Sulfur Reduction Catalyst Design Inspired by Elemental Periodic Expansion Concept for Lithium–Sulfur Batteries

Abstract

The key challenges facing the commercialization of lithium–sulfur (Li–S) batteries are shortening the lithium polysulfide (LiPS) intermediate existence time while accelerating solid-phase conversion reactions. Herein, inspired by highly efficient natural enzymes with Fe/N active sites for oxygen reduction reactions, we report a periodic expansion catalysis concept, i.e., Ru and P synergic stereoselectivity, for designing sulfur reduction reaction (SRR) catalysts. As a proof of concept, a RuP2-configuration molecular catalyst was exploited to assemble an interlayer in Li–S batteries that adsorbs LiPSs, optimizes Li+ migration paths, and catalyzes SRRs. Comprehensive investigation identified the elimination of steric hindrance and strong electron orbital couplings between metallic d band and nonmetallic p band as the main contributing factors of PEC for the SRRs. As a result, the Li–S battery with ∼0.5 wt % catalyst additive showed enhanced cycling stability even under a high sulfur loading (6.5 mg cm–2) and low electrolyte/sulfur ratio (9 μL mg–1).

Unity of Opposites between Soluble and Insoluble Lithium Polysulfides in Lithium–Sulfur Batteries

“…Considering the similarity between SRR and oxygen reduction reaction (ORR), a brilliant strategy would be to design catalysts that can promote the SRR process based on past research studies on the ORR catalytic mechanism. [ 94 ] However, the introduction of catalysts is bound to reduce the overall energy density of the battery. In addition, the mechanism of SRR catalysts, as it is presently known, is still unclear and needs to be further explored in the future.…”

Electrocatalyst Modulation toward Bidirectional Sulfur Redox in Li–S Batteries: From Strategic Probing to Mechanistic Understanding

“…[ 60 ] It is worth noting that the conversion of PSs to Li 2 S accounts for ≈75% of the total capacity and is deemed as the rate‐determining step. [ 61 ] In terms of reverse sulfur evolution reaction (SER), it is compromised by the high activation energy of Li 2 S dissociation, thereby leading to a wealth of “dead” sulfur and restraining sulfur redox kinetics. [ 62 ] Even worse, the catalytic effect of heterogeneous electrocatalysts heavily relies on the surface reaction and hence the limited active sites on their surface might be completely covered by the insulating discharge products (i.e., Li 2 S/Li 2 S 2 ), which results in the premature termination of sulfur redox reaction.…”

Cobalt Nanoparticles Loaded on MXene for Li‐S Batteries: Anchoring Polysulfides and Accelerating Redox Reactions

“…Lithium-sulfur (Li-S) batteries, as attractive post-lithium ion battery technologies, [1] have a high theoretical energy density (2600 Wh kg -1 ) and theoretical capacity (1672 mAh g -1 ) due to multi-electron redox reactions and intrinsic properties of sulfur. [2][3][4] However, in the typical Li-S batteries using prevailing ether electrolytes, the low active sulfur utilization is due to the converted into Co NPs via the reduction of NaBH 4 (Figure S1-S2, Supporting Information). In addition, compared with pristine Ti 2 C, the Ti 2p spectrum of Co/Ti 2 C shows an obvious shift to the higher binding energy.…”

“…Lithium‐sulfur (Li‐S) batteries, as attractive post‐lithium ion battery technologies, [ 1 ] have a high theoretical energy density (2600 Wh kg –1 ) and theoretical capacity (1672 mAh g –1 ) due to multi‐electron redox reactions and intrinsic properties of sulfur. [ 2–4 ] However, in the typical Li‐S batteries using prevailing ether electrolytes, the low active sulfur utilization is due to the low conductivity of S/Li 2 S and the shuttle effect, which cause the low charge transfer rate, a series of the competitive side reactions between the migrated lithium polysulfides (LiPSs) and Li metal, respectively, [ 5–10 ] and a limited practical energy density.…”