An overview of AB2O4- and A2BO4-structured negative electrodes for advanced Li-ion batteries

Energy-storage devices are state-of-the-art devices with many potential technical and domestic applications.

Porous mixed metal oxides: design, formation mechanism, and application in lithium-ion batteries

The relentless pursuit of new electrode materials for lithium ion batteries (LIBs) has been conducted for decades. Structures with either porous or nanostructure configurations have been confirmed as advantageous candidates for energy storage/conversion applications. The integration of the two features into one structure can provide another chance to improve the electroactivities. Recently, single-phased mixed metal oxides (MMOs) containing different metal cations, in particular, have confirmed high electrochemical activities because of their complex chemical composition, interfacial effects, and the synergic effects of the multiple metal species. In this review, we will focus on recent research advances of MMOs with porous architectures as anode materials in the matter of structural arrangement and compositional manipulation. Moreover, the application of self-supported MMO-based porous structures as LIB anodes is also explained herein. More importantly, investigations on the synthetic system and formation mechanism of porous MMOs will be highlighted. Some future trends for the innovative design of new electrode materials are also discussed in this review. The challenges and prospects will draw many researchers' attention.

Hierarchical Porous ZnMn2 O4 Hollow Nanotubes with Enhanced Lithium Storage toward Lithium-Ion Batteries

We have purposefully developed a smart template-engaged methodology to efficiently fabricate well-defined ternary spinel ZnMn2 O4 hollow nanotubes (NTs). The procedure involves coating carbon nanotubes (CNTs) with ZnMn2 O4 nanosheets (NSs), followed by heating at high temperature in air to oxidize the CNT template. Physicochemical characterization demonstrated that the formed ZnMn2 O4 NTs with a diameter of approximately 100 nm were composed of assembled NSs and/or nanoparticles (NPs) as building blocks and possessed numerous nanopores of several nanometers in the sidewall of the NTs. In favor of the intrinsic structural advantages, the resulting ZnMn2 O4 NTs exhibited superior electrochemical lithium-storage performance with a large capacity, good rate behavior, and excellent cyclability when evaluated as promising anodes for lithium-ion batteries (LIBs). The remarkable electrochemical performance was rationally ascribed to the appealing one-dimensional (1D) porous hollow tubular architecture with nanoscale subunits and mesopores in the sidewalls, which decreased the diffusion length for the Li(+) ions, improved the kinetic process, and enhanced the structural integrity with sufficient void space to tolerate the volume variation during Li(+) -ion insertion/extraction. These results highlight the promising application of 1D ZnMn2 O4 NTs as anodes for high-performance LIBs.

Heterostructured core-shell ZnMn₂O₄ nanosheets@carbon nanotubes' coaxial nanocables: a competitive anode towards high-performance Li-ion batteries

In this study, we rationally designed a rapid, low-temperature yet general synthetic methodology for the first time, involving in situ growth of two-dimensional (2D) birnessite-type MnO2 nanosheets (NSs) upon each carbon nanotube (CNT), and we designed the subsequent phase transformation into untrathin mesoporous ZnMn2O4 NSs with a thickness of ∼2-3 nm at room temperature to efficiently fabricate heterostructured core-shell ZnMn2O4 NSs@CNT coaxial nanocables with well-dispersed and tunable ZnMn2O4 loading. The underlying insights into the low-temperature formation mechanism of the unique core-shell hybrid nanoarchitectures were tentatively proposed here. When utilized as a high-performance anode for advanced LIBs, the resultant core-shell ZnMn2O4@CNTs' coaxial nanocables (∼84.5 wt.% loading) exhibited large specific discharge capacity (∼1033 mAh g(-1)), good rate capability (∼528 mAh g(-1)) and excellent cycling stability (average capacity degradation of only ∼5.2% per cycle) at a high current rate of 1224 mA g(-1), originating from the distinct core-shell synergetic effect of fast electronic delivery and from the large electrode/electrolyte contacting surfaces/interfaces provided by three-dimensional entangling coaxial CNT-based nanonetwork topology.

