Electrolyte Additives Research Articles

Dual Strategies of Na+ Electrolyte Additives and Dendrites Protective Ti3C2TX‐MXene/Zn Anode with 2D MXene Nanosheet Encased Niobium Pyrophosphate (NbP2O7) Composite Binder‐Free Cathode for Stable Zinc‐Ion Storage

AbstractZinc‐ion capacitors (ZICs) are promising next‐generation energy storage systems (ESS) owing to high safety, material abundance, environmental friendliness, and low cost; however, the energy density of ZICs must be improved to compete with lithium‐ion batteries (LIBs). Here, the study implements three strategies to enhance the electrochemical performance and manage dendritic growth on Zn anodes, including crafting a highly efficient redox electroactive niobium pyrophosphate (NbP2O7)/Ti3C2TX‐MXene binder‐free cathode, incorporating a NaClO4 additive electrolyte, and applying a protective Ti3C2TX‐MXene layer on Zn anode. The cathode facilitates rapid Zn2+ ion diffusion and a stable host structure. An electrostatic protection layer formed in additive electrolyte and MXene layers regulates the uniform distribution of the electric fields and supports the equalization of nucleation sites. These results are supported by density functional theory (DFT) calculations. The ZICs display an excellent specific capacitance (113.3 F g−1 at 1.5 A g−1) in aqueous additive electrolytes. The flexible solid‐state ZICs exhibits a volumetric capacitance of 865.05 mF cm−3, and an energy density of 0.347 mWh cm−3 at 2.29 mW cm−3 along with capacitance retention of >100% over 38 000 charge‐discharge cycles.

AI-Driven Electrolyte Additive Selection to Boost Aqueous Zn-Ion Batteries Stability.

In tackling the stability challenge of aqueous Zn-ion batteries (AZIBs) for large-scale energy storage, the adoption of electrolyte additive emerges as a practical solution. Unlike current trial-and-error methods for selecting electrolyte additives, a data-driven strategy is proposed using theoretically computed surface free energy as a stability descriptor, benchmarked against experimental results. Numerous additives are calculated from existing literature, forming a database for machine learning (ML) training. Importantly, this ML model relies solely on experimental values, effectively addressing the challenge of large solvent molecule models that are difficult to handle with quantum chemistry computation. The interpretable linear regression algorithm identifies the number of heavy atoms in the additive molecule and the liquid surface tension as key factors. Artificial intelligence (AI) clustering categorizes additive molecules, identifying regions with the most significant impact on enhancing battery stability. Experimental verification successfully confirms the exceptional performance of 1,2,3-butanetriol and acetone in the optimal region. This integrated methodology, combining theoretical models, data-driven ML, and experimental validation, provides insights into the rational design of battery electrolyte additives.

The combined effects of electrolyte addition and mechanical shearing on cellulose nanocrystal alignment

AbstractThis research explored the impact of four different electrolytes on the orientation of cellulose nanocrystals (CNCs) in shear-cast films prepared from aqueous CNC gels. Changes in the aqueous CNC gels’ rheological properties with electrolyte addition were correlated to the orientation and optical properties of dried CNC films. Film alignment was qualitatively assessed using cross-polarized optical microscopy and quantified by order parameters computed by UV–Vis transmission spectroscopy. Electrolyte addition resulted in an increased alignment in dried CNC films. For pure CNCs, the film order parameters remained constant at approximately 0.3 for shear rates from 20 s−1 to 100 s−1. However, higher order parameters were achieved in the presence of electrolytes. Notably, an order parameter of 0.88 was achieved at a shear rate of only 20 s−1. In addition, films produced from dispersions containing electrolytes exhibited improved clarity and haze. The results of this work highlight that electrolyte addition can enable higher order parameters at lower shear rates and facilitate the development of aligned CNC films for applications such as polarizers, clear coatings, and piezoelectric materials. Graphical abstract

Trace Amounts of Multifunctional Electrolyte Additives Enhance Cyclic Stability of High-Rate Aqueous Zinc-Ion Batteries.

