LiNi0.915Co0.075Al0.01O2 (NCA) with Zr(OH)4 coating is demonstrated as high performance cathode material for lithium ion batteries (LIBs). The coated materials are synthesized via a simple dry coating method of NCA with Zr(OH)4 powders, and then characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Experimental results show that amorphous Zr(OH)4 powders have been successfully coated on the surface of spherical NCA particles, exhibiting improved electrochemical performance. 0.50 wt% Zr(OH)4 coated NCA delivers a capacity of 197.6 mAh/g at the first cycle and 154.3 mAh/g after 100 cycles with a capacity retention of 78.1% at 1 C rate. In comparison, the pure NCA shows a capacity of 194.6 mAh/g at the first cycle and 142.5 mAh/g after 100 cycles with a capacity retention of 73.2% at 1 C rate. Electrochemical impedance spectroscopy (EIS) results show that the coated material exhibits a lower resistance, indicating that the coating layer can efficiently suppress transition metals dissolution and decrease the side reactions at the surface between the electrode and electrolyte. Therefore, surface coating with amorphous Zr(OH)4 is a simple and useful method to enhance the electrochemical performance of NCA-based materials for the cathode of LIBs.Download high-res image (92KB)Download full-size imageAmorphous Zr(OH)4 powders have been successfully coated on the surface of NCA and the coating layer can efficiently suppress the side reactions between the electrode and electrolyte during cycling, thus demonstrating excellent cycling stability.

Design and fabrication of stable and coordinated composite nanoarchitectures seem particularly essential for enhancing the catalytic activity and reusability of catalysts. Herein, we report the preparation of cobalt nanoparticles supported on nitrogen-doped porous carbon nanowires (Co/NPCNW) and their remarkable catalytic activity for the hydrolysis of ammonia borane (AB).

Molybdenum disulfide is popular for rechargeable batteries, especially in Li-ion batteries, because of its layered structure and relatively high specific capacity. In this paper, we report MoS2–C nanocomposites that are synthesized by a hydrothermal process, and their use as anode material for Li-ion batteries. Ascorbic acid is used as the carbon source, and the carbon contents can be tuned from 2.5 wt % to 16.2 wt %. With increasing of carbon content, the morphology of MoS2–C nanocomposites changes from nanoflowers to nanospheres, and the particle size is decreased from 200 to 60 nm. This change is caused by the chemical complex interaction of ascorbic acid. The MoS2–C nanocomposite with 8.4 wt % C features a high capacity of 970 mAh g–1 and sustains a capacity retention ratio of nearly 100% after 100 cycles. When the current increases to 1000 mA g–1, the capacity still reaches 730 mAh g–1. The above manifests that the carbon coating layer does not only accelerate the charge transfer kinetics to supply quick discharging and charging, but also hold the integrity of the electrode materials as evidenced by the long cycling stability. Therefore, MoS2-based nanocomposites could be used as commercial anode materials in Li-ion batteries.Keywords: anode; effect of carbon content; Li-ion batteries; MoS2; stability

We report on the preparation of three kinds of Ni nanoparticles supported on carbon (Ni/C) and their application in the catalytic hydrolysis of ammonia borane (AB). Three Ni/C catalysts were prepared from a Ni metal-organic framework (Ni-MOF) precursor by reduction with KBH4, calcination at 700 °C under Ar, and a combination of calcination and reduction, the products being denoted as Ni/C-1, Ni/C-2, and Ni/C-3, respectively. The structure, morphology, specific surface area, and element valence were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption measurements, and X-ray photoelectron spectra (XPS). The results demonstrate that Ni/C-1 is composed of amorphous Ni particles agglomerated on carbon, Ni/C-2 is characteristic of crystalline Ni nanoparticles (about 10 nm in size) supported on carbon with Ni oxidized on the surface, while the surface of the Ni particles in Ni/C-3 is less oxidized. The specific surface areas of Ni-MOF, Ni/C-1, Ni/C-2, and Ni/C-3 are 1239, 33, 470, and 451 m2·g−1, respectively. The catalytic hydrolysis of AB with Ni/C-3 shows a hydrogen generation rate of 834 mL·min−1·g−1 at room temperature and an activation energy of 31.6 kJ/mol. Ni/C-3 shows higher catalytic activity than other materials, which can be attributed to its larger surface area of crystalline Ni. This study offers a promising way to replace noble metal by Ni nanoparticles for AB hydrolysis under ambient conditions.

