Gel Electrolyte Research Articles

Diagnostic Protocols for Evaluating the Degradation Mechanisms in Gel-Polymer Lithium Batteries.

Gel polymer electrolytes (GPEs) present a promising alternative to standard liquid electrolytes (LE) for Lithium-ion Batteries (LIBs) and Lithium Metal Batteries bridging the advantages of both liquid and solid polymer electrolytes. However, their cycle life still lags behind that of standard LIBs, and their degradation mechanisms remain poorly understood. A significant challenge is the need for specific diagnostic protocols to systematically study the degradation mechanisms of GPE-based cells. Challenges include the separation of cell components and effective washing, as well as the study of the solid electrolyte interfaces, all complicated by the semi-solid nature of GPEs. This paper provides a brief review of existing literature and proposes a comprehensive set of diagnostic tools for dismantling and evaluating the degradation of GPE-based LIBs. Finally, these methods and recommendations are applied to LiNi0.5Mn1.5O4 (LNMO)-graphite cells, revealing electrolyte oxidation as a major source of cell degradation.

Dual activated carbon derived from Keekar leaves as an excellent symmetric supercapacitor material

Porous carbonaceous materials derived from biomass, which are both cost-effective and obtained from sustainable resources, have emerged as appealing electrode materials for energy storage devices. These materials have received great interest as active electrode materials due to their ample, low-cost, sustainable nature and excellent electrochemical stability. In the present work, porous activated carbon (AC) was synthesized from Keekar leaves by dual activation using H2SO4 and KOH. This Keekar leaves derived AC (KLAC) possesses a surface area of ~1677m2g−1 with a combination of micro and mesoporosity displaying a specific capacitance of 411F/g in 6 M KOH and 219.55F/g for 1 M H2SO4 electrolytic solution at a current density of 1 A/g. Further, the symmetric devices were fabricated using both aqueous (aq.) and polymer gel electrolytes for practical evaluation of the material. The aq. and gel device are capable of delivering a specific capacitance of 108.34 F/g and 88.45 F/g, respectively, at a current density of 0.5 A/g. The aq. device offers a maximum energy density of 33.85 Whkg−1 at a power density of 562.5 Wkg−1. The outstanding capacitance retention of 89.5 % is demonstrated by the aq. device at a higher scan rate of 20 A/g after continuous 10,000 charging-discharging cycles. Such high performance and stability make KLAC a potential candidate as an affordable and sustainable electrochemical energy storage application.

Use of Silk Fibroin Material Composites for Green, Flexible Supercapacitors.

Within the context of seeking eco-friendly and readily available materials for energy storage, there is a pressing demand for energy storage solutions that employ environmentally sustainable, high-performance, and adaptable constituents. Specifically, such materials are essential for use in wearable technology, smart sensors, and implantable medical devices, whereas, more broadly, their use plays a pivotal role in shaping their efficiency and ecological footprint. Here, we demonstrate an entirely biopolymer-based supercapacitor with a remarkable performance, achieving a capacitance greater than 0.2 F cm-2 at a charge-discharge current of 10 mA cm-2 with 94% capacitance retention after 20,000 cycles. The supercapacitor is composed of three distinct silk fibroin (SF) composite materials, namely, photo-cross-linkable SF (Sil-MA) hydrogel, SF-polydopamine (SF-PDA), and SF bioplastic, to create a gel electrolyte, electrode binder, and encapsulation, respectively. Together, these elements form a mechanically and electrochemically robust skeleton for biofriendly energy storage devices. Moreover, these biomaterial-based supercapacitor devices show stretchability, flexibility, and compressibility while maintaining their electrochemical performance. The biomaterials and fabrication techniques presented can serve as a foundation for investigating various aqueous electrochemical energy storage systems, especially for emerging applications in wearable electronics and environmentally friendly material systems.

