O4 Hollow Microspheres Research Articles

Hierarchical Triple‐Shelled MnCo2O4 Hollow Microspheres as High‐Performance Anode Materials for Potassium‐Ion Batteries

Metal oxide anode materials generally possess high theoretical capacities. However, their further development in potassium-ion batteries (KIBs) is limited by self-aggregation and large volume fluctuations during charge/discharge processes. Herein, hierarchical MnCo2 O4 hollow microspheres (ts-MCO HSs) with three porous shells that consist of aggregated primary nanoparticles are fabricated as anode materials of KIBs. The porous shells are in favor of reducing the diffusion path of K-ions and electrons, and thus the rate performance can be enhanced. The unique triple-shelled hollow structure is believed to provide sufficient contact between electrolyte and metal oxides, possess additional active storage sites for K-ions, and buffer the volume change during K-ions insertion/extraction. A high specific capacity of 243mAhg-1 at 100mAg-1 in the 2nd cycle and a highly improved rate performance of 153mAhg-1 at 1Ag-1 are delivered when cycled between 0.01 and 3.0V. In addition, the transformation of substances during charging/discharging processes are intuitively demonstrated by the in situ X-ray diffraction strategy for the first time, which further proves that the unique structure of ts-MCO HSs with three porous shells can significantly enhance the potassium ions storage performance.

Excellent electrochemical performances of high-voltage LiNi0.5Mn1.5O4 hollow microspheres synthesized by a static co-precipitation method

High-voltage LiNi0.5Mn1.5O4 hollow microspheres are synthesized through a static co-precipitation method. The LiNi0.5Mn1.5O4 microspheres are composed of the spherical micron-sized particles with hollow core, and it has a cubic spinel structure with a space group of Fd3m. Electrochemical results demonstrate that the prepared LiNi0.5Mn1.5O4 exhibit excellent cycle stability and rate capability. The LiNi0.5Mn1.5O4 materials with hollow microsphere structure and excellent electrochemical properties are expected to be used in high energy density lithium-ion batteries.

Li4Ti5O12 epitaxial coating on LiNi0.5Mn1.5O4 surface for improving the electrochemical performance through solvothermal-assisted processing

During the charge-discharge of the LiNi0.5Mn1.5O4 (LNMO) cathode in Li-ion batteries, Ni2+ and Mn2+ dissolve in the electrolyte to cause oxidative decomposition, which is the major cause for fast capacity fading and poor cycle performance. Reducing the direct contact area between the cathode material and the electrolyte is a direct solution to improve the cell performance. This paper focuses on a solvothermal method to coat the surface of LiNi0.5Mn1.5O4 hollow microspheres with TiO2 followed by TiO2 conversion into Li4Ti5O12 (LTO) using LiOH·H2O. The Li4Ti5O12 coating layer synthesized by this method demonstrates epitaxial growth on the outer surface of LiNi0.5Mn1.5O4. The LTO-coated LNMO cathode exhibits capacity retention of 88.1% after 100 cycles at 0.5C rate, much higher than 62.2% for the bare LNMO counterpart, at elevated temperature of 55 °C. In addition, the Li+-ion mobility for the LTO-coated LNMO electrode is increased.

Electrochemical performance and electronic properties of shell LiNi0.5Mn1.5O4 hollow spheres for lithium ion battery

Shell spinel LiNi[Formula: see text]Mn[Formula: see text]O4 hollow microspheres were successfully synthesized by MnCO3 template, and characterized by XRD, SEM, and TEM. The results show that the hollow LiNi[Formula: see text]Mn[Formula: see text]O4 cathode has good cycle stability to reach 124.5, 119.8, and 96.6[Formula: see text]mAh/g at 0.5, 1, and 5 C, the corresponding retention rate of 98.1%, 98.2%, and 98.0% after 50 cycles at 20[Formula: see text]C, and the reversible capacity of 94.6[Formula: see text]mAh/g can be obtained at 1 C rate at 55[Formula: see text]C, 83.3% retention after 100 cycles. As the temperature decreases from 10[Formula: see text]C to [Formula: see text]C, the resistance of [Formula: see text] increases from 5.5 [Formula: see text] to 135 [Formula: see text], [Formula: see text] from 27 [Formula: see text] to 353.2 [Formula: see text], and [Formula: see text] from 12.7 [Formula: see text] to 73.0 [Formula: see text]. Moreover, the B constant and [Formula: see text] activation energy are 4480[Formula: see text]K and 37.22[Formula: see text]KJ/mol for the NTC spinel material, respectively.

