Controllable synthesis of nano-sized LiFePO 4 /C via a high shear mixer facilitated hydrothermal method for high rate Li-ion batteries

Zirconium‑cerium modified polyvinyl alcohol/NaCMC biocomposite film: Synthesis of films through high-speed shear assisted technique and removal fluoride from water

A new zirconium and cerium-modified polyvinyl alcohol (PVA) sodium carboxymethyl cellulose (NaCMC) film (PVA/CMC-Zr-Ce) was synthesized thru a high-speed shear-assisted method and its adsorption for the removal of fluoride was studied, in which the NaCMC provided -COONa for ion exchange between Na and Zr-Ce, thus the loading amount of Zr-Ce on films was accordingly increased. The morphology and structure of PVA/CMC-Zr-Ce were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Besides, the mechanical properties, water contact angle, and swelling ratio of film were also evaluated. The addition of high-speed shear improved the dispersion of the emulsion system, and PVA/CMC-Zr-Ce film with good adsorption performance and film stability was prepared. While, it was found that the adsorption capacity could reach 67.25 mg/g and equilibrium time could reach 20 min. The adsorption mechanism of PVA/CMC-Zr-Ce revealed that ion exchange between hydroxide and fluoride, electrostatic interactions and complexation were the dominating influencing factors. Based on these findings, it can be concluded that PVA/CMC-Zr-Ce film- synthesized with high-speed shear assistance technique is a promising adsorbent for fluoride removal from water.

Controlled Hydrothermal/Solvothermal Synthesis of High-Performance LiFePO4 for Li-Ion Batteries

The sluggish Li-ion diffusivity in LiFePO₄ , a famous cathode material, relies heavily on the employment of a broad spectrum of modifications to accelerate the slow kinetics, including size and orientation control, coating with electron-conducting layer, aliovalent ion doping, and defect control. These strategies are generally implemented by employing the hydrothermal/solvothermal synthesis, as reflected by the hundreds of publications on hydrothermal/solvothermal synthesis in recent years. However, LiFePO₄ is far from the level of controllable preparation, due to the lack of the understanding of the relations between the synthesis condition and the nucleation-and-growth of LiFePO₄ . In this paper, the recent progress in controlled hydrothermal/solvothermal synthesis of LiFePO₄ is first summarized, before an insight into the relations between the synthesis condition and the nucleation-and-growth of LiFePO₄ is obtained. Thereafter, a review over surface decoration, lattice substitution, and defect control is provided. Moreover, new research directions and future trends are also discussed.

Biosynthesis of vivianite from microbial extracellular electron transfer and environmental application

Vivianite (Fe₃(PO₄)₂·8H₂O) is a common hydrous ferrous phosphate mineral which often occurs in reductive conditions, especially anoxic non-sulfide environment containing high concentrations of ferrous iron (Fe²⁺) and orthophosphate (PO₄^3-). Vivianite is an important product of dissimilatory iron reduction and a promising route for phosphorus recovery from wastewater. Its formation is closely related to the extracellular electron transfer (EET), a key mechanism for microbial respiration and a crucial explanation for the reduction of metal oxides in soil and sediments. Despite of the natural ubiquity, easy accessibility and attractive economic value, the application value of vivianite has not received much attention. This review introduces the characteristics, occurrence and biosynthesis of vivianite from microbial EET, and systematically analyzes the application value of vivianite in the environmental field, including immobilization of heavy metals (HMs), dechlorination of carbon tetrachloride (CT), sedimentary phosphorus sequestration and eutrophication alleviation. Additionally, its potential functions as a slow-release fertilizer are discussed as well. In general, vivianite is expected to make more contributions to the future scientific research, especially the solution of environmental problems. Overcoming the lack of understanding and some technical limitations will be beneficial to the further application of vivianite in environmental field.

Effects of high-shear mixing and the graphene oxide weight fraction on the electrochemical properties of the GO/Ni(OH)2 electrode

High-shear mixing can efficiently enhance the homogeneity and the electrochemical performances of the GO/Ni(OH)₂ composite.

Hydraulic shear-induced rapid mass production of CsPbBr3/Cs4PbBr6 perovskite composites

Pure green CsPbBr₃/Cs₄PbBr₆ perovskite composites were synthesized by generating hydraulic shear as a rapid mass synthesis strategy.

