Nanostructured MoS2 with Interlayer Controllably Regulated by Ionic Liquids/Cellulose for High-Capacity and Durable Sodium Storage Properties

Carbon Framework Endows High-Stability Molybdenum Sulfide Nanosheet Anode for High-Voltage and Fast-Charging Alkali-Ion Batteries

Molybdenum disulfide (i.e., MoS2), while promising as an anode for alkali-ion batteries, faces critical challenges including structural degradation and sluggish ion diffusion kinetics in practical applications. Herein, MoS2 nanosheets anchored on a carbon framework (i.e., CF@MoS2) through C─S bonds were successfully synthesized, in which the three-dimensional carbon framework was synthesized using tellurium nanowires as the template. The C─S interfacial bonding ensures robust structural integration, while expanded interlayer spacing and bimodal pore channels synergistically enhance ion/electron transport. As a result, the as-prepared CF@MoS2 demonstrates unprecedented performance in both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). A high lithium storage capacity of 1072 mAh g-1 with superior stability over 500 cycles at 1.0 A g-1 can be achieved, while a high-rate capacity of 570 mAh g-1 at 5.0 A g-1 and excellent cycling stability over 500 cycles are also demonstrated in SIBs. The great features of CF@MoS2 are further confirmed versus LiNi1/3Co1/3Mn1/3O2 cathode in a high-voltage and fast-charging lithium-ion full battery, where the excellent stability and long lifespan are both confirmed. This work probes a great potential for developing metal sulfide-based electrodes in next-generation fast-charging energy storage systems.

Emerging Issues and Opportunities of 2D Layered Transition Metal Dichalcogenide Architectures for Supercapacitors

Two-dimensional layered transition metal dichalcogenides (2D TMDs) have emerged as promising candidates for supercapacitor (SCs) owing to their tunable electronic properties, layered structures, and effective ion intercalation capabilities. Despite these advantages, challenges such as low electrical conductivity, the interlayer restacking, oxidation and structural collapse hinder their practical implementation. This review provides a comprehensive overview of recent advances in the development of 2D TMDs for SCs. We begin by outlining the charge storage mechanisms and design principles for SCs, followed by an in-depth discussion of the synthesis methods and the associated challenges in fabricating 2D TMD architectures. The subsequent sections explore their crystal structures and reaction mechanisms, illustrating their electrochemical potential in SCs. Furthermore, we highlight material modification strategies, including nanostructuring, defect engineering, phase control, and surface/interface modulation, which have been proposed to overcome existing challenges. Finally, we address critical issues and emerging opportunities for 2D TMDs to inspire the development of SC technologies.

Engineering the Catalytic Superlattices for Highly Reversible Sodium-Ion Storage with A high Compositional Conversion Degree

A major obstacle of transition metal disulfides in sodium-ion batteries is compositional irreversible conversion, leading to fast capacity decay. Here, we propose to engineer a catalytic superlattice structure for achieving a record-high compositional reversible conversion degree (≈100 %). The superlattice is constructed by alternately stacking MoS2 layers and nitrogen/oxygen co-doped reduced graphene oxide-supported single-atom metal layers (MoS2/M-ONG SL, M=Fe, Co, Ni, Cu, Zn) with 100 % MoS2/M-ONG interfaces, in which the metal atoms bridge the two layers through S-M-O chemical bonds. Using MoS2/Co-ONG SL as a model, the unique superlattice structure shows excellent electron and Na+ transport properties during discharge and charge. Moreover, the Co-ONG boosts Na2S adsorption and decomposition by forming Co-3d and S-3p hybridization. As a result, the MoS2/Co-ONG SL shows a high compositional reversible conversion degree(≈100 %), as proven by a series of in-/ex situ spectroscopic analyses. As a result, the MoS2/Co-ONG SL exhibits a stable cycling stability of 300.7 mAh g-1 after 2000 cycles at 2 A g-1, with an ultrasmall capacity decay rate of 0.41 % per 100 cycles. This work offers a noteworthy perspective on the design and fabrication of conversion-type materials, emphasizing the crucial role of interface engineering in achieving excellent bidirectional reaction kinetics.

