Preparation And Characterization Of Spherical LiNi_0.80Co_0.15Al_0.05O₂ As Power Cathode Material

The imperious need to solve range anxiety caused by blade electric vehicles'continue voyage course issues and safety issues has made massive and intense researches on safety cathode materials with high energy density and long cycle life a imperative,and Li Ni_0.80Co_0.15Al_0.05O₂ will be matured to the point of dominating cathode materials for the power batteries in terms of specific capacity,cost,and cycle life.To cope with the difficulty of Al³⁺in homogeneous co-precipitation with Ni²⁺and Co²⁺,aimed stoichiometric spherical precursor with homogeneous particle size distribution and high tap density was prepared by liquid controlled crystallization method in this paper.The obtained dried precursor was mixed with LiOH·H₂O thoroughly,and then the mix was sintered in flowing oxygen atmosphere to obtain Li Ni_0.80Co_0.15Al_0.05O₂ with preferable electrochemical performance.To obtain the stoichiometric spherical precursor,the influence of chelating agent,chelating agent concentration,p H value,pumpping speed,agitation speed,aging time on the performance were investigated systematically.The optimal conditions were:the chealting agent was citric acid,with the concentration of 0.3 mol·L^-1,the pH was 11.0,the pumpping speed was 0.05 L·h^-1,the agitation speed was 600 rpm,and the aging time was 20 h.The results also show that:1)Al³⁺was almost re-dissolved at the co-precipitation reaction without the complexing action from chealting agent,but the re-dissolution was suppressed at different degree with contribution from the chealting agent,and the new chealting agent citric acid worked better than the conventional aqueous ammonia.2)Chelating agent,chelating agent concentration,pH value,pumpping speed,agitation speed,aging time would influence the morphology,particle size distribution,tap density of the precursor in the preparation of precursor by means of liquid controlled crystallization method.Increasing the agitation speed,aging time contributed to prepare spherical precursor with homogeneous particle size distribution to a certain degree,but the improvement yielded little with higher parameter values.Meanwhile,the influence of sintering temperature,sintering time,Li/M?M=Ni+Co+Al?molar ratio on the structure and electrochemical performance of the cathode materials were investigated.The optimal conditions were:the LiNi_0.80Co_0.15Al_0.05?OH?₂ and LiOH·H₂O were mixed with a molar ratio of 1:1.05,and then the mix was sintered at 450?for 5 h,followed by heating at 790?for 20 h under oxygen flowing.The results also show that:1)The ratio of layered structure,the degree of cation disordering,degree of crystallinity and corresponding electrochemical performance increased as the sintering temperature raised,but deteriorated both the structure and electrochemical performance when sintering temperature was over 790?.2)The ratio of layered structure,the degree of cation disording,degree of crystallinity and corresponding electrochemical performance increased as the sintering temperature raised,but deteriorated both the structure and electrochemical performance when sintering time was over 20h.3)Too much or none lithium excess both deteriorated the structure and electrochemical performance.