Efficient Laser‐Induced Construction of Oxygen‐Vacancy Abundant Nano‐ZnCo2O4/Porous Reduced Graphene Oxide Hybrids toward Exceptional Capacitive Lithium Storage

Recently, binary ZnCo₂O₄ has drawn enormous attention for lithium‐ion batteries (LIBs) as attractive anode owing to its large theoretical capacity and good environmental benignity. However, the modest electrical conductivity and serious volumetric effect/particle agglomeration over cycling hinder its extensive applications. To address the concerns, herein, a rapid laser‐irradiation methodology is firstly devised toward efficient synthesis of oxygen‐vacancy abundant nano‐ZnCo₂O₄/porous reduced graphene oxide (rGO) hybrids as anodes for LIBs. The synergistic contributions from nano‐dimensional ZnCo₂O₄ with rich oxygen vacancies and flexible rGO guarantee abundant active sites, fast electron/ion transport, and robust structural stability, and inhibit the agglomeration of nanoscale ZnCo₂O₄, favoring for superb electrochemical lithium‐storage performance. More encouragingly, the optimal L‐ZCO@rGO‐30 anode exhibits a large reversible capacity of ≈1053 mAh g^?1 at 0.05 A g^?1, excellent cycling stability (≈746 mAh g^?1 at 1.0 A g^?1 after 250 cycles), and preeminent rate capability (≈686 mAh g^?1 at 3.2 A g^?1). Further kinetic analysis corroborates that the capacitive‐controlled process dominates the involved electrochemical reactions of hybrid anodes. More significantly, this rational design holds the promise of being extended for smart fabrication of other oxygen‐vacancy abundant metal oxide/porous rGO hybrids toward advanced LIBs and beyond.     

NiCo2O4/氧化石墨烯复合材料制备与电化学性能研究

为了研究NiCo₂O₄/氧化石墨烯(NiCo₂O₄/GO)复合材料的电化学性能,本文通过先水热合成前驱体再煅烧的方法制备了一系列NiCo₂O₄/GO复合材料.利用X射线衍射(XRD)、扫描电子显微镜(SEM)和电化学方法对其进行物理表征,其中以GO质量浓度为1 mg/mL悬浊液制备出的NiCo₂O₄ /GO-3复合材料呈类海胆状结构.在1 M KOH水溶液中使用循环伏安法、恒电流充/放电法和交流阻抗法研究了NiCo₂O₄/GO复合材料电化学性能.研究表明,与纯NiCo₂O₄相比,制备的NiCo₂O₄ /GO复合材料的比容量和赝电容性能均有明显提高,这主要是由于NiCo₂O₄ /GO复合材料中NiCo₂O₄与GO纳米片的相互作用形成的高孔隙率复合结构;NiCo₂O₄ /GO-3复合材料在电流密度为0.5~3.0 A/g时,比电容超过650 F/g,具有良好的倍率性能和高比容量.采用本文方法合成的NiCo₂O₄/GO复合材料,既提高了其倍率性能又保证了高比容量,是一种良好的超级电容器电极材料.     

Nanoscale Borate Coating Network Stabilized Iron Oxide Anode for High-Energy-Density Bipolar Lithium-Ion Batteries

High-capacity metal oxides based on non-toxic earth-abundant elements offer unique opportunities as advanced anodes for lithium-ion batteries (LIBs). But they often suffer from large volumetric expansion, particle pulverization, extensive side reactions, and fast degradations during cycling. Here, an easy synthesis method is reported to construct amorphous borate coating network, which stabilizes conversion-type iron oxide anode for the high-energy-density semi-solid-state bipolar LIBs. The nano-borate coated iron oxide anode has high tap density (1.6 g cm⁻³), high capacity (710 mAh g⁻¹ between 0.5 – 3.0 V, vs Li/Li⁺), good rate performance (200 mAh g⁻¹ at 50 C), and excellent cycling stability (≈100% capacity resention over 1,000 cycles at 5 A g⁻¹). When paired with high-voltage cathode LiCoO₂, it enables Cu current collector-free pouch-type classic and bipolar full cells with high voltage (7.6 V with two stack layers), achieving high energy density (≈350 Wh kg⁻¹), outstanding power density (≈6,700 W kg⁻¹), and extended cycle life (75% capacity retention after 2,000 cycles at 2 C), superior to the state-of-the-art high-power LIBs using Li₄Ti₅O₁₂ anode. The design and methodology of the nanoscale polyanion-like coating can be applied to other metal oxides electrode materials, as well as other electrochemical materials and devices.     

