Innovative single-ion conducting solid electrolytes for safe, high performing energy storage devices

The pressing demand for long-lasting, high-power portable electronics and the emerging large-scale diffusion of electric vehicles (EVs) and energy storage from renewable sources require batteries with lower cost and improved energy density, along with enhanced cycle life and safety. State of the art Li-ion batteries (LIBs) currently on the market contain liquid electrolytes, which makes it difficult to design flexible cells, being also hazardous in terms of leakage and flammability. Within this context, a variety of solid-state electrolytes (viz., polymeric, inorganic, composites thereof) have been investigated to date as, in principle, they enable extension of the operating temperature range of a device; this ensures higher safety even in the case of fire, together with high energy and power density, thus favouring the transition to all-solid-state batteries. In the field of polymer electrolytes, the development of innovative single-ion conductors has attracted increasing interest in recent years, mainly because of their intrinsic safety and peculiar chemical structure that can be tailored as desired to display unique properties, such as tLi+ ≈ 1. Nevertheless, their practical application is still limited by low ionic conductivity (σ, far below 10–5 S cm–1 at 25 °C). Starting from the previous experience in the development of single-ion conducting copolymers based on the specifically designed lithium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethylsulfonyl)imide anionic monomer, this work is focused on the challenging synthesis by RAFT of novel ionic monomer with polyethylene glycol (PEG) based side chains and block copolymers comprising polycarbonate units in the backbone chain. The development of new block copolymers with PEG pendant chains should impart high flexibility and enhanced Li+ ion transport, while the introduction of polycarbonate in the main chain concurrently improve the electrochemical stability window (ESW more than 5 V). It would result in solid-state single-ion conducting polymer electrolytes that meet the request of high ionic mobility for ambient temperature practical application, with the chance to exploit their safe use with high voltage cathodes thus enhancing the overall device energy density.