Polymer Electrolytes For Lithium Batteries Research Articles

Facile and Powerful In Situ Polymerization Strategy for Sulfur-Based All-Solid Polymer Electrolytes in Lithium Batteries.

All-solid-state polymer electrolytes can improve the safety of lithium batteries. However, the common Bellcore polymer electrolyte technology faces several issues such as wasting a mass of solvent, high manufacturing cost, and poor interfacial compatibility between polymer electrolytes and electrodes. Herein, we propose an in situ polymerization technique to synthesize all-solid-state polymer electrolytes by a thiol-Michael addition click reaction. The alternating copolymer is made from the Michael addition reaction of ethylene glycol dimethacrylate (EGDMA) and 1,2-ethane dithiol (EDT). At ambient temperature, the obtained composite polymer electrolyte displays an ionic conductivity of 3.02 × 10-5 S/cm, an electrochemical window of 4.5 V, and a lithium-ion transference number of 0.45. In light of this unique polymerization process, the traditional fabrication method of liquid electrolyte-based lithium batteries can be adopted in the current study for the preparation of all-solid-state Li/LiFePO4 batteries. It was found that the assembled all-solid-state Li/LiFePO4 batteries exhibited superior charging/discharging performance and preferable safety. Thus, this facile and powerful in situ polymerization strategy may open up a new approach for the design and fabrication of all-solid-state batteries with desirable performances.

Seaweed extractions as promising polymer electrolytes for lithium batteries

Polymer electrodes are vital components of lithium-ion batteries and have gained great interest in recent years. Currently, the majority of electrodes are petroleum-based that are toxic and non-biodegradable, which consists of serious environmental concerns. Therefore, exploration of natural polymer electrolytes, such as seaweed extracts, balances non-toxicity and ion conductivity as new research directions. In this review, we mainly focus on the progress of polymer electrolytes based on alginate, kappa carrageenan, and other natural polymers of seaweed extracts, including agar and iota carrageenan. We first give a brief overview of the fundamentals of polymer electrolytes. Then, we discuss the structures and performances of seaweed extracts derived polymer electrolytes. Finally, we compare the ion conductivity of natural polymer derived electrolytes and synthetic polymers, and insights on the future direction for improvement of this field.

Beyond fluorine: sustainable ternary polymer electrolytes for lithium batteries

A non-fluorinated solid polymer electrolyte including an ionic liquid has achieved a higher transference number and similar lithium transport as compared to its fluorinated analog and allows the cycling of LiFePO4||Li metal cells for 300 cycles.

Flame retardant polyphosphoester copolymers as solid polymer electrolyte for lithium batteries

Solid-state lithium batteries are considered one of the most promising battery systems due to their high volumetric energy density, in this work a flame retarded polymer electrolyte is proposed.

Sulfonylimide-Based Cation Exchange Membranes As Electrolyte for Lithium-Ion Batteries. Synthesis and Characterization

