Employing Ni-Embedded Porous Graphitic Carbon Fibers for High-Efficiency Lithium-Sulfur Batteries

MgO nanoparticle-decorated in situ nitrogen-doped porous carbon hybrid materials as advanced sulfur hosts in Li-S batteries

Porous carbon combined with metal oxide modification shows great potential applications in lithium-sulfur batteries owing to various merits, including high encapsulation capacity for active sulfur, short transport path for lithium ions and good trapping capability of lithium polysulfides. Herein, inspired from waste biomass from passion fruit peels, an in situ nitrogen-doped porous carbon hybrid material decorated with MgO nanoparticles was designed and constructed via hydrothermal treatment and synchronous activation/carbonization method. The as-prepared porous carbon exhibited abundant pore structure with a notable large specific surface area of 2221.8 m2 g-1, mainly consisting of meso- and micro-pores. Even after modification with MgO nanoparticles, a high specific surface area of 1063.2 m2 g-1 was retained for sulfur loading and electrolyte penetration. In particular, the combination of rich pores, moderate MgO nanoparticles and nitrogen doping exhibited a good physicochemical synergistic effect for alleviating the shuttle dissolution of polysulfides. When the carbon hybrid material was evaluated as a sulfur host, the optimized battery delivered an initial discharge capacity of 792.5 mA h g-1 at 0.2 C and a high reversible capacity of 668 mA h g-1 after 200 cycles. Moreover, a stable long cycle performance of up to 1000 cycles was achieved at a high current rate of 1.0 C.

Interatomic Interactions and Ion-Transport in a Polyoligomeric Silsesquioxane-Based Multi-Ionic Salt Electrolyte for Lithium-Ion Batteries

Polyoligomeric silsesquioxane (POSS) tailored with trifluoromethanesulfonylimide-lithium and solvated in tetraglyme (G4) is a potential electrolyte for Li-ion batteries. Using classical MD simulations, at different G4/POSS(-LiNSO2CF3)8 molar ratios, the interactions of Li+ ions with the oxygen atoms of G4 and, oxygen/nitrogen sites of the pendant tails, the behaviour of POSS(--NSO2CF3)8, and the mobility of species are investigated. The RDFs showed that there exist competing interactions of the O(G4), O(POSS), and N(POSS) sites with Li+ ions. The lifetime analysis indicated that Li+- - -O(POSS) and Li+- - -N(POSS) interactions are longer-lived compared to Li+- - -O(G4). The morphological changes of the POSS tails upon interaction with Li+ ions were analysed using rotational lifetimes, coiling, and end-to-end distances. The ion-speciation analysis indicated the presence of solvent-separated ion pairs (SSIPs), contact ion pairs (CIPs), and higher-order ion clusters, with SSIPs being the more dominant species at 32/1. The self-diffusion coefficients for the 32/1 system, which showed the least cation-anion interaction, followed the trend:D G 4 > D L i + > D F P O S S > D P O S S ${{D}_{G4}\char62 {D}_{Li+}\char62 {D}_{F\left(POSS\right)}\char62 {D}_{POSS}}$ . The computed cationic transference number (t+) using theD F P O S S ${{D}_{F\left(POSS\right)}}$ is consistent with NMR experimental data. The t+ (and the trends with temperature) computed using theD P O S S ${{D}_{POSS}}$ and ionic conductivities are in good agreement.

A Three-Dimensional, Flexible Conductive Network Based on an MXene/Rubber Composite for Lithium Metal Anodes

