Solid Polymer Electrolyte Research Articles

Coupled Ion-Conduction Mechanism for Enhanced Ionic Conductivity in Mg2B2O5 Nanowires Enabled Poly(ethylene oxide)-Based Quasi Solid State Electrolytes

Achieving room temperature high ionic conductivity of polymer solid state electrolytes equivalent to organic liquid electrolytes currently used in lithium ion batteries is a challenging task. The glass transition, crystallinity, free volume structure, salt dissociation, and ionic diffusion affect the ionic conductivity of polymer-based solid state electrolytes. In the present study, we report high-ionic conductivity (4.1 × 10–4 Scm–1) at room temperature for Mg2B2O5 nanowire-enabled solid state electrolytes of fully amorphous poly(ethylene oxide) (PEO). The Mg2B2O5 nanowires are synthesized using a single-step solid state reaction from inexpensive materials. The detailed investigation of the ion conduction mechanism using broadband dielectric spectroscopy confirms that the ionic conduction and segmental relaxations are a coupled phenomenon in these electrolytes, and segmental relaxation-mediated ionic diffusion is the primary ionic conduction mechanism. The enhancement in ionic conductivity on loading of Mg2B2O5 nanowires is attributed to the enhancement in the dissociated ionic concentration, ionic diffusion, and faster segmental relaxation due to interactions between the polymer, Li salt, and the nanowires. The smaller free volume size and enhanced free volume density of PEO in the electrolytes determined using positron annihilation lifetime spectroscopy and reduction in glass transition temperature determined from differential scanning calorimetry further confirm the role of modified chain packing and segmental relaxations in enhancement of ionic conductivity.

One dimensional CeO2 nanorods/poly(ethylene oxide) solid composite electrolyte for all-solid-state lithium-ion batteries

The research of poly(ethylene oxide) (PEO)-based solid composite electrolyte with high ionic conductivity and excellent interfacial stability is the key to the development of all-solid-state lithium-ion batteries (ASSLIBs). Herein, uniform nanorod structured CeO2 fillers were controllably synthesized by electrospinning, which were subsequently filled into PEO polymer to prepare CeO2/PEO solid composite electrolyte. The addition of CeO2 nanorods can reduce both the glass transition temperature and the melting point of PEO polymer, and also interact with PEO and lithium bis(trifluoromethanesulphonyl)imide (LITFSI) by Lewis acid–base reaction. Therefore, the solid composite electrolyte exhibits a high ionic conductivity of 4.52 × 10−4 S/cm, a wide electrochemical stability window of about 4.8 V, and a good interfacial stability with Li at 55 °C. Moreover, the LiFePO4/Li ASSLIB divulges the discharging specific capacity of 165, 162, 156 and 146 mA⋅h/g at 0.2, 0.5, 1 and 2 C, respectively, and achieves the capacity retention of 90.3% after 150 cycles at 0.5 C. Consequently, one dimensional CeO2 nanorods can be considered as an alternative filler for polymeric solid electrolyte.

Characterization and charge transport properties of sodium ion conducting PEO:NaBr solid polymer electrolyte films

AbstractThe study examines the effects of metal salt doping on polyethylene oxide (PEO) solid polymer electrolyte films. Sodium Bromide (NaBr) doped PEO films are prepared using a solution casting technique. The study finds that Na+ rom NaBr interacts with PEO's ether group (C–O–C) through complexation, as confirmed by Fourier Transform Infrared (FTIR) Spectroscopy. X‐ray diffraction analysis reveals that NaBr reduces PEO's degree of crystallinity. The addition of NaBr improves PEO's thermal stability, as shown by thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) images show smooth surface morphology of the polymer electrolyte films. The study also finds that the polymer electrolytes are non‐Debye in nature, based on dielectric studies. The highest ionic conductivity of 1.01 × 10−5 S/cm is observed for the 12.5 wt% NaBr doped PEO, with a low activation energy of 0.246 eV. Wagner's polarization technique is used to determine the charge carrier transport numbers, and the transient ionic current technique confirmed the presence of a single ionic species in the polymer electrolyte. Overall, the study suggests that 12.5 wt% NaBr doped PEO films have appropriate electrical properties for developing charge storage devices.

