Using Aquatic Plant-Derived Biochars as Carbon Materials for the Negative Electrodes of Li-Ion Batteries

The current study focuses on the production of biochars derived from aquatic plants, specifically red seaweed Ahnfeltia and seagrass Zostera and Ruppia, found in brackish lagoons in the Sea of Okhotsk, Sakhalin Island. These biochars were obtained through a stepwise pyrolysis process conducted at temperatures of 500 and 700 °C. The characteristics of the biochars, including their elemental composition, specific surface area, and particle size distribution, were found to be influenced by both the type of biomass used and the pyrolysis temperature. The primary objective of this research was to investigate the potential of these biochars to be used as negative electrodes for lithium ion batteries. Among the various samples we tested, the biochar derived from the macroalgae Ahnfeltia tobuchiensis, produced at 700 °C, exhibited the highest carbon content (70 at%) and nitrogen content (>5 at%). The reversible capacity of this particular biochar was measured to be 391 mAh g−1 during the initial cycles and remained relatively stable at around 300 mAh g−1 after 25 cycles. These findings suggest that biochars derived from aquatic plants have the potential to be utilized as effective electrode materials in lithium ion batteries. The specific properties of the biochar, such as its elemental composition and surface area, play a significant role in determining its electrochemical performance. Further research and optimization of the pyrolysis conditions may lead to the development of biochar-based electrodes with improved capacity and cycling stability, thereby contributing to the advancement of sustainable and environmentally friendly energy storage systems.