Embedding MnO@Mn3 O4 Nanoparticles in an N-Doped-Carbon Framework Derived from Mn-Organic Clusters for Efficient Lithium Storage

Biomass-Derived Carbon Materials for Electrochemical Energy Storage

The environmental impact from the waste disposal has been widely concerned around the world. The conversion of wastes to useful resources is important for the sustainable society. As a typical family of wastes, biomass materials basically composed of collagen, protein and lignin are considered as useful resources for recycle and reuse. In recent years, the development of carbon material derived from biomasses, such as plants, crops, animals and their application in electrochemical energy storage have attracted extensive attention. Through the selection of the appropriate biomass, the optimization of the activation method and the control of the pyrolysis temperatures, carbon materials with desired features, such as high-specific surface area, variable porous framework, and controllable heteroatom-doping have been fabricated. Herein, this review summarized the preparation methods, morphologies, heteroatoms doping in the plant/animal-derived carbonaceous materials, and their application as electrode materials for secondary batteries and supercapacitors, and as electrode support for lithium-sulfur batteries. The challenges and prospects for the controllable synthesis and large-scale application of biomass-derived carbonaceous materials have also been outlooked.

Embedding Multiple Magnetic Components in Carbon Nanostructures via Metal-Oxo Cluster Precursor for High-Efficiency Low-/Middle-Frequency Electromagnetic Wave Absorption

With the advent of wireless technology, magnetic-carbon composites with strong electromagnetic wave (EMW) absorption capability in low-/middle-frequency range are highly desirable. However, it remains challenging for rational construction of such absorbers bearing multiple magnetic components that show uniform distribution and favorable magnetic loss. Herein, a facile metal-oxo cluster (MOC) precursor strategy is presented to produce high-efficiency magnetic carbon composites. Nanosized MOC Fe15 shelled with organic ligands is employed as a novel magnetic precursor, thus allowing in situ formation and uniform deposition of multicomponent magnetic Fe/Fe3O4@Fe3C and Fe/Fe3O4 nanoparticles on graphene oxides (GOs) and carbon nanotubes (CNTs), respectively. Owing to the good dispersity and efficient magnetic-dielectric synergy, quaternary Fe/Fe3O4@Fe3C-GO exhibits strong low-frequency absorption with RLmin of -53.5 dB at C-band and absorption bandwidth covering 3.44 GHz, while ultrahigh RLmin of -73.2 dB is achieved at X-band for ternary Fe/Fe3O4-CNT. The high performance for quaternary and ternary composites is further supported by the optimal specific EMW absorption performance (-15.7 dB mm-1 and -31.8 dB mm-1) and radar cross-section reduction (21.72 dB m2 and 34.37 dB m2). This work provides a new avenue for developing lightweight low-/middle-frequency EMW absorbers, and will inspire the investigation of more advanced EMW absorbers with multiple magnetic components and regulated microstructures.

Decoupling Activation and Transport by Electron-Regulated Atomic-Bi Harnessed Surface-to-Pore Interface for Vanadium Redox Flow Battery

Vanadium redox flow battery (VRFB) promises a route to low-cost and grid-scale electricity storage using renewable energy resources. However, the interplay of mass transport and activation processes of high-loading catalysts makes it challenging to drive high-performance density VRFB. Herein, a surface-to-pore interface design that unlocks the potential of atomic-Bi-exposed catalytic surface via decoupling activation and transport is reported. The functional interface accommodates electron-regulated atomic-Bi catalyst in an asymmetric Bi─O─Mn structure that expedites the V3+ /V2+ conversion, and a mesoporous Mn3 O4 sub-scaffold for rapid shuttling of redox-active species, whereby the site accessibility is maximized, contrary to conventional transport-limited catalysts. By in situ grafting this interface onto micron-porous carbon felt (Bi1 -sMn3 O4 -CF), a high-performance flow battery is achieved, yielding a record high energy efficiency of 76.72% even at a high current density of 400 mA cm-2 and a peak power density of 1.503 W cm-2 , outdoing the battery with sMn3 O4 -CF (62.60%, 0.978 W cm-2 ) without Bi catalyst. Moreover, this battery renders extraordinary durability of over 1500 cycles, bespeaking a crucial breakthrough toward sustainable redox flow batteries (RFBs).

Functional Alkali Metal-Based Ternary Chalcogenides: Design, Properties, and Opportunities

The search for novel materials has recently brought research attention to alkali metal-based chalcogenides (ABZ) as a new class of semiconducting inorganic materials. Various theoretical and computational studies have highlighted many compositions of this class as ideal functional materials for application in energy conversion and storage devices. This Perspective discusses the expansive compositional landscape of ABZ compositions that inherently gives a wide spectrum of properties with great potential for application. In the present paper, we examine the technique of synthesizing this particular class of materials and explore their potential for compositional engineering in order to manipulate key functional properties. This study presents the notable findings that have been documented thus far in addition to outlining the potential avenues for implementation and the associated challenges they present. By fulfilling the sustainability requirements of being relativity earth-abundant, environmentally benign, and biocompatible, we anticipate a promising future for alkali metal chalcogenides. Through this Perspective, we aim to inspire continued research on this emerging class of materials, thereby enabling forthcoming breakthroughs in the realms of photovoltaics, thermoelectrics, and energy storage.

Constructed electron-dense Mn sites in nitrogen-doped Mn3O4 for efficient catalytic ozonation of pyrazines: Degradation and odor elimination

In this study, N-doped Mn3O4 catalysts (Mn-nN) with electron-dense Mn sites were synthesized and employed in heterogeneous catalytic ozonation (HCO). These catalysts demonstrated excellent performance in pyrazines degradation and odor elimination. The synthesis of Mn-nN was achieved through a facile urea-assisted heat treatment method. Experimental characterization and theoretical analyses revealed that the MnN structures in Mn-nN, played a crucial role in facilitating the formation of electron-dense Mn sites that served as the primary active sites for ozone activation. In particular, Mn-1N exhibited excellent performance in the HCO system, demonstrating the highest 2,5-dimethylpyrazine (2,5-DMP) degradation efficiency. •OH was confirmed as the primary reactive oxygen species involved in the HCO process. The second-order rate constants for 2,5-DMP degradation with O3 and •OH, were determined to be (3.75 ± 0.018) × 10-1 and (6.29 ± 0.844) × 109 M-1 s-1, respectively. Seventeen intermediates were identified through GC-MS analysis during the degradation of 2,5-DMP via HCO process with Mn-1N. The degradation pathways were subsequently proposed by considering these identified intermediates. This study introduces a novel approach to synthesize N-doped Mn3O4 catalysts and demonstrates their efficacy in HCO for the degradation of pyrazines and the elimination of associated odors. The results show that the catalysts are promising for addressing odor-related environmental issues and provide valuable insights about the broader significance of catalytic ozonation processes.

