Interfacial and Electronic Modulation via Localized Sulfurization for Boosting Lithium Storage Kinetics

In-situ conversion of BiOBr to Br-doped BiOCl nanosheets for "rocking chair" zinc-ion battery

Developing insertion-type anodes is essential for designing high-performance "rocking chair" zinc-ion batteries. BiOCl shows great potential as an insertion-type anode material for Zn2+ storage due to its high specific capacity and unique layered structure. However, the development of BiOCl has been significantly hampered by its poor stability and kinetics during cycling. In this study, Br-doped and carbon-coated BiOCl ultrathin nanosheets (Br-BiOCl@NC) are synthesized as high-performance anodes. The ultrathin nanosheet morphology facilitates Zn2+/H+ transfer and the Br doping reduces the Zn2+/H+ diffusion barrier. Additionally, the carbon coating enhances the electronic transfer. Furthermore, an insertion-conversion mechanism involving H+ and Zn2+ storage is revealed by ex-situ tests. Therefore, Br-BiOCl@NC exhibits a high discharge capacity of 174 mA h/g at 500 mA/g without capacity degradation after 1000 cycles. The Br-BiOCl@NC//MnO2 full cell presents a discharge capacity of ≈ 120 mA h/g at 200 mA/g. This work offers valuable insights for the design of high-performance insertion-type anode materials in zinc-ion batteries.

A Cellulose Pore Adsorption Strategy to Prepare CoFe/Co8FeS8 Heterostructures into N/S-Doped Carbon Cavities for Enhancing ORR/OER Performance

To address the complex synthesis and metal agglomeration for partially sulfurized heterostructures, a cellulose pore adsorption strategy is proposed to fabricate CoFe/Co8FeS8 heterostructures in N/S-doped biocarbon cavities. In the absence of chelating agents, the porosity and active groups of cellulose enable the preadsorption of metal ions and N/S sources in willow catkin via ion adsorption and hydrogen bonding, respectively. The spatial confinement provided by biopores facilitates incomplete metal sulfuration while effectively preventing metal migration/aggregation. This catalyst demonstrates superior oxygen evolution and reduction reaction performance, with a minimal potential gap of 0.72 V in 0.1 mol·L-1 KOH, exceeding commercial Pt/C+RuO2. When applied in Zn-air batteries, the optimized electrode affords a high specific capacity of 803 mAh·gZn-1 and long-term cycling durability exceeding 500 h. These enhancements are attributed to the self-driven electron transfer between CoFe and Co8FeS8, and from the core to the carbon shell, which induces local electron enrichment at the interface, influencing the adsorption of key reactants. Besides, the ample N/S heteroatoms in the carbon shell further unlock extra active sites, and carbon cavities also inhibit metal nanoparticle shedding during testing, thereby enhancing electrocatalytic stability. This work offers a simple yet effective strategy for designing advanced heterostructure electrocatalysts.

Nanoporous Graphene with Encapsulated Multicomponent Carbide as High-Performance Binder-Free Lithium-Ion Battery Anodes

Metal carbides are considered attractive lithium-ion battery (LIB) anode materials. Their potential practical application, however, still needs nanostructure optimization to further enhance the Li-storage capacity, especially under large current densities. Herein, a nanoporous structured multi-metal carbide is designed, which is encapsulated in a 3D free-standing nanotubular graphene film (MnNiCoFe-MoC@NG). This free-standing composite anode with a high surface area not only provides more active Li+ storage sites but also effectively prevents the agglomeration or detachment of active material in traditional powder-based electrodes. Moreover, the free-standing design does not require additional binders, conductive agents, or even current collectors when used as LIB anode. As a result, the MnNiCoFe-MoC@NG anode exhibits a high specific capacity of 1129.2 mAh g-1 at 2 A g-1 and maintains a stable capacity of 512.9 mAh g-1 after 2900 cycles of 5 A g-1, which is higher than most reported MoxC-based anodes. Furthermore, the anode exhibits superb low-temperature performance at both 0 and -20 °C, especially at large current densities. These properties make the free-standing anode very promising in fast charging and low-temperature applications.

Localized nitride strategy to construct interfacial and electronic modulated WO3/WN nanoparticles for superior lithium-ion storage

The interfacial effect is important for the tungsten trioxide (WO3)-based anode to achieve superior lithium-ion storage performance. Herein, the interfacial effect was constructed by in-situ surface direct nitridation reaction at 600 ℃ for 30 min of the as-synthesis WO3 nanoparticles (WO3/WN). X-ray photoelectron spectroscopy (XPS) analysis confirms evident chemical interaction between WO3 and WN via the interfacial covalent bond (WON). This WO3/WN anode shows a distinct interfacial effect for an efficient interatomic electron migration. Electrochemical kinetic analysis shows enhanced pseudocapacitance contribution. The galvanostatic intermittent titration technique (GITT) result demonstrates improved charge transfer kinetics. Ex-situ X-ray diffraction (XRD) analysis reveals the reversible oxidation and reduction reaction of the WO3/WN anode. The density functional theory (DFT) result shows that the evident interfacial bonding effect can enhance the electrochemical reaction kinetics of the WO3/WN anode. The discharge capacity can reach up to 546.9 mA h g-1 at 0.1 A g-1 after 200 cycles. After 2000 cycles, the capacity retention is approximately 85.97 % at 1.0 A g-1. In addition, the WO3/WN full cell (LiFePO4/C//WO3/WN) demonstrates excellent rate capability and capacity retention ratio. This in-situ surface nitridation strategy is an effective solution for designing an oxide-based anode with good electrochemical performance and beyond.

