A novel Li+‐conducting polymer membrane gelled by fluorine‐free electrolyte solutions for Li‐ion batteries

Gel polymer electrolytes (GPEs), composed of poly(vinylidene fluoride) (PVdF), a ternary solvent of ethylene carbonate: propylene carbonate: dimethyl carbonate, and LiBOB, which are characterised by a novel composition with a fluorine‐free lithium salt, are here proposed. GPEs were firstly prepared through a solution casting procedure using the ternary carbonate solution as a solvent (named ex‐situ prepared membranes), and then activated by being immersed in a 0.7 M LiBOB‐carbonate solution. Fundamental characterizations, including thermal, spectroscopical, mechanical, and electrochemical analyses, were carried out and compared before and after the activation. GPEs, having the same composition, were also prepared by using a novel procedure (named in‐situ prepared membranes), involving the formation of PVdF membrane and its activation by the LiBOB electrolyte, as well as subsequent electrochemical characterizations, in the same T‐shape cell. Thus prepared lithium ion batteries, employing Sn‐C and LiFePO 4 electrodes, were demonstrated to exhibit a high capacity of 150 mAh g ‐1 through the course of cycling.