2D heterostructural Mn2O3 quantum dots embedded N-doped carbon nanosheets with strongly stable interface enabling high-performance sodium-ion hybrid capacitors

The ingenious architectural structural engineering is extensively identified as a cogent means for facilitating the electrochemical properties of conversion-type anode materials for sodium-ion storage. Herein, a delicate, scalable and controllable solvent-free strategy is proposed to synthesize ultrafine Mn2O3 quantum dots embedded into N-doped carbon to generate two-dimensional (2D) composites (MNC) with robust interfacial heterostructural interactions for high sodium ion storage and fast reaction kinetics, which averts the use of solvents and environmental pollution, greatly reduces time and production costs. The introduction of metallic Mn species simultaneously achieves the construction of ultrafine Mn2O3 quantum dots and strong interfacial heterostructural COMn bonds between metal species and 2D N-doped carbon matrix. The synergistic effect of the formation of oxide quantum dots, the combination of 2D N-doped carbon and the construction of robust interfacial interactions provides the stable electrode structure, fast reaction kinetics and high electrochemical storage capability of anode materials. Hence, MNC composites in SIBs convey remarkable reversible rate capability. Its superior capacity reaches 215 mAh g-1 for 50 cycles at 0.2 A g-1 and 155 mAh g-1 for 1000 cycles at a high current density of 5 A g-1, which shows good long-term stability. The assembled sodium-ion hybrid capacitors (SIHCs) device delivers outstanding energy density of 138 Wh kg-1 at a power density of 126 W kg-1 and 98% capacity retention after 2000 cycles at 2 A g-1, and tremendous capability for practical applications (69 LEDs can be easily lighted). This work not merely offers guidance for the rational interfacial engineering design of high-capacity Mn-based electrode materials in a feasible and scalable solvent-free tactics for Na+ storage, but also broadens the routes for projecting a better electrode material for other battery systems.

Phase Engineering of 2D Spinel-Type Manganese Oxides

2D magnetic materials have been of interest due to their unique long-range magnetic ordering in the low-dimensional regime and potential applications in spintronics. Currently, most studies are focused on strippable van der Waals magnetic materials with layered structures, which typically suffer from a poor stability and scarce species. Spinel oxides have a good environmental stability and rich magnetic properties. However, the isotropic bonding and close-packed nonlayered crystal structure make their 2D growth challenging, let alone the phase engineering. Herein, a phase-controllable synthesis of 2D single-crystalline spinel-type oxides is reported. Using the van der Waals epitaxy strategy, the thicknesses of the obtained tetragonal and hexagonal manganese oxide (Mn3 O4 ) nanosheets can be tuned down to 7.1 nm and one unit cell (0.7 nm), respectively. The magnetic properties of these two phases are evaluated using vibrating-sample magnetometry and first-principle calculations. Both structures exhibit a Curie temperature of 48 K. Owing to its ultrathin geometry, the Mn3 O4 nanosheet exhibits a superior ultraviolet detection performance with an ultralow noise power density of 0.126 pA Hz-1/2 . This study broadens the range of 2D magnetic semiconductors and highlights their potential applications in future information devices.

Hybrid Sub-1 nm Nanosheets of Co-assembled MnZnCuOx and Polyoxometalate Clusters as Anodes for Li-ion Batteries

Transition metal oxide (TMO) anode materials in lithium-ion batteries (LIBs) usually suffer from serious volume expansion leading to the pulverization of structures, further giving rise to lower specific capacity and worse cycling stability. Herein, by introducing polyoxometalate (POM) clusters into TMOs and precisely controlling the amount of POMs, the MnZnCuOx -phosphomolybdic acid hybrid sub-1 nm nanosheets (MZC-PMA HSNSs) anode is successfully fabricated, where the special electron rich structure of POMs is conducive to accelerating the migration of lithium ions on the anode to obtain higher specific capacity, and the non-covalent interactions between POMs and TMOs make the HSNSs possess excellent structural and chemical stability, thus exhibiting outstanding electrochemical performance in LIBs, achieving a high reversible capacity (1157 mAh g-1 at 100 mA g-1 ) and an admirable long-term cycling stability at low and high current densities.

ZIF-8-Derived Carbon In-Situ Encapsulated Hollow Mn2SiO4 Sub-Microspheres as Anode for Lithium-Ion Batteries with Ultrahigh Capacity and Excellent Rate Performance

Manganese silicate (Mn2SiO4) possesses a more suitable volume expansion (186%) compared to SiOx-based materials and is also characterized by low cost, environmental friendliness, and considerable theoretical capacity. Hollow Mn2SiO4 sub-microspheres encapsulated by a highly continuous network of conductive carbon (MSC) are prepared by the self-templating method and subsequent ZIF-8-derived carbon coating. The as-prepared Mn2SiO4@C hybrid under optimal conditions (MSC-2) can provide a high capacity of 1343 mA h g-1 at 0.2 A g-1 and an excellent rate performance of 434 mA h g-1 at 10 A g-1. Even after 500 cycles, MSC-2 can still maintain a considerable specific capacity of 554 mA h g-1 at a high current density of 5.0 A g-1. Additionally, the full cell assembled with MSC-2 anode and LiFePO4 cathode (MSC-2//LFP) possesses a robust energy density of 218 W h kg-1, excellent power density of 2.5 kW kg-1, and good cycling stability.

Topological Insulator Bi2 Se3 -Assisted Heterostructure for Ultrafast Charging Sodium-Ion Batteries

The development of fast charging materials offers a viable solution for large-scale and sustainable energy storage needs. However, it remains a critical challenge to improve the electrical and ionic conductivity for better performance. Topological insulator (TI), a topological quantum material that has attracted worldwide attention, hosts unusual metallic surface states and consequent high carrier mobility. Nevertheless, its potential in promising high-rate charging capability has not been fully realized and explored. Herein, a novel Bi2 Se3 -ZnSe heterostructure as excellent fast charging material for Na+ storage is reported. Ultrathin Bi2 Se3 nanoplates with rich TI metallic surfaces are introduced as an electronic platform inside the material, which greatly reduces the charge transfer resistance and improves the overall electrical conductivity. Meanwhile, the abundant crystalline interfaces between these two selenides promote Na+ migration and provide additional active sites as well. As expected, the composite delivers the excellent high-rate performance of 360.5 mAh g-1 at 20 A g-1 and maintains its electrochemical stability of 318.4 mAh g-1 after 3000 long cycles, which is the record high for all reported selenide-based anodes. This work is anticipated to provide alternative strategies for further exploration of topological insulators and advanced heterostructures.

