Polymer Electrolytes For Lithium Ion Batteries Research Articles

Cellulose-based eutectogel electrolyte with high ionic conductivity for solid-state lithium-ion batteries

It is known that the low ionic conductivity of solid-state polymer electrolytes at room temperature (RT) has severely restricted their practical application in lithium-ion batteries. Although eutectogel (ETG) electrolytes could solve this problem to some extent, highly compatible deep eutectic solvent (DES)/polymer systems are desirable to further enhance ion conduction. Herein, we designed cellulose-based ETG (CETG) with dual channels through “hopping” and “vehicle” mechanisms by hydroxyethyl cellulose (HEC) molecular chains and N-methylacetamide (NMA)/LiTFSI-derived DES, respectively. Thanks to the strong molecular interactions between HEC and DES, the highest DES content in the ETG could achieve 90 %, which endowed the CETG with an excellent ionic conductivity of 2.04 × 10–3 S cm−1 at 30 °C. Additionally, our designed CETG displayed good self-healing and fire retardant properties. The assembled Li/LiFePO4 cell showed a capacity retention of 91.8 % after 200 cycles at 0.2 C under RT with an initial discharge capacity of 156.2 mAh g−1. In particular, the capacity retention rates of the assembled batteries reached 95.2 % and 92.1 %, respectively, after 100 cycles at 0.2 C under 60 °C and 50 cycles at 0.2 C under 100 °C. Our fabrication strategy would provide a novel idea for the design of green, safe and efficient solid-state polymer electrolytes for lithium-ion batteries.

A strong nucleophilic fluorination agent to achieve highly stable in-situ 3D cross-linked gel polymer electrolyte for lithium-ion batteries

The Gel Polymer Electrolyte (GPE) is recognized as a promising alternative to conventional electrolytes, aiming to enhance the longevity and energy density of lithium-ion batteries (LIBs). However, several challenges persist, particularly concerning the conductivity and voltage window of GPE in battery systems. In this study, we introduce an in-situ 3D crosslinked GPE, using polymethyl methacrylate (PMMA) as the monomer and polyethylene glycol dimethacrylate (PEGDMA) as the crosslinking agent, to ensure structural stability and optimized ion conductivity. We also incorporate a potent nucleophilic fluorination agent, Tetrabutylammonium fluoride (TBAF), to augment the compatibility and oxidation resistance of the formulated FGPPE. The recurring (–CH2CH2O-) units of PEGDMA, coupled with in-situ lithium fluoride (LiF) and C-F groups introduced by TBAF, endow the FGPPE with a remarkable ionic conductivity of 7.8 mS cm−1 and a distinctly electrochemical stability of 4.65 V. Notably, the Li metal anode, featuring an F-rich solid-state interface (SEI), demonstrates uniform Li+ deposition, sustaining a cycling life of 1000 h and maintaining a commendable average coulomb efficiency of 98.5 % over 300 cycles. Additionally, the NCM811/SiC pouch cell integrated with FGPPE showcases superior cycling stability, retaining 99.4 % of its capacity after 600 cycles at an elevated voltage of 4.45 V. Such advancements in gel polymer electrolyte design can significantly expedite the commercial deployment of gel polymer Li-ion batteries.

Nonflammable Gel Polymer Electrolyte for Lithium-Ion Batteries with Enhanced Safety and High-Temperature Performance

Lithium-ion batteries (LIBs) have become dominant power sources for various applications such as mobile electronics, electric vehicles and energy storage systems. However, liquid electrolytes currently used in LIBs have critical drawbacks such as flammability and leakage problem. In this regard, various electrolyte systems have been developed to enhance the battery safety while maintaining cycling performance. Among them, the chemically cross-linked gel polymer electrolytes (GPEs) can enhance the thermal safety of LIBs by effectively encapsulating organic solvents in the polymer matrix. However, they usually contain large amounts of organic solvents to achieve high ionic conductivity, making GPE be still flammable. To solve these problems, we designed and synthesized a novel phosphorus-based cross-linking agent with excellent flame retardancy. GPE was prepared by in-situ thermal curing of gel precursor containing liquid electrolyte and phosphorus-based cross-linking agent. The obtained GPE exhibited high ionic conductivity and nonflammability. The GPE was applied to lithium-ion cells composed of graphite anode and LiNi0.6Co0.2Mn0.2O2 cathode. Our results revealed that the lithium-ion cell employing GPE exhibited enhanced safety and improved high-temperature cycling performance compared to the cell with the liquid electrolyte.

