind energy, a micro wind energy storage mechanism based on a spiral spring has been designed to enable power generation in low-wind conditions. A wave energy transmission device, complete with a dynamic model, has been devised for wave energy. This device converts torque generated from wave action in different directions into a unified torque, providing continuous power to drive the generator. Solar energy is harnessed using Maximum Power Point Tracking (MPPT) algorithms to ensure optimal operation of the solar panels. The electrical energy generated from these three natural sources is stored using Pulse Width Modulation (PWM) and DC-DC Boost converters. A programmable logic controller manages and allocates this stored electrical energy for the NUSV’s equipment, including underwater propulsion systems, surface cameras, laser radar, GPS, and other electronic devices. This integration of wind, solar, and wave energy sources enables the NUSV to meet power demands, allowing for long-duration operations at sea, extended offshore missions, wide operational ranges, and prolonged mission durations.

Interactions between chaperone and energy storage networks during the evolution of Legionella pneumophila under heat shock.

Waterborne transmission of the bacterium Legionella pneumophila has emerged as a major cause of severe nosocomial infections of major public health impact. The major route of transmission involves the uptake of aerosolized bacteria, often from the contaminated hot water systems of large buildings. Public health regulations aimed at controlling the mesophilic pathogen are generally concerned with acute pasteurization and maintaining high temperatures at the heating systems and throughout the plumbing of hot water systems, but L. pneumophila is often able to survive these treatments due to both bacterium-intrinsic and environmental factors. Previous work has established an experimental evolution system to model the observations of increased heat resistance in repeatedly but unsuccessfully pasteurized L. pneumophila populations. Here, we show rapid fixation of novel alleles in lineages selected for resistance to heat shock and shifts in mutational profile related to increases in the temperature of selection. Gene-level and nucleotide-level parallelisms between independently-evolving lineages show the centrality of the DnaJ/DnaK chaperone system in the heat resistance of L. pneumophila. Inference of epistatic interactions through reverse genetics shows an unexpected interaction between DnaJ/DnaK and the polyhydroxybutyrate-accumulation energy storage mechanism used by the species to survive long-term starvation in low-nutrient environments.

Design of dual carbon encapsulated porous micron silicon composite with compact surface for enhanced reaction kinetics of lithium-ion battery anodes

Developing high-performance composites with fast charging and superior cycle life is paramount for lithium-ion batteries (LIBs). Herein, we synthesized a double-shell carbon-coated porous structure composite with a compact surface (P-Si@rGO@C) using low-cost commercial micron-sized silicon (Si) instead of nanoscale silicon. Results reveal that the unique P-Si@rGO@C features high adaptability to volume expansion, accelerates electron/ion transmission rate, and forms a stable solid electrolyte interphase (SEI) film. This phenomenon arises from the synergistic effect of abundant internal voids and an external double-layer carbon shell with a dense surface. Specifically, the P-Si@rGO@C anode exhibits a high initial coulombic efficiency (ICE) (88.0 %), impressive rate-capability (612.1 mAh/g at 2C), and exceptional long-term cyclability (972.2 mAh/g over 500 cycles at 0.5C). Further kinetic studies elucidate the diffusion-capacitance hybrid energy storage mechanism and reveal an improved Li+ diffusion coefficient (from 3.47 × 10-11 to 2.85 × 10-9 cm2 s-1). Ex-situ characterization confirms the crystal phase change of micron-sized Si and the formation of a stable LiF-rich SEI. Theoretical calculations support these findings by demonstrating an enhancement in the adsorption ability of Si to Li+ (from -0.89 to -0.97 eV) and a reduction in the energy migration barrier (from 0.35 to 0.18 eV). Additionally, practical LixSi powder is shown to increase the ICE of full cells from 67.4 % to 87.9 %. Furthermore, a pouch cell utilizing the prelithiated P-Si@rGO@C anode paired with LiNi1/3Co1/3Mn1/3O2 (NCM111) cathode delivers a high initial reversible capacity of 7.2 mAh and 76.8 % capacity retention after 100 cycles. This work provides insights into the application of commercial silicon-aluminum alloy powder in the anode of high-energy LIBs.