Organic tetralithium salts of 2,5-dihydroxyterephthalic acid (Li4C8H2O6) with the morphologies of bulk, nanoparticles, and nanosheets have been investigated as the active materials of either positive or negative electrode of rechargeable lithium-ion batteries. It is demonstrated that, in the electrolyte of LiPF6 dissolved in ethylene carbonate (EC) and dimethyl carbonate (DMC), reversible two-Li-ion electrochemical reactions are taking place with redox Li4C8H2O6/Li2C8H2O6 at ∼2.6 V for a positive electrode and Li4C8H2O6/Li6C8H2O6 at ∼0.8 V for a negative electrode, respectively. In the observed system, the electrochemical performance of high to low order is nanosheets > nanoparticles > bulk. Remarkably, Li4C8H2O6 nanosheets show the discharge capacities of 223 and 145 mAh g–1 at 0.1 and 5 C rates, respectively. A capacity retention of 95% is sustained after 50 cycles at 0.1 C rate charge/discharge and room temperature. Moreover, charging the symmetrical cells with Li4C8H2O6 nanosheets as the initial active materials of both positive and negative electrodes produces all-organic LIBs with an average operation voltage of 1.8 V and an energy density of about 130 Wh kg–1, enlightening the design and application of organic Li-reservoir compounds with nanostructures for all organic LIBs.

In this paper, we report on the preparation of Si–Y multi-layer thin films by magnetron sputtering and their application as anode materials of lithium-ion batteries. Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) and transmission electron microscopy (TEM) have been used to characterize the morphologies and structures of the as-prepared thin films. The framework of the Si–Y thin films is Y-Si-Y-Si multi-layers, including the Si thin film with a thickness of 225 nm and the Y thin film with different thickness (15–37.5 nm). The electrochemical performance of the samples is investigated by charge–discharge measurement, cyclic voltammetry and electrochemical impedance spectra (EIS). Compared with pure Si thin film, the Si–Y thin films with the optimal Y film thickness of about 22.5 nm can deliver a high reversible capacity of 2450 mAh g−1 under a current density of 0.4 C after 50 cycles, showing superior cycle performance and electrode stability due to the better Li+ diffusion character. This study should shed light on the design and application of Si–Y multi-layer thin films as anode materials of high-capacity lithium-ion batteries.Highlights► Si–Y multi-layer thin films have been prepared by radio frequency magnetron sputtering. ► The sample with the Y thin film of 22.5 nm shows excellent cycle performance. ► The Y thin film can act as a buffer layer to improve the Li-ion kinetic property.

In this paper, we report on the facile preparation of porous Li2FeSiO4/C nanocomposites by tartaric acid-assisted sol–gel method and their electrochemical properties as the cathode materials of Li-ion batteries. The structure, morphology, and texture of the as-prepared samples are characterized by means of XRD, Raman, SEM, TEM/HRTEM, and N2 adsorption/desorption techniques. The results show that the porous Li2FeSiO4/C nanocomposites are consisted of nanoparticles, which have been coated with in situ carbon on the surface. The electrochemical properties of the as-prepared Li2FeSiO4/C nanocomposites have been investigated using galvanostatic charge/discharge and cyclic voltammograms. It is found that porous Li2FeSiO4/C nanocomposite with 8.06 wt% carbon shows a high capacity of 176.8 mAh g−1 at 0.5 C in the first cycle and a reversible capacity of 132.1 mAh g−1 at 1 C (1 C = 160 mA g−1) in the 50th cycle. This high capacity indicates that more than one electron reaction may be occurred. These results illustrate that the porous Li2FeSiO4/C nanocomposite with 8.06 wt% carbon is potential in the application of high-rate cathode material of Li-ion batteries.Highlights► Porous Li2FeSiO4/C nanocomposites have been synthesized by a simple sol–gel method. ► The as-synthesized porous Li2FeSiO4/C nanocomposites exhibit enhanced electronic conductivity and Li+ diffusion coefficient as well as superior rate and cycling capabilities. ► The porous Li2FeSiO4/C nanocomposite with 8.06 wt% carbon delivers a high initial discharge capacity of 176.8 mAh g−1 at 0.5 C (1 C = 160 mA g−1) and a reversible capacity of 132.1 mAh g−1 in the 50th cycle at 1 C.

