New insights towards aging resistant lithium polymer batteries for wide temperature applications

A wide interest is mounting in the field of polymer electrolytes, due to their application in energy efficient devices such as rechargeable batteries, photo-electrochemical cells, electrochromic devices, fuel cells and super capacitors. Polymer electrolytes exhibit unique advantages such as mechanical integrity, wide variety of fabrication methods in desirable size and shape, possibility to fabricate an intimate electrode/electrolyte interface and adapt to a lightweight, leak proof construction, safety and economic packaging structure. In this communication, we offer a summary of our recent and most interesting results regarding the synthesis, physico-chemical and electrochemical characterization of solid polymer electrolytes (SPEs) based on different monomers/oligomers (methacrylic and/or ethylene oxide based) with specific amounts of lithium salt, plasticizers and/or fillers. Profoundly ion conducting (σ > 10–4 S cm–1 at 20 °C), electrochemically stable (> 5 V vs. Li), self-standing, robust and tack-free SPEs are successfully prepared via a rapid and easily up-scalable process including a light induced photo-polymerization step and/or by thermal polymerization. The crosslinking produced by UV irradiation allows the incorporation of higher amounts of tetraglyme and/or RTIL (e.g., imidazolium, pyrrolidinium) with lithium salt (based on TFSI– anion), leading to a material with remarkable morphological characteristics in terms of homogeneity and mechanical abusability under highly stressful conditions. The lab-scale Li-polymer cells assembled show stable charge/discharge characteristics without any capacity fading at C/5 current regime (> 130 mAh g–1 in LiFePO4/Li configuration and > 150 mAh g–1 in TiO2/Li configuration @ 20 °C exploiting tetraglyme). Noteworthy, the ability to resist the lithium dendrite nucleation and growth is demonstrated by means of galvanostatic polarization studies. The overall performance of the SPEs postulates the possibility of effective implementation in the next generation of safe, durable and high energy density secondary all-solid Li-ion as well as Li-metal polymer batteries working at ambient and/or sub-ambient temperatures.