Surface Defect Engineering of a Bimetallic Oxide Precatalyst Enables Kinetics-Enhanced Lithium–Sulfur Batteries

Abstract

Developing efficient electrocatalysts to accelerate the sluggish conversion of lithium polysulfides (LiPSs) is of paramount importance for improving the performances of lithium–sulfur (Li–S) batteries. However, a consensus has not yet been reached on the in situ evolution of the electrocatalysts as well as the real catalytic active sites. Herein, defective MnV2O6 (D-MVO) is designed as a precatalyst toward LiPSs’ adsorption and conversion. We reveal that the introduction of surface V defects can effectively accelerate the in situ sulfurization of D-MVO during the electrochemical cycling process, which acts as the real electrocatalyst for LiPSs’ retention and catalysis. The in situ-sulfurized D-MVO demonstrates much higher electrocatalytic activity than the defect-free MVO toward LiPSs’ redox conversion. With these merits, the Li–S batteries with D-MVO separators achieve superior long-term cycling performance with a low decay rate of 0.056% per cycle after 1000 cycles at 1C. Even under an elevated sulfur loading of 5.5 mg cm–2, a high areal capacity of 4.21 mAh cm–2 is still retained after 50 cycles at 0.1C. This work deepens the cognition of the dynamic evolution of the electrocatalysts and provides a favorable strategy for designing efficient precatalysts for advanced Li–S batteries using defect engineering.

Improvement of Redox Kinetics of Dendrite-Free Lithium–Sulfur Battery by Bidirectional Catalysis of Cationic Dual-Active Sites

“…The high areal capacity of 2.7 and 3.8 mAh cm –2 can still be obtained after 100 cycles at a current density of 0.5 mA cm –2 (Figure b). Additionally, recently published studies (Figure c) on modified separators were compared in terms of different aspects. ,− These results further proved that the 3DCS-FMO@C separator can still effectively improve sulfur electrochemistry and inhibit the shuttling of LIPSs in the case of high sulfur loading and poor electrolyte.…”

Dynamic evolution of electrocatalytic materials for Li–S batteries

“…118,119 Impressively, Gu et al designed defective MnV 2 O 6 (D-MVO) encompassing surface V defects as pre-electrocatalysts to track the phase evolution of cationic vacancies. 120 By virtue of XAS characterizations, the newly generated V–S bonds during electrochemical cycling echo the conception that V defects existing on the surface of D-MVO are conducive to enhancing the in situ sulfurization of D-MVO. As a result, the sulfurized D-MVO as the actual electrocatalyst lowers the Li 2 S decomposition barrier, accelerates the Li-ion transfer kinetics, and stimulates the catalytic conversion capacity of LiPSs.…”

In Situ Reconstruction of Electrocatalysts for Lithium–Sulfur Batteries: Progress and Prospects

“…It is very likely that most of the reported electron regulation strategies and the resulting catalytic mechanisms should be re-examined when the electrocatalysts undergo dynamic evolution during the charge/ discharge process. In fact, the nonnegligible harsh working conditions of Li-S batteries, that is, the polysulfide-rich aprotic environment, most likely lead to the reconstruction of electrocatalysts, [112][113][114][115][116] which can be electrochemically transformed into corresponding sulfurized or other composite electrocatalysts. [117][118][119][120] This phenomenon has been increasingly observed by different research groups, in which the catalytic characteristics of the electrocatalysts are inevitably altered, such as reaction sites, selectivity, activity, and amounts of catalytic sites, thereby changing the energy barrier and kinetics of catalytic reactions.…”