The use of cation-exchange membranes as electrolytes in lithium-ion batteries is considered to be one of their highly promising applications. Polystyrene-based membranes containing sulfonylimide functional groups are the promising materials for these application due to the low crystallinity of polymer, high dissociation degree of functional groups, as well as thermal and electrochemical stability of obtained electrolytes. There are two different approaches for the synthesis of sulfonylimide based polymers: polymerization of functional monomer [1], and functionalization of the polymer [2]. The aim of this work was to synthesize membranes based on polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) containing functional sulfo R–SO3Li and sulfonylimide groups [R–SO2NSO2–X]Li, where X= –CF3, –CCl3, –CH3, –C6H5, –p-NO2C6H4 and –p-CF3C6H4, and investigation of Li+ conductivity of polyelectrolytes solvated by mixtures of ethylene carbonate/dimethylacetamide (EC-DMA) and ethylene carbonate/propylene carbonate (EC-PC). Membranes were synthesized according to the Scheme.To prepare plasticized polymer electrolytes, the synthesized dry SSEBS and SSEBS-X membranes in the Li+ form were transferred to a dry argon box (humidity level <10 ppm) and placed in the solutions containing equal volumes of EC-DMA or EC-PC for 24 h. Solvation degrees (n) of the membranes with EC-DMA and EC-PC mixtures were calculated as a ratio of the number of solvent molecules to the total number of membrane functional groups.The acid-base titration was used to determine full ion-exchange capacity (IEC) of the SSEBS membrane containing functional sulfo groups, as well as the residual amount of R–SO3 - functional groups in the SSEBS-NH2 membrane after the amination.The structure of SEBS, SSEBS and SSEBS-X were proven by ATR IR spectroscopy, using Nicolet iS5 IR in the frequency range 4000-500cm-1, and CHNS analysis, using EuroVector ЕА3000 equipment.Ionic conductivity of the obtained polymer electrolytes in the Li+ form plasticized by EC-PC and EC-DMA mixtures was investigated by impedance spectroscopy in the temperature range 0...+50 °С under the argon atmosphere, using the alternating current bridge Elins Z-1500J (frequency range from 2 MHz to 10 kHz) on symmetrical cells carbon/membrane/carbon. Resistance was determined from the intercept with the axis of active resistances in Nyquist plot.Optimal concentrations and equivalent excesses required for complete transformation of R–SO2NH2 groups into sulfonylimide functional groups [R–SO2NSO2–X]M by the Hinsberg reaction were found using phenylsulfonyl chloride. In particular, 1.5М is the minimal concentration of sulfonyl chloride in the mixture, and minimal excesses of sulfonyl chloride and triethylamine with respect to the amount of R–SO2NH2 groups are 10 and 3, respectively.IEC of the obtained membranes SSEBS-X are 1.54-1.68 mmol∙g-1. Solvation of the membranes with the EC-PC solvent mixture, which is the most common solvent in lithium-ion batteries, is not efficient for this purpose due to low solvation capability of organic carbonates and a high viscosity of the mixture. The solvation number of the membranes with this mixture does not exceed 1.7 solvent molecules per functional group, and Li+ conductivity is equal to or below 2∙10-3 mS∙cm-1 at 25°С. The use of amide-containing solvents leads to an increase of ionic conductivity of the sulfonylimide-based membranes due to specific interactions that determine their high solvation capability. In particular, when the EC-DMA mixture is used the solvation degree and ionic conductivity of the SSEBS-CF3 membranes at 25°С increase to 14.1 and 1 mS∙cm-1, respectively.The lowest solvation degree (1.9 solvent molecules per sulfonic group) and conductivity (0.1 mS∙cm-1 at 25°С) was found for the SSEBS membrane and the largest values were found for the SSEBS-CF3 polymer that contains trifluoromethanesulfonylimide functional groups (14.1 solvent molecules per 1 sulfonic group and 1.1 mS∙cm-1 at 25°С)According to acidity of [R–SO2NHSO2X] groups negative charge delocalization degree decreases along the following sequence X=CF3>CCl3>p-CF3Ph>Ph, whereas the sulfonic group should be placed at the end of the sequence having the lowest acidity. Such consistency of measured ionic conductivity and calculated acidity.This work was financially supported by the Russian Science Foundation (project No 17-79-30054) Bouchet, S. Maria, R. Meziane, A. Aboulaich, L. Lienafa, J.-P. Bonnet, T.N.T. Phan, D. Bertin, D. Gigmes, D. Devaux, R. Denoyel, M. Armand. Single-ion BAB triblock copolymers as highly efficient electrolytes for lithium-metal batteries // Nat. Mater. 2013. V. 12. P. 452-457. Rohan, Y. Sun, W. Cai, Y. Zhang, K. Pareek, G. Xu, H. Cheng. Functionalized polystyrene based single ion conducting gel polymer electrolyte for lithium batteries // Solid State Ionics 2014. V. 268. P. 294-299. Figure 1

Solid Polymer Electrolytes in Lithium Batteries: Challenges and Opportunities for High Specific Energy