Aqueous zinc ion batteries (AZIBs) are renowned for their exceptional safety and eco-friendliness. However, they face cycling stability and reversibility challenges, particularly under high-rate conditions due to corrosion and harmful side reactions. This work introduces fumaric acid (FA) as a trace amount, suitable high-rate, multifunctional, low-cost, and environmentally friendly electrolyte additive to address these issues. FA additives serve as prioritized anchors to form water-poor Inner Helmholtz Plane on Zn anodes and adsorb chemically on Zn anode surfaces to establish a unique in situ solid-electrolyte interface. The combined mechanisms effectively inhibit dendrite growth and suppress interfacial side reactions, resulting in excellent stability of Zn anodes. Consequently, with just tiny quantities of FA, Zn anodes achieve a high Coulombic efficiency (CE) of 99.55 % and exhibit a remarkable lifespan over 2580 hours at 5mA cm-2, 1 mAh cm-2 in Zn//Zn cells. Even under high-rate conditions (10mA cm-2, 1 mAh cm-2), it can still run almost for 2020 hours. Additionally, the Zn//V2O5 full cell with FA retains a high specific capacity of 106.95 mAh g-1 after 2000 cycles at 5 A g-1. This work provides a novel additive for the design of electrolytes for high-rate AZIBs.

Organic Electrolyte Additives for Aqueous Zinc Ion Batteries:Progress and Outlook.

Aqueous zinc ion batteries (AZIBs) are considered one of the most prospective new-generation electrochemical energy storage devices with the advantages of high specific capacity, good safety, and high economic efficiency. Nevertheless, the enduring problems of low Coulombic efficiency (CE) and inadequate cycling stability of zinc anodes, originating from dendrites, hydrogen precipitation and passivation, are closely tied to their thermodynamic instability in aqueous electrolytes, which significantly shortens the cycle life of the battery. Electrolyte additives can solve the above difficulties and are important for the advancement of affordable and reliable AZIBs. Organic electrolyte additives have attracted widespread attention due to their unique properties, however, there is a lack of systematic discussion on the performance and mechanism of action of organic electrolyte additives. In this review, a comprehensive overview of the application of organic electrolyte additives in AZIBs is presented. The role of organic electrolyte additives in stabilizing zinc anodes is described and evaluated. Finally, further potential directions and prospects for improving and directing organic electrolyte additives for AZIBs are presented.

Synergistic Cationic Shielding and Anionic Chemistry of Potassium Hydrogen Phthalate for Ultrastable Zn─I2 Full Batteries.

Electrolyte additives are investigated to resolve dendrite growth, hydrogen evolution reaction, and corrosion of Zn metal. In particular, the electrostatic shielding cationic strategy is considered an effective method to regulate deposition morphology. However, it is very difficult for such a simple cationic modification to avoid competitive hydrogen evolution reactions, corrosion, and interfacial pH fluctuations. Herein, multifunctional additives of potassium hydrogen phthalate (KHP) based on the synergistic design of cationic shielding and anionic chemistry for ultrastable Zn||I2 full batteries are demonstrated. K cations, acting as electrostatic shielding cations, constructed the smooth deposition morphology. HP anions can enter the first solvation shell of Zn2+ for the reduced activities of H2O, while they remain in the primary solvation shell and are finally involved in the formation of SEI, thus accelerating the charge transfer kinetics. Furthermore, by in situ monitoring the near-surface pH of the Zn electrode, the KHP additives can effectively inhibit the accumulation of OH- and the formation of by-products. Consequently, the symmetric cells achieve a high stripping-plating reversibility of over 4500 and 2600 h at 1.0 and 5mA cm-2, respectively. The Zn||I2 full cells deliver an ultralong term stability of over 1400 cycles with a high-capacity retention of 78.5%.

