Electrode Electrolyte Research Articles

Novel Anchored Branched Polymer Coating Layers for Enhanced Redox Kinetics in Aqueous Zinc‐Ion Batteries

The fundamental issues associated with Zn anodes prevent the commercialization of aqueous Zn ion batteries. To address this, a simple dip‐coating method was used to coordinate a thin layer of branched polyethyleneimine (b‐PEI) polymer onto the electrode surface. This process increases hydrophilicity and reduces interfacial resistance between the electrode and aqueous electrolyte. Consequently, electrolyte leaching from the hydrophilic polymer coating layer is prevented, charge distribution is uniform, and stable electrochemical performance is maintained over extended periods. In symmetric cell testing, the b‐PEI@Zn anode exhibits a lifespan of over 1400 h (3 mA cm−2, 1 mAh cm−2). Furthermore, full‐cell tests, the b‐PEI@Zn anode demonstrates higher capacity (+26.05%) and improved stability (95.4%) compared to the bare Zn anode (0.5 A g−1). This study presents a practical surface modification strategy for Zn anodes and underscores the potential of innovative polymer‐based electrode coatings for aqueous battery applications.

Lattice Strain-Modulated Trifunctional CoMoO4 Polymorph-Based Electrodes for Asymmetric Supercapacitors and Self-Powered Water Splitting.

Developing efficient, multifunctional electrodes for energy storage and conversion devices is crucial. Herein, lattice strains are reported in the β-phase polymorph of CoMoO4 within CoMoO4@Co3O4 heterostructure via phosphorus doping (P-CoMoO4@Co3O4) and used as a high-performance trifunctional electrode for supercapacitors (SCs), hydrogen evolution reaction (HER), and oxygen evolution reaction (OER) in alkaline electrolytes. A tensile strain of +2.42% on the β-phase of CoMoO4 in P-CoMoO4@Co3O4 results in superior electrochemical performance compared to CoMoO4@Co3O4. The optimized P-CoMoO4@Co3O4 achieves a high energy density of 118Wh kg-1 in an asymmetric supercapacitor and low overpotentials of 189mV for the HER and 365mV for the OER at a current density of 500mA cm-2. This results in a low overall water splitting voltage of 1.71V at the same current density making it an effective bifunctional electrode in a 1m KOH freshwater electrolyte. Theoretical analysis shows that the excellent performance of P-CoMoO4@Co3O4 can be attributed to interfacial interactions between CoMoO4 and Co3O4, and the β-phase of CoMoO4, which lead to strong OH- adsorption and low energy barriers for reaction intermediates. Practical application is demonstrated by using P-CoMoO4@Co3O4-based ASCs to self-generate hydrogen (H2) in a P-CoMoO4@Co3O4||P-CoMoO4@Co3O4 alkaline seawater electrolyzer, showcasing its potential for future energy technologies.

Operando monitoring the redox activity of sodium vanadium titanium phosphate electrodes in organic and aqueous electrolytes by magnetometry

The bulk oxidation states of the transition metals in Na2VTi(PO4)3 are monitored continuously based on magnetic susceptibility variations. It is shown that the same charge compensation processes occur in organic and aqueous electrolytes.

Challenges in extracting and characterizing electrolytes from automotive lithium-ion cells.

The demand for lithium-ion cells in the automotive industry is rapidly growing due to the increasing electrification of the transportation sector. The electrolyte composition plays a critical role in determining the lifetime and performance of these large-format cells. Additionally, advancements in this field are leading to frequent changes in both electrode materials and electrolyte formulations. As a result, new analytical approaches are required to enable comprehensive characterization of the relevant components of the electrolytes used in lithium-ion cells. In this research a novel electrolyte extraction method is presented, enabling the quantitative electrolyte analysis in large format cylindrical lithium-ion cells under inert conditions. A liquid-liquid extraction of the cell materials is performed in a newly developed extraction chamber, in which the electrodes are rewound to ensure an efficient extraction. The design of the chamber allows the extraction of volatile and nonvolatile electrolyte components. The cells were filled with various electrolytes and analyzed using high-performance liquid chromatography and ion chromatography coupled with electrospray ionization mass spectrometry. Using the developed method, up to 83% of the conductive salt and up to 89% of the solvents can be recovered. The first application of this method involved analyzing a cylindrical lithium-ion cell after formation. This method provides a crucial tool for mapping electrolyte compounds formed during degradation due to cycling or thermal aging. This analytical approach will offer valuable insights, contributing to a deeper understanding of lithium-ion cell systems and could enhance battery life and performance in the future.

