High-Entropy Polymer Electrolytes Derived from Multivalent Polymeric Ligands for Solid-State Lithium Metal Batteries with Accelerated Li+ Transport.

Solid-state polymer-based electrolytes (SSPEs) exhibit great possibilities in realizing high-energy-density solid-state lithium metal batteries (SSLMBs). However, current SSPEs suffer from low ionic conductivity and unsatisfactory interfacial compatibility with metallic Li because of the high crystallinity of polymers and sluggish Li+ movement in SSPEs. Herein, differing from common strategies of copolymerization, a new strategy of constructing a high-entropy SSPE from multivariant polymeric ligands is proposed. As a protocol, poly(vinylidene fluoride-co-hexafluoropropylene) (PH) chains are grafted to the demoed polyethylene imine (PEI) with abundant -NH2 groups via a click-like reaction (HE-PEIgPHE). Compared to a PH-based SSPE, our HE-PEIgPHE shows a higher modulus (6.75 vs 5.18 MPa), a higher ionic conductivity (2.14 × 10-4 vs 1.03 × 10-4 S cm-1), and a higher Li+ transference number (0.55 vs 0.42). A Li|HE-PEIgPHE|Li cell exhibits a long lifetime (1500 h), and a Li|HE-PEIgPHE|LiFePO4 cell delivers an initial capacity of 160 mAh g-1 and a capacity retention of 98.7%, demonstrating the potential of our HE-PEIgPHE for the SSLMBs.

Polycarbonate-Based Solid-Polymer Electrolytes for Solid-State Sodium Batteries.

Solid-polymer electrolytes comprised of polypropylene carbonate (PPC) and varied sodium bis(fluorosulfonyl)imide (NaFSI) salt concentrations are investigated for implementation as a conductive solid polymer electrolyte into solid-state cathode composites utilizing a sodium-layered oxide active material. The ionic conductivity generally increases with NaFSI salt content, reaching ≈1 mS cm-1 at 80 °C at the highest salt concentration (PPC:NaFSI = 0.5:1). Through an all-in-one slurry casting method, Na2/3Ni1/3Mn2/3O2 cathode composites are fabricated in which the dispersed PPC electrolyte acts as the primary binder. Enabled by a bilayer polymer electrolyte system, cycling performance with the PPC cathode electrolyte is optimized with respect to salt concentration and anode material. The best cyclability is achieved with a moderate salt concentration electrolyte (PPC:NaFSI = 5:1), showcasing an initial capacity of 83 mA h g-1 with a remarkable 80% capacity retention after 150 cycles at C/5 rate and 60 °C. The superior performance of the lower salt concentration electrolyte is attributed to better electrochemical stability, as confirmed by linear sweep voltammetry and online electrochemical mass spectrometry measurements. These results underscore the potential of carbonate-based polymer electrolytes and the importance of balancing electrolyte conductivity and stability in cell design.

A Healable Quasi-Solid Polymer Electrolyte with Balanced Toughness and Ionic Conductivity.

Solid polymer electrolytes (SPEs) have garnered extensive attention as potential alternatives to traditional liquid electrolytes, primarily due to their prowess in curbing lithium dendrite formation and preventing electrolyte leaks. The quest for SPEs that are both mechanically robust and exhibit superior ionic conductivity has been vigorous. However, achieving a harmonious balance between these two attributes remains a significant challenge. In this study, we introduce a novel quasi-solid electrolyte, ingeniously crafted from a poly(urethane-urea) network, enriched with lithium salts and plasticizers. This innovative composition not only boasts remarkable toughness but also ensures commendable ionic conductivity. Our post-gelation method yields gel polymer electrolytes that undergo rigorous evaluation, leading to an optimized version that stands out with its exceptional room-temperature ionic conductivity (2.94×10-4 S cm-1) and outstanding toughness (11.9 MJ m-3). Moreover, it demonstrates a broad electrochemical window (4.73 V), remarkable stability across a 600-hour cycle test, a high capacity retention exceeding 80 % after 100 cycles at 0.2 C, and a noteworthy self-healing capability. This quasi-solid polymer electrolyte emerges as a promising contender to replace current liquid electrolyte solutions.

Solid polymer electrolyte-based atomic switches: from materials to mechanisms and applications.

