Hydrothermal “Disproportionation” of Biomass into Oriented Carbon Microsphere Anode and 3D Porous Carbon Cathode for Potassium Ion Hybrid Capacitor

The comprehensive utilization of biomass to obtain energy-storage carbonaceous materials with special microstructures is of great significance. Herein, a universal method is proposed to fabricate oriented carbon microspheres (OCMSs) and 3D porous carbon (3DPC) block at the same time via high-temperature hydrothermal “disproportionation” of biomass including but not limited to basswood, pinus sylvestris, red walnut, beech, bamboo, and sorghum straw. Through nuclear magnetic resonance, gas chromatography mass spectrometry, as well as various morphologic and structural characterizations, it is demonstrated that OCMS with (002) orientation originates from the carbonization of organic matters produced by the successive decomposition of hemicellulose, cellulose, and lignin during the high-temperature hydrothermal process, while the 3DPC blocks exhibit abundant sp³ defects and micropores with a surface area of 855.12 m² g⁻¹ due to the constant loss of organic components from basswood blocks. As a result, the OCMS anode exhibits a high capacity of 201.1 mA h g⁻¹ at 2000 mA g⁻¹ after 2000 cycles, 3DPC cathode delivers a capacity of 95.7 mA h g⁻¹ at 1.0 A g⁻¹ after 5000 cycles. Remarkably, the as-assembled OCMS//3DPC potassium ion hybrid capacitor exhibits an energy of 140.7 Wh kg⁻¹ at 643.8 W kg⁻¹, with a long cycle life over 8500 cycles.     

Unraveling the Origin of Enhanced K+ Storage of Carbonaceous Anodes Enabled by Nitrogen/Sulfur Co-Doping

N-doped carbons, as promising anode materials for energy storage, are generally modified by the additional heteroatoms (B, P, and S) doping to further promote the electrochemical performance. However, the promotion mechanism by such additional doping, especially its interplay with N-containing species, remains unclear. Herein, by adopting N/S co-doped carbon as a model system, it is found that S-doping can significantly improve the content of pyridinic-N, i.e., the most energetically favorable N type for K⁺ storage. Theoretical calculations reveal that such S-induced pyridinic-N improvement possibly originates from its catalytic effect that can facilitate the transition from edge quaternary-N to pyridinic-N. The resultant high content of pyridinic-N, together with the additional S species, ensures abundant active sites for K⁺ storage. Accordingly, the N/S co-doped carbon anode delivers both a high reversible capacity (422.9 mA h g⁻¹ at 0.05 A g⁻¹) and an impressive cyclic stability (249.6 mA h g⁻¹ at 1 A g⁻¹ over 4000 cycles). Moreover, in/ex situ characterizations further verify the merits of N/S co-doped carbon from the perspective of compositional evolution and structural stability. This study unravels the origin of enhanced K⁺ storage by N/S co-doping, which also helps to understand the synergistic effects of other heteroatoms co-doping systems.     

Boosting Potassium Storage Kinetics,Stability, and Volumetric Performance of Honeycomb-Like Porous Red Phosphorus via In Situ Embedding Self-Growing Conductive Nano-Metal Networks

Large volume expansion and sluggish reaction kinetics of low-conductivity red phosphorus (RP) anodes hinder its practical application in potassium-ion batteries (PIBs). Here, a self-limited growth strategy to fabricate Bi (Sb) nanoparticles is demonstrated, as electrochemically active and conductive coating, in situ embedded into honeycomb-like porous red phosphorus (HPRP) to form HPRP@Bi (HPRP@Sb) composites, greatly improving the potassium-storage kinetics, stability and volumetric performance of HPRP. Here, Bi nanoparticles are converted into amorphous Bi during cycling, which are uniformly coated on the porous HPRP skeleton to form 3D conductive Bi networks. Theoretical calculations verify that introducing amorphous Bi significantly decreases K⁺ diffusion barrier in composites, and greatly enhancing their electrical conductivity and interfacial ion transport between HPRP and Bi, thereby accelerating their potassium storage kinetics and stability. Whereas the robust porous structure and inward expansion mechanism of HPRP effectively buffer their volume expansion of RP and Bi. Therefore, HPRP@Bi anode delivers high gravimetric and volumetric capacity (465.6 mAh g⁻¹, 745 mAh cm⁻³) and stable long lifespan with 200 cycles at 0.05 A g⁻¹ in PIBs. This work demonstrates a new approach to promote ion storage kinetics and stability of RP via integrating the synergy of high-conductivity active metal and high-capacity porous RP.     