Dynamically Regulating Polysulfide Degradation via Organic Sulfur Electrolyte Additives in Lithium‐Sulfur Batteries

AbstractLithium‐sulfur (Li‐S) batteries offer promising prospects due to their high energy density and cost‐effectiveness. However, the sluggish kinetics of lithium polysulfides (LiPSs) conversion, particularly the crucial stage from LiPSs to lithium sulfide (Li2S), hampers their development. Herein, a novel strategy for dynamically regulating LiPSs conversion by incorporating 4‐mercaptopyridine (4Mpy), as a LiPSs Redox Regulator (RR) in the electrolyte is introduced. This organic sulfur additive actively interacts with LiPSs during discharge, facilitating rapid conversion and promoting the formation of a three‐dimensional (3D) Li2S structure, thereby enhancing reaction kinetics. Both theoretical and experimental results reveal that the redox conversion mechanism with the 4Mpy additive differs from traditional electrolytes. Upon lithiation, 4Mpy forms lithium‐pyridinethiolate (Li‐pyS), which reversibly engages in the LiPSs conversion during the charging/discharging cycles, significantly improving the redox process. As a result, the Li‐S battery with 4Mpy additive demonstrates superior performances, achieving 10.05 mAh cm−2 under a high sulfur loading of 10.88 mg cm−2, surpassing industrial benchmarks. This study not only presents an approach to mitigating the shuttle effect in Li‐S batteries but also offers valuable insights into electrolyte design for other metal batteries.

Stable LCO Cathodes Charged at 4.6 V for High Energy Secondary Li‐ion Batteries by One‐Pot Dual Metal Fluorides Coating

AbstractLiCoO2 (LCO) has been the cathode material of choice for three decades for durable, lightweight Li‐ion storage systems. Being charged up to 4.2 V versus Li/Li+, LCO provides excellent cycling stability with a specific capacity of ≈140 mAh g−1. Raising the cut‐off voltage to 4.6 V improves capacity by up to 60% however, it leads to rapid degradation of the cathode structure. Here, a one‐pot dual coating of MgF2 and AlF3 with fluorinated electrolyte additives achieves 190 mAh g−1 at a 0.5 C rate after 400 cycles with a capacity retention of 93%. Various analytical tools are used to follow the structural and morphological changes during cycling. Synergistically, ion transport is improved, and detrimental interfacial side reactions with the electrolyte solutions are fully mitigated. Structural stability is thus improved by using this coating, with only a little loss of the active material. This work provides a brief guideline for designing dual metal‐ion‐based surface coatings in various electrolytes to develop high‐voltage cathode systems for Li and maybe also Na batteries.

Highly porous ZIF-67/KLAC composite for enhanced supercapacitor performance with redox additive electrolyte

To enhance the efficiency of supercapacitors, the selection of appropriate electrode materials as well as electrolytes is essential. Highly porous materials have gained attention as electrode material while Redox Additive Electrolytes (RAE) have gained popularity as effective alternatives to traditional aqueous electrolytes. The present study discusses the fabrication of a highly porous Co-MOF (ZIF-67) grown on Keekar leaves-derived activated carbon (KLAC) to develop a suitable composite using a simple and inexpensive approach. The grown ZIF-67 material shows a polyhedron kind of morphology over the surface of KLAC with an overall surface area of 1012 m2/g. The synthesized material was evaluated for a three-electrode configuration in a 1 M Na2SO4 aqueous electrolyte and 0.2 M K3[Fe(CN)6] in 1 M Na2SO4 (RAE). The ZIF-67/KLAC composite exhibits a high capacitance of 2880 F/g when electrochemically tested within RAE, at a specific current of 5 A/g as compared to 33.11 F/g when tested in 1 M Na2SO4 aqueous electrolyte, over a potential range of −0.1–0.5 V. Also, the cyclic stability in RAE is found to be superior (∼100 %) as compared to 1 M Na2SO4 (∼95.30 %) after continuous 5000 charge-discharge cycles. The lower resistance in RAE allows for faster ionic and electronic transmission, resulting in superior cyclic stability. Due to the excellent electrochemical outcomes, the suggested synergic of ZIF-67/KLAC/RAE may work as a highly effective supercapacitor assembly in the future.

Comparison of Construction Strategies of Solid Electrolyte Interface (SEI) in Li Battery and Mg Battery-A Review.

