Construction and ionic transport properties of a PPC–AlF3 composite solid-state electrolyte for aluminum batteries

Abstract

With the rapid development of lithium-ion batteries, issues related to safety risks and resource limitations have become increasingly prominent, driving the need for alternative energy storage systems. Aluminum-based batteries have attracted significant attention due to the abundance of aluminum resources and their high theoretical capacity; however, the low Al3+ transport efficiency in solid electrolytes remains a critical bottleneck. In this work, a PPC–AlF3 composite solid-state electrolyte was fabricated using polypropylene carbonate (PPC) as the polymer matrix and aluminum fluoride (AlF3) as the inorganic additive via mechanical ball milling, thermal pressing, and annealing processes. The ionic transport behavior and electrochemical performance were systematically investigated. The results show that pure PPC exhibits negligible ionic conductivity, while the introduction of AlF3 significantly facilitates the formation of Al3+ transport pathways. The conductivity increases with AlF3 content and reaches a maximum value of 1.01×10−4 mS/cm at a PPC: AlF3 ratio of 1:0.27. Further increase of AlF3 leads to aggregation effects and a decline in conductivity. In addition, lower temperatures significantly increase internal resistance and degrade charge–discharge performance. These findings demonstrate that the PPC–AlF3 composite system holds promising potential as a solid-state electrolyte for aluminum battery applications.