Besides enhanced safety aspects, solid polymer electrolytes (SPEs) offer the opportunity to increase the specific energy of secondary batteries by enabling lithium metal as negative electrode in all-solid-state lithium batteries (ASSLB). Therefore, the SPE needs to provide sufficient mechanical strength to prevent short circuits caused by lithium dendrite penetration especially favoured at high current densities.[1] In order to obtain the maximum specific energy of ASSLBs, lithium metal negative electrodes are combined with high voltage positive electrodes, e.g. LiNi0.6Mn0.2Co0.2O2 (NMC622).[2]In the frame of this work, a novel SPE is applied to NMC622 based ASSLB cells and studied regarding energy limits on battery cell and pack level. In a first step, the active mass loading is systematically increased revealing the specific energy limit on battery cell level. Additionally, the chosen system is applied to a bipolar (serial) stacking aiming towards further energy improvements on battery pack level.[3] In sum, this work reveals remaining challenges but still points towards opportunities enabling the aimed energy increase of ASSLBs.[1] G. Homann, L. Stolz, J. Nair, I. C. Laskovic, M. Winter and J. Kasnatscheew, Sci Rep, 10, 4390 (2020).[2] J. Kasnatscheew, M. Evertz, R. Kloepsch, B. Streipert, R. Wagner, I. Cekic Laskovic and M. Winter, Energy Technology, 5, 1670-1679 (2017).[3] G. Homann, P. Meister, L. Stolz, J. P. Brinkmann, J. Kulisch, T. Adermann, M. Winter and J. Kasnatscheew, ACS Appl. Energy Mater., 3, 4, 3162–3168 (2020). Figure 1

Difunctional block copolymer with ion solvating and crosslinking sites as solid polymer electrolyte for lithium batteries

High conductivity, solid polymer electrolytes (sPE) are an enabling technology for safe, high energy-density lithium ion batteries. Unfortunately, polymer architectures with high ion conductivity are usually associated with poor mechanical properties. In this study, a difunctional block copolymer (DFBCP) which addresses the need has been synthesized and demonstrated. The first block, P(DBEA-co-MA), has tethered double bonds and can form a dense, crosslinked network upon UV irradiation to provide mechanical strength. The second block is a pendant type polyethylene glycol (PEG) moiety with low crystallization to provide ion solvation. The PEG moiety is confined on one side of the polymer and has high segmental motion, resulting in an adequate ionic conductivity, 0.6 mS/cm. The amorphous nature of PEG second block also ensures low interfacial resistance, <80 Ω∙cm2, and mechanical adaptability to electrode volumetric changes. The combined advantages of high conductivity, low interfacial resistance and good mechanical stability enable full cell durability, >1000 cycles at 2C in a Li–LiFePO4 battery.

Design and Construction of Cross-Linked PEO with the Integration of Helical Polyurethane as an Advanced All-Solid-State Polymer Electrolyte for Lithium Batteries

All-solid-state polymer electrolytes (SPEs) have been regarded as an advisible alternative for simultaneously overcoming the safety issues and high energy density demands presented in traditional lithium batteries, and they represent the development orientation of energy storage devices. This course describes the preparation of a cross-linked and helical polyurethane modified poly(ethylene oxide) (PEO@HPU) and its utilization as the SPE in lithium batteries, which can be used to teach upper-division undergraduates the principle of energy storage devices and the role of liquid-free electrolytes. Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopies are used to determine the structure of the polymers. The ionic conductivity, lithium ion transference number, and electrochemical window of PEO@HPU are measured through an electrochemical workstation. The lithium batteries assembled by students are evaluated via a battery testing system. The modification by the special helical polymer obviously improves the electrochemical and battery performance of the PEO-based SPE. Upon completion of the experiment, students will understand the structure–activity relationship in materials science and propose new suggestions for designing advanced SPEs. This experiment requires well-prepared laboratory chemicals as well as long-term processes, so it is suitable to be considered as a project. Meanwhile, it can be also used for senior projects and interdisciplinary projects between engineering and science.

