Solid Polymer Electrolyte Research Articles

Contributing to the Revolution of Electrolyte Systems via In Situ Polymerization at Different Scales: A Review.

Solid-state batteries have become the most anticipated option for compatibility with high-energy density and safety. In situ polymerization, a novel strategy for the construction of solid-state systems, has extended its application from solid polymer electrolyte systems to other solid-state systems. This review summarizes the application of in situ polymerization strategies in solid-state batteries, which covers the construction of polymer, the formation of the electrolyte system, and the design of the full cell. For the polymer skeleton, multiple components and structures are being chosen. In the construction of solid polymer electrolyte systems, the choice of initiator for in situ polymerization is the focus of this review. New initiators, represented by lithium salts and additives, are the preferred choice because of their ability to play more diverse roles, while the coordination with other components can also improve the electrical properties of the system and introduce functionalities. In the construction of entire solid-state battery systems, the application of in situ polymerization to structure construction, interface construction, and the use of separators with multiplex functions has brought more possibilities for the development of various solid-state systems and even the perpetuation of liquid electrolytes.

Tunable Conformal Electrodeposition of Ultra-Thin Polymeric Films for Electrolyte Interphases

Functional coatings and interphases influence the stability and performance parameters of electrodes in various applications. Polymer thin films offer a wide range of molecular structures and compositions for tunable functionalities that can be custom designed to the needs of an application. In solid-state energy storage devices in particular, electrolyte-type polymeric interfaces between battery components and materials with disparate functions, such as the active electrode material and solid electrolyte could overcome some of these incompatibility detriments and the increase in contact resistance over long-term operation. In high-performance micro scale power sources, 3D thin-film all-solid-state batteries show great potential as they take advantage of both short ion diffusion distances for high-rate capability with low heat generation, as well as the third dimension for high material loading and energy density. Therefore, conformal deposition methods for ultra-thin polymeric electrolyte interphases on the interior surface of electrodes with mesoscale 3D architectures and complex porosity are in demand. Here, we report a molecular design concept of dual-functional molecules that contain electrochemically active end groups for self-limiting electropolymerization, and a core molecular motif that determines the thin film functionality. The electrodeposition of this monomer represents a non-line-of-sight coating method for polymer thin films with independently tailorable functionalities and tunable properties on conductive substrates with arbitrary shape. We exemplify this method using monomers with poly(ethylene glycol) (PEG) as the core motif for lithium-ion transport and phenol as electrochemically active end groups. We studied the electrodeposition of the monomers, poly(ethylene glycol) diphenol (PEGDP), and demonstrate their self-limiting film formation mechanism (Figure 1a) which originates from the insulating nature of resulting poly(PEGDP) film that confines the charge transfer reaction. We present an exhaustive exploration of their material-processing-structure-property relationships that reveals the multi-scale control over the ultrathin-film properties. For example, the uniform film thickness is tunable from 10 to 100s of nanometer through electrodeposition conditions and molecular design, while their molecular permeability and electronic resistance can be tailored from pervious to fully blocking. We show that the electrodeposited functional interphases fully coat complex 3D electrode architectures (Figure 1b top: uncoated carbon electrode, bottom: film coated carbon electrode) with retention of their functionality in a battery. This work demonstrates that rational molecular design enables the conformal electrodeposition of ultrathin functional coatings with solid polymer electrolyte properties on 3D structured electrodes that will enable designer interphases in various solid-state battery architectures and chemistries. Figure 1

Nanocomposite Solid Polymer Electrolytes with Polymer Blend (PVDF‐HFP/Pluronic) as Matrix and GO as Nanofiller: Preparation, Structural Characterization, and Lithium‐Ion Conductivity Analysis

