Electrochemical Energy Storage for Green Grid

A Copolymer of Benzoquinone and Pyrrole as High Rate, Durable Polymer Electrode for Aqueous Zn- and Mg-Ion Based Batteries

The growing energy demands have led to an increased attention towards the development of efficient energy storage devices. In this direction, aqueous rechargeable batteries have attracted considerable attention due to their affordability, environmental friendliness and quite importantly, safety. In the present studies, a two-dimensional copolymer of benzoquinone and pyrrole that is insoluble in aqueous solutions is explored as an electrode for aqueous, rechargeable divalent ion storage. The polymer exhibits high capacity, long cycle life and lends itself amenable for high rates of discharge/charge. It reveals a stable capacity of 125 mAh/g at a high current density of 1 A/g in the case of zinc ion batteries while a stable capacity of 75 mAh/g at 1 A/g is observed in the case of aqueous magnesium ion battery. Electrochemical studies reveal contributions due to capacitive storage of the 2-dimensional polymer. The charge storage mechanism due to the involvement of carbonyl groups is deciphered using spectroscopic techniques.

Understanding the Solution-Phase Catalysis Process inside the Li-O2 Battery Using Redox Mediator─Butylated Hydroxytoluene

The redox mediators help prevent cathode passivation and promote the formation and decomposition of Li2O2 within the electrolyte of the battery. Understanding the mechanistic properties of the soluble catalyst from an atomic level is crucial for developing an all-in-one multifunctional soluble catalyst for Li-O2 batteries. With the help of density functional theory and atom-centered density matrix propagation molecular dynamics simulations, we report how butylated hydroxytoluene (BHT), an experimentally reported soluble catalyst, mediates the stabilization of reactive intermediates and the mechanism behind the formation and decomposition of Li2O2. The hydroxy group in BHT facilitates the stabilization of O2•- via hydrogen bonding and the solvation of Li+, LiO2•, and Li2O2. This characteristic of BHT helps to promote the solution-phase mechanism and suppress parasitic reactions induced by O2•-. During the charging process, the reversibility of BHT and BHT•+ happens and the disappearance of the hydrogen bonding interaction facilitates the delithiation process. The Mulliken charge distribution analysis shows that the reversibility of BHT and BHT•+ is due to the electron delocalization between the oxygen atom and benzene ring of BHT. We observe the two benefits of the hydrogen bond: the presence and absence of hydrogen bonding enhance the formation and decomposition of Li2O2, respectively. We find that tetraethylene glycol dimethyl ether solvent plays a significant role in stabilizing lithium-oxygen-containing species such as LiO2• and Li2O2. However, the presence of BHT further improves the results. This finding highlights the cooperative activity of BHT in conjugation with the tetraethylene glycol dimethyl ether solvent. The atom-centered density matrix propagation method reveals that BHT facilitates Li2O2 decomposition through protonation, whereas BHT•+ induces Li2O2 decomposition by promoting the formation of LiO2• and the BHT:Li+ complex without transferring the proton.

Mechanism guided two-electron energy storage for redox-flow batteries using nickel bis(diphosphine) complexes

The storage of multiple electrons per molecule can greatly enhance the energy density of redox-flow batteries (RFBs). Here, we show that nickel bis(diphosphine) complexes efficiently store multiple electrons through either sequential 1e- redox waves or a concerted 2e- redox wave, depending on their coordination environment. Mechanistic studies comparing ligand sterics (-Me vs. -Ph) and coordination of monodentate ligands (MeCN vs. Cl-) allow for selective control of the electron transfer pathway, steering electron storage toward the more favorable 2e- wave. Continuous charge-discharge cycling experiments show more negative charge-discharge potentials and improved capacity retention in the presence of Cl-, thus improving the energy storage of nickel bis(diphosphine) complexes as anolytes in RFBs. This work shows how mechanistic understanding of 2e- redox cycles for transition metal complexes can create new opportunities for multi-electron storage in RFBs.

Nanomaterials for Energy Storage Systems-A Review

The ever-increasing global energy demand necessitates the development of efficient, sustainable, and high-performance energy storage systems. Nanotechnology, through the manipulation of materials at the nanoscale, offers significant potential for enhancing the performance of energy storage devices due to unique properties such as increased surface area and improved conductivity. This review paper investigates the crucial role of nanotechnology in advancing energy storage technologies, with a specific focus on capacitors and batteries, including lithium-ion, sodium-sulfur, and redox flow. We explore the diverse applications of nanomaterials in batteries, encompassing electrode materials (e.g., carbon nanotubes, metal oxides), electrolytes, and separators. To address challenges like interfacial side reactions, advanced nanostructured materials are being developed. We also delve into various manufacturing methods for nanomaterials, including top-down (e.g., ball milling), bottom-up (e.g., chemical vapor deposition), and hybrid approaches, highlighting their scalability considerations. While challenges such as cost-effectiveness and environmental concerns persist, the outlook for nanotechnology in energy storage remains promising, with emerging trends including solid-state batteries and the integration of nanomaterials with artificial intelligence for optimized energy storage.

Unraveling Cu2+ Ion Intercalation-Based V3O7·H2O Cathode to Drive Ultrahigh-Rate Aqueous Zinc-Ion Batteries

Vanadium-based cathode materials have attracted significant interest owing to their high theoretical capacities (>300 mA h g-1), versatile electrochemical ion insertions, and high valence states. However, their poor electrical conductivities and dissolution in electrolytes have hindered the development of grid energy storage systems. To address these issues, Cu2+ ion-doped V3O7·H2O (CuVO-2) cathode materials prepared via a one-step hydrothermal method were used to solve the aforementioned problems. The as-prepared CuVO-2 offered ample space for rapid ion transport, enabling a high reversible capacity of 444.8 mA h g-1 at 0.1 A g-1, excellent rechargeability of up to 5000 cycles at 5 A g-1 with a Coulombic efficiency (CE) of 84.4%, and an acceptable energy density of 302.65 W h kg-1. To better understand the storage mechanism of CuVO-2, several characterizations were conducted, including ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), which helped elucidate the intercalation mechanism of the developed cathode materials. These findings offer valuable insights into the design of stable V-based cathode materials for next-generation aqueous zinc-ion batteries (AZIBs).

A Long-Life Zinc-Bromine Single-Flow Battery Utilizing Trimethylsulfoxonium Bromide as Complexing Agent

Aqueous zinc-bromine single-flow batteries (ZBSFBs) are highly promising for distributed energy storage systems due to their safety, low cost, and relatively high energy density. However, the limited operational lifespan of ZBSFBs poses a significant barrier to their large-scale commercial viability. Here, trimethylsulfoxonium bromide (TMSO), a nonquaternary ammonium salt, is introduced as a bromine complexing agent to extend the cycle life of ZBSFBs by reducing the imbalance of active substances. Benefiting from the strong interaction between TMSO and H2O, the hydrogen evolution reaction is notably suppressed compared with the traditional N-ethyl-N-methyl-pyrrolidinium bromide (MEP) complexing agent, resulting in reduced bromine accumulation at the cathode. The resultant solid polybromide-TMSO complex, featuring rapid electrochemical redox reaction of Br2/Br-, further contributes to reduce the residual bromine. Consequently, the ZBSFB with TMSO demonstrates a longer lifespan of 1500 cycles with a higher average energy efficiency (EE) of ≈81.6% than that with MEP (less than 300 cycles with an average EE of ≈80.2%). This research explores a sulfonium complexing agent and provides a feasible strategy to effectively extend the cycle life of ZBSFBs.

