Replacement Of Liquid Electrolytes Research Articles

Synthesis and Characterizations of Novel Copolymers with Zwitterionic Moiety-Based Solid Polymer Electrolytes for Solid-State Lithium Metal Battery

Electric vehicles (EVs) have become the dominant choice in the automotive industry, displacing internal combustion engine vehicles (ICEVs) to some extent. The development of high-efficiency batteries is essential to meet these market demands. Conventional lithium-ion batteries (LIBs), which consist of a cathode, anode, separator, and liquid electrolyte (such as 1M LiPF6 in carbonate solvents), have been widely utilized in portable electronic devices, hybrid electric vehicles (HEVs), and EVs. This popularity is attributed to their relatively high energy density and extended cycle life [1]. However, LIBs with energy density exceeding 240 Wh kg-1 face challenges in terms of thermal stability, potentially leading to fire and explosions by overcharging or accidental cell penetration. This drawback significantly hinders their application in automotive settings [2, 3]. In response to these safety concerns, there is a shift towards incorporating solid-state electrolytes (SSEs) as a replacement for liquid electrolytes. SSEs include solid polymer electrolyte (SPE), inorganic solid electrolyte (ISE), and composite polymer electrolyte (CPE).Solid-state lithium metal batteries (SSLMBs) incorporating SPE hold significant promise for advancing energy storage technologies due to their high energy density and improved safety features. However, the low ionic conductivity and ionic transference number of SPEs present challenges in their application for solid-state batteries. This work focuses on designing novel copolymers with polar soft unit and zwitterionic unit to address these challenges.In this study, poly(ethylene glycol) methyl ether acrylate (PEGMEA) and sulfobetaine methacrylate (SBMA) were selected as the polar soft segment and zwitterionic unit, respectively. Various ratios of PEGMEA/SBMA in copolymers were synthesized and characterized, and the resultant SPEs consisting of resultant copolymers and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were prepared. Subsequently, their electrochemical, thermal, mechanical, and morphological properties were systematically investigated. The copolymers-based SPEs exhibited improved electrochemical properties. The optimized SPE comprising the copolymer with the molar ratio of PEGMEA/SBMA = 1/3 and 50 wt% LiTFSI exhibited the ionic conductivity of approx. 2×10–4 S cm–1, lithium-ion transference number of approx. 0.3, Li+ diffusion coefficient of 15×10-12 cm² s-1, and oxidation stability of 5.2 V (vs. Li/Li+) at 25 oC. Additionally, the mechanical properties of such SPEs were assessed, showing improved tensile strength (up to approx. 6 MPa) and Young’s modulus (up to approx. 83 MPa) with increasing SBMA content. The selected SPE with the best electrochemical properties was sandwiched between a Li metal electrode and a LiFePO4 electrode to assemble a SSLMB. As a result, the discharge capacity (DC) at 0.1 C-rate and room temperature was approx. 170 mA h g–1. Furthermore, the DC at a 0.5 C-rate was approx. 146 mA h g–1, and the capacity retention of 70% obtained after 470 cycles. In summary, this work demonstrates the potential of tailored copolymers with zwitterionic moiety-based SPEs for SSLMB. The comprehensive characterization and performance assessments provide valuable insights into the design and optimization of polymer electrolytes for next-generation energy storage systems.The copolymers and corresponding SPEs underwent characterization through various techniques such as DSC, SEM, XRD, and FTIR. The Ionic conductivity of the SPEs was determined by analyzing the results obtained from EIS measurement. The lithium-ion diffusion coefficient (DLi+) for SPE in a symmetric SSLMB cell, Li/SPE/Li, was also calculated based on the EIS results [4]. The oxidation stability window of the SPE was measured using the linear sweep voltammetry technique, and the ion transfer number was determined using the Evans-Vincent-Bruce method [5].

High-performance fibre battery with polymer gel electrolyte.

