FTIR features of lithium-iron phosphates as electrode materials for rechargeable lithium batteries

Advanced Characterization Methodology to Unravel the Biodegradability of Metal-Organic Framework Nanoparticles in Extremely Diluted Conditions

Porous iron(III) carboxylate metal-organic frameworks (MIL-100; MIL stands for Material of Institute Lavoisier) of submicronic size (nanoMOFs) have attracted a growing interest in the field of drug delivery due to their high drug payloads, excellent entrapment efficiencies, biodegradable character, and poor toxicity. However, only a few studies have dealt with the nanoMOF degradation mechanism, which is key to their biological applications. Complementary methods have been used here to investigate the degradation mechanism of Fe-based nanoMOFs under neutral or acidic conditions and in the presence of albumin. High-resolution STEM-HAADF coupled with energy-dispersive X-ray spectroscopy enabled the monitoring of the crystalline organization and elemental distribution during degradation. NanoMOFs were also deposited onto silicon substrates by dip-coating, forming stable thin films of high optical quality. The mean film thickness and structural changes were further monitored by IR ellipsometry, approaching the "sink conditions" occurring in vivo. This approach is essential for the successful design of biocompatible nano-vectors under extreme diluted conditions. It was revealed that while the presence of a protein coating layer did not impede the degradation process, the pH of the medium in contact with the nanoMOFs played a major role. The degradation of nanoMOFs occurred to a larger extent under neutral conditions, rapidly and homogeneously within the crystalline matrices, and was associated with the departure of their constitutive organic ligand. Remarkably, the nanoMOFs' particles maintained their global morphology during degradation.

Simultaneous removal of nitrate nitrogen and orthophosphate by electroreduction and electrochemical precipitation

Electrochemical methods can effectively remove nitrate nitrogen (NO3-N) and orthophosphate phosphorus (PO4-P) from wastewater. This work proposed a process for the simultaneous removal of NO3-N and PO4-P by combining electroreduction with electrochemically-induced calcium phosphate precipitation, and its performance and mechanisms were studied. For the treatment of 100 mg L-1 NO3-N and 5 mg L-1 PO4-P, NO3-N removal of 60-90% (per cathode area: 0.25-0.38 mg h-1 cm-2) and 80-90% (per cathode area: 0.33-0.38 mg h-1 cm-2) could be acquired within 3 h in single-chamber cell (SCC) and dual-chamber cell (DCC), while P removal was 80-98% (per cathode area: 0.10-0.12 mg h-1 cm-2) in SCC after 30 min and 98% (per cathode area: 0.37 mg h-1 cm-2) in DCC within 10 min. The faster P removal in DCC was due to the higher pH and more abundant Ca2+ in the cathode chamber of DCC, which was caused by the cation exchange membrane (CEM). Interestingly, NO3-N reduction enhanced P removal because more OH- can be produced by nitrate reduction than hydrogen evolution for an equal-charge reaction. For 10 mg L-1 PO4-P in SCC, when the initial NO3-N was 0, 20, 100, and 500 mg L-1, the P removal efficiencies after 1 h treatment were < 10%, 45-55%, 86-99%, and above 98% respectively. An increase in Ca2+ concentration also promoted P removal. However, Ca and P inhibited nitrate reduction in SCC at the relatively low initial Ca/P, as CaP on the cathode limited the charge or mass transfer process. The removal efficiency of NO3-N in SCC after 3 h reaction can reduce by about 17%, 40%, and 34% for Co3O4/Ti, Co/Ti, and TiO2/Ti. The degree of inhibition of P on NO3-N removal was related to the content and composition of CaP deposited on the cathode. On the cathode, the lower the deposited Ca and P, and the higher the deposited Ca/P molar ratio, the weaker the inhibition of P on NO3-N removal. Especially, P had little or even no inhibition on nitrate reduction when treated in DCC instead of SCC or under high initial Ca/P. It is speculated that under these conditions, a high local pH and local high concentration Ca2+ layer near the cathode led to a decrease in CaP deposition and an increase in Ca/P molar ratio on the cathode. High initial concentrations of NO3-N might also be beneficial in reducing the inhibition of P on nitrate reduction, as few CaP with high Ca/P molar ratios were deposited on the cathode. The evaluation of the real wastewater treatment was also conducted.

