Flexible Solid Polymer Electrolytes Research Articles

Facile Strategy to Prepare Poly(ionic liquid)-Coated Solid Polymer Electrolytes through Layer-by-Layer Assembly.

The inability of solid polymer electrolytes to preserve strong mechanical strength with high ionic conductivity hinders the commercialization of lithium metal batteries (LMBs). The success of fabricating layer-by-layer (LbL)-assembled electrolytes has realized the application of flexible solid polymer electrolytes in electrochemical devices. Here, we demonstrate a rational strategy to construct solid electrolytes coated with multiple ultrathin layers of polyanions (poly(sodium 4-styrenesulfonate)) and polycations (linear poly(1-butyl-3-(4-vinylbenzyl)-1H-imidazolium chloride) (BVIC)/linear poly(PEG4-VIC)/SiO2-g-poly(PEG4-VIC)) using an LbL assembly method. Poly(ionic liquid) backbones and PEG side groups are employed to facilitate the transport of lithium ions via the segmental motion of the macromolecular matrix. The fabricated free-standing membranes exhibited good ionic conductivities of 9.03-10 × 10-4 S cm-1. Furthermore, a Li/LiFePO4 cell assembled with the LbL-membrane electrolytes exhibits an initial high discharge capacity of 143-158 mAhg-1 at 60 °C with high columbic efficiency. This approach, which combines polymer synthesis and LbL self-assembly, is an effective and facile route to fabricate solid polymer electrolyte membranes with superior ionic conductivity and mechanical robustness, which are useful for electrochemical devices and high-voltage battery applications.

Investigation of flexible electrochemical storage with Li+/PVdF-HFP/PEO blend

ABSTRACT Design and development of lithium ion batteries with flexible solid polymer electrolyte along with high ionic conductivity is crucial and challenging so as to protect from electrical short circuits within electrochemical devices. The present research work describes the fabrication of lithium based solid polymer electrolytes (LSPEs) using polymer blends of poly (vinylidene fluoride- hexafluoropropylene) (PVdF-HFP), poly (ethylene oxide) (PEO) with selective weight ratios of lithium trifluoromethanesulfonate (LiCF3SO3) salt by using solution-cast approach. The scanning electron microscopy (SEM) exposed morphology of LSPE membranes depicts crosslinking of polymer network with salt elevates strong dissociation behavior of LiCF3SO3. The amorphous behavior of LSPEs explored using X-ray diffraction (XRD) crystallographs clearly accommodates reduction of average crystallite size from 10─6 m to 10─9 m. The complexation studies, bond length and force constants calculations, interaction of ions, ionic pairs and aggregates of LiCF3SO3 in LSPE films were briefly analyzed using Fourier transform infrared spectroscopy (FTIR). IR modes correspond to [δs (SO3)], [υas (SO3)], [υas (CF3)], and amorphous phase of PVdF-HFP results in complexation, whereas IR modes correspond to [δas (SO3)], [δs (CF3)], [δas (CF3)], [υs (SO3)], C=O and β-phase of PVdF-HFP attributes ionic pairs and aggregation phenomena. The [υs (SO3)] mode contribution toward ionic conductivity was detailed. The ionic conductivity (σionic) values were estimated using Electrochemical impedance spectroscopy (EIS). The σionic values were enhanced from 10─7 S/cm to 10─4 S/cm as salt concentration increases. Charge accumulation, ionic strength, and transference number analysis of LSPE membranes were investigated using Chronoamperometry and Cyclic Voltammetry. Further, we have fabricated flexible electrochemical storage device (FESD) which are accentuating carriers of smart electronics technology (SET) in terms of foldable and stretchable electronic devices. We have explored discharge characteristics of our FESD with an average discharge current of 3 mA for 25 hours and denoted using 0.04C rating.

