Zhaoqiang Li

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.

Prussion Blue-Supported Annealing Chemical Reaction Route Synthesized Double-Shelled Fe2O3/Co3O4 Hollow Microcubes as Anode Materials for Lithium-Ion Battery

Fe2O3/Co3O4 double-shelled hierarchical microcubes were synthesized based on annealing of double-shelled Fe4[Fe(CN)6]3/Co(OH)2 microcubes, using Co(AC)2 as a Co(2+) source to react with OH(-) generated from the reaction of ammonium hydroxide and water. The robust Fe2O3 hollow microcube at the inner layer not only displays a good electronic conductivity but also acts as stable supports for hierarchical Co3O4 outside shell consisting of nanosized particles. The double-shelled hollow structured Fe2O3/Co3O4 nanocomposites display obvious advantages as anode materials for LIBs. The hollow structure can ensure the presence of additional free volume to alleviate the structural strain associated with repeated Li(+)-insertion/extraction processes, as well as a good contact between electrode and electrolyte. The robust Fe2O3 shell acts as a strong support for Co3O4 nanoparticles and efficiently prevents the aggregation of the Co3O4 nanoparticles. Furthermore, the charge transfer resistance can be greatly decreased because of the formation of interface between Fe2O3 and Co3O4 shells and a relative good electronic conductivity of Fe2O3 than that of Co3O4, resulting in a decrease of charge transfer resistance for improving the electron kinetics for the hollow double-shelled microcube as anode materials for LIBs. The Fe2O3/Co3O4 nanocomposite anode with a molar ratio of 1:1 for Fe:Co exhibits the best cycle performance, displaying an initial Coulombic efficiency of 74.4%, delivering a specific capacity of 500 mAh g(-1) after 50 cycles at a current density of 100 mA g(-1), 3 times higher than that of pure Co3O4 nanoparticle sample. The great improvement of the electrochemical performance of the synthesized Fe2O3/Co3O4 double-shelled hollow microcubes can be attributed to the unique microstructure characteristics and synergistic effect between the inner shell of Fe2O3 and outer shell of Co3O4.

Three-dimensional nanohybrids of Mn3O4/ordered mesoporous carbons for high performance anode materials for lithium-ion batteries

We developed a facile one-step route to three-dimensional hybrids with Mn3O4 nanoparticles well and homogeneously embedded within ordered mesoporous carbon (OMC) for lithium ion battery applications. The Mn3O4/OMC hybrids with good rate capability and cycling stability display a high specific capacity up to 802 mA h g−1, and a high coulombic efficiency of up to 99.2% even after 50 cycles at a high current density of 100 mA g−1. This value is 1.6 times higher than the discharge capacity of 512 mA h g−1 for pure ordered OMC materials, and more than 5.4 times higher than the discharge value of 148 mA h g−1 for pure Mn3O4 nanoparticles. The enhanced capacity and cycling performance of the Mn3O4/OMC hybrids could be attributed to their unique robust three-dimensional composite structure and the synergistic effects between the Mn3O4 nanoparticles and OMC. The ordered mesostructured channels of Mn3O4/OMC hybrids are expected to buffer well against the local volume change during the Li uptake/removal reactions and thus to enhance the structural stability. The OMC matrix wall with a thickness of <10 nm greatly reduces the solid-state transport length for Li diffusion, and the hierarchical ordered mesoporosity facilitates the liquid electrolyte diffusion into the bulk of the electrode material and hence provides fast conductive ion transport channels for the conductive Li+ ions. The improved cycling performance can also be mainly attributed to good electrical contact between the Mn3O4 and OMC in the three-dimensional nanocomposites during phase transformation of Mn3O4 upon lithiation/delithiation that usually leads to capacity fading. This facile strategy can be extended to fabricate other ordered mesoporous carbon-encapsulated metal oxides.

Metal–Organic Frameworks Derived Porous Core/Shell Structured ZnO/ZnCo2O4/C Hybrids as Anodes for High-Performance Lithium-Ion Battery

Metal-organic frameworks (MOFs) derived porous core/shell ZnO/ZnCo2O4/C hybrids with ZnO as a core and ZnCo2O4 as a shell are for the first time fabricated by using core/shell ZnCo-MOF precursors as reactant templates. The unique MOFs-derived core/shell structured ZnO/ZnCo2O4/C hybrids are assembled from nanoparticles of ZnO and ZnCo2O4, with homogeneous carbon layers coated on the surface of the ZnCo2O4 shell. When acting as anode materials for lithium-ion batteries (LIBs), the MOFs-derived porous ZnO/ZnCo2O4/C anodes exhibit outstanding cycling stability, high Coulombic efficiency, and remarkable rate capability. The excellent electrochemical performance of the ZnO/ZnCo2O4/C LIB anodes can be attributed to the synergistic effect of the porous structure of the MOFs-derived core/shell ZnO/ZnCo2O4/C and homogeneous carbon layer coating on the surface of the ZnCo2O4 shells. The hierarchically porous core/shell structure offers abundant active sites, enhances the electrode/electrolyte contact area, provides abundant channels for electrolyte penetration, and also alleviates the structure decomposition induced by Li(+) insertion/extraction. The carbon layers effectively improve the conductivity of the hybrids and thus enhance the electron transfer rate, efficiently prevent ZnCo2O4 from aggregation and disintegration, and partially buffer the stress induced by the volume change during cycles. This strategy may shed light on designing new MOF-based hybrid electrodes for energy storage and conversion devices.