High interfacial storage capability of porous NiMn2O4/C hierarchical tremella-like nanostructures as the lithium ion battery anode

Porous hierarchical NiMn2O4/C tremella-like nanostructures are obtained through a simple solvothermal and calcination method. As the anode of lithium ion batteries (LIBs), porous NiMn2O4/C nanostructures exhibit a superior specific capacity and an excellent long-term cycling performance even at a high current density. The discharge capacity can stabilize at 2130 mA h g(-1) within 350 cycles at a current density of 1000 mA g(-1). After a long-term cycling of 1500 cycles, the capacity is still as high as 1773 mA h g(-1) at a high current density of 4000 mA g(-1), which is almost five times higher than the theoretical capacity of graphite. The porous NiMn2O4/C hierarchical nanostructure provides sufficient contact with the electrolyte and fast three-dimensional Li(+) diffusion channels, and dramatically improves the capacity of NiMn2O4/C via interfacial storage.

High-performance nickel manganese ferrite/oxidized graphene composites as flexible and binder-free anodes for Li-ion batteries

The obtained binder-free and flexible free-standing Ni_0.5Mn_0.5Fe₂O₄/oxidized graphene (NMFO/OGP) and NMFO/OGP coated on polypropylene microporous film exhibited good electrochemical performance.

The preparation of flowerlike ZnMn2O4 microspheres assembled with porous nanosheets and their lithium battery performance as anode materials

Hierarchical flowerlike ZnMn₂O₄ microspheres with high electrochemical performance as an anode material for Li-ion batteries have been fabricated by a facile solvothermal method.

Ultrafast spray pyrolysis fabrication of a nanophase ZnMn2O4 anode towards high-performance Li-ion batteries

Nanophase ZnMn₂O₄ was ultrafast fabricated via a green spray pyrolysis strategy, and exhibited large initial specific discharge capacity, good rate capability, and excellent cycling stability at 1 C rate.

Core–shell-structured nickel ferrite/onion-like carbon nanocapsules: an anode material with enhanced electrochemical performance for lithium-ion batteries

Core–shell-structured nanocapsules consisting of a nickel ferrite (NiFe₂O₄) nanoparticle core encapsulated in an onion-like carbon (C) shell are prepared by a modified arc-discharge method followed by an air-annealing process.

Pristine hollow microspheres of Mn2O3 as a potential anode for lithium-ion batteries

Ascorbic acid aided inside-out Ostwald ripening promotes the formation of Mn₂O₃ microspheres with a hollow interior surface that exhibits an appreciable capacity of 610 mA h g⁻¹, even after completing 100 cycles.

Synthesis of graphene-wrapped ZnMn2O4 hollow microspheres as high performance anode materials for lithium ion batteries

A facile method for the synthesis of graphene-wrapped ZnMn₂O₄ hollow microspheres which show excellent electrochemical performance.

Enhanced electrochemical performance of a ZnO–MnO composite as an anode material for lithium ion batteries

A reduced ZnO–MnO composite electrode exhibits improved electrochemical performance as an anode material for lithium ion batteries.

General formation of Mn-based transition metal oxide twin-microspheres with enhanced lithium storage properties

Complex metal oxide twin-microspheres were synthesized by a general strategy involving the synthesis of carbonate twin-spheres and subsequent thermal annealing. Their structural features cause excellent electrochemical performance as anode electrode materials for LIBs.

Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems

Transition metal oxides possessing two kinds of metals (denoted as A_xB_3−xO₄, which is generally defined as a spinel structure; A, B = Co, Ni, Zn, Mn, Fe,etc.), with stoichiometric or even non-stoichiometric compositions, have recently attracted great interest in electrochemical energy storage systems (ESSs).