Highly stable MXene/g-PPy@sulfonated cellulose composite electrodes for flexible supercapacitors

Traditional two-dimensional transition metal carbides/nitrides (MXene) have gained much academic concern due to their excellent physicochemical properties, but their susceptibility to self-stacking leads to poor cyclic stability. In this paper, an MXene-based electrode active material was successfully prepared. The generated modified PPy (g-PPy) increases the active site, increases the accessibility of ions, and can give full play to the pseudocapacitance. By the combination of modified PPy (g-PPy) nanoparticles with pseudocapacitive behavior polymerized in situ on sulfonated cellulose (SC) and MXene, not only the electrochemical performance was improved by exploiting the synergy between different electrode materials and different energy storage mechanisms, but also the MXene as a skeleton limited the volume expansion and contraction of PPy during charge/discharge cycles and the g-PPy and SC composites (g-PPy@SC) as a spacer supported the MXene layer, resulting in much higher cycle stability. Cycle stability of 98.4 % even after 10,000 cycle tests. In addition, a symmetric supercapacitor assembled from this electrode material maintains a stability of 84.4 % under 10,000 cycles at a low temperature of −40 °C. Therefore, this study provides a feasible method for the preparation of MXene-based electrodes with high cycling stability.

One-Step Construction of Closed Pores Enabling High Plateau Capacity Hard Carbon Anodes for Sodium-Ion Batteries: Closed-Pore Formation and Energy Storage Mechanisms.

Closed pores play a crucial role in improving the low-voltage (<0.1 V) plateau capacity of hard carbon anodes for sodium-ion batteries (SIBs). However, the lack of simple and effective closed-pore construction strategies, as well as the unclear closed-pore formation mechanism, has severely hindered the development of high plateau capacity hard carbon anodes. Herein, we present an effective closed-pore construction strategy by one-step pyrolysis of zinc gluconate (ZG) and elucidate the corresponding mechanism of closed-pore formation. The closed-pore formation mechanism during the pyrolysis of ZG mainly involves (i) the precipitation of ZnO nanoparticles and the ZnO etching on carbon under 1100 °C to generate open pores of 0.45-4 nm and (ii) the development of graphitic domains and the shrinkage of the partial open pores at 1100-1500 °C to convert the open pores to closed pores. Benefiting from the considerable closed-pore content and suitable microstructure, the optimized hard carbon achieves an ultrahigh reversible specific capacity of 481.5 mA h g-1 and an extraordinary plateau capacity of 389 mA h g-1 for use as the anode of SIBs. Additionally, some in situ and ex situ characterizations demonstrate that the high-voltage slope capacity and the low-voltage plateau capacity stem from the adsorption of Na+ at the defect sites and Na-cluster formation in closed pores, respectively.

Boosting the Energy Density of Bowl-Like MnO2@Carbon Through Lithium-Intercalation in a High-Voltage Asymmetric Supercapacitor with "Water-In-Salt" Electrolyte.

Highly concentrated "'water-in-salt"' (WIS) electrolytes are promising for high-performance energy storage devices due to their wide electrochemical stability window. However, the energy storage mechanism of MnO2 in WIS electrolytes-based supercapacitors remains unclear. Herein, MnO2 nanoflowers are successfully grown on mesoporous bowl-like carbon (MBC) particles to generate MnO2/MBC composites, which not only increase electroactive sites and inhibit the pulverization of MnO2 particles during the fast charging/discharging processes, but also facilitate the electron transfer and ion diffusion within the whole electrode, resulting in significant enhancement of the electrochemical performance. An asymmetric supercapacitor, assembled with MnO2/MBC and activated carbon (AC) and using 21m LiTFSI solution as the WIS electrolyte, delivers an ultrahigh energy density of 70.2Whkg-1 at 700W kg-1, and still retains 24.8Whkg-1 when the power density is increased to 28kWkg-1. The ex situ XRD, Raman, and XPS measurements reveal that a reversible reaction of MnO2 + xLi+ + xe-↔LixMnO2 takes place during charging and discharging. Therefore, the asymmetric MnO2/MBC//AC supercapacitor with LiTFSI electrolyte is actually a lithium-ion hybrid supercapacitor, which can greatly boost the energy density of the assembled device and expand the voltage window.

Fabrication of MnO2@Porous Carbons with High Energy and Power Density and Their Application in Supercapacitors

MnO2@PCs (porous carbons) exhibiting high energy and power density are utilized as supercapacitor electrodes and prepared by impregnating porous carbons (PCs) derived from coal tar pitch (CTP) with KMnO4 as the manganese source. This study systematically investigates the impact of MnO2 loading on the microstructure and electrochemical performance in sample. It is found that the specific surface areas (SSA) of all MnO2@PCs significantly reduced compared to that of the PCs 2789 m2 g−1. The suggested mechanism might be a combination of the energy storage mechanism of dual layer capacitors with pseudo‐capacitance due to redox reactions of MnO2. Notably, MnO2@PCs‐0.0075 exhibits a maximum SSA of 1454.62 m2 g−1. Its specific capacitance reached 561 F g−1 at 0.5 A g−1, while the capacitance of the PCs increased by 81.5% to 309 F g−1. Remarkably, the Coulombic efficiency remained at 100%. The power density and energy density are determined in a two‐electrode test system to be 0.5 kW kg−1 and 58.01 Wh kg−1, respectively, at 0.5 A g−1. Concluding from these results and related literature, the MnO2 content significantly influences the electrochemical performance, suggesting that MnO2@PCs‐0.0075 could be a promising supercapacitor (SC) electrode material, provided its capacitance retention is enhanced.