Reduced graphene oxide-wrapped ZnS-SnS2 heterojunction bimetallic hollow cubic boxes as high-magnification and long lifespan supercapacitor anode materials

Metal sulfides have attracted extensive attention due to their excellent electrochemical performance. However, issues such as poor conductivity and severe volume expansion during charge and discharge processes affect the applications of sulfides as electrode materials. Here, a combination of coprecipitation and high-temperature sulfidation methods are employed to synthesize a ZnS-SnS2 composite with a hollow cubic structure, which is further composited with reduced graphene oxide (RGO) to form ZnS-SnS2 hollow cubic boxes encapsulated in a conductive framework of reduced graphene oxide (RGO) (denoted as ZnS-SnS2@RGO) for electrode materials. The hollow structure effectively alleviates the pulverization of ZnS-SnS2@RGO caused by volume expansion during charge and discharge processes. The heterogeneous structure formed by ZnS and SnS2 effectively reduces the electron transfer resistance of the material. The use of RGO wrapping enhances the conductivity of the ZnS-SnS2 hollow cubic boxes, and RGO's dispersion effect on the ZnS-SnS2 cubes improves particle agglomeration, further mitigating volume expansion of the material. These results indicate the outstanding electrochemical performance of heterostructural ZnS-SnS2 hollow cubic electrodes encapsulated with reduced graphene oxide as a conductive framework. The fabrication process provides a novel approach for addressing volume expansion and poor conductivity issues in other pseudocapacitive materials.

Advanced Insights on MXenes: Categories, Properties, Synthesis, and Applications in Alkali Metal Ion Batteries

The development and optimization of promising anode material for next-generation alkali metal ion batteries are significant for clean energy evolution. 2D MXenes have drawn extensive attention in electrochemical energy storage applications, due to their multiple advantages including excellent conductivity, robust mechanical properties, hydrophilicity of its functional terminations, and outstanding electrochemical storage capability. In this review, the categories, properties, and synthesis methods of MXenes are first outlined. Furthermore, the latest research and progress of MXenes and their composites in alkali metal ion storage are also summarized comprehensively. A special emphasis is placed on MXenes and their hybrids, ranging from material design and fabrication to fundamental understanding of the alkali ion storage mechanisms to battery performance optimization strategies. Lastly, the challenges and personal perspectives of the future research of MXenes and their composites for energy storage are presented.

NH4 + Pre-Intercalation and Mo Doping VS2 to Regulate Nanostructure and Electronic Properties for High Efficiency Sodium Storage

Sodium-ion hybrid capacitors (SIHCs) have attracted much attention due to integrating the high energy density of battery and high out power of supercapacitors. However, rapid Na+ diffusion kinetics in cathode is counterbalanced with sluggish anode, hindering the further advancement and commercialization of SIHCs. Here, aiming at conversion-type metal sulfide anode, taking typical VS2 as an example, a comprehensive regulation of nanostructure and electronic properties through NH4 + pre-intercalation and Mo-doping VS2 (Mo-NVS2) is reported. It is demonstrated that NH4 + pre-intercalation can enlarge the interplanar spacing and Mo-doping can induce interlayer defects and sulfur vacancies that are favorable to construct new ion transport channels, thus resulting in significantly enhanced Na+ diffusion kinetics and pseudocapacitance. Density functional theory calculations further reveal that the introduction of NH4 + and Mo-doping enhances the electronic conductivity, lowers the diffusion energy barrier of Na+, and produces stronger d-p hybridization to promote conversion kinetics of Na+ intercalation intermediates. Consequently, Mo-NVS2 delivers a record-high reversible capacity of 453 mAh g-1 at 3 A g-1 and an ultra-stable cycle life of over 20 000 cycles. The assembled SIHCs achieve impressive energy density/power density of 98 Wh kg-1/11.84 kW kg-1, ultralong cycling life of over 15000 cycles, and very low self-discharge rate (0.84 mV h-1).

