Li-ion nanorobots with enhanced mobility for fast-ion conducting polymer electrolytes†

Ion transport in known polymer electrolytes highly depends on the segmental motion of polymer chains and they have low ionic conductivity due to a single-ion transport pathway. Novel design paradigms are required to enhance the performance of polymer electrolytes beyond traditional systems. Here the role of an ultrasmall nanoparticle-assisted-migration is shown to significantly enhance the ionic conductivity of polyethylene oxide (PEO) polymer electrolytes. PEGylated nanoparticles with a size of much smaller than the gyration radius of the PEO chain diffuse rapidly within the PEO matrix and function as ion nanorobots for the transport of Li-ions. The ultrasmall nanoparticles also act as lubricants that further enhance the chain mobility of the bulk PEO backbone. The ultrasmall nanoparticle migration synergistically with accelerated segmental motion of the PEO form a dual-channel Li⁺ transport pathway, leading to an increase of the Li⁺ conductivity of the PEO-based electrolyte by three orders of magnitude. The electrolyte enables stable symmetric cell-cycling performance of >1800 h and long-term charge/discharge stability for 980 cycles when used for a Li|LiFePO₄ full battery at 50 °C. This work highlights the potential of activating hopping of nanoparticles in composite polymer electrolytes to construct high-performance polymer-based all-solid-state battery.