A preliminary investigation of the electrochemical performance of α-Fe2O3 and Fe3O4 cathodes in high-temperature cells

The electrochemical behaviour of α-Fe₂O₃ and Fe₃O₄ cathodes has been investigated in cells containing lithium - aluminium anodes and a molten LiCl/KCl electrolyte. Cells were cycled continuously at a current density of 7mA/cm² and were found to operate reversibly at 420°C. Discharge characteristics for both α-Fe₂O₃ and Fe₃O₄ cathodes were similar. Discharge plateaus at 0.8 – 1.0 V were observed which accounted for more than 70% of the total capacity. Maximum capacities of up to 700 mA-h/g were recorded. Cell performance deteriorated slowly with time, probably on account of slow dispersion of Li₂O into the electrolyte. One α-Fe₂O₃ cathode was subjected to 116 cycles over 335 days during which the capacity was reduced from 695 mA-h/g to 460 mA-h/g. X-ray diffraction analyses of α-Fe₂O₃ cathodes indicate that during the electrochemical reduction process, the corundum structure transforms irreversibly to the spinel structure of Fe₃O₄ before being completely reduced to α-Fe. During the charging process it appears that γ-Fe₂O₃ is generated by electrochemical oxidation of the Fe₃O₄ intermediate.     

Ionic Liquid‐Directed Nanoporous TiNb2O7 Anodes with Superior Performance for Fast‐Rechargeable Lithium‐Ion Batteries

Nanoporous TiNb₂O₇ (NPTNO) material is synthesized by a sol–gel method with an ionic liquid (IL) as the nanoporous structure directing template. NPTNO exhibits a high reversible capacity of 210 mAh g^–1 even at the charging rate of 50 C and an excellent cyclability of half‐cell capacity retention of 74% for 1000 cycles at 5 C and LiNi_0.5Mn_1.5O₄‐coupled full‐cell capacity retentions of 81% and 87% for 1000 cycles at 1 C and 2 C, respectively. The studies of the 1000 cycled NPTNO electrode illustrate that the IL‐directed mesoporous structure can enhance the cyclability of NPTNO cells due to the alleviation of repetitive mechanical stress and volume fluctuation induced by the repetitive Li⁺ insertion‐extraction processes. The measured Li⁺ diffusion coefficients from the galvanostatic intermittent titration technique suggest that the IL‐templating strategy indeed ensures the fast rechargeability of NPTNO cells based on the fast Li⁺ diffusion kinetics. Benefitting from the nanoporous structure, NPTNO with unhindered Li⁺ diffusion pathways achieves a superior rate capability in the titanium‐based oxide materials and the best full‐cell cyclability in the TNO materials. Therefore, the templating potential of IL is demonstrated, and the superb electrochemical performance establishes the IL‐directed NPTNO as a promising anode candidate for fast‐rechargeable LIBs.     

Oxygen‐Vacancy and Surface Modulation of Ultrathin Nickel Cobaltite Nanosheets as a High‐Energy Cathode for Advanced Zn‐Ion Batteries

The development of high‐capacity, Earth‐abundant, and stable cathode materials for robust aqueous Zn‐ion batteries is an ongoing challenge. Herein, ultrathin nickel cobaltite (NiCo₂O₄) nanosheets with enriched oxygen vacancies and surface phosphate ions (P–NiCo₂O_4‐x) are reported as a new high‐energy‐density cathode material for rechargeable Zn‐ion batteries. The oxygen‐vacancy and surface phosphate‐ion modulation are achieved by annealing the pristine NiCo₂O₄ nanosheets using a simple phosphating process. Benefiting from the merits of substantially improved electrical conductivity and increased concentration of active sites, the optimized P–NiCo₂O_4‐x nanosheet electrode delivers remarkable capacity (309.2 mAh g^?1 at 6.0 A g^?1) and extraordinary rate performance (64% capacity retention at 60.4 A g^?1). Moreover, based on the P–NiCo₂O_4‐x cathode, our fabricated P–NiCo₂O_4‐x//Zn battery presents an impressive specific capacity of 361.3 mAh g^?1 at the high current density of 3.0 A g^?1 in an alkaline electrolyte. Furthermore, extremely high energy density (616.5 Wh kg^?1) and power density (30.2 kW kg^?1) are also achieved, which outperforms most of the previously reported aqueous Zn‐ion batteries. This ultrafast and high‐energy aqueous Zn‐ion battery is promising for widespread application to electric vehicles and intelligent devices.     

