High-Index Faceted Nanocrystals as Highly Efficient Bifunctional Electrocatalysts for High-Performance Lithium–Sulfur Batteries

Abstract

Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium–sulfur (Li–S) batteries. Herein, high-index faceted iron oxide (Fe2O3) nanocrystals anchored on reduced graphene oxide are developed as highly efficient bifunctional electrocatalysts, effectively improving the electrochemical performance of Li–S batteries. The theoretical and experimental results all indicate that high-index Fe2O3 crystal facets with abundant unsaturated coordinated Fe sites not only have strong adsorption capacity to anchor polysulfides but also have high catalytic activity to facilitate the redox transformation of polysulfides and reduce the decomposition energy barrier of Li2S. The Li–S batteries with these bifunctional electrocatalysts exhibit high initial capacity of 1521 mAh g−1 at 0.1 C and excellent cycling performance with a low capacity fading of 0.025% per cycle during 1600 cycles at 2 C. Even with a high sulfur loading of 9.41 mg cm−2, a remarkable areal capacity of 7.61 mAh cm−2 was maintained after 85 cycles. This work provides a new strategy to improve the catalytic activity of nanocrystals through the crystal facet engineering, deepening the comprehending of facet-dependent activity of catalysts in Li–S chemistry, affording a novel perspective for the design of advanced sulfur electrodes.

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

“…Considering that the particular crystal facet of nanocatalysts might harness the selective electrocatalytic activity for accelerating the specific reaction step in Li–S batteries, the rational adjustment of crystal facet exposure offers an appealing solution to realize bidirectional polysulfide electrocatalysis. [ 141 ] In this sense, Yu et al. designed VO 2 with highly exposed (110) and (002) facets (denoted as (110)VO 2 and (002)VO 2 , respectively) to probe the facet effect for catalyzing bidirectional Li–S chemistry.…”

“…Considering that the particular crystal facet of nanocatalysts might harness the selective electrocatalytic activity for accelerating the specific reaction step in Li-S batteries, the rational adjustment of crystal facet exposure offers an appealing solution to realize bidirectional polysulfide electrocatalysis. [141] In this sense, Yu et al designed VO 2 with highly exposed ( 110) and (002) facets (denoted as (110)VO 2 and (002)VO 2 , respectively) to probe the facet effect for catalyzing bidirectional Li-S chemistry. [142] To begin with, the cyclic voltammetry (CV) profile of sulfur cathode with (110)VO 2 additive exhibits higher current response and lower potential difference as compared to that of (002)VO 2 -mediated electrode, which is indicative of the reduced reaction polarization and elevated redox kinetics (Figure 6a).…”

Construction of Ultrathin Layered MXene-TiN Heterostructure Enabling Favorable Catalytic Ability for High-Areal-Capacity Lithium–Sulfur Batteries

“…In addition, researchers found that excessive adsorption will give rise to the decomposition of LiPSs and thus hinder the electrochemical redox reactions [ 17 – 19 ]. Recently, catalytic effect has been recognized as the key technology to improve conversion kinetics and inhibit the shuttle effect simultaneously [ 20 , 21 ]. The conversion of sulfur species is accelerated and thus the shuttle effect is mitigated [ 22 ].…”

Manganese–nickel bimetallic oxide electrocatalyzing redox reactions of lithium polysulfides in lithium–sulfur batteries

“…That is, one component is for LiPS capture and the other is for catalyzing LiPS conversion. 16,17 Over the past few years, researchers have proposed some catalysts as the substrate in sulfur cathodes 18–20 or polypropylene (PP) separators 21–23 so as to accelerate the liquid–solid conversion kinetics, materials such as metal oxides, 24–26 metal sulfides, 21,27 metal nitrides 20,28 and metal selenides. 29,30 Manganic oxides have been proven to strongly adsorb LiPS, both experimentally and theoretically.…”