Highly stretchable double‐network gel electrolytes integrated with textile electrodes for wearable thermo‐electrochemical cells

AbstractThermo‐electrochemical cells (TECs) provide a new potential for self‐powered devices by converting heat energy into electricity. However, challenges still remain in the fabrication of flexible and tough gel electrolytes and their compatibility with redox actives; otherwise, contact problems exist between electrolytes and electrodes during stretching or twisting. Here, a novel robust and neutral hydrogel with outstanding stretchability was developed via double‐network of crosslinked carboxymethyl chitosan and polyacrylamide, which accommodated both n‐type (Fe2+/Fe3+) and p‐type ([Fe(CN)6]3−/[Fe(CN)6]4−) redox couples and maintained stretchability (>300%) and recoverability (95% compression). Moreover, poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) textile electrodes with porous structure are integrated into gel electrolytes that avoid contact issues and effectively boost the Pmax of n‐ and p‐type thermocell by 76% and 26%, respectively. The optimized thermocell exhibits a quick current density response and is continually fully operational under deformations, which satisfies the working conditions of wearable devices. Multiple thermocells (four pairs) are effectively connected in alternating single n‐ and p‐type cells in series and outputted nearly 74.3 mV at ΔT = 10°C. The wearable device is manufactured into a soft‐pack thermocells to successfully harvest human body heat and illuminate an LED, demonstrating the potential of the actual application of the thermocell devices.

Optoelectronic performance of Jatropha oil-derived poly(ethyl carbamate) gel polymer electrolyte as quasi-solid-state solution for photoelectrochemical cells

Optoelectronic performance of Jatropha oil-derived poly(ethyl carbamate) gel polymer electrolyte as quasi-solid-state solution for photoelectrochemical cells

Nanocomposite Perfluorosulfonic Acid/Montmorillonite-Na+ Polymer Membrane as Gel Electrolyte in Hybrid Supercapacitors.

Solid-state supercapacitors with gel electrolytes have emerged as a promising field for various energy storage applications, including electronic devices, electric vehicles, and mobile phones. In this study, nanocomposite gel membranes were fabricated using the solution casting method with perfluorosulfonic acid (PFSA) ionomer dispersion, both with and without the incorporation of 10 wt.% montmorillonite (MMT). MMT, a natural clay known for its high surface area and layered structure, is expected to enhance the properties of supercapacitor systems. Manganese oxide, selected for its pseudocapacitive behavior in a neutral electrolyte, was synthesized via direct co-precipitation. The materials underwent structural and morphological characterization. For electrochemical evaluation, a two-electrode Swagelok cell was employed, featuring a carbon xerogel negative electrode, a manganese dioxide positive electrode, and a PFSA polymer membrane serving as both the electrolyte and separator. The membrane was immersed in a 1 M Na2SO4 solution before testing. A comprehensive electrochemical analysis of the hybrid cells was conducted and compared with a symmetric carbon/carbon supercapacitor. Cyclic voltammetric curves were recorded, and galvanostatic charge-discharge tests were conducted at various temperatures (20, 40, 60 °C). The hybrid cell with the PFSA/MMT 10 wt.% exhibited the highest specific capacitance and maintained its hybrid profile after prolonged cycling at elevated temperatures, highlighting the potential of the newly developed membrane.

A High Voltage Symmetric Supercapacitor Comprising Concentrated NaCl: PVA Electrolyte and Partially Reduced Graphene Oxide Electrodes

AbstractStrategies to improve energy density in supercapacitors are mainly based on utilizing electrodes providing larger effective surfaces and electrolytes allowing op eration in wider voltage windows. Here, a water‐based, binder‐free, environmentally friendly, high voltage, and quasi‐solid‐state symmetric supercapacitor is presented comprising partially reduced graphene oxide active electrodes and concentrated NaCl: polyvinyl alcohol gel electrolyte. It is shown that the ionic diffusion through the electrode‐electrolyte interface is augmented by the partial reduction of the graphene oxide electrodes up to an optimum level. The safe operation voltage window is 4 V; the high field endurance is attributed to the ion‐saturated hydrogel electrolyte used. At a scan rate of 25 mV/s, the provided capacitance and stored energy are 0.1 F.cm−2 and 5.6 e−5 W.h.cm−2, respectively. The optimized device retains ~90 % of its initial capacitance after 1000 charge‐discharge cycles; no meaningful sign of degradation is detected afterwards up to the 2000 cycles examined. These results place further emphasis on the potentials of the gel polymer electrolytes in the fabrication of environmentally friendly supercapacitors. Our findings are anticipated to accelerate improvements in the properties of the graphene‐based electrodes, particularly in conjunction with the proposed electrolyte.

