Direct Dry Synthesis of LiNi0.8Co0.2O2 Thin Film for Lithium Ion Battery Cathodes
While solid state reactions and sol-gel methods have been widely used to synthesize LiNi0.8Co0.2O2 powders, there are many problems associated with these processes, such as structural inhomogeneity, multiple time consuming steps, irregular morphology and poor control of the particle size [14-16]. Reactive spray deposition technology (RSDT), a one-step flame based deposition method, offers a convenient solution to electrode fabrication by direct deposition of LiNi0.8Co0.2O2 nanoparticles. Films can be grown directly on the current collector. RSDT has the capability to tailor the electrochemical properties of synthesized cathode materials by manipulating the several key processing conditions. The size, morphology, and composition of particles can be controlled by changing the reactant concentration in the solvent, the heat enthalpy of solvent, the flow rate of precursor solution, and the flow rate of oxidant gases. Precursor solution for flame combustion is prepared by dissolving acetylacetonates of lithium, cobalt and nickel into organic solvents like methanol.
X-ray diffraction (XRD), transmission electron microscopy (TEM) and inductively coupled plasma (ICP) are used to characterize the chemical composition, crystal structure, and structural morphology of the synthesized LiNi0.8Co0.2O2 nanoparticles. Electrochemical properties of as-deposited LiNi0.8Co0.2O2 thin film are evaluated with typical 2032 coin half-cell using lithium foil as the counter electrode. As the particle size of cathode material is in the nanometer range, the diffusion length of lithium ions is small, which enables a fast charge and discharge rate. The large surface area of the nanoparticles can also reduce the resistance of charge transfer.
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