A Flexible Solid Polymer Electrolyte based Polymerized Ionic Liquid for High Performance Solid‐State Batteries

AbstractSolid polymer electrolytes (SPEs) combine the benefits of ceramic electrolyte and polymer electrolyte, and have broad application prospects in high‐energy lithium metal batteries. However, low Li+ conductivity and tensile strength are crucial elements that hinder the application of solid polymer electrolytes. In this paper, an effective solid polymer electrolyte was proposed to solve these problems. A polymerized ionic liquid (PIL) was chosen as the ionic transport material to synthesize three‐dimensional cross‐linked ion channels through thermal polymerization, which can effectively improve the ionic conductivity. This work is different from some other reports that add ionic liquid without C=C double bond. We used the vinyl ionic liquid (IL) as matrix via polymerization with azobis initiator (AIBN) and the obtained co‐polymer has excellent flexibility and non‐flowing character. Li6.4La3Zr1.4Ta0.6O12 (LLZTO) ceramic filler was added to enhance the thermal stability and tensile strength of the electrolyte. Meanwhile, solid‐state batteries (SSBs) assembled with LiFePO4 cathode and high‐voltage LiNi0.8Co0.1Mn0.1O2 cathode can deliver remarkable cell performance. This work presents an appropriate device for the structure of modern polymerized ionic liquid solid polymer electrolytes, and shows significant implication for the progress of high‐property polymer electrolytes.

PolySchiff based self-healing solid-state electrolytes for lithium ion battery

Vitrimers are novel polymeric materials consisting of dynamic covalent networks that can change their topology in response to external stimuli. Here, we reported flexible solid polymer electrolyte (SPE) with room temperature self-healing properties based on imine dynamic network. The effect of cross-linking degree, the content of succinonitrile (SN) plasticizer and lithium salt on the lithium ion conductivity (σ) was carefully studied. With the addition of the lithium salt, the Tg of pure polyschiff film is apparently enhanced and the vitrimers electrolyte with lower cross-linking degree show a lower Tg. The σ shows an obviously increasing trend with the dropping cross-linking degree and higher SN content, and it reach a maximum value of 6.43 × 10−4 S/cm at 30 wt % LiTFSI at 60 °C. Importantly, the cutted vitrimers electrolyte show 74 % recovery of its original tensile strength after self-healing at room temperature. Furthermore, the electrochemical window was widened with SN addition, up to 5.1 V vs. Li/Li+. The fabricated Li||PSFSPE@0.5SN||LiFePO4 cell also demonstrates a 100mAh/g discharge capacity at 0.05C after 50th cycles, showing its possible application of imine-based polymer electrolyte. Importantly, the SPEs membranes with imine bonds can heal damages outside or inside a battery without deterioration of discharging capacity of lithium ion battery.

A flexible solid polymer electrolyte enabled with lithiated zeolite for high performance lithium battery

A flexible solid polymer electrolyte enabled with lithiated zeolite for high performance lithium battery

Li+ affinity ultra-thin solid polymer electrolyte for advanced all-solid-state lithium-ion battery

The chasing for all-solid-state lithium-ion batteries (ASSLIBs) is based on the need for safer and higher energy density batteries. In this regard, solid polymer electrolytes (SPEs) are well-renowned for their processability and electrochemical stability, yet slimmer and more flexible SPE with higher ionic conductivity is still desired. Herein, an ultrathin (35 µm), rigidity-enhancing co-blending SPEs design using electrospinning was proposed, blending bio-polyamide with a N-substituted pyrrolidone ring (IBD) with polyethylene oxide/lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI). IBD is confirmed to possess the dominant Li+ affinity. Then IBD with flexible chain segments of PEO, triggers a concerted ion-transport mechanism synergistically, in which IBD is responsible for the processes of enhanced ion-pair dissociation resulting in dynamic association between the mobile cations and the long-chain molecules that constitute the SPE. Meanwhile, it could broaden the ion transport channel in some extent. The ionic conductivity of the SPE is up to 4.26 × 10−4 S cm−1 at 50 ℃. Furthermore, the high strength modulus, low crystallinity, and ultra-thin characteristic of IBD-PEO/LiTFSI power-assisted the ASSLIBs of LiFePO4//Li to achieve extraordinary cycle performance (80.5 % capacity retention after 580 cycles at C/2 rate) and the average coulomb efficiency exceeds 99.5 % at 50 ℃. Moreover, it has the ability to withstand folding and bending conditions.