Synthesis, characterization and thermoluminescence properties of LiCaPO4 phosphor for ionizing radiation dosimetry

Many minerals and compounds show thermoluminescence (TL) properties but only a few of them can meet the requirements of an ideal dosimeter. Several phosphate materials have been studied for low-dose dosimetryin recent times. Among the various phosphates, ABPO4-type material shows interesting TL properties. In this study, an ABPO4-type (A = Lithium, B=Calcium) phosphor is synthesized using a modified solid-state diffusion method. Temperature is maintained below 800 °C in every step of phosphor preparation to obtain the pure phase of Lithium calcium phosphate (LiCaPO4). The purpose of this work is to synthesize LiCaPO4 using a simple method, examine its structural and luminescence properties in order to gain a deeper understanding of its TL characteristics. The general TL properties, such as TL glow curve, dose linearity, sensitivity, and fading, are investigated. Additionally, this study aims to determine various kinetic parameters through Glow Curve Deconvolution (GCD) method using the Origin Lab software together with the Chen model. XRD analysis confirmed the phase purity of the phosphor with a rhombohedral structure. Lattice parameters, unit cell volume, grain size, dislocated density, and microstrain were also calculated from XRD data. Raman analysis and Fourier Transform Infrared analysis were used to collect information about molecular bonds, vibrations, identity, and structure of the phosphor. To investigate TL properties and associated kinetic parameters, the phosphor was irradiated with 6.0 MV (photon energy) and 6.0 MeV (electron energy) from a linear accelerator for doses ranging from 0.5 Gy to 6.0 Gy. For both photon and electron energy, TL glow curves have two identical peaks near 200 °C and 240 °C.The TL glow curves for 0.5 Gy-6 Gy are deconvoluted, then fitted with the appropriate model and then calculated the kinetic parameters. Kinetic parameters such as geometric factor (μg), order of kinetics, activation energy (E), and frequency factor (s) are obtained from Chen's peak shape method. The dose against the TL intensity curve shows that the response is almost linear in the investigated dose range. For photon and electron energy, the phosphor is found to be the most sensitive at 2.0 Gy and 4.0 Gy, respectively. The phosphor shows a low fading and after 28 days of exposure, it shows a signal loss of better than 3%. The studied TL properties suggest the suitability of LiCaPO4 in radiation dosimetry and associated fields.

Tunable electronic structure of heterosite FePO4: an in-depth structural study and polaron transport

The development of better electrode materials for lithium-ion batteries has been intensively investigated both due to their fundamental scientific aspects as well as their usefulness in technological applications. The present technological development of rechargeable batteries is hindered by fundamental challenges, such as low energy and power density, short lifespan, and sluggish charge transport kinetics. Among the various anode materials proposed, heterosite FePO₄ (h-FP) has been found to intercalate lithium and sodium ion hosts to obtain novel rechargeable batteries. The h-FP has been obtained via the delithiation of triphylite LiFePO₄ (LFP), and its structural and electronic properties have been investigated with different crystallite sizes. The synchrotron XRD measurements followed by Rietveld refinement analysis reveal lattice expansion upon the reduction of crystallite size of h-FP. In addition, the decrease in the crystallite size enhances surface energy contributions, thereby creating more oxygen vacancies up to 2% for 21 nm crystallite size. The expansion in the lattice parameters is reflected in the vibrational properties of the h-FP structure, where the red-shift has been observed in the characteristic modes upon the reduction of crystallite size. The local environment of the transition metal ion and its bonding characteristics have been elucidated through soft X-ray absorption spectroscopy (XAS) with the effect of crystallite size. XAS unequivocally reveals the valence state of iron 3d electrons near the Fermi level, which is susceptible to local lattice distortion and uncovers the detailed information on the evolution of electronic states with crystallite size. The observed local lattice distortion has been considered to be as a result of the decrease in the level of covalency between the Fe-3d and O-2p states. Further, we demonstrate the structural advantages of nanosized h-FP on the transport properties, where an enhancement in the polaronic conductivity with decreasing crystallite size has been observed. The polaronic conduction mechanism has been analyzed and discussed on the basis of the Mott model of polaron conduction along with an insightful analysis on the role of the electronic structure. The present study provides spectroscopic results on the anode material that reveal the evolution of electronic states for fingerprinting, understanding, and optimizing it for advanced rechargeable battery operations.