Operando Raman Spectroscopy for Evaluating Concentration Changes in Li- and Na-Based Solid Polymer Electrolytes

The solid polymer electrolytes (SPEs) can apply to all-solid-sate batteries using various cations as the carrier species. Herein, we performed operando Raman spectroscopy to evaluate the concentration changes with ionic transport in the Li- and Na-based SPEs composed of ether-based host polymer and MN(SO2CF3)2 (M = Li, Na; MTFSA), with the aim of extracting differences in behavior under electrochemical operation. In the [Li | Li-based SPE | Cu] cell, the integrated intensities of TFSA anions changed near the working electrode (WE) and counter electrode (CE) sides during cyclic voltammetry measurements, revealing changes in the anion concentration. Then, operando Raman spectroscopy was conducted for the [M | Li- or Na-based SPE | M (M = metallic Li or Na)] symmetric cells during chronoamperometry measurements. The cell using Li-based SPE exhibited increasing and decreasing integrated intensities for TFSA at the WE and CE sides, respectively, before reaching a steady state. In contrast, the integrated intensities of TFSA required a longer time to reach a steady state in the Na-based SPE system, suggesting that the solvation/desolvation of Na+ is more difficult during ionic transport. Overall, operando Raman spectroscopy contributed to elucidating the differences in ionic transport properties between Li- and Na-based SPEs during electrochemical processes.

Protonated chitosan nanostructures for enhancing ionic conductivity of solid-state electrolytes

Solid polymer electrolytes (SPEs) have aroused widespread attention for their high flexibility and good interface contact with electrode. However, the low ionic conductivity severely hinders their application in energy storage devices. Herein, a novel protonated nanostructure was synthesized through the reaction between PEO and Chitosan (Chi) and applied as fillers to form PEO/Chi composite solid-state electrolytes (PCCSEs). The fillers, which achieve nanization by the reaction with PEO, plays an important role in promoting the property of transporting Li+, due to the protonated amino (–NH3+) improving the dissociation of LiTFSI and the nanoscale size with high dispersity. Various characterizations and density functional theory (DFT) calculations were applied to reveal the enhanced Li+ transport mechanism in PCCSE. Owing to the unique design, PCCSE exhibits excellent ionic conductivity at room temperature (1.02 × 10−4 S cm−1) and the Li||SSEs||Li symmetric cells and LFP||SSEs||Li batteries with PCCSE show great cycling stability. This strategy of taking full use of the cations in protonated Chi provides effective design guidance for promoting the Li+ transport in polymer-based electrolytes.

Impact of Fluorine‐Based Lithium Salts on SEI for All‐Solid‐State PEO‐Based Lithium Metal Batteries

AbstractLiF‐rich solid‐electrolyte‐interphase (SEI) can suppress the formation of lithium dendrites and promote the reversible operation of lithium metal batteries. Regulating the composition of naturally formed SEI is an effective strategy, while understanding the impact and role of fluorine (F)‐based Li‐salts on the SEI characteristics is unavailable. Herein, LiFSI, LiTFSI, and LiPFSI are selected to prepare solid polymer electrolytes (SPEs) with poly(ethylene oxide) and polyimide, investigating the effects of molecular size, F contents and chemical structures (F‐connecting bonds) of Li‐salts and revealing the formation of LiF in the SEI. It is shown that the F‐connecting bond is more significant than the molecular size and F element contents, and thus the performances of cells using LiPFSI are slightly better than LiTFSI and much better than LiFSI. The SPE containing LiPFSI can generate a high amount of LiF, and SPEs containing LiPFSI and LiTFSI can generate Li3N, while there is no Li3N production in the SEI for the SPE containing LiFSI. The preferential breakage bonds in LiPFSI are related to its position to Li anode, where Li‐metal as the anode is important in forming LiF, and consequently the LiPFSI reduction mechanism is proposed. This study will boost other energy storage systems beyond Li‐ion chemistries.

