Surface area to volume ratio concept in microvilli-like sulphur electrode of lithium sulphur batteries

Maximizing surface area is a core pursuit in many everyday applications such as harnessing solar energy through solar photovoltaic and catalysing chemical reactions via industrial catalysts. The same principle is also at work in batteries where the electrodes mediate the transfer of electrons to and from charge carriers in the liquid electrolyte between electrodes. Similarly, lithium ion batteries utilize electrodes for storing lithium ions which serve as the charge carriers, and thus, the electrodes benefit from a large surface area as the lithium ions are stored on the electrode surface. Surface area, however, is only one part of the equation, as a large surface area would also incur cost of space: i.e., how to pack more charge in a defined volume. Adding to the mix is the weight commonly associated with a large volume. Theoretically, lithium sulphur batteries have a higher charge density compared to lithium ion batteries utilizing commercialized graphite electrodes. Nevertheless, their practical application is hampered by the formation of polysulphides at the electrode as well as volume expansion and contraction problems during charge/discharge given that lithium ion intercalates into the sulphur matrix. Taking a leaf from the human gut microvilli which has a large surface area to volume ratio, battery researchers have designed and fabricated a lithium sulphur battery with microvilli-like electrodes, which further increases charge density due to a large surface area to volume ratio. Here, an appended graphical abstract, which accompanied a blog post I wrote on the advance in lithium sulphur battery design and research, may find use as an educational tool for highlighting the concept of long and thin structures as one possible geometry for increasing surface area to volume ratio to students in secondary schools, high schools, polytechnics and universities. The blog post mentioned is at https://ngwenfa.wordpress.com/2016/11/13/high-surface-area-to-volume-ratio-electrodes-in-lithium-sulphur-batteries/