Regulating pH value synthesis of NiCo2O4 with excellent electromagnetic wave absorbing performance

In last several decades, electromagnetic wave (EMW) absorbing materials have attracted much attention because of their ability to attenuate EMW and reduce the electromagnetic pollution caused by the rapid development of information technology. Among many electromagnetic wave absorbers, nickel cobaltite (NiCo₂O₄) stands out for its excellent electromagnetic wave absorbing performance. However, as the most commonly used synthesis method of NiCo₂O₄-based materials, hydrothermal method is time-consuming and complicated, which hinders the actual production and application of nickel cobaltite. In this work, agglomerate NiCo₂O₄ of lamellar accumulation was prepared by chemical coprecipitation and calcination with oxalic acid as precipitant. The effect of pH control on the properties of product was studied by adding ammonia to change the microenvironment of coprecipitation system. When the pH value of the coprecipitation system is 7, the absorbent has been prepared successfully which has broad absorption bandwidth of 6.26 GHz (11.74–18 GHz) and ultrathin matching thickness of 1.58 mm. The synthesis method is simple, convenient, time-saving and energy-saving, and the product has excellent electromagnetic wave absorption capacity, which has a good industrial application prospect.

     

Yolk–Shell MnO@ZnMn2O4/N–C Nanorods Derived from α‐MnO2/ZIF‐8 as Anode Materials for Lithium Ion Batteries

Manganese oxides (MnO_x) are promising anode materials for lithium ion batteries, but they generally exhibit mediocre performances due to intrinsic low ionic conductivity, high polarization, and poor stability. Herein, yolk–shell nanorods comprising of nitrogen‐doped carbon (N–C) coating on manganese monoxide (MnO) coupled with zinc manganate (ZnMn₂O₄) nanoparticles are manufactured via one‐step carbonization of α‐MnO₂/ZIF‐8 precursors. When evaluated as anodes for lithium ion batteries, MnO@ZnMn₂O₄/N–C exhibits an reversible capacity of 803 mAh g^?1 at 50 mA g^?1 after 100 cycles, excellent cyclability with a capacity of 595 mAh g^?1 at 1000 mAg^?1 after 200 cycles, as well as better rate capability compared with those non‐N–C shelled manganese oxides (MnO_x). The outstanding electrochemical performance is attributed to the unique yolk–shell nanorod structure, the coating effect of N–C and nanoscale size.     

Synthesis and electrochemical property of LiFePO4 with core-shell structures

制备热解炭/磷酸亚铁锂和纳米炭纤维/磷酸亚铁锂核壳结构材料, 研究了电化学性能. 结果表明, 热解炭和纳米炭纤维包覆层能有效地降低磷酸亚铁锂材料的电阻率, 大大提高材料的充放电容量和循环稳定性. 与热解炭相比, 纳米炭纤维具有一维结构和优异的力学性能, 更适于作为磷酸亚铁锂电极材料的高效导电剂.     