First-principles study of the discharge electrochemical and catalytic performance of the sulfur cathode host Fe0.875M0.125S2 (M = Ti, V)

Lithium-sulfur batteries (LSBs) are one of the most promising energy storage devices with high energy density. However, their application and commercialization are hampered by the slow Li-S redox chemistry. Fe0.875M0.125S2 (M = Ti, V), as the sulfur cathode host, enhances the Li-S redox chemistry. FeS2 with Pa3̄ is transformed into Li2FeS2 with P3̄m1 after discharge. The structure changes and physicochemical properties during Fe0.875M0.125S2 discharge process are further investigated to screen out the sulfur cathode host materials with the best comprehensive properties. The discharge structure of Fe0.875M0.125S2 is verified by the thermodynamic stability of Li-deficient phases, voltage and capacity based on Monte Carlo methods. Fe0.875M0.125S2 with Pa3̄ is transformed into Li2Fe0.875M0.125S2 with P3̄m1 after discharge. Using the first-principles calculations, the physicochemical properties of Li2Fe0.875M0.125S2 are systematically investigated, including the formation energy, voltage, theoretical capacity, electrical conductivity, Li+ diffusion, catalytic performance and Li2S oxidation decomposition. The average redox voltage of Li2Fe0.875V0.125S2 is higher than that of Li2Fe0.875Ti0.125S2. Li2Fe0.875M0.125S2 shows metallic properties. Li2Fe0.875V0.125S2 is more beneficial to the reduction reaction of Li2S2 and Li2S oxidation decomposition. Fe0.875V0.125S2 has more potential as the sulfur cathode host than Fe0.875Ti0.125S2 in LSBs. A new strategy for the selection of the sulfur cathode host material for LSBs is provided by this work.

Discovery of Two-dimensional Hexagonal MBene HfBO and Exploration on its Potential for Lithium-Ion Storage

The practical applications of two-dimensional (2D) transition-metal borides (MBenes) have been severely hindered by the lack of accessible MBenes because of the difficulties in the selective etching of traditional ternary MAB phases with orthorhombic symmetry (ort-MAB). Here, we discover a family of ternary hexagonal MAB (h-MAB) phases and 2D hexagonal MBenes (h-MBenes) by ab initio predictions and experiments. Calculations suggest that the ternary h-MAB phases are more suitable precursors for MBenes than the ort-MAB phases. Based on the prediction, we report the experimental synthesis of h-MBene HfBO by selective removal of In from h-MAB Hf2 InB2 . The synthesized 2D HfBO delivered a specific capacity of 420 mAh g-1 as an anode material in lithium-ion batteries, demonstrating the potential for energy-storage applications. The discovery of this h-MBene HfBO added a new member to the growing family of 2D materials and provided opportunities for a wide range of novel applications.

A Potential Polycarbonyl Polyimide as Anode Material for Lithium-Ion Batteries

Organic polymers have been considered reliable candidates for lithium storage due to their high capacity and lack of volume expansion. Compared with other organic polymers, polyimide has become a very promising electrode material for lithium-ion batteries (LIBs) because of its easy synthesis, customizable structure and structural stability. A large number of studies have confirmed that the benzene ring structure of polyimide has strong lithium storage capacity as an anode material. Hence, we designed and synthesized polyimide organic polymer (PBPAQ) for the first time. The unique spherical flower structure of this material enhances the interaction between the electrode material and the electrolyte by increasing the contact area. The PBPAQ anode has a specific discharge capacity of 738 mAh g-1 after 100 cycles at 0.1 A g-1 . The excellent lithium storage performance of this material laid a foundation for the research of the anode of LIBs in the future.

High-Performance Alkali Metal Ion Storage in Bi2Se3 Enabled by Suppression of Polyselenide Shuttling Through Intrinsic Sb-Substitution Engineering

Bismuth selenide holds great promise as a kind of conversion-alloying-type anode material for alkali metal ion storage because of its layered structure with large interlayer spacing and high theoretical specific capacity. Nonetheless, its commercial development has been significantly hammered by the poor kinetics, severe pulverization, and polyselenide shuttle during the charge/discharge process. Herein, Sb-substitution and carbon encapsulation strategies are simultaneously employed to synthesize Sb_xBi_2-xSe₃ nanoparticles decorated on Ti₃C₂T_x MXene with encapsulation of N-doped carbon (Sb_xBi_2-xSe₃/MX⊂NC) as anodes for alkali metal ion storage. The superb electrochemical performances could be assigned to the cationic displacement of Sb³⁺ that effectively inhibits the shuttling effect of soluble polyselenides and the confinement engineering that alleviates the volume change during the sodiation/desodiation process. When used as anodes for sodium- and lithium-ion batteries, the Sb_0.4Bi_1.6Se₃/MX⊂NC composite exhibits superior electrochemical performances. This work offers valuable guidance to suppress the shuttling of polyselenides/polysulfides in high-performance alkali metal ion batteries with conversion/alloying-type transition metal sulfide/selenide anode materials.