Sandwich-like reduced graphene oxide wrapped MOF-derived ZnCo2O4–ZnO–C on nickel foam as anodes for high performance lithium ion batteries

A sandwich-like structure with reduced graphene oxide (RGO) wrapped MOF-derived ZnCo2O4–ZnO–C polyhedrons on nickel foam as an anode for high performance lithium ion batteries (LIBs) is for the first time reported via simply growing MOFs on Ni foam, and wrapping graphene oxide nanosheets on MOFs, and then annealing under a N2 atmosphere. It should be noted that the MOF-derived porous products are composed of carbon-coated spinel ZnCo2O4–ZnO nanoparticle polyhedrons. When tested as anodes for LIBs, the unique RGO/ZnCo2O4–ZnO–C/Ni sandwich-structured LIB anodes exhibit superior coulombic efficiency, excellent cycling stability and rate capability. The in situ formed carbon layers outside the ZnCo2O4–ZnO act as not only a conductive substrate but also a buffer layer for volume changes. The open pores in ZnCo2O4–ZnO–C polyhedrons provide sufficient electrolyte as well as serve as cushion space to further alleviate volume changes. The RGO nanosheets act as a flexible protector to firmly fix polyhedrons on the Ni foam, as well as a conductive substrate to wire up all the polyhedrons. The interconnected carbon layers and two high conductive substrates (RGO and Ni foam) together form an unhindered highway for charge transfer during discharge/charge processes, promising good electrochemical performance.

ZnS-Sb2S3@C Core-Double Shell Polyhedron Structure Derived from Metal–Organic Framework as Anodes for High Performance Sodium Ion Batteries

Taking advantage of zeolitic imidazolate framework (ZIF-8), ZnS-Sb2S3@C core-double shell polyhedron structure is synthesized through a sulfurization reaction between Zn2+ dissociated from ZIF-8 and S2- from thioacetamide (TAA), and subsequently a metal cation exchange process between Zn2+ and Sb3+, in which carbon layer is introduced from polymeric resorcinol-formaldehyde to prevent the collapse of the polyhedron. The polyhedron composite with a ZnS inner-core and Sb2S3/C double-shell as anode for sodium ion batteries (SIBs) shows us a significantly improved electrochemical performance with stable cycle stability, high Coulombic efficiency and specific capacity. Peculiarly, introducing a carbon shell not only acts as an important protective layer to form a rigid construction and accommodate the volume changes, but also improves the electronic conductivity to optimize the stable cycle performance and the excellent rate property. The architecture composed of ZnS inner core and a complex Sb2S3/C shell not only facilitates the facile electrolyte infiltration to reduce the Na-ion diffusion length to improve the electrochemical reaction kinetics, but also prevents the structure pulverization caused by Na-ion insertion/extraction. This approach to prepare metal sulfides based on MOFs can be further extended to design other nanostructured systems for high performance energy storage devices.

Ordered mesoporous SnO2 with a highly crystalline state as an anode material for lithium ion batteries with enhanced electrochemical performance

Ordered mesoporous SnO2 materials with many regularly ordered pore channels, uniform size distribution, high surface area, highly crystalline state and good structural stability were synthesized via a facile infiltration chemical route. The synthesized ordered mesoporous SnO2 materials were characterized by X-ray diffraction, Brunauer–Emmett–Teller (BET) method, field emission scanning electron microscopy, and high resolution transmission electron microscopy. Cyclic voltammetry and galvanostatic techniques were utilized to characterize the electrochemical performance of the as prepared SnO2 samples as anode materials for lithium ion batteries. The ordered mesoporous SnO2 displays a good rate capability and cycling stability, exhibiting a high specific capacity of up to 557 mA h g−1, and a high coulombic efficiency of up to 98.5%, even after 40 cycles at a high current density of 100 mA g−1. The significant improvement of the electrochemical performance is attributed to the unique ordered mesoporous structure of SnO2 with a variety of favorable properties. The large surface area endows the synthesized SnO2 with more lithium storage sites and a large electrode–electrolyte contact area for high Li+ ions flux across the interface, a narrow mesopore size distribution is promised to render the liquid electrolyte diffusion into the bulk of the electrode material facile and hence to providing fast transport channels for the solvated Li+ ions, and the regularly ordered mesoporous structures are expected to buffer well against the local volume change during the Li–Sn alloying–dealloying reactions, and the interior space allows the volume variation upon insertion–extraction of lithium ions to be better accommodated.

