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Recently, Ni-rich LiNixCoyMn1−x−yO2 (x ≥ 0.8) draw significant research attention as cathode materials in lithium-ion batteries due to their superiority in energy density. However, the oxygen release and the transition metals (TMs) dissolution during the (dis)charging process lead to serious safety issues and capacity loss, which highly prevent its application. In this work, we systematically explored the stability of lattice oxygen and TM sites in LiNi0.8Co0.1Mn0.1O2(NCM811) cathode via investigating various vacancy formations during lithiation/delithiation, and properties such as the number of unpaired spins (NUS), net charges, and d band center were comprehensively studied. In the process of delithiation (x = 1 → 0.75 → 0), the vacancy formation energy of lattice oxygen [Evac(O)] has been identified to follow the order of Evac(O–Mn) > Evac(O–Co) > Evac(O–Ni), and Evac(TMs) shows a consistent trend with the sequence of Evac(Mn) > Evac(Co) > Evac(Ni), demonstrating the importance of Mn to stabilize the structural skeleton. Furthermore, the |NUS| and net charge are proved to be good descriptors for measuring Evac(O/TMs), which show linear correlations with Evac(O) and Evac(TMs), respectively. Li vacancy plays a pivotal role on Evac(O/TMs). Evac(O/TMs) at x = 0.75 vary extremely between the NiCoMnO layer (NCM layer) and the NiO layer (Ni layer), which correlates well with |NUS| and net charge in the NCM layer but aggregates in a small region in the Ni layer due to the effect of Li vacancies. In general, this work provides an in-depth understanding of the instability of lattice oxygen and transition metal sites on the (104) surface of Ni-rich NCM811, which might give new insights into oxygen release and transition metal dissolution in this system. [ABSTRACT FROM AUTHOR]

The floating zone technique is a popular method for crystal growth of nonconventional superconductors and magnetic materials. However, the quality must be characterized with particular care with respect to their actual crystallinity since not everything grown by floating zone method is a single crystal. In this paper, the molten‐zone sensitive material LiCoPO4 has been grown by the floating zone method using Co(NO3)2∙6H2O and CoO precursors, respectively, abbreviated as LCPN and LCPO. The grown materials are characterized regarding their chemical composition, phase purity, crystal perfection, and orientation. In order to optimize crystal growth and quantitatively characterize its crystallinity quality, the development factor (V) has been proposed to determine the growth rate of the grains, while the orientation deviation factor (δ) for assessing the quality of the grown crystals. The development factors V for LCPN and LCPO are calculated to be 0.05 and 0.09, respectively, indicating that the grains of LCPO develop faster than those of LCPN. At the same time, the orientation deviation factor of LCPO exceeds that of LCPN (δ(LCPO) = 2.00, δ(LCPN) = 0.77) suggesting a higher quality for the latter. This model provides significant guidance for the evaluation of other materials grown by the floating zone method. [ABSTRACT FROM AUTHOR]

Size and shape uniformity of nanomaterials are extremely important for their applications in batteries, supercapacitors, catalysis, etc. In the crystallization process, finding proper synthesis conditions is necessary to have control over size dispersion, as well as crystal planes. In this work, we synthesized Cu2O rhombic dodecahedra (exposing 12 {110} planes) with size range from 1351 nm to 142 nm at a reaction temperature of 31–60 °C. The main parameters governing the size of Cu2O were the concentration of the precursor species and reduction reaction, which were affected by a given temperature. Results of crystallization experiments indicated that reaction and crystallization kinetics were mainly enhanced by raised temperature. Serving as lithium ion battery anodes, Cu2O rhombic dodecahedra showed higher capacity than cubes and octahedra. This work gives us a way of optimizing the temperature conditions for obtaining size uniformity of nanomaterials. [ABSTRACT FROM AUTHOR]

