A Review on Engineering Transition Metal Compound Catalysts to Accelerate the Redox Kinetics of Sulfur Cathodes for Lithium–Sulfur Batteries

Abstract

Engineering transition metal compounds (TMCs) catalysts with excellent adsorption-catalytic ability has been one of the most effective strategies to accelerate the redox kinetics of sulfur cathodes. Herein, this review focuses on engineering TMCs catalysts by cation doping/anion doping/dual doping, bimetallic/bi-anionic TMCs, and TMCs-based heterostructure composites. It is obvious that introducing cations/anions to TMCs or constructing heterostructure can boost adsorption-catalytic capacity by regulating the electronic structure including energy band, d/p-band center, electron filling, and valence state. Moreover, the electronic structure of doped/dual-ionic TMCs are adjusted by inducing ions with different electronegativity, electron filling, and ion radius, resulting in electron redistribution, bonds reconstruction, induced vacancies due to the electronic interaction and changed crystal structure such as lattice spacing and lattice distortion. Different from the aforementioned two strategies, heterostructures are constructed by two types of TMCs with different Fermi energy levels, which causes built-in electric field and electrons transfer through the interface, and induces electron redistribution and arranged local atoms to regulate the electronic structure. Additionally, the lacking studies of the three strategies to comprehensively regulate electronic structure for improving catalytic performance are pointed out. It is believed that this review can guide the design of advanced TMCs catalysts for boosting redox of lithium sulfur batteries.

Optimized Adsorption–Catalytic Conversion for Lithium Polysulfides by Constructing Bimetallic Compounds for Lithium–Sulfur Batteries

“…Moreover, the density of states of different materials was also calculated. The (CuCo)Se2 presents a higher density of states around the Fermi level in comparison to CoSe2 and (NiCo)Se2 (Figure 6a), meaning a better electron conductivity, which can help to accelerate the electrochemical reaction [8,47,48]. Charge density difference analyses are further displayed in Figure 6b,c, the yellow region stands for charge accumulation and the cyan region means charge depletion.…”

“…Currently, catalyst materials for Li-S batteries mainly include metal oxides, metal sulfides, metal nitrides, and metal phosphates with single metal components [8,9]. Considering the complex and multistep conversion of LiPSs in the process of charge-discharge and the difficulty of adjusting the electron structure of catalysts by single, it is extremely necessary to modify metal components for increasing active site and adjusting its catalytic activity with introduced metal ions [10][11][12].…”

“…Considering the complex and multistep conversion of LiPSs in the process of charge-discharge and the difficulty of adjusting the electron structure of catalysts by single, it is extremely necessary to modify metal components for increasing active site and adjusting its catalytic activity with introduced metal ions [10][11][12]. The methods involve doping and the construction of bimetallic compounds [8,[13][14][15]. Among them, doping modifications are deeply studied to boost the catalytic activity of catalysts for Li-S batteries, while bimetallic compounds should be further developed even though some reports.…”

Rechargeable Metal-Sulfur Batteries: Key Materials to Mechanisms

“…Heterostructures with more than one transition metal compound can more effectively endow the host material with optimal absorptivity and conductivity properties without requiring such trade-offs. 232 Constructing heterostructures with multiple metal cations can enable hosts that adsorb polysulfides effectively and also have high catalytic activity. Li et al have revealed that an effective heterostructure host can be produced by selecting two metal cations that produce compounds with large bandgap differences.…”

“…Heterostructures with more than one transition metal compound can more effectively endow the host material with optimal absorptivity and conductivity properties without requiring such trade-offs . Constructing heterostructures with multiple metal cations can enable hosts that adsorb polysulfides effectively and also have high catalytic activity.…”