NiCo2O4-Based Nanosheets with Uniform 4 nm Mesopores for Excellent Zn–Air Battery Performance

Herein, a strategy is reported for the fabrication of NiCo₂O₄-based mesoporous nanosheets (PNSs) with tunable cobalt valence states and oxygen vacancies. The optimized NiCo_2.148O₄ PNSs with an average Co valence state of 2.3 and uniform 4 nm nanopores present excellent catalytic performance with an ultralow overpotential of 190 mV at a current density of 10 mA cm⁻² and long-term stability (700 h) for the oxygen evolution reaction (OER) in alkaline media. Furthermore, Zn–air batteries built using the NiCo_2.148O₄ PNSs present a high power and energy density of 83 mW cm⁻² and 910 Wh kg⁻¹, respectively. Moreover, a portable battery box with NiCo_2.148O₄ PNSs as the air cathode presents long-term stability for 120 h under low temperatures in the range of 0 to −35 °C. Density functional theory calculations reveal that the prominent electron exchange and transfer activity of the electrocatalyst is attributed to the surface lower-coordinated Co-sites in the porous region presenting a merging 3d–e_g–t_2g band, which overlaps with the Fermi level of the Zn–air battery system. This favors the adsorption of the *OH, and stabilized *O radicals are reached, toward competitively lower overpotential, demonstrating a generalized key for optimally boosting overall OER performance.     

Hydrogen sorption properties of MgH2–NiCo2O4 composites activated mechanically under argon and hydrogen atmospheres

The effect of the mechanical activation medium on the hydrogen absorption–desorption properties of MgH₂ with NiCo₂O₄ additives is investigated. The composite 90 wt.% MgH₂–10 wt.% NiCo₂O₄ mechanically activated for 180 min under hydrogen reaches a higher absorption capacity as compared to the composite ground for the same time in an argon medium. At T = 573 K and P = 1 MPa the composite activated mechanically in a reactive medium shows a value of 5.67 wt.% while for the composite ground under argon the value is 4.36 wt.% only, both samples preserving a high absorption capacity at temperatures below 573 K. Addition of nickel cobaltite is found to have a favorable effect on the hydriding kinetics of magnesium. In order to elucidate this effect, a composite containing a large amount of NiCo₂O₄ (50 wt.%) is also investigated.     

A High‐Rate V2O5 Hollow Microclew Cathode for an All‐Vanadium‐Based Lithium‐Ion Full Cell

V₂O₅ hollow microclews (V₂O₅‐HMs) have been fabricated through a facile solvothermal method with subsequent calcination. The synthesized V₂O₅‐HMs exhibit a 3D hierarchical structure constructed by intertangled nanowires, which could realize superior ion transport, good structural stability, and significantly improved tap density. When used as the cathodes for lithium‐ion batteries (LIBs), the V₂O₅‐HMs deliver a high capacity (145.3 mAh g^‐1) and a superior rate capability (94.8 mAh g^‐1 at 65 C). When coupled with a lithiated Li₃VO₄ anode, the all‐vanadium‐based lithium‐ion full cell exhibits remarkable cycling stability with a capacity retention of 71.7% over 1500 cycles at 6.7 C. The excellent electrochemical performance demonstrates that the V₂O₅‐HM is a promising candidate for LIBs. The insight obtained from this work also provides a novel strategy for assembling 1D materials into hierarchical microarchitectures with anti‐pulverization ability, excellent electrochemical kinetics, and enhanced tap density.     

负极活性材料Li4Ti5O12的研究进展

介绍了负极材料Li₄Ti₅O₁₂的物理特性和电化学性能,详细介绍并评述了Li₄Ti₅O₁₂ 在锂离子电池和不对称型超级电容器中的应用情况,总结了Li₄Ti₅O₁₂的不同合成方法及材料的电化学改性研究进展.     

A Facile Strategy to Construct Silver‐Modified,ZnO‐Incorporated and Carbon‐Coated Silicon/Porous‐Carbon Nanofibers with Enhanced Lithium Storage