Flexibility enhancement is a pressing issue in the current development of advanced lithium-metal battery applications. Many types of organic polymers are inherently flexible, which can form a composite structure enhancing electrode flexibility. However, organic polymers have a negative influence on the plating and stripping of lithium-metal anodes, and the large number of polymers block the pore of the material, reducing the utilization of the active site. Herein, we report a flexible porous substrate as an anode host based on a serine-modified three-dimensional structure of MXene and epoxidized natural rubber composite (3D/MXene-S-ENR), in which lithium ions can uniformly deposit in the interconnected pore structure. The 3D/MXene-S-ENR, having more nucleation sites, can effectively improve the uniformity of lithium metal, which effectively reduces the local current density and inhibits lithium dendrites. Compared with the serine-modified MXene and the epoxidized natural rubber electrode (MXene-S-ENR), the 3D/MXene-S-ENR electrode has lower overpotential and stable cycling. The lithium-sulfur batteries (Li-S) based on the 3D/MXene-S-ENR anode and sulfur cathode (3D/MXene-S-ENR@Li|S/C) deliver a stable discharge capacity of 316.2 mAh g-1 after 350 cycles, with a Coulombic efficiency of 98.05%. Finally, we assembled a flexible pack battery, which demonstrates the potential value of the 3D/MXene-S-ENR anode in high-performance flexible lithium-sulfur batteries.

Immobilization and Catalytic Conversion of Polysulfide by In-Situ Generated Nickel in Hollow Carbon Fibers for High-Rate Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are considered promising energy-storage systems because of their high theoretical energy density, low cost, and eco-friendliness. However, problems such as the shuttle effect can result in the loss of active materials, poor cyclability, and rapid capacity degradation. The utilization of a structural configuration that enhances electrochemical performance via dual adsorption-catalysis strategies can overcome the limitations of Li-S batteries. In this study, an integrated interlayer structure, in which hollow carbon fibers (HCFs) were modified with in-situ-generated Ni nanoparticles, was prepared by scalable one-step carbonization. Highly hierarchically porous HCFs act as the carbon skeleton and provide a continuous three-dimensional conductive network that enhances ion/electron diffusion. Ni nanoparticles with superior anchoring and catalytic abilities can prevent the shuttle effect and increase the conversion rate, thereby promoting the electrochemical performance. This synergistic effect resulted in a high capacity retention of 582 mAh g-1 at 1 C after 100 cycles, providing an excellent rate capability of up to 3 C. The novel structure, wherein Ni nanoparticles are embedded in cotton-tissue-derived HCFs, provides a new avenue for enhancing electrochemical performance at high C rates. This results in a low-cost, sustainable, and high-performance hybrid material for the development of practical Li-S batteries.

Cyclodextrin Metal-Organic Framework Functionalized Carbon Materials with Optimized Interface Electronics and Selective Supramolecular Channels for High-Performance Lithium-Sulfur Batteries

During the reaction process in lithium-sulfur batteries, Lewis acidic lithium polysulfides (LiPSs) affect ion distribution and overall electrolyte stability, degrading battery performance and product distribution (e.g., Li2S). Here, a microenvironment regulation strategy with optimized interface electronics and selective supramolecular channels, is proposed to enhance LiPS reaction kinetics through Lewis basic γ-cyclodextrin metal-organic framework (γ-CDMOF). To validate this concept, γ-CDMOF is rapidly synthesized on 3D graphene foam (GF) via a microwave-assisted method, resulting in a γ-CDMOF/GF cathode for high-performance Li-S batteries. A range of analytical techniques combined with density functional theory (DFT) calculations confirm that introducing a Lewis basic supramolecular microenvironment mitigates the LiPSs shuttle effect, enhances polysulfide capture, and improves sulfur redox conversion. Additionally, COMSOL simulations reveal that the γ-CDMOF framework and oxygen sites significantly reduce volumetric expansion stress during the LiPS solid-liquid phase transition. Impressively, the γ-CDMOF/GF cathode exhibits exceptional performance, including a high specific capacity (1253.01 mAh g⁻¹ at 0.1C), excellent rate performance (589.68 mAh g⁻¹ at 5C), and long cycle life (over 1200 cycles). This study introduces a new concept of supramolecular microenvironment regulation and interfacial interaction strategy, offering a unique approach for the development of multifunctional electrode materials.