As miniaturization of semiconductor memory devices is reaching its physical and technological limits, there is a demand for memory technologies that operate on new principles. Atomic switches are nanoionic devices that show repeatable resistive switching between high-resistance and low-resistance states under bias voltage applications, based on the transport of metal ions and redox reactions in solids. Their essential structure consists of an ion conductor sandwiched between electrochemically active and inert electrodes. This review focuses on the resistive switching mechanism of atomic switches that utilize a solid polymer electrolyte (SPE) as the ion conductor. Owing to the superior properties of polymer materials such as mechanical flexibility, compatibility with various substrates, and low fabrication costs, SPE-based atomic switches are a promising candidate for the next-generation of volatile and nonvolatile memories. Herein, we describe their operating mechanisms and key factors for controlling the device performance with different polymer matrices. In particular, the effects of moisture absorption in the polymer matrix on the resistive switching behavior are addressed in detail. As potential applications, atomic switches with inkjet-printed SPE and quantum conductance behavior are described. SPE-based atomic switches also have great potential in use for neuromorphic devices. The development of these devices will be enhanced using nanoarchitectonics concepts, which integrate functional materials and devices.

This article reviews a series of works starting with the author's 2011 paper on solid polymer electrolyte-based atomic switches, and describes the current status and future prospects for this technology.

Covalent Organic Framework Enhanced Solid Polymer Electrolyte for Lithium Metal Batteries.

High ionic conductivity, outstanding mechanical stability, and a wide electrochemical window are the keys to the application of solid-state lithium metal batteries (LMBs). Due to their regular channels for ion transport and tailored functional groups, covalent organic frameworks (COFs) have been applied to solid electrolytes to improve their performance. Herein, we report a flexible polyethylene oxide-COF-LZU1 (abbreviated as PEO-COF) electrolyte membrane with a high lithium ion transference number and satisfactory mechanical strength, allowing for dendrite-free and long-time cycling for LMBs. Benefiting from the interaction between bis(triflfluoromethanesulonyl)imide anions (TFSI-) and aldehyde groups in COF-LZU1, the Li+ transference number of the PEO-5% COF-LZU1 electrolyte reached up to 0.43, much higher than that of neat PEO electrolyte (0.18). Orderly channels are conducive to the homogenous Li-+ deposition, thereby inhibiting the lithium dendrites. The assembled LiFePO4|PEO-5% COF-LZU1/Li cells delivered a discharge specific capacity of 146 mAh g-1 and displayed a capacity retention of 80% after 200 cycles at 0.1 C (60 °C). The Li/Li symmetrical cells of the PEO-5% COF-LZU1 electrolyte presented a longer working stability at different current densities compared to that of the PEO electrolyte. Therefore, the enhanced comprehensive performance of the solid electrolyte shows potential application prospects for use in LMBs.

A Dual-Bond Crosslinking Strategy Enabling Resilient and Recyclable Electrolyte Elastomers for Solid-State Lithium Metal Batteries.

Elastomeric solid polymer electrolytes (SPEs) are highly promising to address the solid-solid-interface issues of solid-state lithium metal batteries (LMBs), but compromises have to be made to balance the intrinsic trade-offs among their conductive, resilient and recyclable properties. Here, we propose a dual-bond crosslinking strategy for SPEs to realize simultaneously high ionic conductivity, elastic resilience and recyclability. An elastomeric SPE is therefore designed with hemiaminal dynamic covalent networks and Li+-dissociation co-polymer chains, where the -C-N- bond maintains the load-bearing covalent network under stress but is chemically reversible through a non-spontaneous reaction, the weaker intramolecular hydrogen bond is mechanically reversible, and the soft chains endow the rapid ion conduction. With this delicate structure, the optimized SPE elastomer achieves high elastic resilience without loading-unloading hysteresis, outstanding ionic conductivity of 0.2 mS cm-1 (25 °C) and chemical recyclability. Then, exceptional room-temperature performances are obtained for repeated Li plating/stripping tests, and stable cycling of LMBs with either LiFePO4 or 4.3 V-class LiFe0.2Mn0.8PO4 cathode. Furthermore, the recycled and reprocessed SPEs can be circularly reused in LMBs without significant performance degradation. Our findings provide an inspiring design principle for SPEs to address the solid-solid-interface and sustainability challenges of solid-state LMBs.

Deciphering and Integrating Functionalized Side Chains for High Ion-Conductive Elastic Ternary Copolymer Solid-State Electrolytes for Safe Lithium Metal Batteries.