Synthesis of shell-in-shell LiNi0.5Mn1.5O4 hollow microspheres and their enhanced performance for lithium ion batteries

Shell-in-shell LiNi0.5Mn1.5O4 hollow microspheres (SS-LNMO) were synthesized by a facile molten salt and temperature programmed calcination route. SS-LNMO with an average size of 1.2µm and a shell thicknesses of ~120nm were employed as cathode materials for lithium ion batteries. Experiment results showed that SS-LNMO exhibited a good rate performance. At 2C, the reversible capacity after 100 cycles was 140 mAhg−1 with a coulombic efficiency of 97.7%. The superior electrochemical behavior of SS-LNMO could be ascribed to the unique micro-nano assembly hollow structure, simultaneously offering short diffusion distance, cushioning the volume change and maintaining the electrode integrity.

High performance LiNi0.5Mn1.5O4 cathode by Al-coating and Al3+-doping through a physical vapor deposition method

In this work, spinel LiNi0.5Mn1.5O4 (LNMO) hollow microspheres are synthesized by an impregnation method using microsphere MnO2 as both the precursor and template. To enhance the electrical conductivity of LNMO, metal Al was employed for the first time as a coating material for LNMO. Though an Electron-beam Vapor Deposition approach, the surface of LNMO can be easily coated by a tight layer of Al nanoparticles with adjusted thickness. Further annealing the Al-coated sample at 800°C in air, the Al3+-doped LNMO can be obtained. The effects of Al-coating and Al3+-doping on the sample morphology and structure are investigated by SEM, TEM, XRD and FT-IR. The electrochemical properties of Al-coated LNMO and Al3+-doped LNMO are measured with comparison of bare LNMO by charge/discharge tests and electrochemical impedance spectroscopy (EIS). The results show that both Al-coating and Al3+-doping can greatly enhance the cycle performance and rate capability of LNMO. Especially for Al-coated LNMO, it shows the lowest battery impedance due to the existence of conductive Al coating layer, thus delivers the best rate performance among the three. The physical coating procedure used in this work may provide a new facile modification approach for other cathode materials.

Synergistic Ternary Composite (Carbon/Fe3 O4 @Graphene) with Hollow Microspherical and Robust Structure for Li-Ion Storage.

The electrode materials with hollow structure and/or graphene coating are expected to exhibit outstanding electrochemical performances in energy-storage systems. 2D graphene-wrapped hollow C/Fe3 O4 microspheres are rationally designed and fabricated by a novel facile and scalable strategy. The core@double-shell structure SPS@FeOOH@GO (SPS: sulfonated polystyrene, GO: graphene oxide) microspheres are first prepared through a simple one-pot approach and then transformed into C/Fe3 O4 @G (G: graphene) after calcination at 500 °C in Ar. During calcination, the Kirkendall effect resulting from the diffusion/reaction of SPS-derived carbon and FeOOH leads to the formation of hollow structure carbon with Fe3 O4 nanoparticles embedded in it. In the rationally constructed architecture of C/Fe3 O4 @G, the strongly coupled C/Fe3 O4 hollow microspheres are further anchored onto 2D graphene networks, achieving a strong synergetic effect between carbon, Fe3 O4 , and graphene. As an anode material of Li-ion batteries (LIBs), C/Fe3 O4 @G manifests a high reversible capacity, excellent rate behavior, and outstanding long-term cycling performance (1208 mAh g(-1) after 200 cycles at 100 mA g(-1) ).

Preparation and electrochemical performance of spinel LiNi0.5−x Mn1.5+x O4 (x = 0, 0.05, 0.1) hollow microspheres as cathode materials for lithium-ion batteries

