The adsorption effect of freestanding SiOx-decorated stabilized polyacrylonitrile interlayers in lithium-sulfur batteries.

Lithium-sulfur batteries are well-known for their high theoretical specific capacity and high energy density. However, they undergo rapid capacity fading after the initial cycles due to the dissolution of polysulfides which further results in the shuttle effect. To address this issue and to protect the Li anode surface, silicon suboxide decorated stabilized polyacrylonitrile (sPAN-SiOx) fibermats are used as a freestanding interlayer on the cathode side. Polysulfides are easily captured at the cathode side with the help of the complementary adsorption effect of oxygen-containing functional groups, SiOx and the pyridinic-N structure of sPAN-SiOx resulting in better electrochemical cell performance. The adsorption effect of those functional groups and SiOx is confirmed by X-Ray Photoelectron Spectroscopy (XPS) analysis as obvious shifts in the binding energies and reductions of the peak intensities in the presence of polysulfides. The battery cell with the sPAN-SiOx interlayer shows a discharge capacity of 646 mA h g-1 after 100 cycles of charge-discharge at C/5 current density which is a significant increase compared to the cells with a stabilized polyacrylonitrile (sPAN) interlayer or the cells without an interlayer.

In-situ wrapping of tin oxide nanoparticles by bacterial cellulose derived carbon nanofibers and its application as freestanding interlayer in lithium sulfide based lithium-sulfur batteries.

Lithium-Sulfur (Li-S) batteries are mostly known for their high energy density and cost-effectiveness. However, their intrinsic problems hinder their implementation into the marketplace. The most pronounced problems are the parasitic reactions which occur between lithium polysulfides species and lithium metal anode, the volume expansion of sulfur (80%) at the end of discharge and the safety issues which are linked with the use of lithium metal. Herein this work, two approaches are applied to prevent these effects; one approach is the use of Li2S as cathode material, instead of starting from sulfur powder, both to circumvent the volume expansion of sulfur taking place during discharge and to enable lithium-free anodes cell assembling (i.e. Si-Li2S or Sn-Li2S cell configurations). Second approach deals with the lithium anode protection by SnO2 containing freestanding pyrolyzed bacterial cellulose interlayers located between anode and cathode electrodes. Since bacterial celluloses are formed in the presence of SnO2 nanoparticles, the resulting structure enables intimate contact between carbon and SnO2 nanoparticles. By employing Li2S cathode and freestanding interlayer concurrently, 468 mAh g-1 discharge capacity is obtained at C/10 current density over 100 cycles.