AbstractNanocomposite solid polymer electrolytes (NSPEs) with PVDF‐HFP/Pluronic as blend polymer matrix, graphene oxide (GO) as nanofiller, and LiClO4 are reported. FTIR spectroscopy reveals the crystal phase transformation of PVDF‐HFP from nonpolar α phase to electroactive γ phase upon salt addition that suggests the ion‐dipole interaction between the salt and the matrix. Further, Pluronic not only hinders the PVDF crystallization that increases the amorphous character of the matrix but also interacts with the salt and hence assists in salt dissociation in the blend matrix. The dc conductivity of PVDF‐HFP/Pluronic/LiClO4 blend SPE improves with increasing the Pluronic content reaching 0.73 × 10−6 Scm−1 at room temperature with 60 wt.% Pluronic. The dispersion of GO in the same blend SPE leads to a significant jump in room temperature ion conductivity (≈1.2 × 10−6 Scm−1) with 0.4% GO. Temperature‐dependent ion conductivity of the NSPEs reveals an Arrhenius type thermally activated process. The dc polarization data indicates that the conductivity is predominantly due to ions. Impedance plots exhibit a distorted semicircle at higher frequency and a tilted spike at lower frequency. The spike is an indication of ion diffusion and electrode polarization effect. Further, GO also has enhanced the mechanical properties of the fabricated NSPEs.

Synthesis and properties of polymer electrolytes based on polyurethane elastomer and lithium salts

Polymer solid electrolytes were obtained by swelling the polyurethane elastomer with solutions of lithium salts LiBF4 and LiClO4 in DMSO at different concentration of lithium salt. The swelling effect was found to decrease with the increase in the salt concentration, whereas, the ionic conductivity has a maximum of 6–8·10–4 S/cm at 5 wt.% lithium salt. The salt solutions incorporated into the polymer pores have melting points ranging from –10 to 2 °C and de-swelling takes place at low temperatures. The obtained polyurethane elastomer materials have a high conductivity and may be promising for use in flexible lithium polymer batteries.

Effects of Lithium Metal Storage Environment on Its Reactivity toward Polyethylene Oxide-Based Blend Electrolytes.

Lithium metal has generated significant interest as an anode material because of its high theoretical capacity. However, issues such as dendrite growth and lithium loss during cycling make this material incompatible with liquid electrolytes. Solid polymer electrolytes (SPE) have been proposed as replacements as they are non-flammable, resist dendrite growth, have decent ionic conductivity, and have low resistance with lithium metal. Passivation layers, which form on the lithium metal surface and are hence intrinsic to its chemical composition, are often overlooked. Residual quantities of atmospheric gases are present in lithium metal storage environments, making surface modification and its subsequent impact on anode reactivity inevitable. Moreover, the impact of this phenomenon in a realistic lithium metal anode (LMA) environment with SPE has not yet been extensively investigated. In this study, the impact of gas exposure on an LMA was investigated by exposing freshly cut lithium rods to O2, CO2, and N2. Passivation layers were characterized via X-ray photoelectron spectroscopy. The effect of passivation layer formation on LMA reactivity toward SPE was measured by exposing passivated samples to common SPE materials. The resultant interface was characterized using Raman spectroscopy. SPE-passivation layer reactivity was correlated to ageing by electrochemical impedance spectroscopy and kinetic charge transfer via galvanostatic linear polarization at the LMA-SPE interface in symmetric Li─SPE─Li stacks. This study revealed that the chemical composition of the passivation layer affects LMA reactivity toward SPE and electrochemical performance. A thorough characterization of the lithium metal passivation layer is essential to understanding the fundamental factors affecting solid-state lithium metal battery performance.

Crosslinked Hyperbranched Polyglycerol-Based Polymer Electrolytes for Lithium Metal Batteries

Tailored partially methylated and methacrylated hyperbranched polyglycerols (hbPG-MAx/OMey) combined with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as conducting salt were investigated after crosslinking with respect to their application as solid polymer electrolytes (SPE) in lithium metal batteries. For sample preparation and coating, a straightforward solvent-free photopolymerization method was applied. With the aim of finding the right balance between mechanical and electrochemical properties, electrolytes with different crosslinking densities were studied. High crosslink density increases mechanical integrity but reduces local chain motion and thus ionic conductivity at the same time. Differential scanning calorimetry (DSC), chronoamperometric and impedance measurements show that the hyperbranched polyether structure interacts strongly with lithium cations. Finally, the SPE with the lowest crosslinking density was selected and investigated in cycling tests due to the parameters of highest absolute values in conductivity (2.1 × 10−6 S cm−1 at 30 °C; 2.0 × 10−5 S cm−1 at 60 °C), lowest Tg (from DSC: −39 °C), electrochemical stability window (4.3 V vs. Li/Li+) and mechanical strength (1.6 ± 0.4 MPa at 25 °C). At low C-rates and elevated temperatures (60 °C), cells were cycled with high Coulombic efficiency. At high C-rates, a distinct decrease in specific capacity was observed due to insufficient ionic conductivity.

