Expediting Sulfur Reduction/Evolution Reactions with Integrated Electrocatalytic Network: A Comprehensive Kinetic Map

Molecular Intercalation Enables Phase Transition of MoSe2 for Durable Na-Ion Storage

1T-MoSe2 is recognized as a promising anode material for sodium-ion batteries, thanks to its excellent electrical conductivity and large interlayer distance. However, its inherent thermodynamic instability often presents unparalleled challenges in phase control and stabilization. Here, a molecular intercalation strategy is developed to synthesize thermally stable 1T-rich MoSe2, covalently bonded to an intercalated carbon layer (1TR/2H-MoSe2@C). Density functional theory calculations uncover that the introduced ethylene glycol molecules not only serve as electron donors, inducing a reorganization of Mo 4d orbitals, but also as sacrificial guest materials that generate a conductive carbon layer. Furthermore, the C─Se/C─O─Mo bonds encourage strong interfacial electronic coupling, and the carbon layer prevents the restacking of MoSe2, regulating the maximum 1T phase to an impressive 80.3%. Consequently, the 1TR/2H-MoSe2@C exhibits an extraordinary rate capacity of 326 mAh g-1 at 5 A g-1 and maintains a long-term cycle stability up to 1500 cycles, with a capacity of 365 mAh g-1 at 2 A g-1. Additionally, the full cell delivers an appealing energy output of 194 Wh kg-1 at 208 W kg-1, with a capacity retention of 87.3% over 200 cycles. These findings contribute valuable insights toward the development of innovative transition metal dichalcogenides for next-generation energy storage technologies.

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.

Conformal 3D Li/Li13Sn5 Scaffolds Anodes for High-Areal Energy Density Flexible Lithium Metal Batteries

Achieving a high depth of discharge (DOD) in lithium metal anodes (LMAs) is crucial for developing high areal energy density batteries suitable for wearable electronics. Yet, the persistent growth of dendrites compromises battery performance, and the significant lithium consumption during pre-lithiation obstructs their broad application. Herein, A flexible 3D Li13Sn5 scaffold is designed by allowing molten lithium to infiltrate carbon cloth adorned with SnO2 nanocrystals. This design markedly curbs the troublesome dendrite growth, thanks to the uniform electric field distribution and swift Li+ diffusion dynamics. Additionally, with a minimal SnO2 nanocrystals loading (2 wt.%), only 0.6 wt.% of lithium is consumed during pre-lithiation. Insights from in situ optical microscope observations and COMSOL simulations reveal that lithium remains securely anchored within the scaffold, a result of the rapid mass/charge transfer and uniform electric field distribution. Consequently, this electrode achieves a remarkable DOD of 87.1% at 10 mA cm-2 for 40 mAh cm-2. Notably, when coupled with a polysulfide cathode, the constructed flexible Li/Li13Sn5@CC||Li2S6/SnO2@CC pouch cell delivers a high-areal capacity of 5.04 mAh cm-2 and an impressive areal-energy density of 10.6 mWh cm-2. The findings pave the way toward the development of high-performance LMAs, ideal for long-lasting wearable electronics.

Bottom-Up Magnesium Deposition Induced by Paper-Based Triple-Gradient Scaffolds toward Flexible Magnesium Metal Batteries

The development of advanced magnesium metal batteries (MMBs) has been hindered by longstanding challenges, such as the inability to induce uniform magnesium (Mg) nucleation and the inefficient utilization of Mg foil. This study introduces a novel solution in the form of a flexible, lightweight, paper-based scaffold that incorporates gradient conductivity, magnesiophilicity, and pore size. This design is achieved through an industrially adaptable papermaking process in which the ratio of carboxylated multi-walled carbon nanotubes to softwood cellulose fibers is meticulously adjusted. The triple-gradient structure of the scaffold enables the regulation of Mg ion flux, promoting bottom-up Mg deposition. Owing to its high flexibility, low thickness, and reduced density, the scaffold has potential applications in flexible and wearable electronics. Accordingly, the triple-gradient electrodes exhibit stable operation for over 1200 h at 3 mA cm-2 /3 mAh cm-2 in symmetrical cells, markedly outperforming the non-gradient and metallic Mg alternatives. Notably, this study marks the first successful fabrication of a flexible MMB pouch full cell, achieving an impressive volumetric energy density of 244 Wh L-1 . The simplicity and scalability of the triple-gradient design, which uses readily available materials through an industrially compatible papermaking process, open new doors for the production of flexible, high-energy-density metal batteries.

