The development of high-capacity carbon anode materials can further increase the energy density of sodium ion batteries (NIBs). Recently, researchers at the Institute of Physics of the Chinese Academy of Sciences (IOP-CAS) have developed a high-capacity carbon anode (~ 400mAh g-1) for NIBs. The results were published in the Science Bulletin.
Since 2010, sodium ion batteries (NIBs) have received widespread attention for their cost, resource advantages, and applications in large-scale energy storage systems. However, the energy density of current spikes in sodium-ion batteries remains a serious challenge, preventing large-scale commercial applications. Hard carbon has the advantages of large capacity (~ 330mAh g-1), good cycle stability, high initial coulomb efficiency, low cost, and high natural abundance of precursor materials. It is one of the most promising anodes for early industrial NIBs.
Although much effort has been invested in the development of high-performance carbon anode materials, the consistency in the discharge-charge curve typically appears in two different regions: a slope region above ~ 0.1 V and a flat region below ~ 0.1V. Generally, the flat area has a higher capacity than the slope area, and high-capacity carbon anodes often show a significant proportion of flat area capacity, which can further increase the energy density of the full cell to a certain extent. Therefore, designing and discovering carbon anodes with a large proportion of flat capacity may be a potential way to increase the energy density of NIBs.
Recently, the research group of Professor Yongsheng Hu of the Institute of Physics, Chinese Academy of Sciences (IOP-CAS) carbonized a double honeycomb structure carbon material in a high-temperature graphite furnace at 1900 ° C. The carbon anode exhibits a high capacity of ~ 400mAh g-1, which is higher than the ~ 330mAh g-1 capacity of current hard carbon materials. 85% of its total capacity (> 330 mAh g-1) comes from long and low potential platforms below ~ 0.1V, which is different from the curve of typical NIBs hard carbon materials. When it is coupled with the stable Na0.9Cu0.22Fe0.30Mn0.48O2 layered cathode in the air, it can obtain a high energy density of ~ 240Wh kg-1, with good rate performance and cycle stability. The discovery of this promising carbon anode is expected to provide further research basis for high energy density NIBs for large-scale electrical energy storage.