Green Polymer Electrolytes Based on Polycaprolactones for Solid-State High-Voltage Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Solid polymer electrolytes (SPEs) are crucial for developing high energy solid-state lithium metal batteries (LMBs).
• Achieving long-term stability and suppressing lithium dendrite formation remain key challenges for LMBs.

Purpose of the Study:

• To introduce novel, ecofriendly, cross-linked poly(ε-caprolactone) (PCL)-based star polymer electrolytes (xBt-PCL).
• To evaluate the performance and interfacial properties of these SPEs in solid-state LMBs with LiNi$_{0.6}$ Mn$_{0.2}$ Co$_{0.2}$ O$_{2}$ (NMC622) cathodes.

Main Methods:

• Synthesis of cross-linked PCL-based star polymer electrolytes (xBt-PCL).
• Electrochemical cycling of Li metal batteries using xBt-PCL and NMC622 composite cathodes.
• Characterization of lithium dendrite suppression using ⁷ Li solid-state NMR.
• Analysis of electrolyte-electrode interfacial properties with cathode impregnation (1.5 wt% PCL).

Main Results:

• The xBt-PCL electrolytes demonstrated robust cycling performance against NMC622 cathodes.
• Significant suppression of dendritic lithium deposits was confirmed by ⁷ Li solid-state NMR.
• Cells exhibited stable performance up to 500 cycles at 1C rate (60 °C) due to improved interfacial properties.

Conclusions:

• PCL-based star polymer electrolytes show high potential for high-voltage solid-state lithium metal batteries.
• The cross-linked structure and cathode impregnation enhance interfacial stability and suppress dendrites.
• These findings pave the way for safer and more durable solid-state battery technologies.