The solid electrolyte interface (SEI) plays a critical role in determining the performance, stability, and longevity of batteries. This review comprehensively compares the construction strategies of the SEI in Li and Mg batteries, focusing on the differences and similarities in their formation, composition, and functionality. The SEI in Li batteries is well-studied, with established strategies that leverage organic and inorganic components to enhance ion diffusion and mitigate side reactions. In contrast, the development of the SEI in Mg batteries is still in its initial stages, facing significant challenges such as severe passivation and slower ion kinetics due to the divalent nature of magnesium ions. This review highlights various approaches to engineering SEIs in both battery systems, including electrolyte optimization, additives, and surface modifications. Furthermore, it discusses the impact of these strategies on electrochemical performance, cycle life, and safety. The comparison provides insights into the underlying mechanisms, challenges, and future directions for SEI research.

Influence of electrolyte additives on a pebble-shaped Mn2V2O7 electrode for electrochemical performance

In this study, pebble-shaped Mn2V2O7 nanoparticles have been synthesised by a simple hydrothermal technique. PXRD, FTIR, and FESEM-EDS studies have been used to investigate the structural and morphological nature of the material. The electrochemical performance has been conducted using two and three electrode configurations in redox additive electrolytes (RAE). It exhibits the highest specific capacitance of 3788.21 F/g at 6 A/g current density. After 10,000 cycles, the fabricated device shows a capacity retention of about 77.56 %.

Organic Small Molecules of Hydroxy-Rich Vitamins as Electrolyte Additives for Inducing Dendrite-Free and High-Performance Aqueous Zn-Ion Batteries

Organic Small Molecules of Hydroxy-Rich Vitamins as Electrolyte Additives for Inducing Dendrite-Free and High-Performance Aqueous Zn-Ion Batteries

The influence of P-toluenesulfonyl isocyanate on the solvation structure and solid electrolyte interphase formation on graphite anode under high temperatures

The formation and stability of the solid electrolyte interphase (SEI) play a crucial role in determining the performance and lifespan of lithium-ion batteries (LIBs) at evaluated temperatures. Electrolyte additives have emerged as promising candidates for modulating the formation kinetics and stability of the SEI layer. In this study, molecular dynamics (MD) and ab initio molecular dynamics (AIMD) simulations were employed to investigate the influences of P-toluenesulfonyl isocyanate (PTSI) as an electrolyte additive in the LiPF6/EC/DMC electrolyte on the SEI formation process on the graphite anode under high temperatures. MD simulations revealed that PTSI induces modifications in the solvation structure, resulting in two ethylene carbonate (EC) and two dimethyl carbonate (DMC) molecules in the first solvation shell of Li+. Furthermore, the PTSI additive suppressed the decomposition of solvent molecules and PF6 anions in the LiPF6/EC/DMC/PTSI electrolyte under high temperatures according to the AIMD simulations, contributing to a more stable SEI layer. Moreover, this suppression can be attributed to the reduced reactivity of solvent molecules and salt anions, as evidenced by the enhanced bond strength and decreased bond length. These microscopic insights provide a multi-faceted understanding of the functionality of PTSI additives, facilitating the rational design of novel additives.

Saturation absorbed sodium benzenesulfonate as crystallization modulating additive for dendrite-free Zn anode

Aqueous Zn metal batteries face significant obstacles such as rampant Zn dendrite growth and side reactions besides their benefits. Adding trace amounts of organic additives in electrolyte is considered as an application strategy to achieve long cycling performance. In this study, sodium benzenesulfonate (SBS) composed of an electron-withdrawing sulfonate group and a benzene ring is introduced as a crystallization modulating additive into ZnSO4 solution. We find that the saturation absorption concentration of SBS plays a key role in realizing the uniform deposition of Zn metal anode. SBS is vertically adsorbed onto Zn surface, building a top-down internal electric field that promotes the three-dimensional diffusion of Zn2+. SBS shows a crystallization modulating behavior in terms of grain nucleation, grain morphology and crystal orientation. The well-tailored crystallization structure contributes to a uniform Zn metal deposition for long cycling, which improved from 300 to 4000 cycles with the addition of SBS. At the saturation concentration of SBS, the Zn||Zn symmetric cell shows a lifespan of over 2200 h at 1 mA cm−2. This work not only provides a new option for Zn metal batteries additives but also offers new insights into the function of electrolyte additives.