Finite elastic-viscoplastic deformation behaviour of PEO-based solid polymer electrolyte: Experimental investigation and constitutive modelling

Polyethene oxide (PEO) has emerged as a preferred candidate for solid electrolytes due to its excellent solubility towards lithium salts, stable chemical properties, high flexibility, and low cost. However, the poor knowledge of the mechanical behaviours of PEO electrolytes leads to the road facing vast challenges in developing all-solid-state lithium batteries. In this study, we conducted the uniaxial tensile tests on PEO-LiTFSI films at 20–40 °C, and the strain rate ranges from 0.001 s−1 to 0.01 s−1 while investigating the potential effect mechanisms. Based on a rheological scheme of semi-crystalline polymers, we developed a new constitutive model for simulating the stress-strain curves of PEO-based electrolytes. The results indicate that PEO-LiTFSI exhibits the finite viscoelastic-plastic deformation characteristic with a minimal elastic strain range, low elastic modulus and yield strength. Increasing LiTFSI content and temperature can reduce the crystallinity of the PEO, resulting in significant softening of the polymer electrolyte; the opposite is true with raising the strain rate. Notably, the present model can capture the mechanical response of PEO electrolytes across a range of temperatures and strain rates, and the predicted tensile curves align closely with the experimental results. In addition, the simulation reveals that subpar mechanical performance would occur for PEO-LiTFSI under the recommended electrochemical operation conditions (0.05–5 C and 50 °C).

Glucose-derived carbon dots as nanofillers for improved ionic conductivity in polyvinyl alcohol–based solid polymer electrolyte membranes

Glucose-derived carbon dots as nanofillers for improved ionic conductivity in polyvinyl alcohol–based solid polymer electrolyte membranes

Graphyne-based membrane as a promising candidate for Li-Battery electrodes protection: Insight from atomistic simulations

All-solid electrolytes could lead to a technological breakthrough in the performance of all-solid-state batteries when combined with a lithium-metal anode. However, the use of a lithium-metal anode presents several challenges, such as dendrite growth, interface electrochemical stability, formation and propagation of cracks, and delamination of the electrode/electrolyte interfaces. This work aims to explore the effectiveness of using newly synthesized 2D graphyne-based membranes (namely graphyne, graphdiyne, and graphtriyne) for electrode protection in a solid polymer electrolyte battery through first-principle calculations, nudged elastic band method, and classical molecular dynamics simulation. Specifically, we aim to investigate the effectiveness of these membranes in mitigating the aforementioned challenges. A high external electric field of up to 0.5 V/Å, 0.75 V/Å, and 1 V/Å was applied to accelerate the ions diffusion process. The adsorption energies, charge transfer, and in-plane/out-plane diffusion of single lithium on graphyne-based surfaces were investigated. Afterward, we calculated and compared the Li+ permeability, the electrolyte molecules’ rejection efficiency, and the intrinsic properties of graphyne-based nanoporous membranes. Our findings show that both graphyne and graphdiyne surfaces effectively permit Li+ intercalation while preventing other electrolyte molecules from reaching the electrodes.

Structural and Spectroscopic Investigation on Plasticized PEO/PMMA Blended Nanocomposite Solid Polymer Electrolytes

Structural and Spectroscopic Investigation on Plasticized PEO/PMMA Blended Nanocomposite Solid Polymer Electrolytes

Development of Na+ ion conducting solid biopolymer electrolytes based on Na-CMC-SPA hydrogel

Solid polymer electrolytes based on biopolymers are green and environment-friendly materials. Here, solid biopolymer electrolyte (SBPE) hydrogel based on carboxymethyl cellulose is introduced for Na+ ion-based energy storage material. The synthesized SBPE material is biodegradable and shows excellent strength with good flexibility and high elasticity. SBPE-2 has compact packing with inner porous morphology which is helpful in ionic conduction inside the matrix. The ionic conductivity of electrolyte material was recorded in the range of 10-5 S/cm at room temperature and 10-4 S/cm at higher temperatures (>40 °C). The ionic transference number is found to be > 96% in 510 sec. LSV measurements confirm that the SBPEs material can be used in device fabrication up to 2.3 V. These properties of electrolytes make them a promising material for application in energy storage devices.