Advances in Composite Polymer Electrolytes for Lithium Batteries and Beyond

AbstractConventional lithium‐ion batteries have approached their capacity and energy density limits. Use of lithium metal anode can enable high‐energy batteries. However, the safety hazards and lithium dendrite formation associated with lithium metal require safe electrolytes to replace flammable liquid ones. In recent years, solid‐state electrolytes have attracted tremendous attention. Among them, composite polymer electrolytes (CPEs) with different constitutions have the unique advantages of low interfacial resistance, high ionic conductivity, and flexible characteristics. Here, the basic properties and analysis methods related to CPEs are discussed. Following that, the components added into the polymer matrix, such as organic solvents, nanostructured ceramics, and fast‐ion‐conductive inorganics are classified. CPEs used in low‐cost Na and K batteries are briefly discussed. It is hoped that the review can supply both advances and fundamentals to the researchers in this field and provide guidance for the development of CPEs for lithium battery systems, and beyond.

Thermally and Oxidatively Stable Polymer Electrolyte for Lithium Batteries Enabled By Phthalate Plasticization

Solid-state lithium batteries are desirable alternatives to lithium ion batteries given their high theoretical energy densities associated with Li metal anodes and the potentially superior safety from the elimination of flammable liquid electrolytes. Compelling ceramic lithium conductors with ionic conductivities surpassing those of conventional liquid electrolytes have been developed, but they suffer from high fabrication and processing costs. Moreover, achieving intimate solid-solid contact at the electrolyte-electrode interface is challenging. Polymer electrolytes are alternative materials that offer processing ease and the ability to fully infiltrate and wet composite electrodes. Poly(ethylene oxide) (PEO) mixed with lithium salt is the archetypical polymer electrolyte and solid-state cells using LiFePO4 cathode and lithium metal anode have been successfully commercialized. However, a significant limitation of PEO is its low oxidative stability, which restricts its application to lower voltage cathode (e.g. LiFePO4). Thus, polymer electrolytes with higher oxidative stabilities are desperately needed. In previous work, our group investigated hydrogenated nitrile butadiene rubber (HNBR) as a candidate for high-voltage application because of its superior oxidative stability of 5.3 V vs. Li/Li+. This polymer readily dissolves lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt and has a high lithium transference number (0.59 compared to 0.37 for PEO). However, HNBR-LiTFSI suffers from low ionic conductivity (3.6×10-8 S·cm-1 at 20°C), which severely limits transport in full solid-state cells. In this work, phthalates were employed as the plasticizer to increase the conductivity of the HNBR-based electrolyte. FTIR shows that phthalates not only enhance the segmental mobility of the polymer chains but also coordinate with Li+ and participate in the solvation of lithium salt. Phthalates have a broad liquid-phase window preventing potential phase separation in the polymer electrolyte and evaporation at elevated temperatures. Their low HOMOs (e.g. -10.7 eV for di-ethyl-phthalate) should translate to higher oxidative resistance. A series of di-alkyl-phthalate homologues differing in the length of the alkyl branches were investigated in this report. Plasticized polymer electrolytes were prepared by blending HNBR-LiTFSI and a given amount of phthalate in acetone solution, and then casting into a mold and evaporating the volatile acetone. The plasticized electrolyte can withstand 159°C without significant evaporation; the decomposition of HNBR occurs at over 400°C even in a pure O2 environment. The conductivity of HNBR-LiTFSI with di-ethyl-phthalate (up to 20 wt.%) was 7.3×10-7 S·cm-1 at 20°C and 4.4×10-5 S·cm-1 at 70°C. The electrochemical oxidative stability of both HNBR-LiTFSI and plasticized-HNBR-LiTFSI was assessed by linear sweep voltammetry. The oxidation potential was reduced from 5.3 V to 5.2 V vs. Li/Li+ after introducing phthalates. Electrochemical impedance analysis showed that a resistive interface developed between HNBR-based electrolytes and lithium, indicating a chemical incompatibility between HNBR and lithium metal. However, this problem was readily addressed through a laminated electrolyte structure where a layer of PEO/LiTFSI physically separated plasticized HNBR/LiTFSI from direct contact with lithium metal. The effectiveness of this structure was confirmed by over 2000 hours of reversible galvanostatic cycling of symmetric lithium metal electrodes at 70°C.