In Situ Polymerization of a Self-Healing Polyacrylamide-Based Eutectogel as an Electrolyte for Zinc-Ion Batteries.

Gel electrolytes have attracted extensive attention in flexible batteries. However, the traditional hydrogel electrolyte is not enough to solve the fundamental problems of zinc anodes, such as dendrite growth, side reactions, and freezing failure at temperatures below zero, which seriously restricts the development of zinc-ion batteries. As a flexible energy storage device, the zinc-ion battery inevitably undergoes multiple stretches, bends, folds, or twists in daily use. Here, a self-healing and stretchable eutectogel, designated as deep eutectic solvent-acrylamide eutectic gel (DA-ETG), was developed as a solid-state electrolyte for zinc-ion batteries. This gel was prepared by immobilizing a high-concentration ZnCl2 deep eutectic solvent (DES) into a polyacrylamide matrix through in situ polymerization under ultraviolet light. The eutectogel electrolyte showed exceptional mechanical properties with a maximum fracture strength of 0.6 MPa and a high ionic conductivity of 6.4 × 10-4 S cm-1. The in situ polymerization of the DA-ETG electrolyte in the assembly of a full solid-state zinc-ion battery increased the electrode-electrolyte interface area contact, reduced the ion transport distance between the electrode and electrolyte, minimized the internal resistance, and enhanced the battery's long-term cycling stability. Using the DA-ETG electrolyte, a remarkably high capacity of 580 mAh g-1 at 0.1 A g-1 was achieved by the zinc-ion battery, and a considerable capacity of 234 mAh g-1 was maintained even at 5 A g-1, showing exceptional rate performance. After 2000 cycles at 2 A g-1, the cell with the eutectogel retained a capacity of 85% with a cycling efficiency close to 98%, which demonstrated excellent cycling stability. The self-healing function enabled the prepared soft battery to be reused multiple times, with full contact between the electrode and electrolyte interface, and without device failures.

“Seaweed Structure” design for solid gel electrolyte with hydroxide ion conductivity enabling flexible zinc air batteries

The construction of solid-state electrolytes for flexible zinc-air batteries is extremely challenging. A flexible and highly conductive solid electrolyte designed with a “seaweed structure” is reported in this work. Sodium alginate serves as the backbone to form a robust network structure, and the grafted quaternary ammonium groups provide channels for rapid ion transport, achieving excellent flexibility and hydroxide conductivity. The conductivity of the modified electrolyte membrane (QASA) is 5.23 × 10−2 S cm−1 at room temperature and reaches up to 8.51 × 10−2 S cm−1 at 75 °C. In the QASA based battery, bending at any angle is realized, and the power density is up to 57.28 mW cm−2. This work provides a new way to prepare high conductivity, green solid-state zinc-air batteries, and opens up a research line of thought for flexible energy storage materials.

A Gel Polymer Electrolyte with High Uniform Na+ Flux and its Constructed Hybrid Interface Synergistically to Facilitate High-Performance Sodium Batteries.

Sodium metal batteries (SMBs) can be developed on a large scale to achieve low-cost and high-capacity energy storage systems. Gel polymer electrolyte (GPE) can relieve volatilization of liquid electrolyte, adapt to volume changes in electrodes, and better satisfy the requirements of long-term SMBs. Herein, a dense polyurethane-based GPE modified with polyacrylonitrile is synthesized by rapidly swelling two-component polyurethane/polyacrylonitrile electrospun fiber film. Compared to traditional porous GPEs obtained by swelling porous matrixes, the fiber film provides uniform high Na+ flux inside GPE due to its partial solubility property and ability to dissociate salts. Therefore, it can reduce the polarization effect and induce uniform metal deposition under high current in conjunction with its constructed hybrid N/F-containing solid electrolyte interface (SEI) that possesses low ionic diffusion barrier. The study demonstrates that GPE has an ionic conductivity of 1.816 mS cm-1 at 20 °C and an ion transference number of 0.53. The full battery (NVP/GPE/Na) assembled with this GPE and Na3V2(PO4)3 (NVP) cathode shows 90.8% capacity retention rate after 1000 cycles at 10 C. Considering the convenient preparation and outstanding electrochemical performances of the obtained GPE, it can also be matched with other electrodes in the future to expand the application of sodium-based batteries.