AlTiMgLiO medium entropy oxide additive for PEO-based solid polymer electrolytes in lithium ion batteries

Solid polymer electrolytes (SPE) have attracted considerable attention as electrolytes for solid-state batteries due to their toughness, high safety, and ionic conductivities that can be comparable with liquid electrolytes, especially at higher temperatures. However, polymers have low elastic moduli, which decrease at higher temperatures, limiting their ability to reduce dendrite formation. Mechanical blocking is one method of improving the interfacial layer and reducing dendritic growth but requires the elastic modulus of the polymer to be high enough to suppress lithium dendrites growth. Previous studies have focused on using unary metal oxides, which are limited by the percent of additives that can be included in the polymer before causing negative effects on electrochemical properties. In this study, we demonstrate a new strategy for improving the performance of polymers by synthesizing a multielement oxide (MEO) filler, AlTiMgLiO, to create a composite SPE with enhanced electrochemical performance. The synthesized AlTiMgLiO-containing SPE resulted in a voltage window of 0–6.18 V and a lithium transference number of 0.42. The overpotential voltage during galvanostatic cycling was reduced due to the improvements made to the morphology. The improvement of the interfacial layer reduced Li dendritic growth, resulting in a capacity of 99.68 mAh g−1 after 500 cycles, and a capacity retention of 78.69 %. The possible reasons for the improvement are discussed, providing a direction for future studies on the use of multielement materials as fillers in solid polymers electrolytes.

The Promise of 3D Printed Solid Polymer Electrolytes for Developing Sustainable Batteries: A Techno-Commercial Perspective

The Promise of 3D Printed Solid Polymer Electrolytes for Developing Sustainable Batteries: A Techno-Commercial Perspective

Solid–Polymer–Electrolyte Electrolysis of Urea Aqueous Solutions for Hydrogen Synthesis

Solid–Polymer–Electrolyte Electrolysis of Urea Aqueous Solutions for Hydrogen Synthesis

Preparation and characterization of shrimp shell waste derived carboxymethyl chitosan solid polymer electrolyte membrane

Preparation and characterization of shrimp shell waste derived carboxymethyl chitosan solid polymer electrolyte membrane

Perspective on the mechanism of mass transport-induced (tip-growing) Li dendrite formation by comparing conventional liquid organic solvent with solid polymer-based electrolytes

A major challenge of Li metal electrodes is the growth of high surface area lithium during Li deposition with a variety of possible shapes and growing mechanisms. They are reactive and lead to active lithium losses, electrolyte depletion and safety concerns due to a potential risk of short-circuits and thermal runaway. This work focuses on the mechanism of tip-growing Li dendrite as a particular high surface area lithium morphology. Its formation mechanism is well-known and is triggered during concentration polarization, i.e. during mass (Li+) transport limitations, which has been thoroughly investigated in literature with liquid electrolytes. This work aims to give a stimulating perspective on this formation mechanism by considering solid polymer electrolytes. The in-here shown absence of the characteristic “voltage noise” immediately after complete concentration polarization, being an indicator for tip-growing dendritic growth, rules out the occurrence of the particular tip-growing morphology for solid polymer electrolytes under the specific electrochemical conditions. The generally poorer kinetics of solid polymer electrolytes compared to liquid electrolytes imply lower limiting currents, i.e. lower currents to realize complete concen­tration polarization. Hence, this longer-lasting Li-deposition times in solid polymer electro­lytes are assumed to prevent tip-growing mechanism via timely enabling solid electrolyte interphase formation on fresh Li deposits, while, as stated in previous literature, in liquid electrolytes, Li dendrite tip-growth process is faster than solid electrolyte interphase forma­tion kinetics. It can be reasonably concluded that tip-growing Li dendrites are in general practically unlikely for both, (i) the lower conducting electrolytes like solid polymer electro­lytes due to enabling solid electrolyte interphase formation and (ii) good-conducting electro­lytes like liquids due to an impractically high current required for concentration polarization.

