Hybridizing polymer electrolyte with poly(ethylene glycol) grafted polymer-like quantum dots for all-solid-state lithium batteries

Enhanced Interfacial Contact and Lithium-Ion Transport in Ionic Liquid Polymer Electrolyte via In-Situ Electrolyte-Cathode Integration

Solid polymer electrolytes (SPEs) have attracted much attention due to their excellent flexibility, strong interfacial adhesion, and good processibility. However, the poor interfacial contact between the separate solid polymer electrolytes and electrodes leads to large interfacial impedance and, thus, hinders Li transport. In this work, an ionic liquid-modified comb-like crosslinked network composite solid-state electrolyte with an integrated electrolyte/cathode structure is prepared by in situ ultraviolet (UV) photopolymerization. Combining the enhanced interfacial contact and the introduction of ionic liquid, a continuous and fast Li+ transport channel at the electrolyte-cathode interface is established, ultimately enhancing the overall performance of solid-state lithium batteries. The composite solid electrolytes (CSEs) exhibit an ionic conductivity of 0.44 mS cm-1 at 60 °C. LiFePO4//Li cells deliver a high discharge capacity (154 mAh g-1 at 0.5 C) and cycling stability (with a retention rate of more than 80% at 0.5 C after 200 cycles) at 60 °C.

Enhanced electrochemical stability and ion transfer rate: A polymer/ceramic composite electrolyte for high-performance all-solid-state lithium-sulfur batteries

All-solid-state (ASS) lithium-sulfur (LiS) batteries utilizing composite polymer electrolytes (CPEs) represent a promising avenue in the domain of electric vehicles and large-scale energy storage systems, leveraging the combined benefits of polymer electrolytes (PEs) and ceramic electrolytes (CEs). However, the inherent weak interface compatibility between PEs and CEs often leads to phase separation, thereby impeding the transposition of Li+. In this study, the trimethoxy-[3-(2-methoxyethoxy)propyl]silane (TM-MES) is introduced as a chemical agent to form bonds with polyethylene oxide (PEO) and Li10GeP2S12 (LGPS), resulting in the development of a novel composite polymer electrolyte (CPETM-MES). This innovative approach mitigates phase separation between PEs and CEs while concurrently enhancing the protective capabilities of LGPS against decomposition at the interfaces of both the Li anode and sulfur cathode. Moreover, the CPETM-MES exhibits superior mechanical toughness, an expanded electrochemical window, and elevated ionic conductivity. In the symmetric cell, it demonstrates an extended operational lifespan exceeding 1800 h, and the current density can reach up to 1.05 mA/cm2. Furthermore, the initial discharge capacity of ASS LiS batteries utilizing CPETM-MES attains 1227 mAh/g and maintains a capacity of 904 mAh/g after 100 cycles. Notably, a high-energy-density of 2454 Wh/kg is achieved based on the sulfur cathode.

Polymer Engineering Enables High Linear Capacity Fiber Electrodes by Microenvironment Regulation

Unlike bulky and rigid traditional power systems, 1D fiber batteries possess appealing features such as flexibility and adaptability, which are promising for use in wearable electronic devices. However, the performance and energy density fiber batteries are limited by the contradiction between ionic transfer and robust structure of fiber electrodes. Herein, these problems are addressed via polymer engineering to regulate the microenvironment in electrodes, realizing high-linear-capacity thick fiber electrodes with excellent cycling performance. The porosity of the electrodes is regulated using polymer crosslink networks designed with various components, and lithium-ion transfer is optimized through ether-abundant polymer chains. Furthermore, reinforced covalent bonding with carbon nanotube networks is established based on the modified functional groups of polymer networks. The multiscale optimizations of the porous structure, ionic transportation, and covalent bonding network enhance the lithium-ion dynamics property and structural stability. Therefore, ultrahigh linear-capacity fiber electrodes (17.8 mAh m-1) can be fabricated on a large scale and exhibit excellent stability (92.8% after 800 cycles), demonstrating obvious superiority among the reported fiber electrodes. Moreover, this study highlights the high effectiveness of polymer regulation in fiber electrodes and offers new avenues for designing next-generation wearable energy-storage systems.

