Single Lithium-ion Conducting Polymer Electrolytes Research Articles

The role of nanoceramic additives surface charge on the ionic transport of single lithium-ion conducting polymer electrolytes

The role of nanoceramic additives surface charge on the ionic transport of single lithium-ion conducting polymer electrolytes

Chain length dependence of structural and transport properties of single lithium-ion conducting polymer electrolytes: A molecular dynamics simulation study

In this work, the parameters affecting the performance of polymer electrolytes, for utilization in lithium-ion batteries (LiBs) are investigated. For this purpose, by using density functional theory (DFT) and molecular dynamics (MD) simulation, the structural and transport properties of single lithium-ion conducting polymer electrolytes (SLICPEs) based on boron ethylene glycol (BEG), as the anion, with the molecular structure ofBO3−−C2H4On−BO4− are evaluated. The calculated structural properties, include density, glass transition temperature, and radial distribution function (RDF). The simulated transport properties are diffusion coefficient, transference number, and ionic conductivity. In the first step, the optimization of molecular structures is obtained by DFT calculations with B3LYP functional approximation and Mullikan partial charges for the polymer chain lengths of 1, 4, 8, and 15 monomers. Then, by using MD simulations and an ten-stages compression-expansion procedure, the studied electrolyte systems are equilibrated. The results indicate that the transference numbers of these electrolytes are significantly higher than those of commonly used electrolytes based on polyethylene oxide (PEO). Inspection of the obtained results indicates that the diffusion and ionic conductivity coefficients are influenced by the interaction of Li+ with oxygen atoms in the polymer chain. Analysis of the transport properties of Li+ along the polymer chain structure reveals that the presence of a boron atom in the polymer chain backbone induces a significant non–uniform charge distribution along the polymer chain and as a result weakens the interaction between Li+ with an oxygen atom in the polymer chain. Therefore compared to the conventional electrolytes, Li+ can move more freely along the polymer chain, and as a result, the performance of LiBs is promoted significantly.

Nanoscale Ionic Materials for Nafion Based Nanocomposites Membranes As Single Lithium-Ion Conducting Polymer Electrolytes for Lithium Sulfur Batteries

Currently, rechargeable batteries with the lithium–sulfur (Li–S) chemistry has attracted great interest as one of the most promising candidates for next generation electrochemical energy storage systems. Research into these high energy density devices is critical to the development of thinner, lighter, and lower cost battery systems. One of the biggest obstacles for practical applications of Li-S batteries is caused by the soluble nature of the highly ordered lithium polysulfides (Li2Sn) in the organic electrolytes and induce a so-called “shuttle effect”. A solid-state electrolyte (SPEs) could be a valid alternative in terms of reducing the polysulfides dissolution and shuttle, as well as to protect the lithium metal anode and to minimize dendrite formation, which is beneficial for improving the safety and cycle life of Li−S batteries. SPEs are typically dual-ion conductor systems both cations and anions are mobile and cause a concentration polarization leading to poor performances of batteries. Recently, single lithium-ion conducting solid polymer electrolytes (SLIC-SPEs) have been proposed for polymer electrolytes, where anions are covalently bonded to the polymer, inorganic backbone, or immobilized by anion acceptors and only the Li+ cation will contribute to a permanent flow of charge. They have advantages over conventional dual-ion conducting SPEs such as unity transference number, absence of harmful effect of anion polarization, extremely low rate of Li dendrite growth and immobilization of the lithium polysulfides in the lithium-sulfur (Li-S) batteries. Polymer electrolytes based on ionomers (e.g., Nafion) with easily ionizable groups (e.g., sulfonic groups covalently bonded to the polymer side-chains, −CF2SO3 −) are promising thanks to the high concentration of weakly coordinating anions (counterions). In this work, lithiated Nafion and Nafion-nanocomposites membranes based on Nanoscale Ionic Materials (NIMs) were synthesized, and their ionic conductivity and lithium transference number were investigated in common nonaqueous organic solvents (EC/PC and Glymes).A thorough and systematic study of the lithium-ion transport was conducted by p 1H and 7Li pulsed field gradient (PFG) NMR spectroscopy and electrochemical impedance spectroscopy (EIS), while the mechanical properties of the film electrolytes have been tested by dynamic mechanical analysis (DMA) in a wide temperature range. The electrochemical studies have been conducted both in Li/Li symmetric cell and in secondary Li-S cells. The preliminary results are very interesting, showing ionic conductivities of the order of 5 × 10-4 S/ cm at 25°C satisfactory properties in terms of stability window and stability of the lithium stripping. The lithium transport number is very close to unity thus confirming the complete immobilization of the negative charge carriers.

Fire-retardant sp3 boron-based single ion conducting polymer electrolyte for safe, high efficiency and dendrite-free Li-metal batteries

Single lithium ion conducting polymer electrolytes (SIPEs) are an emerging class of alternative polymer electrolytes for protecting lithium metal anode. This work explores a fully aromatic sp3 boron based SIPE, lithium poly (4,4′-dihydroxydiphenyl sulfone borate), Li-PSB, via a one-step synthetic procedure. A series of highly porous SIPE membranes, defined as po-PBSBs, comprising of Li-PSB and a fully aromatic polybenzimidazole (PBI) binder are firstly prepared. As a polymer electrolyte, po-PBSB exhibits high lithium ion transference number of close to unity, high ionic conductivity, excellent thermal dimensional stability and promising flame-retardant. X-ray Photoelectron Spectroscopy (XPS) and Density Functional Theory (DFT) calculations depict multi-coordinated lithium ion transport channels in the po-PBSB membranes. By serving as polymer electrolyte in lithium metal batteries (LMBs), Li/LiFePO4 (LFP) cell, the po-PBSB shows an effective suppression of lithium dendrite growth. As a consequence, po-PBSB based Li/LFP cell demonstrates superior cycling performance remaining 76.1% of its initial capacity with nearly 100% coulombic efficiency at 1.0C after 200 cycles. The excellent performance may be ascribed to the remarkable lithium ion transference number, high organic solvent absorption in pores and thermal and electrochemical stabilities of the po-PBSB. We believe that the novel SIPE materials have great potential for application in high-safety LMBs.

