Eutectic Solution Enables Powerful Click Reaction for In‐Situ Construction of Advanced Gel Electrolytes

Abstract

Thiol‐ene click reaction is an intriguing strategy for preparing polymer electrolytes due to its high activity, atom economy and less side reaction. However, the explosive reaction rate and the use of non‐electrolytic amine catalyst hamper its application in in‐situ batteries. Herein, a nitrogen‐containing eutectic solution is designed as both the catalyst of the thiol‐ene reaction and the plasticizer to in‐situ synthesize the gel polymer electrolytes, realizing a mild in‐situ gelation process and the preparation of high‐performance gel electrolytes. The obtained gel polymer electrolytes exhibit a high ionic conductivity of 4 × 10−4 S cm−1 and lithium‐ion transference number () of 0.51 at 60 °C. The as‐assembled Li/LiFePO4 (LFP) cell delivers a high initial discharge capacity of 155.9 mAh g−1, and a favorable cycling stability with the capacity retention of 82% after 800 cycles at 1 C is also obtained. In addition, this eutectic solution significantly improves the rate performance of the LFP cell with high specific capacity of 141.5 and 126.8 mAh g−1 at 5 C and 10 C, respectively, and the cell can steadily work at various charge–discharge rate for 200 cycles. This powerful and efficient strategy may provide a novel way for in‐situ preparing gel polymer electrolytes with desirable comprehensive performances.

In Situ Construction of Polymer Electrolytes with Dynamic Covalent Networks via Initiator-Free Thiol-Methacrylate Radical Polymerization

“…Although the overall performance of PEO-based electrolytes can be significantly enhanced by chemical modifications (such as copolymerization, grafting, and physical blending), the commercialization of PEs is still limited by their complex chemical preparation process, the addition of foreign compounds (such as initiators or catalysts), and the high solid–solid interface impedance. The in situ polymerization method can enhance battery performance by reducing interface resistance and simplifying synthesis procedures. − Recently, we successfully achieved in situ construction of block copolymers by selecting bifunctional chain transfer reagents, which significantly optimized the overall performance of batteries . Although small amounts of initiators or catalysts used during the preparation process of the PEs did not affect the cycling performance of the batteries, they may have an adverse effect when produced on a large scale.…”

“…To manufacture PEs via in situ polymerization, an appropriate polymerization rate and avoidance of extraneous components (initiators or catalysts) are essential. , As a versatile chemical toolbox, click chemistries, including azide–alkyne cycloaddition, Diels–Alder reaction, and thiol chemistries, have been widely applied in all disciplines of chemistry . Among them, the thiol–ene reaction is frequently utilized in the preparation of polymers due to its simplicity and effectiveness. ,, Generally, the thiol–ene reaction is either an initiator-induced radical reaction or an alkali-catalyzed Michael addition reaction. , However, in situ polymerization via the thiol–ene reaction inevitably requires a radical initiator or catalyst, which adversely affects the cycling stability of lithium-based batteries. , Meanwhile, the introduction of solvents is not conducive to the continuous assembly of batteries. Therefore, developing solvent-free in situ polymerization that can be autocatalyzed or self-initiated at ambient temperature is crucial for constructing high-performance PEs .…”

Amine-Acrylate Michael Addition: A Versatile Platform for Fabrication of Polymer Electrolytes with Varied Cross-Linked Networks

“…The high selectivity and mild reaction conditions of click chemistry have simplified the tedious process of organic synthesis. Among them, the Michael addition reaction becomes the typical click chemistry reaction, and it has a much longer history of development than most click chemistry reactions. − Especially, thiol-Michael addition has been widely used in the preparation of cross-linked polymer electrolytes. ,− Thiol-Michael addition has been able to be carried out in a solvent-free and moderate-temperature environment, making it an efficient click chemistry method, whereas the reaction rate and yield are mainly dependent on the strength and concentration of the base catalyst and the p K a of thiol.…”

Facile Fabrication of Polymer Electrolytes with Branched Structure via Deep Eutectic Electrolyte-Enabled In Situ Polymerizations

“…DEE is intriguing as the liquid component of GPEs because of its simple preparation, excellent ion-conduction capability, and nonflammability. 50 To optimize the electrochemical performance of the GPEs, a deep eutectic electrolyte was designed (Figure 2b), namely DEE 1 (SL/LiPF 6 = 5:1), and the GPE based on DEE 1 is abbreviated as GPE-SL. Transparent DEE with a lower melting point could be obtained by stirring the corresponding components at ambient temperature.…”

“…GPE-SL possessed good electrochemical stability, and no obvious oxidation current was observed before 5.1 V (Figure 3b), which is due to the introduction of SL and the formation of polymer networks during the in situ polymerization process. 50,55 Li|GPE-SL|LiFePO 4 batteries were then prepared through in situ lithium-salts-induced cationic polymerization and radical polymerization, and the Li|DEE 1 |LiFePO 4 cell was also assembled as the comparison. The theoretical capacity of the LiFePO 4 cathode used for C-rates calculation is 170 mAh g −1 .…”