Advancements in battery materials: bio-based and mineral fillers for next-generation solid polymer electrolytes

The state-of-the-art all-solid-state batteries are expected to surpass conventional flammable Li-ion batteries, offering high energy density and safety in an ultrathin and lightweight solvent-free polymeric electrolyte (SPE). Nevertheless, there is an urgent need to boost the room-temperature ionic conductivity and interfacial charge transport of the SPEs to approach practical all-solid-state devices. Accordingly, loading filler grains into SPEs has been well-documented as a versatile strategy, promoting the overall electrochemical performance. In this era, using natural resources to extract filler additives has attracted tremendous attention to curb fossil fuel dependency. Also, there is a growing preference for materials that impose minimal environmental harm, are sustainable, and exhibit environmentally friendly characteristics. Therefore, mineral and biobased fillers, as natural-based additives, are strong candidates to replace traditional petroleum-based synthetic materials. Herein, we conduct a systematic investigation into the ion-transport mechanisms and fundamental properties of the filler-loaded SPEs. Additionally, recent advances in SPE architectures through embedding mineral and biobased fillers, as well as their hybrid compositions, are focused. Finally, the downsides and future directions are highlighted to facilitate further development and research toward revitalizing rechargeable battery-related technology. Overall, efficient methods for modifying SPEs through the use of natural resource organic and inorganic fillers are discussed, and technological advancements and related challenges are emphasized. Following the provided rational solutions to overcome major obstacles faced by SPEs, we hope to meet the demands of a greener future.