Polyurethane–P2S5 composite-based solid-state electrolyte assists low polarization and high stability all-solid-state lithium-ion batteries

Abstract

Block copolymer electrolytes represented by polyurethane (PU) have become the forefront field of organic solid-state electrolytes for high-performance lithium-metal batteries due to their superb mechanical properties. However, due to the existence of mechanical hard segments, discontinuous ion transition at the electrolyte–electrode contact is inevitable, which leads to a series of problems such as terrible polarization phenomena, poor cycle stability and inadequate capacity retention. Here, we propose a new strategy to improve the chemical stability and interaction of electrolyte–electrode by modulating soft segments, which successfully reduces the polarization phenomenon. Then a new composite polymer solid electrolyte based on block copolymer PU (abbr. SPE) was prepared by ion-conduct segment modification using P₂S₅ with high lithium-ion affinity, and the ion conductivity of the SPE reached 7.4 × 10⁻⁴ S cm⁻¹ (25 °C) and 4.3 × 10⁻³ S cm⁻¹ (80 °C) respectively. The assembled LFP|SPE|Li displays a high specific capacity and stable charging/discharging platforms. Besides, an excellent retention capacity of 90% is obtained after 2000 cycles at 5C, and the lithium symmetric battery exhibits no significant polarization over 750 h. This work provides a viable strategy to suppress the polarization phenomenon to develop new block copolymer electrolytes with long cycle stability and high capacity retention.