Mg-Doped Na4Fe3(PO4)2(P2O7)/C Composite with Enhanced Intercalation Pseudocapacitance for Ultra-Stable and High-Rate Sodium-Ion Storage

Na₄Fe₃(PO₄)₂(P₂O₇) (NFPP) is considered as a promising cathode material for sodium-ion batteries (SIBs) due to its low cost, non-toxicity, and high structural stability, but its electrochemical performance is limited by the poor electronic conductivity. In this study, Mg-doped NFPP/C composites are presented as cathode materials for SIBs. Benefiting from the enhanced electrochemical kinetics and intercalation pseudocapacitance resulted from the Mg doping, the optimal Mg-doped NFPP/C composite (NFPP-Mg5%) delivers high rate performance (capacity of ≈40 mAh g⁻¹ at 20 A g⁻¹) and ultra-long cycling life (14 000 cycles at 5 A g⁻¹ with capacity retention of 80.8%). Moreover, the in situ X-ray diffraction and other characterizations reveal that the sodium storage process of NFPP-Mg5% is dominated by the intercalation pseudocapacitive mechanism. In addition, the full SIB based on NFPP-Mg5% cathode and hard carbon anode exhibits the discharge capacity of ≈50 mAh g⁻¹ after 200 cycles at 500 mA g⁻¹. This study demonstrates the feasibility of improving the electrochemical performance of NFPP by doping strategy and presents a low-cost, ultra-stable, and high-rate cathode material for SIBs.     

Fe2VO4 Nanoparticles Anchored on Ordered Mesoporous Carbon with Pseudocapacitive Behaviors for Efficient Sodium Storage

Iron vanadates are attractive anode materials for sodium-ion batteries (SIBs) because of their abundant resource reserves and high capacities. However, their practical application is restricted by the aggregation of materials, sluggish reaction kinetics, and inferior reversibility. Herein, Fe₂VO₄ nanoparticles are anchored on the ordered mesoporous carbon (CMK-3) nanorods to assemble 3D Fe₂VO₄@CMK-3 composites, by solvothermal treatment and subsequent calcination. The resulting composites provide abundant active sites, high electrical conductivity, and excellent structural integrity. The pseudocapacitive-controlled behavior is the dominating sodium storage mechanism, which facilitates a fast charge/discharge process. The Fe₂VO₄@CMK-3 composites exhibit stable sodium-ion storage (219 mAh g⁻¹ under 100 mA g⁻¹ after 300 cycles), good rate performance (144 mAh g⁻¹ at 3.2 A g⁻¹), and excellent cycling performance (132 mAh g⁻¹ at 1 A g⁻¹ with capacity retention of 96.4% after 800 cycles). When coupled with a NaNi_1/3Fe_1/3Mn_1/3O₂ cathode, the sodium-ion full cell displays excellent cycling stability (94 mAh g⁻¹ after 500 cycles at 500 mA g⁻¹). These findings point to the potential of Fe₂VO₄@CMK-3 for application as anodes in SIBs.     

Effective Coupling of Amorphous Selenium Phosphide with High-Conductivity Graphene as Resilient High-Capacity Anode for Sodium-Ion Batteries