Structure and Magnetic Properties of AO and LiFePO4/C Composites by Sol-Gel Combustion Method

LiFePO₄ takes advantage of structure stability, safety and environmental friendliness, and has been favored by the majority of scientific researchers. In order to further improve the properties of LiFePO₄, AO-type metal oxides (MgO and ZnO) and LiFePO₄/C composites were successfully prepared by a two-step sol-gel method. The effects of AO-type metal oxides (MgO and ZnO) on LiFePO₄/C composites were studied. TG, XRD, FTIR, SEM and VSM analysis showed that the final product of the MgO and LiFePO₄/C composite was about 70.5% of the total mass of the precursor; the complete main diffraction peak of LiFePO₄ and MgO can be found without obvious impurity at the diffraction peak; there is good micro granularity and dispersion; the particle size is mainly 300 nm; the saturation magnetization (Ms), the residual magnetization (Mr) and the area of hysteresis loop are increased with the increase in MgO content; and the maximum Ms is 11.11 emu/g. The final product of ZnO and LiFePO₄/C composites is about 69% of the total mass of precursors; the complete main diffraction peak of LiFePO₄ and ZnO can be found without obvious impurity at the diffraction peak; there is good micro granularity and dispersion; the particle size is mainly 400 nm; and the coercivity (Hc) first slightly increases and then gradually decreases with the increase of zinc oxide.

A sustainable closed-loop method of selective oxidation leaching and regeneration for lithium iron phosphate cathode materials from spent batteries

A sustainable closed-loop method for recovering waste lithium iron phosphate batteries is developed in this paper. Li⁺ was selectively leached from cathode materials in a system of NaHSO₄ and H₂O₂. Under the optimal conditions of leaching temperature of 65 °C, 1.1 times molar quantity NaHSO₄, 2 vol% H₂O₂, solid-liquid ratio of 100 g/L and leaching time of 15 min, the leaching efficiency of Li can reach 99.84%, while Fe is only 0.048%. Meanwhile, XRD, FTIR, XPS and TEM analysis were carried out to explore the conversion mechanism in the oxidation leaching process of the original raw and leaching products. Li⁺ in the filtrate was precipitated with Na₂CO₃ and converted into Li₂CO₃. The precipitated salty wastewater can be converted into leaching agent for recycling by adding a certain amount of sulfuric acid. The recycled products are used to synthesize LiFePO₄ materials, and regenerated LiFePO₄ materials show good electrochemical properties. The discharge capacity displays 141.3 mAhg^-1 at 1C, with the capacity retention rate of 99.4% after 200 cycles. This study provides a sustainable closed-loop process for recycling and reuse of waste LiFePO₄ batteries, which promotes resource conservation and environmental protection.

New Cathode Materials in the Fe-PO4 -F Chemical Space for High-Performance Sodium-Ion Storage

Sodium and iron make up the perfect combination for the growing demand for sustainable energy storage systems, given the natural abundance and sustainability of the two building block elements. However, most sodium-iron electrode chemistries are plagued by intrinsic low energy densities with continuous ongoing efforts to solve this. Herein, the chemical space of a series of (meta)stable, off-stoichiometric Fe-PO4 -F phases is analyzed. Some are found to display markedly improved electrochemical activity for sodium storage, as compared to the amorphous or thermodynamically stable phases of equivalent composition. The metastable crystalline Na1.2 Fe1.2 PO4 F0.6 delivers a reversible capacity of more than 140 mAh g-1 with an average discharge potential of 2.9 V (vs Na+ /Na0 ) resulting in a practical specific energy density of 400 Wh kg-1 (estimated at the material level), outperforming many developed Fe-PO4 analogs thus far, with further multiple possibilities to be explored toward improved energy storage metrics. Overall, this study unlocks the possibilities of off-stoichiometric Fe-PO4 -F cathode materials and reveals the importance to explore the oft-overlooked metastable or transient state materials for energy storage.

