High-performance solid polymer electrolytes (SPEs) have long been desired for the next generation of lithium batteries. One of the most promising ways to improve the morphological and electrochemical properties of SPEs is the addition of fillers with specific nanostructures. However, the production of such fillers is generally expensive and requires complicated preparation procedures. Halloysite nanotubes (HNTs), with their tubular structure, resemble carbon nanotubes in terms of geometric features and can be obtained at a relatively low cost. Previously, we reported that the HNT poly(ethylene oxide) composite SPE possesses excellent electrochemical and mechanical properties and outstanding cycling performance for all-solid-state lithium sulfur batteries. However, the HNT/SPE was not effective for lithium iron phosphate (LFP) batteries. The compatibility between the electrodes and the electrolyte sharply decreased, and no decent cycling performance was achieved. Therefore, a modification was studied which involves a minor addition of LFP during the preparation procedure. With this modification, good ionic conductivity (9.23 × 10-5 S cm-1 at 25 °C) is achieved, and compatibility between the electrodes and the electrolyte is enhanced. At the same time, an electrochemical stability window of 5.14 V and lithium-ion transference number of 0.46 are found. All-solid-state LFP batteries possessing excellent cycling performance are further demonstrated.
Keywords: coin cell battery testing; halloysite nanotube; lithium ion conductivity; lithium iron phosphate; poly(ethylene oxide); solid polymer electrolyte.