Nitrogen-Doped Hollow Carbon@Tin Disulfide as A Bipolar Dynamic Host for Lithium-Sulfur Batteries with Enhanced Kinetics and Cyclability

Interface control in TiO2/BaTiO3 ferroelectric heterostructures: A bidirectional catalytic pathway toward high-performance Li-S batteries

Li-S batteries (LSBs), noted for their high energy density and low cost, face challenges due to sluggish lithium polysulfide (LiPS) redox kinetics and complex phase transformations during charge/discharge cycles. Herein, we introduce a novel hollow nanocomposite, a titanium oxide/barium titanate (TiO2/BaTiO3) heterostructure with an ultrathin carbon coating, designed to act as a bidirectional electrocatalyst, enhancing the sequential conversion of sulfur (S8) to Li2S4 and then to lithium sulfide (Li2S). The ferroelectric nature of BaTiO3 enhances LiPS adsorption, reducing the shuttling effect and improving battery performance. The interface-induced electric field directs LiPS migration to TiO2, facilitating the redox process. An applied electric field polarizes the heterostructure, optimizing the dipole moment of BaTiO3 and further enhancing performance. Electrochemical measurements and theoretical calculations confirm the superior electrocatalytic activity of TiO2/BaTiO3@C for LiPS redox kinetics. The composite electrode achieves a high initial capacity of 836 mAh g-1 at 1C, retaining 64 % of its capacity after 400 cycles with a low fading rate of 0.075 % per cycle. Under practical operation conditions (sulfur areal loading: 6.02 mg cm-2; electrolyte/sulfur (E/S) ratio: 6.5 μL mg-1), the as-fabricated LSBs still demonstrate good areal capacities of 5.18, 4.09, 3.84, 3.64, and 3.15 mAh cm-2, respectively, at current densities from 0.05 to 0.5C. This study elucidates the critical synergy between self-induced electric fields and heterostructure engineering in polysulfide conversion, providing fundamental guidance for designing advanced catalysts in high-energy LSBs and related electrochemical energy systems.

Magnetopyrite Fe1-xS modified with N/S-doped carbon as a synergistic electrocatalyst for lithium-sulfur batteries

Rational design of effective cathode host materials is an effective way to solve the problems of serious shuttle and slow conversion of polysulfides in lithium-sulfur batteries (LSBs). However, the redox reaction of sulfur differs from conventional "Rocking chair" type batteries and involves a cumbersome phase transition process, so a single-component catalyst cannot consistently and steadily enhance the reaction rate throughout the redox process. In this work, a hybrid composed of magnetopyrite Fe1-xS catalyst-modified with N/S-doped porous carbon spheres (Fe1-xS@NSC) is proposed as a novel sulfur host to synergistically promote the adsorption and redox catalysis conversion of polysulfides. In this hybrid, the NSC skeleton provides excellent electrical conductivity and abundant adsorption sites for the physical immobilization of polysulfides; the magnetopyrite Fe1-xS nanoparticles promote the fast conversion reaction from Li2S2 to Li2S, affording strong adsorption and catalytic conversion. The optimal LSB with Fe1-xS@NSC manifests a high initial capacity of 971 mAh g-1 at 0.2 C (1 C = 1675 mAh g-1) and a retention rate of up to 75 % after 100 cycles. This work can provide a new approach for rationalizing the novel transition metal sulfide/porous carbon-based composite hosts with efficient lithium polysulfides (LiPSs) adsorption and catalytic conversion in high-performance lithium-sulfur batteries.

Exquisitely constructing hierarchical carbon nanoarchitectures decorated with sulfides for high-performance Li-S batteries

The sluggish reaction kinetics and notorious shuttle effect of polysulfides significantly hinder the practical application of lithium-sulfur batteries (LSBs). Therefore, polysulfides are anchored and their conversion reactions are catalyzed to enhance the performance of LSBs. Herein, an exquisite hierarchical carbon nanoarchitecture decorated with sulfides is designed and introduced into LSBs. Systematic experiments show that the nanoarchitecture not only enables rapid electron/ion migration but also functions as an active catalyst to increase polysulfide conversion, thus effectively reducing the shuttle effect. As a result, LSBs with the nanoarchitecture modified separator exhibited outstanding rate capacity (724.9 mA h g-1 at 5C), low self-discharge capacity loss (4.1% capacity loss after 72 h), and exceptional reversible capacity (1518.3 mA h g-1 at 0.1C and 25.6% capacity loss after 100 cycles). Through the design of a multifunctional separator, this study offers an effective way to minimize the shuttle effect and speed up redox conversion. The strategy of constructing nanoarchitectures provides an innovative route for hierarchical heterocatalyst design for LSBs.

Encapsulation of sulfur in MoS2-modified metal-organic framework-derived N, O-codoped carbon host for sodium-sulfur batteries

Room-temperature sodium-sulfur batteries (RT Na-S) are promising energy storage systems with high energy densities and low costs. Nevertheless, drawbacks, including the limited cycle life and sluggish redox kinetics of sodium polysulfides, hinder their implementation. Herein, a heterostructure of MoS2 nanosheets coated on a metal-organic framework (MOF)-derived N, O-codoped flower-like carbon matrix (NOC) was designed as a sulfur host for advanced RT Na-S batteries. The NOC@MoS2 hierarchical host provided a sufficient space to guarantee a high sulfur loading and confinement for the volume expansion of sulfur during the charge/discharge process. According to first-principle calculations, the NOC@MoS2 composite exhibited metallic conductivity because electronic states crossed the Fermi level, which indicates that the introduction of NOC significantly improved the electronic conductivity of MoS2. Furthermore, electron transfer from MoS2 to the O-doped carbon sites was observed owing to the strong electronegativity of O, which can effectively increase the Lewis acidity of MoS2 and weaken the sodium-sulfur bonds in sodium polysulfides after adsorption on the cathode, leading to reductions in the Na2S dissociation energy barrier and Gibbs free energy for the rate-limiting step of the sulfur reduction process. Therefore, with the synthetic effects of MoS2 and N, O-codoped carbon, the obtained cathode exhibited a superior electrochemical performance.

Engineering Strategies for Suppressing the Shuttle Effect in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are supposed to be one of the most potential next-generation batteries owing to their high theoretical capacity and low cost. Nevertheless, the shuttle effect of firm multi-step two-electron reaction between sulfur and lithium in liquid electrolyte makes the capacity much smaller than the theoretical value. Many methods were proposed for inhibiting the shuttle effect of polysulfide, improving corresponding redox kinetics and enhancing the integral performance of Li-S batteries. Here, we will comprehensively and systematically summarize the strategies for inhibiting the shuttle effect from all components of Li-S batteries. First, the electrochemical principles/mechanism and origin of the shuttle effect are described in detail. Moreover, the efficient strategies, including boosting the sulfur conversion rate of sulfur, confining sulfur or lithium polysulfides (LPS) within cathode host, confining LPS in the shield layer, and preventing LPS from contacting the anode, will be discussed to suppress the shuttle effect. Then, recent advances in inhibition of shuttle effect in cathode, electrolyte, separator, and anode with the aforementioned strategies have been summarized to direct the further design of efficient materials for Li-S batteries. Finally, we present prospects for inhibition of the LPS shuttle and potential development directions in Li-S batteries.