Papers by Keyword: Anode Materials

Abstract: Silicon materials are currently being explored for usage in lithium-ion battery anodes due to their high lithium storage capacity. We have developed a novel method, using a simple thermal treatment of low-cost silicon powder and nanographite, resulting in a composite where silicon nanoparticles are grown on the graphene surfaces. Electrodes fabricated from these Si-NG composites delivered a stable capacity of 489 mAh/g during 25 cycles, i.e. higher than conventional graphite anodes (theoretical capacity: 372 mAh/g). The method uses low-cost materials and avoids complex setups, thereby suggesting industrial scalability.

Abstract: Lithium ion battery is a kind of secondary battery that mainly relies on lithium ions moving between a positive electrode and a negative electrode. Lithium-ion batteries are considered to be the most ideal automotive power battery and has been widely applied in EV industry due to the outstanding advantages including but not limited to high energy density, high open circuit voltage and wide operating temperature range. The technical bottleneck of lithium-ion power batteries is how to further increase the energy density and optimize operating performance at low temperature. Besides, how to decrease the cost for lithium ion battery is also a big problem. The higher potential end of the power supply device is called cathode materials and the lower potential end of the power supply is called anode materials. At cathode end, Lithium ion intercalation process happens during discharging cycle and lithium ion deintercalation process happens during charging.For anode end, Lithium ion deintercalation process happens during charging cycle and lithium ion insertion process happens during discharging process. Good cathode/anode materials should include but not limited to the following characters: large specific capacity density, long cycling lifetime, good rate performance, proper electric potential and relatively stable structure during charge and discharge process.

Abstract: As a clean and efficient renewable energy, hydrogen energy will play an important role in the future energy system. The utilization of hydrogen energy involves various fields including production, application, storage and transportation, and the storage of hydrogen has become the main technical bottleneck restricting the wide application of hydrogen energy. Rare earth-based hydrogen storage alloys are promising hydrogen storage medium and have been widely used as anode materials for commercial Ni/MH batteries because of the excellent hydrogen storage and electrochemical properties. In this paper, the research progress of AB5 and R-Mg-Ni-based rare earth-based hydrogen storage alloys is described in detail. The alloy composition, preparation process, heat treatment and surface treatment process have significant influence on the comprehensive properties of rare earth-based hydrogen storage alloys. The effects of element substitution on the hydrogen storage capacity, corrosion resistance, oxidation resistance and electrochemical properties of the alloys are emphasized. This paper provides a guidance and a theoretical basis for the development and application of rare earth-based hydrogen storage materials.

Abstract: In this study, nitrogen-doped graphene (NrGO)/ titanium dioxide (B) (TiO₂(B))/ silicon composites were synthesized by dispersion method. Weight ratios of NrGO:TiO₂(B):Si were varied as 9:1:0, 8:2:0, 7:1:2 and 6:2:2. NrGO was prepared from graphite by the Modified Hummers method, followed by heat treatment under nitrogen atmosphere and N-added by annealing with melamine. TiO₂(B) was prepared by hydrothermal method and its phase was confirmed by X-Ray powder diffraction pattern (XRD), transmission electron microscopy (TEM) and electron diffraction pattern. Silicon was synthesized from bamboo leaves by combustion followed by magnesiothermic reduction process. The results from XRD could confirm components of the composites and the unchanged phase of TiO₂(B). From scanning electron microscopy (SEM) images of the composites, together with energy dispersive spectroscopy (EDS) data, silicon particles were distributed on the surface of NrGO, and TiO₂(B) nanorods which are between 0.5-5 µm in length were distributed on the surface and spaces between layers of NrGO, and NrGO/TiO₂ 8:2 had the most thoroughly distribution of particles.