Nanocomposites of SnO2@ordered mesoporous carbon (OMC) as anode materials for lithium-ion batteries with improved electrochemical performance

We developed a facile infiltration chemical route to fabricate nanocomposites with SnO2 nanoparticle embedded ordered mesoporous carbon (SnO2@OMC) as anode materials for lithium-ion batteries application. The content of SnO2 in the composites can be optimized by changing the mass ratio of SnCl2·2H2O to OMC. The as-prepared materials were characterized by X-ray diffraction, N2 adsorption–desorption analysis techniques, field emission scanning electron microscopy, and high resolution transmission electron microscopy. Electrochemical performance results reveal that the SnO2@OMC composite containing 20 at% SnO2 displays an extraordinary reversible capacity up to 769 mA h g−1 and a high coulombic efficiency up to nearly 98.7% even after 60 cycles at a high current density of 100 mA g−1. Meanwhile, SnO2@OMC composite exhibits excellent rate capabilities. Even at a current rate as high as 1600 mA g−1, it still maintains a stable charge–discharge capacity of 440 mA h g−1 after 60 cycles. The outstanding electrochemical performance of the synthesized SnO2@OMC composites could be ascribed to its unique structural characteristics. The SnO2@OMC nanocomposites are promising candidates as anode materials for rechargeable lithium-ion batteries.

Hybrids of iron oxide/ordered mesoporous carbon as anode materials for high-capacity and high-rate capability lithium-ion batteries

A hybrid of iron oxide nanoparticle modified ordered mesoporous carbon (OMC) was successfully prepared via a controllable two-step route. Electrochemical lithium storage experimental results reveal that the FeOx/OMC composites can effectively reduce the capacity decay caused by volume change, and decrease the irreversible capacity of ordered mesoporous carbon. The first discharge capacities of FeOx/OMC and OMC are 1718 mA h g−1 and 1685 mA h g−1, respectively, while the first charge capacities of the FeOx/OMC and OMC electrodes are 1004 mA h g−1 and 528 mA h g−1, respectively. Apparently, the FeOx/OMC hybrids display a higher reversible capacity of more than 660 mA h g−1 and higher initial coulombic efficiency (58.4%). More importantly, at high charge–discharge rates, even at a current density of 1600 mA g−1, the capacity of the FeOx/OMC electrode is still maintained at 320 mA h g−1 even after 50 cycles, almost 5.4 times higher than the capacity of 50 mA h g−1 for the pure OMC sample. The high rate of performance is important for applications where fast charge and discharge are needed. The prominent improvement of electrochemical performance can be attributed to the synergistic effects of the FeOx/OMC composites. The FeOx nanoparticles can reduce the large amounts of active sites due to the high specific surface of the OMC, which results in a high irreversible capacity. While the OMC in the composite not only provides an elastic buffer space to accommodate the volume expansion/contraction of FeOx nanoparticles during the Li ions insertion/extraction process, but also efficiently prevents crumbling of electrode material upon continuous cycling, thus maintaining large capacity, good Coulombic efficiency, high rate capability and cycling stability. Furthermore, the OMC in the composite with good electrical conductivity can serve as the conductive channels between FeOx nanoparticles. This excellent electrochemical performance of the FeOx/OMC hybrid makes it a candidate anode material for commercial lithium-ion batteries.

TiO2 nanocrystal embedded ordered mesoporous carbons as anode materials for lithium-ion batteries with highly reversible capacity and rate performance

The ordered mesoporous carbon/TiO2 (OMCT) nanocomposites with TiO2 nanocrystals embedded within ordered mesoporous carbon (OMC) were prepared by a simple solvothermal method. The effect of TiO2 nanoparticle incorporation in OMC matrix on the mesoporous structure, pore size, pore volume, surface area and microstructure of OMCT composites was investigated using X-ray diffraction, N2 adsorption–desorption and Brunauer–Emmett–Teller method, scanning electron microscopy and transmission electron microscopy. The electrochemical lithium storage capacities of OMCT composites with different incorporated TiO2 nanoparticles are comparatively investigated using cyclic voltammetry and galvanostatic charge–discharge techniques. It is suggested that the OMCT composites as anode materials for lithium ion batteries display a greatly improved electrochemical performance with high reversible capacity, coulombic efficiency, rate capability and cycling performance. As an anode electrode for Li-ion battery, OMCT15 composite with an incorporated TiO2 nanocrystal content possesses a high reversible capacity of 540.9 mA h g−1 even up to 60 cycles at a high current density of 100 mA g−1, with a stable coulombic efficiency of 98% and good rate capability. Especially at the current density of 1600 mA g−1 after 50 cycles, the reversible capacity of the OMCT15 remains at a value of 260 mA h g−1, 5 times that of the OMC (48.9 mA h g−1) and 21 times that of the pure TiO2 (12.4 mA h g−1) electrodes, respectively. The improved electrochemical lithium storage performance of high reversible capacity, coulombic efficiency, rate performance and cycling ability can be mainly attributed to the synergic effects between the TiO2 nanoparticles and the three dimensional OMC matrices.