Imidazolium-Type Poly(ionic liquid) Endows the Composite Polymer Electrolyte Membrane with Excellent Interface Compatibility for All-Solid-State Lithium Metal Batteries

Developing a poly(ethylene oxide) (PEO)-based polymer electrolyte with high ionic conductivity and robust mechanical property is beneficial for real applications of all-solid-state lithium metal batteries (ASSLMBs). Herein, an excellent organic/inorganic interface compatibility of all-solid-state composite polymer electrolytes (CPEs) is achieved using a novel imidazolium-type poly(ionic liquid) with strong electrostatic interactions, providing insights into the achievement of highly stable CPEs. The key properties such as micromorphologies, thermal behavior, crystallinity, t_Li⁺, mechanical property, lithium anode surficial morphology, and electrochemical performance are systematically investigated. The combined experimental and density functional theory (DFT) simulation results exhibit that the strong electrostatic interaction and ion-dipole interaction cooperated to improve the compatibility of the CPE, with a high ionic conductivity of 1.46 × 10^-4 S cm^-1 at 40 °C and an incredible mechanical strain of 2000% for dendrite-free and highly stable all-solid-state LMBs. This work affords a promising strategy to accelerate the development of PEO-based polymer electrolytes for real applications in ASSLMBs.

Abundant Hydrogen Bonds Formed in a Urea-Based Gel Polymer Electrolyte Improve Interfacial Stability in Lithium Metal Batteries

As an emerging and potential replacement system for liquid electrolytes, polymer electrolytes (PEs) exhibit unique capacity in suppressing metal dendrite formation and leakage risks. However, the most used polymer matrix, including polyether, polyester, and polysiloxane, still cannot meet the practical demands for metal electrode compatibility and long lifespan. In this study, gel polymer electrolytes consisting of a polyurea network with abundant hydrogen bonds and deep eutectic electrolyte (DEE) are designed and prepared in-situ. The hydrogen bonding between polyurea chains and polyurea-DEE provides good interfacial stability between PEs and lithium metal. As a result, the assembled Li/LiFePO₄ cells based on this electrolyte deliver a long cycle life with 90 % retention after 500 cycles and 76.5 % retention after 1000 cycles at 1 C. In addition, the flexible design characteristics of polyurea structure permit easy operation for performance optimization by modulating the composition of hard and soft segments, and enhanced ionic conductivity and self-healing efficiency are obtained. This study provides a novel method for preparing advanced polymer electrolytes for lithium metal batteries.

Rearrangement of Ion Transport Path on Nano-Cross-linker for All-Solid-State Electrolyte with High Room Temperature Ionic Conductivity

The low room temperature ionic conductivity (RTσ) of polyethylene oxide (PEO)-based solid-state polymer electrolyte (SPE) severely restricts its application for lithium batteries. Herein, acrylamide (AM) has been introduced into the poly(ethylene glycol) methyl ether methacrylate-poly(ethylene glycol) diacrylate (P-P). The multiple hydrogen bonds of AM expand the original single lithium environment (Li···O-C) to three types (Li···O-C, Li···N-H, and Li···O═C), which accelerates the conduction of lithium ions. In addition, the double bond modification of nanosilica (═SiO₂) not only improves the mechanical properties but also brings a high-speed orderly vehicular transport mechanism. The multiple-lithium-ions environment is rearranged on the surface of the ═SiO₂ to play a more significant role, making the RTσ of SPE reach 2.6 × 10^-4 S cm^-1, and the Li-ion transfer number reaches 0.84. The results show that the assembled all-solid-state lithium-sulfur battery has a high initial discharge capacity of 707 mAh g^-1 at 30 °C when the sulfur loading is 4.3 mg cm^-2, good cycle stability (capacity retention rate of 89% after 100 cycles at 0.1 C), and excellent rate performance. This SPE with high RTσ, stable interface engineering, and broad potential window (5.1 V) is expected to be used in other lithium/lithium-ion batteries that require high-voltage tolerance.

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.