Fabrication and performance assessment of coin cell supercapacitors with multiwalled carbon nanotube-supported mixed metal oxide nanocomposites and redox additive electrolyte

In the realm of supercapacitor applications, the fabrication of coin cell supercapacitors with superior performances played a crucial role. In this work, an asymmetrical type coin supercapacitor was fabricated with multiwalled carbon nanotube supported mixed metal oxide (CuO/CoO@MWCNT - CCM) nanocomposites (NCs) and potassium ferrocyanide incorporated KOH based redox additive electrolyte (RAE). The synergistic effect and the enhanced conductivity by the mixed metal oxides and MWCNT, respectively, were acted as the performance enhancer for electrode performances. On the other hand, RAE with optimized concentration provided additional redox active sites for superior performances. The combined effect of CCM NCs and RAE, were responsible for the superior performances. CCM NCs were prepared by one-pot hydrothermal technique and characterized. Working electrodes with CCM NCs were fabricated by doctor blade method and evaluated in KOH and RAE. It exhibited 1838.55 Fg−1 of specific capacitance (Csp) in RAE. Assembled asymmetrical supercapacitors with CCM NCs modified working electrode and activated carbon based anode, delivered 123.91 Fg−1 of Csp at 2.75 Ag−1 in RAE. The assembled supercapacitors delivered the highest energy density of 27.53 Wh kg−1 and power density of 1875 W kg−1 in RAE with an impressive 82.89 % of cyclic retention after 5000 GCD cycles. Finally, an asymmetric coin cell supercapacitor (CR2302) was fabricated with CCM NCs and RAE. The fabricated coin cell delivered the charge and discharge capacities of 157.72 and 55.99 mAh g−1, respectively in KOH, whereas these values were significantly improved 172.46 and 126.2 mAh g−1 respectively, in RAE. It proved that the fabricated coin cell supercapacitors performed well in terms of maximum charge and discharge performances in RAE compared to conventional KOH.

Facile synthesis of MCo2O4(M= Ni, Cu, and Zn) materials for high-performing electrochemical capacitors with robust cyclic stability using redox additive electrolyte

Developing efficient electrochemical capacitors relies heavily on the quality of electrode materials and electrolytes used. This report presents the successful solvothermal synthesis of three cobaltites, NiCo2O4, CuCo2O4, and ZnCo2O4, and their electrochemical performance in a 2M KOH solution. Among the three cobaltites, NiCo2O4 showed the best electrochemical performance with a specific capacity of 178 C/g with FTO (fluorine-doped tin oxide) as the current collector. In addition, the performance of NiCo2O4 was tested in different aqueous electrolytes, including KOH, NaOH, NaCl, and Na2SO4, and the specific capacity was found to vary in the order of 2 M KOH > 2 M NaOH > 2 M NaCl > 2 M Na2SO4. The performance of NiCo2O4 was also assessed in various concentrations of KOH electrolyte (2 M KOH, 3 M KOH, and 4 M KOH), and the best performance was observed in 3 M KOH with a specific capacity of 928.3 C/g with Ni foam as the current collector. Finally, using redox additive electrolytes, the performance of synthesized NiCo2O4 was evaluated in both 3-electrode and 2-electrode systems. No studies have been conducted on the electrochemical performance of NiCo2O4 with KFCN redox additive in a 3 M KOH electrolyte. In the three-electrode system, NiCo2O4 showed a high specific capacity of 1005.5 C/g at 1 A/g, with 167 % capacity retention after 1000 charge-discharge cycles at a high current density of 30 A/g. The NiCo2O4//Activated Carbon asymmetric hybrid supercapacitors in two-electrode systems exhibited a maximum specific capacity of 115.6 C/g and a specific energy density of 85 Wh/kg at a specific current density of 1 A/g. They also showed a capacitive retention of 120% after 5000 charge-discharge cycles. The maximum power density was 13225 W/kg at a current density of 5 A/g while maintaining an energy density of 22 Wh/kg.

