高镍三元正极材料表面碱性物质研究进展

Research progress on alkaline substance on surface of nickel-rich ternary cathode materials

高镍三元正极材料表面形成的碱性物质容易导致电池容量衰减加快、寿命缩短,因而调控三元材料表面碱性物质对于提高锂离子二次电池的功能和安全性至关重要。综述了高镍锂离子电池三元正极材料表面碱性物质的形成机理及处理手段,从不同角度阐述了环境中的水、二氧化碳对表面碱性物质形成的影响。探讨了表面碱性物质形成过程中,由于锂离子和过渡金属的迁移与固化引发的表面结构的相变现象,造成了三元正极材料的加工储存性能的恶化。还对降碱工艺中的洗涤、干燥、低温烧结等过程进行了重点说明,阐述了洗涤工艺对三元材料表面碱性物质降低及对材料性质的影响,指出需选择合适的洗涤、干燥条件,减小材料表面发生的变异。最后结合目前降碱工艺对后续研究方向提出了建议。

Alkaline substance is prone to form on the surface of nickel-rich ternary cathode materials,which accelerate the capacity fade and short the life of lithium-ion batteries.Therefore,it is vital to control the content of the lithium hydroxide and lithium carbonate on the surface of the nickel-rich cathode material for improving the performance and safety of batteries.The formation mechanism and the treatment of the lithium hydroxide and lithium carbonate on the surface of the Nickel-rich cathode materials were summarized.The effect of H2O and CO2 in the environment on the formation of the lithium hydroxide and lithium carbonate was discussed from different perspectives.The phase transformation of surface structure caused by the migration and solidification of Li+and transition metals during the formation of alkaline materials on surface was discussed,wich led to the deterioration of the processing and storage properties of ternary cathode materials.Washing,drying,low temperature sintering and the other“alkali-reducing”processes were also emphasized,it explained the effect of the washing process on the reduction of alkaline substances on the surface of the ternary material and the effect on the material properties.It was pointed out that it was necessary to choose appropriate washing and drying conditions to reduce the variation of the material surface.Finally,combined with the current alkali reduction process,suggestions on the follow-up research direction were put forward.