摘要
高镍层状LiNi_(x)Co_(y)Mn_(1-x-y)O_(2)(x≥0.6)三元材料具有较高的能量密度,但因锂镍混排、结构稳定性不佳等问题限制了其在锂离子电池中的应用。因此,采用Nb_(2)O_(5)包覆对三元材料LiNi_(0.6)Co_(0.1)Mn_(0.3)O_(2)(NCM613)进行改性,并考察了不同包覆量对NCM613的形貌结构和电化学性能的影响,得出了最佳工艺条件的包覆量为0.75%。首先,采用共沉淀法制备了前驱体Ni_(0.6)Co_(0.1)Mn_(0.3)(OH)_(2);然后利用高温固相法制备了裸样LiNi_(0.6)Co_(0.1)Mn_(0.3)O_(2)(NCM613);最后加入不同物质的量的Nb_(2)O_(5)粉末,通过球磨后高温烧结回火法制备了不同比例包覆量的Nb_(2)O_(5)@NCM613样品。XRD分析结果表明,各包覆样品与裸样NCM613的晶体结构相似,都具有完整的α-NaFeO_(2)层状结构,阳离子混排程度较低;SEM分析结果表明,包覆样品和裸样NCM613均为1.0~1.5μm的类球状粒子,且Ni、Co、Mn和Nb元素均匀分布在类球状材料表面;TEM分析结果表明,0.75Nb_(2)O_(5)@NCM613样品的Nb_(2)O_(5)包覆层厚度约为10~20 nm;材料电化学性能研究结果表明,在2.7~4.3 V、0.2C的电流密度条件下NCM613和0.75Nb_(2)O_(5)@NCM613的首圈放电比容量分别为208.11,237.39 mA·h/g,1.0C循环100圈后,0.75Nb_(2)O_(5)@NCM613的放电比容量为176.43 mA·h/g,容量保持率高达86%。与裸样相比,在100圈循环后0.75Nb_(2)O_(5)@NCM613的阻抗明显降低,电化学极化降低,可逆性增强,这是因为Nb_(2)O_(5)包覆能提高材料的结构稳定性和电化学性能。可见,Nb_(2)O_(5)包覆高镍三元材料有利于推动高镍层状正极材料的工业化生产。
With its high discharge capacity,ternary Ni-rich layered LiNi_(x)Co_(y)Mn_(1-x-y)O_(2)(x≥0.6)materials have found an extensive application in many fields,however,the application in lithium-ion batteries is limited by its lithium-nickel mixed arrangement and poor structural stability.The ternary material LiNi_(0.6)Co_(0.1)Mn_(0.3)O_(2)(NCM613)is modified by Nb_(2)O_(5)coating,followed by an investigation of the influence of different coating amounts on the morphology,structure and electrochemical performance of NCM613,thus obtaining an optimum coating amount of 0.75%.The precursor LiNi_(0.6)Co_(0.1)Mn_(0.3)O_(2)(OH)_(2)is first prepared by co-precipitation method,followed by the preparation of the bare sample LiNi_(0.6)Co_(0.1)Mn_(0.3)O_(2)(NCM613)by adopting the high-temperature solid-phase method,with a final addition of Nb_(2)O_(5)powders of different molar.Meanwhile coated samples with different ratios of Nb_(2)O_(5)@NCM613 are prepared by high temperature sintering and tempering after ball milling.An X-ray diffraction(XRD)study shows that there is a similarity between the crystal structure of the coated sample and the bare NCM613,both of which have a completeα-NaFeO_(2)layered structure with a low degree of cation mixing;SEM analysis shows that the coated sample and the bare NCM613 are both 1~1.5μm-like spherical particles,with the elements of Ni,Co,Mn and Nb uniformly distributed on the surface of the spherical-like material.TEM analysis showed that the Nb_(2)O_(5)coating thickness of 0.75Nb_(2)O_(5)@NCM613 is about 10~20 nm.The study of the electrochemical properties of the materials shows that the specific capacities of NCM613 and 0.75Nb_(2)O_(5)@NCM613 are 208.11 mA·h/g and 237.39 mA·h/g in the first cycle at current densities of 2.7~4.3 V and 0.2C,respectively.After 100 cycles at 1.0C,the discharge specific capacity of 0.75Nb_(2)O_(5)@NCM613 is 176.43 mA·h/g,with its capacity retention rate as high as 86%.Compared with the bare sample,there is a significant reduction of the impedance of 0.75Nb_(2)O_(5)@NCM613 after 100 cycles,with the electrochemical polarization reduced,and the reversibility enhanced as well,due to the fact that the Nb_(2)O_(5)coating helps to improve the structural stability and electrochemical performance of the material.Therefore,Nb_(2)O_(5)-coated high-nickel ternary material is conducive to the promotion of the industrial production of high-nickel layered cathode materials.
作者
席帅
唐娴敏
旷焕
陈昱珏
肖利
XI Shuai;TANG Xianmin;KUANG Huan;CHEN Yujue;XIAO Li(College of Materials and Advanced Manufacturing,Hunan University of Technology,Zhuzhou Hunan 412007,China)
出处
《湖南工业大学学报》
2022年第4期31-38,共8页
Journal of Hunan University of Technology
基金
国家自然科学基金资助项目(51774127)
湖南省教育厅科研基金资助项目(20k044)。
