Protein-rich tryptic soy broth biomaterial for improving solid polymer electrolyte lithium-ion battery performance

Aiming toward sustainable, economic, safe, and environmentally friendly energy storage, biomaterials and bio-inspired designs are increasingly adopted in battery materials and device fabrications. Here, we investigate a commonly found protein-rich solution containing soy proteins and tryptone amino acids, known as tryptic soy broth (TSB), as an additive biomaterial for solid polymer electrolytes (SPEs). SPE-based batteries offer many advantages, but two key issues persist, namely, low bulk ion conductivity and high interfacial impedance between the solid electrode and solid polymer electrolyte. Protein is an intrinsically surface-active molecule due to its large amphipathic nature and it has the potential to improve interfacial ion diffusion owing to the side groups on the chain. The electrochemical impedance spectroscopy of the solid polyethylene oxide (PEO) electrolyte/TSB shows one order of magnitude increase in the bulk ion conductivity and the diffusion coefficient of the biomaterial polymer electrolyte. Moreover, the capacity of the biomaterial-polymer based lithium-ion battery is found to improve significantly, attributed primarily to better interfacial ion transfer between the electrode and the PEO-TSB electrolyte, decrease in the crystallization of the electrolyte, and increased bulk ion conductivity.