Development of biomass pyrolysis bio-oil as a renewable surface engineering agent for bio-based hard carbon production

Sodium-ion batteries (SIBs) are emerging as a promising alternative to lithium-ion batteries due to their potential for efficient and sustainable energy storage. Thus, the demand for high-performance battery materials with a sustainable supply chain, particularly hard carbon (HC) as the primary anode material for SIBs, is rapidly increasing. This study focuses on enhancing the production and electrochemical performance of HC products by leveraging Sweden's abundant forestry resources and advanced biomass refining processes. Specifically, we propose a novel HC production process that compresses sawdust-derived biocarbon with bio-oil derived from the same pyrolysis process to produce HC with improved properties, where the bio-oil serves as both a binder and a surface engineering agent for the biocarbon. This approach effectively modifies surface defects, leading to increased initial Coulombic efficiency (ICE), reaching values of 90 % in half-cell tests. Moreover, laboratory measurements and Life Cycle Assessment (LCA) results quantified that this production method achieves nearly 50 % higher HC yields and reduces greenhouse gas (GHG) emissions by approximately 20 % compared to the conventional production method. As a result, this offers a potentially more sustainable and economically viable solution for advancing the SIB anode material production.