Stable functional electrode–electrolyte interface formed by multivalent cation additives in lithium-metal anode batteries

This work introduces the use of multivalent cations (e.g. Ca2+, Ba2+, La3+ and Ce3+) as electrolyte additives in lithium-metal anode batteries with a focus on solvation structure modification, SEI formation and lithium growth.

Simultaneously constructing solid cathode/anode-electrolyte interphase by anions decomposition in aqueous Zn battery

Aqueous Zn batteries exhibit enormous potential in large-scale energy storage. However, complex interfacial side reactions between electrode and electrolyte fast deteriorate the electrochemical performance. Directly constructing solid electrode–electrolyte interphase is an effective strategy to enhance the interface stability, while it is difficult to form solid electrode–electrolyte interphase in conventional electrolytes. Herein, propylene carbonate was introduced into water-in-salts electrolytes to regulate Zn2+ solvation structure, which reduces the HOMO and LUMO energy gap of Zn2+ solvation complexes. As a result, anion-derived cathode-electrolyte interphase (CEI) and anode-electrolyte interphase (SEI) are formed simultaneously. Assembled Zn||Zn symmetrical cell achieves high cycling stability over 9000 h at 8 mA cm−2 with 8 mAh cm−2. Moreover, Zn||AlxV2O5·nH2O battery displays excellent cycling performance at low current density (capacity retention rate of 92 %/94 % after 400/1300 cycles of 0.2/0.5 A g−1). This work provides a simple and effective strategy to simultaneously construct CEI layer and SEI layer, achieving long life aqueous Zn batteries.

Investigating the Impact of Copper and Zinc Doping in High‐Entropy Prussian Blue Analogues for Na‐Ion Batteries: From Material Analysis to Device Fabrication

High‐entropy Prussian blue analogues (HE‐PBAs) show great promise as active materials in Na‐ion batteries, particularly due to their multimetallic synergism that enhances electrochemical performance. This study explores two HE‐PBAs: Na2Mn0.2Fe0.2Co0.2Ni0.2Cu0.2Fe(CN)6 (HE‐PBA‐1) and Na2Mn0.2Fe0.2Co0.2Ni0.2Zn0.2Fe(CN)6 (HE‐PBA‐2). Both crystallize in monoclinic (P21/n) symmetry, but HE‐PBA‐1, with Cu, exhibits a lower bandgap, lower Na‐ion diffusion barrier, higher [Fe(CN)6] vacancy, and smaller particle size compared to HE‐PBA‐2 with Zn. These factors result in higher power capability for HE‐PBA‐1 due to its enhanced electronic conductivity and Na‐ion diffusivity. Additionally, its higher [Fe(CN)6] vacancy and smaller particle size offer more electrochemical active sites, improving energy characteristics. A Na‐ion full cell with HE‐PBA‐1 as the positive electrode and a mixed‐metallic sodium–copper–iron oxide (NaCuFe‐Oxide) as the negative electrode in a hydrogel electrolyte is assembled. It achieves a specific capacity of 94 mAh g−1 at 100 mA g−1, an energy density of 70 Wh kg−1 at 74 W kg−1, a power density of 375 W kg−1 at 57 Wh kg−1, and excellent durability with 89% capacity retention over 500 cycles at 200 mA g−1 within a 0–2 V window. A 5 V/3 mAh prototype device is tested with a solar charging module to evaluate its real‐life feasibility.