Preparation and Evaluation of Co-Doped Fe7S8/C Composites for Lithium Storage

Fe₇S₈ has a high theoretical capacity (663 mAh g^-1) and can be prepared at a low cost, making it advantageous for production. However, Fe₇S₈ has two disadvantages as a lithium-ion battery anode material. The first is that the conductivity of Fe₇S₈ is not good. The second is that when the lithium ion is embedded, the volume expansion of the Fe₇S₈ electrode is serious. That is why Fe₇S₈ has not been used in real life yet. In this paper, Co-Fe₇S₈/C composites were prepared by doping Co into Fe₇S₈ through a one-pot simple hydrothermal method. In situ Co is doped into Fe₇S₈ to produce a more disordered microstructure to improve ion and electron transport performance, thereby reducing the activation barrier of the main material. The Co-Fe₇S₈/C electrode presents a high specific discharge capacity of 1586 mAh g^-1 and a Coulombic efficiency (CE) of 71.34% at an initial cycle at 0.1 A g^-1. After 1500 cycles, the specific discharge capacity remains at 436 mAh g^-1 (5 A g^-1). When the current density returns to 0.1 A g^-1, the capacity almost returns to the initial level, showing excellent rate performance.

Tailored engineering of Fe3O4 and reduced graphene oxide coupled architecture to realize the full potential as electrode materials for lithium-ion batteries

Developing advanced electrode materials with appropriate compositions and exquisite configurations is crucial in fabricating lithium-ion batteries (LIBs) with high energy density and fast charging capability plateau. Herein, a Fe₃O₄@reduced graphene oxide (Fe₃O₄@rGO) coupled architecture was rationally designed and in-situ synthesized. Monodispersed mesoporous Fe₃O₄ nanospheres were homogeneously formed and strongly bound on interconnected macroporous rGO frameworks to form well-defined three-dimensional (3D) hierarchical porous morphologies. This tailored Fe₃O₄@rGO coupled architecture fully exploited the advantages of Fe₃O₄ and rGO to overcome their inherent challenges, including spontaneous aggregating/excessive restacking tendency, sluggish ions diffusion/electrons transportation, and severe volume expansion/structural collapse. Benefitting from their synergistic effects, the optimized Fe₃O₄@rGO composite electrode exhibited an improved electrochemical reactivity, electrical conductivity, electrolyte accessibility, and structural stability. The optimized composite electrode displayed a high specific capacity of 1296.8 mA h g^-1 at 0.1 A g^-1 after 100 cycles, even retaining 555.1 mA h g^-1 at 2 A g^-1 after 2000 cycles. The electrochemical kinetics analysis revealed the predominantly pseudocapacitive behaviors of the Fe₃O₄@rGO heterogeneous interfaces, accounting for the excellent electrode performance. This study proposes a viable strategy for use in engineering hybrid composites with coupled architectures to optimize their potential as high-performance electrode materials for use in LIBs.

A "Pre-Division Metal Clusters" Strategy to Mediate Efficient Dual-Active Sites ORR Catalyst for Ultralong Rechargeable Zn-Air Battery

To conquer the bottleneck of sluggish kinetics in cathodic oxygen reduction reaction (ORR) of metal-air batteries, catalysts with dual-active centers have stood out. Here, a "pre-division metal clusters" strategy is firstly conceived to fabricate a N,S-dual doped honeycomb-like carbon matrix inlaid with CoN₄ sites and wrapped Co₂ P nanoclusters as dual-active centers (Co₂ P/CoN₄ @NSC-500). A crystalline {Co^II ₂ } coordination cluster divided by periphery second organic layers is well-designed to realize delocalized dispersion before calcination. The optimal Co₂ P/CoN₄ @NSC-500 executes excellent 4e^- ORR activity surpassing the benchmark Pt/C. Theoretical calculation results reveal that the CoN₄ sites and Co₂ P nanoclusters can synergistically quicken the formation of *OOH on Co sites. The rechargeable Zn-air battery (ZAB) assembled by Co₂ P/CoN₄ @NSC-500 delivers ultralong cycling stability over 1742 hours (3484 cycles) under 5 mA cm^-2 and can light up a 2.4 V LED bulb for ≈264 hours, evidencing the promising practical application potentials in portable devices.

Dual Strategies of Metal Preintercalation and In Situ Electrochemical Oxidization Operating on MXene for Enhancement of Ion/Electron Transfer and Zinc-Ion Storage Capacity in Aqueous Zinc-Ion Batteries

As an emerging two-dimensional material, MXenes exhibit enormous potentials in the fields of energy storage and conversion, due to their superior conductivity, effective surface chemistry, accordion-like layered structure, and numerous ordered nanochannels. However, interlayer accumulation and chemical sluggishness of structural elements have hampered the demonstration of the superiorities of MXenes. By metal preintercalation and in situ electrochemical oxidization strategies on V₂ CT_x , MXene has enlarged its interplanar spacing and excited the outermost vanadium atoms to achieve frequent transfer and high storage capacity of Zn ions in aqueous zinc-ion batteries (ZIBs). Benefiting from the synergistic effects of these strategies, the resulting VO_x /Mn-V₂ C electrode exhibits the high capacity of 530 mA h g^-1 at 0.1 A g^-1 , together with a remarkable energy density of 415 W h kg^-1 and a power density of 5500 W kg^-1 . Impressively, the electrode delivers excellent cycling stability with Coulombic efficiency of nearly 100% in 2000 cycles at 5 A g^-1 . The satisfactory electrochemical performances bear comparison with those in reported vanadium-based and MXene-based aqueous ZIBs. This work provides a new methodology for safe preparation of outstanding vanadium-based electrodes and extends the applications of MXenes in the energy storage field.