3D Printable Ionogels with High Ionic Conductivity

Hybrid materials based on ionic or polymer components are very useful in electrochemical devices like battery systems or fuel cells due to their unique properties like thermal and electrochemical stability and polarity. For all advances over the past, lithium ion based materials are still costly, limited and not very stable. Currently, solid-state polymer electrolytes (SPEs) and gel polymer electrolytes (GPEs) [1] have ion conductivities below 10-4 S/cm at room temperature.Polymer electrolytes can be established by ionic liquids (ILs) which combine beneficial properties like high ionic conductivity, wide electrochemical potential window and high viscosity. These kinds of electrolytes can be very beneficial in solid-state batteries for example. This technology has garnered immense excitement from investors and large corporations. The main advantage of all-solid-state to liquid electrolyte-based batteries is that the size can be easily made smaller e.g. solid‐state electrolytes have a typical thickness of approximately 1.0 μm, whereas the separator in liquid electrolyte‐based cells typically has a thickness of 20 μm. Several investigators are exploring 3D architectures for thin-film rechargeable battery electrodes. Nevertheless additive manufacturing, also known as 3D printing, could revolutionize the structural properties of batteries. In addition, this technology could improve the adaptability of the electrolyte to the electrodes.This scientific approach introduces the possibility to combine ionic liquids with a commercial photoreactive resin to realise a well-defined structure by using stereolithography (SLA). This provides, for the first time, access to ionogels (IGs) with complex 3D shapes (figure 1a) with potential application in battery or fuel cell technology. For first experiments new IGs were prepared by adding a series of sulfonate-based ionic liquids (ILs), 1-methyl-3-(4-sulfobutyl)imidazolium para-toluenesulfonate [BmimSO3H][pTS], 1-methyl-1-butylpiperidiniumsulfonate para-toluenesulfonate [BmpipSO3][pTS], and 1-methyl-3-(4-sulfobutyl) imidazolium methylsulfonate [BmimSO3H][MeSO3] with a clear photoreactive resin which were used in a Form 2 3D printer [2]. Moreover, the IGs are thermally stable up to about 200 °C and mechanically robust. In addition to this synthesized protic conductive IGs, sulfobataine, metal and lanthanides containing IGs were prepared and analysed. These IGs exhibit higher conductivities compared to the sulfonated based IGs in the range from 10-4 to 10-2 S/cm at room temperature. 3D Printable metal-lanthanide IGs could possibly be an adequate replacement for lithium-ion electrolytes. Figure 1: a) Well-defined structures of IGs by SLA, b) Rhd battery cell for electrochemical measurements. Literature: [1] Stephan, A.M., Review on gel polymer electrolytes for lithium batteries. European polymer journal, 2006. 42(1): p. 21-42. [2] Zehbe, K.; Lange,A.; Taubert, A., Stereolithography provides access to 3D printed ionogels with high ionic conductivity, Energy and Fuels, accepted. Figure 1

Partially Oxidized Cellulose grafted with Polyethylene Glycol mono-Methyl Ether (m-PEG) as Electrolyte Material for Lithium Polymer Battery

Herein, a novel cellulose derivative has been synthesized and investigated as a nature-derived solid polymer electrolyte for lithium batteries. Cellulose is oxidized in a two-step process to dicarboxylic acid cellulose to allow for grafting low molecular weight poly(ethylene glycol) monomethyl ether (550 g mol-1) via Fischer–Speier esterification at the thus obtained carboxyl groups. The chemical structure of the synthesized materials is confirmed by Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy as well as X-ray diffraction. Incorporating lithium bis(trifluoromethane-sulfonyl)imide (LiTFSI) as conducting salt and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) ionic liquid as plasticizer results in the realization of an amorphous and solvent-free solid polymer electrolyte. These electrolyte membranes are characterized by high thermal and electrochemical stability and ionic conductivities of about 1×10−5 S cm−1 at 20 °C and 2.5×10−4 S cm−1 at 80 °C, which enables very stable lithium stripping and plating for more than 800 h.

Tuning the Properties of a UV-Polymerized, Cross-Linked Solid Polymer Electrolyte for Lithium Batteries.