Gel Polymer Electrolytes for Lithium-Ion Batteries Enabled by Photo Crosslinked Polymer Network.

We demonstrate a gel polymer electrolyte (GPE) featuring a crosslinked polymer matrix formed by poly(ethylene glycol) diacrylate (PEGDA) and dipentaerythritol hexaacrylate (DPHA) using the radical photo initiator via ultraviolet (UV) photopolymerization for lithium-ion batteries. The two monomers with acrylate functional groups undergo chemical crosslinking, resulting in a three-dimensional structure capable of absorbing liquid electrolytes to form a gel. The GPE system was strategically designed by varying the ratios between the main polymer backbone (PEGDA) and the crosslinker (DPHA) to achieve an optimal gel polymer electrolyte network. The resulting GPE exhibited enhanced thermal stability compared to conventional liquid electrolytes (LE) and demonstrated high ionic conductivity (1.40 mS/cm) with a high lithium transference number of 0.65. Moreover, the obtained GPE displayed exceptional cycle performance, maintaining a higher capacity retention (85.2%) comparable to the cell with LE (79.3%) after 200 cycles.

Enhanced performance of electrospun poly(ethylene oxide)/reduced graphene oxide polymer electrolyte for lithium-ion batteries

A novel polymer membrane based on electrospun poly(ethylene oxide) (PEO) incorporated with different concentrations of reduced graphene oxide (rGO) was prepared using the electrospinning technique. The electrospun PEO/rGO was incorporated with lithium ions to manufacture a gel polymer electrolyte (GPE) and sandwiched inside a coin cell. The electrochemical properties of PEO/rGO electrolytes confirmed good stability of the lithium cell, a satisfactory lithium transference number and improved ionic conductivity in the order of 10−3 S/cm. The GPE developed in this work is well suited for application in reliable, low-cost and eco-friendly energy storage technologies.

Study of poly (organic palygorskite-methyl methacrylate)/poly(vinylidene fluoride-co-hexafluoropropylene) blended gel polymer electrolyte for lithium-ion batteries

Study of poly (organic palygorskite-methyl methacrylate)/poly(vinylidene fluoride-co-hexafluoropropylene) blended gel polymer electrolyte for lithium-ion batteries

Automated Design of Li+ -Conducting Polymer by Quantum-Inspired Annealing.

Automated molecule design by computers is an essential topic in materials informatics. Still, generating practical structures is not easy because of the difficulty in treating material stability, synthetic difficulty, mechanical properties, and other miscellaneous parameters, often leading to the generation of junk molecules. The problem is tackled by introducing supervised/unsupervised machine learning and quantum-inspired annealing. This autonomous molecular design system can help experimental researchers discover practical materials more efficiently. Like the human design process, new molecules are explored based on knowledge of existing compounds. A new solid-state polymer electrolyte for lithium-ion batteries is designed and synthesized, giving a promising room temperature conductivity of 10-5 S cm-1 with reasonable thermal, chemical, and mechanical properties.

In Situ Dendrimer-Crosslinked Gel Polymer Electrolytes for Lithium-Ion Batteries with High Ionic Conductivity and Excellent Electrochemical Performance

In Situ Dendrimer-Crosslinked Gel Polymer Electrolytes for Lithium-Ion Batteries with High Ionic Conductivity and Excellent Electrochemical Performance

Facile design of novel nanocellulose-based gel polymer electrolyte for lithium-ion batteries application