Ultrasound-enabled adaptive protocol for fast charging of lithium-ion batteries

Abstract This paper introduces an ultrasound-assisted multi-stage constant current (UA-MSCC) charging protocol to enhance the charging performance of lithium-ion batteries. In this approach, ultrasound is applied during the final portion of each multi-stage constant current (MSCC) charging phase. Experimental results demonstrate that ultrasound decreases the internal resistance of pouch cells by up to 7%, leading to significant increase in charging capacity during each MSCC stage. The overall charging time is reduced by 26% compared to the conventional constant current constant voltage (CCCV) protocol. The performance improvement delivered by this ultrasound-assisted charging approach is especially large when the battery is charged at low temperatures and to a partial capacity. Notably, the application of ultrasound improves the coulombic efficiency to levels comparable to that at the room temperature when charging in cold environments (0°C). This approach can be applied to commercial batteries to immediately improve their charging performance, and can be seamlessly integrated into battery management systems. Unlike approaches that necessitate electrode material modifications or electrolyte additives, which require a long development time, this UA-MSCC charging protocol offers a practical and easily applicable solution for improving the battery charging performance.

Determination of the mutual influence of additives for a sulfate copper electrolyte on adsorption by the ellipsometry method

Determination of the mutual influence of additives for a sulfate copper electrolyte on adsorption by the ellipsometry method

Pyrrolic‐Nitrogen Chemistry in 1‐(2‐hydroxyethyl)imidazole Electrolyte Additives toward a 50,000‐Cycle‐Life Aqueous Zinc‐Iodine Battery

Rechargeable aqueous zinc iodine (Zn‐I2) batteries offer benefits such as low cost and high safety. Nevertheless, their commercial application is hindered by hydrogen evolution reaction (HER) and polyiodide shuttle, which result in a short lifespan. In this study, 1‐(2‐hydroxyethyl)imidazole (HEI) organic molecules featuring pyrrole‐N groups are introduced as dually‐functional electrolyte additives to simultaneously stabilize Zn anode and confine polyiodide through ion‐dipole interactions. The pyrrole‐N groups in HEI can preserve the interfacial pH equilibrium at Zn anode by reversibly capturing H+ ions and dynamically neutralizing OH− ions, thereby suppressing the HER. Notably, the H2 evolution rate at the Zn anode is reduced to a mere 2.20 µmol h−1 cm−2. Furthermore, the pyrrole‐N moieties in HEI effectively curtail the polyiodide shuttle at I2 cathode, which show adsorption energies of −0.174 eV for I2, −0.521 eV for I3−, and −0.768 eV for I−, as indicated by density functional theory calculations. Electrochemical testing demonstrates that the Zn//Zn symmetric cell maintains stable cycling for up to 4,200 hours at 1 mA cm−2. Most strikingly, at a high I2 mass loading of 9.7 mg cm−2, the Zn‐I2 battery achieves an extraordinary cycle life of 50,000 cycles.

Pyrrolic-Nitrogen Chemistry in 1-(2-hydroxyethyl)imidazole Electrolyte Additives toward a 50,000-Cycle-Life Aqueous Zinc-Iodine Battery.

Rechargeable aqueous zinc iodine (Zn-I2) batteries offer benefits such as low cost and high safety. Nevertheless, their commercial application is hindered by hydrogen evolution reaction (HER) and polyiodide shuttle, which result in a short lifespan. In this study, 1-(2-hydroxyethyl)imidazole (HEI) organic molecules featuring pyrrole-N groups are introduced as dually-functional electrolyte additives to simultaneously stabilize Zn anode and confine polyiodide through ion-dipole interactions. The pyrrole-N groups in HEI can preserve the interfacial pH equilibrium at Zn anode by reversibly capturing H+ ions and dynamically neutralizing OH- ions, thereby suppressing the HER. Notably, the H2 evolution rate at the Zn anode is reduced to a mere 2.20 µmol h-1 cm-2. Furthermore, the pyrrole-N moieties in HEI effectively curtail the polyiodide shuttle at I2 cathode, which show adsorption energies of -0.174 eV for I2, -0.521 eV for I3-, and -0.768 eV for I-, as indicated by density functional theory calculations. Electrochemical testing demonstrates that the Zn//Zn symmetric cell maintains stable cycling for up to 4,200 hours at 1 mA cm-2. Most strikingly, at a high I2 mass loading of 9.7 mg cm-2, the Zn-I2 battery achieves an extraordinary cycle life of 50,000 cycles.