A critical challenge in solid polymer lithium batteries is developing a polymer matrix that can harmonize ionic transportation, electrochemical stability, and mechanical durability. We introduce a novel polymer matrix design by deciphering the structure-function relationships of polymer side chains. Leveraging the molecular orbital-polarity-spatial freedom design strategy, a high ion-conductive hyperelastic ternary copolymer electrolyte (CPE) is synthesized, incorporating three functionalized side chains of poly-2,2,2-Trifluoroethyl acrylate (PTFEA), poly(vinylene carbonate) (PVC), and polyethylene glycol monomethyl ether acrylate (PEGMEA). It is revealed that fluorine-rich side chain (PTFEA) contributes to improved stability and interfacial compatibility; the highly polar side chain (PVC) facilitates the efficient dissociation and migration of ions; the flexible side chain (PEGMEA) with high spatial freedom promotes segmental motion and interchain ion exchanges. The resulting CPE demonstrates an ionic conductivity of 2.19×10-3 S cm-1 (30 °C), oxidation resistance voltage of 4.97 V, excellent elasticity (2700 %), and non-flammability. The outer elastic CPE and the inner organic-inorganic hybrid SEI buffer intense volume fluctuation and enable uniform Li+ deposition. As a result, symmetric Li cells realize a high CCD of 2.55 mA cm-2 and the CPE-based Li||NCM811 full cell exhibits a high-capacity retention (~90 %, 0.5 C) after 200 cycles.

Design of Quasi-Metal-Organic Frameworks for Solid Polymer Electrolytes Enabling an Ultra-Stable Interface with Li Metal Anode.

Solid polymer electrolytes (SPEs) are crucial in the development of lithium metal batteries. Recently, metal-organic frameworks (MOFs) with open metal sites (OMSs) have shown promise as solid fillers to improve the performance of SPEs. However, the number of OMS-containing MOFs is quite limited, comprising less than 5% of the total MOFs. When considering yield, cost, and processability, the commonly used OMS-containing MOFs are no more than 10 types, causing great limitations. Herein, we reported a simple and universal methodology that converted OMS-free MOFs to OMS-rich quasi-MOFs for developing high-performance SPEs, and explored the underlying mechanism. The "OMS-polymer" and "OMS-ion" interactions were investigated in detail to elucidate the role of quasi-MOFs on battery performance. It was found that quasi-MOFs, functioning as ion sieves, can effectively regulate ion migration, thus promoting uniform Li deposition and enabling an ultra-stable interface. As a result, the Li symmetric cell stably ran over 3000 h at 0.3 mA cm-2, while the full cell retained 85% of its initial capacity after 1500 cycles at 1.0 C. Finally, universal testing was performed using other MOFs, confirming the generalizability and effectiveness of our design concept.

Long-cycling and High-voltage Solid State Lithium Metal Batteries Enabled by Fluorinated and Crosslinked Polyether Electrolytes.

Solid-state lithium metal batteries (LMBs), constructed through the in situ fabrication of polymer electrolytes, are considered a critical strategy for the next-generation battery systems with high energy density and enhanced safety. However, the constrained oxidation stability of polymers, such as the extensively utilized polyethers, limits their applications in high-voltage batteries and further energy density improvements. Herein, an in situ fabricated fluorinated and crosslinked polyether-based gel polymer electrolyte, FGPE, is presented, exhibiting a high oxidation potential (5.1 V). The fluorinated polyether significantly improves compatibility with both lithium metal and high-voltage cathode, attributed to the electron-withdrawing -CF3 group and the generated LiF-rich electrolyte/electrode interphase. Consequently, the solid-state Li||LiNi0.6Co0.2Mn0.2O2 batteries employing FGPE demonstrate exceptional cycling performances of 1000 cycles with 78 % retention, representing one of the best results ever reported for polymer electrolytes. Moreover, FGPE enables batteries to operate at 4.7 V, realizing the highest operating voltage of polyether-based batteries to date. Notably, our designed in situ FGPE provides the solid-state batteries with exceptional cycling stability even at practical conditions, including high cathode loading (21 mg cm-2) and industry-level 18650-type cylindrical cells (1.3 Ah, 500 cycles). This work provides critical insights into the development of oxidation-stable polymer electrolytes and the advancement of practical high-voltage LMBs.

Anion-modulated Ion Conductor with Chain Conformational Transformation for stabilizing Interfacial Phase of High-Voltage Lithium Metal Batteries.