MOF-derived porous ZnO/ZnFe₂O₄/C octahedra with hollow interiors for high-rate lithium-ion batteries

Novel porous ZnO/ZnFe2O4/C octahedra with hollow interiors are fabricated by a facile self-sacrificing template method involving the refluxing synthesis of hollow, metal-organic framework octahedra in solution and subsequent thermal annealing in N2 . When evaluated as an anode material for lithium-ion batteries, these porous hollow ZnO/ZnFe2O4/C octahedra exhibit significantly enhanced electrochemical performances with high rate capability, high capacity, and excellent cycling stability.

Nanostructure copper oxocobaltate fabricated by co-precipitation route using copper and cobalt nitrate as precursors: characterization by combined diffuse reflectance and FT infrared spectra

Nanostructure copper oxocobaltate has been fabricated by a co-precipitation route using copper and cobalt nitrate as precursors. The physicochemical properties of copper cobaltate have been characterized via X-ray powder diffractometry (XRD) and field emission scanning electron microscopy (FESEM). The X-ray diffraction patterns indicates the presence of a spinel crystalline phase, (Cu0.30Co0.70)Co2O4, copper oxocobaltate with face-centered cubic lattice and Fd3m space group. FESEM images also illustrated a typical hexagonal morphology with particle size 25 nm, showing a good nanoscale crystalline morphology, which corresponds well with their XRD results. The FTIR spectra confirmed the presence of hydroxyl groups bonded to the metals, stretching vibration of the cobalt-oxygen bond in an octahedral coordination and the characteristic band assigned to the vibration of Cu-O bond. UV-VIS diffuse reflectance spectrum shows a broad band over the whole visible range and broad band between 200 nm and 390 nm ascribed to the ligand to metal charge transfer.

Highly porous NiCo2O4 Nanoflakes and nanobelts as anode materials for lithium-ion batteries with excellent rate capability

Highly porous NiCo2O4 nanoflakes and nanobelts were synthesized by using a hydrothermal technique, followed by calcination of the NiCo2O4 precursors. The as-synthesized materials were analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and Brunauer-Emmett-Teller methods. The NiCo2O4 nanoflakes and nanobelts were applied as anode materials for lithium-ion batteries. Owing to the unique porous structural features, the NiCo2O4 nanoflakes and nanobelts exhibited high specific capacities of 1033 and 1056 mA h g(-1), respectively, and good cycling stability and rate capability. These exceptional electrochemical performances could be ascribed to the remarkable structural feature with a high surface area and void spaces within the surface of nanoflakes and nanobelts, which provide large contact areas between electrolyte and active materials for electrolyte diffusion and cushion the volume variation during the lithium-ion insertion/extraction process.

Chemically integrated two-dimensional hybrid zinc manganate/graphene nanosheets with enhanced lithium storage capability

Hybrid inorganic/graphene two-dimensional (2D) nanostructures can offer vastly open large surface areas for ion transport and storage and enhanced electron transport, representing a promising material platform for next-generation energy storage. Here we report chemically integrated hybrid ZnMn2O4/graphene nanosheets synthesized via a facile two-step method for greatly enhanced lithium storage capability. The hybrid 2D nanosheets are composed of ultrafine ZnMn2O4 nanocrystals with a mean diameter of ∼4 nm attached to and well dispersed on the surface of reduced graphene oxide sheets. The hybrid nanosheets based anode offers a high capacity of ∼800 mAh g(–1) at a current rate of 500 mA g(–1), excellent rate capability, and long-term cyclability with reversible capacity of ∼650 mAh g(–1) over 1500 cycles at a current density of 2000 mA g(–1). Moreover, when tested in a temperature range of ∼0–60 °C, the designed anode can maintain high discharge capacities from 570 to 820 mAh g(–1).