Achieving Record-High Photoelectrochemical Photoresponse Characteristics by Employing Co3O4 Nanoclusters as Hole Charging Layer for Underwater Optical Communication

The physicochemical properties of a semiconductor surface, especially in low-dimensional nanostructures, determine the electrical and optical behavior of the devices. Thereby, the precise control of surface properties is a prerequisite for not only preserving the intrinsic material quality but also manipulating carrier transport behavior for promoting device characteristics. Here, we report a facile approach to suppress the photocorrosion effect while boosting the photoresponse performance of n-GaN nanowires in a constructed photoelectrochemical-type photodetector by employing Co₃O₄ nanoclusters as a hole charging layer. Essentially, the Co₃O₄ nanoclusters not only alleviate nanowires from corrosion by optimizing the oxygen evolution reaction kinetics at the nanowire/electrolyte interface but also facilitate an efficient photogenerated carrier separation, migration, and collection process, leading to a significant ease of photocurrent attenuation (improved by nearly 867% after Co₃O₄ decoration). Strikingly, a record-high responsivity of 217.2 mA W^-1 with an ultrafast response/recovery time of 0.03/0.02 ms can also be achieved, demonstrating one of the best performances among the reported photoelectrochemical-type photodetectors, that ultimately allowed us to build an underwater optical communication system based on the proposed nanowire array for practical applications. This work provides a perspective for the rational design of stable nanostructures for various applications in photo- and biosensing or energy-harvesting nanosystems.

Electron transfer enhancing the Mn(II)/Mn(III) cycle in MnO/CN towards catalytic ozonation of atrazine via a synergistic effect between MnO and CN

In this study, manganese oxide (MnO) dispersed on CN (Mn-nCN) was fabricated as a catalyst in heterogeneous catalytic ozonation (HCO), achieving excellent catalytic performance on refractory organic pollutant degradation via the synergistic effects between MnO and CN. The study demonstrated that the C-N-Mn and C-O-Mn bonds constructed in the catalyst linking MnO and CN created the synergistic effects which could overcome typical problems, such as metal leaching etc. The C-N-Mn and C-O-Mn bonds could promote electron transfer from cation-π reactions to form electron-rich Mn(II) sites and electron-poor CN sites. The electron-rich Mn(II) sites as active sites supplied electrons to ozone which then further evolved into reactive oxygen species (ROS). The electron-poor CN sites captured electrons from the pollutant intermediate radicals to electron-rich Mn(II) sites via cation-π reactions with the help of C-N-Mn and C-O-Mn bonds, which promote the redox reactions of Mn. The surface hydroxyl groups also participated in ozone decomposition and ROS production. Additionally, ^•OH was the dominant ROS of the Mn-nCN HCO processes. This study presents the excellent HCO performance of Mn-nCN, as well as provides views on the electron transfer route between the catalyst, pollutant and ozone, which is crucial for the design of the catalyst.

MOF-derived nitrogen-doped porous carbon nanofibers with interconnected channels for high-stability Li+/Na+ battery anodes

Heteroatom-doped porous carbon materials have been widely used as anode materials for Li-ion and Na-ion batteries, however, improving the specific capacity and long-term cycling stability of ion batteries remains a major challenge. Here, we report a facile based metal-organic framework (MOFs) strategy to synthesize nitrogen-doped porous carbon nanofibers (NCNFs) with a large number of interconnected channels that can increase the contact area between the material and the electrolyte, shorten the diffusion distance between Li⁺/Na⁺ and the electrolyte, and relieve the volume expansion of the electrode material during cycling; the doping of nitrogen atoms can improve the conductivity and increase the active sites of the carbon material, can also affect the microstructure and electron distribution of the electrode material, thereby improving the electrochemical performance of the material. As expected, the obtained NCNFs-800 exhibited excellent electrochemical performance with high reversible capacity (for Li⁺ battery anodes: 1237 mA h g^-1 at 100 mA g^-1 after 200 cycles, for Na⁺ battery anodes: 323 mA h g^-1 at 100 mA g^-1 after 150 cycles) and long-term cycling stability (for Li⁺ battery anodes: 635 mA h g^-1 at 2 A g^-1 after 5000 cycles, for Na⁺ battery anodes: 194 mA h g^-1 at 2 A g^-1 after 5000 cycles).

MgAl Saponite as a Transition-Metal-Free Anode Material for Lithium-Ion Batteries

Transition-metal compounds (oxides, sulfides, hydroxides, etc.) as lithium-ion battery (LIB) anodes usually show extraordinary capacity larger than the theoretical value due to the transformation of LiOH into Li₂O/LiH. However, there has rarely been a report relaying the transformation of LiOH into Li₂O/LiH as the main reaction for LIBs, due to the strong alkalinity of LiOH leading to battery deterioration. In this work, layered silicate MgAl saponite (MA-SAP) is applied as a -OH donor to generate LiOH as the anode material of LIBs for the first time. The MA-SAP maintains a layered structure during the (dis)charging process and has zero-strain characteristic on the (001) crystal plane. In the discharging process, Mg, Al, and Si in the saponite sheets become electron-rich, while the active hydroxyl groups escape from the sheets and combine with lithium ions to form LiOH in the "caves" on sheets, and the LiOH continues to decompose into Li₂O and LiH. Consequently, the MA-SAP delivers a maximum capacity of 536 mA h·g^-1 at 200 mA·g^-1 with a good high-current discharging ability of 155 mA h·g^-1 after 1000 cycles under 1 A·g^-1. Considering its extremely low cost and completely nontoxic characteristics, MA-SAP has great application prospects in energy storage. In addition, this work has an enlightening effect on the development of new anodes based on extraordinary mechanisms.

Accommodation of Two-Dimensional SiOx in a Point-to-Plane Conductive Network Composed of Graphene and Nitrogen-Doped Carbon for Robust Lithium Storage

Silicon oxides (SiO_x) are one of the most promising anode materials for next-generation lithium-ion batteries owing to their abundant reserve and low lost and high reversible capacity. However, the practical application of SiO_x is still hindered by their intrinsically low conductivity and huge volume change. In this regard, we design a novel anode material in which sheet-like SiO_x nanosheets are encapsulated in a unique point-to-plane conductive network composed of graphene flakes and nitrogen-doped carbon spheres. This unique composite structure demonstrates high specific capacity (867.7 mAh g^-1 at 0.1 A g^-1), superior rate performance, and stable cycle life. The electrode delivers a superior reversible discharge capacity of 595.8 mAh g^-1 after 200 cycles at 1.0 A g^-1 and 287.5 mAh g^-1 after 500 cycles at 5.0 A g^-1. This work may shed light on the rational design of SiO_x-based anode materials for next-generation high-performance lithium-ion batteries.