In-situ catalytic mechanism coupling quantum dot effect for achieving high-performance sulfide anode in potassium-ion batteries

Though numerous framework structures have been constructed to strengthen the reaction kinetics and durability, the inevitable generation of polysulfide dissolution during conversion-process can cause irreparable destruction to ion-channel and crystal structure integrality, which has become a huge obstacle to the application of metal-sulfide in potassium-ion batteries. Herein, the quantum dot structure with catalytic conversion capability is synchronously introduced into the design of FeS₂ anode materials to heighten its K⁺-storage performance. The constructed quantum dot structure anchored by the graphene with space-confinement effect can shorten the ion diffusion path and enlarge the active area, thus accelerating the K⁺-ions transmission kinetics and absorption action, respectively. The intermediate phase of formed Fe-nanoclusters possesses high-active catalysis ability, which can effectively suppress the polysulfide shuttle combined with the enhanced absorption effect, fully guaranteeing the structure stability and cycling reversibility. Predictably, the fabricated quantum dot FeS₂ can express a prominent advantage in rapid potassiation/depotassiation processes (518.1 mAh g^-1, 10 A g^-1) and a superior cycling lifespan with gratifying reversible capacity at superhigh rate (177.7 mAh g^-1, 9000 cycles, 5 A g^-1). Therefore, engineering quantum dot structure with self-induced catalysis action for detrimental polysulfide is an achievable strategy to implement high-performance sulfide anode materials for K-ions accommodation.

Interface Engineering of Fe7S8/FeS2 Heterostructure in situ Encapsulated into Nitrogen-Doped Carbon Nanotubes for High Power Sodium-Ion Batteries

Heterostructure engineering combined with carbonaceous materials shows great promise toward promoting sluggish kinetics, improving electronic conductivity, and mitigating the huge expansion of transition metal sulfide electrodes for high-performance sodium storage. Herein, the iron sulfide-based heterostructures in situ hybridized with nitrogen-doped carbon nanotubes (Fe7S8/FeS2/NCNT) have been prepared through a successive pyrolysis and sulfidation approach. The Fe7S8/FeS2/NCNT heterostructure delivered a high reversible capacity of 403.2 mAh g-1 up to 100 cycles at 1.0 A g-1 and superior rate capability (273.4 mAh g-1 at 20.0 A g-1) in ester-based electrolyte. Meanwhile, the electrodes also demonstrated long-term cycling stability (466.7 mAh g-1 after 1,000 cycles at 5.0 A g-1) and outstanding rate capability (536.5 mAh g-1 at 20.0 A g-1) in ether-based electrolyte. This outstanding performance could be mainly attributed to the fast sodium-ion diffusion kinetics, high capacitive contribution, and convenient interfacial dynamics in ether-based electrolyte.

In Situ Growth of Iron Sulfide on Fast Charge Transfer V2 C-MXene for Superior Sodium Storage Anodes

Due to the upstream pressure of lithium resources, low-cost sodium-ion batteries (SIBs) have become the most potential candidates for energy storage systems in the new era. However, anode materials of SIBs have always been a major problem in their development. To address this, V₂ C/Fe₇ S₈ @C composites with hierarchical structures prepared via an in situ synthesis method are proposed here. The 2D V₂ C-MXene as the growth substrate for Fe₇ S₈  greatly improves the rate capability of SIBs, and the carbon layer on the surface provides a guarantee for charge-discharge stability. Unexpectedly, the V₂ C/Fe₇ S₈ @C anode achieves satisfactory sodium storage capacity and exceptional rate performance (389.7 mAh g^-1  at 5 A g^-1 ). The sodium storage mechanism and origin of composites are thoroughly studied via ex situ characterization techniques and first-principles calculations. Furthermore, the constructed sodium-ion capacitor assembled with N-doped porous carbon delivers excellent energy density (135 Wh kg^-1 ) and power density (11 kW kg^-1 ), showing certain practical value. This work provides an advanced system of sodium storage anode materials and broadens the possibility of MXene-based materials in the energy storage.

Insights into the electrochemical properties of Li2FeS2 after FeS2 discharging

All-solid-state lithium-sulfur batteries (ASSLSBs) have high reversible characteristics owing to the high redox potential, high theoretical capacity, high electronic conductivity, and low Li⁺ diffusion energy barrier in the cathode. Monte Carlo simulations with cluster expansion, based on the first-principles high-throughput calculations, predicted a phase structure change from Li₂FeS₂ (P3̄M1) to FeS₂ (PA3̄) during the charging process. LiFeS₂ is the most stable phase structure. The structure of Li₂FeS₂ after charging was FeS₂ (P3̄M1). By applying the first-principles calculations, we explored the electrochemical properties of Li₂FeS₂ after charging. The redox reaction potential of Li₂FeS₂ was 1.64 to 2.90 V, implying a high output voltage of ASSLSBs. Flatter voltage step plateaus are important for improving the electrochemical performance of the cathode. The charge voltage plateau was the highest from Li_0.25FeS₂ to FeS₂ and followed from Li_0.375FeS₂ to Li_0.25FeS₂. The electrical properties of Li_xFeS₂ remained metallic during the Li₂FeS₂ charging process. The intrinsic Li Frenkel defect of Li₂FeS₂ was more conducive to Li⁺ diffusion than that of the Li₂S Schottky defect and had the largest Li⁺ diffusion coefficient. The good electronic conductivity and Li⁺ diffusion coefficient of the cathode implied a better charging/discharging rate performance of ASSLSBs. This work theoretically verified the FeS₂ structure after Li₂FeS₂ charging and explored the electrochemical properties of Li₂FeS₂.

