Study of the microstructure and particles of vanadium (III) oxide, vanadium (V) oxide and lithium aluminate powders

Powder materials are widely used in the manufacture of electrochemical elements of thermal chemical sources of current. Electrochemical behavior of the powders depends on the shape and size of their particles. The results of the study of the microstructure and particles of the powders of vanadium (III), (V) oxides and lithium aluminate obtained by transmission electron and atomic force microscopy, X-ray diffraction and gas adsorption analyses are presented. It is found that the sizes of vanadium (III) and vanadium (V) oxide particles range within 70 – 600 and 40 – 350 nm, respectively. The size of the coherent-scattering regions of the vanadium oxide particles lies in the lower range limit which can be attributed to small size of the structural elements (crystallites). An average volumetric-surface diameter calculated on the basis of the surface specific area is close to the upper range limit which can be explained by the partial agglomeration of the powder particles. Unlike the vanadium oxide particles, the range of the particle size distribution of the lithium aluminate powder is narrower — 50 – 110 nm. The values of crystallite sizes are close to the maximum of the particle size distribution. Microstructural analysis showed that the particles in the samples of vanadium oxides have a rounded (V2O3) or elongated (V2O5) shape; whereas the particles of lithium aluminate powder exhibit lamellar structure. At the same time, for different batches of the same material, the particle size distribution is similar, which indicates the reproducibility of the technologies for their manufacture. The data obtained can be used to control the constancy of the particle size distribution of powder materials.

Review of Modified Nickel-Cobalt Lithium Aluminate Cathode Materials for Lithium-Ion Batteries

Ternary nickel-cobalt lithium aluminate LiNixCoyAl1‐x‐yO2 (NCA, x≥0.8) is an essential cathode material with many vital advantages, such as lower cost and higher specific capacity compared with lithium cobaltate and lithium iron phosphate materials. However, the noticeably irreversible capacity and reduced cycle performance of NCA cathode materials have restricted their further development. To solve these problems and further improve the electrochemical performance, numerous research studies on material modification have been conducted, achieving promising results in recent years. In this work, the progress of NCA cathode materials is examined from the aspects of surface coating and bulk doping. Furthermore, future research directions for NCA cathode materials are proposed.

Nanosized Lithium Aluminate (γ-LiAlO2) Synthesized by EDTA-citrate Complexing Method, Using Different Thermal Conditions

Lithium aluminate (LiAlO2) polymorphs have been synthesized by solid-state reaction, but these ceramics usually show certain limitations attributed to the low control on the particle size, morphology and specific surface area. In this sense, different chemical synthesis pathways, citrate precursor among them, have been studied to obtain ultrafine powders exhibiting enhanced textural and morphological features. Synthesis by citrate precursor method would involve the use of alternative chelating agents for the formation of more stable metal-chelate species, such as ethylene-diamine-tetra-acetic acid (EDTA). Thus, the aim of this work was to study the g-LiAlO2 synthesis by EDTA-citrate complexing approach to establish the effect of the synthesis route on the structural and microstructural characteristics of the resultant powders. The synthesized ceramic powders were calcined (600-900°C) and characterized by simultaneous TG-DTA, XRD, SEM, TEM and N2 adsorption-desorption techniques. Crystallization transition process from the precursors to the g-LiAlO2 phase is reported. Results show that chemical synthesis by EDTA-citrate complexing method can produce pure and crystalline g-LiAlO2 nanoparticles at relative low temperatures (700 ºC). The possible formation mechanism is discussed. Resumen. El aluminato de litio (LiAlO2) en sus diferentes fases polimórficas se ha sintetizado por la técnica convencional de reacción en estado sólido; sin embargo, este método presenta ciertas limitaciones desde el punto de vista del control que se tiene en el tamaño de partícula, morfología y área específica. En este sentido, se han estudiado diferentes rutas de síntesis química para la obtención de polvos ultrafinos que presenten propiedades texturales y características morfológicas mejoradas. Entre éstas, se encuentra la síntesis por citratos precursores; un método que además del ácido cítrico, puede involucrar el uso de agentes complejantes o quelantes alternativos para promover la formación de especies más estables. Un ejemplo de lo anterior es el ácido etilendiaminotetraacético o EDTA por sus siglas en inglés. El objetivo de este trabajo es estudiar la síntesis del g-LiAlO2 por el método del citrato precursor-EDTA y establecer el efecto de la ruta de síntesis sobre las características estructurales y microestructurales de los compuestos obtenidos. Los polvos cerámicos sintetizados fueron calcinados a diferentes temperaturas (600-900 ºC) y caracterizados por diferentes técnicas como ATG-ATD, DRX, MEB, MET y adsorción-desorción de N2 a baja presión. Se estudió el proceso de descomposición y cristalización de los precursores hasta la obtención del óxido metálico de aluminato de litio. Los resultados muestran que el método de síntesis propuesto es adecuado para la obtención, a baja temperatura (700 ºC), de nanopartículas de la fase cristalina y pura del g-LiAlO2. Se discute un posible mecanismo de formación del compuesto de estudio a partir de los geles precursores usados.