In solid-state lithium metal batteries (SSLMBs), the inhomogeneous electrolyte-electrode interphase layer aggravates the interfacial stability, leading to discontinuous interfacial ion/charge transport and continuous degradation of the electrolyte. Herein, we constructed an anion-modulated ionic conductor (AMIC) that enables in situ construction of electrolyte/electrode interphases for high-voltage SSLMBs by exploiting conformational transitions under multiple interactions between polymer and lithium salt anions. Anions modulate the decomposition behavior of supramolecular poly (vinylene carbonate) (PVC) at the electrode interface by changing the spatial conformation of the polymer chains, which further enhances ion transport and stabilizes the interfacial morphology. In addition, the AMIC weakens the "Li+-solvation" and increases Li+ vehicle sites, thereby enhancing the lithium-ion transport number (tLi +=~0.67). Consequently, Li || LiNi0.8Co0.1Mn0.1O2 cell maintains about 85 % capacity retention and Coulombic efficiency >99.8 % in 200 cycles at a charge cut-off voltage of 4.5 V. This study provides a new understanding of lithium salt anions regulating polymer chain segment behavior in the solid-state polymer electrolyte (SPE) and highlights the importance of the ion environment in the construction of interfacial phases and ionic conduction.

Optimizing the Microenvironment in Solid Polymer Electrolytes by Anion Vacancy Coupled with Carbon Dots.

The practical application of solid polymer electrolyte is hindered by the small transference number of Li+, low ionic conductivity and poor interfacial stability, which are seriously determined by the microenvironment in polymer electrolyte. The introduction of functional fillers is an effective solution to these problems. In this work, based on density functional theory (DFT) calculations, it is demonstrated that the anion vacancy of filler can anchor anions of lithium salt, thereby significantly increasing the transference number of Li+ in the electrolyte. Therefore, flower-like SnS2-based filler with abundant sulfur vacancies is prepared under the regulation of functionalized carbon dots (CDs). It is worth mentioning that the CDs dotted on the surface of SnS2 have rich organic functional groups, which can serve as the bridging agent to enhance the compatibility of filler and polymer, leading to superior mechanical performance and fast ion transport pathway. Additionally, the in situ formed Li2S/Li3N at the interface of Li metal and electrolyte facilitate the fast Li+ diffusion and uniform Li deposition, effectively mitigating the growth of lithium dendrites. As a result, the assembled lithium metal batteries exhibit excellent cycling stability, reflecting the superiority of the carbon dots derived vacancy-rich inorganic filler modification strategy.

A Dielectric MXene-Induced Self-Built Electric Field in Polymer Electrolyte Triggering Fast Lithium-Ion Transport and High-Voltage Cycling Stability.

Quasi-solid polymer electrolyte (QPE) lithium (Li)-metal battery holds significant promise in the application of high-energy-density batteries, yet it suffers from low ionic conductivity and poor oxidation stability. Herein, a novel self-built electric field (SBEF) strategy is proposed to enhance Li+ transportation and accelerate the degradation dynamics of carbon-fluorine bond cleavage in LiTFSI by optimizing the termination of MXene. Among them, the SBEF induced by dielectric Nb4C3F2 MXene effectively constructs highly conductive LiF-enriched SEI and CEI stable interfaces, moreover, enhances the electrochemical performance of the QPE. The related Li-ion transfer mechanism and dual-reinforced stable interface are thoroughly investigated using ab initio molecular dynamics, COMSOL, XPS depth profiling, and ToF-SIMS. This comprehensive approach results in a high conductivity of 1.34 mS cm-1, leading to a small polarization of approximately 25 mV for Li//Li symmetric cell after 6000 h. Furthermore, it enables a prolonged cycle life at a high voltage of up to 4.6 V. Overall, this work not only broadens the application of MXene for QPE but also inspires the great potential of the self-built electric field in QPE-based high-voltage batteries.

Mixed Ionically/Electronically Conductive Double-Phase Interface Enhanced Solid-State Charge Transfer for a High-Performance All-Solid-State Li-S Battery.

An all-solid-state lithium-sulfur battery (ASSLSB) is a promising candidate for post-Li-ion battery technologies with high energy densities and good safety performance. However, the intrinsic insulating nature of sulfur requires triple-phase contact with an ionic conductor and an electronic conductor for electrochemical reactions, which decreases the amount of active surface and lowers the charge-transfer efficiency. In this work, a double-phase interface constructed from a mixed ionic/electronic conductor is proposed to enhance the solid-state electrochemical reaction of sulfur. By employing lithium lanthanum titanium oxide/carbon (LLTO/C) nanofibers with mixed ionic/electronic conductivity, enhanced charge-transfer behavior is realized at the sulfur-LLTO/C double-phase interface, compared to the traditional triple-phase interface. As a result, high sulfur utilization and excellent rate performance are achieved. And the facilitated charge transfer shows great potential to lower the operating temperature and improve the sulfur content for practical applications of ASSLSBs. Cycle performance is also enhanced due to the suppressed shuttle effect of polysulfides by the incorporation of the LLTO/C nanofibers.