Comparative study of the removal of urea by electrocoagulation and electrocoagulation combined with chemical coagulation in aqueous effluents

AbstractUrea is a major issue in human wastewater because it may be easily broken down by the urease enzyme produced by bacteria, leading to ammonia production. Due to its ability to increase soil pH and eutrophicate streams, ammonia-containing effluent emissions pose environmental and health risks. This study aimed to evaluate the effectiveness of various treatment approaches in reducing urea concentrations by comparing the removal rates of conducting electrocoagulation (EC), EC followed by chemical coagulation (EC-CC), and CC followed by electrocoagulation (EC-CC). Numerous electrocoagulation parameters have been investigated, including current density, electrode gap distance, electrolyte type, concentration, and electrolysis duration. The electrode morphology was examined using a scanning electron microscope, while the produced sludge was analyzed using Fourier transform infrared spectroscopy. Three kinds of aluminum coagulants—potash alum, aluminum sulfate, and aluminum chloride—were used in the chemical coagulation, while the electrocoagulation was optimized at 30 A/m2. The results of this investigation suggest that the application of EC-CC, regardless of the type of coagulant used in both synthetic and real effluent, could marginally improve the efficacy of urea removal. Conversely, CC-EC exhibits an adverse effect on the efficiency of urea removal in both synthetic and real wastewater. The application of CC-EC demonstrated a significant improvement in the effectiveness of COD removal from actual wastewater, according to experimental results. The study emphasized the effectiveness and economic advantages of electrocoagulation over EC-CC and CC-EC techniques, used to remove urea from both real and synthetic wastewater.

Preferred Chemical Agent for Electrochemical Modification of Physical and Mechanical Parameters of Mudstone

To study the influence of electrochemically modified mediums on the physical and mechanical parameters of mudstone samples, focusing on electrolyte solutions and electrode materials, this paper combines theoretical analysis and experimental research. It analyzes the modification mechanism of mudstone through electrochemical techniques, clarifying that the main factors improving the strength of mudstone are electro-osmotic drainage consolidation and electrochemical reaction cementation. The mudstone was electrochemically modified using the controlled variable method. The mudstone sample’s hydraulic properties and shear strength were measured before and after modification. The study compared and analyzed the effectiveness of different modified materials. The results indicated that the liquid limit of the modified mudstone samples decreased by 7.874%, while the plastic limit increased by 9.499%. The type of ions introduced by the electrolyte solution influenced the cementation strength of the mudstone. AlCl3 solutions with a 10% mass fraction and CaCl2 solutions with a 25% mass fraction both effectively modify the reinforcement; however, the AlCl3 solution with a 10% mass fraction is the most effective for modifying mudstone samples. The electrochemical modification of mudstone samples with the three electrode materials (graphite, iron and aluminum) revealed that the samples modified with graphite electrodes had the highest shear strength, while those modified with aluminum electrodes had the lowest shear strength. The internal friction angle of graphite electrode-modified mudstone specimens was 26.7°, compared to the original value of 23.9°, and the cohesion was 34.4 kPa, compared to the original value of 12.3 kPa, nearly three times the original value. It is recommended to use graphite electrodes and a 10% mass fraction of AlCl3 for the electrochemical modification of this type of mudstone in engineering applications.

Mn Doping at High-Activity Octahedral Vacancies of γ-Fe2O3 for Oxygen Reduction Reaction Electrocatalysis in Metal-Air Batteries.

γ-Fe2O3 with the intrinsic cation vacancies is an ideal substrate for heteroatom doping into the highly active octahedral sites in spinel oxide catalysts. However, it is still a challenge to confirm the vacancy location of γ-Fe2O3 through experiments and obtain enhanced catalytic performance by preferential occupation of octahedral sites for heteroatom doping. Here, a Mn-doped γ-Fe2O3 incorporated with carbon nanotubes catalyst was developed to successfully achieve preferential doping into highly active octahedral sites by employing γ-Fe2O3 as the precursor. Further, the vacancy in γ-Fe2O3 was only located on octahedral sites rather than tetrahedral ones, which was first proved by direct experimental evidence through the clarification doping sites of Mn. Notably, the catalyst shows outstanding activity towards oxygen reduction reaction with the half-wave potential of 0.82 V and 0.64 V vs. reversible hydrogen electrode in alkaline and neutral electrolytes, respectively, as well as the maximum power density of 179 mWcm-2 and 403 mWcm-2 for Mg-air batteries and Al-air batteries, respectively. It could be attributed to the synergistic effect of the doping Mn on octahedral sites and the substrate γ-Fe2O3 along with the modification of the adsorption/desorption properties for oxygen-containing intermediates as well as the optimization of the reaction energy barriers.