RuOx Quantum Dots Loaded on Graphdiyne for High-Performance Lithium-Sulfur Batteries

Here, a strategy to strengthen d-p orbital hybridization by fabricating π backbonding in the catalyst for efficient lithium polysulfides (LiPSs) conversion is reported. A special interface structure of RuOx quantum dots (QDs) anchored on graphdiyne (GDY) nanoboxes (RuOx QDs/GDY) is prepared to enable strong Ru-to-alkyne π backdonation, which effectively regulates the d-electron structures of Ru centers to promote the d-p orbital hybridization between the catalyst and LiPSs and significantly boosts the catalytic performance of RuOx QDs/GDY. The strong affinity with Li ions and fast Li-ion diffusion of RuOx QDs/GDY also enable ultrastable Li metal anodes. Thus, S@RuOx QDs/GDY cathodes exhibit excellent cycling performance under harsh conditions, and Li@RuOx QDs/GDY anodes show an ultralong cycling life over 8800 h without Li dendrite growth. Lithium-sulfur (Li-S) full cells with S@RuOx QDs/GDY cathodes and Li@RuOx QDs/GDY anodes can deliver an impressive areal capacity of 17.8 mA h cm-2 and good cycling stability under the practical conditions of low negative-to-positive electrode capacity (N/P) ratio (N/P = 1.4), lean electrolyte (E/S = 3 µL mg-1 ), and high S mass loading (15.4 mg cm-2 ).

Sustainable release of LiNO3 in carbonate electrolytes for stable lithium metal anodes

LiNO3 is recognized as an effective additive, forming a dense, nitrogen-rich solid electrolyte interphase (SEI) on lithium's surface, which safeguards it from parasitic reactions. However, its use is limited due to the poor solubility in carbonate electrolytes. Herein, we introduce a bilayer separator designed to release LiNO3 sustainably. This continual release not only alters the chemistry of the SEI but also replenishes the additives that are depleted during battery cycling, thereby enhancing the durability of the modified interphase. This strategy effectively curtails Li dendrite formation, significantly enhancing the longevity of Li|LiFePO4 batteries, evidenced by an impressive 85% capacity retention after 800 cycles. This research offers a compelling remedy to the longstanding challenge of incorporating LiNO3 in carbonate electrolytes.

Li+ mobility powered by a crystal compound for fast Li-S chemistry

Placing blocking layers between electrodes has shown paramount prospects in suppressing the shuttle effect of Li-S batteries, but the associated ionic transport would be a concurrent obstacle. Herein, we present a Li-based crystal composited with carbon (LiPN2@C) by a one-step annealing of Li+ absorbed melamine polyphosphate, which simultaneously achieves alleviated polysulfide-shuttling and facilitated Li+ transport. As a homologous crystal, LiPN2 with abundant lithiophilic sites makes Li+ transport more efficient and sustainable. With a LiPN2@C-modified separator, the Li2S cathode exhibits a much-lower activation potential of 2.4 V and a high-rate capacity of 519 mA h g-1 at 2C. Impressively, the battery delivers a capacity of 726 mA h g-1 at 0.5C with a low decay rate of 0.25% per cycle during 100 continuous cycles.

Fast-Charging Sodium-Ion Batteries Enabled by Molecular-Level Designed Nitrogen and Phosphorus Codoped Mesoporous Soft Carbon