It is of great importance to develop high-capacity electrodes for sodium-ion batteries (SIBs) using low-cost and abundant materials, so as to deliver a sustainable technology as alternative to the established lithium-ion batteries (LIBs). Here, a facile ball milling process to fabricate high-capacity SIB anode is devised, with large amount of amorphous SeP being loaded in a well-connected framework of high-conductivity crystalline graphene (HCG). The HCG substrate enables fast transportation of Na ions and electrons, while accommodating huge volumetric changes of the active anode matter of SeP. The strong glass forming ability of NaxSeP helps prevent crystallization of all stable compounds but ultrafine nanocrystals of Na2Se and Na3P. Thus, the optimized anode delivers excellent rate performance with high specific capacities being achieved (855 mAh g⁻¹ at 0.2 A g⁻¹ and 345 mAh g⁻¹ at 5 A g⁻¹). More importantly, remarkable cycling stability is realized to maintain a steady capacity of 732 mAh g⁻¹ over 500 cycles, when the SeP in the SeP@HCG still remains 86% of its theoretical capacity. A high areal capacity of 2.77 mAh is achieved at a very high loading of 4.1 mg cm⁻² anode composite.     

Systematic Modification of MoO3-Based Cathode by the Intercalation Engineering for High-Performance Aqueous Zinc-Ion Batteries

Aqueous Zn-ion batteries are attracting extensive attention, but their large-scale application is prevented by the poor electrochemical kinetics and terrible lifespan. Herein, a strategy of introducing the conductive poly(3,4-ethylenedioxythiophene) (PEDOT) into the interlayers of α-MoO₃ is reported to systematically overcome the above shortcomings. Through data analyses of the cyclic coltammetry, electrochemical impedance spectroscopy, and galvanostatic intermittent titration technique, the electrochemical kinetics of the PEDOT-intercalated MoO₃ (PEDOT-MoO₃) is proved to be significantly improved. The first-principles calculations microscopically disclose that the changed energy band and the lowered binding energy between Zn²⁺ and host O²⁻ boost electrochemical kinetics of PEDOT-MoO₃. Meanwhile, its decreased hydrophilicity and the suppressed dissolution of molybdenum stabilizes the repeated cycling processes. Interestingly, it is found that excellent electrochemical kinetics of cathode electrode can restrain the growth of zinc dendrite on the Zn anode, prolonging the lifespan of aqueous Zn-ion batteries. As a result, the PEDOT-MoO₃ exhibits the enhanced specific capacity (341.5 vs 146.7 mAh g⁻¹ at 0.1 A g⁻¹), high rate capacity (178.2 vs 19.4 mAh g⁻¹ at 30 A g⁻¹) and prolonged cycling stability (77.6% capacity retention over 500 cycles vs 2.3% capacity retention over 100 cycles at 30 A g⁻¹) compared with pristine MoO₃. Moreover, the PEDOT-MoO₃ as cathode of quasi-solid-state ZIBs also delivers an impressive electrochemical performance.     

Si/SiO2@Graphene Superstructures for High-Performance Lithium-Ion Batteries

The superstructure composed of various functional building units is promising nanostructure for lithium-ion batteries (LIBs) anodes with extreme volume change and structure instability, such as silicon-based materials. Here, a top-down route to fabricate Si/SiO₂@graphene superstructure is demonstrated through reducing silicalite-1 with magnesium reduction and depositing carbon layers. The successful formation of superstructure lies on the strong 3D network formed by the bridged-SiO₂ matrix coated around silicon nanoparticles. Furthermore, the mesoporous Si/SiO₂ with amorphous bridged SiO₂ facilitates the deposition of graphene layers, resulting in excellent structural stability and high ion/electron transport rate. The optimized Si/SiO₂@graphene superstructure anode delivers an outstanding cycling life for ≈1180 mAh g⁻¹ at 2 A g⁻¹ over 500 cycles, excellent rate capability for ≈908 mAh g⁻¹ at 12 A g⁻¹, great areal capacity for ≈7 mAh cm⁻² at 0.5 mA cm⁻², and extraordinary mechanical stability. A full cell test using LiFePO₄ as the cathode manifests a high capacity of 134 mAh g⁻¹ after 290 loops. More notably, a series of technologies disclose that the Si/SiO₂@graphene superstructure electrode can effectively maintain the film between electrode and electrolyte in LIBs. This design of Si/SiO₂@graphene superstructure elucidates a promising potential for commercial application in high-performance LIBs.     