Chiral Metal Coating to Enhance Water Electrolysis.

Producing hydrogen through water splitting often faces challenges of overpotential, stability, and expensive catalysts, which limit its efficiency and hinder the advancement of hydrogen production technologies. Nickel foam and nickel meshes have emerged as promising materials for electrolyzer electrodes due to their high surface area and the ability to produce electrolyzers with a very small gap between the anode and cathode. This study presents a simple method for coating Ni-based electrodes with a chiral Ni-Au film, using electroplating, thus enhancing its efficiency dramatically. We introduce chirality to the electroplating layer by incorporating an enantiopure chiral reagent into the electroplating solution. The chiral layer enhances the oxygen evolution reaction due to the chiral-induced spin selectivity effect. By optimizing the chiral electroplating process, we demonstrate the reduction of the overpotential and an increase in the reaction efficiency by 95% at 1 M KOH at room temperature.

Solid-State Battery Developments: A Cross-Sectional Patent Analysis

Solid-state batteries (SSBs) hold the potential to revolutionize energy storage systems by offering enhanced safety, higher energy density, and longer life cycles compared with conventional lithium-ion batteries. However, the widespread adoption of SSBs faces significant challenges, including low charge mobility, high internal resistance, mechanical degradation, and the use of unsustainable materials. These technical and manufacturing hurdles have hindered the large-scale commercialization of SSBs, which are crucial for applications such as electric vehicles, portable electronics, and renewable energy storage. This study systematically reviews the global SSB patent landscape using a cross-sectional bibliometric and thematic analysis to identify innovations addressing key technical challenges. The study classifies innovations into key problem and solution areas by meticulously examining 244 patents across multiple dimensions, including year, geographic distribution, inventor engagement, award latency, and technological focus. The analysis reveals significant advancements in electrolyte materials, electrode designs, and manufacturability. This research contributes a comprehensive analysis of the technological landscape, offering valuable insights into ongoing advancements and providing a roadmap for future research and development. This work will benefit researchers, industry professionals, and policymakers by highlighting the most promising areas for innovation, thereby accelerating the commercialization of SSBs, and supporting the transition toward more sustainable and efficient energy storage solutions.

Well-Defined Co2 Dual-Atom Catalyst Breaks Scaling Relations of Oxygen Reduction Reaction.

The 4-electron oxygen reduction reaction (ORR) under alkaline conditions is central to the development of non-noble metal-based hydrogen fuel cell technologies. However, the kinetics of ORR are constrained by scaling relations, where the adsorption free energy of *OOH is intrinsically linked to that of *OH with a nearly constant difference larger than the optimal value. In this study, a well-defined binuclear Co2 complex was synthesized and adsorbed onto carbon black, serving as a model dual-atom catalyst. This catalyst achieved a record half-wave potential of 0.972 V versus the reversible hydrogen electrode in an alkaline electrolyte. Density functional theory simulations and in situ infrared spectroscopy revealed that the dual-atom site stabilizes the *OOH intermediate through bidentate coordination, thereby reducing the free energy gap between *OOH and *OH. By altering the adsorption configuration of *OOH on the dual-atom site, the scaling relations are effectively disrupted, leading to a significant enhancement in ORR activity.

Intramolecular Hydrogen Bonds Weaken Interaction Between Solvents and Small Organic Molecules Towards Superior Lithium-Organic Batteries.

The strong interaction between organic electrode materials (OEMs) and electrolyte components induces a high solubility tendency of OEMs, thus hindering the practical application of lithium-organic batteries. Herein, we propose an efficient strategy for intramolecular hydrogen bonds (HBs) to redistribute the charge of OEMs to weaken the interaction with electrolyte components, thereby suppressing their dissolution. For the designed 2,2',2''-(2,4,6-trihydroxybenzene-1,3,5-triyl) tris (1H-naphtho[2,3-d]imidazole-4,9-dione) (TPNQ) molecule, the intramolecular HBs (O-H⋅⋅⋅N and N-H⋅⋅⋅O) reduce the charge density of active sites and alter the charge distribution on the molecular skeleton. As a result, TPNQ shows significantly reduced solubility in both ether- and ester-based solvents. In situ measurements and theoretical calculations indicate that the O-H⋅⋅⋅N dominated HB interaction strengthening during the discharging process, which can continuously suppress dissolution. Therefore, the TPNQ cathode displays high cycling stability (no capacity fading over 100 cycles at 0.1 A g-1; 88.4 % capacity retention over 1000 cycles at 1 A g-1), fast Li+-storage kinetics (211 mAh g-1 at 2 A g-1), and surprising low-temperature performances (stability cycles 500 times at -60 °C). Our results offer evidence that the intramolecular HBs strategy is promising in developing robust organic electrode materials for rechargeable batteries.