Hollow MnCo2O4 submicrospheres with multilevel interiors: from mesoporous spheres to yolk-in-double-shell structures

We present a general strategy to synthesize uniform MnCo2O4 submicrospheres with various hollow structures. By using MnCo-glycolate submicrospheres as the precursor with proper manipulation of ramping rates during the heating process, we have fabricated hollow MnCo2O4 submicrospheres with multilevel interiors, including mesoporous spheres, hollow spheres, yolk-shell spheres, shell-in-shell spheres, and yolk-in-double-shell spheres. Interestingly, when tested as anode materials in lithium ion batteries, the MnCo2O4 submicrospheres with a yolk-shell structure showed the best performance among these multilevel interior structures because these structures can not only supply a high contact area but also maintain a stable structure.

Hollow/porous nanostructures derived from nanoscale metal-organic frameworks towards high performance anodes for lithium-ion batteries

Lithium-ion batteries (LIBs), owing to their high energy density, light weight, and long cycle life, have shown considerable promise for storage devices. The successful utilization of LIBs depends strongly on the preparation of nanomaterials with outstanding lithium storage properties. Recent progress has demonstrated that hollow/porous nanostructured oxides are very attractive candidates for LIBs anodes due to their high storage capacities. Here, we aim to provide an overview of nanoscale metal-organic frameworks (NMOFs)-templated synthesis of hollow/porous nanostructured oxides and their LIBs applications. By choosing some typical NMOFs as examples, we present a comprehensive summary of synthetic procedures for nanostructured oxides, such as binary, ternary and composite oxides. Hollow/porous structures are readily obtained due to volume loss and release of internally generated gas molecules during the calcination of NMOFs in air. Interestingly, the NMOFs-derived hollow/porous structures possess several special features: pores generated from gas molecules release will connect to each other, which are distinct from "dead pores"; pore size often appears to be <10 nm; in terms of surface chemistry, the pore surface is hydrophobic. These structural features are believed to be the most critical factors that determine LIBs' performance. Indeed, it has been shown that these NMOFs-derived hollow/porous oxides exhibit excellent electrochemical performance as anode materials for LIBs, including high storage capacity, good cycle stability, and so on. For example, a high charge capacity of 1465 mA h g(-1) at a rate of 300 mA g(-1) was observed after 50 cycles for NMOFs-derived Co3O4 porous nanocages, which corresponds to 94.09% of the initial capacity (1557 mA h g(-1)), indicating excellent stability. The capacity of NMOFs-derived Co3O4 is higher than that of other Co3O4 nanostructures obtained by a conventional two-step route, including nanosheets (1450 mA h g(-1) at 50 mA g(-1)), nanobelts (1400 mA h g(-1) at 40 mA g(-1)) and nanoflowers (694 mA h g(-1) at 100 mA g(-1)). The capacity is also better than Co3O4 octahedra obtained by a one-step hydrothermal method (946 mA h g(-1) at 100 mA g(-1)). In this review, we will summarize the recent research advances on NMOFs-derived hollow/porous oxides as LIBs anodes. The enhanced lithium storage properties have been discussed in relation to their special structural parameters. Moreover, remarks on the current challenges and perspectives for future NMOFs applications are proposed. Through this systematic review, we aim to stress the importance of NMOFs templates for the fabrication of hollow/porous functional materials that would result in improved physicochemical properties and provide insights to guide future research for LIBs applications.

Recent advances in Mn-based oxides as anode materials for lithium ion batteries

The Mn-based oxides including MnO, Mn₃O₄, Mn₂O₃, MnO₂, CoMn₂O₄, ZnMn₂O₄and their carbonaceous composite/oxide supports with different morphologies and compositions as anode materials are reviewed.

Synthesis of multi-shelled ZnO hollow microspheres and their improved photocatalytic activity

Herein, we report an effective, facile, and low-cost route for preparing ZnO hollow microspheres with a controlled number of shells composed of small ZnO nanoparticles. The formation mechanism of multiple-shelled structures was investigated in detail. The number of shells is manipulated by using different diameters of carbonaceous microspheres. The products were characterized by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. The as-prepared ZnO hollow microspheres and ZnO nanoparticles were then used to study the degradation of methyl orange (MO) dye under ultraviolet (UV) light irradiation, and the triple-shelled ZnO hollow microspheres exhibit the best photocatalytic activity. This work is helpful to develop ZnO-based photocatalysts with high photocatalytic performance in addressing environmental protection issues, and it is also anticipated to other multiple-shelled metal oxide hollow microsphere structures.

