Molecular Electrocatalysts in Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries face challenges due to the sluggish reaction kinetics of sulfur species, which reduces sulfur utilization and thus lowers performance. Molecular electrocatalysts, with their clear and adequately exposed active sites, offer a reliable way to enhance reaction kinetics in lithium-sulfur batteries. This review elaborates on the reaction processes and mechanisms of molecular electrocatalysts, focusing on both the sulfur reduction reaction (SRR) and sulfur evolution reaction (SER) to explore their potential working principles.

Fence-Type Molecular Electrocatalysts for High-Performance Lithium-Sulfur Batteries.

Improving the slow redox kinetics of sulfur species and shuttling issues of soluble intermediates induced from the multiphase sulfur redox reactions are crucial factors for developing the next-generation high-energy-density lithium-sulfur (Li-S) batteries. In this study, we successfully constructed a novel molecular electrocatalyst through in situ polymerization of bis(3,4-dibromobenzene)-18-crown-6 (BD18C6) with polysulfide anions on the cathode interface. The crown ether (CE)-based polymer acts as a spatial "fence" to precisely control the unique redox characteristics of sulfur species, which could confine sulfur substance within its interior and interact with lithium polysulfides (LiPSs) to optimize the reaction barrier of sulfur species.

Undercoordination Chemistry of Sulfur Electrocatalyst in Lithium-Sulfur Batteries.

Undercoordination chemistry is an effective strategy to modulate the geometry-governed electronic structure and thereby regulate the activity of sulfur electrocatalysts. Efficient sulfur electrocatalysis is requisite to overcome the sluggish kinetics in lithium-sulfur (Li-S) batteries aroused by multi-electron transfer and multi-phase conversions. Recent advances unveil the great promise of undercoordination chemistry in facilitating and stabilizing sulfur electrochemistry, yet a related review with systematicness and perspectives is still missing.

Dually Sulphophilic Chromium Boride Nanocatalyst Boosting Sulfur Conversion Kinetics Toward High-Performance Lithium-Sulfur Batteries.

The sluggish kinetics of sulfur conversions have long been hindering the implementation of fast and efficient sulfur electrochemistry in lithium-sulfur (Li-S) batteries. In this regard, herein the unique chromium boride (CrB) is developed via a well-confined mild-temperature thermal reaction to serve as an advanced sulfur electrocatalyst. Its interstitial-alloy nature features excellent conductivity, while the nano-lamination architecture affords abundant active sites for host-guest interactions.

Uncoordinated chemistry enables highly conductive and stable electrolyte/filler interfaces for solid-state lithium-sulfur batteries.

Composite-polymer-electrolytes (CPEs) embedded with advanced filler materials offer great promise for fast and preferential Li conduction. The filler surface chemistry determines the interaction with electrolyte molecules and thus critically regulates the Li behaviors at the interfaces. Herein, we probe into the role of electrolyte/filler interfaces (EFI) in CPEs and promote Li conduction by introducing an unsaturated coordination Prussian blue analog (UCPBA) filler.

"Tree-Trunk" Design for Flexible Quasi-Solid-State Electrolytes with Hierarchical Ion-Channels Enabling Ultralong-Life Lithium-Metal Batteries.

The construction of robust (quasi)-solid-state electrolyte (SSE) for flexible lithium-metal batteries is desirable but extremely challenging. Herein, a novel, flexible, and robust quasi-solid-state electrolyte (QSSE) with a "tree-trunk" design is reported for ultralong-life lithium-metal batteries (LMBs). An in-situ-grown metal-organic framework (MOF) layer covers the cellulose-based framework to form hierarchical ion-channels, enabling rapid ionic transfer kinetics and excellent durability.

Interspersing Partially Oxidized VC Nanosheets and Carbon Nanotubes toward Multifunctional Polysulfide Barriers for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have attracted much attention attributed to their high theoretical energy density, whereas the parasitic shuttling behavior of lithium polysulfides (LiPS) hinders this technology from yielding practically competitive performance. Targeting this critical challenge, we develop an advanced polysulfide barrier by modifying the conventional separator with CNTs-interspersed VC/VO nanosheets to alleviate the shuttle effect. The partial oxidization of VC MXene constructs the VC/VO composite with VO nanoparticles uniformly dispersed on few-layered VC nanosheets, which synergistically and concurrently improves the sulfur confinement and redox reaction kinetics.

Porous Carbon Nanosheets Armoring 3D Current Collectors toward Ultrahigh Mass Loading for High-Energy-Density All-Solid-State Supercapacitors.

The in situ growth of active materials on 3D current collectors (such as Ni foams) presents facile and efficient access to high-performance supercapacitors. However, the low surface area of current collectors limits the mass loading, microstructure, and capacitive performance of active materials thereon. Herein, we develop a novel surface modification with hierarchical N-rich carbon nanosheets on Ni foams via a simple sol-gel method.