Soft carbons have attracted extensive interests as competitive anodes for fast-charging sodium-ion batteries (SIBs); however, the high-rate performance is still restricted by their large ion migration barriers and sluggish reaction kinetics. Herein, we show a molecular design approach toward the fabrication of nitrogen and phosphorus codoped mesoporous soft carbon (NPSC). The key to this strategy lies in the chemical cross-linking reaction between polyphosphoric acid and p-phenylenediamine, associated with pyrolysis induced in-situ self-activation that creates mesoporous structures and rich heteroatoms within the carbon matrix. Thanks to the enlarged interlayer spacing, reduced ion diffusion length, and plentiful active sites, the obtained NPSC delivers a superb rate capacity of 215 mAh g-1 at 10 A g-1 and an ultralong cycle life of 4,700 cycles at 5 A g-1. Remarkably, the full cell shows 99% capacity retention during 100 continuous cycles, and maximum energy and power densities of 191 Wh kg-1 and 9.2 kW kg-1, respectively. We believe that such a synthetic protocol could pave a novel venue to develop soft carbons with unique properties for advanced SIBs.

Integrated Gradient Cu Current Collector Enables Bottom-Up Li Growth for Li Metal Anodes: Role of Interfacial Structure

3D Cu current collectors have been demonstrated to improve the cycling stability of Li metal anodes, however, the role of their interfacial structure for Li deposition pattern has not been investigated thoroughly. Herein, a series of 3D integrated gradient Cu-based current collectors are fabricated by the electrochemical growth of CuO nanowire arrays on Cu foil (CuO@Cu), where their interfacial structures can be readily controlled by modulating the dispersities of the nanowire arrays. It is found that the interfacial structures constructed by sparse and dense dispersion of CuO nanowire arrays are both disadvantageous for the nucleation and deposition of Li metal, consequently fast dendrite growth. In contrast, a uniform and appropriate dispersity of CuO nanowire arrays enables stable bottom Li nucleation associated with smooth lateral deposition, affording the ideal bottom-up Li growth pattern. The optimized CuO@Cu-Li electrodes exhibit a highly reversible Li cycling including a coulombic efficiency of up to ≈99% after 150 cycles and a long-term lifespan of over 1200 h. When coupling with LiFePO4 cathode, the coin and pouch full-cells deliver outstanding cycling stability and rate capability. This work provides a new insight to design the gradient Cu current collectors toward high-performance Li metal anodes.

Boosting Lean Electrolyte Lithium-Sulfur Battery Performance with Transition Metals: A Comprehensive Review

Lithium-sulfur (Li-S) batteries have received widespread attention, and lean electrolyte Li-S batteries have attracted additional interest because of their higher energy densities. This review systematically analyzes the effect of the electrolyte-to-sulfur (E/S) ratios on battery energy density and the challenges for sulfur reduction reactions (SRR) under lean electrolyte conditions. Accordingly, we review the use of various polar transition metal sulfur hosts as corresponding solutions to facilitate SRR kinetics at low E/S ratios (< 10 µL mg-1), and the strengths and limitations of different transition metal compounds are presented and discussed from a fundamental perspective. Subsequently, three promising strategies for sulfur hosts that act as anchors and catalysts are proposed to boost lean electrolyte Li-S battery performance. Finally, an outlook is provided to guide future research on high energy density Li-S batteries.

Engineering the First Coordination Shell of Single Zn Atoms via Molecular Design Strategy toward High-Performance Sodium-Ion Hybrid Capacitors

Atomically dispersed Zn moieties are efficient active sites for accelerating the electrode kinetics of carbons for sodium-ion hybrid capacitors (SIHCs), but the low utilization and symmetric configuration of Zn single-atom greatly hamper the Na ion storage capability. Herein, a molecular design strategy is employed to synthesize high-density Zn single atoms with asymmetric Zn-N₃ S coordination embedded in nitrogen/sulfur codoped carbon (Zn-N₃ S-NSC). The key to this strategy lies in the Zn power-catalyzed condensation of trithiocyanuric acid molecules to generate S-doped g-C₃ N₄ , which can in situ coordinate with Zn sources to form Zn-N₃ S moieties during pyrolysis. By virtue of the highly exposed Zn-N₃ S moieties, Zn-N₃ S-NSC presents ultrahigh reactivity, efficient electron transfer, and decreased ion diffusion barriers for SIHCs, rendering an impressive energy density of 215 Wh kg^-1 and a maximum power density of 15625 W kg^-1 . Moreover, the pouch cell displays a high capacity of 279 mAh g^-1 after 4000 cycles. This work provides a new avenue for the regulation of the coordination configuration of single metal atoms in carbons toward high-performance electrochemical energy technologies at the molecular level.