3D Sodiophilic Ti3C2 MXene@g-C3N4 Hetero-Interphase Raises the Stability of Sodium Metal Anodes

Owing to several advantages of metallic sodium (Na), such as a relatively high theoretical capacity, low redox potential, wide availability, and low cost, Na metal batteries are being extensively studied, which are expected to play a major role in the fields of electric vehicles and grid-scale energy storage. Although considerable efforts have been devoted to utilizing MXene-based materials for suppressing Na dendrites, achieving a stable cycling of Na metal anodes remains extremely challenging due to, for example, the low Coulombic efficiency (CE) caused by the severe side reactions. Herein, a g-C₃N₄ layer was attached in situ on the Ti₃C₂ MXene surface, inducing a surface state reconstruction and thus forming a stable hetero-interphase with excellent sodiophilicity between the MXene and g-C₃N₄ to inhibit side reactions and guide uniform Na ion flux. The 3D construction can not only lower the local current density to facilitate uniform Na plating/stripping but also mitigate volume change to stabilize the electrolyte/electrode interphase. Thus, the 3D Ti₃C₂ MXene@g-C₃N₄ nanocomposite enables much enhanced average CEs (99.9% at 1 mA h cm^-2, 0.5 mA cm^-2) in asymmetric half cells, long-term stability (up to 700 h) for symmetric cells, and stable cycling (up to 800 cycles at 2 C), together with outstanding rate capability (up to 20 C), of full cells. The present study demonstrates an approach in developing practically high performance for Na metal anodes.

Tin nanoparticle in-situ decorated on nitrogen-deficient carbon nitride with excellent sodium storage performance

Tin (Sn)-based electrodes, featuring high electrochemical activity and suitable voltage plateau, gain tremendous attention as promising anode materials for sodium-ion batteries. However, the application of Sn-based electrodes has been largely restricted by the serious pulverization upon repeated cycling due to their large volume expansion, especially at high current densities. Herein, a unique three-dimensional decorated structure was designed, containing ultrafine Sn nanoparticles and nitrogen-deficient carbon nitride (Sn/D-C₃N₄), to efficiently alleviate the expansion stress and prevent the aggregation of Sn nanoparticles. Furthermore, the density functional theory calculations have proved the high sodium adsorption ability and improved diffusion kinetics through the hybridization of D-C₃N₄ with Sn nanoparticles. Further combining the high electronic/ionic conductivity provided by the porous C₃N₄ matrix, high charge contribution from capacitive behavior, and high sodium storage activity of ultrafine Sn nanoparticles, the resultant Sn/D-C₃N₄ can achieve an ultrahigh reversible capacity of 518.3 mA g^-1 after 300 cycles at 1.0 A g^-1, and even maintaining a reversible capacity of 436.1 mAh g^-1 up to 500 cycles (5.0 A g^-1). What's more, the optimized Sn/D-C₃N₄∥Na₃V₂(PO₄)₃/C full cell can keep a high capacity retention of 87.1% at 1.0 A g^-1 even after 5000 cycles, manifesting excellent sodium storage performance.

Intercalation Reaction in Amorphous Layer-Wrapped Ni0.2Mo0.8N/Ni3N Heterostructure Toward Efficient Lithium-Ion Storage

Transition metal nitrides (TMNs) with high specific capacity and electric conductivity have drawn considerable attention as electrode materials of lithium-ion batteries (LIBs). However, the cycling stability of most TMNs is not satisfactory, which was caused by the large volume variation during cycles due to their intrinsic conversion reaction mechanism. Herein, by rational design, a much stable tremella-like Ni_0.2Mo_0.8N/Ni₃N heterostructure with amorphous Ni_0.2Mo_0.8N wrapped layer has been fabricated. The Ni₃N particles worked as pillars to support the Ni_0.2Mo_0.8N material as well as conductive medium to facilitate ionic and electronic transport. The amorphous layer can relieve the structural stress of Ni_0.2Mo_0.8N during cycles. Moreover, an exotic intercalation-type reaction mechanism in the ternary nitride Ni_0.2Mo_0.8N was revealed by a series ex situ and in situ characterization. Profiting from these advantages, the Ni_0.2Mo_0.8N/Ni₃N heterostructure anode displays an outstanding electrochemical performance with a high initial reversible discharge capacity of 1001.6 mA h g^-1 at 0.1 A g^-1, excellent cycle stability of 695.5 mA h g^-1 at 2 A g^-1 after 600 cycles, and superior rate capability of 595.3 mA h g^-1 at a high current density of 5 A g^-1. This work provides a new insight for designing high efficiency LIBs based on intercalation reaction for practical applications.

