SnF2 -Catalyzed Formation of Polymerized Dioxolane as Solid Electrolyte and its Thermal Decomposition Behavior
Wei Li1, Jian Gao1, Huayang Tian1
1Beijing Advanced Innovation Center for Soft Matter Science and Engineering, State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing, 100029, China.
Angewandte Chemie (International Ed. in English)
|November 30, 2021
Summary
Tin(II) fluoride (SnF2) catalyzes solid-polymer-electrolyte polymerization and improves lithium-metal battery performance. However, P-DOL-SPE stability limits operating temperatures due to thermal decomposition.
Area of Science:
- Materials Science
- Electrochemistry
- Polymer Chemistry
Background:
- Polymerized-dioxolane (P-DOL) shows promise as a solid-polymer-electrolyte (SPE) for lithium-metal batteries due to its high ionic conductivity and compatibility with lithium metal.
- In situ polymerization offers a convenient method for preparing P-DOL-based SPEs within battery cells.
- Controlling the interface between the electrolyte and lithium metal is crucial for stable battery operation and dendrite suppression.
Purpose of the Study:
- To investigate the dual role of tin(II) fluoride (SnF2) as a catalyst for P-DOL polymerization and as an additive to enhance the performance of solid-state lithium batteries.
- To evaluate the impact of SnF2 on interfacial properties, dendrite suppression, and electrochemical cycling stability.
- To determine the thermal stability limitations of the SnF2-modified P-DOL SPE.
Main Methods:
- Room temperature polymerization of dioxolane (DOL) using SnF2 as a catalyst.
- Preparation of a solid-polymer-electrolyte (P-DOL-SPE) incorporating 1 M LiTFSI and SnF2.
- Fabrication and electrochemical testing of all-solid-state (ASS) Li/LiFePO4 cells.
- Analysis of interfacial layers (SEI) and thermal decomposition behavior of the P-DOL-SPE.
Main Results:
- SnF2 efficiently catalyzes DOL polymerization at room temperature and forms a LiF/LixSn composite SEI layer, improving interfacial wettability and suppressing lithium dendrites.
- The P-DOL-SPE with SnF2 enabled denser lithium deposition and stable cycling of ASS Li/LiFePO4 cells for over 350 cycles at 45°C.
- Irreversible decomposition of P-DOL-SPE was observed at 110°C, initiated at lower temperatures (40°C) under vacuum, leading to significant volume swell in pouch cells.
Conclusions:
- SnF2 is a highly effective additive for P-DOL-based solid-polymer-electrolytes, enhancing catalytic polymerization, interfacial stability, and electrochemical performance in solid-state lithium batteries.
- The formation of a composite SEI layer containing LiF and LixSn is key to the improved performance.
- Thermal decomposition of the P-DOL-SPE at elevated temperatures poses a significant limitation, restricting the operational temperature window for these electrolytes.