On the Road to the Frontiers of Lithium-Ion Batteries: A Review and Outlook of Graphene Anodes

Graphene has long been recognized as a potential anode for next-generation lithium-ion batteries (LIBs). The past decade has witnessed the rapid advancement of graphene anodes, and considerable breakthroughs are achieved so far. In this review, the aim is to provide a research roadmap of graphene anodes toward practical LIBs. The Li storage mechanism of graphene is started with and then the approaches to improve its electrochemical performance are comprehensively summarized. First, morphologically engineered graphene anodes with porous, spheric, ribboned, defective and holey structures display improved capacity and rate performance owing to their highly accessible surface area, interconnected diffusion channels, and sufficient active sites. Surface-modified graphene anodes with less aggregation, fast electrons/ions transportation, and optimal solid electrolyte interphase are discussed, demonstrating the close connection between the surface structure and electrochemical activity of graphene. Second, graphene derivatives anodes prepared by heteroatom doping and covalent functionalization are outlined, which show great advantages in boosting the Li storage performances because of the additionally introduced defect/active sites for further Li accommodation. Furthermore, binder-free and free-standing graphene electrodes are presented, exhibiting great prospects for high-energy-density and flexible LIBs. Finally, the remaining challenges and future opportunities of practically available graphene anodes for advanced LIBs are highlighted.

Interface Engineering Toward Expedited Li2 S Deposition in Lithium-Sulfur Batteries: A Critical Review

Lithium-sulfur batteries (LSBs) with superior energy density are among the most promising candidates of next-generation energy storage techniques. As the key step contributing to 75% of the overall capacity, Li₂ S deposition remains a formidable challenge for LSBs applications because of its sluggish kinetics. The severe kinetic issue originates from the huge interfacial impedances, indicative of the interface-dominated nature of Li₂ S deposition. Accordingly, increasing efforts have been devoted to interface engineering for efficient Li₂ S deposition, which has attained inspiring success to date. However, a systematic overview and in-depth understanding of this critical field are still absent. In this review, the principles of interface-controlled Li₂ S precipitation are presented, clarifying the pivotal roles of electrolyte-substrate and electrolyte-Li₂ S interfaces in regulating Li₂ S depositing behavior. For the optimization of the electrolyte-substrate interface, efforts on the design of substrates including metal compounds, functionalized carbons, and organic compounds are systematically summarized. Regarding the regulation of electrolyte-Li₂ S interface, the progress of applying polysulfides catholytes, redox mediators, and high-donicity/polarity electrolytes is overviewed in detail. Finally, the challenges and possible solutions aiming at optimizing Li₂ S deposition are given for further development of practical LSBs. This review would inspire more insightful works and, more importantly, may enlighten other electrochemical areas concerning heterogeneous deposition processes.

Unlocking Interfacial Electron Transfer of Ruthenium Phosphides by Homologous Core-Shell Design toward Efficient Hydrogen Evolution and Oxidation

Developing high-efficiency electrocatalysts for the hydrogen evolution and oxidation reactions (HER/HOR) in alkaline electrolytes is of critical importance for realizing renewable hydrogen technologies. Ruthenium phosphides (RuP_x ) are promising candidates to substitute Pt-based electrodes; however, great challenges still remain in their electronic structure regulation for optimizing intermediate adsorption. Herein, it is reported that a homologous RuP@RuP₂ core-shell architecture constructed by a phosphatization-controlled phase-transformation strategy enables strong electron coupling for optimal intermediate adsorption by virtue of the emergent interfacial functionality. Density functional theory calculations show that the RuP core and RuP₂ shell present efficient electron transfer, leading to a close to thermoneutral hydrogen adsorption Gibbs free energy of 0.04 eV. Impressively, the resulting material exhibits superior HER/HOR activities in alkaline media, which outperform the benchmark Pt/C and are among the best reported bifunctional hydrogen electrocatalysts. The present work not only provides an efficient and cost-effective bifunctional hydrogen electrocatalyst, but also offers a new synthetic protocol to rationally synthesize homologous core-shell nanostructures for widespread applications.