Highly Robust Lithium Ion Battery Anodes from Lignin: An Abundant, Renewable, and Low-Cost Material

The synthesis, processing, and performance of a low‐cost monolithic battery electrode, produced entirely of natural and renewable resources, are reported. This anode material exhibits tunable electrochemical performance suitable for both high power and high energy applications. A synthesis method that directly results in electrically interconnected three‐dimensional architectures is presented, where the carbon framework functions as current collector and lithium insertion material, eliminating the extra mass and expense of inactive materials in conventional designs. Fibrous carbon electrode materials are produced from solvent extracted lignin using scalable melt processing technology and thermal conversion methods. The resulting free‐standing electrodes exhibit comparable electrochemical performance to commercial carbon‐based anodes at a fraction of the materials and processing costs. Compositional and electrochemical characterization shows that carbonized lignin has a disordered nano‐crystalline microstructure. The carbonized mats cycle reversibly in conventional aprotic organic electrolytes with Coulombic efficiencies over 99.9%. Moreover, lignin carbon fibers carbonized at 2000 °C can cycle reversibly in 1 m LiPF6 in propylene carbonate. A novel synthetic technique for lignin‐based carbon fibers, where the fibers are fused to each other resulting in monolithic fibrous mats, is described. The unique fiber microstructures and mat morphologies provide favorable electrochemical performance for lithium ion battery anode applications. The fibers cycle reversibly versus Li metal in alkyl carbonate electrolytes.