Engineering 3D Interpenetrated ZIF-8 Network in Poly(ethylene oxide) Composite Electrolyte for Fast Lithium-Ion Conduction and Effective Lithium-Dendrite Inhibition

A novel 3D ZIF-8 network-reinforced polyethylene oxide (PEO) composite polymer electrolyte (Z-C-PAN-PEO) is successfully built, in which the network with an interpenetrated structure is tactfully developed by in situ assembling ZIF-8 nanoparticles on electrospinning carboxylated polyacrylonitrile (C-PAN) nanofiber surfaces. ZIF-8 with high porosity and unsaturated open metal sites will act as the bridge between C-PAN nanofibers and the PEO matrix. It is proven that the selected ZIF-8 can play a significant role in facilitating Li+ conduction and transference by effectively interacting with the oxygen atoms of C–O–C to promote the segmental movement of PEO and immobilizing TFSI– anions to release more free Li+. The 3D interpenetrating structure of Z-C-PAN further enables the conduction channels more consecutive and long-ranged, endowing the Z-C-PAN-PEO electrolyte with an optimum ionic conductivity of 4.39 × 10–4 S cm–1 and a boosted Li+ transference number of 0.42 at 60 °C. Other improvements occurring in the reinforced electrolytes are the broaden electrochemical stability window of ∼4.9 V and sufficient mechanical strength. Consequently, the stable Li-plating/stripping for 1000 cycles at 0.1 mA cm–1 witnesses the splendid compatibility against Li dendrite. The cycling performance of LiFePO4/Z-C-PAN-PEO/Li cells with a reversible capacity of 116.2 mAh g–1 after 600 cycles at 0.2 C guarantees the long-term running potential in lithium metal batteries. This study puts forward new insights in designing and exploiting the active role of MOFs for high-performance solid polymer electrolytes.

Photo-Electrical Tandem of Modulated Polyvinyl Alcohol Based Plasticized Solid Polymer Electrolyte Nanocomposite Films: Effect of Propylene Carbonate Contents

Plasticized solid polymeric electrolyte nanocomposites based on polyvinyl alcohol (PVA) incorporating Cs2CuO2 nanoparticles (NPs), electrolyte salt (LiClO4) and plasticizer (PC) were prepared via solution casting technique. The dynamic light-scattering histogram revealed that the prepared Cs2CuO2 NPs have a size in the range of 80-120 nm. The interaction between different components in PVA/Cs2CuO2/LiClO4-PC films (plasticized PVA-SPEs) were probed by FTIR, while the surface and structure were evaluated by SEM and XRD, which indicate to amorphous nature of plasticized PVA-SPEs. The thermal behavior of films was measured via TGA, where a partial decrease in the thermal stability of films was noticed with an increase of PC content in the PVA-SPEs. The highest conductivity achieved is 9.56X10-5 S/cm for PVA-SPEs containing 8wt% PC at 298K. The plasticized PVA-SPEs exhibited higher specific capacitance by two folds and photovoltaic efficiency by three folds compared to pure PVA matrix.