The spinel LiNi0.5−x Mn1.5+x O4 (x = 0, 0.05, 0.1) including LiNi0.5Mn1.5O4, LiNi0.45Mn1.55O4, and LiNi0.4Mn1.6O4 hollow microspheres has been prepared by adjusting the stoichiometric ratios of Ni and Mn with an impregnation method followed by a simple solid-state reaction. They are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, high-resolution transmission electron microscope, X-ray photoelectron spectroscopy, and electrochemical tests. The results show that LiNi0.5Mn1.5O4 is the ordered with the space group of P4332, but LiNi0.45Mn1.55O4 and LiNi0.4Mn1.6O4 are the disordered with the space group of Fd3m. All the three types of hollow microspheres have the similar primary particles. Compared to LiNi0.5Mn1.5O4, partial Ni atoms are substituted by Mn atoms in LiNi0.45Mn1.55O4 and LiNi0.4Mn1.6O4 lattices along with incorporation of small amounts of Mn3+. Although the ordered LiNi0.5Mn1.5O4 hollow microspheres deliver the highest capacity of 128.5 mAh/g at 1 C among the three types of spinel materials, the disordered LiNi0.45Mn1.55O4 hollow microspheres exhibit the highest capacity of 96.8 mAh/g at 10 C. The superior rate capability of LiNi0.45Mn1.55O4 hollow microspheres is attributed to the combination of the increased electronic conductivity and Li+-ion diffusion by moderate Mn3+ incorporation, along with the hierarchical structure.

Synthesis of LiNi0.5Mn1.5O4 Hollow Microspheres and Their Lithium‐Storage Properties

AbstractHigh‐voltage LiNi0.5Mn1.5O4 hollow microspheres have been synthesized through a facile solid‐state method. X‐ray diffraction and scanning electron microscopy results reveal that the as‐prepared LiNi0.5Mn1.5O4 microspheres are constructed with nanometer‐sized primary particles. The effects of the precursors on the morphologies and electrochemical properties of LiNi0.5Mn1.5O4 materials are systematically investigated. Electrochemical test results demonstrate that the materials with large porosity and smaller second particles exhibit higher reversible capacity as well as better cycle stability and rate capacities. LiNi0.5Mn1.5O4 prepared from MnCO3 precursors delivers high reversible capacities of 135.5, 147.5, and 132.1 mAh g−1 at 0.1, 0.5, and 2 C, respectively. Even at a high rate of 5 C, the electrode retains 93.4 % of the initial capacity at 0.1 C. Moreover, the electrode shows excellent cycle stability with a discharge capacity of 110 mAh g−1 at 1 C after 80 cycles at elevated temperature. The extremely attractive electrochemical properties are closely related to the unique structure and chemistry of the synthesized material.

Facile synthesis of aluminum-doped LiNi0.5Mn1.5O4 hollow microspheres and their electrochemical performance for high-voltage Li-ion batteries

This paper presents the preparation of LiNi0.5Mn1.5O4 and aluminum (Al) doped LiNi0.5Mn1.5O4 hollow microspheres as 5V cathodes using monodisperse MnCO3 microspheres as precursor and template, which were synthesized using MnSO4·H2O, NaHCO3 and ethanol in water at room temperature. XRD and morphology characterization results indicated that the as-prepared LiNi0.5Mn1.5O4 and Al doped LiNi0.5Mn1.5O4 were both spinel structure, and have particle sizes of 2–3μm. The cathode electrochemical properties of LiNi0.5Mn1.5O4 and Al doped LiNi0.5Mn1.5O4 hollow microspheres (as 5V cathodes) were evaluated and compared by galvanostatic cycling (GC) vs. Li/Li+ at the current rate 1C in 2.7–4.8V. The specific initial capacities of all samples were in the range of 70–120mAhg−1. Compared to undoped LiNi0.5Mn1.5O4, Al doped LiNi0.5Mn1.5O4 hollow structures can effectively improve discharge capacity (up to 140 (±5)mAhg−1) and cycling stability (70% capacity retention after 200 cycles) as high voltage cathode materials.

Designed synthesis of LiNi0.5Mn1.5O4 hollow microspheres with superior electrochemical properties as high-voltage cathode materials for lithium-ion batteries

LiNi0.5Mn1.5O4 hollow microspheres with designed subunits as high-voltage cathode materials for lithium-ion batteries were synthesized using dense or hollow Mn2O3 porous-spheres as self-templates. Dense Mn2O3 porous-spheres with mesosized subunits (>100 nm) were prepared by the direct decomposition of microspherical MnCO3, while the hollow and porous Mn2O3 microspheres with nanosized subunits (<30 nm) were synthesized by temperature-controlled decomposition of Mn–Ca bicarbonates followed by the selective removal of carbonates with HCl. Through a solid state reaction between Li/Ni precursors with meso/nanoporous Mn2O3, LiNi0.5Mn1.5O4 hollow spheres with different cavity size and wall structure were prepared. The as-synthesized hollow microspheres exhibited superior cyclability and high-rate capability. The best sample delivered a high and reversible discharge capacity of around 130 mA h g−1 with a capacity retention efficiency of 98.6% after 60 cycles at 1 C rate. The sample also showed high reversible capacities of 100.5 mA h g−1 even at a high current rate of 5 C. As a comparison, LiNi0.5Mn1.5O4 powders were also produced by a conventional solid state process using ball-milled Li–Ni–Mn hydroxide-oxide precursors, which showed low capacities of around 110 mA h g−1 at 1 C and greatly degraded capacities at higher current rates.

