A bilayer polymer electrolyte encompassing pyrrolidinium-based RTIL for binder-free silicon few-layer graphene nanocomposite anodes for Li-ion battery

A binder-free electrode made of polycrystalline carbon-coated silicon nanoparticles encapsulated in few-layer graphene flakes is coupled with a PEO-based crosslinked bilayer polymer electrolyte (BLPE). A soft polymer electrolyte layer enriched with a pyrrolidium-based ionic liquid (Pyr14TFSI) is deposited on top of the electrode and UV cured by an in situ process to achieve optimal interfacial contact. A hard layer consisting of a crosslinked PEO-based polymer electrolyte film with a lower amount of Pyr14TFSI is integrated with the electrode/electrolyte assembly to improve the self-standing and shape-retention abilities. Proof-of-concept lab-scale Si-C||Li-metal polymer cells demonstrate a reversible specific discharge capacity up to 1044 mAh gSi–1 at 80 °C, largely outperforming the one with Pyr14TFSI/LiTFSI liquid electrolyte under the same experimental condition. Our results highlight the beneficial effect of the crosslinked PEO-based polymer matrix on the cycling performance, despite the absence of any SEI-forming agent.