On the Practical Applicability of Rambutan-like SiOC Anode with Enhanced Reaction Kinetics for Lithium-Ion Storage

Silicon oxycarbide (SiOC) possesses great potential in lithium-ion batteries owing to its tunable chemical component, high reversible capacity, and small volume expansion. However, its commercial application is restricted due to its poor electrical conductivity. Herein, rambutan-like vertical graphene coated hollow porous SiOC (Hp-SiOC@VG) spherical particles with an average diameter of 302 nm are fabricated via a hydrothermal treatment combined CH₄ pyrolysis strategy for the first time. As-prepared Hp-SiOC@VG exhibits a large reversible capacity of 729 mAh g⁻¹ at 0.1 A g⁻¹, remarkable cycling stability of 98% capacity retention rate after 600 cycles at 1.0 A g⁻¹ and high rate capability of 289 mAh g⁻¹ at 5.0 A g⁻¹ owing to the unique structure of the particles and the electrical conductivity of the vertical graphene. Density functional theory calculations reveal that the higher contents of SiO₃C and SiO₂C₂ structural units in the SiOC are beneficial to enhance the Li⁺ storage capacity. Additionally, the full-cell assembled with Hp-SiOC@VG and LiFePO₄ delivers up to 74% capacity retention rate after 100 cycles at 0.2 A g⁻¹. This work reports a new way for the facile preparation of template-free hollow porous materials and expands the application prospects of SiOC-based anode for lithium-ion batteries.     

Functional Passivation Interface of LiNi0.8Co0.1Mn0.1O2 toward Superior Lithium Storage

The fast capacity/voltage fading with a low rate capability has challenged the commercialization of layer-structured Ni-rich cathodes in lithium-ion batteries. In this study, an ultrathin and stable interface of LiNi_0.8Mn_0.1Co_0.1O₂ (NCM) is designed via a passivation strategy, dramatically enhancing the capacity retention and operating voltage stability of cathode at a high cut-off voltage of 4.5 V. The rebuilt interface as a stable path for Li⁺ transport, would strengthen the cathode–electrolyte interface stability, and restrain the detrimental factors for cathode–electrolyte interfacial reactions, intergranular cracking and irreversible phase transformation from layered to spinel, even salt-rock phase. The as-optimized NCM displays a higher cyclability (i.e., 206.6 mA h g⁻¹ at 0.25 C (50 mA g⁻¹) with 92.0% capacity retention over 100 cycles) and a better rate capability (141.0 and 112.6 mA h g⁻¹ at 12.5 and 25 C, respectively) than pristine NCM (205.0 mA h g⁻¹ with 73.0% capacity retention at 0.25 C; 120.9 and 93.1 mA h g⁻¹ at 12.5 and 25 C, respectively).     

Rotatable Methylene Ether Bridge Units Enabling High Chain Flexibility and Rapid Ionic Transport in a New Universal Aqueous Conductive Binder

Binders play an essential role in maintaining the mechanical integrity and stability of electrodes. Herein, a novel aqueous and conductive binder (OXP/CNT-1.5) consisting of carbon nanotubes (CNTs) interwoven with a flexible nano-film of oxidized pullulan (OXP) is designed. The rotatable methylene ether bridge units within OXP chain endow the binder with high chain flexibility, facilitate rapid ion transport, and buffer severe volumetric expansion during charge-discharge cycling. Furthermore, its tight intertwining with CNTs forms continuously conductive and flexible skeletons, which can firmly grasp active nanoparticles through a “face-to-point” bonding type, guaranteeing the electrodes high conductivity and outstanding mechanical integrity. More importantly, these conductive binders are applicable to the Si/C anode as well as the LiFePO₄ cathode. The as-fabricated Si/C anode delivers a 88.2% capacity retention after 100 cycles and 80.2% capacity retention at 0.5 A g⁻¹ (vs 0.05 A g⁻¹), far surpassing the electrode fabricated by conventional polyvinylidene fluoride binder and carbon black mixtures. The LiFePO₄/Si/C full cells based on OXP/CNT-1.5 demonstrate excellent electrochemical behavior and stability (97.4% capacity retention after 100 cycles). This work highlights the key role of rotatable methylene ether bridge units to enhance the flexibility, ion conductivity, and stability, which is inspiring in the context of designing novel binders for high-performance batteries.     