Replacement of liquid electrolytes with polymer gel electrolytes is recognized as a general and effective way of solving safety problems and achieving high flexibility in wearable batteries1-6. However, the poor interface between polymer gel electrolyte and electrode, caused by insufficient wetting, produces much poorer electrochemical properties, especially during the deformation of the battery7-9. Here we report a strategy for designing channel structures in electrodes to incorporate polymer gel electrolytes and to form intimate and stable interfaces for high-performance wearable batteries. As a demonstration, multiple electrode fibres were rotated together to form aligned channels, whilethe surface of each electrode fibre was designed with networked channels. The monomer solution was effectively infiltrated first along the aligned channels and then into the networked channels. The monomers were then polymerized to produce a gel electrolyte and form intimate and stable interfaces with the electrodes. The resulting fibre lithium-ion battery (FLB) showed high electrochemical performances (for example, an energy density of about 128 Wh kg-1). This strategy also enabled the production of FLBs with a high rate of 3,600 m h-1 per winding unit. The continuous FLBs were woven into a 50 cm × 30 cm textile to provide an output capacity of 2,975 mAh. The FLB textiles worked safely under extreme conditions, such as temperatures of -40 °C and 80 °C and a vacuum of -0.08 MPa. The FLBs show promise for applications in firefighting and space exploration.

Role of Interfaces in Solid-State Batteries.

Solid-state batteries (SSBs) are considered as one of the most promising candidates for the next-generation energy-storage technology, because they simultaneously exhibit high safety, high energy density, and wide operating temperature range. The replacement of liquid electrolytes with solid electrolytes produces numerous solid-solid interfaces within the SSBs. A thorough understanding on the roles of these interfaces is indispensable for the rational performance optimization. In this review, the interface issues in the SSBs, including internal buried interfaces within solid electrolytes and composite electrodes, and planar interfaces between electrodes and solid electrolyte separators or current collectors are discussed. The challenges and future directions on the investigation and optimization of these solid-solid interfaces for the production of the SSBs are also assessed.

Gel Polymer Electrolyte Based on Methyl Methacrylate for Lithium-Sulfur Batteries

Lithium-sulfur batteries are next-generation battery systems with low cost and high specific energy. However, it is necessary to solve several deficiencies of these batteries such as shuttle effect, and gel polymer electrolyte is a great candidate. These perspective materials can be used as a replacement for liquid electrolytes, and at the same time, they can help to solve the problems of lithium-sulfur batteries. In this work, gel polymer electrolyte (GPE) based on methyl methacrylate was prepared by cross-linking strategy. As cross-link ethylene glycol dimethacrylate (EDMA) was used. Prepared gel with a high electric conductivity was testing in the lithium-sulfur cell (Li/GPE/S). The electrochemical performance of the cell was studied.

Polymer Electrolytes - New Opportunities for the Development of Multivalent Ion Batteries.

Batteries, as highly concerned energy conversion system, have a great development prospect in various fields, especially in the field of energy powered vehicles. Multivalent ion batteries are getting more attention due to their low cost, high abundance in earth crust, high capacity and safety compared with Lithium batteries. Despite above advantages, several problems still need to be solved before multivalent ion batteries achieve large-scale application, such as interfacial parasitic reaction, anode passivation, and dendrites. The replacement of liquid electrolytes with gel polymer electrolytes (GPEs) which pose high safety, high mechanical strength and simplified battery system, is an effective strategy to inhibit dendrite growth and improve electrochemical performance. This review mainly discusses the advantages and challenges of multivalent ion batteries including zinc, magnesium, calcium and aluminum batteries. Meanwhile, the major targets of this review are introducing the recent developments and making a summary of the future trends of GPEs in the multivalent ion batteries.

OPTIMIZATION OF Cu2O AND CuSCN AS HTL OF PLANAR PEROVSKITE SOLAR CELLS VIA NUMERICAL SIMULATION

Perovskite solar cells have gained a great deal of interest as it has low cost, suitable electronic and optical properties, and strong light absorption. Since the replacement of liquid electrolyte in 2012, there has been a need to optimize the Hole Transport Layer (HTL) to achieve higher efficiency. Copper Thiocyanate (CuSCN) and Cuprous Oxide (Cu2O) are inorganic HTLs, which have a bandgap of 3.4eV and 2.17eV respectively are abundant, non-toxic, and suitable for band matching. Using CuSCN and Cu2O as an electron blocking layer allows for reducing manufacturing cost and improving solar cell performance. Inorganic HTLs such as CuI and NiO are proven to have good stability, low cost, and high mobility. Currently, organic HTLs such as Spiro MeOTAD produce higher efficiency, however, they have poor thermal stability. This work looks into optimizing the CuSCN and Cu2O as an HTL to replace the expensive Spiro MeOTAD, which incurs high manufacturing costs. Using SCAPS-1D software, an efficiency of 21.5% was achieved by varying the parameters of the HTL and absorber layer. The results indicate that CuSCN is a better HTL compared to Cu2O.

