摘要
高镍层状氧化物LiNiO_(2)具有高理论比容量和相对低廉价格,被认为是下一代锂离子动力电池的正极材料之一。当LiNiO_(2)正极材料应用于锂离子电池时,其循环稳定性无法满足要求,需经改性后才能得以应用。采用固相法合成了Nb掺杂的层状LiNi_(1-x)Nb_(x)O_(2)(x=0.005、0.01、0.015)正极材料,利用X射线衍射、扫描电子显微镜和X射线能谱等测试手段,分析了Nb掺杂量(摩尔百分比)对其晶体结构、微观形貌及元素分布的影响,并通过恒电流间歇滴定和交流阻抗测试研究了其电化学性能。结果表明,随着Nb元素掺杂量的提高,LiNi_(1-x)Nb_(x)O_(2)材料的晶格晶面间距逐渐扩大,一次颗粒尺寸逐渐减小。在LiNiO_(2)材料中引入Nb^(5+)离子,提高了LiNi_(1-x)Nb_(x)O_(2)材料的锂离子扩散系数,并通过稳定晶体结构,抑制了Nb掺杂材料在充放电过程中的相变,有利于其电化学性能的提升。当Nb掺杂量为1%时,LiNi_(1-x)Nb_(x)O_(2)材料表现出较好的倍率性能,在10 C大电流密度下的放电比容量高达134.1 mAh·g^(-1);随着Nb掺杂量的增加,LiNi_(1-x)Nb_(x)O_(2)材料循环稳定性同步提升,当Nb掺杂量为1.5%时,LiNi_(1-x)Nb_(x)O_(2)材料经150次循环后的容量保持率为73.3%,远高于未掺杂LiNiO_(2)样品的36.2%。表明,Nb掺杂可改善LiNiO_(2)正极材料的晶体结构和电化学性能,为其在下一代锂离子动力电池的应用提供了理论依据。
The layered nickel-rich oxide LiNiO_(2),characterized by its high theoretical specific capacity and relatively low cost,is considered one of the next-generation cathode materials for lithium-ion batteries.However,its cycling stability fails to meet requirements when applied in lithium-ion batteries,necessitating modification before practical use.Layered LiNi_(1-x)Nb_(x)O_(2)(x=0.005,0.01,0.015)cathode materials doped with Nb were synthesized via solid-state reaction.The effects of niobium doping level(in mole percentage)on the crystal structure,microstructure,and elemental distribution were investigated using techniques such as X-ray diffraction,scanning electron microscopy,and energy-dispersive X-ray spectroscopy.Additionally,electrochemical tests were conducted to evaluate their electrochemical performance.The results indicate that with an increase in the Nb doping level,the interplanar spacing of the LiNi_(1-x)Nb_(x)O_(2)material lattice gradually enlarges,while the primary particle size decreases.Introducing Nb^(5+)ions into the LiNiO_(2)material enhances the lithium ion diffusion coefficient of LiNi_(1-x)Nb_(x)O_(2)and stabilizes the crystal structure,suppressing phase transitions during charge-discharge processes,thereby improving electrochemical performance.When the Nb doping level is 1%,LiNi_(1-x)Nb_(x)O_(2)exhibits excellent rate capability,with a discharge specific capacity of 134.1 mAh∙g^(-1)at a high current density of 10 C.Moreover,the cycling stability of LiNi_(1-x)Nb_(x)O_(2)improves with increasing Nb doping level.For instance,when the Nb doping level is 1.5%,the capacity retention of LiNi_(1-x)Nb_(x)O_(2)after 150 cycles is 73.3%,which is significantly higher than that of the undoped LiNiO_(2)sample at 36.2%.This study demonstrates that Nb doping can improve crystal structure and electrochemical properties of the LiNiO_(2)cathode material,providing a theoretical basis for its application.
作者
孟祥聪
刘丽英
MENG Xiangcong;LIU Liying(School of Materials and Energy,Guangdong University of Technology,Guangzhou 510006,China)
出处
《材料研究与应用》
CAS
2024年第2期207-214,共8页
Materials Research and Application