All-natural charge gradient interface for sustainable seawater zinc batteries

Paring seawater electrolyte with zinc metal electrode has emerged as one of the most sustainable alternative solutions for offshore stationary energy storages owing to the intrinsic safety, extremely low cost, and unlimited water source. However, it remains a substantial challenge to stabilize zinc metal negative electrode in seawater electrolyte, given the presence of chloride ions and complex cations in seawater. Here, we reveal that chloride pitting initiates negative electrode corrosion and aggravates dendritic deposition, causing rapid battery failure. We then report a charge gradient negative electrode interface design that eliminates chloride-induced corrosion and enables a sustainable zinc plating/stripping performance beyond 1300 h in natural seawater electrolyte at 1 mA cm-2/1 mAh cm-2. The gradually strengthened negative charges formed via diffusion-controlled electrostatic complexation of biomass-derived polysaccharides serve to repel the unfavorable accumulation of chloride ions while simultaneously accelerating the diffusion of zinc ions. The seawater-based Zn | |NaV3O8·7H2O cell delivers an initial areal discharge capacity of 5 mAh cm-2 and operates over 500 cycles at 500 mA g-1.

The Negative Role of Proton Insertion on the Lifetime of Vanadium-Based Aqueous Zinc Batteries

Vanadium oxides are attracted cathodes for aqueous zinc batteries owing to their high capacity. However, the limited cyclability of vanadium-based oxide cathodes, especially at low current densities, impedes their practical application. Here, it is revealed that proton insertion is responsible for the limited lifetime of vanadium oxides. Proton insertion promotes the dissolution of vanadium oxides, deteriorating electrochemical performance. Propylene carbonate (PC) is introduced into Zn(CF3SO3)2 electrolyte to regulate the coordination environment of water, forming PC-coordinated Zn2+ solvation structure and [H2O-CF3SO3 --PC] complex. The optimized coordination environment of water weakens the adsorption energy between water molecules and vanadium oxides, inhibiting proton insertion. As a result, vanadium-based oxides cathode without proton insertion can maintain the stability of crystal structure and avoid the dissolution of V. Taking CaV8O20·nH2O as cathode, Zn||CaV8O20·nH2O battery without proton insertion performs enhanced cycling performance. This work not only reveals the negative effect of proton insertion on the lifetime of vanadium-based oxides cathode but also provides an effective strategy to modulate proton insertion.

Hyper-Cross-Linked Polymer-Derived Carbon-Coated Fe-Ni Alloy/CNT as a Bifunctional Electrocatalyst for Rechargeable Zinc-Air Batteries

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are considered to be the most important processes in metal-air batteries and regenerative fuel cell devices. Metal-organic polymers are attracting interest as promising precursors of advanced metal/carbon electrocatalysts because of their hierarchical porous structure along with the integrated metal-carbon framework. We developed carbon-coated CNTs with Ni/Fe and Cu/Fe as active sites. Experimental observations from X-ray photoelectron spectroscopy and X-ray absorption analysis suggest that C@CNT[Ni] outperforms C@CNT[Cu] in the ORR and OER, which is further supported by density functional theory calculations. C@CNT[Ni] exhibits a higher onset potential (0.99 V vs RHE) and a smaller Tafel slope (40.2 mV decade-1) compared to those of C@CNT/[Cu] in an alkaline electrolyte (0.94 V vs RHE and 46.5 mV decade-1, respectively). Such circumstances are attributed to the alloying effect between Ni and Fe in C@CNT[Ni], in contrast to the existing copper iron oxide phase in C@CNT/[Cu]. It is noteworthy that C@CNT[Ni] also displayed an improved OER, demanding its bifunctional property. As a proof of concept, C@CNT[Ni] was utilized in zinc-air batteries, which shows a high energy efficiency of ∼60%, a small charge-discharge voltage gap of 0.78 V, and excellent cycling performance (∼120 h) at 5 mA cm-2 and 25 °C. This protocol expands the utility of novel metal-organic hyper-cross-linked polymer-derived bimetallic electrocatalysts for clean energy research.

Manganese Intercalation Enabling High-Performance Aqueous Fe-VO2 Batteries

The aqueous iron ion batteries (AIIBs) are an attractive option for large-scale energy storage applications. However, the inadequate plating and stripping of Fe2+ ions underscore the need to explore more suitable cathode materials. Herein, we optimize the structure of tunnel-like VO2 nanosheets by introducing Mn2+ ion intercalation as a cathode material to enhance their performance in AIIBs. Mn2+ serves as a stabilizing pillar for VO2, which brings some oxygen vacancies to provide extra electrochemically active sites, and accelerates the reversible (de)insertion of Fe2+ ions. In addition, the density functional theory (DFT) calculations show that the introduction of Mn2+ reduces the band gap of VO2 and also decreases the electrostatic interaction between Fe2+ and VO2. Consequently, the VO2 with interlayer Mn2+ pillars (5% MVO) electrodes exhibit a remarkable capacity of 284.32 mAh g-1 at a current density of 0.1 A g-1 and demonstrate excellent cycle life, maintaining 81.7% of their capacity at 1.0 A g-1 after 600 cycles. Therefore, these results offer a promising choice for the cathode material to achieve outstanding electrochemical performance in AIIBs.

The Critical Role of Atomic-Scale Polarization in Transition Metal Oxides on Vanadium-Redox Electrochemistry

Transition metal oxide electrocatalysts (TMOEs) are poised to revive grid-scale all-vanadium redox flow batteries (VRFBs) due to their low-cost and unique electronic properties, while often inescapably harboring surface vacancies. The role of local vacancy-induced physicochemical properties on vanadium-redox electrochemistry (VRE), encompassing kinetics, and stability, remains profoundly unveiled. Herein, for the first time, it is revealed that vacancies induce atomic-scale polarization in TMOEs and elucidate its mechanism in VRE. Attributable to local polarization, particularly by cation vacancy, the activated nearest-coordinated Mn sites prominently augment the adsorption competence of the V2+/V3+ couple and expedite its round-tripping by forming an intermediate *Mn-O-V bridge. It is also affirmed that the anion vacancies are vulnerable to microstructure reconfiguration by feeble hydroxyl adsorption and thus performance degradation over long-term cycling, in contrast to cation vacancies. Accordingly, the VRFB employing cation-vacancy-functionalized electrode delivers an energy efficiency of 80.8% and a reliable 1000-cycle lifespan with a negligible decay of 0.57% per cycle at 300 mA cm-2, outclassing others. The findings shed light on the fundamental rules governing the utility and evolution of vacancies in TMOEs, thereby moving a step closer toward their deployment in a wide range of sustainable energy storage schemes.

Balancing pH and Pressure Allows Boosting Voltage and Power Density for a H2-I2 Redox Flow Battery

The decoupled power and energy output of a redox flow battery (RFB) offers a key advantage in long-duration energy storage, crucial for a successful energy transition. Iodide/iodine and hydrogen/water, owing to their fast reaction kinetics, benign nature, and high solubility, provide promising battery chemistry. However, H2-I2 RFBs suffer from low open circuit potentials, iodine crossover, and their multiphase nature. We demonstrate a H2-I2 operation with a combined neutral-pH catholyte (I3 -/I-) and an alkaline anolyte (KOH), producing an open circuit cell voltage of 1.28 V. Additionally, we incorporate a pressure-balanced gas diffusion electrode (GDE) to mitigate mass transport limitations at the anode. These improvements result in a maximum power density of 230 W/m2 when allowing a mild breakthrough of H2 through the GDE. While minimal crossover occurs, side reactions of permeating active species were found reversible, enabling long-term operation. Future work should address the stability of the GDE and optimization of the electrolyte thickness and concentration to fully leverage the potential unlocked by balancing the pressure and pH in the H2-I2 RFB.

