Strategies for improving ionic conductivity and mechanical stability of solid polymer electrolytes for lithium batteries via physical and chemical interlocking

Solid polymer electrolytes (SPEs) are essential for the advancement of high-energy density, safe, solid-state lithium batteries. However, traditional SPEs encounter difficulties such as inadequate ionic conductivity, poor mechanical stability, and high interfacial impedance. Incorporating inorganic fillers or polymer-reinforced structures can improve the electrochemical performance and physical qualities of the SPEs. Inorganic fillers frequently have compatibility issues with the polymer matrix and result in poor ionic conductivity due to their uneven distribution in the matrix. Conversely, continuous fiber-based three-dimensional frameworks, whether inorganic or polymeric, facilitate physical interlocking of the polymer matrix, limit filler aggregation, and improve ion transport, resulting in increased ionic conductivity and mechanical strength. Electrospinning is the most widely adopted approach for fabricating oriented fibrous frameworks with uniform thickness. Cross-linking also improves ionic conductivity by chemically interlocking the polymer matrix, inhibiting crystallization and allowing for steady battery performance across a wide temperature range. This review emphasizes the dual-interlocking strategies employed in SPEs, where electrospun fibrous networks provide physical interlocking and cross-linking offers chemical interlocking of the polymer matrices simultaneously. The synergy between fiber-based networks and cross-linking results in SPEs with balanced electro-chemo-mechanical properties which is crucial for the development of next-generation solid-state lithium batteries.