UV cross-linked highly stable polymer garnet composite electrolyte with improved interphase for lithium metal batteries

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Switzerland), 2024-09, Vol.968, p.118492, Article 118492
• Main Authors: Swathi, Pandurangan, Panneerselvam, Thamayanthi, Sreejith, O.V., Murugan, Ramaswamy, Ramaswamy, Arun Prasath
• Format: Article
• Language: English
• Subjects: Al-LLZO garnet; Cross-linking; High stability; Photo polymerization; Solid state electrolyte
• ISSN: 1572-6657
• DOI: 10.1016/j.jelechem.2024.118492

[Display omitted] •CPGCE synthesizedviathiol-ene click-reaction by photopolymerization.•CPGCE electrolyte exhibits Li+ conductivity of 4.4 × 10−4 S/cm, with a wide potential stability window of >4.2 V at 25 °C.•CPGCE provides higher stability and smooth Li-ion mobility with superior interfacial contact between the electrodes and electrolyte over 1000 cycles.•Full cell Li|CPGCE|LFP provides higher discharge capacity of 160–155 mAh g−1 of 96 % Coulombic efficiency. The next-generation electric vehicles heavily rely on high-energy–density lithium metal batteries with enhanced safety. Replacing liquid electrolytes with solid-state polymer electrolytes offers superior protection, high flexibility, and stability. However, inadequate ionic conductivity and poor compatibility at the interfaces with the electrodes hinder the practical application of solid-state electrolytes. In this work, we developed a polyethylene glycol-based, highly cross-linked polymer electrolyte with a garnet-type, fast Li+ conductive Li6.2Al0.24La3Zr2O12 (Al-LLZO) filler. The Al-LLZO filler was incorporated into a cross-linking functional polymeric matrix of polyethylene glycol diacrylate, pentaerythritol tetrakis (3-mercaptopropionate), and lithium perchlorate salt. The cross-linked polymer garnet composite electrolyte (CPGCE) was prepared via UV-induced photo-polymerization. The resulting CPGCE exhibits superior free-standing flexibility, a desired ionic conductivity of 4.4 × 10−4 S cm−1, and a wide potential window up to 4.2 V. The Li|CPGCE|Li symmetric cell underwent stripping and plating at varying current densities of 0.05 to 0.3 mA cm−2, displaying a low overpotential range from ±0.02 V to ±0.08 V over 500 cycles. Similarly, the as-cycled Li|CPGCE|Li showed excellent stripping and plating performance at 0.1 mA cm−2 for 500 cycles at 60 °C. The incorporation of the Al-LLZO nanofiller provided active sites with continuous Li+ conducting pathways, suppressing the growth of dead lithium dendrites. The Li|CPGCE|LiFePO₄ full cell exhibited a discharge capacity of 155 mAh g−1 at a rate of 0.1C, with a coulombic efficiency of 96 % over 50 cycles at 25 °C. This work offers a straightforward and convenient approach to creating highly durable polymer composite electrolytes with enhanced interfacial stability, advancing the implementation of all-solid-state lithium metal batteries.