Low-Cost, High-Strength Cellulose-based Quasi-Solid Polymer Electrolyte for Solid-State Lithium-Metal Batteries.

Solid-state lithium-metal batteries are considered as the next generation of high-energy-density batteries. However, their solid electrolytes suffer from low ionic conductivity, poor interface performance, and high production costs, restricting their commercial application. Herein, a low-cost cellulose acetate-based quasi-solid composite polymer electrolyte (C-CLA QPE) was developed with a high Li+ transference number ( t L i + ${{t}_{{{\rm L}{\rm i}}^{+}}}$ ) of 0.85 and excellent interface stability. The prepared LiFePO4 (LFP)|C-CLA QPE|Li batteries exhibited excellent cycle performance with a capacity retention of 97.7 % after 1200 cycles at 1 C and 25 °C. The experimental results and Density Function Theory (DFT) simulation revealed that the partially esterified side groups in the CLA matrix contribute to the migration of Li+ and enhance electrochemical stability. This work provides a promising strategy for fabricating cost-effective, stable polymer electrolytes for solid-state lithium batteries.

Influencing Factors on Li-ion Conductivity and Interfacial Stability of Solid Polymer Electrolytes, Exampled by Polycarbonates, Polyoxalates and Polymalonates.

The application of solid polymer electrolytes (SPEs) in all-solid-state(ASS) batteries is hindered by lower Li+ -conductivity and narrower electrochemical window. Here, three families of ester-based F-modified SPEs of poly-carbonate (PCE), poly-oxalate (POE) and poly-malonate (PME) were investigated. The Li+ -conductivity of these SPEs prepared from pentanediol are all higher than the counterparts made of butanediol, owing to the enhanced asymmetry and flexibility. Because of stronger chelating coordination with Li+ , the Li+ -conductivity of PME and POE is around 10 and 5 times of PCE. The trifluoroacetyl-units are observed more effective than -O-CH2 -CF2 -CF2 -CH2 -O- during the in situ passivation of Li-metal. Using trifluoroacetyl terminated POE and PCE as SPE, the interfaces with Li-metal and high-voltage-cathode are stabilized simultaneously, endowing stable cycling of ASS Li/LiNi0.6 Co0.2 Mn0.2 O2 (NCM622) cells. Owing to an enol isomerization of malonate, the cycling stability of Li/PME/NCM622 is deteriorated, which is recovered with the introduce of dimethyl-group in malonate and the suppression of enol isomerization. The coordinating capability with Li+ , molecular asymmetry and existing modes of elemental F, are all critical for the molecular design of SPEs.

Promotion of Interface Fusion of Solid Polymer Electrolyte and Cathode by Ultrasonic Vibration.

All-solid-state polymer lithium batteries have good safety, stability, and high energy densities and are employed in wireless sensors. However, the solid contact between the polymer electrolyte and the cathode leads to high interface resistance, limiting the broad application of solid-state lithium batteries. This paper proposes an ultrasonic fusion method to reduce the interface resistance between the polymer electrolyte and the cathode. The method applied a high-frequency ultrasonic vibration technique to impact the polymer electrolyte/cathode structure, melting the electrolyte at the interface and thus generating good contact at the interface. The experimental results showed that the ultrasonic fusion method decreased the interface resistance between the polymer electrolyte and the cathode by 96.2%. During the ultrasonic fusion process, high-frequency ultrasonic vibrations generated high temperatures at the interface, and the polymer electrolyte became molten, improving the contact between the electrolyte and the cathode. The ultrasonic fusion method eliminated the gaps at the interface, and the interface became more compact. Furthermore, ultrasonic vibrations made the molten electrolyte fill the holes in the cathode, and the contact area was enhanced, providing more Li+ ions transmission paths.

Flame-Retardant ADP/PEO Solid Polymer Electrolyte for Dendrite-Free and Long-Life Lithium Battery by Generating Al, P-rich SEI Layer.