A Mechanistic Insight into the Acidic-stable MnSb2O6 for Electrocatalytic Water Oxidation

The abundant, active, and acidic-stable catalysts for the oxygen evolution reaction (OER) are rare to proton exchange membrane-based water electrolysis. Mn-based materials show promise as electrocatalysts for OER in acid electrolytes. However, the relationship between the stability, activity and structure of Mn-based catalysts in acidic environments remains unclear. In this study, phase-pure MnSb2O6 was successfully prepared and investigated as a catalyst for OER in a sulfuric acid solution (pH of 2.0). A comprehensive mechanistic comparison between MnSb2O6 and Mn3O4 revealed that the rate-determining step for OER on MnSb2O6 is the direct formation of MnIV=O from MnII-H2O by the 2H+/2e- process. This process avoids the rearrangement of adjacent MnIII intermediates, leading to outstanding stability and activity.

Building Robust Manganese Hexacyanoferrate Cathode for Long-Cycle-Life Sodium-Ion Batteries

Manganese Hexacyanoferrate (Mn─HCF) is a preferred cathode material for sodium-ion batteries used in large-scale energy storage. However, the inherent vacancies and the presence of H2O within the imperfect crystal structure of Mn─HCF lead to material failure and interface failure when used as a cathode. Addressing the challenge of constructing a stable cathode is an urgent scientific problem that needs to be solved to enhance the performance and lifespan of these batteries. In this review, the crystal structure of Mn─HCF is first introduced, explaining the formation mechanism of vacancies and exploring the various ways in which H2O molecules can be present within the crystal structure. Then comprehensively summarize the mechanisms of material and interfacial failure in Mn─HCF, highlighting the key factors contributing to these issues. Additionally, eight modification strategies designed to address these failure mechanisms are encapsulated, including vacancy regulation, transition metal substitution, high entropy, the pillar effect, interstitial H2O removal, surface coating, surface vacancy repair, and cathode electrolyte interphase reinforcement. This comprehensive review of the current research advances on Mn─HCF aims to provide valuable guidance and direction for addressing the existing challenges in their application within SIBs.

A Bifunctional Iron-Nickel Oxygen Reduction/Oxygen Evolution Catalyst for High-Performance Rechargeable Zinc-Air Batteries

Efficient and robust electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial for fuel cells, metal-air batteries, and other energy technologies. Here, a highly stable, efficient bifunctional OER/ORR electrocatalyst (FeNi-NC@MWCNTs) is reported and demonstrated its integration and robust performance in an aqueous Zinc-air battery (ZAB). The catalyst is based on neighboring iron/nickel sites (FeNiN6) which are atomically dispersed on porous nitrogen-doped carbon particles. The particles are wrapped in electrically conductive multi-walled carbon nanotubes for enhanced electrical conductivity. Electrocatalytic analyses show high OER and ORR performance (OER/ORR voltage difference = 0.69 V). Catalyst integration in a ZAB results in excellent performance metrics, including an open circuit voltage of 1.44 V, a specific capacity of 782 mAh g-1 (at j = 15 mA cm-2), a peak power density of 218 mW cm-2 (at j = 260 mA cm-2) and long-term durability over 600 charge/discharge cycles. Combined experimental and theoretical (density functional theory) analyses provide an in-depth understanding of the physical and electronic structure of the catalyst and the role of the FeNi dual atom reaction site. The study therefore provides critical insights into the structure and reactivity of high-performance bifunctional OER/ORR catalysts based on atomically dispersed non-critical metals.

Disodium Malate Electrolyte Additive Facilitates Dendrite-Free Zinc Anode: Deposition Kinetics and Interface Regulation

Due to the presence of H2O within the solvated sheath of [Zn(H2O)6]2+ as well as reactive free water in the electrolyte bulk phase, the extended cycling of aqueous zinc-ion batteries (AZIBs) is significantly affected by detrimental side reactions and the growth of Zn dendrites. This study significantly enhances the long-term cycling stability of AZIBs by introducing a small amount of disodium malate (DM) into a 2 m ZnSO4 electrolyte solution. DM involvement in the solvation sheath of Zn2+ reduces the desolvation energy of Zn2+, thereby mitigating the corrosion and hydrogen evolution reaction (HER) of the negative electrode surface by [Zn(H2O)6]2+ ions. Additionally, DM adsorption on the zinc surface retards the reduction kinetics of Zn2+ at anode, promoting uniform distribution and predominant deposition on the flat (002) crystal plane, thus reducing dendrite formation. The assembled Zn||Zn symmetric cell exhibits stable cycling for over 500 h at 10 mA cm-2 and 5 mAh cm-2. The Zn||VO2 full cells with DM additive exhibits an ultralong cycling lifespan without capacity loss.

Boosting the Charge Storage Capability of Bi2TeO5 Cathode Using Iodide Ions in Aqueous Zinc-Based Batteries System

As insertion-type cathode materials of aqueous Zn-based batteries (ABs), bismuth chalcogenides/oxychalcogenides exhibits relatively limited capacities in ZnSO4 baseline electrolyte. This work finds that Bi2TeO5 (BTO) cathode with pre-added I- electrolyte additive can simultaneously achieve conversion and insertion chemistries, which enables aqueous BTO-Zn batteries to deliver an extraordinary electrochemical performance. As shown in the experiment results, the BTO cathode showcases an ultrahigh specific capacity of 534.9 mA h g-1 at 0.5 A g-1, excellent rate capability (237.3 mA h g-1 at 10 A g-1). In the estimation of cyclic durability, the capacity of the BTO cathode decreases from 271.2 to 171.1 mA h g-1 during 2000 cycles at 10 A g-1.

Advancements and Applications of Conjugated Polyelectrolytes and Conjugated Oligoelectrolytes in Bioanalytical and Electrochemical Contexts

In the past decade, conjugated oligoelectrolytes (COEs) and conjugated polyelectrolytes (CPEs) have emerged at the forefront of active materials in bioanalytical and electrochemical settings due to their unique electronic and ionic properties. These materials possess π-conjugated backbones with ionic functionalities at the ends of their side chains, granting them water solubility and facilitating their processability, exploration, and applications in aqueous environments. In this perspective, the basis for evaluating their figures of merit in selected bioanalytical and electrochemical contexts will be provided and contextualized. We will primarily discuss their roles in biosensing, bioimaging, bioelectrosynthesis, and electrochemical contexts, such as organic electrochemical transistors (OECTs), microbial fuel cells (MFCs), and their use as charge-storing materials. Emphasis will be placed on their role in improving efficiency and utility within these applications. We will also explore the fundamental mechanisms that govern their behavior and highlight innovative strategies and perspectives for developing the next generation of CPEs and COEs for bioanalytical and electrochemical applications and their integration into practical devices.

Ultrafast Joule Heating Modification of Methane-Pyrolyzed Carbon Black for Supercapacitor Application

Carbon black from methane pyrolysis for hydrogen is an alternative resource and can be improved for conductive material supplication. Our current work uses an ultrafast Joule heating technique to modify the methane-pyrolyzed carbon black and prepare nanoparticles of electrode material for supercapacitor application, coupled with density functional theory, structural, and electrochemical analyses. Evolution rules of the carbon and pore structures of the modified sample with an increase in temperature reveal good structure improvements. The graphitization degree of modified carbon black nanoparticles increases, and the particle morphology changes from a smooth surface, disordered structure removal, and pore formation to graphite crystallization. Band structure and state density analytical results show that the modified carbon black with a defect-free structure possesses metallic properties and exhibits good electrical conductivity. A temperature around 1576 °C to the initial graphitization was defined based on the critical point of the evolution of ordered and disordered structures, while the electrical conductivity of the carbon black nanoparticles at 2000 °C reaches 2300 S/m. The modified carbon black performed with stable charge/discharge characteristics, exhibiting a 4.31% capacitance drop at a current load of 2 A/g and a 18.31% capacitance drop at a current load of 20 A/g.

