Method for producing protective surface layers containing aluminum for cathode materials intended for lithium-ion cells

Abstract

The subject of the application is a method for producing protective surface layers containing aluminum for cathode materials intended for lithium-ion cells, which comprises adding to a reaction reactor at a constant rate of 0.02 to 0.2 ml / min an aqueous solution of transition metals, in the form of a mixture of NiSO4•6H2O, MnSO4•H2O and CoSO4•7H2O sulfates, with the Ni:Mn:Co ratio being 0.05—0.3:0.55—0.8:0.05—0.3, and adding at a constant rate of 0.02 to 0.2 ml / min an aqueous solution of ammonia with a concentration of 0.2 to 1 mol / L, in a volume in which the ratio of moles of ammonia to the total number of moles of sulfates is 0.01—2.0. Throughout the process, the pH is monitored and an aqueous solution of Na2CO3 is added in an amount sufficient to maintain the reaction pH above 8.0.After the entire transition metal solution is consumed, an aqueous solution of Al2(SO4)3 is added to the prepared cathode material precursor at a controlled rate of 0.02 to 0.2 ml / min, in a volume in which the ratio of Al2(SO4)3 moles to the total moles of sulfates is 0.01 to 0.6. All added components are continuously mixed at a speed of 500 to 1000 rpm, at a temperature of 40°C to 90°C, under a nitrogen atmosphere. The resulting precipitate is filtered, rinsed with distilled water, and dried in vacuum. The resulting powder is then mixed with the lithium precursor Li2CO3 and annealed at a temperature of 400°C to 550°C for 4 to 5 hours, and then at a temperature of 800°C to 850°C for 6 to 15 hours. A cathode material of the formula Li1+xNiaMnbCocO2 is obtained, where x, a, b, c are numerical values ​​and x > 0, a, b, c < 1, covered with a protective surface layer containing aluminum in an amount of 1% to 5% by weight, which is in the form of spherical particles.