Epoxy-Based Interlocking Membranes for All Solid-State Lithium Ion Batteries: The Effects of Amine Curing Agents on Electrochemical Properties

Epoxy-based multifunctional solid polymer electrolytes for structural batteries and supercapacitors. a short review

The potential applications of epoxy-based solid polymer electrolytes are continually expanding because of their versatile characteristics. These characteristics include mechanical rigidity, nonvolatility, nonflammability, and electrochemical stability. However, it is worth noting that pure epoxy-based solid polymer electrolytes inherently exhibit lower ion transport capabilities when compared to traditional liquid electrolytes. Striking a balance between high mechanical integrity and superior ionic conductivity at room temperature poses a significant challenge. In light of this challenge, this review is dedicated to elucidating the fundamental concepts of epoxy-based solid polymer electrolytes. It will explore various preparation techniques, the incorporation of different nanomaterials into epoxy-based solid polymer electrolytes, and an evaluation of their multifunctional properties. This comprehensive evaluation will cover both mechanical and electrical properties with a specific focus on their potential applications in batteries and structural supercapacitors.

Crosslinked Gel Polymer Electrolyte from Trimethylolpropane Triglycidyl Ether by In Situ Polymerization for Lithium-Ion Batteries

Electrolytes play a critical role in battery performance. They are associated with an increased risk of safety issues. The main challenge faced by many researchers is how to balance the physical and electrical properties of electrolytes. Gel polymer electrolytes (GPEs) have received increasing attention due to their satisfactory properties of ionic conductivity, mechanical stability, and safety. Herein, we develop a gel network polymer electrolyte (GNPE) to address the challenge mentioned earlier. This GNPE was formed by tri-epoxide monomer and bis(fluorosulfonyl)imide lithium salt (LiFSI) via an in situ cationic polymerization under mild thermal conditions. The obtained GNPE exhibited a relatively high ionic conductivity (σ) of 2.63 × 10-4 S cm-1, lithium transference number (tLi+, 0.58) at room temperature (RT), and intimate electrode compatibility with LiFePO4 and graphite. The LiFePO4/GNPE/graphite battery also showed a promising cyclic performance at RT, e.g., a suitable discharge specific capacity of 127 mAh g-1 and a high Coulombic efficiency (>97%) after 100 cycles at 0.2 C. Moreover, electrolyte films showed good mechanical stability and formed the SEI layer on the graphite anode. This study provides a facile method for preparing epoxy-based electrolytes for high-performance lithium-ion batteries (LIBs).

Glycidyl Methacrylate-Based Copolymers as Healing Agents of Waterborne Polyurethanes

Self-healing materials and self-healing mechanisms are two topics that have attracted huge scientific interest in recent decades. Macromolecular chemistry can provide appropriately tailored functional polymers with desired healing properties. Herein, we report the incorporation of glycidyl methacrylate-based (GMA) copolymers in waterborne polyurethanes (WPUs) and the study of their potential healing ability. Two types of copolymers were synthesized, namely the hydrophobic P(BA-co-GMAy) copolymers of GMA with n-butyl acrylate (BA) and the amphiphilic copolymers P(PEGMA-co-GMAy) of GMA with a poly(ethylene glycol) methyl ether methacrylate (PEGMA) macromonomer. We demonstrate that the blending of these types of copolymers with two WPUs leads to homogenous composites. While the addition of P(BA-co-GMAy) in the WPUs leads to amorphous materials, the addition of P(PEGMA-co-GMAy) copolymers leads to hybrid composite systems varying from amorphous to semi-crystalline, depending on copolymer or blend composition. The healing efficiency of these copolymers was explored upon application of two external triggers (addition of water or heating). Promising healing results were exhibited by the final composites when water was used as a healing trigger.

Spiro-Twisted Benzoxazine Derivatives Bearing Nitrile Group for All-Solid-State Polymer Electrolytes in Lithium Batteries

In this study, two nitrile-functionalized spiro-twisted benzoxazine monomers, namely 2,2′-((6,6,6′,6′-tetramethyl-6,6′,7,7′-tetrahydro-2H,2′H-8,8′-spirobi[indeno[5,6-e][1,3]oxazin]-3,3′(4H,4′H)-diyl)bis(4,1-phenylene))diacetonitrile (TSBZBC) and 4,4′-(6,6,6′,6′-tetramethyl-6,6′,7,7′-tetrahydro-2H,2′H-8,8′-spirobi[indeno[5,6-e][1,3]oxazin]-3,3′(4H,4′H)-diyl)dibenzonitrile (TSBZBN) were successfully developed as cross-linkable precursors. In addition, the incorporation of the nitrile group by covalent bonding onto the crosslinked spiro-twisted molecular chains improve the miscibility of SPE membranes with lithium salts while maintaining good mechanical properties. Owing to the presence of a high fractional free volume of spiro-twisted matrix, the –CN groups would have more space for rotation and vibration to assist lithium migration, especially for the benzyl cyanide-containing SPE. When combined with poly (ethylene oxide) (PEO) electrolytes, a new type of CN-containing semi-interpenetrating polymer networks for solid polymer electrolytes (SPEs) were prepared. The PEO-TSBZBC and PEO-TSBZBN composite SPEs (with 20 wt% crosslinked structure in the polymer) are denoted as the BC20 and BN20, respectively. The BC20 sample exhibited an ionic conductivity (σ) of 3.23 × 10⁻⁴ S cm⁻¹ at 80 °C and a Li⁺ ion transference number of 0.187. The LiFePO₄ (LFP)|BC20|Li sample exhibited a satisfactory charge–discharge capacity of 163.6 mAh g⁻¹ at 0.1 C (with approximately 100% coulombic efficiency). Furthermore, the Li|BC20|Li cell was more stable during the Li plating/stripping process than the Li|BN20|Li and Li|PEO|Li samples. The Li|BC20|Li symmetric cell could be cycled continuously for more than 2700 h without short-circuiting. In addition, the specific capacity of the LFP|BC20|Li cell retained 87% of the original value after 50 cycles.