Oxygen- and dendrite-resistant ultra-dry polymer electrolytes for solid-state Li–O2 batteries

Utilizing polymer electrolytes in Li–O2 batteries could effectively solve safety issues caused by flammable liquid electrolytes. However, the effect of polymer matrixes and additional liquid electrolytes on the cycle performance of Li–O2 batteries is still not clear. Herein, free-standing, Li-ion conducting ultra-dry polymer electrolytes (UDPEs) without additional liquid electrolytes are synthesized by a simple tape-casting and vacuum-drying method. The long-term cycle performance (over 800 ​h) of the UDPE-based symmetric Li–Li cells in O2 atmosphere demonstrates that the UDPEs significantly resist O2 crossover and Li dendrite penetration. Moreover, side reactions caused by the degradation of liquid electrolytes can be alleviated and a stable LiF-containing solid electrolyte interface is formed between the UDPEs and Li metal. Meanwhile, the cycle life of the UDPE-based catalyst-free Li–O2 batteries under a high current density of 0.4 ​mA ​cm-2 is improved by more than twofold in comparison with that of the liquid electrolyte-based Li–O2 batteries. The replacement of liquid electrolytes by UDPEs does not change the fundamental reaction of the solid-state Li–O2 batteries, which is still the formation and decomposition of typical Li2O2 crystals. The outstanding comprehensive performance of UDPEs may trigger further studies towards multifunctional polymer electrolytes in Li–O2 batteries and even other alkali metal-based O2 (air) batteries.

Effect of NASICON-type LiSnZr(PO4)3 ceramic filler on the ionic conductivity and electrochemical behavior of PVDF based composite electrolyte

Replacement of liquid electrolytes with polymer-based solid electrolytes is considered as the key to the realization of high-energy lithium metal anode in rechargeable batteries. However, the polymer electrolytes suffer from poor lithium-ion conductivity and low lithium-ion transference number. Poly(vinylidene difluoride) (PVDF) based polymer-ceramic composite electrolytes were fabricated at room temperature via the solution casting method. The effect of NASICON-type lithium tin zirconium phosphate (LiSnZr(PO4)3) particles added as the ceramic filler to the PVDF + LiTFSI polymer-salt matrix on the structure, ionic conductivity, transference number, and electrochemical behaviour was studied. The x-ray diffraction (XRD) and fourier transform infrared (FTIR) absorption studies confirmed the structure of the fabricated polymer as the mixed (α+β) phases of PVDF. The addition of LiSnZr(PO4)3 ceramic filler resulted in the enhancement in Li+ conductivity of the polymer composite and the sample with 15 wt% ceramic filler (CPE-15) showed the highest lithium-ion conductivity of 5.76 × 10−5 Scm−1 at 300 K. The addition of 15 wt% LSZP improved the stability window up to 4.73 V as confirmed by linear sweep voltammetry (LSV). A significant improvement in (tLi+) resulted from the addition of ceramic filler. The reversibility of Li+ transport across the composite ceramic-polymer electrolyte (15 wt% CPE) was confirmed by galvanostatic charging-discharging of symmetric lithium (Li||CPE||Li) cell at various current density for 100 h. Li||CPE||LTO cells with Li4Ti5O15 (LTO) as the working electrode, CPE-15 as the Li+ conducting separator, and Li foil as the counter electrode were fabricated to demonstrate the application of the CPE-15 as the electrolyte in all-solid-state batteries. Li||CPE||LTO cell delivered a specific discharge capacity of 133 mAhg−1 and 88% capacity retention after 20 cycles at 0.1C rate.