Intramolecular Hydrogen Bonds Weaken Interaction Between Solvents and Small Organic Molecules Towards Superior Lithium‐Organic Batteries

The strong interaction between organic electrode materials (OEMs) and electrolyte components induces a high solubility tendency of OEMs, thus hindering the practical application of lithium‐organic batteries. Herein, we propose an efficient strategy for intramolecular hydrogen bonds (HBs) to redistribute the charge of OEMs to weaken the interaction with electrolyte components, thereby suppressing their dissolution. For the designed 2,2',2''‐(2,4,6‐trihydroxybenzene‐1,3,5‐triyl) tris (1H‐naphtho[2,3‐d]imidazole‐4,9‐dione) (TPNQ) molecule, the intramolecular HBs (O‐H…N and N‐H…O) reduce the charge density of active sites and alter the charge distribution on the molecular skeleton. As a result, TPNQ shows significantly reduced solubility in both ether‐ and ester‐based solvents. In‐situ measurements and theoretical calculations indicate that the O‐H…N dominated HB interaction strengthening during the discharging process, which can continuously suppress dissolution. Therefore, the TPNQ cathode displays high cycling stability (no capacity fading over 100 cycles at 0.1 A g‐1; 88.4% capacity retention over 1000 cycles at 1 A g‐1), fast Li+‐storage kinetics (211 mAh g‐1 at 2 A g‐1), and surprising low‐temperature performances (stability cycles 500 times at ‐60 °C). Our results offer evidence that the intramolecular HBs strategy is promising in developing robust organic electrode materials for rechargeable batteries.

Investigation of Electrolyte Decomposition Byproducts in Gas and Liquid Phases Due to Water Impurities in Large‐Scale Acetonitrile‐Based Supercapacitors

AbstractThis study investigates the impact of water impurities on electrolyte decomposition in large‐scale cylindrical supercapacitors, with a focus on acetonitrile‐based electrolytes. The research identified ethylene, ethane, and nitrogen as primary gaseous byproducts and acetamide, N‐ethyl acetamide, and trimethylsilyl acetamide as major liquid‐phase decomposition products. Advanced analytical techniques, including in‐situ gas chromatography and nuclear magnetic resonance, revealed that water impurities significantly accelerate electrolyte degradation. The findings demonstrate that water‐induced decomposition mechanisms involve intricate pathways, including Hofmann elimination and hydrolysis reactions. Additionally, the presence of water catalyzes the formation of new byproducts, impacting both the electrolyte and electrode stability. This comprehensive analysis provides critical insights into the degradation processes of supercapacitors, emphasizing the need for stringent control of water content to enhance device longevity and performance. The study's outcomes suggest potential strategies for optimizing electrolyte compositions and electrode materials to mitigate degradation and improve supercapacitor efficiency.

Current Collectors for Supercapacitors: Objectives, Modification Methods and Challenges

AbstractSupercapacitors (SCs) have emerged as promising candidates for efficient and sustainable energy storage devices due to their unique merits, including high power density and long lifespan. However, despite these advantages, SCs face significant challenges related to their relatively low energy density. Current collectors are critical components of SCs, which significantly impacts the efficiency and overall performance by connecting active materials and external devices. However, the reviews on SCs are predominantly focused on electrode active materials or electrolyte materials, with insufficient comprehensive summaries regarding current collectors. This review focuses on the research progress related to current collectors in SCs. Firstly, the article outlines the modification objectives mechanism and inherent nature of SC current collectors. Building on this foundation, the authors further classify the current collector materials towards metallic, carbon‐based, polymers and other ones and highlights their modification strategies. Finally, the future development trends and challenges of SCs current collectors are comprehensively discussed.