A MOF-derived hollow Co3O4/NiCo2O4 nanohybrid: a novel anode for aqueous lithium ion batteries with high energy density and a wide electrochemical window

Aqueous lithium-ion batteries (LIBs) have attracted increasing attention because of their higher safety and nontoxicity compared to traditional LIBs. However, crucial shortcomings impede their practical applications. A narrow electrochemical window restricts the capacity of aqueous LIBs so the ultrahigh concentration electrolyte lithium bistrifluoromethosulfonimide (LiTFSI) is introduced to widen the electrochemical window in this work. With the addition of LiTFSI, the electrochemical window of the created aqueous LIBs is improved to 2 V. Moreover, the material design promotes the high density of aqueous LIBs, in which hollow Co₃O₄ nanocrystals obtained by the metal organic framework (MOF) template are connected with NiCo₂O₄ nanorods to form three-dimensional nanohybrids. The formed Co₃O₄/NiCo₂O₄ (CN) materials can provide NiCo₂O₄ channels for electron transfer between hollow Co₃O₄ which can offer more lithium-ions insertion. These effects work together synergistically to achieve aqueous LIBs with a wide electrochemical window and high energy density (93.07 W h kg^-1 at 0.5 C). CN-6/LiMn₂O₄-based aqueous LIBs with LiTFSI as the electrolyte take into account both environmental friendliness and sustainable energy storage and exhibit great potential for producing novel clean energy storage devices from the concepts of material design and synthesis.

Hollow Porous N and Co Dual-Doped Silicon@Carbon Nanocube Derived by ZnCo-Bimetallic Metal-Organic Framework toward Advanced Lithium-Ion Battery Anodes

Silicon (Si) has been recognized as a promising alternative to graphite anode materials for advanced lithium-ion batteries (LIBs) owing to its superior theoretical capacity and low discharge voltage. However, Si-based anodes undergo structural pulverization during cycling due to the large volume expansion (ca. 300-400%) and continuous formation of an unstable solid electrolyte interphase (SEI), resulting in fast capacity fading. To address this challenge, a series of different amounts of silicon nanoparticles (Si NPs)-encapsulated hollow porous N-doped/Co-incorporated carbon nanocubes (denoted as p-CoNC@SiX, where X = 50, 80, and 100) as anode materials for LIBs are reported in this paper. These hollow nanocubic materials were derived by facile annealing of different contents of Si NPs-encapsulated Zn/Co-bimetallic zeolitic imidazolate frameworks (ZIF@Si) as self-sacrificial templates. Owing to the advantages of well-defined hollow framework clusters and highly conductive hollow carbon frameworks, the hollow porous p-CoNC@SiX significantly improved the electronic conductivity and Li⁺ diffusion coefficient by an order of magnitude higher than that of Si NPs. The as-prepared p-CoNC@Si80 with 80 wt % Si NPs delivered a continuously increasing specific capacity of 1008 mAh g^-1 at 500 mA g^-1 over 500 cycles, excellent reversible capacity (∼1361 mAh g^-1 at 0.1 A g^-1), and superior rate capability (∼603 mAh g^-1 at 3 A g^-1) along with an unprecedented long-life cyclic stability of ∼1218 mAh g^-1 at 1 A g^-1 over 1000 cycles caused by low volume expansion (9.92%) and suppressed SEI side reactions. These findings provide new insights into the development of highly reversible Si-based anode materials for advanced LIBs.

CdS Nanocubes Adorned by Graphitic C3N4 Nanoparticles for Hydrogenating Nitroaromatics: A Route of Visible-Light-Induced Heterogeneous Hollow Structural Photocatalysis

Modulating the transport route of photogenerated carriers on hollow cadmium sulfide without changing its intrinsic structure remains fascinating and challenging. In this work, a series of well-defined heterogeneous hollow structural materials consisting of CdS hollow nanocubes (CdS NCs) and graphitic C3N4 nanoparticles (CN NPs) were strategically designed and fabricated according to an electrostatic interaction approach. It was found that such CN NPs/CdS NCs still retained the hollow structure after CN NP adorning and demonstrated versatile and remarkably boosted photoreduction performance. Specifically, under visible light irradiation (λ ≥ 420 nm), the hydrogenation ratio over 2CN NPs/CdS NCs (the mass ratio of CN NPs to CdS NCs is controlled to be 2%) toward nitrobenzene, p-nitroaniline, p-nitrotoluene, p-nitrophenol, and p-nitrochlorobenzene can be increased to 100%, 99.9%, 83.2%, 93.6%, and 98.2%, respectively. In addition, based on the results of photoelectrochemical performances, the 2CN NPs/CdS NCs reach a 0.46% applied bias photo-to-current efficiency, indicating that the combination with CN NPs can indeed improve the migration and motion behavior of photogenerated carriers, besides ameliorating the photocorrosion and prolonging the lifetime of CdS NCs.

Manipulation of the MoO2/MoSe2 Heterointerface Boosting High Rate and Durability for Sodium/Potassium Storage

The main challenge for sodium/potassium ion storage is to find the suitable host materials to accommodate the larger-sized Na⁺/K⁺ and conquer the sluggish chemical kinetics. Herein, by selenation of polyoxometalate in electrospinning fiber, a novel MoO₂/MoSe₂ heterostructure embedded in one-dimensional (1D) N,P-doped carbon nanofiber (MoO₂/MoSe₂@NPC) is rationally constructed to show distinct enhancement of rate performance and cycle life for sodium ion batteries (SIBs) and potassium ion batteries (PIBs). The 1D skeleton of MoO₂/MoSe₂@NPC decreases the diffusion pathway of Na⁺/K⁺, and the doping of N/P heteroatoms in carbon fiber creates abundant active sites and provides good reachability for Na⁺/K⁺ transportation. MoSe₂ nanosheets grow in the bulk phase of MoO₂ via in situ local phase transformation to achieve effective and firm heterointerfaces. Especially, the exposure extent of heterointerfaces can be controlled by treatment temperature during the preparation process, and the optimized heterointerfaces result in an ideal synergic effect between MoO₂ and MoSe₂. DFT calculations confirm that the internal electric field in the heterogeneous interface guides the electron transfer from MoO₂ to MoSe₂, combined with strong adsorption capacity toward sodium/potassium, facilitating ion/electron transfer kinetics. It is confirmed that the MoO₂/MoSe₂@NPC anode for SIBs delivers 382 mA h g^-1 under 0.1 A g^-1 upon 200 cycles; meanwhile, a reversible capacity of 266 mA h g^-1 is maintained even under 2 A g^-1 after 2000 cycles. For PIBs, it can reach up to 216 mA h g^-1 in the 200th cycle and still retain 125 mA h g^-1 after 2000 cycles under 1 A g^-1. This study opens up a new interface manipulation strategy for the design of anode materials to boost fast Na⁺/K⁺ storage kinetics.