Effect of Corrosive Media on the Chemical and Mechanical Resistance of IPS e.max® CAD Based Li2Si2O5 Glass-Ceramics

The influence of 4% acetic acid (pH~2.4) and an alkaline solution of NaOH (pH~10) on the corrosion resistance and micromechanical properties of disilicate crystals containing glass-ceramics (LS2-GC's) is studied. Partially crystallized lithium metasilicate crystal containing glass-ceramics (LS-GC's) are annealed to fully LS2-GC's using a one stage and a two-stage heating to induce nucleation. Materials with various chemical and wear resistance are prepared. The content of the crystalline phase in the material annealed in the two-stage process A is 60.0% and increases to 72.2% for the material heated in the one-stage process B. The main elements leached in the acidic medium are lithium and phosphorus, while lithium, silicon, and phosphorus leached into the alkaline environment. Material B exhibits better chemical resistance to the corrosive influence of 4% acetic acid under quasi-dynamic conditions. In the alkaline corrosion medium, silicon is leached from material A faster compared to the material B. After prolonged exposure to acidic or basic environments, both materials show evidence of surface structural changes. A decrease of the sliding wear resistance is observed after corrosion in the acidic environment under dynamic conditions. In both materials, the wear rate increases after corrosion.

Development of Injectable Hydroxyapatite/2-(dimethylamino)Ethyl Methacrylate/Polyvinylpyrrolidone Aqua-Hydrogel System to Repair of the Shoulder Joint Head for Hemiarthroplasty

This study aimed to develop osteogenic structure assembly for modular bone treatment presentations, effect of 2-(dimethylamino)ethyl methacrylate and polyvinyl pyrrolidone combination as cell adhesive molecule with hydroxyapatite-based composite as osteoconductive constituent was inspected on bone fracture repair. The prepared injectable composite hydrogel showed significantly improved mechanical stability. The ternary composite gel was characterized for functional group modifications and chemical interactions using Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Moreover, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses were performed to observe surface appearances of the hydrogel. The hydroxyapatite/2-(dimethylamino)ethyl methacrylate/poly-N-vinyl-2-pyrrolidone hydrogel played key role in supporting osteoblastic cell spread due to their bioactivity and strength abilities. The present findings revealed the significance of hydroxyapatite concentration on proliferation and osteogenic purpose of the cells. The developed performances of hydrogel have been improved cell proliferation and functions to repair bone fracture.

Structural and Spectroscopic Studies of NaCuCr2(PO4)3: A Noncentrosymmetric Phosphate Belonging to the α-CrPO4-Type Compounds

An electron and joint neutron and X-ray diffraction study of the synthetic copper/chromium phosphate NaCuCr₂(PO₄)₃ (NaCuP) is reported. A noncentrosymmetric Imm2 space group belonging to the well-known α-CrPO₄ type is observed contrary to what is reported in NaMCr₂(PO₄)₃ (M = Co and Ni) phosphates. The structural model is validated by bond valence sum analysis and charge-distribution (CHARDI) calculations and supported by complementary infrared and Raman spectroscopy investigations. Both Raman spectroscopy and theoretical study by deformation density approach further suggest the presence of Cu²⁺ (3d⁹) and Cr²⁺ (3d⁴) Jahn-Teller polaron effects as a key factor to the centro Imma to noncentrosymmetric Imm2 phase change.

Enhancing LiAlOX synaptic performance by reducing the Schottky barrier height for deep neural network applications

Although good performance has been reported in shallow neural networks, the application of memristor synapses towards realistic deep neural networks has met more stringent requirements on the synapse properties, particularly the high precision and linearity of the synaptic analog weight tuning. In this study, a LiAlOX memristor synapse was fabricated and optimized to address these demands. By delicately tuning the initial conductance states, 120-level continuously adjustable conductance states were obtained and the nonlinearity factor was substantially reduced from 8.96 to 0.83. The significant enhancements were attributed to the reduced Schottky barrier height (SBH) between the filament tip and the electrode, which was estimated from the measured I-V curves. Furthermore, a deep neural network for realistic action recognition task was constructed, and the recognition accuracy was found to be increased from 15.1% to 91.4% on the Weizmann video dataset by adopting the above-described device optimization method.