New Class of Solid State Electrolytes for Batteries: Correlating Structure to Functional Properties

Growing energy demand and depletion of fossils fuels results in requirement of electrochemical devices with high energy density, smart miniaturisation to store energy in lower area. These are coupled with safety concern which is mitigated via replacement of liquid electrolytes with polymeric and solid-state electrolytes. Exploration of novel class of electrolytes with good ionic conductivity, high thermal stability and mechanical integrity not only address safety concern of devices but also adds up possibility of exploring new processing technology. In this regard, we demonstrate here a new class of borohydride-based ion conductors based on bimetallic anion-substituted borohydrides, as a potential solid-state electrolyte. The pertinent structure-property relationships will be discussed as a function of structural parameters (metallic substitution, anionic substitution and doping) of the solid like electrolytes. They show appreciable ionic conductivity (σ ~10-4 S cm-1 at 298 K) and and wide electrochemical window, pertinent to the battery application. Preliminary electrochemical results on solid state battery assembly will be presented briefly. The solid-state electrolyte work will be coupled with soft material-based electrolytes as potential electrolyte/lithium protecting layers will also be discussed in application of lithium based solid state batteries. A special attention will be given to fundamental transport properties and correlating the key physical design strategies of new ionic conductors to their physico-chemical properties.

Electrochemical Properties of Assbs with High Energy Density Using Thin Solid Electrolyte Sheet

Recently, the use of liquid electrolytes in lithium batteries is prone to cause safety problems such as leakage and gas explosions. The PEO-based solid composite electrolytes (CE) for all-solid state batteries (ASSBs) have been studied for a possible replacement for liquid electrolytes. However, it results in degradation of mechanical properties and short circuit during cycling at the high temperature (60~80°C). Therefore, the thickness of electrolytes is required to be 150㎛ or more. However, to improve the energy density of all-solid state battery, it is required to reduce the thickness of the solid electrolyte layer to as low as 50㎛ and less. As a method for reducing the thickness, we suggested that the thin solid composite electrolyte film was composed of PEO/PVDF blending polymer as ionic conductor and binder including lithium salts and garnet LLZO powders. In addition, the composite cathode slurry was composed of NCM active material, Super P, Garnet-type LLZO powder and PEO/PVDF blending polymer. The electrochemical properties were measured by the AC impedance method, Linear Sweep Voltammetry, Symmetrical cell test and charge/discharge cell test. As a result, we will introduce the properties of CE with garnet LLZO powder, PEO and PVDF polymers in cathode and solid electrolyte layer. Finally, a pouch-type ASSBs having a bipolar structure in which energy density is improved by applying such a thin SE is described in more detail.

Efficiency enhancement study on addition of 1-hexyl-3-methylimidazolium iodide ionic liquid to the poly(methyl methacrylate-co-methacrylic acid) electrolyte system as applied in dye-sensitized solar cells

The replacement of liquid electrolytes with gel polymer substituents in dye-sensitized solar cells (DSSCs) has become an accepted strategy not only to overcome problems encountered previously but also to increase the shelf life and photovoltaic performance of DSSCs. In that perspective, a gel polymer electrolyte system based on poly(methyl methacrylate-co-methacrylic acid), P(MMA-co-MAA), was prepared with iodine/iodide redox mediator from a sodium salt and the commercially available ionic liquid 1-hexyl-3-methylimidazolium iodide (HMIm+I−) and was studied for its ionic conductivity and energy conversion efficiencies along with structural investigation of the complex by Fourier transform infrared spectroscopy and X-ray diffraction. The highest conductivity achieved was 2.33 mS cm−1 at room temperature for the gel polymer electrolyte with 20 wt% HMIm+I−. With a generic DSSC arrangement of TiO2 sensitized with N719 dye photoanode/electrolyte/Pt-containing counter electrode, the copolymer-based conducting electrolyte displayed power conversion efficiency of 5.30% under illumination of 100 mW cm−2.