Van der Waals Forces between S and P Ions at the CoP-C@MoS2/C Heterointerface with Enhanced Lithium/Sodium Storage

Metal–organic framework-derived metal phosphides with high capacity, facile synthesis, and morphology-controlled are considered as potential anodes for lithium/sodium-ion batteries. However, the severe volume expansion during cycling can cause the electrode material to collapse and reduce the cycle life. Here, novel CoP-C@MoS₂/C nanocube composites are synthesized by vapor-phase phosphating and hydrothermal process. As the anode of LIBs, CoP-C@MoS₂/C exhibits outstanding long-cycle performance of 369 mAh g⁻¹ at 10 A g⁻¹ after 2000 cycles. In SIBs, the composite also displays excellent rate capability of 234 mAh g⁻¹ at 5 A g⁻¹ and an ultra-high the capacity retention rate of 90.16% at 1 A g⁻¹ after 1000 cycles. Through density functional theory, it is found that the S ions and P ions at the interface formed by CoP and MoS₂ can serve as Na⁺/Li⁺ diffusion channels with an action of van der Waals force, have attractive characteristics such as high ion adsorption energy, low expansion rate and fast diffusion kinetics compared with MoS₂. This study provides enlightenment for the reasonable design and development of lithium/sodium storage anode materials composited with MOF-derived metal phosphides and metal sulfides.     

Tailoring Ultrahigh Energy Density and Stable Dendrite-Free Flexible Anode with Ti3C2Tx MXene Nanosheets and Hydrated Ammonium Vanadate Nanobelts for Aqueous Rocking-Chair Zinc Ion Batteries

Exploiting Zn metal-free anode materials would be an effective strategy to resolve the problems of Zn metal dendrites that severely hinder the development of Zn ion batteries (ZIBs). However, the study of Zn metal-free anode materials is still in their infancy, and more importantly, the low energy density severely limits their practical implementations. Herein, a novel (NH₄)₂V₁₀O₂₅ · 8H₂O@Ti₃C₂T_x (NHVO@Ti₃C₂T_x) film anode is proposed and investigated for constructing “rocking-chair” ZIBs. The NHVO@Ti₃C₂T_x electrode shows a capacity of 514.7 mAh g⁻¹ and presents low potential which is 0.59 V (vs Zn²⁺/Zn) at 0.1 A g⁻¹. The introduction of Ti₃C₂T_x not only affords an interconnected conductive network, but also stabilizes the NHVO nanobelts structure for a long cycle life (84.2% retention at 5.0 A g⁻¹ over 6000 cycles). As a proof-of-concept, a zinc metal-free full battery is successfully demonstrated, which delivers the highest capacity of 131.7 mAh g⁻¹ (mass containing anodic and cathodic) and energy density of 97.1 Wh kg⁻¹ compared to all reported aqueous “rocking-chair” ZIBs. Furthermore, a long cycling span of 6000 cycles is obtained with capacity retention reaching up to 92.1%, which is impressive. This work is expected to provide new moment toward V-based materials for “rocking-chair” ZIBs.     

A Novel Hexaazatriphenylene Carboxylate with Compatible Binder as Anode for High-Performance Organic Potassium-Ion Batteries

Organic electrode materials have attracted tremendous attention for potassium-ion batteries (PIBs). Whereas, high-performance anodes are scarcely reported. Herein, a novel hexaazatriphenylene potassium carboxylate (HAT-COOK) is proposed as anode materials for PIBs. The rich CN/CO bonds guarantee the high theoretical capacity. It is also demonstrated HAT-COOK is more compatible with the water-soluble binders than the hydrophobic fluoride binders, forming homogenous electrode film, maintaining structural integrity, and achieving stable cycling and excellent rate performance. With the compatible binder, each HAT-COOK molecule can involve 6-electron transfer, yielding a high reversible discharge capacity of 288 mAh g⁻¹ at 50 mA g⁻¹, excellent rate performance (105 mAh g⁻¹ at 5000 mA g⁻¹), and good cycling stability (143 mAh g⁻¹ after 500 cycles at 500 mA g⁻¹). These results highlight the importance of the delicate molecular design of organic molecules as well as the optimization of binders to achieve high-performance PIBs.     