Lithium metal anodes have been pursued for decades as a way to significantly increase the energy density of lithium-ion batteries. However, safety risks caused by flammable liquid electrolytes and short circuits due to lithium dendrite formation during cell cycling have so far prevented the use of lithium metal in commercial batteries. Solid polymer electrolytes (SPEs) offer a potential solution if their mechanical properties and ionic conductivity can be simultaneously engineered. Here, we introduce a family of SPEs that are scalable and easy to prepare with a photopolymerization process, synthesized from amphiphilic acrylic polymer conetworks based on poly(ethylene glycol), 2-hydroxy-ethylacrylate, norbornyl acrylate, and either lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) or a single-ion polymethacrylate as lithium-ion source. Several conetworks were synthesized and cycled, and their ionic conductivity, mechanical properties, and lithium transference number were characterized. A single-ion-conducting polymer electrolyte shows the best compromise between the different properties and extends the calendar life of the cell.

Composite polymer electrolytes reinforced by two-dimensional layer-double-hydroxide nanosheets for dendrite-free lithium batteries

Applications of polymer electrolytes in lithium batteries are lagged by the low ionic conductivity and lithium-ion transference number, and polymer electrolytes are mechanically weak to suppress lithium dendrites. Herein, two-dimensional layer-double-hydroxide (2D LDH) nanosheets are introduced into polyethylene oxide (PEO) as fillers for the first time. After blending with 2D LDH fillers, the composite polymer electrolyte (CPE) exhibits an optimized conductivity with a lithium-ion transference number of 0.42. Additionally, the mechanical strength and electrochemical stability of the CPE at high voltages are improved. More importantly, the CPE shows a markedly enhanced stability against dendritic lithium, and the current density for dendrite-free Li plating/stripping in the CPE arises to 800 μA cm−2 at 60 °C. Solid-state lithium batteries based on the PEO/LDH CPEs show an initial discharge capacity of ~138 mA h g−1 with a capacity retention of 88% after 100 cycles at 0.2 C and 60 °C.

Influence of the Cyclic versus Linear Carbonate Segments in the Properties and Performance of CO2-Sourced Polymer Electrolytes for Lithium Batteries

Polycarbonates bearing linear carbonate linkages and polyether segments have demonstrated to be highly attractive solid electrolyte candidates for the design of safe energy storage devices, for example, lithium metal batteries. In this contribution, we are studying the influence of the introduction of some cyclic carbonate linkages within the polymer backbone on the electrolyte properties. We first describe the synthesis of polycarbonates/polyethers containing different contents of both linear and cyclic carbonate linkages within the chain by the copolymerization of a highly reactive CO2-based monomer (bis(α-alkylidene cyclic carbonate)) with poly(ethylene glycol) diol and a dithiol at room temperature. We then explore the influence of the content of the cyclic carbonates and the loading of the polymer by lithium bis(trifluoromethane) sulfonimide (LiTFSI) on the electrolyte properties (glass transition and melting temperatures, ion conductivity, and diffusivity). The best electrolyte candidate is characterized by a linear/cyclic carbonate linkage ratio of 82/18 when loaded with 30 wt % LiTFSI. It exhibits an ion conductivity of 5.6 × 10–5 S cm–1 at 25 °C (7.9 × 10–4 S cm–1 at 60 °C), which surpasses by 150% (424% at 60 °C) the conductivity measured for a similar polymer bearing linear carbonate linkages only. It is also characterized by a high oxidation stability up to 5.6 V (vs Li/Li+). A self-standing membrane is then constructed by impregnating a glass fiber filter by this optimal polymer, LiTFSI, and a small amount of a plasticizer (tetraglyme). Cells are then assembled by sandwiching the membrane between a C-coated LiFePO4 (LFP) as the cathode and lithium as the anode and counter electrode. The cycling performances are evaluated at 0.1 C at 60 °C and room temperature for 40 cycles. Excellent cycling performances are noted with 100% of the theoretical capacity (170 mAh g–1) at 60 °C and 73.5% of the theoretical capacity (125 mAh g–1) at 25 °C.