The poly(ethylene oxide) solid polymer electrolyte (PEO SPE) has recently received much attention, however, the organic components in the SPE are still flammable. In this paper, we find that the high efficiency halogen-free aluminum (Al) diethyl hypophosphite flame retardant (ADP) is effective in reducing the flammability of PEO SPE. The SEI layer containing Al and phosphorus (P) inhibits the growth of lithium dendrite and enhances the cycle life of the battery. The capacity of a LiFePO4/SPE/Li battery containing ADP is still 123.2 mAh g-1 at 1.0 C and the Coulombic efficiency is as high as 99.95% after 1000 cycles (60 °C). At the same time, Al, P-rich SEI can inhibit the growth of lithium dendrite and the cycle stability of the battery is further enhanced.

Effect of ZnO Nanofiller on Structural and Electrochemical Performance Improvement of Solid Polymer Electrolytes Based on Polyvinyl Alcohol-Cellulose Acetate-Potassium Carbonate Composites.

In this study, a solution casting method was used to prepare solid polymer electrolytes (SPEs) based on a polymer blend comprising polyvinyl alcohol (PVA), cellulose acetate (CA), and potassium carbonate (K2CO3) as a conducting salt, and zinc oxide nanoparticles (ZnO-NPs) as a nanofiller. The prepared electrolytes were physicochemically and electrochemically characterized, and their semi-crystalline nature was established using XRD and FESEM. The addition of ZnO to the polymer-salt combination resulted in a substantial increase in ionic conductivity, which was investigated using impedance analysis. The size of the semicircles in the Cole-Cole plots shrank as the amount of nanofiller increased, showing a decrease in bulk resistance that might be ascribed to an increase in ions due to the strong action of the ZnO-NPs. The sample with 10 wt % ZnO-NPs was found to produce the highest ionic conductivity, potential window, and lowest activation energy (Ea) of 3.70 × 10-3 Scm-1, 3.24 V, and 6.08 × 10-4 eV, respectively. The temperature-frequency dependence of conductivity was found to approximately follow the Arrhenius model, which established that the electrolytes in this study are thermally activated. Hence, it can be concluded that, based on the improved conductivity observed, SPEs based on a PVA-CA-K2CO3/ZnO-NPs composite could be applicable in all-solid-state energy storage devices.

SnF2 -Catalyzed Formation of Polymerized Dioxolane as Solid Electrolyte and its Thermal Decomposition Behavior.

Polymerized-dioxolane(P-DOL) is of potential as a solid-polymer-electrolyte(SPE) due to its high Li+ -conductivity, good compatibility with Li-metal and desired preparation method of in situ polymerization in cells. In this study, SnF2 was demonstrated not only to be an efficient catalyst for the polymerization of DOL at room temperature, but also an effective additive for improving interfacial wettability and suppressing dendrite through the reaction with Li-metal and the formation of LiF/Lix Sn based composite solid electrolyte interlayer(SEI). Using the SnF2 polymerized P-DOL containing 1 M LiTFSI as SPE(P-DOL-SPE), obviously denser Li-deposition was obtained, and the all-solid-state(ASS) Li/LiFePO4 cell delivered stable cycling over 350 cycles at 45 °C. At the same time, the irreversible decomposition of P-DOL-SPE into formaldehyde and small molecule epoxides are observed at 110 °C, which is even initiated at lower temperature of 40 °C under vacuum. This thermal decomposition of P-DOL-SPE in pouch cell causes huge volume swell, and therefore putting a strict limitation on the operating temperature window for the P-DOL based electrolytes.

Thermally Depolymerizable Polyether Electrolytes for Convenient and Low-Cost Recycling of LiTFSI.

Solid polymer electrolytes (SPEs) with LiTFSI (lithium bis(trifluoromethane sulfonimide)) are promising candidates for solid-state batteries, owing to their good interfacial contact with solid electrodes. Here, three copolymerized polyethers were prepared as SPEs, using the catalysts of SnF2 or SnF2 -LiPF6 . The thermal depolymerization of these polyethers was observed at elevated temperatures, which limits their operating temperature ranges. Once the catalyst is removed, the thermal degradation temperatures of these SPEs are raised by 30-55 °C, together with improved thermal performance in cells. For SPEs, the high price of LiTFSI is an obstacle for their large-scale application, and it's recycling is hindered by the strong interaction with polymers. By the thermal depolymerization of polyethers, LiTFSI can be easier reclaimed from above mentioned SPEs and even the commercial PEO(poly(ethylene-oxide)) based SPE in rates of 70-80 %, providing a low-cost strategy for the recycling of LiTFSI.