Enhanced cycling performance of nanostructure LiFePO4/C composites with in situ 3D conductive networks for high power Li-ion batteries

In this work, reduced nano-sized LiFePO4 precursor particles were fabricated via a green chemistry approach without the use of any organic solvent or surfactants by accelerating the feeding speed of ferrous sulfate. After carbon coating, a 4 nm thick high graphitic degree carbon layer was deposited uniformly on the surface of reduced nano-sized LiFePO4 particles and constructed in situ 3D conductive networks among the adjacent LiFePO4 particles, as a result of an elevated self-catalytic effect of the reduced nano-size LiFePO4 particles that promoted the formation of the conductive networks. The reduced nano-size LiFePO4/C particles with in situ 3D conductive networks were shown to have an excellent high rate discharge capacity and long cycle life, delivering a high initial reversible discharge capacity of 163 mA h g-1 at 0.2C and an even high rate discharge capacity of 104 mA h g-1 at 30C. Additionally, a capacity of 101.7 mA h g-1 with a capacity retention of 97% remained after 850 cycles at 30C. This work suggests that the enhanced electrochemical performance of the LiFePO4/C composite was improved via the combination of the reduced nano-sized and 3D conductive networks, facilitating the electron transfer efficiency and diffusion of lithium ions, especially over an extended cycling performance at a high rate.

Controllable synthesis of (NH4)Fe2(PO4)2(OH)·2H2O using two-step route: Ultrasonic-intensified impinging stream pre-treatment followed by hydrothermal treatment

(NH₄)Fe₂(PO₄)₂(OH)·2H₂O samples with different morphology are successfully synthesized via two-step synthesis route - ultrasonic-intensified impinging stream pre-treatment followed by hydrothermal treatment (UIHT) method. The effects of the adoption of ultrasonic-intensified impinging stream pre-treatment, reagent concentration (C), pH value of solution and hydrothermal reaction time (T) on the physical and chemical properties of the synthesised (NH₄)Fe₂(PO₄)₂(OH)·2H₂O composites and FePO₄ particles were systematically investigated. Nano-seeds were firstly synthesized using the ultrasonic-intensified T-mixer and these nano-seeds were then transferred into a hydrothermal reactor, heated at 170 °C for 4 h. The obtained samples were characterized by utilising XRD, BET, TG-DTA, SEM, TEM, Mastersizer 3000 and FTIR, respectively. The experimental results have indicated that the particle size and morphology of the obtained samples are remarkably affected by the use of ultrasonic-intensified impinging stream pre-treatment, hydrothermal reaction time, reagent concentration, and pH value of solution. When such (NH₄)Fe₂(PO₄)₂(OH)·2H₂O precursor samples were transformed to FePO₄ products after sintering at 650 °C for 10 h, the SEM images have clearly shown that both the precursor and the final product still retain their monodispersed spherical microstructures with similar particle size of about 3 μm when the samples are synthesised at the optimised condition.

Crystal growth kinetics, microstructure and electrochemical properties of LiFePO4/carbon nanocomposites fabricated using a chelating structure phosphorus source

LiFePO4/carbon (LFP/C) nanocomposites were fabricated using bis(hexamethylene triamine penta (methylene phosphonic acid)) (BHMTPMPA) as a new and environment-friendly phosphorus source. The activation energy of the fabricated LFP/C was first investigated in depth based on the theoretical Arrhenius equation and experimental results of the LFP/C composite particle size distribution to explore the grain growth dynamics of the LFP/C particles during the sintering process. The results indicate that the activation energy is lower than 3.82 kJ mol-1 when the sintering temperature is within the range of 600-800 °C, which suggests that the crystal growth kinetics of the LFP/C particles is diffusion-controlled. The diffusion-controlled mechanism results from the mutual effects of chelation with Fe2+ cations, in situ formation of carbon layers and high concentration of hard aggregates due to the use of an organic phosphorous source (BHMTPMPA). The diffusion-controlled mechanism of the LFP/C effectively reduces the LFP particle size and hinders the growth of anomalous crystals, which may further result in nanosized LFP particles and good electrochemical performances. SEM and TEM analyses show that the prepared LFP/C has a uniform particle size of about 300 nm, which further confirms the effects of the diffusion-controlled mechanism of the LFP/C particle crystal growth kinetics. Electrochemical tests also verify the significant influence of the diffusion-controlled mechanism. The electrical conductivity and Li-ion diffusion coefficient (D Li +) of the fabricated LFP/C nanocomposite are 1.56 × 10-1 S cm-1 and 6.24 × 10-11 cm2 s-1, respectively, due to the chelating structure of the phosphorus source. The fabricated LFP/C nanocomposite exhibits a high reversible capacity of 166.9 mA h g-1 at 0.2C rate, and presents an excellent rate capacity of 134.8 mA h g-1 at 10C.