MnCO3 precursors with different morphologies were crystallized using three kinds of surfactants as soft templates, i.e., cation surfactant cetyl trimethyl ammonium bromide (CTAB), anion surfactant sodium dodecyl sulfate (SDS) and neutral poly(vinyl pyrrolidone) (PVP). When PVP was used, the reaction manner was changed from only stirring at room temperature to a hydrothermal route. Under hydrothermal conditions, different ethanol/water ratios and sources of CO32− (NaHCO3 and urea) were used. Porous cubic, regular spherical and nut-like spherical Mn2O3 samples can be obtained by a simple post-annealing process. The correlation between the morphology of Mn2O3 and its performance as an anode material for Li-ion batteries was evaluated. The nut-like spherical Mn2O3 sample has the best cycling performance, with a specific discharge capacity of 925 mA h g−1 at a current density of 100 mA g−1 after 180 cycles. The sample composed of cubes and spheres has superior rate performance. The specific discharge capacity decreases with increasing current density from ~872 mA h g−1 at 100 mA g−1 to ~361 mA h g−1 at 2000 mA g−1. [ABSTRACT FROM AUTHOR]

Spinel cathode materials consisting of LiMn2O4@LiNi0.5Mn1.5O4 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 LiMn2O4@LiNi0.5Mn1.5O4 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. [ABSTRACT FROM AUTHOR]

Charged up: A general soft‐template route for the synthesis of uniform hollow carbon microspheres embedded with transition‐metal oxide nanocrystals (OHCMs) has been developed (see figure). The obtained OHCMs possess a microsized spherical shape, embedded transition‐metal oxide nanocrystals, and fully encapsulating conductive carbon shells, which endow the resulting anode materials with high specific capacities, rate capabilities, electrode densities, and cycle stabilities. [ABSTRACT FROM AUTHOR]

Abstract: Uniform single-crystalline SnS nanobelts have been prepared via a simple wet-chemical route, in which SnCl2 was used as tin source and Na2S as sulfur source. Direct conversion of these SnS nanobelts with two pyramidal tips to porous-walled SnO2 nanocapsules was achieved by oxidizing in atmospheric ambient at 500–700°C. The formation mechanism of these porous nanocapsules is a combination of non-equilibrium interdiffusion, volume loss, and gas release. With these uniform SnS nanobelts as precursors, carbon-coated metal Sn nanorods (Sn@C core-shell structure) were also synthesized by decomposition of sulfide SnS nanobelts with carbon coatings in N2 atmosphere. A strong UV emission peak at 365nm is demonstrated for the SnO2 porous nanocapsules, which makes these promising materials for applications such as optical sensors. Furthermore, energy storage performances of these Sn-based nanomaterials (porous SnO2 nanocapsules and Sn@C core-shell nanocomposites) as anodes for Li-ion batteries were investigated in detail. [Copyright &y& Elsevier]

Hollow nanostructured anode materials lie at the heart of research relating to Li-ion batteries, which require high capacity, high rate capability, and high safety. The higher capacity and higher rate capability for hollow nanostructured anode materials than that for the bulk counterparts can be attributed to their higher surface area, shorter path length for Li transport, and more freedom for volume change, which can reduce the overpotential and allow better reaction kinetics at the electrode surface. In this article, we review recent research activities on hollow nanostructured anode materials for Li-ion batteries, including carbon materials, metals, metal oxides, and their hybrid materials. The major goal of this review is to highlight some recent progresses in using these hollow nanomaterials as anode materials to develop Li-ion batteries with high capacity, high rate capability, and excellent cycling stability. [ABSTRACT FROM AUTHOR]

Nanoscale engineering of regular structured materials is immensely demanded in various scientific areas. In this work, vertically oriented TiO2 nanotube arrays were grown by self-organizing electrochemical anodization. The effects of different fluoride ion concentrations (0.2 and 0.5 wt% NH4F) and different anodization times (2, 5, 10 and 20 h) on the morphology of nanotubes were systematically studied in an organic electrolyte (glycol). The growth mechanisms of amorphous and anatase TiO2 nanotubes were also studied. Under optimized conditions, we obtained TiO2 nanotubes with tube diameters of 70–160 nm and tube lengths of 6.5–45 μm. Serving as free-standing and binder-free electrodes, the kinetic, capacity, and stability performances of TiO2 nanotubes were tested as lithium-ion battery anodes. This work provides a facile strategy for constructing self-organized materials with optimized functionalities for applications. [ABSTRACT FROM AUTHOR]