Averting H+-Mediated Charge Storage Chemistry Stabilizes the High Output Voltage of LiMn2O4-Based Aqueous Battery

H+ co-intercalation chemistry of the cathode is perceived to have damaging consequences on the low-rate and long-term cycling of aqueous zinc batteries, which is a critical hindrance to their promise for stationary storage applications. Herein, the thermodynamically competitive H+ storage chemistry of an attractive high-voltage cathode LiMn2O4 is revealed by employing operando and ex-situ analytical techniques together with density functional theory-based calculations. The H+ electrochemistry leads to the previously unforeseen voltage decay with cycling, impacting the available energy density, particularly at lower currents. Based on an in-depth investigation of the effect of the Li+ to Zn2+ ratio in the electrolyte on the charge storage mechanism, a purely aqueous and low-salt concentration electrolyte with a tuned Li+/Zn2+ ratio is introduced to subdue the H+-mediated charge storage kinetically, resulting in a stable voltage output and improved cycling stability at both low and high cathode loadings. Synchrotron X-ray diffraction analysis reveals that repeated H+ intercalation triggers an irreversible phase transformation leading to voltage decay, which is averted by shutting down H+ storage. These findings unveiling the origin and impact of the deleterious H+-storage, coupled with the practical strategy for its inhibition, will inspire further work toward this under-explored realm of aqueous battery chemistry.

Metal alkoxides: A new type of reversible anode materials for stable and high-rate lithium-ion batteries

Metal-organic compounds have attracted significant attention for lithium-ion battery (LIB) anodes. However, their practical application is severely hindered by the poor structural stability and sluggish Li+ reaction kinetics. Herein, we proposed a new type of metal-organic compound, metal alkoxides, for high-performance LIBs. A series of metal-alkoxide/graphene composites with different transition metal centers and alkoxide anions are prepared to investigate the structural stability, Li-storage ability, and Li+ diffusion kinetics. The results reveal that the metal centers and alkoxide anions have significant influence on the structural stability, molar mass, and electronic structures, which are highly related to the Li-storage performance. Among them, Co-EG/rGO (EG represents the ethylene glycol anion) delivers the best performance involving high specific capacity (975 mAh g-1 at 0.2 A g-1), excellent rate capability (400.8 mAh g-1 at 10 A g-1), and stable cycling performance (86.8 % capacity retention after 600 cycles) due to its stable structure, smaller molar mass, and favorable electronic structure. Moreover, the Li-storage mechanism and solid electrolyte interphase (SEI) evolution of the Co-EG/rGO electrode are studied in detail through multiple ex-situ/in-situ characterizations. This work provides a new type of metal alkoxide anode material for high-rate and long-life LIBs toward practical energy applications.

Electrochemical CO2 Reduction Reaction: Comprehensive Strategic Approaches to Catalyst Design for Selective Liquid Products Formation

The escalating concern regarding the release of CO2 into the atmosphere poses a significant threat to the contemporary efforts in mitigating climate change. Amidst a multitude of strategies for curtailing CO2 emissions, the electrochemical CO2 reduction presents a promising avenue for transforming CO2 molecules into a diverse array of valuable gaseous and liquid products, such as CO, CH3OH, CH4, HCO2H, C2H4, C2H5OH, CH3CO2H, 1-C3H7OH and others. The mechanistic investigations of gaseous products (e. g. CO, CH4, C2H4, C2H6 and others) broadly covered in the literature. There is a noticeable gap in the literature when it comes to a comprehensive summary exclusively dedicated to coherent roadmap for the designing principles for a selective catalyst all possible liquid products (such as CH3OH, C2H5OH, 1-C3H7OH, 2-C3H7OH, 1-C4H9OH, as well as other C3-C4 products like methylglyoxal and 2,3-furandiol, in addition to HCO2H, AcOH, oxalic acid and others), selectively converted by CO2 reduction. This entails a meticulous analysis to justify these approaches and a thorough exploration of the correlation between materials and their electrocatalytic properties. Furthermore, these insightful discussions illuminate the future prospects for practical applications, a facet not exhaustively examined in prior reviews.

Structure and dynamics of aqueous VOSO4 solutions in conventional flow through cell design: a molecular dynamics simulation study

A theoretical model has been proposed to study the structure and dynamics of aqueous vanadyl sulfate (VOSO4) solution used in the conventional flow (CF) through cell design operating under varying thermodynamic conditions. Classical molecular dynamics simulations have been carried out for aqueous solutions of vanadyl sulfate (VOSO4) and sulfuric acid (H2SO4) at two different concentrations and temperatures considering the temperature dependent degree of dissociation of sulfuric acid. The MD trajectories are used to study the equilibrium structural, dynamical properties such as viscosity, diffusivity and surface tension of the aqueous solution of vanadyl sulfate (VOSO4). According to the new model, the cation-cation and cation-anion interaction should be low in order to have a good current density in the conventional flow through cell design and further explains the importance of considering mass transport when designing high energy density redox flow batteries. The model is further validated by calculating the viscosity of each system, individual diffusion coefficient of each ion and by comparing them with the experimental data wherever they are available.

CuS-NiTe2 embedded phosphorus-doped graphene oxide catalyst for evaluating hydrogen evolution reaction

The hydrogen evolution reaction (HER), a crucial half-reaction in the water-splitting process, is hindered by slow kinetics, necessitating efficient electrocatalysts to lower overpotential and enhance energy conversion efficiency. Transition-metal electrode materials, renowned for their robustness and effectiveness, have risen to prominence as primary contenders in the field of energy conversion and storage research. In this investigation, we delve into the capabilities of transition metals when employed as catalysts for the HER. Furthermore, we turn our attention to carbon nanomaterials like graphene, which have exhibited tremendous potential as top-performing electrocatalysts. Nevertheless, advancements are indispensable to expand their utility and versatility. One such enhancement involves the integration of phosphorus-doped graphene. Our research focuses on the synthesis of CuS-NiTe2/PrGO, a nanocomposite with a crystalline structure, through a straightforward method. This nanocomposite exhibits enhanced catalytic activity for the HER, boasting a Tafel slope of 57 mV dec-1 in an acidic environment. Consequently, our findings present a straightforward and efficient approach to developing high-performance electrocatalysts for HER.

Screening Ammonium-Based Cationic Additives to Regulate Interfacial Chemistry for Aqueous Ultra-Stable Zn Metal Anode

The interfacial dynamics and chemistry at the electrolyte/metal interface, particularly the formation of an adsorption interphase, is paramount in dictating the reversibility of Zn metal deposition and dissolution processes in battery systems. Herein, a series of different cationic ammonium-based electrolyte additives are screened that effectively modulate the interfacial chemistry of zinc anodes in aqueous electrolytes, significantly improving the reversibility of Zn metal plating/stripping processes. As initially comprehensive investigation by combining theoretical calculation and molecular dynamic simulation, the tetramethylammonium cation, with its specific molecular structure and charge distribution, is identified as pivotal in mediating the Zn(H2O)6 2+ solvation shell structure at the electrode/electrolyte interface and shows the strong resistance against electrolyte corrosion as revealed by X-ray and optical measurements. As a result, the Zn||Zn symmetric cell with optimal electrolyte lasts for over 4400 h of stable plating/stripping behaviors, and the Zn||Cu asymmetric cell stabilizes for 2100 cycles with an average Coulombic efficiency of 99.8%, which is much better than the-state-of-art progress. Consequently, full-cells coupled with various cathodes showcase improved electrochemical performance, displaying high capacity-retention and low self-discharge behaviors. These findings offer essential insights of cationic additives in ameliorating zinc anode performance.