Optimization of lithium content in LiFePO4 for superior electrochemical performance: the role of impurities

Carbon coated Li_xFePO₄ samples with systematically varying Li-content (x = 1, 1.02, 1.05, 1.10) have been synthesized via a sol–gel route. The Li : Fe ratios for the as-synthesized samples is found to vary from ∼0.96 : 1 to 1.16 : 1 as determined by the proton induced gamma emission (PIGE) technique (for Li) and ICP-OES (for Fe). According to Mössbauer spectroscopy, sample Li_1.05FePO₄ has the highest content (i.e., ∼91.5%) of the actual electroactive phase (viz., crystalline LiFePO₄), followed by samples Li_1.02FePO₄, Li_1.1FePO₄ and LiFePO₄; with the remaining content being primarily Fe-containing impurities, including a conducting FeP phase in samples Li_1.02FePO₄ and Li_1.05FePO₄. Electrodes based on sample Li_1.05FePO₄ show the best electrochemical performance in all aspects, retaining ∼150 mA h g⁻¹ after 100 charge/discharge cycles at C/2, followed by sample Li_1.02FePO₄ (∼140 mA h g⁻¹), LiFePO₄ (∼120 mA h g⁻¹) and Li_1.10FePO₄ (∼115 mA h g⁻¹). Furthermore, the electrodes based on sample Li_1.05FePO₄ retain ∼107 mA h g⁻¹ even at a high current density of 5C. Impedance spectra indicate that electrodes based on sample Li_1.05FePO₄ possess the least charge transfer resistance, plausibly having influence from the compositional aspects. This low charge transfer resistance is partially responsible for the superior electrochemical behavior of that specific composition.

Extensive information regarding the Li : Fe stoichiometry in the LiFePO₄ cathode and the formation of concomitant impurities and their impact on the various electrochemical performances have been reported.

Non-stoichiometric carbon-coated LiFexPO4as cathode materials for high-performance Li-ion batteries

This work first discloses the evolution of lattice parameters of the non-stoichiometric lithium iron phosphate crystals.

Phosphorus recovery as ferrous phosphate (vivianite) from wastewater produced in manufacture of thin film transistor-liquid crystal displays (TFT-LCD) by a fluidized bed crystallizer (FBC)

In this investigation, fluidized bed crystallization (FBC) is utilized to treat phosphorus wastewater that is produced by the manufacture of thin film transistor-liquid crystal displays (TFT-LCD).

Boron and Nitrogen Codoped Carbon Layers of LiFePO4 Improve the High-Rate Electrochemical Performance for Lithium Ion Batteries

An evolutionary composite of LiFePO4 with nitrogen and boron codoped carbon layers was prepared by processing hydrothermal-synthesized LiFePO4. This novel codoping method is successfully applied to LiFePO4 for commercial use, and it achieved excellent electrochemical performance. The electrochemical performance can be improved through single nitrogen doping (LiFePO4/C-N) or boron doping (LiFePO4/C-B). When modifying the LiFePO4/C-B with nitrogen (to synthesis LiFePO4/C-B+N) the undesired nonconducting N-B configurations (190.1 and 397.9 eV) are generated. This decreases the electronic conductivity from 2.56×10(-2) to 1.30×10(-2) S cm(-1) resulting in weak electrochemical performance. Nevertheless, using the opposite order to decorate LiFePO4/C-N with boron (to obtain LiFePO4/C-N+B) not only eliminates the nonconducting N-B impurity, but also promotes the conductive C-N (398.3, 400.3, and 401.1 eV) and C-B (189.5 eV) configurations-this markedly improves the electronic conductivity to 1.36×10(-1) S cm(-1). Meanwhile the positive doping strategy leads to synergistic electrochemical activity distinctly compared with single N- or B-doped materials (even much better than their sum capacity at 20 C). Moreover, due to the electron and hole-type carriers donated by nitrogen and boron atoms, the N+B codoped carbon coating tremendously enhances the electrochemical property: at the rate of 20 C, the codoped sample can elevate the discharge capacity of LFP/C from 101.1 mAh g(-1) to 121.6 mAh g(-1), and the codoped product based on commercial LiFePO4/C shows a discharge capacity of 78.4 mAh g(-1) rather than 48.1 mAh g(-1). Nevertheless, the B+N codoped sample decreases the discharge capacity of LFP/C from 101.1 mAh g(-1) to 95.4 mAh g(-1), while the commercial LFP/C changes from 48.1 mAh g(-1) to 40.6 mAh g(-1).

Mixed ionic liquid/organic carbonate electrolytes for LiNi0.8Co0.15Al0.05O2 electrodes at various temperatures

At various temperatuers, different IL ratios in mixed electrolytes should be adopted to optimize cell relaibility and charge–discharge performance.