Solvent-free synthesis of PEO/garnet composite electrolyte for high-safety all-solid-state lithium batteries

• Published in: Journal of alloys and compounds 2021-04, Vol.860, p.157915, Article 157915
• Main Authors: Zhuang, Hua, Ma, Wencheng, Xie, Jingwei, Liu, Xiaoyu, Li, Bobo, Jiang, Yong, Huang, Shoushuang, Chen, Zhiwen, Zhao, Bing
• Format: Article
• Language: English
• Subjects: All-solid-state batteries; Composite electrolyte; Electric potential; Electrolytes; Electrolytic cells; Elongation; Hot rolling; Interface stability; Ion currents; Li6.75La3Zr1.75Ta0.25O12; Light emitting diodes; Lithium; Lithium batteries; Mechanical properties; Membranes; Polyethylene oxide; Safety; Solid electrolytes; Solid state; Solvent-free method; Solvents; Voltage
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.157915

Solid electrolyte membrane plays a vital role in the application of all-solid-state batteries. In this paper, composite electrolyte membranes incorporating commercial submicron Li6.75La3Zr1.75Ta0.25O12 (LLZTO) are prepared by solvent-free hot rolling method. It is found that the addition of LLZTO to the PEO-LiTFSI-based electrolyte can effectively reduce the crystallinity of PEO, improve the ion conductivity, voltage window, mechanical properties and interfacial stability of the composite solid electrolyte membrane. The composite electrolyte membrane with the optimal LLZTO content of 10 wt% exhibits a maximum ionic conductivity of 3.03 × 10−4 S cm−1 at 55 °C and a maximum elongation break of 74.8%. And also, the lithium symmetric cell assembled with 10 wt% LLZTO membrane exhibits the lowest polarization voltage and the best cycle performance, which can be attributed to the enhanced mechanical properties of the membrane and the lower and stable interfacial resistance between the membrane and lithium metal. The all-solid-state LiFePO4/Li batterie delivers a high specific capacity of 155.8 mAh g−1 at 0.1C rate at 55 °C, and exhibits excellent cycle performance and rate performance. In addition, the pouch cells assembled with PEO-LiTFSI-10LLZTO composite electrolyte membrane can still maintain the pristine voltage of 3.39 V and power light-emitting diodes (LEDs) under harsh conditions such as cutting, showing an excellent safety performance. [Display omitted] •Solvent-free hot rolling method is used to prepare PEO/garnet composite electrolyte.•LLZTO reduces crystallinity of PEO and widens voltage window of the PEO-electrolyte.•10 wt% LLZTO membrane shows the highest Li+ conductivity and transference number.•LiFePO4/Li pouch cell exhibits excellent safety property after cutting and piercing.