Quan Kuang

Lithium deintercalation behavior in Li-rich vanadium phosphate as a potential cathode for Li-ion batteries

Layered Li-rich vanadium phosphate, Li9V3(P2O7)3(PO4)2, is a novel and potential cathode material for lithium-ion batteries. It possesses both facile ion mobility due to its two-dimensional pathways, and high theoretical capacity (173.5 mAh g−1) because of its ability to extract six lithium ions (per formula) from the trigonal framework accompanied with the double-electron reaction of vanadium. In this study, we first correlate the structural characters with the electrochemical process by using a combined experimental and computational method. The electrochemical recrystallization of Li9V3(P2O7)3(PO4)2 is accomplished along with a metastable superstructure phase in different but related space group. Nevertheless, the structure as well as oxidation state can be easily recovered on reduction-oxidation, and the volume change is minimal. Furthermore, the electrochemical voltage-composition profile is predicted and understood as emerging from site energetics and redox couples via first-principles calculations.

Crystal structure and electrochemical properties of LiFe 1− x Zn x PO 4 ( x ≤ 1.0)

A series of LiFe 1− x Zn x PO 4 (0.0 ≤ x ≤ 1.0) compounds were prepared by solid-state reaction. Effects of the substitution of Zn for Fe on crystal structure and electrochemical properties of LiFe 1− x Zn x PO 4 were investigated. The results show that single-phase regions of LiFe 1− x Zn x PO 4 with orthorhombic (space group Pmna ) and monoclinic ( Cc ) structures were found for the compounds with low Zn (or high Fe) contents of 0.0 ≤ x ≤ 0.30 and high Zn (or low Fe) contents of 0.90 ≤ x ≤ 1.0, respectively. The LiFe 1− x Zn x PO 4 compounds with medium Zn (or Fe) contents of 0.35 ≤ x ≤ 0.80 are two-phase mixtures containing both the orthorhombic and the monoclinic phases. Systematic variations of unit-cell parameters a , b , c , and volume V with the Zn content determined by X-ray diffraction have also been obtained. Our electrochemical study show that the conductivity of LiFe 1− x Zn x PO 4 increases by almost 2 orders of magnitude from 2.13 × 10 −9 to 1.27 × 10 −7 Scm −1 as the Zn content increasing from x = 0 to 0.3. The initial specific capacity decreases and the cycle performance increase with increasing Zn-doping content in the four orthorhombic LiFe 1− x Zn x PO 4 compounds. Among the four LiFe 1− x Zn x PO 4 compounds, LiFe 0.8 Zn 0.2 PO 4 has the highest capacity retentions after 6 to 20 cycles and the capacity retention is 93.7% after 20 cycles, even though the initial discharge specific capacity of LiFe 0.8 Zn 0.2 PO 4 is lower than those of LiFeZnPO 4 and LiFe 0.9 Zn 0.1 PO 4 . LiFe 0.7 Zn 0.3 PO 4 has the highest capacity retention of 97% after 20 cycles.

Cheese-like bulk carbon with nanoholes prepared from egg white as an anode material for lithium and sodium ion batteries

Cheese-like bulk carbon with nanoholes has been successfully fabricated from egg white via a simple annealing method by using distilled water as a green clean “corrosive agent”. X-ray diffractions and SEM images show the decomposition product of boiled egg white after annealing is bulk carbon, containing NaCl and KCl with a trace amount of nitrogen doping. After ultrasonic washing and centrifugation, the distilled water removed the NaCl and KCl nanocrystals from the bulk carbon completely and retained empty spaces, which eventually leads to the formation of a cheese-like structured bulk carbon with nanoholes. Our electrochemical tests show this cheese-like bulk carbon with nanoholes has a high specific capacity and good cycling performance and rate stability when evaluated as an anode material for lithium-ion batteries. Meanwhile, the electrochemical performances as an anode material for a sodium-ion battery are also displayed for comparison.

Single-crystalline LaxNd1−xB6 nanowires: synthesis, characterization and field emission performance

We report the catalyst-free synthesis of uniform distributed single-crystalline LaxNd1−xB6 nanowires by simply heating mixed La and Nd powders to the required temperature in an inlet flux of mixed gases (H2, Ar and BCl3). FE-SEM, HRTEM, SAED, EDS, element mapping, XRD and Raman scattering results show that the LaxNd1−xB6 nanowires are structurally uniform and well-doped single crystals. Based on our experimental results, a dominant VLS-like mechanism with a self-catalytic growth mechanism was proposed and depicted conceptually. The nanowires display an excellent field emission performance with a low turn-on field value of ∼4.12 V μm−1 when evaluated as an electron emitter. Attempts were also made to understand the morphological influence of reaction time, reaction temperature and the proportion of the La and Nd powders.

Synthesis and structural data of a Fe-base sodium metaphosphate compound,NaFe(PO3)3

This data article contains the synthesis and structure information of a new Fe-base sodium metaphosphate compound, which is related to the research article entitled ‘Synthesis, structural, magnetic and sodium deinsertion/insertion properties of a sodium ferrous metaphosphate, NaFe(PO3)3’ by Lin et al. [1]. The research article has reported a new Fe-base metaphosphate compound NaFe(PO3)3, which is discovered during the exploration of the new potential electrode materials for sodium-ion batteries. In this data article, the synthesized process of this metaphosphate compound and the morphology of the obtained sample will be provided. The high-power XRD Rietveld refinement is applied to determine the crystal structure of this metaphosphate compound and the refinement result including the main refinement parameters, atomic coordinate and some important lattace parameters are stored in the cif file. Also, the refined structure has be evaluated by checkcif report and the result is also provided as the supplementary materials.

Superstructure ZrV2O7 nanofibres: thermal expansion, electronic and lithium storage properties

ZrV2O7 has attracted much attention as a negative thermal expansion (NTE) material due to its isotropic negative structure. However, rarely has investigation of the lithium storage behaviors been carried out except our first report on it. Meanwhile, the electrochemical behaviors and energy storage characteristics have not been studied in depth and will be explored in this article. Herein, we report on the synthesis, characterization and lithium intercalation mechanism of superstructure ZrV2O7 nanofibres that were prepared through a facile solution-based method with a subsequent annealing process. The thermal in situ XRD technique combined with the Rietveld refinement method is adopted to analyze the change in the temperature-dependent crystal structure. Benefiting from the nanostructured morphology and relatively high electronic conductivity, it presents acceptable cyclic stability and rate capability. According to the operando evolution of the XRD patterns obtained from electrochemical in situ measurements, the Li intercalation mechanism of the solid solution process with a subsequent conversion reaction can be concluded. Finally, the amorphous state of the electrodes after the initial fully discharged state can effectively enhance the electrochemical performances.