An initiator-free and solvent-free in-situ self-catalyzed crosslinked polymer electrolyte for all-solid-state lithium-metal batteries

Linear polymer (e.g. polyethylene oxide, PEO) based electrolytes have been widely studied due to their flexibility and relatively good contact against electrodes. However, the linear polymers are prone to crystallization at room temperature and melting at moderate temperature, restricting their application in lithium metal batteries. To address these problems, a self-catalyzed crosslinked polymer electrolyte (CPE) was designed and prepared by the reaction of poly (ethylene glycol diglycidyl ether) (PEGDGE) and polyoxypropylenediamine (PPO) with only the bistrifluoromethanesulfonimide lithium salt (LiTFSI) added and with no any initiators. LiTFSI catalyzed the reaction by reducing the activation energy to form a crosslinked network structure, which was identified by calculation, NMR and FTIR. The as-prepared CPE has high resilience and a low glass transition temperature (Tg = −60 °C). Meanwhile, the solvent-free in-situ polymerization technique has been adopted in the assembly of the CPE with electrodes to decrease the interfacial impedance greatly and improve the ionic conductivity to 2.05 × 10−5 S cm−1 and 2.55 × 10−4 S cm−1 at room temperature and 75 °C, respectively. As a result, the in-situ LiFeO4/CPE/Li battery exhibits outstanding thermal and electrochemical stability at 75 °C. Our work has proposed an initiator-free and solvent-free in-situ self-catalyzed strategy of preparing high performance crosslinked solid polymer electrolytes.

Liquid crystals as additives in solid polymer electrolytes for lithium metal batteries

The forefront of research for new electrolyte materials for tomorrow’s electrochemical energy storage technologies is based on thoroughly designed molecular architectures. Here, liquid crystals (LCs) mixed with poly(ethylene-oxide) (PEO) and lithium salts are proposed as solid polymer electrolytes (SPEs) for application in lithium-metal batteries. The PEO matrix comprises the LC, which gives orientational properties, whereas the PEO chains with lithium salts are responsible for the ionic conductivity. N-(4-Methoxybenzylidene)-4-butylaniline (MBBA) is used as proof-of-concept and new LC molecules are developed for further research. Ionic conductivities (7·10–4 S·cm−1 at 40 °C) up to three times higher than the reference without LC are achieved. In addition, the SPEs are characterized electrochemically, thermally and by polarized optical microscope demonstrating the preservation of the liquid crystalline behavior even after mixing with PEO and lithium salts.Graphical abstract

Single-Ion Polymer Electrolyte Based on Lithium-Rich Imidazole Anionic Porous Aromatic Framework for High Performance Lithium-Ion Batteries.

The low ionic conductivity and Li+ transference number ( ) of solid polymer electrolytes (SPEs) seriously hinder their application in lithium-ion batteries (LIBs). In this study, a novel single-ion lithium-rich imidazole anionic porous aromatic framework (PAF-220-Li) is designed. The abundant pores in PAF-220-Li are conducive to the Li+ transfer. Imidazole anion haslow binding force with Li+ . The conjugation of imidazole and benzene ring can further reduce the binding energy between Li+ and anions. Thus, only Li+ moved freely in the SPEs, remarkably reducing the concentration polarization and inhibiting lithium dendrite growth. PAF-220-quasi-solid polymer electrolyte (PAF-220-QSPE) is prepared through solution casting of Bis(trifluoromethane)sulfonimide lithium (LiTFSI) infused PAF-220-Li and Poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP), and possessed excellent electrochemical performance. The electrochemical property are further improved by preparing all-solid polymer electrolyte (PAF-220-ASPE) via pressing-disc method, which has a high Li+ conductivity of 0.501mScm-1 and of 0.93. The discharge specific capacity at 0.2C of Li//PAF-220-ASPE//LFP reached 164mAhg-1 , and the capacity retention rate is 90% after 180 cycles. This study provided a promising strategy for SPE with single-ion PAFs to achieve high-performance solid-state LIBs.