Bilayered Vanadium Oxides Pillared by Strontium Ions and Water Molecules as Stable Cathodes for Rechargeable Zn-Metal Batteries

Vanadium-based compounds have attracted significant attention as cathodes for aqueous zinc metal batteries (AZMBs) because of their remarkable advantages in specific capacities. However, their low diffusion coefficient for zinc ions and structural collapse problems lead to poor rate capability and cycle stability. In this work, bilayered Sr0.25V2O5·0.8H2O (SVOH) nanowires are first reported as a highly stable cathode material for rechargeable AZMBs. The synergistic pillaring effect of strontium ions and water molecules improves the structural stability and ion transport dynamics of vanadium-based compounds. Consequently, the SVOH cathode exhibits a high capacity of 325.6 mAh g-1 at 50 mA g-1, with a capacity retention rate of 72.6% relative to the maximum specific capacity at 3.0 A g-1 after 3000 cycles. Significantly, a unique single-nanowire device is utilized to demonstrate the excellent conductivity of the SVOH cathode directly. Additionally, the energy storage mechanism of zinc insertion and extraction is investigated using a variety of advanced in situ and ex situ analysis techniques. This method of ion intercalation to improve electrochemical performance will further promote the development of AZMBs in large-scale applications.

Liquid Bi-Sb-Sn Electrodes with Synergistic Stabilization Mechanism for Long-Lifespan Sodium-Based Liquid Metal Batteries

Sodium-based liquid metal batteries are well suited for stationary energy storage due to their long life, intrinsic safety, and ease of scale-up. However, the irreversible alloying reaction between the positive current collector (PCC) and the cathodes at high temperatures leads to severe capacity degradation of the battery, severely limiting its scale-up application. In this work, a Bi-Sb-Sn alloy cathode based on a synergistic stabilization mechanism was designed for the first time. Due to the density difference of Bi, Sb, and Sn and the compatibility difference of Bi and Sn with the PCC, a part of Bi and Sn is spontaneously distributed in the region close to the PCC. The protection of Sb is realized by blocking the contact of Sb with the PCC as well as removing the PCC material dissolved in the cathode to prevent the loss of active material. Based on such protection, the Na||Bi36Sb24Sn40 cell maintained 99% Coulombic efficiency for 450 cycles at a rate of 0.75 C, with a capacity retention of 99.56% and a capacity decay rate of 0.001% per cycle. In addition, the interaction of Bi, Sb, and Sn during discharge also promotes capacity release and energy efficiency. At 0.3 C, the Na||Bi36Sb24Sn40 cell achieved 89% capacity utilization and 82% energy efficiency. These results provide an idea for the design of other batteries based on liquid metal electrodes.

Fleeting-Active-Site-Thrust Oxygen Evolution Reaction by Iron Cations from the Electrolyte

Oxygen evolution reaction (OER) is key to sustainable energy and environmental engineering, thus necessitating rational design of high-performing electrocatalysts that requires understanding the structure-performance relationship with a possible dynamic nature under working conditions. Herein, we uncover a novel type of OER mechanisms thrust by the fleeting active sites (FASs) dynamically formed on Ni-based layered double hydroxides (Ni-LDHs) by Fe cations from the electrolyte under OER potentials. We employ grand-canonical ensemble methods and microkinetic modeling to elucidate the potential-dependent structures of FASs on Ni-LDHs and demonstrate that the fleeting-active-site-thrust (FAST) mechanism delivers superior OER activity via the FAST intramolecular oxygen coupling pathway, which also suppresses the lattice oxygen mechanism, leading to improved operando stability of Ni-LDHs. We further reveal that introducing only trace-level loadings (10-100 ppm) of FASs on Ni-LDHs can significantly boost and govern the catalytic performance for OER. This underscores the crucial importance of considering the novel FAST mechanism in OER and also suggests the electrolyte as a key part of the structure-performance relationship as well as an effective design strategy via engineering the electrolyte.

Single-Atom Doped Fullerene (MN4-C54) as Bifunctional Catalysts for the Oxygen Reduction and Oxygen Evolution Reactions

Development of high-performance oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts is crucial to realizing the electrolytic water cycle. C60 is an ideal substrate material for single atom catalysts (SACs) due to its unique electron-withdrawing properties and spherical structure. In this work, we screened for a novel single-atom catalyst based on C60, which anchored transition metal atoms in the C60 molecule by coordination with N atoms. Through first-principles calculations, we evaluated the stability and activity of MN4-C54 (M = Fe, Co, Ni, Cu, Rh, Ru, Pd, Ag, Pt, Ir, Au). The results indicate that CuN4-C54, which is based only on earth-abundant elements, exhibited low overpotentials of 0.46 and 0.47 V for the OER and ORR, respectively, and was considered a promising bifunctional catalyst, showing better performance than the noble-metal ones. In addition, according to the linear relationship of intermediates, we established volcano plots to describe the activity trends of the OER and ORR on MN4-C54. Finally, d-band center and crystal orbital Hamiltonian populations methods were used to explain the catalytic origin. Suitable d-band centers lead to moderate adsorption strength, further leading to good catalytic performances.

Reliability studies of vanadium redox flow batteries: upper limit voltage effect

All-vanadium redox flow batteries (VRFBs) show promise as a long-duration energy storage (LDES) technology in grid applications. However, the continual performance fading over time poses a significant obstacle for VRFBs. This study systematically investigates the impact of increased upper limit voltage (1.6 V, 1.7 V, and 1.8 V) in the reliability and degradation of a scaled VRFB cell (49 cm2) over long-term testing (500+ cycles). The findings indicate that higher upper voltages significantly decrease capacity and voltage efficiencies. Although electrolyte remixing can restore the majority of the capacity, it only partially recovers voltage efficiency at 1.7 V and 1.8 V, suggesting substantial cell degradation. Analysis reveals that the overpotential increase induced degradation is mainly contributed by the anode during charging and the cathode during discharging. Increased upper voltage amplifies degradation, with the anode being more affected. As confirmed by electrochemical impedance spectroscopy (EIS) and polarization curves, elevated voltages lead to significant resistance increases, driven by charge transfer resistance (mostly from the anode). Moreover, the morphological, surficial, and electrochemical characterization results of cycled electrodes suggest that the degree and mode of degradation were contingent upon the cutoff voltage. For instance, the cathode experienced severe surface degradation at the maximal upper voltage of 1.8 V. This work highlights the importance of optimizing voltage limits to improve the lifetime of VRFBs and offers valuable insights into the development of predictive models through using accelerated stressor lifetime testing (ASLT) protocols for VRFBs.

The correlation of the liquidus curves and valence electron structures of a ternary lithium halide molten-salt electrolyte for liquid metal batteries

Liquid metal batteries have received considerable attention owing to their excellent properties. However, an electrolyte with low melting temperature is required to decrease operating temperature for the safety of liquid metal batteries and for saving energy. For revealing the mechanism of low liquefaction temperature, an empirical electron theory of solid molecules was used to study the thermal properties of pure lithium halides and their ternary-phase systems systematically. The theoretical bond lengths, melting points, liquefaction temperatures and mixed energies of pure lithium halides and their ternary phases match the experimental values well. The mechanism of liquefaction temperature for ternary lithium halides depends on their valence electron structures. The liquefaction temperature can be stabilized on a liquidus line or curve through the modulation of the constant number of covalent electrons (nc) and lattice electrons (nl). The liquefaction temperatures on various liquidus lines and curves are positively related to the linear density of valence electron pairs on the strong Li-X bond, bonding factor, and number of valence electrons in the s orbital but are negatively related to the number of valence electrons in the p orbital. With an increase in the linear density of the valence electron pair number and bonding factor, bond strength is enhanced, which increases the resistance of the strong Li-X bond against the break force induced by thermal phonon vibrations, and more thermal phonons with high vibrating energy are required for breaking the strongest Li-X bond at a higher temperature; therefore, the liquefaction temperature increases.