Uniform yolk–shell V2O5microspheres were synthesized viaa facile template-free solvothermal route and subsequent calcination treatment in air. The resulting cathode materials showed a high specific capacity of 220 mA h g−1after 30 cycles and good rate capability. [ABSTRACT FROM AUTHOR]

Co 3 O 4 has been extensively studied as an anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity. However, during the charging-discharging processes, the issues of large volume change and low electric conductivity arise, which significantly limit the practical applications of Co 3 O 4. To solve these issues, a Co 3 O 4 /CeO 2 heterostructure derived from metal-organic frameworks (MOFs) was designed and synthesized through one-step microwave synthesis. Benefiting from the mesoporous structure and presence of hetero-components, Co 3 O 4 /CeO 2 having the molar ratio of Co/Ce = 5:1 (denoted as 5Co 3 O 4 /CeO 2) exhibits high reversible capacity and excellent cycling stability when used as an anode material for LIBs. Specifically, compared to a single-phase Co 3 O 4 anode, which shows a capacity of 538.6 mAh/g after 100 cycles, 5Co 3 O 4 /CeO 2 exhibits a higher capacity (1131.2 mAh/g at 100 mA/g). This study provides a novel strategy for using rare earth components to modify electrode materials. [ABSTRACT FROM AUTHOR]

MnC 2 O 4 precursor was prepared by a precipitation method, and then porous MnO@C composites were obtained by mixing MnC 2 O 4 precursor with different amounts of glucose and sintering at different temperatures. The influences of carbon content and crystallinity on the electrochemical performance of MnO@C were investigated. Galvanostatic charge–discharge test results showed that the MnO@C sample “1.2,700” has the largest specific capacity among all samples, which can reach high specific discharge capacity of 1691 mAh g −1 at the current density of 100 mA g −1 after 200 cycles. Even at the high current density of 1600 mA g −1 , a remarkable discharge capacity of ∼630 mAh g −1 can still be delivered, demonstrating a good rate capability. The excellent electrochemical performance can be ascribed to porous structure, good crystallinity and proper amount of carbon coating. This facile method can be applied to the large-scale synthesis of high performance transition metal oxide@carbon composite electrode materials. [ABSTRACT FROM AUTHOR]

Orthorhombic LiMnO 2 (o-LiMnO 2 ) was prepared under hydrothermal conditions using sol–gel derived Mn 2 O 3 and LiOH as precursors and the effects of hydrothermal reaction parameters such as reaction temperature and LiOH and Mn 2 O 3 concentrations on the phase purity of o-LiMnO 2 were studied. The as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and galvanostatic charge−discharge tests. Phase purity of o-LiMnO 2 was affected by hydrothermal temperature and LiOH and Mn 2 O 3 concentrations. High LiOH concentration facilitated the synthesis of pure phase o-LiMnO 2 . Low reaction temperature, lower than 140 °C, did not lead to the formation of pure phase of o-LiMnO 2 . Galvanostatic charge–discharge test results showed that pure o-LiMnO 2 had larger discharge capacity than the mixed phases of o-LiMnO 2 and Li 2 MnO 3 . However, the cycling performance of the mixed phases of o-LiMnO 2 with Li 2 MnO 3 was found to be better than that of pure o-LiMnO 2 . [ABSTRACT FROM AUTHOR]

Amorphous FeOOH and α-FeOOH were synthesized by simple solvothermal methods and used as the reactants to prepare iron oxide-based cathode materials. Amorphous FeOOH transforms to α-Fe2O3 at temperatures as low as 80°C, and is stable enough to avoid the transformation to α-LiFeO2 even at 200°C in LiOH ethanol solution under solvothermal condition. α-FeOOH transforms to α-LiFeO2 in the same reaction system at 140°C. Both α-Fe2O3 and α-LiFeO2 demonstrate good electrochemical performances, especially α-Fe2O3, which delivers a high reversible capacity (105 mAh/g at 100mA/g after 50 cycles) in the voltage range from 1.5 to 4.5V. The electrochemical performances of α-Fe2O3 were found to be influenced by the solvent, temperature, reaction duration and alkali concentration of the solvothermal reactions. It was found that ethanol solution, low temperature, and moderate reaction duration and alkali concentration lead to α-Fe2O3 with reversible capacity of about 100 mAh/g. [ABSTRACT FROM AUTHOR]