High-voltage ionic liquid-based flexible solid polymer electrolyte for high-performance Li-ion batteries

Ionic liquid–solid polymer electrolyte membrane for sustainable battery technology.

Optimized CeO2 Nanowires with Rich Surface Oxygen Vacancies Enable Fast Li‐Ion Conduction in Composite Polymer Electrolytes

Low‐cost and flexible solid polymer electrolytes are promising in all‐solid‐state Li‐metal batteries with high energy density and safety. However, both the low room‐temperature ionic conductivities and the small Li+ transference number of these electrolytes significantly increase the internal resistance and overpotential of the battery. Here, we introduce Gd‐doped CeO2 nanowires with large surface area and rich surface oxygen vacancies to the polymer electrolyte to increase the interaction between Gd‐doped CeO2 nanowires and polymer electrolytes, which promotes the Li‐salt dissociation and increases the concentration of mobile Li ions in the composite polymer electrolytes. The optimized composite polymer electrolyte has a high Li‐ion conductivity of 5 × 10−4 S cm−1 at 30 °C and a large Li+ transference number of 0.47. Moreover, the composite polymer electrolytes have excellent compatibility with the metallic lithium anode and high‐voltage LiNi0.8Mn0.1Co0.1O2 (NMC) cathode, providing the stable cycling of all‐solid‐state batteries at high current densities.

A Flexible Solid Polymer Electrolyte Featured with Ultrahigh Salt Concentration for High-Voltage Cathode

A Flexible Solid Polymer Electrolyte Featured with Ultrahigh Salt Concentration for High-Voltage Cathode

Safe, superionic conductive and flexible “polymer-in-plastic salts” electrolytes for dendrite-free lithium metal batteries

Solid polymer electrolytes (SPEs) garner tremendous attention for both enabling higher energy density battery chemistry and alleviating the safety concerns of liquid electrolytes, but the practical utilizations of SPEs are severely hindered by the limited room temperature ionic conductivity, low transference number and huge interface impedance. Unlike the polymer chain movement in traditional SPEs, in the present work, we develop novel “polymer-in-plastic salts” electrolytes (PIPSEs) via a high weight ratio of plastic salts to polymer in which polymer just function as framework so that non-flammable, superionic conductive and flexible SPEs can be obtained. Also, the high content of plastic salts in PIPSEs can wet electrodes and form compatible solid electrolyte interface (SEI) with lithium metal. As a consequence, solid-state dendrite-free symmetric Li cells with PIPSEs show ultralong cycle life over 1000 h under up to 2.0 mA cm−2 and Li/LiFePO4 and high-voltage Li/LiNi0.6Co0.2Mn0.2O2 cells utilizing above PIPSEs exhibit excellent cycle performance and appealing rate performance. It is anticipated that our work provides a new strategy for the next-generation solid-state batteries.