Enabling Reversible Reaction by Uniform Distribution of Heterogeneous Intermediates on Defect-Rich SnSSe/C Layered Heterostructure for Ultralong-Cycling Sodium Storage

2D layered Sn-based materials have attracted enormous attention due to their remarkable performance in sodium-ion batteries. Nevertheless, this promising candidate involves a complex Na⁺ -storage process with multistep conversion-alloying reactions, which induces the uneven dispersion of heterogeneous intermediate accompanied by severe agglomeration of metallic Sn⁰ , inescapably resulting in poor reaction reversibility with sluggish rate capability and inferior cyclic lifespan. Herein, a delicately layered heterostructure SnSSe/C consisting of defect-rich SnSSe and graphene is designed and successfully achieved via a facile hydrothermal process. The equal anionic substitution of Se in SnSSe crystal can trigger numerous defects, which can not only facilitate Na⁺ diffusion but also accelerate the nucleation process by inducing quantum-dot-level uniform distribution of heterogeneous intermediates, Na₂ Se/Na₂ S and Sn⁰ . Concurrently, in situ formed uniform Na₂ Se/Na₂ S grain boundaries confined by this unique layered heterostructure may effectively suppress the agglomeration of metallic Sn⁰ nanograins and boost the reversibility of conversion-alloying reaction. As a result, the SnSSe/C displays significant improvement in Na-storage performance, in terms of remarkable rate capability and ultralong cycling lifespan. This work, focusing on controlling intermediate distribution, provides an effective strategy to boost reaction reversibility, which can be wildly employed in conversion-based electrodes for energy storage regions.

Rational Design of Space-Confined Mn-Based Heterostructures with Synergistic Interfacial Charge Transport and Structural Integrity for Lithium Storage

Manganese-based compounds are expected to become promising candidates for lithium-ion battery anodes by virtue of their high theoretical specific capacity and low conversion potential. However, their application is hindered by their inferior electrical conductivity and drastic volume variations. In this work, a unique heterostructure composed of MnO and MnS spatially confined in pyrolytic carbon microspheres (MnO@MnS/C) was synthesized through an integrated solvothermal method, calcination, and low-temperature vulcanization technology. In this architecture, heterostructured MnO@MnS nanoparticles (∼10 nm) are uniformly embedded into the carbonaceous microsphere matrix to maintain the structural stability of the composite. Benefiting from the combination of structural and compositional features, the MnO@MnS/C enables abundance in electrochemically active sites, alleviated volumetric variation, a rich conductive network, and enhanced lithium-ion diffusion kinetics, thus yielding remarkable rate capability (1235 mAh·g^-1 at 0.2 A·g^-1 and 608 mAh·g^-1 at 3.2 A·g^-1) and exceptional cycling stability (522 mAh·g^-1 after 2000 cycles at 3.0 A·g^-1) as a competitive anode material for lithium-ion batteries. Density functional theory calculations unveil that the heterostructure promotes the transfer of electrons with improved conductivity and also accelerates the migration of lithium ions with reduced polarization resistance. This combined with the enhancement brought by spatial confinement endows the MnO@MnS/C with remarkable lithium storage performance.

Heterogeneous Atoms Substituted Rock Salt Phase Mn1 -x Fex O Solid Solution with Rich Defects for Advanced Lithium-Ion Batteries

Heterogeneous atoms substitution is an efficient method for promoting Li⁺ storage of transition metal oxides. Herein, a series of Fe-substituted MnO solid solutions with different Fe contents are synthesized by a feasible solid-phase method. The synergistic effects between heterogeneous atoms and rich vacancies are synchronously obtained, which hold distinctive electronic structures and substantial active sites. When optimized Mn_0.55 Fe_0.45 O solid solution as anodes for lithium-ion batteries, pre-prepared electrodes exhibit reversible lithium storage of 1286.9 mAh g^-1 at 1 A g ^-1 after 400 cycles and even 628.1 mAh g^-1 at 2 A g^-1 after 1000 cycles. The LiCoO₂ //Mn_0.55 Fe_0.45 O full cells are assembled, achieving the reversible capacity of 130.2 and 111.3 mAh g^-1 after 150 cycles at 0.1 and 0.2 A g^-1 , respectively. Density functional theory calculations also authenticate that the electrochemical activity can be markedly boosted by the heterogeneous atoms substituted Mn_{1 -x} Fe_x O solid solution.

Electronic Structure Modulation in MoO2 /MoP Heterostructure to Induce Fast Electronic/Ionic Diffusion Kinetics for Lithium Storage

Transition metal oxides (TMOs) are considered as the prospective anode materials in lithium-ion batteries (LIBs). Nevertheless, the disadvantages, including large volume variation and poor electrical conductivity, obstruct these materials to meet the needs of practical application. Well-designed mesoporous nanostructures and electronic structure modulation can enhance the electron/Li-ions diffusion kinetics. Herein, a unique mesoporous molybdenum dioxide/molybdenum phosphide heterostructure nanobelts (meso-MoO₂ /MoP-NBs) composed of uniform nanoparticles is obtained by one-step phosphorization process. The Mott-Schottky tests and density functional theory calculations demonstrated that meso-MoO₂ /MoP-NBs possesses superior electronic conductivity. The detailed lithium storage mechanism (solid solution reaction for MoP and partial conversion for MoO₂ ), small change ratio of crystal structure and fast electronic/ionic diffusion behavior of meso-MoO₂ /MoP-NBs are systematically investigated by operando X-ray diffraction, ex situ transmission electron microscopy, and kinetic analysis. Benefiting from the synergistic effects, the meso-MoO₂ /MoP-NBs displays a remarkable cycling performance (515 mAh g^-1 after 1000 cycles at 1 A g^-1 ) and excellent rate capability (291 mAh g^-1 at 8 A g^-1 ). These findings can shed light on the behavior of the electron/ion regulation in heterostructures and provide a potential route to develop high-performance lithium-ion storage materials.

