Page 368 - Polymer-based Nanocomposites for Energy and Environmental Applications

Nanofibrous composites for sodium-ion batteries 335

Fig. 12.2 Schematic of Na-ion battery and its electrochemical reaction mechanism.

the performance of the electrochemical cell. The role of the electrodes within the cell
is to accept ions and release the electrons, hence closing the circuit that enables energy
storage and release. The electrolyte is the component that provides sufficient amount
of ions, while the separator has to prevent physical contact between the two electrodes
and to allow smooth transport of ions from one to another electrode. The working
mechanism of the Na-ion battery is given in Fig. 12.2. The electrochemical and
structural behaviors of these constituents during charge-discharge determine the
performance of the battery. Thus, the research and development of structures and
materials for each constituent are of great interests for the progress of new energy
storage systems, such as Na-ion batteries.
The studies on positive and negative electrodes for Na-ion batteries are analogues
of those used in Li-ion battery [9]. However, Na cation shows different electrochem-
ical behavior when intercalating into the cathode due to the larger diameter of Na ion.
Thus, materials with open and layered structures are more promising cathode mate-
rials. Similarly, anode materials with larger intercrystalline spaces are also needed,
in spite that the behavior of Na-ion intercalation into the anode is comparable with
the one of Li ion. The research interest is also focused on how to enhance the produc-
tivity of cathode and anode materials, whose manufacturing costs represent 32.4% and
13%, respectively, of the total cost for NIB manufacturing [10]. Another focus of
interest is in electrolytes with higher Na-ion conductivity in order to improve the
battery performances [6].

12.1.2 Nanofibers

With the development of nanotechnology, nanostructures, and their production
methods in the last decades, the application of nanomaterials increases progressively
in many areas, and energy storage sector is not staying behind. Nanomaterials used in