Three-dimensional porous ceramic framework reinforcing composite electrolyte

All solid-state lithium batteries demonstrate excellent characteristics of high safety and energy density, which make them very promising energy storage devices. Among various kinds of solid electrolytes, rigid-flexible coupling composite electrolyte combines the advantages of rigid solid inorganic ceramic electrolytes, i.e., excellent room temperature ionic conductivity, and of flexible solid polymer electrolytes, i.e., the flexibility, and thereby is considered to be one of the most ideal electrolyte candidates for all solid-state lithium batteries. Dispersing 0- or 1-dimensional inorganic fillers is a widespread method to fabricate rigid-flexible coupling composite, where the ionic conductivity of polymer can be improved by one order of magnitude mainly due to the decreased degree of crystallinity. However, aim to further increase the ionic conductivity by increasing the filler content cannot be accomplished because of the fillers' tendency to aggregation. what's more, the highly conductive inorganic fillers are separated by the polymer phase and thus cannot form fast and continuous Li<sup>+</sup> transportation channels. Accordingly, inorganic fillers which can provide percolated pathway for Li<sup>+</sup> transportation and avoid aggregating are highly desirable. To this end, different from adding 0- or 1-dimensional inorganic fillers into polymer matrices, polymers can be cast into porous inorganic substrates, that is, 3-dimensional porous ceramic framework, to obtain organic-inorganic composite electrolyte, in which organic phase, inorganic phase, and organic/inorganic interfacial phase are all continuous for fast Li<sup>+</sup> transportation. And meanwhile, its self-supported structure prevents the agglomeration of inorganic particles. In recent years, the 3-dimensional porous ceramic framework has been more and more frequently used in rigid-flexible coupling composite electrolytes. To have a deep insight into the positive function of 3-dimensional porous ceramic framework, in this review, we firstly reveal the mechanism of the huge improvement in the ionic conductivity and thermostability of the composite electrolyte. Then, we summarize the frequently used preparation methods of the 3-dimensional porous ceramic framework reported recently. Finally, for the future perspective of rigid-flexible coupling composite electrolyte development, we propose two feasible improvement strategies. This review can thereby provide great significance of designing solid electrolytes with comprehensive performance for all solid-state lithium batteries with high energy density and superior safety.

Effect of Temperature on Electrical Properties of Reduced Graphene Oxide (rGO)/Li-ion Embedded Flexible Solid Polymer Electrolyte Films

Reduced graphene oxide (rGO) was synthesized from graphite powder by modified Hummers method. The rGO is emerged with Polystyrene sulfonic acid/Lithium phosphate to prepare PL-rGO solid polymer electrolyte films. The electrical properties of Polystyrene sulfonic acid/Lithium phosphate/reduced graphene oxide composites were analyzed, which is an essential property to obtain the performance, reliability and lifetime of battery with respect to temperature. The mass and charge transfer process that takes place at the interface of electrode and electrolyte was obtained by Impedance analyzer. The Nyquist plots were plotted in the frequency range 1 Hz- 35 MHz at different temperatures (30-100OC). The ionic conductivity of PL-rGO polymer electrolyte is 1.4x10-3 S/c.m has been observed for the composition PSSA/Li3PO4/rGO::50:45:05 wt%. The conductivity of PL-rGO composites is directly related to temperature. The hopping of the ions in the PL-rGO is observed by using dc conductivity which follows the Arrhenius relationship

Investigation on transport and thermal studies of solid polymer electrolyte based on carboxymethyl cellulose doped ammonium thiocyanate for potential application in electrochemical devices

In this work, a free standing and flexible solid polymer electrolyte (SPE) based on non-hazardous and environmental friendly material, carboxymethyl cellulose (CMC) was successfully produced in order to overcome environmental and pollution issues. The effect of doping ammonium thiocyanate (NH4SCN) into SPE based on carboxymethyl cellulose (CMC) on transport, thermal and electrochemical stability window properties have been investigated for potential application in electrochemical devices. CMC-NH4SCN SPE was prepared via solution casting technique. The properties of the prepared CMC-NH4SCN SPE were characterized via Fourier transform infrared spectroscopy (FTIR) deconvolution, transference number measurement (TNM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and linear sweep voltammetry (LSV) techniques. FTIR deconvolution was performed in order to investigate the dissociation of ions and transport properties of CMC-NH4SCN SPE system and it can be correlated with the ionic conductivity of CMC-NH4SCN SPE system. The result of TNM was obtained via a DC polarization method where the ionic transference number for the highest conducting CMC-NH4SCN SPE was found to be 0.93. Thus, it can be suggested that the conducting species for the highest conducting CMC-NH4SCN SPE are mainly due to ions. TGA was performed to investigate the thermal stability of CMC-NH4SCN SPE. The value of glass transition temperature of CMC-NH4SCN SPE was obtained from DSC analysis. Electrochemical stability window of the highest conducting CMC-NH4SCN SPE obtained from LSV technique was up to 1.6 V. As a result, it can be inferred that the highest conducting CMC-NH4SCN SPE had shown a promising performance and has a great potential to be applied in electrochemical devices application such as proton batteries.