A Novel Li+-Nafion-Sulfonated Graphene Oxide Membrane as Single Lithium-Ion Conducting Polymer Electrolyte for Lithium Batteries

Single lithium-ion conducting polymer electrolytes are an innovative concept of solid-state polymer electrolytes (SPEs) for lithium-battery technology. In this work, a lithiated Nafion nanocomposit...

Charge Delocalization on BO4– Centers to Improve Conductivity on Single Lithium Ion Conducting Polymer Electrolytes: A Computational/Experimental Approach

Single lithium ion conducting polymer electrolytes (SLICPEs) could be one of the best options for safer lithium ion batteries, only if new strategies can be envisaged to improve their ionic conduct...

Synthesis of Single Lithium-Ion Conducting Polymer Electrolyte Membrane for Solid-State Lithium Metal Batteries

Synthesis of single lithium-ion conducting polymer electrolyte membrane (SLIC-PEM) composed of polymerized lithium 4-styrenesulfonyl(trifluoromethylsulfonyl)imide (PLiSTFSI), poly(ethylene glycol) methyl ether methacrylate (PEGM), poly(ethylene glycol) dimethacrylate (PEGDMA), and ethylene carbonate (EC) is reported. SLIC-PEM combines the advantages of single lithium-ion conducting polymer electrolytes, cross-linked flexible polymer electrolytes, and the liquid electrolyte of carbonate. The synthesized SLIC-PEMs have superior thermostability, high ionic conductivity, a wide electrochemical window, and high lithium-ion transference number. The corresponding LiFePO4|SLIC-PEM|Li cell delivers high Coulombic efficiency and excellent discharge capacity and cycling performance, demonstrating that SLIC-PEMs will have promising application in next-generation safe lithium metal batteries.

Electrochemical Characterization of Single Lithium-Ion Conducting Polymer Electrolytes Based on sp3 Boron and Poly(ethylene glycol) Bridges

A novel series of single lithium-ion conducting polymer electrolytes (SLICPE) based on sp3 boron and poly(ethylene glycol) (PEG) bridges is presented, in the context of the development of a new generation of batteries, with the aim to overcome the problems related to concentration overpotential and low ion transport numbers in conventional solid polymer electrolytes (SPE). The phase separation generated by the physical mixture of SPE with plasticizers such as poly(ethylene oxide) is still a serious problem. In this work, the use of PEG with different chain lengths, for the polycondensation reaction with LiB(OCH3)4, to synthesize SLICPE allows preventing phase separation while tuning the predominant conduction mechanism, and thus the electrical properties, especially the lithium-ion transference number. The ionic transport is promoted by chain mobility as the chain length is increased. SLICPE with the best ionic conductivity values (4.95 ± 0.05) × 10-6 S cm-1 was the one synthesized from poly(ethylene glycol) with an average MN of 400 (BEG8), having an O/Li+ ratio of 20. The lithium transference number ( tLi+) and electrochemical stability window of SLICPE membranes at 25 °C decreased as the PEG bridge length between sp3 boron atoms increased from 0.97 to 0.88 and 5.4 to 4.2 V vs Li0/Li+, respectively, for SLICPE synthesized from PEG with an average MN of 50-400 (BEG1 to BEG8).

Impact of the functional group in the polyanion of single lithium-ion conducting polymer electrolytes on the stability of lithium metal electrodes

The functional group in the polyanion plays a key role in improving the interfacial stability of the Li metal electrode.

Single lithium-ion conducting polymer electrolytes based on poly[(4-styrenesulfonyl)(trifluoromethanesulfonyl)imide] anions

New single lithium-ion conducting polymer electrolytes are prepared by a copolymerization of the two monomers, lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI) and methoxy-polyethylene glycol acrylate (MPEGA, CH2CHCO2(CH2CH2O)nCH3, n=8) in various monomer ratios. The structures and compositions of the prepared lithium poly[(4-styrenesulfonyl)(trifluoromethanesulfonyl)imide-co-methoxy-polyethylene glycol acrylate] (Li[PSTFSI-co-MPEGA]) copolymers are characterized by 1H and 19F NMR, and gel permeation chromatography (GPC). For comparison, the corresponding blended polymer electrolytes comprising lithium poly[(4-styrenesulfonyl) (trifluoromethanesulfonyl)imide] (LiPSTFSI) and poly(ethylene oxide) (PEO) are also prepared and characterized. The fundamental properties of these two types of lithium-ion conducting polymer electrolytes are comparatively studied, in terms of phase transitions, thermal stability, XRD, ionic conductivities, lithium-ion transference numbers (tLi+), and electrochemical stabilities. Both types of the polymer electrolytes are thermally stable up to 300°C. While both types of polymer electrolytes exhibit single lithium-ion conducting behavior with tLi+>0.9, the solid-state ionic conductivities of the Li[PSTFSI-co-MPEGA] copolymer electrolytes are all higher by 1–3 orders in magnitude than those of the blended ones, irrespective of the concentration of lithium ions. The highest ionic conductivities for the copolymer electrolytes are 7.6×10−6Scm−1 at 25°C and reach 10−4Scm−1 at 60°C, which are obtained at the ethylene oxide (EO) unit/Li+ ratio of 20.5.