Preparation and controllable prelithiation of core–shell SnOx@C composites for high-performance lithium-ion batteries

The carbon coated SnOx with adjustable composition and coating thickness was firstly prepared. The initial coulombic efficiency and cycle stability were improved by chemical prelithiation and the full-cell showed better cycling and rate performance.

Sandwich-Structured Sn4P3@MXene Hybrid Anodes with High Initial Coulombic Efficiency for High-Rate Lithium-Ion Batteries

The high theoretical capacity makes metal phosphides appropriate anode candidates for Li-ion batteries, but their applications are restricted due to the limited structural instability caused by the huge volume change, as in other high-capacity materials. Here, we design an integrated electrode consisting of Sn₄P₃ nanoparticles sandwiched between transition-metal carbide (MXene) nanosheets. Tetramethylammonium hydroxide (TMAOH) plays an essential role in the formation of such sandwich structures by producing negatively charged MXene sheets with expanded layer spacings. The strong C-O-P oxygen bridge bond enables tight anchoring of Sn₄P₃ nanoparticles on the surface of MXene layers. The obtained Sn₄P₃-based nanocomposites exhibit high reversible capacity with an initial Coulombic efficiency of 82% and outstanding rate performance (1519 mAh cm^-3 at a current density of 5 A g^-1). The conductive and flexible MXene layers on both sides of Sn₄P₃ nanoparticles provide the desired electric conductivity and elastomeric space to accommodate the large volume change of Sn₄P₃ during lithiation. Therefore, the Sn₄P₃@MXene hybrid exhibits an enhanced cyclic performance of 820 mAh g^-1 after 300 cycles at a current density of 1 A g^-1.

Reconstructing Vanadium Oxide with Anisotropic Pathways for a Durable and Fast Aqueous K-Ion Battery

Aqueous potassium-ion batteries are long-term pursued, due to their excellent performance and intrinsic superiority in safe, low-cost storage for portable and grid-scale applications. However, the notorious issues of K-ion battery chemistry are the inferior cycling stability and poor rate performance, due to the inevitably destabilization of the crystal structure caused by K-ions with pronouncedly large ionic radius. Here, we resolve such issues by reconstructing commercial vanadium oxide (α-V₂O₅) into the bronze form, i.e., δ-K_0.5V₂O₅ (KVO) nanobelts, as cathode materials with layered structure of enlarged space and anisotropic pathways for K-ion storage. Specifically, it can deliver a high capacity as 116 mAh g^-1 at the 1 C-rate, an outstanding rate capacity of 65 mAh g^-1 at 50 C, and a robust cyclic stability with 88.2% capacity retention after 1,000 cycles at 1 C. When coupled with organic anode in a full-cell configuration, the KVO electrodes can output 95 mAh g^-1 at 1 C and cyclic stability with 77.3% capacity retention after 20,000 cycles at 10 C. According to experimental and calculational results, the ultradurable cyclic performance is assigned to the robust structural reversibility of the KVO electrode, and the ultrahigh-rate capability is attributed to the anisotropic pathways with improved electrical conductivity in KVO nanobelts. In addition, applying a 22 M KCF₃SO₃ water-in-salt electrolyte can impede the dissolving issues of the KVO electrode and further stabilize the battery cyclic performance. Lastly, the as-designed AKIBs can operate with superior low-temperature adaptivity even at -30 °C. Overall, the KVO electrode can serve as a paradigm toward developing more suitable electrode materials for high-performance AKIBs.

Chemical Heterointerface Engineering on Hybrid Electrode Materials for Electrochemical Energy Storage

The chemical heterointerfaces in hybrid electrode materials play an important role in overcoming the intrinsic drawbacks of individual materials and thus expedite the in-depth development of electrochemical energy storage. Benefiting from the three enhancement effects of accelerating charge transport, increasing the number of storage sites, and reinforcing structural stability, the chemical heterointerfaces have attracted extensive interest and the electrochemical performances of hybrid electrode materials have been significantly optimized. In this review, recent advances regarding chemical heterointerface engineering in hybrid electrode materials are systematically summarized. Especially, the intrinsic behaviors of chemical heterointerfaces on hybrid electrode materials are refined based on built-in electric field, van der Waals interaction, lattice mismatch and connection, electron cloud bias and chemical bond, and their combination. The strategies for introducing chemical heterointerfaces are classified into in situ local transformation, in situ growth, cosynthesis, and other strategy. The recent progress about the chemical heterointerfaces engineering specially focusing on metal-ion batteries, supercapacitors, and Li-S batteries are introduced in detail. Furthermore, the classification and characterization of chemical heterointerfaces are briefly described. Finally, the emerging challenges and perspectives about future directions of chemical heterointerface engineering are proposed.

