Cover Feature: High Entropy Oxide (CrMnFeNiMg)₃O₄ with Large Compositional Space Shows Long‐Term Stability as Cathode in Lithium‐Sulfur Batteries (ChemSusChem 8/2023)

Stable Lithium–Sulfur Cell Separator with a High-Entropy Metal Oxide Modification

“…However, the generated polysulfides also diffused irreversibly from the cathode, which caused the low and unstable capacity. 2,25,26 Thus, the comparison confirms that the HEMO-modified separator endowed the lithium−sulfur cell with a high electrochemical utilization ability and a high rate capacity.…”

“…At a high cycling rate of 1C, the sulfur cathode in the cell showed an initial activation process to reach the peak capacity. However, after activation, the HEMO-modified separator provided the cell with good stability at high cycling rate. − In Figures h and i, the charge–discharge curves of the cell at C/2 and 1C rates, respectively, showed the stable and complete discharge and charge curves during 200 cycles. The overlapping discharge curves and charge curves demonstrated that the lithium–sulfur cell with the HEMO-modified separator attains high electrochemical stability and limited polarization.…”

“…In our previous studies, we have designed the (CrMnFeNiMg) 3 O 4 HEMO as the HEMO/phase-inverted carbon electrode substrate for demonstrating the high-sulfurloading ability and attaining a high energy density of the cell 25 and as the HEMO/sulfur energy-storage material for exhibiting the long-term cycle stability and life span. 26 In order to conduct a systemic study of the novel HEMO, the (CrMnFeNiMg) 3 O 4 HEMO is used to prepare the HEMOmodified separator that incorporated the HEMO nanomaterial into its carbon coating and had a low mass loading of 0.2 mg cm −2 . The resulting functional coating was configured to face the sulfur cathode to block polysulfide migration, i.e., so the HEMO-modified carbon coating adsorbed the diffusing polysulfides.…”

“…The configurational entropy value (ΔS) of the resulting (CrMnFeNiMg) 3 O 4 was calculated using the equation −R∑[a i ln(xa i )], where R is the gas constant, a i is the mole fraction of cation component, and x is the mole fraction of elements in the cation sites. The resulting ΔS was 1.6R and therefore indicated the (CrMnFeNiMg) 3 O 4 as a highentropy metal oxide, 25,26 which we named (CrMnFeNiMg) 3 O 4 HEMO. In this work, the as-prepared HEMO (80 wt %) was mixed with conductive carbon (10 wt %) and poly(vinylidene fluoride) (PVDF) binder (10 wt %) in N-methyl-2-pyrrolidone (NMP) for 24 h at room temperature to form a uniform coating slurry.…”

“…Thus, sulfur/oxide nanocomposites with multicomponent metal oxides have demonstrated higher capacity retentions and stabilities than single metal oxides. − In addition to the novel materials, new cell configurations have also been explored with the aim of hosting the active material within the cathode region by replacing the conventional cell components borrowed from the lithium-ion battery cathode. For instance, a porous current collector has been designed to replace an aluminum current collector, as the former is a conductive and lightweight substrate that has a high sulfur-accommodation capacity. − Alternatively, the fast migration of dissolved polysulfides can be blocked by inserting an interlayer between a cathode and a separator; interlayers of conductive carbon, ionic-selective polymer, and polysulfide-trapping oxide have been used for this purpose. ,, These functional materials have also been adapted for separator modification, i.e., as additives in carbon-coating layers, to further simplify the manufacturing process, improve material selectivity, and decrease weight. − Such cells have exhibited optimal cyclability and rate capabilities.…”