Self-healing polymer electrolytes with dynamic-covalent borate for solid-state lithium metal batteries

Developing a solid polymer electrolyte (SPE) combining superior interface stability with high ionic conductivity is still a challenge in the energy storage field. Herein, a series of novel self-healing solid polymer electrolytes were prepared by free radical photopolymerization with poly(ethylene glycol) methyl ether methacrylate and monomers containing borate. The reversible reaction induced by interesterification of borate ester endows the polymer electrolytes with excellent self-healing ability. The comb-like structure based on flexible poly(ethylene glycol) provides an amorphous state, which is conducive to lithium-ion transport. Further benefiting from the strong interaction between electron capture groups and anions of electrolyte salts, the borate-containing comb-shaped solid polymer electrolytes (PPBSPE) films display optimal ionic conductivity of 0.272 mS cm−1 at 60 °C, satisfactory transfer number for lithium ion, wide working voltage window, and remarkable stability towards lithium metal. The initial discharge capacities of the cell based on PPBSPE reach 156.2 mAh g−1 at a current rate of 0.1C, and high Coulombic efficiency (CE) of 99.4 %. This enhancement is due to the introduction of borate to the comb-shaped polymer, which is beneficial to form a more suitable electrolyte that can stabilize and improve the performance of lithium metal batteries.

A critical review on composite solid electrolytes for lithium batteries: Design strategies and interface engineering

The rapid development of new energy vehicles and 5G communication technologies has led to higher demands for the safety, energy density, and cycle performance of lithium-ion batteries as power sources. However, the currently used liquid carbonate compounds in commercial lithium-ion battery electrolytes pose potential safety hazards such as leakage, swelling, corrosion, and flammability. Solid electrolytes can be used to mitigate these risks and create a safer lithium battery. Furthermore, high-energy density can be achieved by using solid electrolytes along with high-voltage cathode and metal lithium anode. Two types of solid electrolytes are generally used: inorganic solid electrolytes and polymer solid electrolytes. Inorganic solid electrolytes have high ionic conductivity, electrochemical stability window, and mechanical strength, but suffer from large solid/solid contact resistance between the electrode and electrolyte. Polymer solid electrolytes have good flexibility, processability, and contact interface properties, but low room temperature ionic conductivity, necessitating operation at elevated temperatures. Composite solid electrolytes (CSEs) are a promising alternative because they offer light weight and flexibility, like polymers, as well as the strength and stability of inorganic electrolytes. This paper presents a comprehensive review of recent advances in CSEs to help researchers optimize CSE composition and interactions for practical applications. It covers the development history of solid-state electrolytes, CSE properties with respect to nanofillers, morphology, and polymer types, and also discusses the lithium-ion transport mechanism of the composite electrolyte, and the methods of engineering interfaces with the positive and negative electrodes. Overall, the paper aims to provide an outlook on the potential applications of CSEs in solid-state lithium batteries, and to inspire further research aimed at the development of more systematic optimization strategies for CSEs.

Cycling of block copolymer composites with lithium-conducting ceramic nanoparticles.

Solid polymer and perovskite-type ceramic electrolytes have both shown promise in advancing solid-state lithium metal batteries. Despite their favorable interfacial stability against lithium metal, polymer electrolytes face issues due to their low ionic conductivity and poor mechanical strength. Highly conductive and mechanically robust ceramics, on the other hand, cannot physically remain in contact with redox-active particles that expand and contract during charge-discharge cycles unless excessive pressures are used. To overcome the disadvantages of each material, polymer-ceramic composites can be formed; however, depletion interactions will always lead to aggregation of the ceramic particles if a homopolymer above its melting temperature is used. In this study, we incorporate Li0.33La0.56TiO3 (LLTO) nanoparticles into a block copolymer, polystyrene-b-poly (ethylene oxide) (SEO), to develop a polymer-composite electrolyte (SEO-LLTO). TEMs of the same nanoparticles in polyethylene oxide (PEO) show highly aggregated particles whereas a significant fraction of the nanoparticles are dispersed within the PEO-rich lamellae of the SEO-LLTO electrolyte. We use synchrotron hard x-ray microtomography to study the cell failure and interfacial stability of SEO-LLTO in cycled lithium-lithium symmetric cells. Three-dimensional tomograms reveal the formation of large globular lithium structures in the vicinity of the LLTO aggregates. Encasing the SEO-LLTO between layers of SEO to form a "sandwich" electrolyte, we prevent direct contact of LLTO with lithium metal, which allows for the passage of seven-fold higher current densities without signatures of lithium deposition around LLTO. We posit that eliminating particle clustering and direct contact of LLTO and lithium metal through dry processing techniques is crucial to enabling composite electrolytes.