Nanocellulose-based gel polymer electrolytes (GPEs) for lithium-ion batteries have attracted great attention due to their biodegradable and renewable precursors, high thermal stability, good mechanical strength and electrolyte wettability. However, their abundant hydroxyl groups lead to the precursor films of GPEs with dense morphology, which severely affect their electrolyte uptake ratio and electrochemical performance. In this work, we aim to pretreat cellulose nanofibrils (CNFs) by acetylation to not only introduce ester groups in the according GPE to improve its electrolyte absorption capacity but also reduce the amount of hydroxyl groups for a stable battery cycle performance. At the optimal degree of substitution (DS) value of 2.37, the generated acetylated CNF (GACNF-3) GPE exhibited the best electrolyte uptake capacity of 301%, ionic conductivity of 2.73 × 10−3 S cm−1, and Li+ ion transference number of 0.65. Due to the high transportation performance of Li+ ions, mechanical strength (tensile strength of 37.66 MPa), and flexibility (elongation of 10.55%), the interfacial resistance of Li/GACNF-3 GPE/Li was 152 Ω, which only increased to 170 Ω after storage for 18 days. In particular, the assembled Li/GPE/LiFePO4 battery demonstrated an initial discharge capacity of 153 mA h g−1 with capacity retention of 88.8% after 100 cycles at 0.2C. The proposed material design would provide a novel perspective for the development of polymer electrolyte for lithium-ion battery.

Toward Sustainable Solid Polymer Electrolytes for Lithium-Ion Batteries.

Lithium-ion batteries (LIBs) are the most widely used energy storage system because of their high energy density and power, robustness, and reversibility, but they typically include an electrolyte solution composed of flammable organic solvents, leading to safety risks and reliability concerns for high-energy-density batteries. A step forward in Li-ion technology is the development of solid-state batteries suitable in terms of energy density and safety for the next generation of smart, safe, and high-performance batteries. Solid-state batteries can be developed on the basis of a solid polymer electrolyte (SPE) that may rely on natural polymers in order to replace synthetic ones, thereby taking into account environmental concerns. This work provides a perspective on current state-of-the-art sustainable SPEs for lithium-ion batteries. The recent developments are presented with a focus on natural polymers and their relevant properties in the context of battery applications. In addition, the ionic conductivity values and battery performance of natural polymer-based SPEs are reported, and it is shown that sustainable SPEs can become essential components of a next generation of high-performance solid-state batteries synergistically focused on performance, sustainability, and circular economy considerations.

Polymer Electrolytes for Lithium-Ion Batteries Studied by NMR Techniques

This review is devoted to different types of novel polymer electrolytes for lithium power sources developed during the last decade. In the first part, the compositions and conductivity of various polymer electrolytes are considered. The second part contains NMR applications to the ion transport mechanism. Polymer electrolytes prevail over liquid electrolytes because of their exploitation safety and wider working temperature ranges. The gel electrolytes are mainly attractive. The systems based on polyethylene oxide, poly(vinylidene fluoride-co-hexafluoropropylene), poly(ethylene glycol) diacrylate, etc., modified by nanoparticle (TiO2, SiO2, etc.) additives and ionic liquids are considered in detail. NMR techniques such as high-resolution NMR, solid-state NMR, magic angle spinning (MAS) NMR, NMR relaxation, and pulsed-field gradient NMR applications are discussed. 1H, 7Li, and 19F NMR methods applied to polymer electrolytes are considered. Primary attention is given to the revelation of the ion transport mechanism. A nanochannel structure, compositions of ion complexes, and mobilities of cations and anions studied by NMR, quantum-chemical, and ionic conductivity methods are discussed.

Photo and thermal crosslinked poly(vinyl alcohol)-based nanofiber membrane for flexible gel polymer electrolyte

Novel dual crosslinked nanofibrous membranes (DCNMs) were fabricated by a combination of UV-photocrosslinking and thermal sol-gel crosslinking procedures and used as a matrix for gel polymer electrolytes for lithium-ion batteries (LIBs). Flexible nanofibrous membranes were obtained from the solution of poly(vinyl alcohol) (PVA), maleated PVA (PVA-MA), polyethylene glycol diacrylate (PEGDA), and tetraethyl orthosilicate (TEOS) by electrospinning technique. As a matrix for gel polymer electrolyte (GPE), it showed significantly higher ionic conductivity of 1.98 × 10−3 S cm−1 than the commercial separators and pure PVDF based GPE. Incorporation of TEOS into the membrane composition, and formation of siloxane bonds (Si–O–Si) greatly increased the conductivity providing excellent mechanical and thermal stability. The assembled lithium metal cell with LiFePO4 cathode exhibited excellent cycling performance and delivered a high reversible capacity of 133 mA h g−1 at 0.1 C and retained 87% of the initial discharge capacity after 150 cycles with a stable coulombic efficiency near 100%. The GPE could substantially suppressed the growth of Li dendrites during the stably cycles up to 1000 h, while the cell with the commercial separator failed within 800 h. In consequence, this novel DCNM possesses a potential for application in flexible and safe Li-ion and Li-metal batteries.

