Efficient Transformation of Bituminous Grade Noncoking Coal into Hard Carbon for High-Performance Sodium-Ion Battery Anodes: A Sustainable and Cost-Effective Energy Storage Solution
Gopal Sebak Goswami, Anirban Ghosh, Srijib Das, Naresh Chandra Murmu, Brij Kishore, Tapas Kuila
Abstract
Hard carbon, characterized by its low surface area and optimized pore structure, is considered one of the most promising anode materials for sodium-ion batteries due to its high capacity in the low-voltage plateau. Progenitors are crucial to both the final cost and yield of synthesized hard carbon. So, in this context, cost-effective bituminous grade noncoking coal is used as a precursor for hard carbon. Interestingly, this coal has ∼40% ash, negatively impacting the final product’s electrochemical performance. However, this study’s chemical and physical processes remove all kinds of ashes/impurities from the raw coal. Finally, the hard carbon is synthesized at ∼1500 °C and ∼55% yield of the final product is obtained, consisting of micro- and mesopores, a disordered structure with a low surface area of ∼4.2 m 2 g –1 . The hard carbon exhibits a specific capacity of ∼259 mAh g –1 with an extended plateau region when cycled at a specific current of ∼80 mA g –1 . Due to extended layer spacing and generation of micro- and mesopores, it shows a sound diffusion of Na + ions of ∼3.6004 × 10 –15 cm 2 s –1 . Upon long cycling, this material shows a cyclic stability of ∼76% up to 100 cycles, proving its effectiveness. When applied to the full cell, against the NVP@C cathode, it exhibits an energy density of ∼165 Wh kg –1 .