For Si anode materials used for lithium ion batteries (LIBs), developing an effective solution to overcome their drawbacks of large volume change and poor electronic conductivity is highly desirable. Here, the composites of ZnO‐incorporated and carbon‐coated silicon/porous‐carbon nanofibers (ZnO‐Si@C‐PCNFs) are designed and synthesized via a traditional electrospinning method. The prepared ZnO‐Si@C‐PCNFs can obviously overcome these two drawbacks and provide excellent LIB performance with excellent rate capability and stable long cycling life of 1000 cycles with reversible capacity of 1050 mA h g^?1 at 800 mA g^?1. Meanwhile, anodes of ZnO‐Si@C‐PCNFs attached with Ag particles display enhanced LIB performance, maintaining an average capacity of 920 mA h g^?1 at a large current of 1800 mA g^?1 even for 1000 cycles with negligible capacity loss and excellent reversibility. In addition, the assembling method with important practical significance for a simple pouch full cell is designed and used to evaluate the active materials. The Ag/ZnO‐Si@C‐PCNFs are prelithiated and assembled in full cells using LiNi_0.5Co_0.2Mn_0.3O₂(NCM523) as cathodes, exhibiting higher energy density (230 W h kg^?1) of 18% than that of 195 W h kg^?1 for commercial graphite//NCM523 full pouch cells. Importantly, the comprehensive mechanisms of enhanced electrochemical kinetics originating from ZnO‐incorporation and Ag‐attachment are revealed in detail.     

Advanced rechargeable lithium-ion batteries based on bendable ZnCo2O4-urchins-on-carbon-fibers electrodes

A novel class of ZnCo₂O₄-urchins-on-carbon-fibers matrix has been designed, characterized, and used to fabricate high-performance energy storage devices. We obtained a reversible lithium storage capacity of 1180 mA·h/g even after 100 cycles, demonstrating the highreversible capacity and excellent cycle life of the as-prepared samples. Tested as fast-charging batteries, these electrodes exhibited a considerable capacity of 750 mA·h/g at an exceptionally high rate of 20 C (18 A/g), with an excellent cycle life (as long as 100 cycles), which are the best high-rate results reported at such a high charge/discharge current density for ZnCo₂O₄-based anode materials in lithium rechargeable batteries. Such attractive properties may be attributed to the unique structure of the binder-free ZnCo₂O₄-urchins-on-carbon-fibers matrix. Full batteries were also developed by combining the ZnCo₂O₄ anodes with commercial LiCoO₂ cathodes, which showed flexible/wearable and stable features for use as very promising future energy storage units.      

A review for the synthesis methods of lithium vanadium phosphate cathode materials

Monoclinic Lithium vanadium phosphate [Li₃V₂(PO₄)₃, LVP] has been extensively studied because of its attractive electrochemical properties including high specific energy, high specific capacity (133 mAh g^?1 in 3.0–4.3 V, 197 mAh g^?1 in 3.0–4.8 V), high working voltage (4.0 V), good cycle stability and low price used in rechargeable lithium ion batteries (LIBs). However, the inherent defects such as low conductivity still restrict its practical application in high performance LIBs. Various synthesis methods have been developed in order to improve electrochemical performances of LVP. The results show that the different synthesis methods have great influence on the properties of LVP cathodes for LIBs, so the study on the synthesis method of high performance LVP will continue to be in great demand. This review briefly introduces the present synthesis methods of LVP, such as high-temperature solid-state method, sol–gel method, hydrothermal method, etc. Apart from already established conventional routes, the novel preparation technologies are also mentioned. Moreover, the synthesis mechanism and electrochemical performances of Li₃V₂(PO₄)₃ cathode materials synthesized by each synthetic method are reviewed. Finally, the directions for further research and prospective applications for the LVP materials are proposed.     

SnO2‐Based Nanomaterials: Synthesis and Application in Lithium‐Ion Batteries

The development of new electrode materials for lithium‐ion batteries (LIBs) has always been a focal area of materials science, as the current technology may not be able to meet the high energy demands for electronic devices with better performance. Among all the metal oxides, tin dioxide (SnO₂) is regarded as a promising candidate to serve as the anode material for LIBs due to its high theoretical capacity. Here, a thorough survey is provided of the synthesis of SnO₂‐based nanomaterials with various structures and chemical compositions, and their application as negative electrodes for LIBs. It covers SnO₂ with different morphologies ranging from 1D nanorods/nanowires/nanotubes, to 2D nanosheets, to 3D hollow nanostructures. Nanocomposites consisting of SnO₂ and different carbonaceous supports, e.g., amorphous carbon, carbon nanotubes, graphene, are also investigated. The use of Sn‐based nanomaterials as the anode material for LIBs will be briefly discussed as well. The aim of this review is to provide an in‐depth and rational understanding such that the electrochemical properties of SnO₂‐based anodes can be effectively enhanced by making proper nanostructures with optimized chemical composition. By focusing on SnO₂, the hope is that such concepts and strategies can be extended to other potential metal oxides, such as titanium dioxide or iron oxides, thus shedding some light on the future development of high‐performance metal‐oxide based negative electrodes for LIBs.     