Integrated Hydrogel-Zn Structure with Modified Interface Realizing Fast Ion Transfer for Long Cycling Zn-ion Battery

Fabrication of gel electrolytes are effective strategy to solve the side reactions and dendrite growth of Zn anodes in aqueous rechargeable zinc batteries (ARZBs). However, complicated synthesis and ex-situ assembled processes lead to poor electrode–electrolyte interfacial contact, which hinders ion transfer. Herein, compatible and stable electrode–electrolyte structure is constructed by in-situ polymerization process. The tightly coupled electrode–electrolyte interface reduces the mass transfer impedance, balances electric field distribution, and thus inhibits dendrites. What’s more, the −SO3H groups in gel electrolyte play a significant role which performs as cation transport channels to regulate the deposition behavior of Zn along (002) crystal plane. The intercanected and porous structure of this electrolyte promote the desolvation process of [Zn(H2O)6]2+ and inhibit the side reaction. As a result, the symmetric cell exhibits ultra-long lifespan over 4,530 h (＞188 days), Zn||Cu cell delivers an average coulombic efficiency (CE) of 99.85 % with 1,000 cycles. Zn||MVO cell operates stably for over 2,700 cycles with CE of 99.91 %. This integrated hydrogel-Zn structure provides broad application prospect in wearable devices.

Double-network gel electrolyte with high electrolyte retention for flexible high-voltage Zn-air batteries

The zinc-air battery (ZAB) exhibits promising potential for application in wearable devices due to its high energy density, low cost, and safety features. However, the semi-open structure of ZAB accelerates the evaporation of battery electrolytes and poses a potential risk of leakage. Herein, a novel polyacrylamide-co-sodium p-benzenesulfonate and carboxymethyl cellulose (PAS-CMC) double-network gel electrolyte was synthesized and utilized in a flexible ZAB. The prepared PAS-CMC exhibits exceptional electrical conductivity (315.53 mS cm−1), mechanical properties, as well as electrolyte retention capacity. The ZAB assembled by alkaline PAS-CMC exhibits remarkable stability during circulation for over 120 h. Compared with the traditional alkaline PAS-CMC electrolyte, the open-circuit voltage (2.03 V), operating voltage (1.90 V) and power density (164.3 mW cm−2) of the ZAB assembled by the acid-alkaline PAS-CMC prepared by the “sandwich” strategy have been significantly improved, showing excellent flexibility under various bending conditions without any degradation in performance. Furthermore, the interaction mechanisms between PAS-CMC/H2O and PAS-CMC/Zn were further elucidated by DFT calculation, thereby establishing a theoretical foundation for high-voltage flexible ZAB.

Complex Hydride-Based Gel Polymer Electrolytes for Rechargeable Ca-Metal Batteries.

Rechargeable Ca batteries offer the advantages of high energy density, low cost, and earth-abundant constituents, presenting a viable alternative to lithium-ion batteries. However, using polymer electrolytes in practical Ca batteries is not often reported, despite its potential to prevent leakage and preserve battery flexibility. Herein, a Ca(BH4)2-based gel-polymer electrolyte (GPE) is prepared from Ca(BH4)2 and poly(tetrahydrofuran) (pTHF) and tested its performance in Ca batteries. The electrolyte demonstrates excellent stability against Ca-metal anodes and high ionic conductivity. The results of infrared spectroscopy and 1H and 11B NMR indicate that the terminal ─OH groups of pTHF reacted with BH4 - anions to form B─H─(pTHF)3 moieties, achieving cross-linking and solidification. Cyclic voltammetry measurements indicate the occurrence of reversible Ca plating/stripping. To improve the performance at high current densities, the GPE is supplemented with LiBH4 to achieve a lower overpotential in the Ca plating/stripping process. An all-solid-state Ca-metal battery with a dual-cation (Ca2+ and Li+) GPE, a Ca-metal anode, and a Li4Ti5O12 cathode sustained >200 cycles, confirming their feasibility. The results pave the way for further developing lithium salt-free Ca batteries by developing electrolyte salts with high oxidation stability and optimal electrochemical properties.

