Preparation of double-shell Si@SnO_(2)@C nanocomposite as anode for lithium-ion batteries by hydrothermal method

Silicon is one of the most promising anode materials for lithium-ion batteries(LIBs), but it suffers from pulverization and hence poor cycling stability due to the large volume variation during lithiation/delithiation. The core-shell structure is considered as an effective strategy to solve the expansion problem of silicon-based anodes. In this paper, the double-shell structured Si@SnO_(2) @C nanocomposite with nano-silicon as the core and SnO_(2) , C as the shells is synthesized by a facile hydrothermal method.Structural characterization shows that Si@SnO_(2) @C nanocomposite is composed of crystalline Si, crystalline SnO_(2) and amorphous C, and the contents of them are 42.1wt%, 37.8 wt% and 20.1 wt%, respectively. Transmission electron microscope(TEM) observations confirm the double-shell structure of Si@SnO_(2) @C nanocomposite, and the thicknesses of the SnO_(2) and C layers are 20 and 7 nm. The Si@SnO_(2) @C electrode exhibits a high initial discharge capacity of 2777 mAh·g^(-1)at 100 mA·g^(-1)and an excellent rate capability of 340 mAh·g^(-1)at 1500 mA·g^(-1). The outstanding capacity retention is 50.2% after 300 cycles over a potential of 0.01 to 2.00 V(vs. Li/Li+) at 500 mA·g^(-1). The resistance of solid electrolyte interphase(SEI) film(Rf) and charge transfer resistance(Rct) of Si@SnO_(2) @C are 7.68and 0.82 Ω, which are relatively smaller than those of Si@C(21.64 and 2.62 Ω). It is obviously seen that the SnO_(2) shell can reduce the charge transfer resistance, leading to high ion and electron transport efficiency in the Si@SnO_(2) @C electrode. The incorporation of SnO_(2) shell is attributed to the enhanced rate capability and cycling performance of Si@SnO_(2) @C nanocomposite.

Hydrothermal synthesis and characterization of nano-petal nickel hydroxide

The current article reports a preparation method of nano-petal nickel hydroxide, which was synthesized using urea as a precipitator by hydrothermal method. Nickel hydroxide samples with different microstructural characteristics were prepared by changing molar ratio of nickel/urea and reaction time. The prepared nickel hydroxide samples were characterized using X-ray diffraction(XRD) and scanning electron micrography(SEM).Electrochemical performances of the samples were then determined under charging–discharging rate of 0.2C. The influences of different conditions of the hydrothermal synthesis method on microstructure parameters of nickel hydroxide were analyzed, while relationships between microstructural characteristics parameters of nickel hydroxide and the electrochemical performances of nickel electrode were also explored.

Synthesis and electrochemical properties of Mn-substituted high-capacity nickel hydroxide

Nickel hydroxide is widely used as cathode materials in nickel-metal secondary batteries.In this work,Mn-substituted nickel hydroxide samples with a special α/βmixed phase structure were synthesized by chemical co-precipitation method.The physical properties were char-acterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),differential scanning calorimetry(DSC)and field emission scanning electron microscopy(FE-SEM).The results show that the structure of the samples and the amount of intercalated anions and water molecules are highly related to the content of the Mn substituted.Their electrochemical performances were characterized by charge/discharge tests and electrochemi-cal cycle tests.The results demonstrate that the Mn-sub-stituted samples with a α/β mixed phase structure perform a much higher discharge capacity than normal β-nickel hydroxide.The specific discharge capacity reaches 330 mAh·g^(-1) after 50 cycles of charge/discharge in charging rate of 0.2C under ambient temperature.Mean-while,the samples show no capacity loss in electrochem-ical cycles,which indicates that the mixed phase nickel hydroxide maintains high structure stability.