Abstract: Si and Mg are good candidates for anode lithium-ion batteries because Si and Mg have high theoretical capacity of 4200 mAh g^-1 and 994 mAh g^-1, respectively. However, these elements generate high-volume expansion during the charge-discharge process, which can cause the electrode to crack after being used for a few cycles. To solve this problem, the active materials are prepared in a nanosize and composited with a 2D-sheet of nitrogen-doped graphene, as the high mechanical stability and flexibility of nitrogen-doped graphene can support the volume expansion. Preparation of Si-Mg and nitrogen-doped graphene includes two steps. First, the reduction of Mg²⁺ ions with NaBH₄ in ethylene glycol solution and reflux at 350 - 400 °C for 3 hr and Si nanoparticles, which were prepared by magnesiothermic reduction, was conducted. Second, Si and Mg nanoparticles and nitrogen-doped graphene were mixed in ethylene glycol solution and then collected by centrifugation. The obtained Si-Mg nanocomposite particles were well distributed on the nitrogen-doped graphene. The phases were indexed as Si, Mg and nitrogen-doped graphene. The particle sizes were small (approx 21 - 56 nm) with good dispersion on the nitrogen-doped graphene which observed by transmission electron microscopy and scanning electron microscopy techniques. Energy dispersive spectrometry results confirmed the existence of Si-Mg. Therefore, Si-Mg and nitrogen-doped graphene nanocomposite materials are expected to contain promising properties that can be used as high-performance anode materials in lithium-ion batteries in the future.

Abstract: Spinel Li₄Ti₅O₁₂ (LTO) doped with Mg²⁺ was synthesized by solid-phase reaction method. The Mg²⁺ doping quantity was 3%, 6%, 9%, and 12%, respectively. The structure and electrochemical performance of the prepared LTO composites were investigated by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and galvanostatic charge-discharge tests. It was found that the doped Mg ion did not change the structure of Li₄Ti₅O₁₂, and it was evenly distributed around Li₄Ti₅O₁₂. When Mg²⁺ doping quantity increased from 3% to 12%, the internal resistance and charge transfer resistance of the composite both decreased. The first discharge specific capacity of 6%-Mg²⁺ doped LTO composite was 168 mAh/g, which was close to the theoretical capacity of pure lithium titanate (175 mAh/g), and the capacity retention rate was 98% after 100 cycles.

Abstract: A superior self-assemble whiskery ZnFe₂O₄ has been synthesized by a facile coprecipitation method in the presence of oxalic acid. After performed as anode for lithium ion battery, the ZnFe₂O₄ exhibits excellent electrochemical performance with an initial discharge capacity of 1364.6 mAh g^-1, maintained an effective discharge capacity of 1086.9 mAh g^-1 after 50 cycles and wonderful rate capacity (687.4 mAh g^-1 at 3.0C). The excellent electrochemical performance was related to the novel whiskery structure, which is made of small spherical nanoparticles and hundreds of voids.

Abstract: The iron oxide anode materials have attracted widespread attention in lithium-ion battery research field. The Fe₂O₃/C composite was synthesized via hydrothermal method and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The XRD confirmed that the main crystallization phases of materials were Fe₂O₃. The Fe₂O₃/AC powders showed very uniform cube between 1 and 2 μm. Fe₂O₃/CNTs composites acted as a three-dimensional network wiring to connect Fe₂O₃ spheres. The electrochemical investigation indicated that the electrochemical performance of Fe₂O₃/CNTs materials shows a high specific capacity and an excellent cycling stability. The first reversible capacity of samples is 808.8 mAhg^-1 at the current density of 100 mAg^-1 between 0.01 and 2.5 V vs. Li/Li⁺.

Abstract: Dopamine was used as the carbon precursor to prepare SiO/C composite. Dopamine achieved self-polymerization and covered on the surface of the SiO particles in Tris-buffer, and the SiO/C composites were gained after heat-treating in the tube furnace under Argon. X-ray diffraction ( XRD ) , scanning electron microscope ( SEM ) were used to determine the phases obtained and to observe the morphologies of the composite. The galvanostatic discharge/charge test was carried out to characterize the electrochemical properties of the composite. When the sample of the mixed SiO and dopamine at a weight ratio of 1 : 3, the composite showed the best cycle ability with the discharge capacity of 1362 mAh g⁻¹ in the first cycle, and the initial coulombic efficiency is 55.6%, after 50 cycles, the discharge capacity is 442 mAh g⁻¹. The improved stability of the composite is attributed to carbon-coating forming during heat-treatment process.

Abstract: As lithium-ion battery anode materials, silicon has the highest specific capacity. In order to restrain pure silicon’s serious volume change and enhance its electrochemical performance, Si/SiO₂ composites were prepared by using a convenient high energy ball-milling technique. The characteristics of the composites as anode material for rechargeable lithium-ion batteries were investigated by X-ray diffraction and scanning electron microscopy methods. The electrochemical performance of the anode material was studied, and it was found the composite anode had a high capacity of 1333 mAhg^-1 in the first cycle and 400 mAhg^-1 could still be obtained after 46 cycles. Such prepared materials displayed improved cycle life.