Ordered LiNi0.5Mn1.5O4 hollow microspheres as high-rate 5 V cathode materials for lithium ion batteries

Ordered LiNi0.5Mn1.5O4 hollow microspheres have been synthesized by an impregnation method followed by a simple solid-state reaction, and their electrochemical performance is investigated as cathode material for lithium ion batteries. The morphologies of the LiNi0.5Mn1.5O4 products prepared at different temperatures reveal that the formation for the hollow structure is tightly relative to the temperature for the solid-state reaction. Then ordered LiNi0.5Mn1.5O4 hollow microspheres are formed under the solid-state reaction temperature of 800°C along with post-annealing at 700°C, but the sample prepared without post-annealing exists at the form of disordered structure. When the ordered LiNi0.5Mn1.5O4 hollow microspheres were applied as the cathode materials for lithium ion batteries, they exhibited superior rate capability (116 mAh g−1 at 5C, 85 mAh g−1 at 10C for charge and discharge) and good cyclability, which are much better than the disordered sample. The durable high-rate capability was attributed to their single-crystal surface configuration that benefits fast Li insertion/extraction kinetics.

Enhancing the Electrochemical Performance of the LiMn2O4 Hollow Microsphere Cathode with a LiNi0.5Mn1.5O4 Coated Layer

Spinel cathode materials consisting of LiMn2 O4 @LiNi0.5 Mn1.5 O4 hollow microspheres have been synthesized by a facile solution-phase coating and subsequent solid-phase lithiation route in an atmosphere of air. When used as the cathode of lithium-ion batteries, the double-shell LiMn2 O4 @LiNi0.5 Mn1.5 O4 hollow microspheres thus obtained show a high specific capacity of 120 mA h g(-1) at 1 C rate, and excellent rate capability (90 mAhg(-1) at 10 C) over the range of 3.5-5 V versus Li/Li(+) with a retention of 95 % over 500 cycles.

Uniform LiNi1/3Co1/3Mn1/3O2 hollow microspheres: Designed synthesis, topotactical structural transformation and their enhanced electrochemical performance

In this work, we designed a facile in-situ template-sacrificial route to prepare LiNi1/3Co1/3Mn1/3O2 hollow microspheres with an average diameter of 2.0μm for the first time through using porous spinel Mn1.5Co1.5O4 hollow microspheres as the template, the formation of which could originate from a synergic effect of the contraction and adhesion action generated during the oxidative decomposition of the Mn0.5Co0.5CO3 precursors. The walls of the as-prepared hollow microspheres are ~300nm in thickness, and composed of numerous primary particles with size of hundreds of nanometers. The as-synthesized nanocrystal-assembled hollow structure showed singnificantly enhanced electrochemical performance with high capacity, excellent cycling stability and good rate capability, compared with the bulk counterparts, when used as a cathode material for Li ion batteries (LIBs), which can be attributed to the unique nano/micro hierarchical structure. Specifically, the resulting LiNi1/3Co1/3Mn1/3O2 hollow microspheres achieve a high discharge capacity of 157.3mAhg−1 at 0.2C after 100 cycles and 120.5mAhg−1 at 0.5C after 200 cycles with an excellent cycle life. Interestingly, it exhibits a high rate capacity of 114.2mAhg−1 even at a current of 1Ag−1 (5C). On the basis of this work, the pesent preparation strategy could provide an effective and general approach to improve the cyclability and rate capability of high-capacity cathode materials with hollow interiors for the application of LIBs.

LiNi0.5Mn1.5O4 Hollow Structures as High‐Performance Cathodes for Lithium‐Ion Batteries

Built to last: Uniform LiNi0.5Mn1.5O4 hollow microspheres and microcubes (see picture; scale bars: 1 μm) with nanosized building blocks have been synthesized by a facile impregnation method followed by a simple solid-state reaction. The resultant LiNi0.5Mn1.5O4 hollow structures deliver a discharge capacity of about 120 mA h g−1 over prolonged cycling and exhibit excellent rate capability.