Realizing the Synergy of Interface and Dual-Defect Engineering for Molybdenum Disulfide Enables Efficient Sodium-Ion Storage

Engineering-rich electrocatalyst defects play a critical role in greatly promoting the charge storage/transfer capability of an energy storage/conversion system. Here, an ingenious and effective two-step strategy was used to synthesize a bimetallic sulfide/oxide composite with a coaxial carbon coating, starting from mixing well-dispersed MoO3 nanobelts and Co-PAA compound, followed by a selective etching process. The simultaneous formation of dual defects of interlayer defect and sulfur-rich vacancies as well as MoO2/MoS2-x/CoS heterojunctions noticeably enhances both electron transfer and ion diffusion kinetics. The ultrathin carbon protective layer on the surface of the composite ensures its high conductivity and excellent structural stability. The composite electrode shows a high reversible capacity (158.3 mAh g-1 at 10 A g-1 after 4000 cycles) and outstanding long-cycle stability (0.04% per cycle over 2100 cycles at 20 A g-1). A full cell based on MoO2/MoS2-x/CoS@N, S-C anode, and Na3V2(PO4)3 cathode can maintain a reversible capacity of 128.1 mAh g-1 after 600 cycles at 1 A g-1, surpassing that based on MoO2/MoS2 and is very comparable in performance with the state-of-the-art Na-ion full cells. Moreover, density functional theory (DFT) calculations, electrochemical kinetics analysis, and in situ Raman and ex-situ X-ray diffraction characterization were carried out to elucidate the involved scientific mechanisms of sodium storage.

Pre-intercalated Sodium Ions Enhance Sodium Storage of MoS2 Anode by Mitigating Structural Dissociation

Molybdenum disulfide (MoS2) is a promising anode for sodium-ion batteries (SIBs) due to its high theoretical capacity and layered structure. However, a poor reversible conversion reaction and a low initial Coulombic efficiency (ICE) limit its practical application. This study systematically investigated the potential of pre-intercalated sodium ions molybdenum disulfide (Na-MoS2) as an anode material for SIBs. Because of the mitigation of MoS2 structural dissociation and effective replenishment of active sodium ions, Na-MoS2 delivered an outstanding capacity of 507.7 mAh g-1 after 2000 cycles at 5 A g-1, along with an ICE of 95.30%. Pre-intercalating sodium ions can expand interlayer spacing and modulate electronic structure, allowing Na-MoS2 to have greater tolerance to the electrochemical intercalation/extraction process. Furthermore, the conversion reaction of Na-MoS2 has a higher Gibbs free energy, implying its structural dissociation is thermodynamically unfavorable. This work provides a new perspective on the study of transition metal dichalcogenide electrode materials for SIBs.

A Robust Network Sodium Carboxymethyl Cellulose-Epichlorohydrin Binder for Silicon Anodes in Lithium-Ion Batteries

Silicon (Si), as an ideal anode component for lithium-ion batteries, is susceptible to substantial volume changes, leading to pulverization and excessive electrolyte consumption, ultimately resulting in a rapid decline in the cycle stability. Herein, a new sodium carboxymethyl cellulose-epichlorohydrin (CMC-ECH) binder featuring a three-dimensional (3D) network cross-linked structure is synthesized by a simple ring-opening reaction, which can effectively bond the Si anode through abundant covalent and hydrogen bonds to mitigate its pulverization. Benefitting from the merits of the CMC-ECH binder, the electrochemical performance is significantly enhanced compared to the CMC binder. The CMC-ECH binder is applied to Si anodes, a specific capacity of 1054.2 mAh g-1 can be maintained at 0.2 C following 200 cycles under an elevated Si mass loading of around 1.0 mg cm-2, and the corresponding capacity retention is 65.6%. In the case of the LiFePO4//Si@CMC-ECH full battery, the cycle stability exhibits a substantial enhancement compared with the LiFePO4//Si@CMC full battery. Furthermore, the CMC-ECH binder demonstrates compatibility with micron-Si anode materials. Based on the above, we have successfully developed a facilely prepared water-based CMC-ECH binder that is suitable for Si and micron-Si anodes in lithium-ion batteries.

