Minimization of Ion–Solvent Clusters in Gel Electrolytes Containing Graphene Oxide Quantum Dots for Lithium-Ion Batteries

This study uses graphene oxide quantum dots (GOQDs) to enhance the Li⁺-ion mobility of a gel polymer electrolyte (GPE) for lithium-ion batteries (LIBs). The GPE comprises a framework of poly(acrylonitrile-co-vinylacetate) blended with poly(methyl methacrylate) and a salt LiPF₆ solvated in carbonate solvents. The GOQDs, which function as acceptors, are small (3−11 nm) and well dispersed in the polymer framework. The GOQDs suppress the formation of ion−solvent clusters and immobilize PF₆⁻ anions, affording the GPE a high ionic conductivity and a high Li⁺-ion transference number (0.77). When assembled into Li|electrolyte|LiFePO₄ batteries, the GPEs containing GOQDs preserve the battery capacity at high rates (up to 20 C) and exhibit 100% capacity retention after 500 charge−discharge cycles. Smaller GOQDs are more effective in GPE performance enhancement because of the higher dispersion of QDs. The minimization of both the ion−solvent clusters and degree of Li⁺-ion solvation in the GPEs with GOQDs results in even plating and stripping of the Li-metal anode; therefore, Li dendrite formation is suppressed during battery operation. This study demonstrates a strategy of using small GOQDs with tunable properties to effectively modulate ion−solvent coordination in GPEs and thus improve the performance and lifespan of LIBs.