The SnO2@polypyrrole (PPy) nanocomposites have been synthesized by a one-pot oxidative chemical polymerization method. The structure, composition, and morphology of the as-prepared SnO2@PPy nanocomposites are characterized by XRD, FTIR, TG, SEM, and TEM. Electrochemical investigations show that the obtained SnO2@PPy nanocomposites exhibit high discharge/charge capacities and favorable cycling when they are employed as anode materials for rechargeable lithium-ion batteries. For the SnO2@PPy nanocomposite with 79 wt% SnO2, the electrode reaction kinetics is demonstrated to be controlled by the diffusion of Li+ ions in the nanocomposite. The calculated diffusion coefficiency of lithium ions in the SnO2@PPy nanocomposite with 79 wt% SnO2 is 6.7 × 10−8 cm2 s−1, while the lithium-alloying activation energy at 0.5 V is 47.3 kJ mol−1, which is obviously lower than that for the bare SnO2. The enhanced electrode performance with the SnO2@PPy nanocomposite is proposed to derive from the advantageous nanostructures that allow better structural flexibility, shorter diffusion length, and easier interaction with lithium.

We report on the carbon supported Ni core–Pt shell Ni1−x@Ptx/C (x = 0.32, 0.43, 0.60, 0.67, and 0.80) nanoparticles as catalysts for hydrogen generation from hydrolysis of ammonia borane (NH3BH3). The catalysts are prepared through a polyol synthesis process with oleic acid as the surfactant. The structure, morphology, and chemical composition of the obtained samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) equipped with energy dispersive X-ray (EDX), inductively coupled plasma emission spectroscopy (ICP), and nuclear magnetic resonance (NMR). The results show that the Ni core–Pt shell nanoparticles are uniformly dispersed on the carbon surface with the diameters of 2–4 nm, and furthermore, the catalysts show favorable performance toward the hydrolysis of NH3BH3. Among the nanoparticles, Ni0.33@Pt0.67/C displays the highest catalytic activity, delivering a high hydrogen release rate of 5469 mL min−1 g−1 and a low activation energy of 33.0 kJ mol−1.

Cobalt–phosphorus (Co–P) catalysts, which were electroless deposited on Cu sheet, have been investigated for hydrogen generation from alkaline NaBH4 solution. The microstructures of the as-prepared Co–P catalysts and their catalytic activities for hydrolysis of NaBH4 are analyzed in relation to pH value, NaH2PO2 concentration, and the deposition time. Experimental results show that the Co–P catalyst formed in the bath solution with pH value of 12.5, NaH2PO2 concentration of 0.8 M, and the deposition time no more than 6 min presents the highest hydrogen generation rate of 1846 mL min−1 g−1. Furthermore, the as-prepared catalyst also shows good cycling capability and the corresponding activation energy is calculated to be 48.1 kJ mol−1. The favorable catalytic performance of the electroless-deposited Co–P catalysts indicates their potential application for quick hydrogen generation from hydrolysis of NaBH4 solution.

We report the preparation of a series of LiNi0.8Co0.15Al0.05O2 materials with different reaction time (10, 20, 30 and 40 h) of precursor and their electrochemical properties as cathode material for lithium-ion batteries (LIBs). The preparation of LiNi0.8Co0.15Al0.05O2 was divided into two steps: a co-precipitation process to obtain Ni0.8Co0.15Al0.05(OH)2 precursor and a calcination step with LiOH. During the co-precipitation process, AlO2- was employed as Al source so as to guarantee Ni2+, Co2+ and Al3+ co-precipitation. The impacts of different synthesis time of the precursor on crystal structure, morphology and electrochemical performance of LiNi0.8Co0.15Al0.05O2 were systematically investigated. The samples with various synthesis time of precursor possessed spherical morphology and a layered α-NaFeO2 structure with R-3m space group. Especially, when the reaction time of precursor was 30 h, the LiNi0.8Co0.15Al0.05O2 had the weakest degree of Li+/Ni2+ ions mixing and the best uniformity and integrity. When used as cathode materials for LIBs, the LiNi0.8Co0.15Al0.05O2 with 30 h exhibited high discharge capacity, good cycling performance and remarkable rate capability. The maximum discharge capacity was 202.3 mAh g−1 at 0.1 C and the capacity retention approached 99.4% after 100 cycles at 1 C. At 10 C, the discharge capacity exceeded 140 mAh g−1, suggesting a possible application in the high rate LIBs. The excellent electrochemical performance might be attributed to the uniform co-precipitation of Ni2+, Co2+ and Al3+ and well layered structure with less Li+/Ni2+ mixing.