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Despite the structural and electrochemical advantages of LiFePO4 (LFP) as a cathode material, the solid-state reaction commonly used as a method to produce it at the industrial level has known disadvantages associated with high energy and fossil fuel consumption. On the other hand, solution-based synthesis methods present a more efficient way to produce LFP and have advantages such as controlled crystal growth, homogeneous morphology, and better control of pollutant emissions because the reaction occurs within a closed system. From an environmental point of view, different impacts associated with each synthesis method have not been studied extensively. The use of less polluting precursors during synthesis, as well as efficient use of energy and water, can provide new insights into the advantages of each cathode material for more environmentally friendly batteries. In this work, a solvothermal method is compared to a solid-state synthesis method commonly used to elaborate LFPs at the commercial level in order to evaluate differences in the environmental impacts of both processes. The solvothermal method used was developed considering the reutilization of solvent, water reflux, and a low thermal treatment to reduce pollutant emissions. As a result, a single high crystallinity olivine phase LFP was successfully synthesized. The use of ethylene glycol (EG) as a reaction medium enabled the formation of crystalline LFP at a low temperature (600 °C) with a nano-plate-like shape. The developed synthesis method was evaluated using life cycle analysis (LCA) to compare its environmental impact against the conventional production method. LCA demonstrated that the alternative green synthesis process represents 60% and 45% of the Resource Depletion impact category (water and fossil fuels, respectively) of the conventional method. At the same time, in the Climate change and Particular matter impact categories, the values correspond to 49 and 38% of the conventional method, respectively.
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Electromembrane processes for LiOH production from lithium brines obtained from solar evaporation ponds in production processes of the Salar de Atacama are considered. In order to analyze high concentrations' effect on ion exchange membranes, the use of concentrated LiCl aqueous solutions in a bipolar membrane electrodialysis process to produce LiOH solutions higher than 3.0% by mass is initially investigated. For this purpose, a mathematical model based on the Nernst-Planck equation is developed and validated, and a parametric study is simulated considering as input variables electrolyte concentrations, applied current density, stack design, process design and membrane characteristics. As a novelty, this mathematical model allows estimating LiOH production in a wide concentration range of LiCl, HCl and LiOH solutions and its effect on the process, providing data on final LiOH solution purity, current efficiency, specific electricity consumption and membrane performance. Among the main results, a concentration of 4.0% to 4.5% by LiOH mass is achieved, with a solution purity higher than 95% by mass and specific electrical energy consumption close to 4.0 kWh/kg. The work performed provides key information on process sensitivity to operating conditions and process design characteristics. These results serve as a guide in the application of this technology to lithium hydroxide production.
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Nanofluids can be employed as one of the two fluids needed to improve heat exchanger performance due to their improved thermal and rheological properties. In this review, the impact of nanoparticles on nanofluid properties is discussed by analyzing factors such as the concentration, size, and shape of nanoparticles. Nanofluid thermophysical properties and flow rate directly influence the heat transfer coefficient and pressure drop. High thermal conductivity nanoparticles improve the heat transfer coefficient; in particular, metallic oxide (such as MgO, TiO2, and ZnO) nanoparticles show greater enhancement of this property by up to 30% compared to the base fluid. Nanoparticle size and shape are other factors to consider as well, e.g., a significant difference in thermal conductivity enhancement from 6.41% to 9.73% could be achieved by decreasing the Al2O3 nanoparticle size from 90 to 10 nm, affecting nanofluid viscosity and density. In addition, equations to determine the heat transfer rate and the pressure drop in a double-pipe heat exchanger are presented. It was established that the main factor that directly influences the heat transfer coefficient is the nanofluid thermal conductivity, and nanofluid viscosity affects the pressure drop.
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The objective of this work was to evaluate obtaining LiOH directly from brines with high LiCl concentrations using bipolar membrane electrodialysis by the analysis of Li+ ion transport phenomena. For this purpose, Neosepta BP and Fumasep FBM bipolar membranes were characterized by linear sweep voltammetry, and the Li+ transport number in cation-exchange membranes was determined. In addition, a laboratory-scale reactor was designed, constructed, and tested to develop experimental LiOH production tests. The selected LiCl concentration range, based on productive process concentrations for Salar de Atacama (Chile), was between 14 and 34 wt%. Concentration and current density effects on LiOH production, current efficiency, and specific electricity consumption were evaluated. The highest current efficiency obtained was 0.77 at initial concentrations of LiOH 0.5 wt% and LiCl 14 wt%. On the other hand, a concentrated LiOH solution (between 3.34 wt% and 4.35 wt%, with a solution purity between 96.0% and 95.4%, respectively) was obtained. The results of this work show the feasibility of LiOH production from concentrated brines by means of bipolar membrane electrodialysis, bringing the implementation of this technology closer to LiOH production on a larger scale. Moreover, being an electrochemical process, this could be driven by Solar PV, taking advantage of the high solar radiation conditions in the Atacama Desert in Chile.
