Precise solid-phase synthesis of CoFe@FeOx nanoparticles for efficient polysulfide regulation in lithium/sodium-sulfur batteries

Nanorobot Swarms Made with Laser-Induced Graphene@Fe3O4 Nanoparticles with Controllable Morphology for Targeted Drug Delivery

Magnetic nanorobot swarms can mimic group behaviors in nature and can be flexibly controlled by programmable magnetic fields, thereby having great potential in various applications. This paper presents a novel approach for the rapid and large-scale processing of laser-induced graphene (LIG) @Fe3O4-based-nanorobot swarms utilizing one-step UV laser processing technology. The swarm is capable of forming a variety of reversible morphologies under the magnetic field, including vortex-like and strip-like, as well as the interconversion of these, demonstrating high levels of controllability and flexibility. Moreover, the maximum forward motion speed of the nanorobot swarm is up to 2165 μm/s, and the drug loading and release ability of such a nanorobot swarm is enhanced about 50 times due to the presence of graphene, enabling the nanorobot swarm to show rapid and precise targeted drug delivery. Importantly, by controllable morphology transformation to conform to the complicated requirements for the magnetic field, the drug-loaded swarm can smoothly pass through a width-varying zigzag channel while maintaining 96% of the initial drug-loading, demonstrating that LIG @Fe3O4 NPs-based nanorobot swarm can provide effective and controllable targeted drug delivery in complex passages.

Amorphous FeSnOx Nanosheets with Hierarchical Vacancies for Room-Temperature Sodium-Sulfur Batteries

Room-temperature sodium-sulfur (RT Na-S) batteries, noted for their low material costs and high energy density, are emerging as a promising alternative to lithium-ion batteries (LIBs) in various applications including power grids and standalone renewable energy systems. These batteries are commonly assembled with glass fiber membranes, which face significant challenges like the dissolution of polysulfides, sluggish sulfur conversion kinetics, and the growth of Na dendrites. Here, we develop an amorphous two-dimensional (2D) iron tin oxide (A-FeSnOx) nanosheet with hierarchical vacancies, including abundant oxygen vacancies (Ovs) and nano-sized perforations, that can be assembled into a multifunctional layer overlaying commercial separators for RT Na-S batteries. The Ovs offer strong adsorption and abundant catalytic sites for polysulfides, while the defect concentration is finely tuned to elucidate the polysulfides conversion mechanisms. The nano-sized perforations aid in regulating Na ions transport, resulting in uniform Na deposition. Moreover, the strategic addition of trace amounts of Ti3C2 (MXene) forms an amorphous/crystalline (A/C) interface that significantly improves the mechanical properties of the separator and suppresses dendrite growth. As a result, the task-specific layer achieves ultra-light (~0.1 mg cm-2), ultra-thin (~200 nm), and ultra-robust (modulus=4.9 GPa) characteristics. Consequently, the RT Na-S battery maintained a high capacity of 610.3 mAh g-1 and an average Coulombic efficiency of 99.9 % after 400 cycles at 0.5 C.

"Bowling Collision Effect" of CoMo6 Polyoxometalate Units Enables Wide Temperature Range from -20 to 60 °C and Dendrite Mitigation Li-S Batteries

To improve the performance of Lithium-Sulfur (Li-S) batteries, the reaction catalysts of lithium polysulfides (LiPSs) reactions should have the characteristics of large surface area, efficient atomic utilization, high conductivity, small size, good stability, and strong adjustability. Herein, Anderson-type polyoxometalate ([TMMo6O24]n-, TM = Co, Ni, Fe, represented by TMMo6 POMs) are used as the modified materials for Li-S battery separator. By customizing the central metal atoms, this work gains insights into the layer-by-layer electron transfer mechanism between TMMo6 units and LiPSs, similar to the collision effect of a bowling ball. Theoretical analysis and in situ experimental characterization show that the changes of CoMo6 units with moderate binding energy and lowest Gibbs free energy result in the formation of robust polar bonds and prolonged S─S bonds after adsorption. Hence, the representative Li-S battery with CoMo6 and graphene composite modified separator has a high initial capacity of 1588.6 mA h g-1 at 0.2 C, excellent cycle performance of more than 3000 cycles at 5 C, and uniform Li+ transport over 1900 h. More importantly, this work has revealed the inherent contradiction between the kinetics and thermodynamics, achieving a stable cycle in the temperature range of -20 to 60 °C.

Dependence of Interlayer or Sulfur Host on Hollow Framework of Lithium-Sulfur Battery

Lithium-sulfur batteries are recognized as the next generation of high-specific energy secondary batteries owing to their satisfactory theoretical specific capacity and energy density. However, their commercial application is greatly limited by a series of problems, including disordered migration behavior, sluggish redox kinetics, and the serious shuttle effect of lithium polysulfides. One of the most efficient approaches to physically limit the shuttle effect is the rational design of a hollow framework as sulfur host. However, the influence of the hollow structure on the interlayers has not been clearly reported. In this study, the Mo2C/C catalysts with hollow(H-Mo2C/C) and solid(S-Mo2C/C) frameworks are rationally designed to explore the dependence of the hollow structure on the interlayer or sulfur host. In contrast to the physical limitations of the hollow framework as host, the hollow structure of the interlayer inhibited lithium-ion diffusion, resulting in poor electrochemical properties at high current densities. Based on the superiority of the various frameworks, the H-Mo2C/C@S | S-Mo2C/C@PP | Li cells are assembled and displayed excellent electrochemical performance. This work re-examines the design requirements and principles of catalyst frameworks in different battery units.

Atom-Level Tandem Catalysis in Lithium Metal Batteries

High-energy-density lithium metal batteries (LMBs) are limited by reaction or diffusion barriers with dissatisfactory electrochemical kinetics. Typical conversion-type lithium sulfur battery systems exemplify the kinetic challenges. Namely, before diffusing or reacting in the electrode surface/interior, the Li(solvent)x + dissociation at the interface to produce isolated Li+, is usually a prerequisite fundamental step either for successive Li+ "reduction" or for Li+ to participate in the sulfur conversions, contributing to the related electrochemical barriers. Thanks to the ideal atomic efficiency (100 at%), single atom catalysts (SACs) have gained attention for use in LMBs toward resolving the issues caused by the five types of barrier-restricted processes, including polysulfide/Li2S conversions, Li(solvent)x + desolvation, and Li0 nucleation/diffusion. In this perspective, the tandem reactions including desolvation and reaction or plating and corresponding catalysis behaviors are introduced and analyzed from interface to electrode interior. Meanwhile, the principal mechanisms of highly efficient SACs in overcoming specific energy barriers to reinforce the catalytic electrochemistry are discussed. Lastly, the future development of high-efficiency atomic-level catalysts in batteries is presented.

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.