Environmental Sustainability of Natural Biopolymer-Based Electrolytes for Lithium Ion Battery Applications.

Biopolymer based electrolytes can overcome current performance limitations of lithium-ion batteries (LIBs). Biopolymers enable electrolytes with high ionic conductivities and wide electrochemical stability windows. While the biobased character of natural materials is claimed as an inherent advantage in meeting current environmental sustainability challenges, further research is required to quantify and compare their environmental impacts as electrolytes. The challenge is addressed by identifying the most promising biopolymer electrolytes for LIBs, measuring ionic conductivities and electrochemical stability windows, and quantifying environmental impacts using life cycle assessment. The environmental impacts of the cost to isolate cellulose derivatives, nanocelluloses, chitin/nanochitin, chitosan, lignin, agar, and silk are reported for climate change, acidification, freshwater ecotoxicity, marine eutrophication, human toxicity, and water use. Material criticality, circularity index, and material circularity indicator, emerging impact categories are prioritized to help integrate biopolymers into circular and sustainable materials. The electrochemical properties and environmental impacts of natural biopolymer membrane-liquid electrolyte pairs, gel electrolytes, and solid electrolytes are quantified and benchmarked against conventional fossil-based electrolytes, providing consistent and comparable electrochemical properties of the most relevant biopolymer electrolytes fabricated so far. This study highlights the significant functional and environmental benefits of biopolymer electrolytes and identifies the most electrochemically competitive biopolymer electrolytes in LIBs.