Electrolyte Engineering on Performance Enhancement of NiCo2S4 Anode for Sodium Storage

NiCo₂S₄ is an attractive anode for sodium-ion batteries (SIBs) due to its high capacity and excellent redox reversibility. Practical deployment of NiCo₂S₄ electrode in SIBs, however, is still hindered by the inferior capacity and unsatisfactory cycling performance, which result from the mismatch between the electrolyte chemistry and electrode. Herein, a functional electrolyte containing 1.0 m NaCF₃SO₃ in diethylene glycol dimethyl ether (DEGDME) (1.0 m NaCF₃SO₃-DEGDME) is developed, which can be readily used for NiCo₂S₄ anode with high initial coulomb efficiency (96.2%), enhanced cycling performance, and boosted capacities (341.7 mA h g⁻¹ after 250 continuous cycles at the current density of 200 mA g⁻¹). The electrochemical tests and related phase characterization combined with density functional theory (DFT) calculation indicate the ether-based electrolyte is more suitable for the NiCo₂S₄ anode in SIBs due to the formation of a stable electrode–electrolyte interface. Additionally, the importance of the voltage window is also demonstrated to further optimize the electrochemical performance of the NiCo₂S₄ electrode. The formation of sulfide intermediates during charging and discharging is predicted by combining DFT and verified by in situ XRD and HRTEM. The findings indicate that electrolyte engineering would be an effective way of performance enhancement for sulfides in practical SIBs.     

Hydrothermal synthesis of carbon nanotube/cubic Fe3O4 nanocomposite for enhanced performance supercapacitor electrode material

Carbon nanotube/Fe₃O₄ (CNT/Fe₃O₄) nanocomposite with well-dispersed Fe₃O₄ nano-cubes inlaid on the surfaces of carbon nanotubes, was synthesized through an easy and efficient hydrothermal method. The electrochemical behaviors of the nanocomposite were analyzed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronopotentiometry in 6 M KOH electrolyte. Results demonstrated that CNT as the supporting material could significantly improve the supercapacitor (SC) performance of the CNT/Fe₃O₄ composite. Comparing with pure Fe₃O₄, the resulting composite exhibited improved specific capacitances of 117.2 F/g at 10 mA/cm² (3 times than that of pure Fe₃O₄), excellent cyclic stability and a maximum energy density of 16.2 Wh/kg. The much improved electrochemical performances could be attributed to the good conductivity of CNTs as well as the anchored Fe₃O₄ particles on the CNTs.     

Phase Separation Derived Core/Shell Structured Cu11V6O26/V2O5 Microspheres: First Synthesis and Excellent Lithium‐Ion Anode Performance with Outstanding Capacity Self‐Restoration

Novel amorphous vanadium oxide coated copper vanadium oxide (Cu₁₁V₆O₂₆/V₂O₅) microspheres with 3D hierarchical architecture have been successfully prepared via a microwave‐assisted solution method and subsequent annealing induced phase separation process. Pure Cu₁₁V₆O₂₆ microspheres without V₂O₅ coating are also obtained by an H₂O₂ solution dissolving treatment. When evaluated as an anode material for lithium‐ion batteries (LIBs), the as‐synthesized hybrid exhibits large reversible capacity, excellent rate capability, and outstanding capacity self‐recovery. Under the condition of high current density of 1 A g^?1, the 3D hierarchical Cu₁₁V₆O₂₆/V₂O₅ hybrid maintains a reversible capacity of ≈1110 mA h g^?1. Combined electrochemical analysis and high‐resolution transmission electron microscopy observation during cycling reveals that the amorphous V₂O₅ coating plays an important role on enhancing the electrochemical performances and capacity self‐recovery, which provides an active amorphous protective layer and abundant grain interfaces for efficient inserting and extracting of Li‐ion. As a result, this new copper vanadium oxide hybrid is proposed as a promising anode material for LIBs.