In Situ Polymerized Zwitterionic Copolymer Ionic Gel Electrolytes with High Performance for Lithium-Ion Batteries.

Gel electrolytes are a promising research direction due to their high safety. However, its poor room temperature conductivity along with complex preparation process hinder its practical application. In this article, a type of zwitterionic gel electrolyte is prepared by in situ polymerization. The introduction of charged but nonmigrating zwitterionic copolymer in the polymer chain is beneficial to the dissociation of the lithium salt, improving the ion transport of the electrolyte on this account. At room temperature, the conductivity of lithium ion reaches 9.1 × 10-4 S cm-1, which contributes to achieve excellent electrochemical performance at high rates. The assembled Li|LiFePO4 cell also shows a capacity retention rate of 90.5% after 150 cycles at 0.5 C at room temperature as well as remarkable cycle stability at 1 C. These offer a novel tactic for the efficient and safe commercial application of lithium-ion batteries.

High performance gel polymer electrolyte based on P(MMA-co-Sty) and PVDF blend for fast-charging lithium metal batteries with extended cycle life

In the quest for high-energy-density lithium metal batteries (LMBs), the stabilization of lithium (Li) metal anodes during fast charging remains a formidable challenge. In this study, a novel copolymer, Poly(methyl methacrylate-co-styrene) (namely PMS) is synthesized and blended with Poly(vinylidene fluoride) to fabricate a porous gel polymer electrolyte (GPE, namely PMS-PVDF) through the nonsolvent-induced phase separation technique, which significantly enhances the electrochemical stability and fast-charging capabilities of LMBs. The developed GPE exhibits a high ionic conductivity of 5.62 mS cm−1, thereby reducing the formation of detrimental Li dendrites and leading to over 400 h stripping/plating process at 0.5 mA cm−2. Extensive electrochemical tests show that the LMBs with the obtained PMS-PVDF GPE achieve exceptional cycle stability over 600 and 1000 cycles at the C-rates of 0.5 and 3 C, respectively, outperforming traditional electrolytes. Furthermore, the ultra-stability of the quasi-solid-state electrolyte is demonstrated in a 375 mAh pouch cell setup, suggesting an essential trait for the practical application of high-power devices. This work marks a pivotal contribution to the field of energy storage, delivering insights and a clear methodology that pave the way for the development of next-generation LMBs poised for commercial viability.

Enhancing dye-sensitized solar cell performance; optimization of quaternary counterion-based gel polymer electrolyte without changing additives or net-ion composition

Enhancing dye-sensitized solar cell performance; optimization of quaternary counterion-based gel polymer electrolyte without changing additives or net-ion composition

Carboxymethyl Cellulose – Polyvinyl Alcohol Composite-Based Gel Polymer Electrolyte for Rechargeable Zn-Air Batteries

The high ionic conductivity, lower interfacial contact resistance, enhanced safety, non-toxicity, and biodegradability bring the gel polymer electrolytes (GPEs) as a prospective electrolyte for applications in high-energy density flexible Zn-air batteries (ZABs). The present study comprehensively optimizes the procedures to obtain carboxymethyl cellulose (CMC)–polyvinyl alcohol (PVA) composite-based GPEs holding a maximum KOH amount in the polymer matrix. Optimization of the GPE has been performed and demonstrated by an in-house-developed rechargeable ZAB cells using MnO2-based air cathode and Zn anode. The optimization parameters include the ratio of PVA:CMC, concentration of PVA-CMC in DI water, and thickness of the gel polymer electrolyte. Results show that a 4mm thick GPE prepared from a polymer membrane synthesized using PVA:CMC ratio of 5:2 at a concentration of 0.063 g ml−1 in DI water displayed the highest 6M KOH uptake, least charge transfer resistance of the device, higher discharge plateau, and 5–6 times more cycling compared to GPE made of PVA only. The “as-synthesized GPE” demonstrates high stability of GPE over 100h for a Zn-air battery device. The findings of this work shall speed up the development of Zn air batteries for applications as energy storage systems.