Synthesis and electrochemical studies on sodium ion conducting PVP based solid polymer electrolytes

The flexible solid polymer electrolytes based on polyvinyl pyrrolidone (PVP) complexed with sodium nitrate have been developed for battery applications. The amorphous natures of the prepared films have been discussed by X-ray diffraction studies. The maximum ionic conductivity value of 1.21 × 10−5 S/cm is obtained for 6 wt% of NaNO3 doped system. The prepared membranes are ionic conductors which is proved by transport studies. The mobility and diffusion coefficient of Na+ ions in the prepared SPEs were estimated. Electrochemical characterization has been carried out by assembling Na-ion conducting symmetry cell. The pseudo-capacitance behavior of the electrolyte is also confirmed by cyclic-voltammetry studies. The solid state battery (Na||94PVP:06NaNO3||I2 + C) has been constructed using the higher conducting membrane and its properties are studied.

Investigations on binary metal oxide based polyvinyl pyrrolidone/sodium nitrate polymer electrolytes for electrochemical cell applications

The flexible solid polymer electrolytes (SPE) based on polyvinylpyrrolidone (PVP):sodium nitrate (NaNO3) with binary metal oxide (BMO) have been prepared. The binary metal oxides (CuWO4 and BiVO4) are synthesized by using hydrothermal method and tested with X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The maximum ionic conductivity value of 1.018 × 10−4 S/cm (at 303 K) is obtained for PVP:NaNO3:BiVO4 system. The prepared electrolytes are ionic conductors which is proved by transport studies.The high conducting SPE can withstand upto 3.5 V from Linear Sweep Voltammetry studies (LSV) and it shows good cyclic behavior (CV studies). The open circuit voltage (OCV) of the electrochemical cell is observed to be 3.5 V.

A solid polymer electrolyte based on star-like hyperbranched β-cyclodextrin for all-solid-state sodium batteries

A star-like hyperbranched β-cyclodextrin is designed and synthesized for the solid polymer electrolyte of all-solid-state sodium batteries by grafting β-cyclodextrin with multiple oligo(methyl methacrylate)-block-oligo(ethylene glycol) methyl ether methacrylate short chains. Complexing this star-like hyperbranched β-cyclodextrin with sodium trifluomethanesulfonate salt leads to a self-standing, transparent, and flexible solid polymer electrolyte film. It is found that this solid polymer electrolyte exhibits superior thermal stability, excellent mechanical properties at the even elevated temperature and good interfacial stability against Na metal electrode. Especially, ascribing to the unique three-dimensional structure of the star-like hyperbranched β-cyclodextrin, a solid polymer electrolyte formed with the optimized star-like hyperbranched β-cyclodextrin containing 69.3 wt.% oligo(ethylene glycol) methyl ether methacrylate shows an ionic conductivity of 1.3 × 10−4 S cm-1 at 60 °C and a wide electrochemical window of 5.2 V vs. Na+/Na, which are superior to those of the previously reported solid polymer electrolytes. The all-solid-state Na/NaNi1/3Fe1/3Mn1/3O2 cell shows high first discharge capacity (102.4 mAh g−1 at 0.1C), good reversibility and excellent cycling performance (with 87.8% capacity retention after 80 cycles at 0.1C) at 60 °C. All the results indicate that the star-like hyperbranched β-cyclodextrin is a promising polymer for the solid polymer electrolyte of all-solid-state sodium batteries.