Fabrication of Li-Polymer/Silica Aerogel Nanocomposite Electrolyte for an All-Solid-State Lithium Battery

The demand for solid-state lithium ion electrolytes has increased owing to the safety concerns regarding the use of lithium ion batteries, which contain flammable organic solvent electrolytes. The liquid electrolyte can give rise to serious problems such as leakage and gas explosions when the operating temperature rises. The use of an organic or inorganic solid electrolyte not only results in improved safety, but also facilitates the fabrication of miniature batteries using thin films. A solid electrolyte is required to have high lithium ion conductivity, mechanical strength, and transference number for lithium ions as well as good thermal/electrochemical stability and compatibility with the electrodes. Recently, polymer-based solid electrolytes have been widely studied for a possible replacement for liquid electrolytes. Various types of polymer-based solid electrolytes for lithium ion batteries exist, such as polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), and polyvinylidene fluoride (PVDF). Among them, the PEO-based polymer has attracted considerable attention, owing to its flexible skeleton and good interfacial stability with lithium electrodes. The mechanism of lithium ion conduction in the PEO-based solid-polymer electrolyte involves the coordination of the lithium ion from the Li-salt by the ether oxygen from the PEO, which moves according to the polymer segmental motion. In this study, a polymer blend of PEO and PVDF, containing fluorine as a polar element, was fabricated to improve the dissociation degree of the Li-salt. In addition, we anticipate that the addition of ultra-porous silica aerogels, which has a high porosity and specific surface area, would increase the lithium ion conductivity. The silica aerogel was fabricated from water glass using the emulsion polymerization method, as was previously described by our research group. We also investigated the effects of the PEO:PVDF molar ratio, polymer:Li-salt molar ratio, and silica aerogel content on the structural, thermal, and electrical properties.

Fabrication Characteristics of Thin Solid Composite Electrolyte Film Sheet for Solid-State Lithium Battery

Recently, the use of liquid electrolytes in lithium batteries is prone to cause safety problems such as leakage and gas explosions. The PEO-based solid composite electrolytes have been studied for a possible replacement for liquid electrolytes. However, it results in degradation of mechanical properties and short circuit during cycling at the high temperature above 70°C. Therefore, the thickness of electrolytes is required to be 200㎛ or more. As a method for reducing the thickness, the composite slurry, which was composed of polymer ionic conductor, lithium salts and Garnet-type LLZO, was filled in a porous polyester nonwoven. And then, it was rolled at a constant ratio to have a thickness of 50~100㎛. The morphology of the solid composite electrolyte film sheet was observed using SEM. Furthermore, the electrochemical properties were measured by the AC impedance method and charge/discharge cell test.

(Invited) Highly Stabilized Perovskite Solar Cells By Li-Ion-Containing Fullerene Salt As Both Dopant and Anti-Oxidant

Lead halide perovskite solar cells (PSCs) have drawn great attention as the promising solar energy source in recent years. Their certified power conversion efficiencies (PCEs) now reach more than 20%. Despite high PCE, low stability of PSCs has been the most serious drawback, which is in dire need of resolution. It has been found that light, oxygen, and water are the origins of the perovskite layer degradation. In particular, dopants used for 2,2’,7,7’-tetrakis(N,N-di-p-methoxyphenylamine)-9,9’-spirobi-fluorene (spiro-MeOTAD) hole-transporting material are attributed for the low stability, due to their hygroscopic nature. Replacement of liquid electrolyte by spiro-MeOTAD was a breakthrough at the initial stage of PSC development, improving PCE substantially, owing to well-aligned energy band and amorphous nature of spiro-MeOTAD. However, because spiro-MeOTAD intrinsically has low mobility, a dopant must be present to improve the conductivity. Lithium bis(trifluoromethanesulfonyl)imide salt (Li+TFSI−) has been widely used as the p-dopant for spiro-MeOTAD. Li+TFSI− does not directly oxidize spiro-MeOTAD, but instead, promotes the oxidation of spiro-MeOTAD by oxygen at the presence of light or thermal excitation. Because doping spiro-MeOTAD with Li+TFSI− requires oxygen, it is difficult to control the amount of spiro-MeOTAD oxidation; the formation of oxidized spiro-MeOTAD has been shown to be reversible during device operation depending on ambient conditions and the sweep direction of current−voltage (J −V) measurement. Also, a number of factors, including light intensity, the concentrations of lithium ions and oxygen, has been shown to the amount of oxidized spiro-MeOTAD. Uncontrolled oxidized spiro-MeOTAD is unpredictable and leads to inconsistent reproducibility and instability of PSCs. In addition to this, as mentioned above, Li+ salt is extremely hygroscopic and induces moisture-based degradation of PSCs. In this work, lithium-ion-encapsulated [60]fullerene bis(trifluoromethanesulfonyl)imide salt ([Li+@C60]TFSI−) was used in PSCs instead of Li+TFSI− as a solution aforementioned problems. C60 encapsulating Li+ changed the hydrophilic alkali salt to a hydrophobic species. Also, spiro-MeOTAD mixed with [Li+@C60]TFSI−produced cationic salt spiro-MeOTAD●+TFSI− and neutral Li+@C60 ●− by electron transfer from spiro-MeOTAD to Li+@C60. While spiro-MeOTAD●+TFSI−functioned as an effective hole transporting material Li+@C60 ●− functioned as an antioxidant, reacting with any intruding oxygen and moisture. spiro-MeOTAD●+TFSI− required no chemical additives nor oxidation as it was technically pre-oxidized spiro-MeOTAD. By preventing unnecessary oxidation in the device system, [Li+@C60]TFSI−-used devices showed approximately 10 times higher stability than the conventional Li+TFSI−-used devices. Figure 1