Hierarchical Micro-Nanoclusters of Bimetallic Layered Hydroxide Polyhedrons as Advanced Sulfur Reservoir for High-Performance Lithium-Sulfur Batteries.

Rational construction of sulfur electrodes is essential in pursuit of practically viable lithium-sulfur (Li-S) batteries. Herein, bimetallic NiCo-layered double hydroxide (NiCo-LDH) with a unique hierarchical micro-nano architecture is developed as an advanced sulfur reservoir for Li-S batteries. Compared with the monometallic Co-layered double hydroxide (Co-LDH) counterpart, the bimetallic configuration realizes much enriched, miniaturized, and vertically aligned LDH nanosheets assembled in hollow polyhedral nanoarchitecture, which geometrically benefits the interface exposure for host-guest interactions.

Constructing multifunctional solid electrolyte interface via in-situ polymerization for dendrite-free and low N/P ratio lithium metal batteries.

Stable solid electrolyte interface (SEI) is highly sought after for lithium metal batteries (LMB) owing to its efficient electrolyte consumption suppression and Li dendrite growth inhibition. However, current design strategies can hardly endow a multifunctional SEI formation due to the non-uniform, low flexible film formation and limited capability to alter Li nucleation/growth orientation, which results in unconstrained dendrite growth and short cycling stability. Herein, we present a novel strategy to employ electrolyte additives containing catechol and acrylic groups to construct a stable multifunctional SEI by in-situ anionic polymerization.

Regulating the Li -Solvation Structure of Ester Electrolyte for High-Energy-Density Lithium Metal Batteries.

The development of high-energy-density Li metal batteries are hindered by electrolyte consumption and uneven lithium deposition due to the unstable lithium-electrolyte interface (SEI). In this work, tetraglyme is introduced into ester electrolyte to regulate the Li -solvation structures for stable SEI while remaining appropriate voltage window for high-voltage cathodes. In the modified solvation structures, an enhanced lowest unoccupied molecular orbital energy level occurs, resulting in relieved electrolyte degradation.

Engineering Solvation Complex-Membrane Interaction to Suppress Cation Crossover in 3 V Cu-Al Battery.

Metal-metal batteries such as the 3 V Cu-Al system are highly desirable for large-scale energy storage owing to their low cost and excellent scalability of Cu and Al foils. However, the dissolved Cu cations will crossover from the cathode to the anode leading to poor electrochemical performance. In this work, it is demonstrated that the reversibility of the Cu-Al battery depends strongly on the interaction of the Cu ions with the electrolyte solvent and subsequently the affinity of the solvated Cu ion with the membrane separator.

Revealing the Rapid Electrocatalytic Behavior of Ultrafine Amorphous Defective NbO Nanocluster toward Superior Li-S Performance.

The notorious shuttling behaviors and sluggish conversion kinetics of the intermediate lithium polysulfides (LPS) are hindering the practical application of lithium sulfur (Li-S) batteries. Herein, an ultrafine, amorphous, and oxygen-deficient niobium pentoxide nanocluster embedded in microporous carbon nanospheres (A-NbO@MCS) was developed as a multifunctional sulfur immobilizer and promoter toward superior shuttle inhibition and conversion catalyzation of LPS. The A-NbO nanocluster implanted framework uniformizes sulfur distribution, exposes vast active interfaces, and offers a reduced ion/electron transportation pathway for expedited redox reaction.

Polysulfide Regulation by the Zwitterionic Barrier toward Durable Lithium-Sulfur Batteries.

Rational regulation on polysulfide behaviors is of great significance in pursuit of reliable solution-based lithium-sulfur (Li-S) battery chemistry. Herein, we develop a unique polymeric zwitterion (PZI) to establish a smart polysulfide regulation in Li-S batteries. The zwitterionic nature of PZI integrates sulfophilicity and lithiophilicity in the matrix, fostering an ionic environment for selective ion transfer through the chemical interactions with lithium polysulfides (LiPS).

Engineering Energy Level of Metal Center: Ru Single-Atom Site for Efficient and Durable Oxygen Reduction Catalysis.

Emerging as a new frontier in heterogeneous catalysis, single-atom site catalysts (SSCs) have sparked enormous attention and bring about new opportunities to oxygen reduction electrocatalysis. Despite considerable progress achieved recently, most of the reported SSCs suffer from either insufficient activity or unsatisfactory stability, which severely retards their practical application. Here, we demonstrate a novel Ru-SSC with appropriate adsorption free energy of OH* (Δ) to confer excellent activity and low Fenton reactivity to maintain long-term stability.

