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 the oxide structure and ion-transport properties. Comparative synthesis using polymolybdate (ammonium heptamolybdate) and monomolybdate (sodium molybdate) precursors reveals a clear correlation between the 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.