Scalable molten salt strategy synthesis of large-size 2D MoS2(1-x)Se2x alloy for boosting potassium-ion storage performance

Owing to the lamellar structure and large theoretical specific capacity, transition metal dichalcogenides (TMDs) are promising anodes for potassium ion batteries (KIBs). However, the development and application of TMDs are greatly confined by the inferior conductivity and structure integrity. Herein, a two-dimensional (2D) MoS2(1-x)Se2x ternary alloy supported by carbon nanosheets (MoS2(1-x)Se2x/C) is designed to boost their electrochemical performance in KIBs. Owing to the unique 2D structure, the assistance of carbon, as well as the synergistic effect of S and Se, the MoS2(1-x)Se2x/C gets many obvious merits as: abundant K+ diffusion path, enhanced structure stability and improved conductivity. Thus, our designed MoS2(1-x)Se2x/C obtains the high reversible capacity (279.93 mAh/g at 0.2 A/g), excellent rate performance and long-cycling capability for KIBs. Even cycling for 500 times at the high current density of 1 A/g, a large reversible capacity of 257.94 mAh/g is kept. Moreover, the energy storage mechanisms of MoS2(1-x)Se2x during potassiation and depotassiation process are revealed. Our work provides a new insight into the modification of TMDs anode for potassium ion batteries.

Potassium-Hydrogen Hybrid Ion Alkaline Battery: A New Rechargeable Aqueous Battery Combined a K+ Storage Cathode and an Electrochemical Hydrogen Storage Anode.

A rechargeable aqueous hybrid ion alkaline battery, using a proton and a potassium ion as charge carriers for the anode and cathode, respectively, is proposed in this study by using well-developed potassium nickel hexacyanoferrate as the cathode material and mesoporous carbon sheets as the anode material, respectively. The constructed battery operates in a concentrated KOH solution, in which the energy storage mechanism for potassium nickel hexacyanoferrate involves the redox reaction of Fe2+/Fe3+ associated with potassium ion insertion/extraction and the redox reaction of Ni(OH)2/NiOOH. The mechanism for the carbon anode is electrochemical hydrogen storage. The cathode made of potassium nickel hexacyanoferrate exhibits both an ultrahigh capacity of 232.7 mAh g-1 under 100 mA g-1 and a consistent performance of 214 mAh g-1 at 2000 mA g-1 (with a capacity retention of 92.8% after 200 cycles). The mesoporous carbon sheet anode exhibits a capacity of 87.6 mAh·g-1 at 100 mA g-1 with a good rate and cyclic performance. The full cell provides an operational voltage of 1.55 V, a capacity of 93.6 mAh g-1 at 100 mA g-1, and 82.4% capacity retention after 1000 cycles at 2000 mA g-1 along with a low self-discharge rate. The investigation and discussion about the energy storage mechanisms for both electrode materials are also provided.

In situ nitrogen-doped into MnO2/carbon derived from manganese (II) – triazole framework to achieve superior zinc ions storage

The widespread application of MnO2 as cathodes for aqueous zinc ions batteries (AZIBs) suffers from challenging issues of inferior ion storage capability, poor intrinsic electronic conduction and undesirable Mn dissolution. Herein, we demonstrate that the nitrogen can be successfully in situ doped into both the MnO2 and carbon lattice to form N-doped MnO2/C (NMC) by pyrolyzing the Mn based metal-triazole (Mn-MET) framework. The generation of oxygen vacancies in MnO2 and the presence of N-doped carbon in the composite not only increase the electronic conductivity to accelerate charges transfer in MnO2, but also relieve the Mn dissolution to stabilize the MnO2 structure. As a result, the NMC cathode based AZIB is able to display high discharge capacity of 339.3 mAh g−1, much higher than the bare Mn2O3 cathode (147.8 mAh g−1). The excellent long-term cycling life with a capacity retention of 82.8 % can be also achieved after 1000 cycles under 3 A g−1. The energy storage mechanism of the NMC cathode related to the reversible H+ and Zn2+ interaction/extraction are systematically investigated through multiple ex situ characterizations. Thus, these inspiring results in our work are expected to stimulate the exploitation of MOFs derived cathode materials for high-performance AZIBs.