Synthesis and Characterization of LiFePO4-PANI Hybrid Material as Cathode for Lithium-Ion Batteries

This work focuses on the synthesis of LiFePO₄-PANI hybrid materials and studies their electrochemical properties (capacity, cyclability and rate capability) for use in lithium ion batteries. PANI synthesis and optimization was carried out by chemical oxidation (self-assembly process), using ammonium persulfate (APS) and H₃PO₄, obtaining a material with a high degree of crystallinity. For the synthesis of the LiFePO₄-PANI hybrid, a thermal treatment of LiFePO₄ particles was carried out in a furnace with polyaniline (PANI) and lithium acetate (AcOLi)-coated particles, using Ar/H₂ atmosphere. The pristine and synthetized powders were characterized by XRD, SEM, IR and TGA. The electrochemical characterizations were carried out by using CV, EIS and galvanostatic methods, obtaining a capacity of 95 mAhg^-1 for PANI, 120 mAhg^-1 for LiFePO₄ and 145 mAhg^-1 for LiFePO₄-PANI, at a charge/discharge rate of 0.1 C. At a charge/discharge rate of 2 C, the capacities were 70 mAhg^-1 for LiFePO₄ and 100 mAhg^-1 for LiFePO₄-PANI, showing that the PANI also had a favorable effect on the rate capability.

Lyotropic Liquid Crystalline Mesophases Made of Salt-Acid-Surfactant Systems for the Synthesis of Novel Mesoporous Lithium Metal Phosphates

Mesoporous lithium metal phosphates are an important class of materials for the development of lithium ion batteries. However, there is a limited success in producing mesoporous lithium metal phosphates in the literature. Here, a lyotropic liquid crystalline (LLC) templating method was employed to synthesize the first examples of LiMPO₄ (LMP) of Mn(II), Co(II), and Ni(II). A homogeneous aqueous solution of lithium and transition metal nitrate salts, phosphoric acid (PA), and surfactant (P123) can be spin coated or drop-cast coated over glass slides to form the LLC mesophases which can be calcined into mesoporous amorphous LMPs (MA-LMPs). The metal salts of Mn(II), Co(II) and Ni(II) produce MA-LMPs that crystallize into olivine structures by heat treatment of the LLC mesophase. The Fe(II) compound undergoes air oxidation. Therefore, both Fe(II) and Fe(III) precursors produce a crystalline Li₃ Fe₂ (PO₄ )₃ phase at over 400 °C. The MA-LMPs show no reactivity towards lithium, however the crystalline iron compound exhibits electrochemical reactivity with lithium and a good electrochemical energy storage ability using a lithium-ion battery test.

Composites with alginate beads: A novel design of nano-adsorbents impregnation for large-scale continuous flow wastewater treatment pilots

The sorption capacity of cadmium (Cd (II)) on three new generated nanocomposite beads sodium alginate (SA) based; SA-Clay (SA-C) beads, SA-Phosphate (SA-P) beads, and SA- Activated Charcoal (SA-Ch) beads was investigated in a batch scale, then a continuous flow reactor.

The highest adsorption capacity (137 mg/g) was obtained for SA-Ch using 1000 mg/L of initial Cd (II). The isotherm results showed that the adsorption equilibrium is compatible with the Langmuir isotherm and the sorption capacity of SA-Nano-adsorbent beads is very high. The models used for representing kinetic data was given that the removal of Cd (II) be well-fitted by second-order reaction kinetics. For the fixed bed column treatment, the maximum breakthrough times were 30, 38, and 48  h respectively for the SA-C, SA-P, and SA-Ch.

According to the obtained results, it was concluded that SA-Nano-adsorbent bead is an excellent designed material as a nanocomposite for cadmium elimination from wastewater in a continuous treatment process.

