Building Ion-Conduction Highways in Polymeric Electrolytes by Manipulating Protein Configuration

Solid polymer electrolytes play a critical role in the development of safe, flexible, and all-solid-state energy storage devices. However, the low ion conductivity has been the primary challenge impeding them from practical applications. Here, we propose a new biotechnology to fabricate novel protein-ceramic hybrid nanofillers for simultaneously boosting the ionic conductivity, mechanical properties, and even adhesion properties of solid polymer electrolytes. This hybrid nanofiller is fabricated by coating ion-conductive soy proteins onto TiO2 nanoparticles via a controlled denaturation process in appropriate solvents and conditions. It is found that the chain configuration and protein/TiO2 interactions in the hybrid nanofiller play critical roles in improving not only the mechanical properties but also the ion conductivity, electrochemical stability, and adhesion properties. Particularly, the ion conductivity is improved by one magnitude from 5 × 10-6 to 6 × 10-5 S/cm at room temperature. To understand the possible mechanisms, we perform molecular simulation to study the chain configuration and protein/TiO2 interactions. Simulation results indicate that the denaturation environment and procedures can significantly change the protein configuration and the protein/TiO2 interactions, both of which are found to be critical for the ion conductivity and mechanical properties of the resultant solid composite electrolytes. This study indicates that biotechnology of manipulating protein configuration can bring novel and promising strategies to build unique ion channels for fast ion conduction in solid polymer electrolytes.