Polymerization-Initiator Engineering Enables High-Voltage-Stable Gel Polymer Electrolytes for Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Gel polymer electrolytes (GPEs) offer high ionic conductivity and good interfacial contact for lithium metal batteries (LMBs).
• Poly(1,3-dioxane) (PDOX)-based GPEs show promise for high-energy LMBs due to oxidative stability, but suffer from lithium dendrite growth.
• Lithium dendrite formation at the PDOX electrolyte/anode interface limits interfacial stability and battery lifespan.

Purpose of the Study:

• To develop a novel GPE for high-energy-density lithium metal batteries.
• To address the challenge of lithium dendrite growth in PDOX-based GPEs.
• To enhance the interfacial stability and cycling performance of LMBs.

Main Methods:

• In situ polymerization of 1,3-dioxane (DOX) initiated by indium trifluoromethanesulfonate (In(OTf)3).
• Formation of a robust solid electrolyte interphase (SEI) layer enriched with LiₓIn alloy and LiF.
• Fabrication and testing of Li||Li symmetric cells and Li||NCM523/NCM712 battery cells.

Main Results:

• The In(OTf)3 initiated PDOX GPE demonstrated stable operation for over 1600 hours at 1.0 mA cm⁻² in Li||Li symmetric cells.
• Li||NCM523 cells exhibited 82.5% capacity retention after 500 cycles at 1 C.
• An Ah-level Li||NCM712 pouch cell achieved an energy density of 402 Wh kg⁻¹ with 99.3% capacity retention over 100 cycles.

Conclusions:

• Indium trifluoromethanesulfonate acts as a bifunctional initiator, creating a stable, lithophilic, and Li⁺-conductive interface that suppresses dendrite growth.
• The developed PDOX-based GPE significantly improves the interfacial stability and long-term cycling performance of lithium metal batteries.
• This GPE shows considerable potential for practical applications in high-energy-density batteries.