S-Decorated Porous Ti3 C2 MXene Combined with In Situ Forming Cu2 Se as Effective Shuttling Interrupter in Na-Se Batteries

Given natural abundance of Na and superior kinetics of Se, Na-Se batteries have attracted much attention but still face the problem of shuttling effect of soluble intermediates. The first-principle calculations reveal the S-decorated Ti₃ C₂ exhibits increased binding energy to sodium polyselenides, suggesting a better capture and restriction on intermediates. The obtained Se@S-decorated porous Ti₃ C₂ (Se@S-P-Ti₃ C₂ ) exhibits a high reversible capacity of 765 mAh g^-1 at 0.1 A g^-1 (calculated based on Se), ≈1.2, 1.3, and 1.7 times of Se@porous Ti₃ C₂ (Se@P-Ti₃ C₂ ), Se@Ti₃ C₂ , and Se, respectively. It gives considerable capacity of 664 mAh g^-1 at 20 A g^-1 and impressive cycling stability over 2300 cycles with an ultralow capacity decay of 0.003% per cycle. The excellent electrochemical performance can be ascribed to the S-modified porous Ti₃ C₂ , which provides effective immobilization toward polyselenides, makes full use of nanosized Se, and alleviates volume expansion during sodiation/desodiation. Additionally, in situ forming Cu₂ Se can generate Cu nanoparticles through discharge process and then transform polyselenides into solid-phase Cu₂ Se, further suppressing the shuttling effect. This work provides a practical strategy to immobilize and transform sodium polyselenides for high-capacity and long-life Na-Se batteries.

Synergistic Interfacial and Doping Engineering of Heterostructured NiCo(OH)x-CoyW as an Efficient Alkaline Hydrogen Evolution Electrocatalyst

To achieve high efficiency of water electrolysis to produce hydrogen (H₂), developing non-noble metal-based catalysts with considerable performance have been considered as a crucial strategy, which is correlated with both the interphase properties and multi-metal synergistic effects. Herein, as a proof of concept, a delicate NiCo(OH)_x-Co_yW catalyst with a bush-like heterostructure was realized via gas-template-assisted electrodeposition, followed by an electrochemical etching-growth process, which ensured a high active area and fast gas release kinetics for a superior hydrogen evolution reaction, with an overpotential of 21 and 139 mV at 10 and 500 mA cm^-2, respectively. Physical and electrochemical analyses demonstrated that the synergistic effect of the NiCo(OH)_x/Co_yW heterogeneous interface resulted in favorable electron redistribution and faster electron transfer efficiency. The amorphous NiCo(OH)_x strengthened the water dissociation step, and metal phase of CoW provided sufficient sites for moderate H immediate adsorption/H₂ desorption. In addition, NiCo(OH)_x-Co_yW exhibited desirable urea oxidation reaction activity for matching H₂ generation with a low voltage of 1.51 V at 50 mA cm^-2. More importantly, the synthesis and testing of the NiCo(OH)_x-Co_yW catalyst in this study were all solar-powered, suggesting a promising environmentally friendly process for practical applications.

Theoretical study of the influence of doped niobium on the electronic properties of CsPbBr3

In the family of inorganic perovskite solar cells (PSCs), CsPbBr3 has attracted widespread attention due to its excellent stability under high humidity and high temperature conditions. However, power conversion efficiency (PCE) improvement of CsPbBr3-based PSCs is markedly limited by the large optical absorption loss coming from the wide band gap and serious charge recombination at interfaces and/or within the perovskite film. In this work, using density functional theory calculations, we systemically studied the electronic properties of niobium (Nb)-doped CsPbBr3 with different concentration ratios. As a result, it is found that doped CsPbBr3 compounds are metallic at high Nb doping concentration but semiconducting at low Nb doping concentration. The calculated electronic density of states shows that the conduction band is predominantly constructed of doped Nb. These characteristics make them very suitable for solar cell and energy storage applications.

Prelithiation: A Crucial Strategy for Boosting the Practical Application of Next-Generation Lithium Ion Battery

With the urgent market demand for high-energy-density batteries, the alloy-type or conversion-type anodes with high specific capacity have gained increasing attention to replace current low-specific-capacity graphite-based anodes. However, alloy-type and conversion-type anodes have large initial irreversible capacity compared with graphite-based anodes, which consume most of the Li⁺ in the corresponding cathode and severely reduces the energy density of full cells. Therefore, for the practical application of these high-capacity anodes, it is urgent to develop a commercially available prelithiation technique to compensate for their large initial irreversible capacity. At present, various prelithiation methods for compensating the initial irreversible capacity of the anode have been reported, but due to their respective shortcomings, large-scale commercial applications have not yet been achieved. In this review, we have systematically summarized and analyzed the advantages and challenges of various prelithiation methods, providing enlightenment for the further development of each prelithiation strategy toward commercialization and thus facilitating the practical application of high-specific-capacity anodes in the next-generation high-energy-density lithium-ion batteries.