Mixed Ionic–Electronic Conduction in Binary Polymer Nanoparticle Assemblies

Abstract Polymer‐based mixed ionic–electronic conductors (MIECs) are desired for both bulk and interfacial materials in next‐generation energy storage and electronic devices. Polymer‐based MIECs contain two principal components, one for electronic conduction and the other for ionic conduction. The central problem is the lack of a general approach to control the molecular packing and morphology of the constituent components that will afford the ability to easily tune transport properties. This study demonstrates the efficacy of a modular method based on polymer nanoparticle self‐assembly to achieve MIECs with tunable conductivity. This work uses poly(3‐hexylthiophene) nanoparticles as the electronic conductor and lithium ion‐doped poly(vinylpyridine) nanoparticles as the ionic conductors. AC impedance spectroscopic studies show that nanoparticle–nanoparticle interfaces in unary assemblies do not impede ion transport in the solid state. AC impedance spectroscopy and DC steady‐state conductivity measurements show that binary nanoparticle assemblies exhibit concurrent ionic and electronic conduction. The power‐law scaling percolation of both the ionic and electronic transport displays nonuniversal values of transport critical exponent, revealing different transport mechanisms. The simplicity of fabrication combined with the versatility in obtainable transport properties illustrates the power of using nanoparticle assemblies as a means to realize MIEC polymer mesoscale morphologies.