共沉淀法优化高镍LiNi_(0.834)Co_(0.11)Mn_(0.056)O_(2)正极材料的结构和性能

Structure and properties of high nickel LiNi_(0.834)Co_(0.11)Mn_(0.056)O_(2) cathode material optimized by the coprecipitation method

【目的】分析共沉淀法合成高镍前驱体Ni_(0.834)Co_(0.11)Mn_(0.056)(OH)_(2)的工艺条件对相应正极性能的影响,并找到最佳合成条件。【方法】在不同氨水浓度和反应溶液pH下合成前驱体和对应的正极材料,分析合成工艺条件参数对结构、微观形貌、电化学性能的影响规律。【结果】在氨水质量浓度为11 g/L、pH为11.0时,制备的Ni_(0.834)Co_(0.11)Mn_(0.056)(OH)_(2)正极材料一次颗粒致密、球形度高、粒径适中,具备最优的电化学性能:在0.1 C倍率下的首次放电比容量为205.6 mAh/g,首圈库仑效率为88.74%;在10.0 C大电流密度下的放电比容量为150.7 mAh/g;在1.0 C倍率下循环300圈后,容量保持率高达80.18%。【结论】氨水浓度和反应溶液pH通过影响溶液过饱和度,从而影响了晶体成核和生长,改变了前驱体的形貌、粒径和成分,而正极材料继承了对应前驱体的形貌特征,其电化学性能也受前驱体合成工艺的影响。

[Purposes]In order to find the optimum synthesis conditions,the technological parameters of the high nickel precursor Ni_(0.834)Co_(0.11)Mn_(0.056)(OH)_(2) in the coprecipitation processes were analyzed.Moreover,the effects on the properties of the corresponding cathodes were also been investigated.[Methods]The precursor and the corresponding cathode materials were synthesized at different ammonia concentrations and pH in the reaction solutions.In addition,the influence of the process parameters on the structural,micro-morphological and electrochemical properties was analyzed.[Findings]Under the conditions of the ammonia concentration of 11 g/L and the pH of 11.0,the prepared Ni_(0.834)Co_(0.11)Mn_(0.056)(OH)_(2) cathode material possesses dense primary particles,high sphericity,and moderate particle size,delivering best electrochemical properties.The first specific discharge capacity at 0.1 C is 205.6 mAh/g and the Coulombic efficiency of the first cycle is 88.74%.Moreover,the specific discharge capacity is 150.7 mAh/g at the high current density of 10.0 C.Meanwhile,the capacity retention is still up to 80.18%after 300 cycles at 1.0 C.[Conclusions]The ammonia concentration and the pH of the reaction solution both alter the morphology,the particle size,and the composition of the precursor by affecting the solution oversaturation and thus influencing the nucleation and the growth of the crystal.The cathode material inherits the morphological characteristics of the corresponding precursors and its electrochemical properties are affected by the precursor synthesis process.