Low-Bandgap Se-Deficient Antimony Selenide as a Multifunctional Polysulfide Barrier toward High-Performance Lithium-Sulfur Batteries.

The shuttling behavior and sluggish conversion kinetics of the intermediate lithium polysulfides (LiPSs) represent the main obstructions to the practical application of lithium-sulfur (Li-S) batteries. Herein, an anion-deficient design of antimony selenide (Sb Se ) is developed to establish a multifunctional LiPS barrier toward the inhibition of polysulfide shuttling and enhancement of battery performance. The defect chemistry in the as-developed Sb Se promotes the intrinsic conductivity, strengthens the chemical affinity to LiPSs, and catalyzes the sulfur electrochemical conversion, which are verified by a series of computational and experimental results.

Defect-Enriched Nitrogen Doped-Graphene Quantum Dots Engineered NiCo S Nanoarray as High-Efficiency Bifunctional Catalyst for Flexible Zn-Air Battery.

Flexible Zn-air batteries have recently emerged as one of the key energy storage systems of wearable/portable electronic devices, drawing enormous attention due to the high theoretical energy density, flat working voltage, low cost, and excellent safety. However, the majority of the previously reported flexible Zn-air batteries encounter problems such as sluggish oxygen reaction kinetics, inferior long-term durability, and poor flexibility induced by the rigid nature of the air cathode, all of which severely hinder their practical applications. Herein, a defect-enriched nitrogen doped-graphene quantum dots (N-GQDs) engineered 3D NiCo S nanoarray is developed by a facile chemical sulfuration and subsequent electrophoretic deposition process.

A Single-Atom Iridium Heterogeneous Catalyst in Oxygen Reduction Reaction.

Combining the advantages of homogeneous and heterogeneous catalysts, single-atom catalysts (SACs) are bringing new opportunities to revolutionize ORR catalysis in terms of cost, activity and durability. However, the lack of high-performance SACs as well as the fundamental understanding of their unique catalytic mechanisms call for serious advances in this field. Herein, for the first time, we develop an Ir-N-C single-atom catalyst (Ir-SAC) which mimics homogeneous iridium porphyrins for high-efficiency ORR catalysis.

2D molybdenum nitride nanosheets as anode materials for improved lithium storage.

Two-dimensional (2D) molybdenum nitride (MoN) nanosheets are promising anode materials for improved lithium-ion batteries. However, the reported synthesis methods of MoN generally rely on high-temperature and complex procedures with low cost efficiency. Herein, we report a facile one-pot synthesis of 2D MoN nanosheets at a low temperature of 400 °C via a solid-state reaction of molybdenum disulfide, sulfur and sodium amide in an autoclave.

Exploring Chemical, Mechanical, and Electrical Functionalities of Binders for Advanced Energy-Storage Devices.

Tremendous efforts have been devoted to the development of electrode materials, electrolytes, and separators of energy-storage devices to address the fundamental needs of emerging technologies such as electric vehicles, artificial intelligence, and virtual reality. However, binders, as an important component of energy-storage devices, are yet to receive similar attention. Polyvinylidene fluoride (PVDF) has been the dominant binder in the battery industry for decades despite several well-recognized drawbacks, i.

Revisiting the Role of Polysulfides in Lithium-Sulfur Batteries.

Intermediate polysulfides (S , where n = 2-8) play a critical role in both mechanistic understanding and performance improvement of lithium-sulfur batteries. The rational management of polysulfides is of profound significance for high-efficiency sulfur electrochemistry. Here, the key roles of polysulfides are discussed, with regard to their status, behavior, and their correspondingimpact on the lithium-sulfur system.

Tuning Shell Numbers of Transition Metal Oxide Hollow Microspheres toward Durable and Superior Lithium Storage.

Multishelled hollow structured transition metal oxides (TMOs) are highly potential materials for high energy density energy storage due to their high volumetric energy density, reduced aggregation of nanosized subunits, and excellent capacity and durability. However, traditional synthetic methods of TMOs generally require complicated steps and lack compositional/morphological adjustability. Herein, a general and straightforward strategy is developed to synthesize multishelled porous hollow microspheres, which is constituted of nanosize primary TMO particles, using metal acetate polysaccharide microspheres as the precursor.

A facile self-templating synthesis of carbon frameworks with tailored hierarchical porosity for enhanced energy storage performance.

Herein, we present a facile synthesis of hierarchical carbon frameworks with microporous skeletons and interconnected meso/macropores by employing poly(vinylidene chloride-co-methyl acrylate)-b-polystyrene copolymers as precursors. The obtained porosity can be tuned over a broad range via well-selected block proportions of the precursor, enabling its advantageous applications in target-oriented energy storage systems.