Effect of Salt Content and Operating Temperature on the Nitrogen Dioxide Gas Sensing Performance of Sodium-Ion Conducting Solid Polymer Electrolyte

Sodium-ion conducting solid polymer electrolyte (Na-SPE) films based on polyvinyl alcohol (PVA) with various weight percentages of sodium iodide (NaI) were prepared using the casting technique. The films’ structural, morphology and electrical conductivity were examined to understand the sensing mechanism of the as-prepared Na-SPE films. The X-ray diffraction (XRD) and atomic force microscopy (AFM) data, respectively, showed the amorphous and homogeneous granular structure of Na-SPE films due to the high dissociation of NaI in the PVA matrix for all concentrations. The changes in the FTIR vibrational modes of Na-SPEs provide evidence of interactions between cations and functional groups of the host matrix. The effect of salt content, operating temperature and gas concentration on the performance of the Na-SPE sensor towards NO2 were investigated. In contrast to the pure PVA film, which did not respond to NO2 gas at low concentrations, Na-SPE films exhibit higher sensitivity to NO2 gas with faster response and recovery times. At low NO2 gas concentration (50 ppm), a sample containing 20 wt.% of NaI exhibits the highest sensitivity at the operating temperature of 200 °C. In comparison, at a high NO2 gas concentration (550 ppm), a sample containing 40 wt.% of NaI exhibits a maximum sensitivity at 150 °C. These findings suggest that Na-SPE films would be suitable for gas sensor applications. HIGHLIGHTS Na-SPEs films based on PVA with various salt contents have been prepared using the casting method The Hall effect data confirm the n-type conductivity of the Na-SPEs Na-SPE structure exhibits high sensitivity towards NO2 with rapid response/recovery times SPE film has a maximum sensitivity of 127.3 % at low NO2 gas concentration and a maximum sensitivity of 126 % at high gas concentration These results imply that this compound would be suitable for environmental and industrial uses GRAPHICAL ABSTRACT

Electrode-electrolyte interface mediation via molecular anchoring for 4.7 V quasi-solid-state lithium metal batteries

Solid polymer electrolytes (SPEs), promising electrolyte candidates for lithium metal batteries (LMBs), still suffer from the great challenge of unstable solid-solid interface between the electrodes and SPEs. Herein, SPEs are modulated by trimethyl phosphate (TMP) molecular anchoring to reconstruct the Li+ solvation structure, satisfy the interfacial compatibility of electrolyte-electrode and further unlock ultra-high voltage quasi-solid-state lithium metal batteries. An ultra-long cycle life of over 9000 h is achieved in Li|Li symmetrical cell at 0.1 mA cm−2. Furthermore, multiple highly-sensitive characterization techniques together with molecular dynamics simulations were applied to demonstrate that the in-situ induced stable cathode-electrolyte interface (CEI) rich in LiF, LixPFyOz and organic hybrids is responsible for the structural integrity of Ni-rich cathodes at 4.7 V ultra-high voltage. More importantly, the 91.55% capacity retention after 300 cycles of NCM811|Li full cell can well satisfy the practical application of high-voltage quasi-solid-state Li-metal energy storage systems.

