(300h) Engineering Block Copolymer-Derived Porous Carbon Nanofibers As Anodes for Sodium-Ion Batteries

For decades, lithium-ion batteries have seen widespread usage in a variety of applications from consumer electronics such as smartphones to the more recent developments of electric vehicles. As the usage of lithium for batteries increases, one growing concern is the finite amount that could be found within the Earth’s crust. An alternative that is being considered is sodium-ion batteries due to how plentiful sodium is in the Earth’s crust and similar chemical properties to lithium. One of the main challenges of sodium-ion batteries is the development of anode materials because sodium does not intercalate well with graphite, which is one of the most used materials in lithium-ion batteries. One promising development for anode materials is the use of hard carbon derived from the pyrolysis of polymers such as polyacrylonitrile (PAN) which can have various morphologies and potential for doping. Our work will focus on carbon nanofibers which show high 1-dimensional transport capabilities. With the addition of a sacrificial material such as polymethylmethacrylate (PMMA) that will be removed entirely during the pyrolysis step, PAN/PMMA can be made into porous carbon nanofibers to further increase ion transport. When a PAN/PMMA blend is used, the pores are very random with a high degree of variation of pore characteristics, however studies have shown that the creation of a PAN-b-PMMA block copolymer would allow for more uniform pore structures. Our work intends to study the effects of pore structures on the electrochemical characteristics of porous carbon nanofiber anodes for sodium-ion batteries. The cycling stability data of coin cells made using hard carbon nanofibers derived from electrospun PAN (Nonporous), PAN/PMMA (Random Porous), and PAN-b-PMMA (Uniform Porous), shows their respective discharging specific capacities (mAh/g) at 0.1 A/g average at about 80, 116, and 175. A slight increase can be seen with the addition of random, nonuniform pores to the PAN hard carbon, however, with the highly uniform and controlled pores resulting from the pyrolysis of the PAN-b-PMMA block copolymer, a very significant increase in the discharging specific capacity can be seen.