Positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a positive electrode material and a preparation method and application thereof. The positive electrode material comprises a single-crystal positive electrode material inner core and a CoxB layer located on the surface of the single-crystal positive electrode material inner core. According to the invention, the surface of the single-crystal positive electrode material is coated with the CoxB layer, so the oxygen activity of the surface/interface is reduced, side reactions are reduced, and the conductivity and the cycle performance of the material are improved. The introduction of the CoxB layer has a particularly remarkable improvement effect on the quaternary positive electrode material, and the conductivity and the cycling stability can be greatly improved under the original conditions of high capacity and low gas production, so the electrochemical performance of the positive electrode material is improved.

Description

technical field [0001] 本发明涉及锂电池技术领域,涉及一种正极材料、其制备方法和应用,尤其涉及一种正极材料、其低温合成方法、正极和锂离子电池。 Background technique [0002] 随着锂离子电池在手机、电脑、汽车、储能等领域的广泛应用,人们对电池的安全性、能量密度和循环稳定性能的需求越来越高。这种电池中最具代表性的就是正极和负极中的锂离子在嵌入与脱嵌时化学电位的变化而产生电能的锂二次电池(LIBs)。而正极材料对LIBs的性能有直接主导的作用,因此许多研究人员致力于实现容量大、充电 / 放电速度快、循环寿命长的可进行锂离子可逆的嵌入与脱嵌的正极材料。 [0003] 高镍材料尤其是高镍四元单晶正极材料被认为是最具有开发前景的正极材料,研究表明,高镍四元材料其容量高、产气较少,但是循环稳定性较差,材料导电性较低。目前对锂离子电池正极材料进行表面包覆是最有效的改性方法之一,包覆层可有效抑制活性物质与电解液的不良反应,材料循环性能得到明显改善。 [0004] 现有技术中,高镍正极材料的常规包覆方式是将正极材料和包覆剂混合后再进行高温煅烧,这样会使正极材料表面小部分过渡金属元素发生偏析,影响其放电容量;且考虑到后期量产问题,工艺步骤繁琐,严重增加了生产成本,还存在着包覆不均匀的问题。 [0005] 但是,上述方法对于高镍材料尤其是高镍四元材料的性能改善有限,且成本高,因而,对正极材料的包覆方法进行研究具有重要意义。 Contents of the invention [0006] 针对现有技术中存在的上述问题,本发明的目的在于提供一种正极材料、其制备方法和应用,尤其在于提供一种正极材料、其低温合成方法、正极和锂离子电池。 [0007] 为达上述目的,本发明采用以下技术方案: [0008] 第一方面,本发明提供一种正极材料,所述正极材料包括单晶正极材料内核和位于所述单晶正极材料内核表面的Co x B层,2≤x≤3,x例如2、2.2、2.5或3等。 [0009] 本发明利用Co x B层包覆单晶正极材料的表面,降低了表面 / 界面的氧活度,减少副反应的发生,同时提高了材料的导电性和循环性能。该Co x B层的引入对于四元正极材料的改善效果尤其显著,可以在其原有的高容量、低产...

AI Technical Summary

Problems solved by technology

[0004] In the prior art, the conventional coating method for high-nickel positive electrode materials is to mix the positive electrode material with the coating agent and then perform high-temperature calcination, which will cause segregation of a small part of the transition metal elements on the surface of the positive electrode material and affect its discharge capacity; and consider In the later stage of mass production, the process steps are cumbersome, which seriously increases the production cost, and there is also the problem of uneven coating

[0005] However, the above method has limited performance improvement for high-nickel materials, especially high-nickel quaternary materials, and the cost is high. Therefore, it is of great significance to study the coating method of positive electrode materials

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