Single-Atom Cadmium-N4 Sites for Rechargeable Li–CO2 Batteries with High Capacity and Ultra-Long Lifetime

The rechargeable Li–CO₂ battery shows great potential in civil, military, and aerospace fields due to its high theoretical energy density and CO₂ capture capability. To facilitate the practical application of Li–CO₂ battery, the design of efficient, low-cost, and robust non-noble metal cathodes to boost CO₂ reduction/evolution kinetics is highly desirable yet remains a challenge. Herein, single-atom cadmium is reported with a Cd-N₄ coordination structure enable rapid kinetics of both the discharge and recharge process when employed as a cathode catalyst, and thus facilitates exceptional rate performance in a Li–CO₂ battery, even up to 10 A g⁻¹, and remains stable at a high current density (100 A g⁻¹). An unprecedented discharge capacity of 160045 mAh g⁻¹ is attained at 500 mA g⁻¹. Excellent cycling stability is maintained for 1685 and 669 cycles at 1 A g⁻¹ and capacities of 0.5 and 1 Ah g⁻¹, respectively. Density functional theory calculations reveal low energy barriers for both Li₂CO₃ formation and decomposition reactions during the respective discharge and recharge process, evidencing the high catalytic activity of single Cd sites. This study provides a simple and effective avenue for developing highly active and stable single-atom non-precious metal cathode catalysts for advanced Li–CO₂ batteries.     

Neuromorphic Carbon for Fast and Durable Potassium Storage

Graphitic carbon materials (GCs) are attractive as anodes for the industrialization of potassium ion batteries (PIBs). However, the poor cycle and rate performance of GC-based anodes hinder the development of PIBs. In this study, inspired by the nervous system, neuromorphic GCs (NGCs) are designed to use as potassium anodes with high cycling stability and excellent rate performance. The inherent neuromorphic nature of NGCs enables fast signal transmission via multiwalled carbon nanotubes (MWCNTs), which serve as efficient pathways for electronic transmission. Meanwhile, the low-stress properties of hollow carbon spheres effectively support the cycling stability of PIBs. As a result, NGC-based potassium anodes achieved an unprecedented cycle life over 18 months (2400 cycles) with a reversible capacity of up to 225 mAh g⁻¹ at a current density of 100 mA g⁻¹. Moreover, the novel anode exhibits exceptional rate performance (73.6 mAh g⁻¹ at 1 A g⁻¹). The research presented here offers a practical and straightforward method for potassium's long-term and high-rate storage and beyond.     

Multicore–Shell Bi@N‐doped Carbon Nanospheres for High Power Density and Long Cycle Life Sodium‐ and Potassium‐Ion Anodes

Bismuth (Bi) is an attractive material as anodes for both sodium‐ion batteries (NIBs) and potassium‐ion batteries (KIBs), because it has a high theoretical gravimetric capacity (386 mAh g^?1) and high volumetric capacity (3800 mAh L^?1). The main challenges associated with Bi anodes are structural degradation and instability of the solid electrolyte interphase (SEI) resulting from the huge volume change during charge/discharge. Here, a multicore–shell structured Bi@N‐doped carbon (Bi@N‐C) anode is designed that addresses these issues. The nanosized Bi spheres are encapsulated by a conductive porous N‐doped carbon shell that not only prevents the volume expansion during charge/discharge but also constructs a stable SEI during cycling. The Bi@N‐C exhibits unprecedented rate capability and long cycle life for both NIBs (235 mAh g^?1 after 2000 cycles at 10 A g^?1) and KIBs (152 mAh g^?1 at 100 A g^?1). The kinetic analysis reveals the outstanding electrochemical performance can be attributed to significant pseudocapacitance behavior upon cycling.     

