Bacterial Cellulose Derived Carbon Nanofibers As High Capacity Anode for Lithium-Ion Batteries

Despite recent developments at lab-scale, Lithium ion is still fastest growing and most promising technology for rechargeable batteries. Although graphite has been conventionally used as anode materials in commercial Li ion batteries, a lot of other allotropes of carbon have also been explored in literature. Carbon nanofibers (CNF) based anode which are primarily derived from polymer precursors such as PAN, SU-8 negative photoresist, cellulose acetate is one such example. However, there is still a need to look for alternative precursors to yield CNF on commercial basis using a scalable, low-cost and sustainable route. Bacterial cellulose, a β-1,4 linked exopolysaccharide which is produced by some special kind of obligate aerobic bacteria is one such potential precursor. Bacterial cellulose which is devoid of lignin, hemicellulose and pectin unlike plant cellulose, comprises three-dimensional (3-D) inter woven nanofibrous network. Bacterial cellulose has several unique properties like higher degree of crystallinity, greater mechanical properties and modability. The fiber morphology and porosity of bacterial cellulose can be controlled to a great extent by employing different fermentation conditions, post treatment (drying and purification) and modifying the network formation by additives in fermentation media. Recent advances not only allows in-situ modification of bacterial cellulose properties using additives but also there are few reports on controlling the orientation and patterning of bacterial cellulose nanofibrils. However there are only few recent studies on exploring the bacterial cellulose as a polymer precursor to carbon upon controlled pyrolysis and to use them as anode. There is still a gap towards the integration of modifying the structural properties of bacterial cellulose and to correlate its effect on as-derived CNF and to further evaluate their electrochemical performance. This work is an effort toward this objective. In the present work, we will first discuss the fermentative production of bacterial cellulose, influence of bioprocess parameters and post production treatments on its physiochemical properties, followed by controlled pyrolysis to yield bacterial cellulose derived CNF. Average diameter of bacterial cellulose CNF was in the range of 20-50 nm. Depending on the fermentation media and growth conditions, crystallinity of bacterial cellulose and its derived carbon can be tuned to a great extent. These bacterial cellulose derived CNF were then used as an anode in half-cell configuration to investigate their electrochemical performance. We shall also present the way forward to explore the in-situ modification of bacterial cellulose to further provide a tight control on the physiochemical properties of CNFs upon pyrolysis with the perspective of their utilization as high performance anode for lithium-ion batteries. Given the scalability and relative low cost production of bacterial cellulose and as-derived CNFs may pave the way of their utilization for commercial electrodes in future