Browsing by Autor "Naviana Leiva"

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Crystal structure and Hirshfeld surface analysis of poly[tris(μ4-benzene-1,4-dicarboxylato)tetrakis(dimethylformamide)trinickel(II)]: a two-dimensional coordination network
(International Union of Crystallography, 2019) Cesario Ajpi; Leopoldo Suescun; Naviana Leiva; Anders Lundblad; Göran Lindbergh; Saúl Cabrera
The crystal structure of the title compound, [Ni3(C8H4O4)3(C3H7NO)4], is a two-dimensional coordination network formed by trinuclear linear Ni3(tp)3(DMF)4 units (tp = terephthalate = benzene-1,4-di-carboxyl-ate and DMF = di-methyl-formamide) displaying a characteristic coordination mode of acetate groups in polynuclear metal-organic compounds. Individual trinuclear units are connected through tp anions in a triangular network that forms layers. One of the DMF ligands points outwards and provides inter-actions with equivalent planes above and below, leaving the second ligand in a structural void much larger than the DMF mol-ecule, which shows positional disorder. Parallel planes are connected mainly through weak C-H⋯O, H⋯H and H⋯C inter-actions between DMF mol-ecules, as shown by Hirshfeld surface analysis.
SÍNTESIS DE COMPUESTOS LiTi2 (PO4)3 TIPO NASICON CON SILICIO Y BORO PARA SU EVALUACIÓN COMO ELECTROLITO SÓLIDO
(2022) Naviana Leiva; Mario Blanco; Saúl Cabrera
Se ha sintetizado por reacciones en estado sólido compuestos de estructura tipo NaSICON (Sodium Superionic Conductor) LiTi2(PO4)3 con Si y B en su estructura. La estequiometría de composición es Li4Ti2P3SiB3O con estructura tipo vitro-cerámico. Se logró mantener y optimizar la formación mayoritaria de la fase cristalina conductora de iones por regulación de TiO2 y H3PO4 a temperaturas de síntesis menores a 1000°C. Esto, fue logrado mediante un riguroso control de la temperatura durante el enfriamiento lento para la obtención de la fase de interés, considerando el B como fundente y formador de red, a temperaturas de 600°C, 700°C y 800°C. Estas fases han sido caracterizadas estructural y micro-estructuralmente por difracción de rayos X de polvo (XRD) y microscopía electrónica de barrido (SEM). El análisis estructural mediante el método de Rietveld y mapas de Fourier, muestran que el compuesto final cristaliza con estructura Rombohedral tipo NaSICON. Adicionalmente, se ha realizado el cálculo computacional de las propiedades termodinámicas para la obtención de las fases LiTi2 (PO4)3 y LiTiOPO4 por DFT para la predicción de la temperatura de síntesis obteniéndose un valor teórico de 695 °C que fueron comparados con los resultados experimentales de 700 °C.
Synthesis and Characterization of LiFePO4–PANI Hybrid Material as Cathode for Lithium-Ion Batteries
(Multidisciplinary Digital Publishing Institute, 2020) Cesario Ajpi; Naviana Leiva; Max Vargas; Anders Lundblad; Göran Lindbergh; Saúl Cabrera
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.
Synthesis and spectroscopic characterization of Fe3+-BDC metal organic framework as material for lithium ion batteries
(Elsevier BV, 2022) Cesario Ajpi; Naviana Leiva; Anders Lundblad; Göran Lindbergh; Saúl Cabrera
Synthesis and spectroscopic characterization of NiII coordination network: Poly-[tris(µ4-Benzene-1,4-dicarboxylato)-tetrakis(µ1-dimethylformamide-κ1O)-trinickel(II)] as material for lithium ion batteries
(Elsevier BV, 2022) Cesario Ajpi; Naviana Leiva; Max Vargas; Anders Lundblad; Göran Lindbergh; Saúl Cabrera
The compound Ni3(C8H4O4)3(C3H7NO)3, poly-[tris(µ4-Benzene-1,4-dicarboxylato)-tetrakis(µ1-dimethylformamide-κ1O)-trinickel(II)], was synthesized by the solvothermal method prepared via reaction between NiCl2•6H2O and terephthalic acid using N,N-dimethylformamide (DMF) as solvent. The structure was characterized by powder X-ray diffraction and infrared spectroscopy analyses. The electrochemical properties as a potential active material in lithium-ion batteries were characterized by electrochemical impedance spectroscopy and galvanostatic charge-discharge curves in a battery half-cell. The characterization results show that the coordination network contains one independent structure in the asymmetric unit. It is constructed from Ni2+ ions, terephthalate bridges and in-situ-generated DMF ligands, forming two similar two-dimensional (2D) layer structures. These similar 2D layers are in an alternating arrangement and are linked with each other by dense H—H interactions (45%) to generate a three-dimensional (3D) supramolecular framework with ordered and disordered DMF molecules. The electrochemical measurements, conducted in the potential range of 0.5–3.5 V vs Li/Li+, show that Ni3(C8H4O4)3(C3H7NO)4 has good electrochemical properties and can work as anode in lithium-ion batteries. The material presents an initial specific capacity of ∼420 mAh g−1, which drops during consecutive scans but stabilizes at ∼50 mAh g−1. However, due to the wide potential range there are indications of a gradual collapse of the structure. The electrochemical impedance spectroscopy shows an increase of charge transfer resistance from 24 to 1190 Ohms after cycling likely due to this collapse.