Ru Single Atom Dispersed on MoS2/MXene for Enhanced Sulfur Reduction Reaction in Lithium-Sulfur Batteries

The high theoretical energy density (2600 Wh kg-1) and low cost of lithium-sulfur batteries (LSBs) make them an ideal alternative for the next-generation energy storage system. Nevertheless, severe capacity degradation and low sulfur utilization resulting from shuttle effect hinder their commercialization. Herein, Single-atom Ru-doped 1T/2H MoS2 with enriched defects decorates V2C MXene (Ru-MoS2/MXene) produced by a new phase-engineering strategy employed as sulfur host to promote polysulfide adsorption and conversion reaction kinetics. The Ru single atom-doped adjusts the chemical environment of the MoS2/MXene to anchor polysulfide and acts as an efficient center to motivate the redox reaction. In addition, the rich defects of the MoS2 and ternary boundary among 1T/2H MoS2 and V2C accelerate the charge transfer and ion movements for the reaction. As expected, the Ru-MoS2/MXene/S cathode-based cell exhibits a high-rate capability of 684.3 mAh g-1 at 6 C. After 1000 cycles, the Ru-MoS2/MXene/S cell maintains an excellent cycling stability of 696 mAh g-1 at 2 C with a capacity degradation as low as 0.02% per cycle. Despite a high sulfur loading of 9.5 mg cm-2 and a lean electrolyte-to-sulfur ratio of 4.3, the cell achieves a high discharge capacity of 726 mAh g-1.

Advancing Metallic Lithium Anodes: A Review of Interface Design, Electrolyte Innovation, and Performance Enhancement Strategies

Lithium (Li) metal is one of the most promising anode materials for next-generation, high-energy, Li-based batteries due to its exceptionally high specific capacity and low reduction potential. Nonetheless, intrinsic challenges such as detrimental interfacial reactions, significant volume expansion, and dendritic growth present considerable obstacles to its practical application. This review comprehensively summarizes various recent strategies for the modification and protection of metallic lithium anodes, offering insight into the latest advancements in electrode enhancement, electrolyte innovation, and interfacial design, as well as theoretical simulations related to the above. One notable trend is the optimization of electrolytes to suppress dendrite formation and enhance the stability of the electrode-electrolyte interface. This has been achieved through the development of new electrolytes with higher ionic conductivity and better compatibility with Li metal. Furthermore, significant progress has been made in the design and synthesis of novel Li metal composite anodes. These composite anodes, incorporating various additives such as polymers, ceramic particles, and carbon nanotubes, exhibit improved cycling stability and safety compared to pure Li metal. Research has used simulation computing, machine learning, and other methods to achieve electrochemical mechanics modeling and multi-field simulation in order to analyze and predict non-uniform lithium deposition processes and control factors. In-depth investigations into the electrochemical reactions, interfacial chemistry, and physical properties of these electrodes have provided valuable insights into their design and optimization. It systematically encapsulates the state-of-the-art developments in anode protection and delineates prospective trajectories for the technology's industrial evolution. This review aims to provide a detailed overview of the latest strategies for enhancing metallic lithium anodes in lithium-ion batteries, addressing the primary challenges and suggesting future directions for industrial advancement.

Hybrid-Electrolytes System Established by Dual Super-lyophobic Membrane Enabling High-Voltage Aqueous Lithium Metal Batteries

Aqueous electrolytes and related aqueous rechargeable batteries own unique advantage on safety and environmental friendliness, but coupling high energy density Li-metal batteries with aqueous electrolyte still represent challenging and not yet reported. Here, this work makes a breakthrough in "high-voltage aqueous Li-metal batteries" (HVALMBs) by adopting a brilliant hybrid-electrolytes strategy. Concentrated ternary-salts ether-based electrolyte (CTE) acts as the anolyte to ensure the stability and reversibility of Li-metal plating/stripping. Eco-friendly water-in-salt (WiS) electrolyte acts as catholyte to support the healthy operation of high-voltage cathodes. Most importantly, the aqueous catholyte and non-aqueous anolyte are isolated in each independent chamber without any crosstalk. Aqueous catholyte permeation toward Li anode can be completely prohibited without proton-induced corrosion, which is enabled by the introduction of under-liquid dual super-lyophobic membrane-based separator, which can realize the segregation of the most effective immiscible electrolytes with a surface tension difference as small as 6 mJ m-2. As a result, the aqueous electrolyte can be successfully coupled with Li-metal anode and achieve the fabrication of HVALMBs (hybrid-electrolytes system), which presents long-term cycle stability with a capacity retention of 81.0% after 300 cycles (LiNi0.8Mn0.1Co0.1O2 || Li (limited) cell) and high energy density (682 Wh kg-1).