Tailoring Nitrogen Species in Disk-Like Carbon Anode Towards Superior Potassium Ion Storage

Carbon materials, as promising anode candidates for K⁺ storage due to their low cost, abundant sources, and high physicochemical stability, however, encounter limited specific capacity and unfavorable cycling stability that seriously hinder their practical applications. Herein, a feasible strategy to tailor and stabilize the nitrogen species in unique P/N co-doped disk-like carbon through the Sn incorporation (P/N_Sn -CD) is presented, which can largely enhance the specific capacity and cycling capability for K⁺ storage. Specifically, it delivers a high specific capacity of 439.3 mAh g^-1 at 0.1 A g^-1 and ultra-stable cycling capability with a capacity retention of 93.5% at 5000 mA g^-1 over 5000 cycles for K⁺ storage. The underlying mechanism for the superior K⁺ storage performance is investigated by systematical experimental data combined with theoretical simulation results, which can be derived from the increased edge-nitrogen species, improved content and stability of P/N heteroatoms, and enhanced ionic/electronic kinetics. After coupling P/N_Sn -CD anode with activated carbon cathode, the KIHCs can deliver a high energy density of 171.7 Wh kg^-1 at 106.8 W kg^-1 , a superior power density (14027.0 W kg^-1 with 31.2 Wh kg^-1 retained), and ultra-stable lifespan (89.7% retention after 30 K cycles with cycled at 2 A g^-1 ).

Recycling and applications of ammonium polyphosphate/polycarbonate/acrylonitrile butadiene styrene by laser-scribing technologies for supercapacitor electrode materials

Fabricating a simple and valid high-property graphene-based supercapacitor employing engineered plastic waste as the original material has attracted tremendous interest. Herein we report an extendable method for producing nitrogen and phosphorus dual-doped porous three-dimensional (3D) graphene materials from the blends of ammonium polyphosphate (APP) and polycarbonate (PC)/acrylonitrile ((A), butadiene (B), and styrene (S)) (ABS) using a simple laser direct-writing technique. In APP/PC/ABS blends, APP/PC/ABS, a waste by-product generated in car interiors and exterior decoration and electronic device shells and other fields, served as a sufficient and economic carbon source, while APP was employed as a nitrogen and phosphorus source as well as flame retardant. APP/PC/ABS blends could be transformed into nitrogen and phosphorus dual-doped laser-induced graphene (NPLIG) via scribing under a CO₂ laser in air conditions. In addition, a supercapacitor was fabricated applying NPLIG as the electrode material, and KOH solution as the electrolyte. The as-fabricated NPLIG supercapacitor exhibited excellent electrochemical behaviours, namely, a high specific areal capacitance (239 F g⁻¹) at a current density of 0.05 A g⁻¹, which outperformed many LIG-based and GO-based supercapacitors. The concept of designing supercapacitors that can be obtained with a facile laser-scribing technology can stimulate both the building of supercapacitors and preparation of graphene, and the sustainable utilization of engineering plastics.

Fabricating a simple and valid high-property graphene-based supercapacitor employing engineered plastic waste as the original material has attracted tremendous interest.

Rational Construction of Yolk-Shell Bimetal-Modified Quinonyl-Rich Covalent Organic Polymers with Ultralong Lithium-Storage Mechanism

Covalent organic polymers are attracting more and more attention for energy storage devices due to their lightweight, molecular viable design, stable structure, and environmental benignity. However, low charge-carrier mobility of pristine covalent organic materials is the main drawback for their application in lithium-ion batteries. Herein, a yolk-shell bimetal-modified quinonyl-rich covalent organic material, Co@2AQ-MnO₂, has been designed and synthesized by in situ loading of petal-like nanosized MnO₂ and coordinating with Co centers, with the aim to improve the charge conductivity of the covalent organic polymer and activate its Li-storage sites. As investigated by in situ FT-IR, ex situ XPS, and electrochemical probing, the quinonyl-rich structure provides abundant redox sites (carbonyl groups and π electrons from the benzene ring) for lithium reaction, and the introduction of two types of metallic species promotes the charge transfer and facilitates more efficient usage of active energy-storage sites in Co@2AQ-MnO₂. Thus, the Co@2AQ-MnO₂ electrode exhibits good cycling performance with large reversible capacity and excellent rate performance (1534.4 mA h g^-1 after 200 cycles at 100 mA g^-1 and 596.0 mA h g^-1 after 1000 cycles at 1000 mA g^-1).

Interpenetrated N-rich MOF derived vesicular N-doped carbon for high performance lithium ion battery

High-performance lithium ion batteries (LIBs) juggling high reversible capacity, excellent rate capability and ultralong cycle stability are urgently needed for all electronic devices. Here we report employing a vesicle-like porous N-doped carbon material (abbr. N/C-900) as a highly active anode for LIBs to balance high capacity, high rate and long life. The N/C-900 material was fabricated by pyrolysis of a designed crystal MOF LCU-104, which exhibits a graceful two-fold interpenetrating structural feature of N-rich nanocages {Zn₆(dttz)₄} linked through an N-donor ligand bpp (H₃dttz = 4,5-di(1H-tetrazol-5-yl)-2H-1,2,3-triazole, bpp = 1,3-bis(4-pyridyl)propane). The features of LCU-104 combine high N content (35.1%), interpenetration, and explosive characteristics, which endow the derived N/C material with optimized N-doping for tuning its chemical and electronic structure, a suitably thicker wall to enhance its stability, and a vesicle-like structure to improve its porosity. As an anode material for LIBs, N/C-900 delivers a highly reversible capacity of ca. 734 mA h g^-1 at a large current density of 1 A g^-1 until the 2000th cycle, revealing its ultralong cycle stability and excellent rate capability. The unique structure and preferential interaction between abundant pyridinic N active sites and Li atoms are responsible for the improved excellent lithium storage capacity and durability performances of the anode according to analysis of the results of computational modeling.

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.