Thermally and Oxidatively Stable Polymer Electrolyte for Lithium Batteries Enabled by Phthalate Plasticization

Hydrogenated nitrile butadiene rubber (HNBR) blended with lithium bis(trifluorosulfonyl)imide (LiTFSI) has been shown to be stable up to 5.3 V vs Li/Li+, making it a promising solid polymer electrolyte material for state-of-the-art high voltage cathodes. However, its relatively low room temperature ionic conductivity (3.6 × 10–8 S cm–1) limits its application in practical lithium battery cells. To address this issue, phthalate esters were selected as plasticizers to improve the conductivity. The low volatility, low flammability, outstanding thermal stability, and expected high oxidative stability of phthalates make them a compelling class of plasticizers for HNBR-based polymer electrolytes. A homologous series of dialkyl phthalate esters blended with HNBR/LiTFSI was studied. The oxidation potential of the plasticized HNBR/LiTFSI exceeded 5.2 V vs Li/Li+, demonstrating that phthalates do not substantially compromise the oxidative stability. The conductivity of the electrolyte (N/Li = 5) was 4.4 × 10–5 S cm...

Cover Feature: Single‐Ion Conducting Poly(Ethylene Oxide Carbonate) as Solid Polymer Electrolyte for Lithium Batteries (Batteries &amp; Supercaps 1/2020)

Cover Feature: Single‐Ion Conducting Poly(Ethylene Oxide Carbonate) as Solid Polymer Electrolyte for Lithium Batteries (Batteries &amp; Supercaps 1/2020)

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...

Single‐Ion Conducting Poly(Ethylene Oxide Carbonate) as Solid Polymer Electrolyte for Lithium Batteries

AbstractSingle‐ion conducting polymer electrolytes (SIPE) have attracted a lot of interest for application in high energy density lithium metal batteries. SIPEs possess lithium transport numbers close to unity, which does not provoke concentration gradients and holds the promise of limiting lithium dendrite formation. In this article, we have optimized a single‐ion polymer incorporating the most successful chemical units in polymer electrolytes, such as ethylene oxide, carbonate, and a lithium sulfonimide. This single‐ion poly(ethylene oxide carbonate) copolymer was synthesized by polycondensation between polyethylene glycol, dimethyl carbonate, and a functional diol including the pendant sulfonamide anionic group and the lithium counter‐cation. By playing with the monomer stoichiometry, the crystallinity and ionic conductivity were optimized. The best copolymer showed high ionic conductivity values of 1.2×10−4 S cm−1 at 70 °C. Lithium interactions and mobility were studied by lithium‐pulsed field gradient, lithium diffusion, NMR relaxation time measurements, and FTIR‐ATR analysis. High lithium mobility is observed, which is due to the weakly coordinating chemical environment in the polymer and also that the sulfonamide in the SIPE adopts to a greater extent the cis conformation, which is known to promote lithium mobility. Finally, the performance of the singe‐ion conducting poly(ethylene oxide carbonate) was compared in lithium symmetric cells versus an analogous conventional salt in polymer electrolyte, showing improved performance in lithium plating and stripping.

Surface Reconstruction Limited Conductivity in Block‐Copolymer Li Battery Electrolytes

AbstractSolid polymer electrolytes for lithium batteries promise improvements in safety and energy density if their conductivity can be increased. Nanostructured block‐copolymer electrolytes specifically have the potential to provide both good ionic conductivity and good mechanical properties. This study shows that the previously neglected nanoscale composition of the polymer electrolyte close to the electrode surface has an important effect on impedance measurements, despite its negligible extent compared to the bulk electrolyte. Using standard stainless steel blocking electrodes, the impedance of lithium salt‐doped poly(isoprene‐b‐styrene‐b‐ethylene oxide) (ISO) exhibits a marked decrease upon thermal processing of the electrolyte. In contrast, covering the electrode surface with a low molecular weight poly(ethylene oxide) (PEO) brush results in higher and more reproducible conductivity values, which are insensitive to the thermal history of the device. A qualitative model of this effect is based on the hypothesis that ISO surface reconstruction at the different electrode surfaces leads to a change in the electrostatic double layer, affecting electrochemical impedance spectroscopy measurements. As a main result, PEO‐brush modification of electrode surfaces is beneficial for the robust electrolyte performance of PEO‐containing block‐copolymers and may be crucial for their accurate characterization and use in Li‐ion batteries.