The addition of tungsten has been reported to greatly improve the capacity retention of Ni-rich layered oxide cathode materials in lithium-ion batteries. In this work, Ni(OH)₂ precursors, coated with WO₃ and also W-containing precursors prepared by co-precipitation followed by heat treatment with LiOH·H₂O, are studied. Structural analysi s and electron microscopy show that W is incorporated as amorphous Li_xW_yO_z phases concentrated in all the grain boundaries between the primary particles of LiNiO₂ (LNO) and on the surface of the secondary particles. Tungsten does not substitute for Ni or Li in the LNO lattice no matter how W is added at the precursor synthesis stage. Scanning electron microscopy (SEM) images show that adding W greatly suppresses primary particle growth during synthesis. In agreement with previous literature reports, cycling test results show that 1% W added to LNO can greatly improve charge–discharge capacity retention while also delivering a high specific capacity. The Li_xW_yO_z amorphous phases act as coating layer on both the primary and secondary particles, restrict primary particle growth during synthesis and increase the resistance of the secondary particles to microcracking.

中文翻译：

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钨掺杂剂在LiNiO2正极材料中的作用机理

据报道，添加钨可以大大提高锂离子电池中富镍层状氧化物正极材料的容量保持率。在这项工作中，研究了涂有WO ₃的Ni(OH) _{2前体以及通过共沉淀然后用LiOH·H 2} O热处理制备的含W前体。结构分析和电子显微镜表明，W 以无定形 Li _x W _y O _{z相的形式掺入，集中在 LiNiO 2}初级粒子之间的所有晶界中(LNO) 和二次粒子的表面。无论在前体合成阶段如何添加 W，钨都不会替代 LNO 晶格中的 Ni 或 Li。扫描电子显微镜 (SEM) 图像显示，添加 W 极大地抑制了合成过程中的初级粒子生长。与之前的文献报道一致，循环测试结果表明，在 LNO 中添加 1% W 可以大大提高充放电容量保持率，同时还提供高比容量。Li _x W _y O _z非晶相在一次粒子和二次粒子上都充当涂层，限制了一次粒子在合成过程中的生长，并增加了二次粒子对微裂纹的抵抗力。