Polar Bilayer Cathode for Advanced Lithium–Sulfur Battery: Synergy Between Polysulfide Conversion and Confinement

Abstract

Despite possessing 5-fold higher specific energy density compared to commercial lithium-ion batteries, the insulating nature of sulfur and its reductive derivatives along with the uncontrollable migration of polysulfides hinder the commercialization of lithium-sulfur technology. Herein a bilayer cathode consisting of nitrogen sulfur codoped porous carbon network and titanium carbide has been introduced and investigated methodically. The porous sulfur host promotes uninterrupted diffusion of electrolyte and ions whereas titanium carbide acts as polysulfide trapping material. The superiority of this bilayer cathode over the conventional interlayer approach has been highlighted in terms of the diffusivity of lithium ions and the overall ohmic resistance. Variation in interfacial charge transfer resistance during charging and discharging has been investigated using dynamic electrochemical impedance spectroscopy. Discharge capacity reaches as high as 1300 mA h g–1 at 0.1 C with a Coulombic efficiency of 99%. Theoretical studies reveal that the polar nature and improved interfacial charge transfer between the TiC and polysulfides result in excellent binding strength and faster redox kinetics during operation, respectively. This work provides an experimental as well as theoretical evidence of the bifunctional mechanism of TiC toward polysulfide confinement and conversion.

Dual-role magnesium aluminate ceramic film as an advanced separator and polysulfide trapper in a Li–S battery: experimental and DFT investigations

“…To further demonstrate the origin of the improved electrochemical performance of the Li-S cell with the MAO separator over the Celgard s separator, we have performed DFT calculations to understand the interaction between Li The negative E ads confirms the spontaneous adsorption of Li 2 S x on MgAl 2 O 4 . 77 The S-Mg adsorption energy increases from À1.02 eV for Li 2 S 8 to À5.46 eV for Li 2 S. It is well known in the literature that the adsorption energy generally grows with the lithiation. 78 Similarly, the Li-O adsorption energy increases from À1.09 eV to À6.26 eV as the lithiation of S progresses (Li 2 S 8 to Li 2 S).…”

Insight into Lithium–Sulfur Batteries with Novel Modified Separators: Recent Progress and Perspectives

“…Various experiments on titanium-based materials have been conducted to overcome the shuttle effect in Li–S batteries. Ti 4 O 7 , − TiC, , TiO and TiO 2 , , and TiN − have all been studied for their ability to trap and adsorb polysulfides efficiently. With its excellent electrical conductivity and chemical stability, titanium diboride (TiB 2 ) has been suggested as an effective sulfur cathode host. , As a result of the strong TiB 2 chemical affinity for polysulfides, TiB 2 /S has been created in recent years to enhance electron transport and sulfur consumption while also alleviating the shuttle effect .…”

Immobilizing Polysulfide by In Situ Topochemical Oxidation Derivative TiC@Carbon‐Included TiO2 Core–Shell Sulfur Hosts for Advanced Lithium–Sulfur Batteries

“…On the other hand, as a congener of TiO 2 by substituting oxygen atom with carbon atom in the crystal lattice, TiC with a high conductivity (10 4 S cm −1 ) has also been widely investigated in the community of Li-S batteries. [29][30][31] Conductive TiC is endowed with favorable conversion efficiency, but weaker adsorption ability than TiO 2 for soluble LiPSs. As a result, the trapping and conversion capability of TiC for LiPSs is still a bottleneck issue.…”