Fluorolytic Sol-Gel Route and Electrochemical Properties of Polyanionic Transition-Metal Phosphate Fluorides

Fluorine-containing polyanionic compounds have attracted much attention in the last few years as potential positive electrode materials for rechargeable batteries. With their formula A_a M_b X_c O₄ Y_d (A=Li, Na…; M=Ti, V, Mn, Fe, Co, Ni…; X=P or S, and Y=F, OH, O), they offer a very rich chemistry and their electrochemical properties can be tuned by carefully choosing the different constituting elements. However, synthesis approaches that allow these materials to be obtained at low temperature are almost nonexistent. In this paper, the use of a nonaqueous fluorolytic sol-gel approach is reported to synthesize a tavorite-type LiFePO₄ F material and its electrochemical characterization was performed. The obtained material displays an electrochemical performance that positively compares with the literature with an excellent cycling stability (115 mA h^-1  g^-1 after 100 cycles at C/2 rate). A slight change in the synthesis parameters allowed Li₂ CoPO₄ F to be successfully obtained, demonstrating the versatility of the reported route, which can be adapted to synthesize other fluorine-containing polyanionic compounds, which are of great interest for energy storage applications.

Advanced Nanoclay-Based Nanocomposite Solid Polymer Electrolyte for Lithium Iron Phosphate Batteries

High-performance solid polymer electrolytes (SPEs) have long been desired for the next generation of lithium batteries. One of the most promising ways to improve the morphological and electrochemical properties of SPEs is the addition of fillers with specific nanostructures. However, the production of such fillers is generally expensive and requires complicated preparation procedures. Halloysite nanotubes (HNTs), with their tubular structure, resemble carbon nanotubes in terms of geometric features and can be obtained at a relatively low cost. Previously, we reported that the HNT poly(ethylene oxide) composite SPE possesses excellent electrochemical and mechanical properties and outstanding cycling performance for all-solid-state lithium sulfur batteries. However, the HNT/SPE was not effective for lithium iron phosphate (LFP) batteries. The compatibility between the electrodes and the electrolyte sharply decreased, and no decent cycling performance was achieved. Therefore, a modification was studied which involves a minor addition of LFP during the preparation procedure. With this modification, good ionic conductivity (9.23 × 10^-5 S cm^-1 at 25 °C) is achieved, and compatibility between the electrodes and the electrolyte is enhanced. At the same time, an electrochemical stability window of 5.14 V and lithium-ion transference number of 0.46 are found. All-solid-state LFP batteries possessing excellent cycling performance are further demonstrated.

High performance LiNi0.5Mn1.5O4 cathode material with a bi-functional coating for lithium ion batteries

LiPO₃/LiNi_0.5Mn_1.5O₄ exhibited superior cyclability and rate performance as a result of a bi-functional coating layer of LiPO₃.

Unlocking the energy capabilities of micron-sized LiFePO4

Utilization of LiFePO4 as a cathode material for Li-ion batteries often requires size nanonization coupled with calcination-based carbon coating to improve its electrochemical performance, which, however, is usually at the expense of tap density and may be environmentally problematic. Here we report the utilization of micron-sized LiFePO4, which has a higher tap density than its nano-sized siblings, by forming a conducting polymer coating on its surface with a greener diazonium chemistry. Specifically, micron-sized LiFePO4 particles have been uniformly coated with a thin polyphenylene film via the spontaneous reaction between LiFePO4 and an aromatic diazonium salt of benzenediazonium tetrafluoroborate. The coated micron-sized LiFePO4, compared with its pristine counterpart, has shown improved electrical conductivity, high rate capability and excellent cyclability when used as a 'carbon additive free' cathode material for rechargeable Li-ion batteries. The bonding mechanism of polyphenylene to LiFePO4/FePO4 has been understood with density functional theory calculations.

LiFePO4 nanoparticles growth with preferential (010) face modulated by Tween-80

Adding Tween-80 as surfactant in hydrothermal synthesis can successfully reduce grain size and adjust crystal orientation of LiFePO₄.

Supercritical synthesis in combination with a spray process for 3D porous microsphere lithium iron phosphate

Supercritical synthesis in combination with a spray process for 3D porous microspheres of lithium iron phosphate.

Morphological and orientational diversity of LiFePO4crystallites: remarkable reaction path dependence in hydrothermal/solvothermal syntheses

Reaction path difference in synthesis conditions has resulted in the morphological and orientational diversity of resultant LiFePO₄crystallites.