Graphene oxide as a filler to improve the performance of PAN-LiClO4 flexible solid polymer electrolyte

Solid polymer electrolytes (SPEs) show structural flexibility and safety to meet the requirements of lithium battery applications. However, SPEs usually have a low ionic conductivity at room temperature. In this study, in order to improve the ionic conductivity, we add graphene oxide (GO) as a nano-filler into LiClO4-polyacrylonitrile (PAN) type SPEs with various weight percentages. The ionic conductivity of the composite SPE containing 1.0wt% GO has reached 4.0×10−4Scm−1 at 30°C, which is one order of magnitude higher than the bare one (2.2×10−5Scm−1 at 30°C). Meanwhile, the activation energy has reduced from 2.31 to 1.03eV and the tensile modulus has increased from 37 to 80MPa. This improvement is mainly ascribed to the functional groups (OH, COOH, CO, COC, et al.) in GO that can alleviate the polarity of “CN:”, which makes the polymer softer and facilitates the dissociation of LiClO4 in PAN matrix. Moreover, the LiFePO4 (LFP) cell with 1.0wt% GO-SPE as electrolyte shows a satisfactory average discharge capacity of 166mAhg−1 at 0.2C, which is better than the performance in the GO-free type cell (136mAhg−1).

In-situ plasticized polymer electrolyte with double-network for flexible solid-state lithium-metal batteries

Flexible solid polymer electrolyte (SPE) confers lithium-based batteries with high energy densities and diverse packaging. However, the application of SPE is hindered by the contradiction between ionic conductivity and mechanical strength. Herein, this issue can be effectively addressed by constructing an in-situ plasticized SPE with double-network (DN-SPE) through reasonably controlling the chain length of constitutional unit. With the self-plasticization of its double network, the bendable DN-SPE exhibits increased ionic conductivity (from 10-5 to 10-4.5Scm-1 at room temperature), high thermal stability (up to 200°C) and good capacity to suppress the growth of lithium dendrite. The resultant solid-state lithium-metal batteries exhibit admirable reversible specific capacity. Notably, pouch cells maintain their electrochemical functions well even under stringent bending and truncated conditions. Structural modulation of the in-situ plasticized DN-SPE demonstrates an effective strategy to enhance the ion conductivity of SPE and might grasp new insights into flexible solid-state lithium-metal batteries.

Electrospun poly(ethylene oxide) nanofibrous composites with enhanced ionic conductivity as flexible solid polymer electrolytes

Solid polymer electrolytes (SPEs) have great potential to address the safety issues of lithium (Li)-ion batteries when compared with conventional liquid electrolytes, which makes them a promising alternative for next-generation high-energy batteries. In this work, poly(ethylene oxide)-lithium perchlorate (PEO–LiClO4) polymer electrolytes for Li-ion batteries were prepared using electrospinning. The crystallinity, ionic conductivity as well as mechanical properties were investigated. Ionic conductivities and mechanical properties of PEO–LiClO4 based SPE have been obviously increased by incorporating modified TiO2 nanofibres (TNFs) than TiO2 nanoparticles (TNPs), due to that both TNFs and TNPs can decrease the crystalline phase concentration of PEO and increase segmental flexibility of PEO. The SPE with 3 wt% TNFs exhibits the highest conductivity of 5.308 × 10−5 S cm−1 at 20°C and higher tensile strength of 13.8 MPa. These results highlight the potential of utilising the electrospinning method to improve the ionic conductivity of SPEs.

Study of Crosslinked Solid Polymer Electrolyte for All-Solid-State Lithium Battery

Developing all-solid-state lithium batteries has been one of the most effective methods to ensure safety for new energy devices, especially with flexible solid polymer electrolyte as a crucial component. However, the electrolyte exhibits low ionic conductivity at room temperature that obviously inhibits the progress of all-solid-state lithium batteries. In this study, we develop a few solid polymer electrolytes to enhance the lithium ion transport ability by using crosslinking polymer methods. The results show that adjustments of the cross-linked centers and branches of the polymer significantly improve the ionic conductivity of the electrolyte. Besides, all-solid-state lithium sulfur batteries with the solid electrolytes are studied. The morphology and structures at the electrode/electrolyte interfaces during the charge and discharge processes are investigated by FIB-SEM, EIS, FTIR and NMR. The effects of molecular structures of solid polymer electrolytes on ionic conductivity and interfacial compatibility are discussed.