Progress and Perspective of Solid‐State Lithium–Sulfur Batteries

AbstractDue to high energy density, low cost, and nontoxicity, lithium–sulfur (Li–S) batteries are considered as the most promising candidate to satisfy the requirement from the accelerated development of electric vehicles. However, Li–S batteries are subjected to lithium polysulfides (LiPSs) shuttling due to their high dissolution in liquid electrolyte, resulting in low columbic efficiency and poor cycling performance. Moreover, the Li metal as an indispensable anode of Li–S batteries shows serious safety issues derived from the lithium dendrite formation. The replacement of liquid electrolytes with solid‐state electrolytes (SSEs) has been recognized as a fundamental approach to effectively address above problems. In this review, the progress on applying various classes of SSEs including gel, solid‐state polymer, ceramic, and composite electrolytes to solve the issues of Li–S batteries is summarized. The specific capacity of Li–S batteries is effectively improved due to the suppression of LiPSs shuttling by SSEs, while the rate and cycling performance remain relatively poor owing to the limited ionic conductivity and high interfacial resistance. Designing smart electrode/electrolyte integrated architectures, enabling the high ionic transportation pathway and compatible electrode/electrolyte interface, may be an effective way to achieve high performance solid‐state Li–S batteries.

Investigation of polyacrylamide based hydroxide ion-conducting electrolyte and its application in all-solid electrochemical capacitors

A hydroxide ion-conducting polymer electrolyte using tetraethylammonium hydroxide and polyacrylamide as a replacement for liquid electrolytes in supercapacitors.

ChemInform Abstract: Perovskite Solar Cells: Influence of Hole Transporting Materials on Power Conversion Efficiency

AbstractReview: 89 refs.

Perovskite Solar Cells: Influence of Hole Transporting Materials on Power Conversion Efficiency.

The recent advances in perovskite solar cells (PSCs) created a tsunami effect in the photovoltaic community. PSCs are newfangled high-performance photovoltaic devices with low cost that are solution processable for large-scale energy production. The power conversion efficiency (PCE) of such devices experienced an unprecedented increase from 3.8 % to a certified value exceeding 20 %, demonstrating exceptional properties of perovskites as solar cell materials. A key advancement in perovskite solar cells, compared with dye-sensitized solar cells, occurred with the replacement of liquid electrolytes with solid-state hole-transporting materials (HTMs) such as 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD), which contributed to enhanced PCE values and improved the cell stability. Following improvements in the perovskite crystallinity to produce a smooth, uniform morphology, the selective and efficient extraction of positive and negative charges in the device dictated the PCE of PSCs. In this Review, we focus mainly on the HTMs responsible for hole transport and extraction in PSCs, which is one of the essential components for efficient devices. Here, we describe the current state-of-the-art in molecular engineering of hole-transporting materials that are used in PSCs and highlight the requisites for market-viability of this technology. Finally, we include an outlook on molecular engineering of new functional HTMs for high efficiency PSCs.