Unravelling multi-layered structure of native SEI on lithium metal electrode and various electrolytes using reactive molecular dynamics

Lithium metal batteries, directly utilizing lithium metal as an anode, are promising as new-generation energy storage devices, and the characteristics of the solid electrolyte interphase (SEI) layer are critical to battery operation. However, the roles of electrolyte compositions on the structure and thickness of the passivating SEI film at the atomistic level have been previously overlooked, resulting in poor understanding of SEI characteristics. In this study, the formation of the native SEI layer on lithium metal electrode and various electrolyte composition is scrutinised using ReaxFF molecular dynamics (MD) simulations. The study successfully identifies different layers of the SEI film using charge distribution as a tool. The decrease in lithium density and the increase in the charge states of oxidised lithium atoms contribute to the identification of an inner layer and a transition layer within the previously known interface layer, as well as the sparse layer. Additionally, different reaction schemes are observed through the analysis of ratio between consumed lithium atoms and electrolyte molecules. Furthermore, results show the lithium salt concentration effects in suppressing the growth of the SEI between the lithium anode and the liquid electrolyte, and inhibiting the formation of key SEI components. This work provides new insights into the nature of SEI surface chemistry and potentially facilitates the design of artificial SEI layers and optimal electrolyte solutions.

Mn Doping at High‐Activity Octahedral Vacancies of γ‐Fe2O3 for Oxygen Reduction Reaction Electrocatalysis in Metal‐Air Batteries

γ‐Fe2O3 with the intrinsic cation vacancies is an ideal substrate for heteroatom doping into the highly active octahedral sites in spinel oxide catalysts. However, it is still a challenge to confirm the vacancy location of γ‐Fe2O3 through experiments and obtain enhanced catalytic performance by preferential occupation of octahedral sites for heteroatom doping. Here, a Mn‐doped γ‐Fe2O3 incorporated with carbon nanotubes catalyst was developed to successfully achieve preferential doping into highly active octahedral sites by employing γ‐Fe2O3 as the precursor. Further, the vacancy in γ‐Fe2O3 was only located on octahedral sites rather than tetrahedral ones, which was first proved by direct experimental evidence through the clarification doping sites of Mn. Notably, the catalyst shows outstanding activity towards oxygen reduction reaction with the half‐wave potential of 0.82 V and 0.64 V vs. reversible hydrogen electrode in alkaline and neutral electrolytes, respectively, as well as the maximum power density of 179 mWcm−2 and 403 mWcm−2 for Mg‐air batteries and Al‐air batteries, respectively. It could be attributed to the synergistic effect of the doping Mn on octahedral sites and the substrate γ‐Fe2O3 along with the modification of the adsorption/desorption properties for ORR oxygen‐containing intermediates as well as the optimization of the reaction energy barriers.

An anticoagulant supercapacitor for implantable applications

With the rapid advancement of implantable electronic medical devices, implantable supercapacitors have emerged as popular energy storage devices. However, supercapacitors inevitably come into direct contact with blood when implanted, potentially causing adverse clinical reactions such as coagulation and thrombosis, impairing the performance of implanted energy storage devices, and posing a serious threat to human health. Therefore, this work aims to design an anticoagulant supercapacitor by heparin doped poly(3, 4-ethylenedioxythiophene) (PEDOT) for possible applications in implantable bioelectronics. Heparin (Hep), the as-known anticoagulant macromolecule acts as the counterion for PEDOT doping to enhance its conductivity, and the bioelectrode material PEDOT: Hep with anticoagulant activity is synthesized via chemical oxidation polymerization. Concurrently, the anticoagulant supercapacitor is constructed through in-situ polymerization, where PEDOT: Hep and bacterial cellulose as electrode material and electrolyte layer, respectively. Owing to the incorporation of heparin, the supercapacitor exhibits high hemocompatibility with hemolysis rate <5 %, good anticoagulant performance with coagulation time of 63.4 s, reasonable cycle stability with capacitance retention rate of 76.24 % after 20, 000 cycles, and supplies power for implanted heart rate sensors in female mice. This work provides a platform for implantable electronics to achieve anticoagulant activity in vivo.