Precursor-Engineered Prelithiation Strategy CaMoO₄ enhancing ion transport in Composite Solid Electrolytes for Flexible Interdigitated Micro-Supercapacitors

Abstract

Solid polymer electrolytes (SPEs) are often limited by low ionic conductivity and poor interfacial ion transport, which restrict their application in flexible solid-state supercapacitors. Here, we report a prelithiated calcium molybdate (Li–CaMoO₄)/PVDF-HFP composite electrolyte and demonstrate that engineering the molybdate precursor provides a powerful strategy to optimize both oxide structure and ion-transport properties. Comparative synthesis using polymolybdate (ammonium heptamolybdate) and monomolybdate (sodium molybdate) precursors reveals a clear correlation between precursor anion structure, filler crystallinity, lithium incorporation, and segmental polymer dynamics. The optimized polymolybdate-derived electrolyte (A-S2, 10 wt% Li–CaMoO₄) achieves an ionic conductivity of 1.2 × 10⁻³ S·cm⁻¹ and retains over 95% of its capacitance after 10,000 cycles. When assembled into an interdigitated micro-supercapacitor, it delivers an areal capacitance of 36.4 mF·cm⁻² while maintaining excellent mechanical flexibility. Dielectric spectroscopy, FTIR, and NMR analyses confirm that the ordered Li–CaMoO₄ framework enhances salt dissociation, reduces space-charge polarization, and promotes polymer segmental mobility. This work establishes precursor-directed oxide engineering as a scalable, mechanism-driven strategy for high-performance flexible solid-state supercapacitors.