Researchers from Northeast Normal University have developed a composite solid electrolyte (CSE) membrane to enhance the conductivity of solid-state lithium-ion batteries. In their recent study published in the journal Polyoxometalates, they introduced a POM-based lithium salt, Li6P2Mo18O62 (LPM), into a solid-polymer electrolyte (SPE) composed of polyethylene oxide (PEO). This addition improved ion movement and conductivity. They also incorporated an ionic liquid (IL) to further enhance the composite electrolyte material.
Solid-state electrolytes (SSEs) are highly regarded for next-generation energy storage due to their thermal and electrochemical stability. However, SPEs, which offer flexibility and viscosity, suffer from low ionic conductivity, mechanical weakness, and poor thermal stability at room temperature.
In contrast, inorganic solid electrolytes like LPM typically exhibit high ionic conductivity. By combining them with SPEs to create composite polymer electrolytes, the researchers harnessed the strengths of both to optimize mechanical properties and boost ionic conductivity.
The study showed that electrolyte membranes with the right balance of LPM and IL achieved three times higher conductivity compared to those without IL. Similarly, composite membranes using polyvinylidene fluoride (PVDF) alongside PEO increased conductivity tenfold compared to LPM-IL membranes without PVDF. These composite membranes remained stable at 80°C for 12 hours.
The results demonstrate the potential of polyoxometalates as inorganic solid electrolytes. IL played a crucial role in enhancing the dissociation of lithium ions from LPM, thereby improving ionic conductivity. The incorporation of PVDF created a conductive network, further enhancing lithium ion movement.
The researchers believe their PEO-based composite membrane, featuring PVDF, POM-based lithium salt, and IL, offers a practical solution to enhance ionic conductivity in solid-state electrolytes for lithium-ion batteries. Their future goal is to improve polyoxometalates’ performance to develop superior solid-state lithium-ion batteries.