Synthesis Of The Spherical Cathode Materials LiNi_0.8Co_0.2O₂ Based On The Controlled Crystallization Method

Lithium-nickel-oxygen series cathode materials are promising candidates for lithium ion batteries. LiNi_0.8Co_0.2O₂ material had been successfully prepared by scientists, but it could not be widely applied because this series materials still possess various problems like the dissatisfied cycle performance, so improving performance study is necessary. Obviously, spherical material LiNi_0.8Co_0.2O₂ can be made a surface decoration much more easily than non-spherical lithium ion batteries anode material, the successful preparation of spherical material LiNi_0.8Co_0.2O₂ in this paper can lay a good foundation and provide a excellent original material for other people who want to improve materials performance. Besides, spherical material LiNi_0.8Co_0.2O₂ has high density and volume capability, so it has its own predominance than non-spherical Li-ion batteries anode material when it is used in small electronic equipment and even more used in spaceflight technology.This paper prepared spherical precursor material Ni_0.8Co_0.2(OH)₂ through controlled crystallization method, through many filtration and incessant optimization, finally found out best technics: the concentration of reactants were CNiSO₄=0.5mol/L, CCoSO₄=0.5mol/L, CNaOH=1mol/L, CNH₃·H₂O=1mol/L, pH=11.2, temperature was 55℃, NH₃:Ni₂⁺=0.8:1, reaction time was 24h, mix round speed was 800r/min, deposit time was 3h. The spherical precursor materials Ni_0.8Co_0.2(OH)₂ prepared by best technics had a compact crystal, good sphericity, the density was 2.0271g/cm3, granularity distributing is well and provide a better precursor for preparing spherical anode material LiNi_0.8Co_0.2O₂.In this paper original materials were mixed by steep ultrasonic oscillation, spherical anode materials LiNi_0.8Co_0.2O₂ were synthesised by sintering twice. The best synthesis technics was: oxide flux was 40mL/min, Li:(Ni+Co)= 1.10:1, sintered for 12h at 650℃at the first time, sintered for 5h at 720℃at the second time. Anode materials LiNi_0.8Co_0.2O₂ synthesized by the best technics were spherical had been proved by SEM, well granularity distributing were proved by laser partical sizer, cation arrangement were regular and crystal structure were integrated could be proved by X-ray diffraction analysis, Li:(Ni +Co)=1.01:1 were proved by ICP-MS, its density could reach 2.7930 g/cm³. In the voltage range of 2.8⁴.4V and at a specific current of 0.2 C the spherical anode material LiNi_0.8Co_0.2O₂ exhibited first charge quality capacity of 196.86mAh/g, first discharge quality capacity of 176.93mAh/g, corresponding volume capacity can reach 549.83mAh/cm³ and 494.17 mAh/cm³, and the capacity retention ratio is 76.28% after 100 cycling.