Activated and carbonized metal-organic frameworks for improved cycle performance of cathode material in lithium-sulphur batteries

Abstract

The development of new battery systems has been intensively pursued in an effort to increase energy densities. Lithium-sulphur batteries represent a group of next-generation batteries with high theoretical capacity and energy density. The electrochemical properties of lithium-sulphur batteries may be improved by the application of appropriate conductive and porous additives to sulphur in the cathode material. Recently, materials belonging to the group of metal-organic frameworks (MOFs) have been widely investigated as host materials for sulphur thanks to their unique porous structure. In this work, various types of MOFs (GaTCPP, MOF-76(Gd), MIL-101(Fe)-NH2) were applied to the cathode material. MOFs were activated or carbonized before cathode material preparation. The structure of activated GaTCPP showed the lowest capacity fading per cycle (0.07 %) from activated MOFs during cycling at 0.5 C for 200 cycles. The carbonization process may improve the electrochemical properties of the electrode material. The best electrochemical properties showed carbonized MOF-76(Gd), and the capacity fading rate per cycle was only 0.04 % despite 200 cycles at 0.5 C.

Porous Nb2O5 Nanofibers Prepared via Reactive Needle-Less Electrospinning for Application in Lithium–Sulfur Batteries

“…The voltage of the high and low voltage plateau decreases with the degradation of the battery. The obtained results are comparable with results published by the authors for the application of MOFs in LSBs [7]. For the sake of comparison and emphasizing the effect of Nb2O5 nanofibers in addition to the cathode material, the same cathode was prepared without ceramic additives and tested similarly.…”

“…The voltage of the high and low voltage plateau decreases with the degradation of the battery. The obtained results are comparable with results published by the authors for the application of MOFs in LSBs [7]. To further demonstrate the positive effect of the Nb2O5 fibers, the cycling stability of the Li-S battery with the S/Nb2O5 cathode was evaluated during long-term cycling at 0.5 C (see Figure 9a).…”

“…With more than three decades of development of rechargeable lithium-ion batteries (LIBs), a variety of electrode active materials was tested: oxide ceramics, carbon polymorphs, etc. Meanwhile, lithium-sulfur batteries (LSBs) are seen as the most promising successors to rechargeable LIBs due to their superior theoretical energy density of 2600 Wh kg −1 and theoretical capacity of 1675 mAh•g −1 [4,6,7]. Despite the low cost, low toxicity, and wide natural abundance of sulfur, LSBs have their drawbacks and face challenges such as the formation of polysulfides, the loss of active sulfur, its dissolution/diffusion in the electrolyte during the discharge cycle, the so-called shuttle effect, and the volume expansion of the cathode containing S. In LSBs, the shuttle effect is one of the main reasons for capacity decay and low charge efficiency [6][7][8].…”

“…Meanwhile, lithium-sulfur batteries (LSBs) are seen as the most promising successors to rechargeable LIBs due to their superior theoretical energy density of 2600 Wh kg −1 and theoretical capacity of 1675 mAh•g −1 [4,6,7]. Despite the low cost, low toxicity, and wide natural abundance of sulfur, LSBs have their drawbacks and face challenges such as the formation of polysulfides, the loss of active sulfur, its dissolution/diffusion in the electrolyte during the discharge cycle, the so-called shuttle effect, and the volume expansion of the cathode containing S. In LSBs, the shuttle effect is one of the main reasons for capacity decay and low charge efficiency [6][7][8]. Soluble long-chain polysulfides migrate to the lithium anode and react irreversibly, and then they form shorter polysulfides, which again flow back to the cathode.…”

“…One of the accepted approaches to eliminate or at least minimize this shuttle effect is to introduce cathode materials, which have an affinity towards polysulfides and can adsorb or immobilize on their surfaces or catalytically convert soluble polysulfides into shorter ones already in the cathode; thus, they arrest the migration of polysulfides towards Li surfaces. The diffusion of polysulfides into the electrolyte will result in capacity decay, a lowering of the Coulombic efficiency, and the uncontrollable deposition of Li 2 S 2 , Li 2 S, and sulfur [6,7].…”