Unveiling the role of electrolyte to promote enhanced proton storage stability in WO3 for energy storage

In the present work, we systematically investigate the phenomenon of electrochemical proton storage in WO3 and subsequently demonstrate a strategy for enhancing the cycle life for proton storage. It was carried out in three different electrolytes medium based on H3PO4, H2SO4 and HCl. It was found that although H3PO4 can promote better cycling stability and high rate capability than HCl and H2SO4, there still persists an issue in achieving large number of charge/discharge cycles. The typical proton storage capacitance of WO3 in 3.75 M H3PO4 is estimated to be around 288–346 F g−1 at a current rate of 0.5 A g−1 over 30 cycles. The cycling stability could, however, be significantly improved by the utilization of gel electrolyte which is basically a mixture of H3PO4 and polyvinyl alcohol (PVA) of different concentrations. For example, the estimated proton storage capacitance is around 287 F g−1 in 3.75 M H3PO4-PVA gel electrolyte (1:8 wt %) over 100 cycles at a current density of 0.5 A g−1. On the basis of the improved proton storage stability in the gel electrolyte, the electrochemical performance of a proton storage full cell with WO3 and V10O24.12H2O as electrodes is also illustrated. Another important revelation is the drastic reduction of the self-discharge rate of the full cell in the gel electrolyte in comparison to pristine aqueous medium electrolyte.

Evaluation of the addition of cement ash to the PVA/TEOS/HCl gel electrolyte on the performance of aluminium air batteries

Cement manufacturing presents substantial environmental challenges due to the volume of waste generated, including cement ash. Therefore, it is crucial to discover novel methods to utilize cement waste effectively. This study aimed to examine the impact of different concentrations of cement ash (1, 1.5, 2, and 2.5 g) on the conductivity of PVA/TEOS/HCl (PTH) gel electrolyte materials. The primary goal was to determine the ideal concentration of cement ash that would yield maximum conductivity. The research findings demonstrated that the PTH2.5CA sample attained the greatest conductivity of 2.78 mS/cm when adding 2.5 g of cement ash. In addition, this material exhibits a capacity of 0.354 mAh, a specific capacity of 0.12826 mAh/g, and a density capacity of 0.11813 mAh/cm2. The power and power densities were measured as 6.48 mW/cm2 and 25.94 mW, respectively. These findings offer promising prospects for implementing sustainable practices in the industry and highlight the viability of utilizing cement waste as a significant element in battery membrane materials. This technique addresses environmental issues related to cement waste and contributes to advancing a more eco-friendly waste management system.

High-performance zinc-ion hydrogel electrolytes based on molecular-level hybridization of PVA with polymer quantum dots

Aqueous zinc ion batteries have received widespread attention. However, the growth of zinc dendrites and hydrogen evolution reaction generation seriously hinder the practical application of zinc ion batteries. Herein, it is reported that a multifunctional dendrites-free low-temperature PVA-based gel electrolyte by introducing negatively charged polymer carbon quantum dots (QDs) and the organic antifreeze dimethyl sulfoxide (DMSO) into it. The QDs carrying a large number of functional groups on the surface can effectively adsorb Zn2+, eliminating the “tip effect”, and inducing the uniform deposition of Zn2+ and the formation of a dendrites-free structure. Meanwhile, the solvation structure of adsorbed Zn2+ can be controlled by charged groups to reduce the generation of side reactions, thus obtaining high-performance zinc ion batteries. The Zn/polyaniline (PANi) full battery can be stably cycled more than 1000 times at –20 °C, and the design of this gel electrolyte can provide good feasibility for safe, stable, and flexible energy storage devices.