Cyanogroup‐Modified PEO‐Based Electrolytes Achieve High Free Al ³⁺ Concentration and Improve the Transport Dynamics in Solid‐State Aluminum‐Ion Batteries

Polymer-based solid electrolyte boasting ultra-high safety, energy density, mechanical strength and flexibility, attracting much attention in the field of battery applications. However, its widespread application is hindered by the low conductivity, insufficient aluminium salt dissociation, high crystallization degree, short service life, etc. To solve the above problems, a composite solid polymer electrolyte (SPE) design based on polyethylene oxide (PEO, Mw = 6 000 000) with AlCl₃·6H₂O as aluminum salt and butanedinitrile (SN) as plasticizer is proposed in this paper. The disorder and mobility of the PEO chains, conductivity, degree of aluminum salt dissociation, and service life are enhanced by the addition of plasticizer SN. Theoretical calculation demonstrates the formation of solvated sheath-like structure [SN…Al³⁺] has strong interactions with the polymer PEO, allowing rapid transport of Al³⁺ through the polymer segments. These results are also further verified by subsequent tests, which can reveal the Al³⁺ transport mechanism of room-temperature SPEs in a more reasonable way. Meanwhile, the relatively strong binding energy between PEO and SN can help to avoid the parasitic reaction between SN and Al, increase the service life of solid-state aluminium-ion batteries. Providing a promising solution for the design of solid-state battery electrolytes that can be applied at room temperature.