【作者】 李悦；

【导师】 李运姣；

【作者基本信息】 中南大学 ， 新能源材料与器件， 2025， 硕士

【摘要】 新能源汽车的大规模产业化进程推动了动力电池能量密度的技术需求迭代升级。层状高镍三元材料凭借其比容量高、成本相对较低及安全性相对较好等优点,被认为是最具前景的高比能锂离子电池正极材料之一。然而,高镍三元材料的结构不稳定问题加剧了容量的衰减。本研究立足高镍三元材料技术发展前沿,以LiNi_0.9Co_0.05Mn_0.05O₂（NCM90）为研究对象,系统开展材料制备与机理研究,得出了最佳制备条件,为有针对性地提升电化学性能提供理论依据。本研究通过材料结构调控与表面性质优化策略实现了NCM90三元正极材料的性能优化。采用掺杂包覆来优化NCM90性能,研究了晶界调控对材料电化学行为的影响机制。首先通过锆元素（氧化锆,Zr O₂）对NCM90进行体相掺杂,并证明其在离子扩散通道、机械性能改善等方面的积极影响,锂离子扩散速率从2.32×10^-13 cm²/s提升到8.34×10^-13 cm²/s;进一步引入钐元素构建双金属共掺杂体系,得出了Zr/Sm共掺杂能降低晶界处的势垒,钝化晶界的活性位点,使其副反应减少,提高了容量的保持率,5 C放电倍率下300次循环容量保持率在97.22%。进一步优化包覆策略,研究包覆层对NCM90电化学性能、机械性能和安全性方面的积极影响。通过氧化硼（B₂O₃）和钛酸钙（Ca Ti O₃）分别对NCM90进行包覆,对修饰材料的结构、形貌、离子扩散、电化学稳定状态、机械性能和热稳定性进行了详细分析。经验证,氧化硼修饰的高镍三元材料,锂离子的扩散能力得到了提升。钛酸钙包覆的材料在10 C下容量依然有初始活化容量的83.74%,恢复到1 C时,容量恢复到了94.91%,而基体材料的容量仅恢复到81.04%。图68幅,表9个,参考文献101篇更多还原

【Abstract】 The large-scale industrialization process of new energy vehicles has promoted the iterative upgrading of the technical demand for power battery energy density.Layered high-nickel ternary materials are considered to be one of the most promising cathode materials for high-energy lithium-ion batteries due to their high specific capacity,relatively low cost and relatively good safety.However,the structural instability of high-nickel ternary materials exacerbates the attenuation of capacity.Based on the frontier of high-nickel ternary material technology,this study systematically carried out material preparation and mechanism research with LiNi_0.9Co_0.05Mn_0.05O₂（NCM90）as the research object,and obtained the optimal preparation conditions,which provided a theoretical basis for improving the electrochemical performance in a targeted manner.In this thesis,the performance optimization of NCM90 ternary cathode material was achieved through the strategy of material structure control and surface property optimization.Doping coating was used to optimize the performance of NCM90,and the influence mechanism of grain boundary regulation on the electrochemical behavior of the material was studied.Firstly,the bulk phase doping of NCM90 by zirconium element（Zirconia,Zr O₂）was demonstrated,and its positive effects on ion diffusion channels and mechanical properties were demonstrated,and the lithium ion diffusion rate increased from 2.32×10^-13 cm²/s to 8.34×10^-13cm²/s.Furthermore,samarium was introduced to construct a bimetallic co-doping system,and it was obtained that the Zr/Sm co-doping energy could reduce the potential barrier at the grain boundary,passivate the active site at the grain boundary,reduce the side reactions,and improve the capacity retention rate,which was 97.22%for 300 cycles at a discharge rate of 5 C.The coating strategy was further optimized to study the positive effects of the coating on the electrochemical properties,mechanical properties and safety of NCM90.The structure,morphology,ion diffusion,electrochemical stability,mechanical properties and thermal stability of the modified materials were analyzed in detail by coating NCM90 with boron oxide（B₂O₃）and calcium titanate（Ca Ti O₃）,respectively.It has been verified that the diffusion ability of lithium ions has been improved in high-nickel ternary materials modified by boron oxide.The capacity of the calcium titanate-coated material still has 83.74%of the initial activation capacity at 10 C,and the capacity recovers to 94.91%when it returns to 1C,while the capacity of the matrix material only recovers to 81.04%.更多还原