Study On Sol-gel Spin Coating Preparation And Properties Of LiNi_0.5Mn_0.5O₂ Cathode Thin-films

LiNi0.5Mn0.5O2 as a layered structure of lithium-ion battery cathode materials with stable structure, high specific capacity, heat safety, low cost of raw materials, is considered the most research value of the material system, but on the LiNi0.5Mn0.5O2 thin film materials reported less. The paper selected as a research system LiNi0.5Mn0.5O2 thin films, sol-gel spin coating method. The process is simple, and RF magnetron sputtering, pulsed laser deposition (PLD) compared with other physical methods do not need expensive equipment, preparation costs are lower, and the chemical composition easy to control, easy to scale production.The comprehensive study reported in the literature, select the cheap and easily obtained lithium acetate, manganese acetate and nickel acetylacetone raw material by a large number of experiments to explore the stability of a uniform method for the preparation of precursor sol. By spin coating techniques, in Si substrate, Pt/Ti/SiO2/Si substrate and the Pt substrate LiNi0.5Mn0.5O2 films were prepared. Mainly discussed the preparation of sol-gel films by spin-coating of film quality and performance in a variety of factors:(1) precursor solution preparation, including raw material ratio, the total metal ion concentration in solution and the concentration of film-forming additives on the film quality; (2) spin-coating process, including the rejection of plastic speed and time control, the determination of wet film drying process; (3) high temperature annealing method, annealing temperature on the structure of the films LiNi0.5Mn0.5O2, shape and the morphology and electrochemical properties. Using a variety of testing methods XRD, SEM, TG/DSC, ICP, CV and electrochemical performance testing, test, system of raw material ratio, PVP amount, annealing temperature and film preparation parameters on the structure of LiNi0.5Mn0.5O2, morphology and electrochemical properties. By optimizing the process parameters, we got the surface crystallization of the system uniform and compact film material LiNi0.5Mn0.5O2 no cracks, with good electrochemical performance.Studies show that the best system for the precursor solution:lithium acetate+nickel acetylacetone+manganese acetate+water+acetic acid to PVP as a film-forming additives, including Li/(Mn+Ni)=1.20, metal ions total concentration of 0.66 mol/L is appropriate, PVP optimal concentration of 0.5 mol/L; spin-coating process speed in 3000rpm, time 30s, five are required to repeat the spin-coated film thickness; when the drying temperature was 450℃, and 700℃(heating rate control certain) 30min annealing structure of thin films obtained LiNi0.5Mn0.5O2 morphology and electrochemical performance is good. XRD results show that under the best conditions LiNi0.5Mn0.5O2 thin films prepared with pure phase of layered structure, ICP analysis of the chemical composition of thin films Li1.01Ni0.5Mn0.5O2, in the voltage range of 2.5V-4.5V to 20μA/cm2 of the current charge and discharge, the initial discharge capacity of 92.28/μAh/cm2μm, after 50 cycles 73.68μAh/cm2μm, the capacity retention rate of about 80%.