Unveiling the charge storage mechanisms of Co-based perovskite fluoride in a mild aqueous electrolyte

This study is an in-depth exploration of the charge storage mechanisms of KCoF3 in 1 M Na2SO4 mild aqueous electrolytes via an array of ex situ/in situ physicochemical/electrochemical methods, especially the electrochemical quartz crystal microbalance (EQCM) technique, showing a combination of conversion, insertion/extraction and adsorption mechanisms. Specifically, during the first charge phase, Co(OH)2 is formed/oxidized into amorphous CoOOH and Co3O4, and then CoOOH undergoes partial proton extraction to yield CoO2, which is simultaneously accompanied by the transformation of Co3O4 into CoOOH and (hydrated) CoO2. During the first discharge process, the partial insertion of H+ into (hydrated) CoO2 leads to the formation of CoOOH and Co3O4, with the conversion of Co3O4 into CoOOH and both Co3O4 and CoOOH undergoing further transformations into (hydrated) Co(OH)2via the insertion of H+. This work offers valuable references for the development of aqueous energy storage.

Interfacial chemistry in multivalent aqueous batteries: fundamentals, challenges, and advances

As one of the most promising electrochemical energy storage systems, aqueous batteries are attracting great interest due to their advantages of high safety, high sustainability, and low costs when compared with commercial lithium-ion batteries, showing great promise for grid-scale energy storage. This invited tutorial review aims to provide universal design principles to address the critical challenges at the electrode-electrolyte interfaces faced by various multivalent aqueous battery systems. Specifically, deposition regulation, ion flux homogenization, and solvation chemistry modulation are proposed as the key principles to tune the inter-component interactions in aqueous batteries, with corresponding interfacial design strategies and their underlying working mechanisms illustrated. In the end, we present a critical analysis on the remaining obstacles necessitated to overcome for the use of aqueous batteries under different practical conditions and provide future prospects towards further advancement of sustainable aqueous energy storage systems with high energy and long durability.

Transition metal oxide clusters: advanced electrocatalysts for a sustainable energy future

The comprehensive utilization of sustainable green energy is essential to face the global energy and environmental crisis. The oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and electrocatalytic urea synthesis (EUS) are the pivotal electrocatalytic processes, necessitating the development of low-cost electrocatalysts with high efficiency. Small-sized transition metal oxide (TMO) clusters have attracted a lot of attention because of their exceptional qualities, such as exhibiting a dense array of low-coordinated metal active sites (e.g. abundant metal cation defects and oxygen vacancy), amorphous structures with high surface energy, high atom utilization efficiency, and cost-effectiveness. Furthermore, the synergistic actions between metal clusters and TM-Nx single atom active sites remarkably boost up the electrocatalytic performances, corroborated by density functional theory (DFT). More efforts in this comprehensive feature article are expected to achieve insights into the fundamental understanding of electrocatalytic reaction mechanisms in our lab and serve as a guide for creating cutting-edge electrocatalysts of transition metal oxide clusters.

Demystifying In Situ Pyrolysis Chemistry for High-Performance Polyanionic Cathodes in Sodium-Ion Batteries

The carbon coating strategy has emerged as an indispensable approach to improve the conductivity of polyanionic cathodes. However, owing to the complex reaction process between precursors of carbon and cathode, establishing a unified screening principle for carbonaceous precursors remains a technical challenge. Herein, we reveal that carbonaceous precursor pyrolysis chemistry undeniably influences the formation process and performance of Na3V2(PO4)3 (NVP) cathodes from in situ insights. By investigating three types of carbonaceous precursors, it is found that O/H-containing functional groups can provide more bonding sites for cathode precursors and generate a reducing atmosphere by pyrolysis, which is beneficial to the formation of polyanionic materials and a uniform carbon coating layer. Conversely, excessive pyrolysis of functional groups leads to a significant amount of gas, which is detrimental to the compactness of the carbon layer. Furthermore, the substantial presence of residual heteroatoms diminishes graphitization. In this case, it is demonstrated that carbon dots (CDs) precursors with suitable functional groups can comprehensively enhance the Na+ migration rate, reversibility, and interface stability of the cathode material. As a result, the NVP/CDs cathode displays outstanding capacity retention, maintaining 92% after 10,000 cycles at a high rate of 50 C. Altogether, these findings provide a valuable benchmark for carbon source selection for polyanionic cathodes.

Constructing Microporous Ion Exchange Membranes via Simple Hypercrosslinking for pH-Neutral Aqueous Organic Redox Flow Batteries

Ion exchange membranes (IEMs) play a critical role in aqueous organic redox flow batteries (AORFBs). Traditional IEMs that feature microphase-separated microstructures are well-developed and easily available but suffer from the conductivity/selectivity tradeoff. The emerging charged microporous polymer membranes show the potential to overcome this tradeoff, yet their commercialization is still hindered by tedious syntheses and demanding conditions. We herein combine the advantages of these two types of membrane materials via simple in situ hypercrosslinking of conventional IEMs into microporous ones. Such a concept is exemplified by the very cheap commercial quaternized polyphenylene oxide membrane. The hypercrosslinking treatment turns poor-performance membranes into high-performance ones, as demonstrated by the above 10-fold selectivity enhancement and much-improved conductivities that more than doubled. This turn is also confirmed by the effective and stable pH-neutral AORFB with decreased membrane resistance and at least an order of magnitude lower capacity loss rate. This battery shows advantages over other reported AORFBs in terms of a low capacity loss rate (0.0017 % per cycle) at high current density. This work provides an economically feasible method for designing AORFB-oriented membranes with microporosity.

Enhancing Energy Storage Capacity of 3D Carbon Electrodes Using Soft Landing of Molecular Redox Mediators

The incorporation of redox-active species into the electric double layer is a powerful strategy for enhancing the energy density of supercapacitors. Polyoxometalates (POM) are a class of stable, redox-active species with multielectron activity, which is often used to tailor the properties of electrochemical interfaces. Traditional synthetic methods often result in interfaces containing a mixture of POM anions, unreactive counter ions, and neutral species. This leads to degradation in electrochemical performance due to aggregation and increased interfacial resistance. Another significant challenge is achieving the uniform and stable anchoring of POM anions on substrates to ensure the long-term stability of the electrochemical interface. These challenges are addressed by developing a mass spectrometry-based subambient deposition strategy for the selective deposition of POM anions onto engineered 3D porous carbon electrodes. Furthermore, positively charged functional groups are introduced on the electrode surface for efficient trapping of POM anions. This approach enables the deposition of purified POM anions uniformly through the pores of the 3D porous carbon electrode, resulting in unprecedented increase in the energy storage capacity of the electrodes. The study highlights the critical role of well-defined electrochemical interfaces in energy storage applications and offers a powerful method to achieve this through selective ion deposition.