Abstract: Fe-based materials, Fe2O3, Fe3O4, and FeOOH, were synthesized by the microwave–hydrothermal process in the temperature range of 100–200°C and under very short reaction times of 15min to 2h. Under microwave-controlled hydrolysis and redox reactions, cube-like Fe2O3 was crystallized using FeCl3, Fe3O4 particles were crystallized from FeCl2 and FeOOH nanorods were crystallized using FeCl3. The Fe-based materials were fabricated to make anodes and cathodes of lithium-ion battery and supercapacitor electrode materials to study their potential electrochemical applications. The electrochemical results showed that FeOOH had better anode capacity as lithium-ion batteries than those of Fe2O3 and Fe3O4. The present results suggest that the microwave–hydrothermally synthesized Fe-based materials are promising lithium-ion battery anode materials. [Copyright &y& Elsevier]

[Display omitted] • High performance electrode materials are the key for LIBs, aqueous batteries and SCs. • Electrochemical properties of iron oxides were determined based on structure and size. • Smallest hematite and akaganeite particles showed the highest capacitances. • Hematite and akaganeite showed similar charge and discharge for aqueous batteries. • Ferrihydrite of 5 nm size showed pseudocapacitive behavior for aqueous batteries. Electrode materials of high-performance are the key for lithium-ion and aqueous batteries, and supercapacitors. Although there are many studies about iron oxides as electrode materials, few or no studies focused on the dependence of electrochemical properties on both their structure and crystal size. Here, we focused on electrochemical properties of iron oxides of different structures such as hematite (α-Fe 2 O 3), akaganeite (β-FeOOH) and ferrihydrite with unique structure (Fe 2 O 3 ·2FeOOH·2.6H 2 O) and of different crystal sizes and morphologies. When used as anode materials for LIBs, hematites with nanosized crystals showed higher capacity than the hematites with micrometer crystals. Among the different crystal structures, both hematite and akaganeite outperformed ferrihydrite even though the latter has the smallest crystals. Both hematite and akaganeite electrode materials showed similar charge and discharge behaviors for aqueous batteries, while ferrihydrite showed pseudocapacitive behavior. Thus, both crystal size and structure of iron oxides are important in tailoring them for electrode materials. [ABSTRACT FROM AUTHOR]

NiO nanoparticles were synthesized by the calcination of two nickel precursors that prepared by mixing of NiCl 2 ·6H 2 O and salicylic acid (NiO-1) and benzoic acid (NiO-2) and characterized by FT-IR, UV–Vis, PL, XRD, SEM and TEM. The products have good electrochemical reversibility and also exhibit a large specific capacitance of about 479 and 388 mA h g−1 after 50 cycles at 100 mA g−1. The NiO nanoparticles electrodes exhibit excellent rate capability, nearly 37% and 40% specific capacity retention have been observed when the current density increases from 100 to 1000 mA g−1. NiO nanoparticles (NiO-1 and NiO-2) were synthesized by the calcination of NiCl 2 ·6H 2 O/benzoic acid and salicylic acid, respectively, with weight ratio 1:1 at temperature 600 °C. They were characterized by Fourier transform infrared (FT-IR), UV–Vis and photoluminecence spectroscopy, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Their electrochemical properties were evaluated using cyclic voltammetry, galvanostatic charge/discharge measurement and electrochemical impedance spectroscopy. The final products have good electrochemical reversibility and show large specific capacitance of about 479 mA h g−1 and 388 mA h g−1 after 50 cycles at 100 mA g−1. The NiO nanoparticles electrodes exhibit also excellent rate capability. Nearly 37% and 40% specific capacity retention were observed after the current density had increased from 100 to 1000 mA g−1. [ABSTRACT FROM AUTHOR]