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A membrane electrodialysis process was tested for obtaining battery grade lithium hydroxide from lithium brines. Currently, in the conventional procedure, a brine with Li+ 4-6 wt% is fed to a process to form lithium carbonate and further used to produce lithium hydroxide. The disadvantages of this process are its high cost due to several stage requirement and the usage of lime, causing waste generation. The main objective of this work is to demonstrate the feasibility of obtaining battery grade lithium hydroxide monohydrate, avoiding production of lithium carbonate. A laboratory cell was constructed to study electrochemical kinetics and determine energetic parameters. The effects of current density, electrode material, electrolyte concentration, temperature and cationic membrane (Nafion 115 and Nafion 117) on cell performance were determined. Tests showed that a current density of 1200 A/m2 and temperatures between 75-85 °C allow reduced specific electricity consumption (SEC) (7.25 kWh/kg LiOH). A high purity product is obtained at temperatures below 75 °C, with a Nafion 117 membrane and low electrolyte concentration. Resulting key electrochemical data would enable a pilot-scale process implementation to obtain lithium compounds.
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In this work, a first study on kinetics and thermodynamics of thermal decomposition for synthesis of doped LiMn2O4 nanoparticles is presented. The effect of Mg doping concentration on thermal decomposition of synthesis precursors, prepared by ultrasound-assisted Pechini-type sol-gel process, and its significance on nucleation and growth of Mg-doped LiMn2O4 nanoparticles was studied through a method based on separation of multistage processes in single-stage reactions by deconvolution and transition state theory. Four zones of thermal decomposition were identified: Dehydration, polymeric matrix decomposition, carbonate decomposition and spinel formation, and spinel decomposition. Kinetic and thermodynamic analysis focused on the second zone. First-order Avrami-Erofeev equation was selected as reaction model representing the polymer matrix thermal decomposition. Kinetic and thermodynamic parameters revealed that Mg doping causes an increase in thermal inertia on conversion rate, and CO2 desorption was the limiting step for formation of thermodynamically stable spinel phases. Based on thermogravimetry experiments and the effect of Mg on thermal decomposition, an optimal two-stage heat treatment was determined for preparation of LiMgxMn2-xO4 (x = 0.00, 0.02, 0.05, 0.10) nanocrystalline powders as promising cathode materials for lithium-ion batteries. Crystalline structure, morphology, and stoichiometry of synthesized powders were characterized by XRD, FE-SEM, and AAS, respectively.
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The literature shows that inorganic phase change materials (PCM) have been very seldom microencapsulated, so this study aims to contribute to filling this research gap. Bischofite, a by-product from the non-metallic industry identified as having good potential to be used as inorganic PCM, was microencapsulated by means of a fluidized bed method with acrylic as polymer and chloroform as solvent, after compatibility studies of both several solvents and several polymers. The formation of bischofite and pure MgCl2·6H2O microcapsules was investigated and analyzed. Results showed an efficiency in microencapsulation of 95% could be achieved when using 2 min of fluidization time and 2 kg/h of atomization flow. The final microcapsules had excellent melting temperatures and enthalpy compared to the original PCM, 104.6 °C and 95 J/g for bischofite, and 95.3 and 118.3 for MgCl2·6H2O.
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Pyrolysis of the silicon-containing polymer {(NP[O2C12H8])0.5[NP(OC6H4 x SiMe3)2]0.5-x [NP(OC6H5) x (OC6H4SiMe3)]x}n (1) (x = 0.13), (2) (x = 0.3), and (3) {(NP[O,2C12He])0.5[NP(OC6H4SiMe2Ph),2]0.2 [NP(OC6H5)(OC6H4SiMe2Ph)]0.3}n in air at 600 degrees C, 800 degrees C and 1000 degrees C results in the formation of nanostructured SiP,2O7, along with P4O7. The morphology as well as the size and shape of the nanostructures is observed to depend on both the mole fraction of silicon, the polymer precursor and the temperature of the pyrolysis. The first observation of nanotube formation using polyphosphazenes as a template, was noted during pyrolysis of the precursor (1) at 600 degrees C. The surface morphology of the Si or SiO2, studied by AFM, depends strongly on the crystallinity of the wafer surface used during deposition. Regular lance or point-like structures were obtained from SiP2O7 deposited on SiO2 from its precursor (2). The unique formation of micro and nanostructured SiP2O7 is discussed and a mechanism of the formation of the nanostructured materials is proposed.
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Two new hybrid organic/inorganic copper oxovanadium diphosphonates [Cu2(phen)2(O3PCH2PO3)(V2O5)(H2O)] x H2O (1) and [(Cu2(phen)2(O3P(CH2)3PO3)(V2O5)] x C3H8 (2) have been obtained by hydrothermal synthesis. The compounds are monoclinic, and they crystallize in the space group P2(1)/n with cell parameters of a = 11.788(2) A, b = 17.887(3) A, c = 14.158(2) A, and beta = 93.99(0) degrees and in the space group C2/c with cell parameters of a = 11.025(1) A, b = 18.664(2) A, c = 15.054(2) A, and beta = 90.06(0) degrees, respectively. Both compounds present two-dimensional frameworks built up from infinite chains of corner-sharing vanadium tetrahedra and diphosphonate groups connected by copper tetramers for (1) and copper dimers for (2). The remarkable feature of (2) is the encapsulation of propane molecules, stabilized by strong hydrogen bonding between the layers. The magnetic properties of the compounds have been investigated showing antiferromagnetic coupling with Tmax = 64 K for (1) and Curie-like paramagnetic behavior for (2).