Sulfur Modified Carbon-Based Single-Atom Catalysts for Electrocatalytic Reactions

Efficient and sustainable energy development is a powerful tool for addressing the energy and environmental crises. Single-atom catalysts (SACs) have received high attention for their extremely high atom utilization efficiency and excellent catalytic activity, and have broad application prospects in energy development and chemical production. M-N4 is an active center model with clear catalytic activity, but its catalytic properties such as catalytic activity, selectivity, and durability need to be further improved. Adjustment of the coordination environment of the central metal by incorporating heteroatoms (e.g., sulfur) is an effective and feasible modification method. This paper describes the precise synthetic methods for introducing sulfur atoms into M-N4 and controlling whether they are directly coordinated with the central metal to form a specific coordination configuration, the application of sulfur-doped carbon-based single-atom catalysts in electrocatalytic reactions such as ORR, CO2RR, HER, OER, and other electrocatalytic reaction are systematically reviewed. Meanwhile, the effect of the tuning of the electronic structure and ligand configuration parameters of the active center due to doped sulfur atoms with the improvement of catalytic performance is introduced by combining different characterization and testing methods. Finally, several opinions on development of sulfur-doped carbon-based SACs are put forward.

The Enormous Potential of Sodium/Potassium-Ion Batteries as the Mainstream Energy Storage Technology for Large-Scale Commercial Applications

Cost-effectiveness plays a decisive role in sustainable operating of rechargeable batteries. As such, the low cost-consumption of sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) provides a promising direction for "how do SIBs/PIBs replace Li-ion batteries (LIBs) counterparts" based on their resource abundance and advanced electrochemical performance. To rationalize the SIBs/PIBs technologies as alternatives to LIBs from the unit energy cost perspective, this review gives the specific criteria for their energy density at possible electrode-price grades and various battery-longevity levels. The cost ($ kWh-1 cycle-1) advantage of SIBs/PIBs is ascertained by the cheap raw-material compensation for the cycle performance deficiency and the energy density gap with LIBs. Furthermore, the cost comparison between SIBs and PIBs, especially on cost per kWh and per cycle, is also involved. This review explicitly manifests the practicability and cost-effectiveness toward SIBs are superior to PIBs whose commercialization has so far been hindered by low energy density. Even so, the huge potential on sustainability of PIBs, to outperform SIBs, as the mainstream energy storage technology is revealed as long as PIBs achieve long cycle life or enhanced energy density, the related outlook of which is proceeded as the next development directions for commercial applications.

Research Advances of Cathode Materials for Rechargeable Aluminum Batteries

Rechargeable aluminum ion batteries (AIBs) have recently gained widespread research concern as energy storage technologies because of their advantages of being safe, economical, environmentally friendly, sustainable, and displaying high performance. Nevertheless, the intense Coulombic interactions between the Al3+ ions with high charge density and the lattice of the electrode body lead to poor cathode kinetics and limited cycle life in AIBs. This paper reviews the recent advances in the cathode design of AIBs to gain a comprehensive understanding of the opportunities and challenges presented by current AIBs. In addition, the advantages, limitations, and possible solutions of each cathode material are discussed. Finally, the future development prospect of the cathode materials is presented.

Bifunctional Catalysts for CO2 Reduction and O2 Evolution: A Pivotal for Aqueous Rechargeable Zn-CO2 Batteries

The quest for the advancement of green energy storage technologies and reduction of carbon footprint is determinedly rising toward carbon neutrality. Aqueous rechargeable Zn-CO2 batteries (ARZCBs) hold the great potential to encounter both the targets simultaneously, i.e., green energy storage and CO2 conversion to value-added chemicals/fuels. The major descriptor of ARZCBs efficiency is allied with the reactions occurring at cathode during discharging (CO2 reduction) and charging (O2 evolution) which own different fundamental mechanisms and hence mandate the employment of two different catalysts. This presents an overall complex and expensive battery system which requires a concrete solution, while the development and application of a bifunctional cathode catalyst toward both reactions could reduce the complexity and cost and thus can be a pivotal for ARZCBs. However, despite the increasing research interest and ongoing research, a systematic evaluation of bifunctional catalysts is rarely reported. In this review, the need of bifunctional cathode catalysts for ARZCBs and associated challenges with strategies have been critically assessed. A detailed progress examination and understanding toward designing of bifunctional catalyst for ARZCBs have been provided. This review will enlighten the future research approaching boosted performance of ARZCBs through the development of efficient bifunctional cathode catalysts.

Carbon Nanotube Network Induces Porous Deposited MnO2 for High-Areal Capacity Zn/Mn Batteries

Mn2+/MnO2 aqueous battery is a promising candidate for large-scale energy storage owing to its feature of low-cost and abundant crustal reserves. However, the inherent MnO2 shedding issue results in a limited areal capacity and poor cycling life, which prohibits its further commercialization. In this manuscript, it is revealed that the cause of shedding is the cracking of MnO2 layer due to stress. To circumvent this challenge, carbon nanotubes framework is introduced on pristine carbon felt, which provides more deposition sites and induces the formation of a porous deposition layer. Compared to the dense deposition layer on pristine carbon felt, the porous structure can effectively avoid cracking and subsequent shedding issue. Moreover, the porous deposited layer is conducive to proton diffusion and rich in defects, which facilitates the subsequent dissolution reaction. As results, the assembled Zn/Mn battery demonstrates more than 200 cycles with the areal capacity of 15 mAh cm-2 at 40 mA cm-2. Even with a high areal capacity of 40 mAh cm-2, it can still run for more than 60 cycles. This breakthrough paves a way toward practical manganese-based batteries, bringing us closer to achieve cost-effective batteries.

Natural bio-waste-derived 3D N/O self-doped heteroatom honeycomb-like porous carbon with tuned huge surface area for high-performance supercapacitor

Supercapacitor electrodes (SCs) of carbon-based materials with flexible structures and morphologies have demonstrated excellent electrical conductivity and chemical stability. Herein, a clean and cost-effective method for producing a 3D self-doped honeycomb-like carbonaceous material with KOH activation from bio-waste oyster shells (BWOSs) is described. A remarkable performance was achieved by the excellent hierarchical structured carbon (HSC-750), which has a large surface area and a reasonably high packing density. The enhanced BWOSs-derived HSC-750 shows an ultrahigh specific capacitance of 525 F/g at 0.5 A g-1 in 3 M KOH electrolyte, as well as high specific surface area (2377 m2 g-1), pore volume (1.35 cm3 g-1), nitrogen (4.70%), and oxygen (10.58%) doping contents. The SCs also exhibit exceptional cyclic stability, maintaining 98.5% of their capacitance after 10,000 charge/discharge cycles. The two-electrode approach provides a super high energy density of 28 Wh kg-1 at a power density of 250 W kg-1 in an alkaline solution, with remarkable cyclability after 10,000 cycles. The study demonstrates the innovative HSC synthesis from BWOSs precursor and cost-effective fabrication of 3D N/O self-doped heteroatom HSC for flexible energy storage.

Strategy to Simultaneously Manipulate Direct Zn Nucleation and Hydrogen Evolution via Surface Modifier Hydrolysis for High-Performance Zn-Ion Batteries

The demand for safer batteries is growing rapidly due to fire incidents in electronic devices that use Li-ion batteries. Zn-ion batteries are among the most promising candidates to replace Li-ion batteries because they use a water-based electrolyte and are not explosive. However, Zn-ion batteries suffer from persistent corrosion and dendritic crystal formation during the charge-discharge process, which decrease their reversibility and hinder their commercial usage. Extensive research has been conducted to address these issues, but there are significant limitations due to high process and time costs. In this study, the modulation of the Zn-electrolyte interface to overcome these challenges is attempted using acetamide-derived thioacetamide (TAA), a surface modifier used in electroplating. TAA undergoes hydrolysis in an aqueous solution and produces weakly acidic byproducts and sulfide ions. These species are adsorbed onto the Zn metal surface, which induces uniform Zn2+ deposition, facilitates the formation of a stable interfacial layer, and inhibits side reactions due to the reduced water activity. Consequently, the symmetric cell with TAA achieves a low polarization of 50 mV and stable cycling for 700 h at 1 mA cm-2. Additionally, a Zn|V6O13 full cell exhibits electrochemical reversibility, maintaining a capacity retention of 64% over 300 cycles. Therefore, this study offers useful insights into the development of a simple manufacturing process to ensure the competitiveness of Zn-ion batteries for practical applications using functional electrolyte additives.