Stable Structure and Fast Ion Diffusion: A Flexible MoO2@Carbon Hollow Nanofiber Film as a Binder-Free Anode for Sodium-Ion Batteries with Superior Kinetics and Excellent Rate Capability

Designing innovative anode materials that exhibit excellent ion diffusion kinetics, enhanced structural stability, and superior electrical conductivity is imperative for advancing the rapid charge-discharge performance and widespread application of sodium-ion batteries. Hollow-structured materials have received significant attention in electrode design due to their rapid ion diffusion kinetics. Building upon this, we present a high-performance, free-standing MoO2@hollow carbon nanofiber (MoO2@HCNF) electrode, fabricated through facile coaxial electrospinning and subsequent heat treatment. In comparison to MoO2@carbon nanofibers (MoO2@CNFs), the MoO2@HCNF electrode demonstrates superior rate capability, attributed to its larger specific surface area, its higher pseudocapacitance contribution, and the enhanced diffusion kinetics of sodium ions. The discharge capacities of the MoO2@HCNF (MoO2@CNF) electrode at current densities of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 A g-1 are 195.55 (155.49), 180.98 (135.20), 163.81 (109.71), 144.05 (90.46), 121.16 (71.21) and 88.90 (44.68) mAh g-1, respectively. Additionally, the diffusion coefficients of sodium ions in the MoO2@HCNFs are 8.74 × 10-12 to 1.37 × 10-12 cm2 s-1, which surpass those of the MoO2@CNFs (6.49 × 10-12 to 9.30 × 10-13 cm2 s-1) during the discharging process. In addition, these prepared electrode materials exhibit outstanding flexibility, which is crucial to the power storage industry and smart wearable devices.

Recent Progress in Improving Rate Performance of Cellulose-Derived Carbon Materials for Sodium-Ion Batteries

Cellulose-derived carbon is regarded as one of the most promising candidates for high-performance anode materials in sodium-ion batteries; however, its poor rate performance at higher current density remains a challenge to achieve high power density sodium-ion batteries. The present review comprehensively elucidates the structural characteristics of cellulose-based materials and cellulose-derived carbon materials, explores the limitations in enhancing rate performance arising from ion diffusion and electronic transfer at the level of cellulose-derived carbon materials, and proposes corresponding strategies to improve rate performance targeted at various precursors of cellulose-based materials. This review also presents an update on recent progress in cellulose-based materials and cellulose-derived carbon materials, with particular focuses on their molecular, crystalline, and aggregation structures. Furthermore, the relationship between storage sodium and rate performance the carbon materials is elucidated through theoretical calculations and characterization analyses. Finally, future perspectives regarding challenges and opportunities in the research field of cellulose-derived carbon anodes are briefly highlighted.

3D flower-like hollow MXene@MoS2 heterostructure for fast sodium storage

Constructing an anode with fast electron transport and high cycling stability is important but challenging for large-scale applications of sodium-ion batteries (SIB). In this study, hierarchical flower-like MXene structures were synthesized using poly (methyl methacrylate) (PMMA) microsphere as templates. Subsequently, a straightforward hydrothermal reaction was utilized to anchor small-sized MoS2 nanosheets. The resulting MXene@MoS2 heterostructure exhibits a distinctive three-dimensional (3D) porous hollow architecture. This structure effectively addresses challenges related to self-aggregation of MoS2 nanosheets and volume expansion of the electrode material during Na+ insertion/extraction processes. Furthermore, the robust hetero-interface supports fast and stable electron transfer, thereby enhancing electrochemical reaction kinetics. The prepared MXene@MoS2 electrode demonstrates the specific capacity of 682.1 mA h g-1 at 0.2 A/g and the reversible capacity of 494.4 mA h g-1 after 1000 cycles at 5 A/g. It is noteworthy that the full battery assembled with the composite material as the anode can still maintain the capacity of 456.2 mA h g-1 after 80 cycles at 0.5 A/g. This outstanding reversible capacity and sustained stability over numerous cycles highlights its potential for a wide range of applications.