Reducing the crystallinity of PEO-based composite electrolyte for high performance lithium batteries

Poly(ethylene oxide) (PEO) based polymer electrolytes show great potential as the high energy density, mass-producible, low cost and high safety in the application of all-solid-state lithium (Li)-ion batteries. However, the unsatisfied ionic conductivity due to the high crystallinity of the intrinsic PEO limits its application. In this paper, the composite PEO-based electrolytes with sandwich-like structure have been designed, and the maneuverable heat-assisted process and multi-phase composite in order to suppress the crystallinity of PEO matrix are researched systematically. It's confirmed that the ionic conductivity of composite solid-state polymer electrolytes (CSPEs) after a hot-press process (90 °C, 15 min) reaches 4.9 × 10−4 S cm−1 at 25 °C. The sandwich structure of CSPEs not only enhances the ionic conductivity over the PEO electrolyte by decreasing the degree of crystallinity, but also enhances the mechanical strength and electrochemical window. Solid-state Li-ion cells fabricated with the CSPEs exhibit excellent and stable cycle performance. The specific capacity of cells is 160 mA h g−1 at 0.2C, and the capacity retention rate is almost 100% after 110 cycles. The Li|CSPE|Li cells could survive steadily for over 1,800 h. In this work, the multi-phase sandwich structure and practical manufacturing heat-assisted methods for CSPEs result in the excellent ionic conductivity, high mechanic strength and low cost of mass production, which offer a guidance on the commercialization of high-performance PEO-based electrolytes.