Path ahead: Tackling the Challenge of Computationally Estimating Lithium Diffusion in Cathode Materials

In the roadmap toward designing new and improved materials for Lithium ion batteries, the ability to estimate the diffusion coefficient of Li atoms in electrodes, and eventually solid-state electrolytes, is key. Nevertheless, as of today, accurate prediction through computational tools remains challenging. Its experimental measurement does not appear to be much easier. In this work, we devise a computational protocol for the determination of the Li-migration energy barrier and diffusion coefficient, focusing on a common cathode material such as LiNiO2, which represents a prototype of the widely adopted NMC (LiNi1-x-y Mn x Co y O2) class of materials. Different methodologies are exploited, combining ab initio metadynamics, path sampling, and density functional theory. Furthermore, we propose a novel, fast, and simple 1D approximation for the estimation of the effective frequency. The outlined computational protocol aims to be generally applicable to Lithium diffusion in other materials and components for batteries, including anodes and solid electrolytes.

Two-dimensional architecture of N,S-codoped nanocarbon composites embedding few-layer MoS2 for efficient lithium storage

The exploration and advancement of highly efficient anode materials for lithium-ion batteries (LIBs) are critical to meet the growing demands of the energy storage market. In this study, we present an easily scalable synthesis method for the one-pot formation of few-layer MoS2 nanosheets on a N,S dual-doped carbon monolith with a two-dimensional (2D) architecture, termed MoS2/NSCS. Systematic electrochemical measurements demonstrate that MoS2/NSCS, when employed as the anode material in LIBs, exhibits a high capacity of 681 mA h g-1 at 0.2 A g-1 even after 110 cycles. The exceptional electrochemical performance of MoS2/NSCS can be attributed to its unique porous 2D architecture. The few-layer MoS2 sheets with a large interlayer distance reduce ion diffusion pathways and enhance ion mobility rates. Additionally, the N,S-doped porous carbon matrix not only preserves structural integrity but also facilitates electronic conductivity. These combined factors contribute to the reversible electrochemical activities observed in MoS2/NSCS, highlighting its potential as a promising anode material for high-performance LIBs.

Development of Modular Nitrenium Bipolar Electrolytes for Possible Applications in Symmetric Redox Flow Batteries

Amid the escalating integration of renewable energy sources, the demand for grid energy storage solutions, including non-aqueous organic redox flow batteries (oRFBs), has become ever more pronounced. oRFBs face a primary challenge of irreversible capacity loss attributed to the crossover of redox-active materials between half-cells. A possible solution for the crossover challenge involves utilization of bipolar electrolytes that act as both the catholyte and anolyte. Identifying such molecules poses several challenges as it requires a delicate balance between the stability of both oxidation states and energy density, which is influenced by the separation between the two redox events. We report the development of a diaminotriazolium redox-active core capable of producing two electronically distinct persistent radical species with typically extreme reduction potentials (E1/2red < -2 V, E1/2ox > +1 V, vs Fc0/+) and up to 3.55 V separation between the two redox events. Structure-property optimization studies allowed us to identify factors responsible for fine-tuning of potentials for both redox events, as well as separation between them. Mechanistic studies revealed two primary decomposition pathways for the neutral radical charged species and one for the radical biscation. Additionally, statistical modeling provided evidence for the molecular descriptors to allow identification of the structural features responsible for stability of radical species and to propose more stable analogues.

Optical and Chemical Measurements of Solvated Electrons Produced in Plasma Electrolysis with a Water Cathode

It is known that glow discharges with a water anode inject and form solvated electrons at the plasma-liquid interface, driving a wide variety of reduction reactions. However, in systems with a water cathode, the production and role of solvated electrons are less clear. Here, we present evidence for the direct detection of solvated electrons produced at the interface of an argon plasma and a water cathode via absorption spectroscopy. We further quantify their yield using the dissociative electron attachment of chloroacetate, measuring a yield of 1.04 ± 0.59 electrons per incident ion, corresponding to approximately 100% faradaic efficiency. Additionally, we estimate a yield of 2.09 ± 0.93 hydroxyl radicals per incident ion. Comparison of this yield with other findings in the literature supports that these hydroxyl radicals are likely formed directly in the liquid phase rather than by diffusion from the vapor phase.

Stabilizing Zn/electrolyte Interphasial Chemistry by a Sustained-Release Drug Inspired Indium-Chelated Resin Protective Layer for High-Areal-Capacity Zn//V2O5 Batteries

For zinc-metal batteries, the instable chemistry at Zn/electrolyte interphasial region results in severe hydrogen evolution reaction (HER) and dendrite growth, significantly impairing Zn anode reversibility. Moreover, an often-overlooked aspect is this instability can be further exacerbated by the interaction with dissolved cathode species in full batteries. Here, inspired by sustained-release drug technology, an indium-chelated resin protective layer (Chelex-In), incorporating a sustained-release mechanism for indium, is developed on Zn surface, stabilizing the anode/electrolyte interphase to ensure reversible Zn plating/stripping performance throughout the entire lifespan of Zn//V2O5 batteries. The sustained-release indium onto Zn electrode promotes a persistent anticatalytic effect against HER and fosters uniform heterogeneous Zn nucleation. Meanwhile, on the electrolyte side, the residual resin matrix with immobilized iminodiacetates anions can also repel detrimental anions (SO4 2- and polyoxovanadate ions dissolved from V2O5 cathode) outside the electric double layer. This dual synergetic regulation on both electrode and electrolyte sides culminates a more stable interphasial environment, effectively enhancing Zn anode reversibility in practical high-areal-capacity full battery systems. Consequently, the bio-inspired Chelex-In protective layer enables an ultralong lifespan of Zn anode over 2800 h, which is also successfully demonstrated in ultrahigh areal capacity Zn//V2O5 full batteries (4.79 mAh cm-2).

Plasticised chitosan: Dextran polymer blend electrolyte for energy harvesting application: Tuning the ion transport and EDLC charge storage capacity through TiO2 dispersion

This study investigates the performance of biopolymer electrolytes based on chitosan and dextran for energy storage applications. The optimization of ion transport and performance of electric double-layer capacitors EDCL using these electrolytes, incorporating different concentrations of glycerol as a plasticizer and TiO2 as nanoparticles, is explored. Impedance measurements indicate a notable reduction in charge transfer resistance with the addition of TiO2. DC conductivity estimates from AC spectra plateau regions reach up to 5.6 × 10-4 S/cm. The electric bulk resistance Rb obtained from the Nyquist plots exhibits a substantial decrease with increasing plasticizer concentration, further enhanced by the addition of the nanoparticles. Specifically, Rb decreases from ∼20 kΩ to 287 Ω when glycerol concentration increases from 10 % to 40 % and further drops to 30 Ω with the introduction of TiO2. Specific capacitance obtained from cyclic voltammetry shows a notable increase as the scan rate decreases, indicating improved efficiency and stability of ion transport. The TiO2-enriched EDCL achieves 12.3 F/g specific capacitance at 20 mV/s scan rate, with high ion conductivity and extended electrochemical stability. These results suggest the great potential of plasticizer and TiO2 with biopolymers in improving the performance of energy storage systems.