Waste-derived hard carbon anode materials for sodium-ion batteries : The potential of using cardboard as precursor material in sodium-ion batteries for hard carbon production in Sweden

Abstract: In recent years, sodium ion batteries (SIBs) have emerged as a strong contender to lithium-ion batteries (LIBs). The most promising anode for the SIBs is hard carbon (HC), which can be derived from a wide variety of raw materials and waste globally. Using waste as raw material for SIB anodes has the potential to be a low-cost and sustainable alternative to the expensive and unsustainable LIB components. Recent research has presented a lot of potential waste-derived precursor materials for HC anodes for SIBs. However, the research of waste-derived precursors that are geographically relevant to Sweden are lacking. Given the abundance of annual waste cardboard in Sweden as well as the lack of research about it as a HC- anode, this study aims to explore its viability a precursor material for waste-derived HC anode production. For comparison, we have also included sawdust, an abundant material previously studied in Sweden, in our investigation. This study used a two-step carbonization approach, pyrolysis and high-temperature carbonization, to produce HC from cardboard. Specifically, the impact of varying carbonization temperatures (800, 1000, and 1300°C) on the structural characteristics of the hard carbon was investigated. The samples were analysed using SEM, Raman and XRD to determine their structural parameters. It was also tested for electrochemical performance by producing a half-cell battery, where it was tested for its capacity and initial coulombic efficiency (ICE). Furthermore, an economic analysis was made to review the profitability of the process where it  was concluded that it is more profitable to produce HC compared to incinerating it for energy, and that sawdust-derived HC is more profitable to produce in comparison to cardboard-derived HC. The results revealed sub-optimal structural parameters and an unsatisfactory electrochemical performance with a capacity of 108.9 - 140.8 mAhg-1 and an ICE of 77.3% for the cardboard-derived HC. The poor performance primarily stemmed from the high ash content of 17.49% within the cardboard, indicating that untreated cardboard should not be used as a raw material for a SIB anode and is not suitable for commercial usage.