Dawei Song

Novel flower-like CoS hierarchitectures: one-pot synthesis and electrochemical properties

Novel 3D flower-like CoS hierarchitectures and CoS microspheres have been synthesized by a facile solvothermal method. A growth mechanism has been proposed for the nanostructures. Temperature and precursor concentration are the key factors influencing the nanostructures. Electrochemical measurements display high discharge capacity and excellent cycle stability.

LiCoO2: recycling from spent batteries and regeneration with solid state synthesis

A green recycling process was designed and used to recycle spent LiCoO2 batteries, and the recycled LiCoO2 was regenerated after the solid state synthesis with Li2CO3. XRD results showed that the layered structure of LiCoO2 was repaired after regeneration. The physical and chemical properties (XRD, morphology, tap density, average particle size, specific surface areas and pH value) and electrochemical properties (discharge capacity, attenuation rate of capacity, plateau retention at 3.6 V and attenuation rate of plateau) of LiCoO2 after regeneration were tested in detail and compared with commercial LiCoO2. The test data show that the regenerated LiCoO2 at 900 °C can meet the commercial requirements for reuse.

Crystalline TiB2: an efficient catalyst for synthesis and hydrogen desorption/absorption performances of NaAlH4 system

High hydrogen pressure and desorption/absorption temperature retard the practical applications of the NaAlH4 system. To ease these problems, we successfully synthesize a crystalline TiB2 catalyst to catalyze the synthesis of NaAlH4. The weight percentage of synthesized nanocrystalline NaAlH4 is as high as 89 wt%. More interestingly, a dramatically reduced of desorption/absorption temperature is achieved with the efficient TiB2 catalyst. Thermodynamic analyses show that the onset dehydrogenation temperature of TiB2–NaAlH4 mixture is lowered to about 70 °C, which is lower than the pristine system. The activation energy of TiB2–NaAlH4 mixture calculated by Arrhenius equation is only 56.28 kJ mol−1. In addition, as-prepared NaAlH4 can be recharged almost quantitatively under remarkably mild conditions (90 °C and 4 MPa hydrogen pressure). The improvement of hydrogen storage and release properties is considerably pronounced under low-pressure and low-temperature conditions. Moreover, preliminary research about the catalytic mechanism of TiB2 is also discussed.

Environmentally friendly recycling and effective repairing of cathode powders from spent LiFePO4 batteries

Extensive use of LiFePO4 batteries will afford a lot of spent LiFePO4 batteries, which cannot be recycled properly by using traditional processes at present. If these spent LiFePO4 batteries are thrown away without recycling properly, it is not only a severe waste of valuable resources, but also leads to serious environmental pollution. In this paper, a completely green recycling process and a small scale model line are developed to recycle cathode powders from spent LiFePO4 batteries for the first time. Parts of LiFePO4 host particles in spent LiFePO4 batteries decompose to FePO4, Fe2O3, P2O5 and Li3PO4 after numerous charge–discharge cycles, resulting in poor electrochemical performance of freshly recycled cathode powders for Li-ion batteries. To repair decomposed LiFePO4 host particles, recycled cathode powders are heat-treated at different temperatures. After heat-treatment at high temperatures, especially at 650 °C, cathode powders are effectively recycled and can be reused for Li-ion batteries.

Chainlike structures assembled by Co hierarchitectures: synthesis and electrochemical properties as negative materials for alkaline secondary batteries

Chainlike structures assembled by cobalt hierarchitectures have been selectively synthesized via facile hydrothermal and solvothermal routes and electrochemically investigated as the negative materials for alkaline secondary batteries. The obtained cobalt samples exhibit high discharge capacities, excellent cycle stabilities and favorable rate capabilities. Furthermore, with the introduction of sulfur, the electrochemical properties are greatly improved.

Effects of annealing on microstructures and electrochemical properties of La0.8Mg0.2Ni2.4Mn0.10Co0.55Al0.10 alloy

The La0.8Mg0.2Ni2.4Mn0.10Co0.55Al0.10 alloy was prepared by induction melting. The structural and morphological characterizations were performed by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical measurements were performed using LAND and CHI 660b electrochemical workstation. The main phases of the alloy were LaNi5 and (La,Mg)Ni3. After annealing, the maximum discharge capacity, cycle stability and high rate dischargeability (HRD) were improved obviously. The maximum discharge capacity reached 373.80 mAh/g (T=1173 K), the C100/Cmax(%) was 72.63% (T=1173 K), and the value of HRD reached 51.8% at a discharge current density of 1150 mA/g (T=1173 K). The cyclic voltammetry (CV) and potentiodynamic polarization were also studied.