Interfacial integration of ultra-thin flexible electrochemical capacitors via vacuum filtration based on gelatinized fibrous membranes

We developed a hydroxyl-rich fibrous membrane that can undergo controllable in situ gelation to create a porous integrated interface between hydrogel electrolytes and electrode, resulting in ultra-thin all-in-one electrochemical capacitors.

Research progress in the preparation of mesophase pitch from fluid catalytic cracking slurry

For the preparation of high-performance pitch-based carbon fibers and other carbon materials, mesophase pitch serves as a high-quality precursor. Since FCC (Fluid Catalytic Cracking) oil slurry is abundant in aromatic hydrocarbons and saturated hydrocarbons (about 95% in total), it has become an ideal choice for developing new carbon material products. This paper details the research progress of preparing mesophase asphalt with FCC oil slurry as a raw material from perspectives including the preparation method of synthesizing mesophase asphalt from FCC oil slurry, the impact factors of the formation process of mesophase asphalt and the industrial application of mesophase asphalt.

In Situ Trapping Strategy Enables a High-Loading Ni Single-Atom Catalyst as a Separator Modifier for a High-Performance Li-S Battery

The poor electrochemical reaction kinetics of Li polysulfides is a key barrier that prevents the Li-S batteries from widespread applications. Ni single atoms dispersed on carbon matrixes derived from ZIF-8 are a promising type of catalyst for accelerating the conversion of active sulfur species. However, Ni favors a square-planar coordination that can only be doped on the external surface of ZIF-8, leading to a low loading amount of Ni single atoms after pyrolysis. Herein, we demonstrate an in situ trapping strategy to synthesize Ni and melamine-codoped ZIF-8 precursor (Ni-ZIF-8-MA) by simultaneously introducing melamine and Ni during the synthesis of ZIF-8, which can remarkably decrease the particle size of ZIF-8 and further anchor Ni via Ni-N₆ coordination. Consequently, a novel high-loading Ni single-atom (3.3 wt %) catalyst implanted in an N-doped nanocarbon matrix (Ni@NNC) is obtained after high-temperature pyrolysis. This catalyst as a separator modifier shows a superior catalytic effect on the electrochemical transitions of Li polysulfides, which endows the corresponding Li-S batteries with a high specific capacity of 1232.4 mA h g^-1 at 0.3 C and an excellent rate capability of 814.9 mA h g^-1 at 3 C. Furthermore, a superior areal capacity of 4.6 mA h cm^-2 with stable cycling over 160 cycles can be achieved under a critical condition with a low electrolyte/sulfur ratio (8.4 μL mg^-1) and high sulfur loading (4.85 mg cm^-2). The outstanding electrochemical performances can be attributed to the strong adsorption and fast conversion of Li polysulfides on the highly dense active sites of Ni@NNC. This intriguing work provides new inspirations for designing high-loading single-atom catalysts applied in Li-S batteries.

Interlayer Modulation of Layered Transition Metal Compounds for Energy Storage

Layered transition metal compounds are one of the most important electrode materials for high-performance electrochemical energy storage devices, such as batteries and supercapacitors. Charge storage in these materials can be achieved via intercalation of ions into the interlayer channels between the layer slabs. With the development of lithium-beyond batteries, larger carrier ions require optimized interlayer space for the unrestricted diffusion in the two-dimensional channels and effectively shielded electrostatic interaction between the slabs and interlayer ions. Therefore, interlayer modulation has become an efficient and promising approach to overcome the problems of sluggish kinetics, structural distortion, irreversible phase transition, dissolution of some transition metal elements, and air instability faced by these materials and thus enhance the overall electrochemical performance. In this review, we focus on the interlayer modulation of layered transition metal compounds for various batteries and supercapacitors. Merits of interlayer modulation on the charge storage procedures of charge transfer, ion diffusion, and structural transformation are first discussed, with emphasis on the state-of-art strategies of intercalation and doping with foreign species. Following the obtained insights, applications of modified layered electrode materials in various batteries and supercapacitors are summarized, which may guide the future development of high-performance and low-cost electrode materials for energy storage.