A General Route for Encapsulating Monodispersed Transition Metal Phosphides into Carbon Multi-Chambers toward High-Efficient Lithium-Ion Storage with Underlying Mechanism Exploration

Transition metal phosphides (MP_x) with high theoretical capacities and low cost are regarded as the most promising anodes for lithium-ion batteries (LIBs), but the large volume variations and sluggish kinetics largely restrict their development. To solve the above challenges, herein a generic but effective method is proposed to encapsulate various monodispersed MP_x into flexible carbon multi-chambers (MP_x@NC, MNi, Fe, Co, and Cu, etc.) with pre-reserved voids, working as anodes for LIBs and markedly boosting the Li⁺ storage performance. Ni₂P@NC, one representative example of MP_x@NC anode, shows high reversible capacity (613 mAh g⁻¹, 200 cycles at 0.2 A g⁻¹), and superior cycle stability (475 mAh g⁻¹, 800 cycles at 2 A g⁻¹). Full cell coupled with LiFePO₄ displays a high reversible capacity (150.1 mAh g⁻¹ at 0.1 A g⁻¹) with stable cycling performance. In situ X-ray diffraction and transmission electron microscope techniques confirm the reversible conversion reaction mechanism and robust structural integrity, accounting for enhanced rate and cycling performance. Theoretical calculations reveal the synergistic effect between MP_x and carbon shells, which can significantly promote electron transfer and reduce diffusion energy barriers, paving ways to design high-energy-density materials for energy storage systems.     

Novel Designed MnS-MoS2 Heterostructure for Fast and Stable Li/Na Storage:Insights into the Advanced Mechanism Attributed to Phase Engineering

Combining 2D MoS₂ with other transition metal sulfide is a promising strategy to elevate its electrochemical performances. Herein, heterostructures constructed using MnS nanoparticles embedded in MoS₂ nanosheets (denoted as MnS-MoS₂) are designed and synthesized as anode materials for lithium/sodium-ion batteries via a facile one-step hydrothermal method. Phase transition and built-in electric field brought by the heterostructure enhance the Li/Na ion intercalation kinetics, elevate the charge transport, and accommodate the volume expansion. The sequential phase transitions from 2H to 3R of MoS₂ and α to γ of MnS are revealed for the first time. As a result, the MnS-MoS₂ electrode delivers outstanding specific capacity (1246.2 mAh g⁻¹ at 1 A g⁻¹), excellent rate, and stable long-term cycling stability (397.2 mAh g⁻¹ maintained after 3000 cycles at 20 A g⁻¹) in Li-ion half-cells. Superior cycling and rate performance are also presented in sodium half-cells and Li/Na full cells, demonstrating a promising practical application of the MnS-MoS₂ electrode. This work is anticipated to afford an in-depth comprehension of the heterostructure contribution in energy storage and illuminate a new perspective to construct binary transition metal sulfide anodes.     

Intercalative Motifs-Induced Space Confinement and Bonding Covalency Enhancement Enable Ultrafast and Large Sodium Storage

Alloying-type metal sulfides with high theoretical capacities are promising anodes for sodium-ion batteries, but suffer from sluggish sodiation kinetics and huge volume expansion. Introducing intercalative motifs into alloying-type metal sulfides is an efficient strategy to solve the above issues. Herein, robust intercalative In S motifs are grafted to high-capacity layered Bi₂S₃ to form a cation-disordered (BiIn)₂S₃, synergistically realizing high-rate and large-capacity sodium storage. The In S motif with strong bonding serves as a space-confinement unit to buffer the volume expansion, maintaining superior structural stability. Moreover, the grafted high-metallicity Indium increases the bonding covalency of Bi S, realizing controllable reconstruction of Bi S bond during cycling to effectively prevent the migration and aggregation of atomic Bi. The novel (BiIn)₂S₃ anode delivers a high capacity of 537 mAh g⁻¹ at 0.4 C and a superior high-rate stability of 247 mAh g⁻¹ at 40 C over 10000 cycles. Further in situ and ex situ characterizations reveal the in-depth reaction mechanism and the breakage and formation of reversible Bi S bonds. The proposed space confinement and bonding covalency enhancement strategy via grafting intercalative motifs can be conducive to developing novel high-rate and large-capacity anodes.