Jun Pu

The shuttle effect and slow reaction kinetics of soluble lithium polysulfides (LiPSs) have a significant impact on the cycle life and rapid charging and discharging capacity of lithium-sulfur (Li-S) batteries. Herein, the Fe-based MBene material was adopted to alleviate the above problems. Unlike previous LiF etching techniques, petal-shaped Fe₂Al1-_xB₂ was obtained through simple, nontoxic alkaline solution etching. The sheet-like two-dimensional structure not only effectively provided a large quantity of FeB adsorption active sites but also effectively reduced the resistance to charge transfer. Based on these advantages, the sulfur cathode modified with Fe₂Al1-_xB₂ thin layers achieved reversible capacities of 1103 and 478 mA h g^-1 at rates of 0.2 and 4 C, respectively. Even under high loading, the solution could provide an initial areal capacity of 5.4 mg cm^-2. It provided a new idea for the Li-S application of Fe-based two-dimensional borides.

The shuttle effect of lithium polysulfides (LiPSs) and sluggish redox kinetics severely restrict the development of high-energy lithium–sulfur (Li–S) batteries. To alleviate this issue, this study adopts an in situ design strategy to construct tungsten carbide (WC) nanocrystals on the surface of two-dimensional (2D) tungsten boride (WB)-based MBene, creatively forming a WB@WC heterostructure to optimize the adsorption–migration–catalysis mechanism of LiPSs. The WB–WC heterointerface reduces the reaction energy barrier of LiPSs due to the electron delocalization effect and promotes the deposition/dissociation of Li ₂ S and the transfer of charge. In situ Raman verified that WB@WC can effectively inhibit LiPSs shuttling. In situ X-ray absorption fine structure spectroscopy (XAFS) characterizations further explored the dynamic change of W valence state during LiPSs redox cycle. Encouragingly, the WB@WC-modified Li–S cell delivers an initial capacity of 1277 mAh g ⁻¹ at 0.2 C. It exhibits extremely stable cycling performance at 2 C, with a low-capacity decay rate of only ~ 0.024% per cycle. Even under sulfur loading of 7.92 mg cm ⁻² , high capacity of 7.9 mAh cm ⁻² can still be achieved. This work provides an effective method for regulating the activity of MBene-based catalysts.

The practical application of the sulfur cathode in lithium–sulfur (Li–S) batteries mainly depends on the suppression of lithium polysulfide (LiPSs) diffusion and the improvement of its kinetics. Efficient 2D adsorption‐catalytic media are an important direction for its future progress. Herein, the ultrathin (~2.2 nm) Fe ₂ O ₃ ‐Fe ₃ O ₄ heterointerface is rapidly synthesized. As an adsorption and catalytic medium for LiPSs, it exhibits a stronger LiPS affinity than the single‐component Fe ₃ O ₄ and Fe ₂ O ₃ . The built‐in electric field at the heterogeneous interface can significantly enhance the kinetics of charge transfer. It provides a positive regulatory effect on the smooth “adsorption‐migration‐conversion” process of active sulfur species. Both theoretical calculations and in situ Raman have verified its performance enhancement mechanism. As a result, the cell based on this heterointerface achieves reversible capacities of up to 737 mAh·g ⁻¹ at 4 C. A high capacity retention of 493 mAh·g ⁻¹ is maintained after 500 cycles at 2 C. Even under a high sulfur load of 4.2 mg·cm ⁻² , an area capacity of 6.1 mAh·cm ⁻² can still be obtained, with stable cycling maintained for dozens of cycles.

The sluggish kinetics and diffusion of lithium polysulfide (LiPS) intermediates lead to the decline in the capacity and rate of high-energy lithium-sulfur (Li-S) batteries. Integrating adsorbents and electrocatalysts into the Li-S system is an effective strategy for suppressing the polysulfide shuttle and enhancing the redox kinetics of sulfur species. The disordered structure of the electrocatalysts exhibits significantly enhanced catalytic activity. By inducing more oxygen vacancies, this structure can not only effectively promote the adsorption behavior of LiPSs but also significantly enhance the intrinsic catalytic activity of the Li₂S product nucleation. Herein, an amorphous iron oxide-graphene oxide (FeO_x-GO) ultrathin nanosheet was developed for the adsorption and catalysis of LiPSs. Experiments showed that the FeO_x-GO-based cell exhibited excellent rate performance: a reversible capacity of 880 mAh g^-1 at 2C, along with ultralow capacity decay (a decay rate of only 0.08% per cycle). More notably, it demonstrated a stable performance under high sulfur loading conditions, achieving a high areal capacity of 5.5 mAh cm^-2. The synergistic effect at the FeO_x-GO interface optimized the electronic structure of active sites and adsorption energy barriers, facilitating the efficient acceleration of rapid redox reactions.

The shuttle effect of lithium polysulfides (LiPSs) and the slow conversion kinetics of sulfur have been hindering the commercial development of lithium–sulfur (Li–S) batteries. Herein, WB‐V _B based 2Dl MBene catalyst containing B vacancies is successfully prepared by a one‐step room temperature F‐free etching method. Both W and B atoms in this catalyst can interact with LiPSs simultaneously, effectively inhibiting the diffusion of soluble LiPSs. B‐vacancy construction not only provides more exposure of active site W, but also improves the d band center, which is conducive to the rapid adsorption and Li–S reaction kinetics. More importantly, its mechanism for catalyzing LiPS reaction is characterized by in situ X‐ray absorption spectroscopy. The results show that the reversible capacity is as high as 1485 mAh g ⁻¹ at 0.2 C, and 664 mAh g ⁻¹ even at 4 C. Furthermore, an outstanding capacity of 4.15 mAh cm ⁻² under high load of 4.36 mg cm ⁻² has remarkable cyclic stability.

Aqueous Zn–metal batteries have attracted wide attention due to the abundant Zn reserves and the safety and non-toxicity of aqueous electrolytes, and have become a research hotspot in the field of electrochemical energy.

A 2D MoB-based MBene substrate used for MnO ₂ loading is conducive to the stability and kinetic reaction of aqueous Zn-ion batteries.

Lithium-sulfur (Li-S) batteries hold the potential to revolutionize energy storage due to the high theoretical capacity and energy density. However, the commercialization process is seriously hindered by the rapid capacity decay and low utilization of sulfur, caused by the inevitable slow dynamics and the “shuttle effect”. The incorporation of metal-based electrocatalysts into sulfur cathodes shows promise in promoting the conversion of lithium polysulfides (LiPSs), reducing the “shuttle effect”, and enhancing cell kinetics and cycle life. Among these, Fe-based materials, characterized by environmental friendliness, low cost, abundant reserves, and high activity, are extensively used in sulfur cathode modification. This article reviews the advancements of Fe-based materials in enhancing Li-S batteries in recent years. Starting from single/multi-component Fe-based metal compounds and single/bimetallic atoms, the influence of different Fe coordination environments on the conversion mechanism of LiPSs is analyzed. It is hoped that this review and the proposed prospects can further stimulate the development and application of the Fe element in Li-S batteries in the future.