A comprehensive review of polymer electrolyte for lithium-ion battery

A comprehensive review of polymer electrolyte for lithium-ion battery

Bacterial cellulose reinforced polymer electrolytes for lithium-ion batteries

A sandwich-like polyethylene oxide (PEO)-based polymer electrolyte membrane with a thickness of only 60 μm is fabricated. The electrolyte is composed of a porous bacterial cellulose (BC) membrane, polymer matrix and lithium salt, fabricated by only one-step approach. The BC membrane provides strong mechanical property and physically prevents the lithium dendrite from unrestricted growth. Meanwhile, the presence of polar small molecule organics can not only increase the flexibility of polymer chain segments to enhance ion transport capacity, but also obtain a “soft contact” between the electrolyte–electrode. The BPP60% electrolyte shows enhanced electrochemical performance and LiFePO4/Li cell processes reliable charge–discharge cycle performance.

Photocured Cationic Polyoxazoline Macromonomers as Gel Polymer Electrolytes for Lithium-Ion Batteries

In this work, we present a cationic vinylimidazolium-terminated poly(2-ethyl-2-oxazoline) (PEtOx) macromonomer as a key component of gel polymer electrolytes (GPE) for lithium-ion batteries. GPE production followed a scalable process based on UV curing of the cationic PEtOx macromonomer with polyfunctional acrylic comonomers dissolved in an organic electrolyte (LP30), affording electrolyte-swollen polymeric ionic liquid (PIL) networks with PEtOx side chains. Thus, cathodes coated with a GPE layer of less than 200 μm thickness were readily manufactured. The PIL brush-type GPE is highly insoluble but swellable in LP30 and exhibits pronounced electrolyte retaining ability against evaporation. At 160 °C, the weight loss of the GPE amounted to around 5%. This is 12% less compared to an LP30-soaked commercial Celgard separator. At room temperature, the ionic conductivity was 3.6 × 10–4 S/cm, surpassing that of a comparable Celgard/LP30 system. Contrary to LP30 in Celgard, conductivity measurements for the PIL brush GPE did not indicate any crystallization of the liquid electrolyte at subambient temperatures. This was confirmed by differential scanning calorimetry, suggesting improved ionic mobility in the GPE over a wide temperature range. The electrochemical stability window of the PIL brush GPE is wide enough and fits all common lithium-ion cathode materials. In fact, the GPE exhibited exceptional oxidative stability of 5.2 V vs Li/Li+. Half-cell cycling experiments using a lithium iron phosphate cathode revealed high capacity values of 150 mAh/g at a current rate of C/10. When the current was increased to C/2, the capacity decreased to 120 mAh/g and the cell reached 80% of its initial capacity (referred to C/2) after 180 cycles. Thus, according to the first physicochemical and electrochemical investigations, the PEtOx-based PIL brush GPE represents a promising candidate with respect to lithium-ion battery operation.

Plasticized 3D-Printed Polymer Electrolytes for Lithium-Ion Batteries

In the current research, we developed and printed by fused-filament fabrication polylactide-polyethylene-oxide blended membranes. The influence of relative content of polymers on the ease of extrusion and printing processes was studied. Ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethane-sulfonyl)imide (Pyr14TFSI) with dissolved LiTFSI salt was infused into the membranes to produce free-standing films of quasi-solid polymer electrolytes. The printed membranes were characterized by ESEM, DSC, XPS, NMR and EIS methods. Neat-printed PLA (polylactide) membrane exhibited poor wetting and low uptake of ionic liquid. However, the XPS tests of 3D-printed PLA-PEO membrane infused with LiTFSI solvated ionic liquid show evidence of the interaction between lithium cations with both, PEO (polyethylene oxide) and PLA. The measurements of diffusion coefficients by PGSE-NMR suggest that the Li+ ions are coordinated by the PEO segments in the polymer blend. Increase of the PEO content at the expense of PLA polymer, leads to more than one order of magnitude improvement of bulk conductivity, approaching 0.2 mS cm−1 at 60

Electrochemical behavior of BaTiO3 embedded spongy PVDF-HFP/cellulose blend as a novel gel polymer electrolyte for lithium-ion batteries

