Nanocomposite solid polymer electrolytes based on semi-interpenetrating hybrid polymer networks for high performance lithium metal batteries

Abstract

This research reports the synthesis of nanocomposite solid polymer electrolytes (ncSPEs) for solid state lithium metal batteries. These materials are composed of a controlled hybrid organic-inorganic network of glycidyl POSS® and Jeffamine® ED2003, in which linear high molecular weight poly (ethylene oxide) (PEO) chains are entangled to improve both mechanical and electrochemical properties of the ncSPE. Synthesis and preparation of self-standing membranes are achieved with a facile one-pot catalyst-free method with considerably reduced amount of organic solvent, which is a plus toward a future scale-up. We found that the component ratio plays a crucial role in ncSPEs’ performance as a simple variation (i.e. cross-linking degree) is sufficient to completely change the electrochemical behavior of the solid state cell. For instance, increasing POSS® amount guarantees better resistance to lithium dendrites penetration, better electro-oxidation stability, and significantly extends cycle life in Li/ncSPE/LiFePO4 solid state cells. Furthermore, besides improving cell performance at higher C-rate of Li/LiFePO4 cells, this PEO-based ncSPE gives better response than reference PEO-LiTFSI electrolyte in high voltage Li/LiNi0.6Mn0.2Co0.2O2 cells with up to 10 cycles at 60 °C with discharge capacity retention above 80%. Despite the poor performance, to the best of our knowledge, this electrolyte is one of the few examples of PEO-based solid polymer electrolytes being capable of cycling with high voltage cathodes.