Ultrahigh Li-ion conductive single-ion polymer electrolyte containing fluorinated polysulfonamide for quasi-solid-state Li-ion batteries

Abstract

With the rapid development of electronic devices and electric vehicles, the requirements for their safety issues and service stabilities have become more and more strict. Single-ion gel polymer electrolytes exhibit outstanding ion conduction, high safety, good flexibility and a lithium transference number close to unity, leading to extensive research. In this work, a flexible fluorinated polysulfonamide based single-ion polymer electrolyte (SIPE) was synthesized using lithium [(4-styrenesulfonyl)(fluorosulfonyl)imide] (LiSFSI), pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) and pentaerythritol tetraacrylate (PET4A) via one-step in situ photoinitiated thiol–ene click reaction in plasticizers, with electrospun poly(vinylidene fluoride) (PVDF) as the standing membrane. The influence of plasticizer content was investigated and the optimized electrolyte exhibits ultra-high ionic conductivity (5.81 × 10⁻³ S cm⁻¹ at 28 °C) and a high lithium transference number of 0.91, near to unity. This ionic conductivity is among the highest ionic conductivities exhibited by SIPEs reported to date. Its electrochemical stability window is up to 5.2 V. More importantly, Li/LiFePO₄ cells using the prepared SIPE as both the electrolyte and separator displayed high reversible capacity at room temperature. It also exhibits excellent long-term stability and reliability as it maintains a capacity of 140 mA h g⁻¹ at 0.2C rate even after 230 cycles without obvious decay at room temperature.