Self-induced matrix with Li-ion storage activity in ultrathin CuMnO2 nanosheets electrode

Conversion anode materials such as Mn₃O₄ draw much attention due to their considerable theoretical capacity for lithium-ion batteries (LIBs). However, poor conductivity, slow solid-state Li-ion diffusion, and huge volume expansion of the active materials during charge/discharge lead to unsatisfied electrochemical performance. Despite several strategies like nanocrystallization, fabricating hierarchical nanostructures, and introducing a matrix are valid to address these crucial issues, the achieved electrochemical performance still needs to be further enhanced. What is worse, the matrix with less or no Li-ion storage activity may lower the achieved capacity of the electrodes. Herein, ultra-thin CuMnO₂ nanosheets with the thickness of 5-8 nm were evaluated for LIBs. The ultra-thin sheet-like nanostructure offers sufficient contact areas with electrolyte and shortens the Li-ion diffusion distance. Moreover, the in-situ generated Mn and Cu along with their oxides could play the role of matrix and conductive agent in turn at different stages, relieving the stress brought by volume expansion. Therefore, the as-prepared ultra-thin CuMnO₂ nanosheets electrode displays a remarkable reversible capacity, long cycling stability, and outstanding rate capability (a reversible capacity of 1160.5 mAh g^-1 at 0.1A g^-1 was retained after 100 cycles with a capacity retention of 95.1 %, and 717.8 mAh g^-1 at 2.0 A g^-1 after 400 cycles).

Rational design of 3D net-like carbon based Mn3O4 anode materials with enhanced lithium storage performance

A three-dimensional net-like Mn3O4/carbon paper composite was realized, which delivers a remarkably enhanced rate performance and excellent cycling stability for lithium-ion storage.

Construction of a ternary MoO2/Ni/C hybrid towards lithium-ion batteries as a high-performance electrode

The high lithium storage performance of 3D flower-like MoO2/Ni/C through a temperature annealing strategy is benefitted from the high capacitive contribution, high electrical conductivity, and good structural stability.

Fabrication of MnSe/SnSe@C heterostructures for high-performance Li/Na storage

Novel heterostructured MnSe/SnSe@C nanoboxes display excellent electrochemical performance.

Synthesis of MnO-Sn cubes embedding in nitrogen-doped carbon nanofibers with high lithium-ion storage performance

In this paper, a carbon nanofiber (CNF) hybrid nanomaterial composed of MnO-Sn cubes embedding in nitrogen-doped CNF (MnO-Sn@CNF) is synthesized through electrospinning and post-thermal reduction processes. It exhibits good electrochemical lithium-ion storage performance as the anode, such as high reversible capacity, outstanding cycle performance (754 mAh g^-1at 1 A g^-1after 1000 cycles), and good rate capability (447 mAh g^-1at 5 A g^-1). The excellent electrochemical properties are derived from a unique nanostructure design. MnO-Sn@CNF has a three-dimensional conductive network with a stable core-shell structure, which improves the electrical conductivity and mechanical stability of the materials. In addition, the mesopores on the surface of carbon fibers can shorten the diffusion distance of lithium ions and promote the combination of active sites of the material with lithium ions. The internal MnO and Sn form a heterostructure, which enhances the stability of the physical structure of the electrode material. This material design method provides a reference strategy for the development of high-performance lithium-ion batteries anode.

Transferrin guided quasi-nanocuboid as tetra-enzymic mimics and biosensing applications

Given the promising prospect of nanozymes system with multi-enzyme mimetic activities, it is also a challenge for designing a controllable nanostructure as multi-enzymes mimics by protein-guided strategy. Here, transferrin (Trf)-directed manganese oxide with 3D nanomorphology was developed. Trf-Mn₃O₄ quasi-nanocuboids (NCs) was obtained by improved conditions for biomineralization, which employing Trf as biotemplate and Mn²⁺ as metal source in alkaline solution. Fortunately, not only was the controllable structure discovered, but Trf-Mn₃O₄ NCs also showed tetra-enzyme mimic activities involving peroxidase-, ascorbic acid oxidase-, catalase- and superoxide dismutase-mimic activities. Further, the catalytic properties and steady-state kinetic of Trf-Mn₃O₄ NCs was explored, systematically. Moreover, we develop simple colorimetric sensor based on the peroxidase-mimic activity of Trf-Mn₃O₄ NCs for the detection of gallic acid (GA) with the linear range within 0.1-40 μΜ, and the limit of detection was 41.2 nM (S/N = 3). Besides, a novel fluorimetric sensor for the detection of AA based on the ascorbic acid oxidase-mimic activity was proposed with the linear range of 0.5 μM-10 μM (R² = 0.9906) and 10 μM-5 mM (R² = 0.9927), and LOD of 0.24 μM (S/N = 3) was obtained. Both the proposed sensors showed outstanding detection performance, accuracy and repeatability, which realized the detection of GA and AA in real sample, respectively. The as-synthesized tetra-enzymic mimics not only enriched the species of nanozymes, particularly for the nanozymes with multi-enzyme mimic activities, the proposed sensors showed promising potential applications for biosensor in complex samples.

MOF-derivated MnO@C nanocomposite with bidirectional electrocatalytic ability as signal amplification for dual-signal electrochemical sensing of cancer biomarker

Dual-signal strategy has great potential in improving the accuracy and sensitivity of cancer biomarker determination. However, most sensors based on nanomaterials as signal amplification usually output single detectable signal. It is still a challenge to achieve dual-signal sensing of biomarkers with nanomaterials as signal amplification. Herein, MnO@C nanocomposite was prepared with Mn-MOF-74 as precursor by pyrolysis. It possesses bidirectional electrocatalytic ability toward both oxidation and reduction of H₂O₂ for its fully exposed crystal facets. After loading AuNPs, MnO@C@AuNPs can connect aptamer (Apt) via Au-S and then as a signal amplification for the construction of sandwich-type aptasensor for dual-signal electrochemical sensing of cancer biomarker. Thus, taking mucin 1 (MUC1) as a model system. The aptasensor has the parallel output of differential pulse voltammetry (DPV) and chronoamperometry responses based on oxidation and reduction of H₂O₂, respectively, which implemented sensitive and accurate measurements to avoid false results. The linear response ranges of 0.001 nM-100 nM (detection limit of 0.31 pM) for DPV technique and 0.001 nM-10 nM (detection limit of 0.25 pM) for chronoamperometry technique were obtained. It opens up a new way to design elegant dual-signal aptasensors with potential applications in early disease diagnosis.