Herein, a microporous poly(vinylidene fluoride co-hexafluoropropylene)/cellulose/ BaTiO3 membrane with a sponge-like architecture has been prepared by spinning cum immersion precipitation route followed by hydrolysis with lithium hydroxide for the deacetylation of cellulose acetate. The fabricated composite membrane-based LiFePO4|Li cell achieves a high ionic conductivity of 1.36 mS cm−1 at 30 °C. Additionally, the electrochemical system exhibits a good discharge capacity of 150.1 mAh g−1 and excellent cycling stability with a capacity retention of 95% after 200 cycles at a 0.1C rate. The transference number of the system is computed to be 0.51. According to these findings, the proposed gel polymer electrolytes have a great potential for use in lithium-ion batteries.

Solvent-Free Procedure to Prepare Ion Liquid-Immobilized Gel Polymer Electrolytes Containing Li0.33La0.56TiO3 with High Performance for Lithium-Ion Batteries.

Based on the advantages of intrinsic safety, flexibility, and good interfacial contact with electrodes, a gel polymer electrolyte (GPE) is a promising electrolyte for lithium-ion batteries, compared with the conventional liquid electrolyte. However, the unstable electrochemical performance and the liquid state in a microscale limit the commercial application of GPE. Herein, we developed a novel gel polymer electrolyte for lithium-ion batteries by blending methyl methacrylate (MMA), N-butyl-N-methyl-piperidinium (Pyr14TFSI), and lithium salts in a solvent-free procedure, with SiO2 and Li0.33La0.56TiO3 (LLTO) additives. The prepared MMA-Pyr14TFSI-3 wt % LLTO electrolyte shows the best electrochemical performance and obtains a high ion conductivity of 4.51 × 10–3 S cm–1 at a temperature of 60 °C. Notably, the electrochemical window could be stable up to 5.0 V vs Li+/Li. Moreover, the batteries with the GPE also show excellent electrochemical performance. In the LiFePO4/MMA-Pyr14TFSI-3 wt % LLTO/Li cell, a high initial discharge capacity was achieved 150 mA h g–1 at 0.5C with a Coulombic efficiency over 99% and maintaining a good capacity retention of 90.7% after 100 cycles at 0.5C under 60 °C. In addition, the physical properties of the GPE have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) measurements, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetry (TG).

Exploring the Ion Solvation Environments in Solid-State Polymer Electrolytes through Free-Energy Sampling

The success of poly(ethylene oxide) (PEO) in solid-state polymer electrolytes for lithium-ion batteries is well established. Recently, in order to understand this success and to explore possible alternatives, we studied polyacetal electrolytes to deepen the understanding of the effect of the local chemical structure on ion transport. Advanced molecular dynamics techniques using newly developed, tailored interaction potentials have helped elucidate the various coordination environments of ions in these systems. In particular, the competition between cation–anion pairing and coordination by the polymer has been explored using free-energy sampling (metadynamics). At equivalent reduced temperatures, with respect to the polymer-specific glass-transition temperature, two-dimensional free-energy plots reveal the existence of multiple coordination environments for the lithium (Li) ions in these systems and their relative stabilities. Furthermore, we observe that the Li-ion movement in PEO follows a serial, stepwise pathway when moving from one coordination state to another, whereas this happens in a more continuous and concerted fashion in a polyacetal such as poly(1,3-dioxalane) [P(EO-MO)]. The implication is that interconversion between coordination states of the Li ions may be easier in P(EO-MO). However, the overarching observation from our free-energy analysis is that Li-ion coordination is dominated by the polymer (in either case) and contact-ion pairs are rare. We rationalize the observed higher increase in glass-transition temperature (Tg) with salt loading in polyacetals as due to intermolecular Li-ion coordination involving multiple polymer chains, rather than just one chain for PEO-based electrolytes. This interchain coupling in the polyacetals, resulting in the higher Tg, works against any gains due to variations in Li-ion coordination that might enhance transport processes over PEO. Further research is required to overcome the interdependence between local coordination and macroscopic properties to compete with PEO electrolytes at the same absolute working temperature.

Nanostructured Polymer Electrolytes for Lithium-Ion Batteries

Nanostructured Polymer Electrolytes for Lithium-Ion Batteries