Copper doped hollow structured manganese oxide mesocrystals with controlled phase structure and morphology as anode materials for lithium ion battery with improved electrochemical performance

We develop a facile synthesis route to prepare Cu doped hollow structured manganese oxide mesocrystals with controlled phase structure and morphology using manganese carbonate as the reactant template. It is shown that Cu dopant is homogeneously distributed among the hollow manganese oxide microspherical samples, and it is embedded in the lattice of manganese oxide by substituting Mn(3+) in the presence of Cu(2+). The crystal structure of manganese oxide products can be modulated to bixbyite Mn2O3 and tetragonal Mn3O4 in the presence of annealing gas of air and nitrogen, respectively. The incorporation of Cu into Mn2O3 and Mn3O4 induces a great microstructure evolution from core-shell structure for pure Mn2O3 and Mn3O4 samples to hollow porous spherical Cu-doped Mn2O3 and Mn3O4 samples with a larger surface area, respectively. The Cu-doped hollow spherical Mn2O3 sample displays a higher specific capacity of 642 mAhg(-1) at a current density of 100 mA g(-1) after 100 cycles, which is about 1.78 times improvement compared to that of 361 mA h g(-1) for the pure Mn2O3 sample, displaying a Coulombic efficiency of up to 99.5%. The great enhancement of the electrochemical lithium storage performance can be attributed to the improvement of the electronic conductivity and lithium diffusivity of electrodes. The present results have verified the ability of Cu doping to improve electrochemical lithium storage performances of manganese oxides.

Fabrication of free-standing ZnMn2O4 mesoscale tubular arrays for lithium-ion anodes with highly reversible lithium storage properties

In this paper, ZnMn2O4 mesoscale tubular arrays on current collectors were successfully synthesized using a reactive template route combined with a postcalcination process through the shape-preserving conversion of ZnO nanorod arrays in aqueous solutions at room temperature. On the basis of the experimental analyses, including X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy, a plausible formation mechanism of ZnMn2O4 tubular arrays was proposed in which solid ZnO nanorods are gradually transformed to ZnMn2O4 tubules via a simple cation exchange process between Zn(2+) and Mn(2+), followed by a postannealing process. Moreover, the lithium storage properties of the as-prepared ZnMn2O4 tubular structures were investigated by applying the structures as an active electrode material without auxiliary additives. The ZnMn2O4 array electrodes showed an excellent discharge capacity of ca. 1198.3 mAh g(-1) on the first cycle and exhibited outstanding cycling durability, rate capability, and Coulombic efficiency. These results indicate that the free-standing tubular array architectures of ZnMn2O4 prepared directly on the current collector can be powerful candidates for a highly reversible lithium storage electrode platform.

Self-assembled Fe3O4 nanoparticle clusters as high-performance anodes for lithium ion batteries via geometric confinement

Although different kinds of metal oxide nanoparticles continue to be proposed as anode materials for lithium ion batteries (LIBs), their cycle life and power density are still not suitable for commercial applications. Metal oxide nanoparticles have a large storage capacity, but they suffer from the excessive generation of solid-electrolyte interphase (SEI) on the surface, low electrical conductivity, and mechanical degradation and pulverization resulted from severe volume expansion during cycling. Herein we present the preparation of mesoporous iron oxide nanoparticle clusters (MIONCs) by a bottom-up self-assembly approach and demonstrate that they exhibit excellent cyclic stability and rate capability derived from their three-dimensional mesoporous nanostructure. By controlling the geometric configuration, we can achieve stable interfaces between the electrolyte and active materials, resulting in SEI formation confined on the outer surface of the MIONCs.