Polyoxometalate@MOF derived porous carbon-supported MoO2/MoS2 octahedra boosting high-rate lithium storage

Structural stability and rapid charge-discharge capability of electrode materials are required for high performance lithium-ion batteries (LIBs). The materials derived from polyoxometalates (POMs) show special advantages in inhibiting capacity attenuation, and good dispersion or combination of POMs with metal-organic frameworks (MOFs) is an important method to obtain high activity anode composites for LIBs. In this study, a uniform MoO₂/MoS₂ heterostructure with surface supported carbon (C-MoO₂/MoS₂) was successfully fabricated from a [Cu₂(BTC)_4/3(H₂O)₂]₆[H₃PMo₁₂O₄₀] precursor, which showed not only the designed octahedral morphology but also fast charge transfer, long working life, and high rate performance. Superior reversible lithium storage capacity of 1047 mA h g^-1 after 300 cycles was obtained at 1 A g^-1. Even after 700 cycles at 5 A g^-1, the discharge specific capacity of 646 mA h g^-1 was maintained, and rate capability of 610 mA h g^-1 could be achieved at 10 A g^-1. The high capacitive contribution could be explained by the relatively large specific surface area of porous C-MoO₂/MoS₂, which was mainly caused by the supported carbon network and MoS₂ nanosheets, resulting in fast lithiation/delithiation processes.

Synthesis and Characterization of Nanocrystalline Ba-doped Mn3O4 Hausmannite Thin Films for Optoelectronic Applications

In the present work, nanocrystalline hausmannite Mn3O4:Ba thin films have been deposited on glass substrates by chemical spray pyrolysis (CSP). Then, we investigated the impact of Ba doping concentrations on the structural, morphological and optical properties. The structural characteristics were investigated by X-ray diffraction technique and clearly show the films have a spinel Mn3O4 polycrystalline structure, the degree of crystallinity was improved by increasing Ba concentrations in Mn3O4 matrix with crystallite size range of 15–33[Formula: see text]nm. The lattice parameters, the unit cell volume and the (Mn-O) bond length of tetrahedral and octahedral sites, were varied by increasing Ba concentrations. SEM micrographs show that the films are homogeneous with nanoparticles dispersed on the surface with sizes range 30–132[Formula: see text]nm. The optical properties were estimated by UV-Vis-NIR spectrophotometer and exhibited that the optical transmittance and band gap were improved by increasing Ba doping concentration. Empirical equations were suggested to estimate some correlated variables with excellent agreement with the experimental data. The optimum condition was recorded in films doped with 3% of Ba where a better crystallinity, a preferable surface morphology and outstanding optical properties have been achieved.

Epitaxially Grown Heterostructured SrMn3 O6-x -SrMnO3 with High-Valence Mn3+/4+ for Improved Oxygen Reduction Catalysis

Heterostructured catalysts show outstanding performance in electrochemical reactions owing to their beneficial interfacial properties. However, the rational design of heterostructured catalysts with the desired interfacial properties and charge-transfer characteristics is challenging. Herein, we developed a SrMn₃ O_6-x -SrMnO₃ (SMO_x -SMO) heterostructure through epitaxial growth, which demonstrated excellent electrocatalyst performance for the oxygen reduction reaction (ORR). The formation of high-valence Mn^3+/4+ is beneficial for promoting a positive shift in the position of the d-band center, thereby optimizing the adsorption and desorption of ORR intermediates on the heterojunction surface and resulting in improved catalytic activity. When SMO_x -SMO was applied as an air-electrode catalyst in a rechargeable zinc-air battery, a high output voltage and power density was achieved, with performance comparable to a battery prepared with Pt/C-IrO₂ air-electrode catalysts, albeit with much better cycling stability.

Co0.85Se particles encapsulated in the inner wall of nitrogen-doped carbon matrix nanotubes with rational interfacial bonds for high-performance lithium-ion batteries

Cobalt selenides based on the conversion reaction have been widely applied in lithium-ion batteries (LIBs) due to their high conductivity and high specific capacity. However, effectively suppressing the fast capacity fade caused by the irreversible Se/Co dissolution and serious volume change during the cycling process is still a challenge. Herein, a facile and efficient self-generated sacrificial template method is used to prepare Co_0.85Se nanoparticles encapsulated in the inner wall of N-doped carbon matrix nanotubes (Co_0.85Se@NCMT). In this strategy, the formation of stable Co-N/C and Se-C as well as enhancing the mechanical strength between active materials and N-doped carbon matrix nanotubes can critically affect the performance through suppressing the dissolution of Se/Co, decreasing energy band, promoting the shuttling of the ions/e^- moving and mitigating the volume expansion during the charge-discharge process, which play a key role in improving the structure stability and electrochemical performance. Besides, Co_0.85Se nanoparticles encapsulated in the robust carbon matrix inner wall can ensure good electron transfer and prevent the aggregation of nanoparticles, leading to superior electrochemical reversibility. Finally, carbon matrix nanotubes can provide sufficient space to effectively accommodate the volume changes of encapsulated Co_0.85Se nanoparticles, thereby improving the cyclic stability. Based on the above advantages, as expected, the electrochemical investigations exhibited that the Co_0.85Se@NCMT anode performs a stable reversible capacity of 462.9 mA h g^-1 at a large current density of 5 A g^-1 and a remarkable capacity retention of 99.5% after 800 cycles, suggesting its promising potential for the anode of LIBs.

Copper niobate nanowires boosted by a N, S co-doped carbon coating for superior lithium storage

With the development of electric vehicles, more and more attention has been paid to the kinetic performance of batteries, which is related to rapid charge/discharge and safety issues. To improve this aspect, Cu₂Nb₃₄O₈₇ nanowires covered by nitrogen and sulfur co-doped carbon (Cu₂Nb₃₄O₈₇/NSC nanowires) are prepared by electrospinning combined with surface coating. As-prepared Cu₂Nb₃₄O₈₇/NSC nanowires present a high ion diffusion coefficient and electronic conductivity, showing good a kinetic performance. Specifically, they deliver a splendid capacity of 311.2 mA h g^-1 at 1 C and a superior cycling stability with a capacity fading of 0.031% per cycle upon 1000 cycles. At the same time, the electrochemical and structural reversibility is fully discussed and demonstrated by ex situ XRD, ex situ SEM and ex situ XPS based on the redox couples of Cu²⁺/Cu⁺, Nb⁵⁺/Nb⁴⁺, and Nb⁴⁺/Nb³⁺. Contributing to peculiar physico-chemical properties, Cu₂Nb₃₄O₈₇/NSC nanowires are expected to be a candidate material for the anode in lithium-ion batteries.