Impact of EC-plasticizer on electrical and dielectrical properties of PEO/PVdF/NaNO3 solid polymer electrolyte systems

Impact of EC-plasticizer on electrical and dielectrical properties of PEO/PVdF/NaNO3 solid polymer electrolyte systems

Water as dispersion medium to fabricate homogeneous nano-hectorite solid-state electrolyte for suppressing lithium dendrite

The rational design of green chemical, low-cost, and highly efficient solid-state electrolytes for Li-metal anode is a promising but still challenging strategy for preventing Li dendrite growth and developing safe and ultralong cycle life Li-metal batteries. Herein, a homogeneous composite solid polymer electrolyte (CSPE) is fabricated with water as the ideal dispersion medium, hectorite (Ht) as nanofiller, and poly (ethylene oxide) (PEO) as the matrix, to guide uniform Li plating/stripping. Benefiting from the merit of Ht can form uniformly dispersed nanosheets in water, the obtained CSPE inheres to a low melting point, robust mechanical property, and high Li+ transference number. Moreover, the fabricated Li symmetric battery using PEO-Ht-LiClO4 CSPE keeps cycling steadily for 4 000 h. The well demonstrated water-based CSPE paves the way for developing low-cost, environmentally friendly, and safe solid-state electrolytes for Li-metal batteries.

Dielectric relaxation and ionic conduction in solid polymer electrolyte based on a random copolymer of ethylene carbonate and ethylene oxide

Broadband dielectric spectroscopy (BDS) is a powerful technique for studying the dielectric and ion-conductive behavior of solid polymer electrolytes (SPE). In this study a random copolymer of ethylene carbonate (EC) and ethylene oxide (EO), P(EC/EO), was used as a polymer host for SPE, and the correlation between dielectric relaxation and ionic conduction in P(EC/EO)-LiFSI electrolytes was studied. BDS measurements revealed that the DC conductivity for P(EC/EO) electrolytes is higher than for the PEC system at all salt concentrations. This is due to the much higher a-relaxation frequency, indicating that the randomly introduced EO units can provide fast segmental motion with no formation of any stable coordination structures with Li ions. FT-IR analysis indicated that the peak fraction of C = O interacting with Li ions was small, less than 10% in the 10 mol% electrolyte, but in concentrations above 40 mol% the proportion was nearly saturated at around 60–70%. A small CO-C peak interacting with Li ions appears at 1080 cm−1, but no change in peak intensity is observed, implying no formation of stable coordination structures that reduce the glass transition temperature.

Robust ion-rectifying polymer electrolyte membrane for high-rate solid-state lithium metal batteries

The uncontrolled dendrite growth and poor rate performance originating from crystallization-induced anisotropic ion transport and insufficient mechanical strength of solid polymer electrolytes (SPE) have significantly impeded the practical application of high-rate solid-state lithium metal batteries. Herein, we present a robust ion-rectifying PEO-based SPE membrane by incorporating titanium-oxo clusters (TOC) composed of a diameter of 2.69 nm and a height of 1.04 nm rigid backbone and hairy PEG chains into PEO-LiN(CF3SO2)2 (LiTFSI) electrolyte, denoted as PEO-TOC membrane. This membrane realizes dendrite-free lithium metal deposition where TOC serves as a rhecology-tuning (by reducing crystallinity) and anion-trapping (through Lewis acid-base interactions) agent, thus achieving an ion-rectifying effect in the electrolyte membrane. Consequently, the rapid and homogeneous Li+ flux is achieved, resulting in a high ionic conductivity of 5.5 × 10−5 S cm−1 at 30 °C and Li+ transference number of 0.51. Furthermore, the rigid backbone enables a robust compressive strength of 940 MPa for dendrite suppression. As a result, the robust ion-rectifying PEO-TOC membrane endows the Li-LFP cells with high-rate performance, achieving 111.9 mAh g−1 at 3.5 C, and good cycling performance of 92.9% capacity retention over 250 cycles at 1 C, which routine SPE hardly fulfills with anisotropic Li+ flux and mechanical properties.