Siloxane-type single-ion conductors enable composite solid polymer electrolyte membranes with fast Li+ transporting networks for dendrite-proof lithium-metal batteries

Solid polymer electrolytes (SPEs) significantly improve the operational safety of lithium-metal batteries (LMBs) by replacing the flammable liquid electrolytes, but still suffer from key limitations including low ionic conductivities, inferior lithium-ion transference numbers (tLi+), and poor mechanical properties. Herein, a novel poly (ethylene oxide) (PEO)-based composite electrolyte, with a semi-interpenetrating polymer network, is fabricated via in-situ cross-linking siloxane-type single-ion conductors (SICs) in PEO SPEs by one-step sol–gel method, enabling they simultaneously achieve the enhanced electrochemical and physicochemical properties. Incorporating a thermodynamically compatible SIC network not only reduces the crystallization of PEO matrix while facilitating the segmental relaxation of polymer chains, but also contributes to dissociating Li-salt and forming a three-dimensional conducting network for fast Li-ion transport. Thus, the resulting composite SPEs exhibit higher ionic conductivities (1.10 × 10−5 S cm−1 at 25 °C and 1.41 × 10−4 S cm−1 at 60 °C), tLi+ (0.52), and electrochemical window stability (4. 59 V) than pure PEO SPEs. Furthermore, this stable SIC networks can also enhance the mechanical performance and thermal stability of the composite SPEs. Thanks to these merits, the composite SPEs show the significant feasibility to regulate Li deposition and suppress the growth of Li dendrites, affording excellent stability and compatibility with Li metal. As a result, the Li/Li symmetrical cells using the composite SPEs show excellent cycling performances without an evident polarization enlargement for more than 900 h. The LiFePO4/Li batteries also achieve a remarkable capacity of 132.8 mA g−1 at 1C and exhibit impressive cycling abilities with 91.9% retention over 250 cycles. This study provides a promising concept for developing advanced composite SPEs for potential application in solid-state dendrite-free LMBs.

Solid polymer electrolytes: Ion conduction mechanisms and enhancement strategies

Solid polymer electrolytes (SPEs) possess comprehensive advantages such as high flexibility, low interfacial resistance with the electrodes, excellent film-forming ability, and low price, however, their applications in solid-state batteries are mainly hindered by the insufficient ionic conductivity especially below the melting temperatures, etc. To improve the ion conduction capability and other properties, a variety of modification strategies have been exploited. In this review article, we scrutinize the structure characteristics and the ion transfer behaviors of the SPEs (and their composites) and then disclose the ion conduction mechanisms. The ion transport involves the ion hopping and the polymer segmental motion, and the improvement in the ionic conductivity is mainly attributed to the increase of the concentration and mobility of the charge carriers and the construction of fast-ion pathways. Furthermore, the recent advances on the modification strategies of the SPEs to enhance the ion conduction from copolymer structure design to lithium salt exploitation, additive engineering, and electrolyte micromorphology adjustion are summarized. This article intends to give a comprehensive, systemic, and profound understanding of the ion conduction and enhancement mechanisms of the SPEs for their viable applications in solid-state batteries with high safety and energy density.

A Review of the Relationship between Gel Polymer Electrolytes and Solid Electrolyte Interfaces in Lithium Metal Batteries.

Lithium metal batteries (LMBs) are a dazzling star in electrochemical energy storage thanks to their high energy density and low redox potential. However, LMBs have a deadly lithium dendrite problem. Among the various methods for inhibiting lithium dendrites, gel polymer electrolytes (GPEs) possess the advantages of good interfacial compatibility, similar ionic conductivity to liquid electrolytes, and better interfacial tension. In recent years, there have been many reviews of GPEs, but few papers discussed the relationship between GPEs and solid electrolyte interfaces (SEIs). In this review, the mechanisms and advantages of GPEs in inhibiting lithium dendrites are first reviewed. Then, the relationship between GPEs and SEIs is examined. In addition, the effects of GPE preparation methods, plasticizer selections, polymer substrates, and additives on the SEI layer are summarized. Finally, the challenges of using GPEs and SEIs in dendrite suppression are listed and a perspective on GPEs and SEIs is considered.

A fiber-reinforced solid polymer electrolyte by in situ polymerization for stable lithium metal batteries

A fiber-reinforced solid polymer electrolyte by in situ polymerization for stable lithium metal batteries