FeCoNi Ternary Nano-Alloys Embedded in a Nitrogen-Doped Porous Carbon Matrix with Enhanced Electrocatalysis for Stable Lithium-Sulfur Batteries

The application of composite materials that combine the advantages of carbonaceous material and metal alloy proves to be a valid method for improving the performance of lithium-sulfur batteries (LSBs). Herein iron-cobalt-nickel (FeCoNi) ternary alloy nanoparticles (FNC) that spread on nitrogen-doped carbon (NC) are obtained by a strategy of low-temperature sol-gel followed by annealing at 800 °C under an argon/hydrogen atmosphere. Benefiting from the synergistic effect of different components of FNC and the conductive network provided by the NC, not only can the "shuttle effect" of lithium polysulfides (LiPS) be suppressed, but also the conversion of LiPS, the diffusion of Li⁺, and the deposition of Li₂S can be accelerated. Taking advantage of those merits, the batteries assembled with an FNC@NC-modified polypropylene (PP) separator (FNC@NC//PP) can deliver a high reversible specific capacity of 1325 mAh g^-1 at 0.2 C and maintain 950 mAh g^-1 after 200 cycles, and they can also achieve a low capacity fading rate of 0.06% per cycle over 500 cycles at 1 C. More impressively, even under harsh test conditions (the ratio of electrolyte to sulfur (E/S) = 6 μL mg^-1 and sulfur loading = 4.7 mg cm^-2 and E/S = 10 μL mg^-1 and sulfur loading = 5.9 mg cm^-2), the area capacity of batteries is still much higher than 4 mAh cm^-2.

In Situ Construction of Composite Artificial Solid Electrolyte Interphase for High-Performance Lithium Metal Batteries

Lithium metal is considered as the most promising anode material for high energy density secondary batteries due to its high theoretical specific capacity and low redox potential. However, poor interfacial stability and uncontrollable dendrite growth seriously hinder the commercial application of Li metal anodes. Herein, we constructed a composite artificial solid-electrolyte interphase (ASEI) utilizing the in situ reaction between polyacrylic acid (PAA)/stannous fluoride (SnF₂) and lithium metal, which spontaneously generates LiPAA, LiF, and Li₅Sn₂ alloys. The in situ formed LiPAA as a flexible matrix can accommodate the volume change of the lithium anode. Meanwhile, LiF and Li₅Sn₂ play the roles for improving the mechanical properties and boosting Li-ion flux in the interfacial layer, respectively. Benefiting from the ingenious design, the PAA-SnF₂@Li anodes remain stable and dendrite-free morphology in symmetric cells for over 2000 h and exhibit excellent cycling stability in high-area loading (10.52 mg cm^-2) Li||LiFePO₄ full cells with a N/P of 1.68, which endures only 0.11% average capacity decay per cycle in 200 cycles. This simple and low-cost method supplies a route for the commercial application of lithium metal anodes with fresh eyes.

Stabilization of Lithium Metal Interfaces by Constructing Composite Artificial Solid Electrolyte Interface with Mesoporous TiO2 and Perfluoropolymers

The next generation of high-energy-density storage devices is expected to be rechargeable lithium metal batteries. However, unstable metal-electrolyte interfaces, dendrite growth, and volume expansion will compromise lithium metal batteries (LMB) safety and life. A simple drop-casting method is used to create a double-layer functional interface composed of inorganic mesoporous TiO₂ and F-rich organics PFDMA. For high-quality lithium deposition, TiO₂ can provide uniform mechanical pressure, abundant mesoporous channels, and increased ionic conductivity, while PFDMA provides enough F to form LiF in the first cycle and improves Li-electrolyte compatibility. Experiments and simulations are combined to investigate the optimized mechanism of the LiF-rich solid electrolyte interface (SEI). The high binding energy of organic matter and Li demonstrates that Li⁺ preferentially binds with the F atom in organic matter. As a result, the tightly bound double-layer structure can inhibit lithium dendrite growth and slow electrolyte decomposition. Consequently, the symmetric Li||Li cell has a high stability performance of over 800 h. The assembled LiFePO₄ ||Li cell can sustain 300 cycles at a 1 C rate and has a reversible capacity of 136.7 mAh g^-1 .

Hierarchical hollow superstructure cobalt selenide bird nests for high-performance lithium storage

The inferior cycling performance caused by large volume variation is the main problem that restricts the application of cobalt selenides in lithium-ion batteries. Herein, we synthesize raspberry-like Co-ethylene glycol precursor. It is further selenized into the hierarchical hollow superstructure CoSe₂/CoSe bird nests that are assembled by the hollow nanosphere units of CoSe₂ and CoSe nanocrystalline. CoSe₂/CoSe bird nests achieve excellent cycling performance, high reversible capacity and satisfactory rate capability (1361 mAh/g at 1 A/g after 1000 cycles, 579 mAh/g at 2 A/g after 2000 cycles, 315 mAh/g at 5 A/g after 1000 cycles). Electrochemical kinetics analyses and ex-situ material characterization reveal that the surface capacitive behavior controls the electrochemical reaction, and the composite has low reaction impedance, fast and stable Li⁺ diffusion, and superior structural stability. The superior lithium storage performance is attributed to the unique superstructure bird nest. Large specific surface area, abundant hierarchical pores and the opening mouth result in high electrochemical activity, which induces high reversible capacity. The small hollow nanosphere units, the sufficiently thick hierarchical porous superstructure shell and the large hollow interior bring about the strong synergistic effect to improve cycling performance. The intimately coupling of CoSe₂/CoSe nanocrystalline and the hollow nanosphere units guarantees high conductivity. This work has greatly enriched the understanding of structure design of high-performance cobalt selenide anodes.

Recent Advances in Carbon Anodes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have gained tremendous attention for large-scale energy storage applications due to the natural abundance, low cost, and even geographic distribution of sodium resources as well as a similar working mechanism to lithium-ion batteries (LIBs). One of the critical bottlenecks, however, is the design of high-performance and low-cost anode materials. Graphite anode that has dominated the market share of LIBs does not properly intercalate sodium ions. However, other carbonaceous materials are still considered as one of the most promising anode materials for SIBs in virtue of their high electronic conductivity, abundant active sites, hierarchical porosity, and excellent mechanical stability. In this review, we have tried to summarize the latest progresses made on the development of carbon-based negative electrodes (including hard carbons, soft carbons, and synthetic carbon allotropes) for SIBs. We also have provided a comprehensive understanding of their physical properties, the sodium ions storage mechanisms, and the improvement measures to cope with the current challenges. In addition, we have proposed future research directions for SIBs that will provide important insights into further development of carbon-based materials for SIBs.

Surpassing the Redox Potential Limit of Organic Cathode Materials via Extended p-π Conjugation of Dioxin

The key to enabling high energy density of organic energy-storage systems is the development of high-voltage organic cathodes; however, the redox voltage (<4.0 V vs Li/Li⁺) of state-of-the-art organic electrode materials (OEMs) remains unsatisfactory. Herein, we propose a novel dibromotetraoxapentacene (DBTOP) redox center to surpass the redox potential limit of OEMs, achieving ultrahigh discharge plateaus of approximately 4.4 V (vs Li⁺/Li). As theoretically analyzed, electron delocalization between dioxin active centers and benzene rings as well as electron-withdrawing bromine atoms endows the molecule with a low occupied molecular orbital level by diluting the electron density of dioxin in the whole p-π conjugated skeleton, and the strong π-π interactions among the DBTOP molecules provide a faster electrochemical kinetic pathway. This tetraoxapentacene redox center makes the working voltage of OEMS closer to the high-voltage inorganic electrodes, and its chemical and structural tunability may stimulate the further development of high-voltage organic cathodes.