Modification mechanism of Ho doped NCM622 induced local electron remodeling to inhibit cationic mixing

doi:10.11949/0438-1157.20250291

Abstract

Abstract:

LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) is a high nickel cathode material for lithium-ion batteries. The nickel content brings higher specific capacity and certain thermal stability. However, the nickel-lithium mixing phenomenon in the charge-discharge process of the material inhibits the further increase of its specific capacity and affects the lattice stability. In order to alleviate this phenomenon to obtain higher-performance NCM622 materials, the lanthanide element Ho is doped for modification. The Ho element has high-energy d and f-layer electrons, which can significantly increase the degree of electron delocalization inside the material, inhibit nickel-lithium mixing, and improve lattice stability by reducing charge concentration. Compared with the pure phase material, Ho-doped NCM622 can achieve a discharge specific capacity of 196.82 mAh·g^-1, and still has a retention rate of 92.6% after multiple charge-discharge cycles. Finally, the specific modification mechanism of Ho doping was discussed through the change of microstructure before and after cycling and first-principles calculation, which has certain guiding significance for rare earth doping of lithium ion battery.

Key words: lithium-ion battery, cathode material, electrochemistry, optimization, renewable energy

摘要：

LiNi_0.6Co_0.2Mn_0.2O₂（NCM622）为锂离子电池高镍正极材料，镍含量为其带来了更高的比容量，同时具有一定的热稳定性，但材料充放电过程中存在的镍锂混排现象抑制了其比容量的进一步增加且影响晶格稳定性。为了缓解这种现象以得到更高性能的NCM622材料，用镧系元素钬（Ho）掺杂进行改性，Ho元素具备高能级的d、f层电子，能够显著增加材料内部的电子离域程度，抑制镍锂混排，通过降低电荷集中程度提高晶格稳定性。Ho掺杂NCM622能够达到196.82 mAh·g^-1的放电比容量，并且在多次充放电循环下仍有92.6%的容量保持率。最后通过循环前后微观结构的变化与第一性原理计算探讨了Ho掺杂的具体改性机理，可为锂离子电池稀土掺杂的研究提供参考。

关键词: 锂离子电池, 正极材料, 电化学, 优化, 再生能源

CLC Number:

TQ 028.8

Xinran LI, Longjiao CHANG, Shaohua LUO, Yongbing LI, Ruifen YANG, Zenglei HOU, Jie ZOU. Modification mechanism of Ho doped NCM622 induced local electron remodeling to inhibit cationic mixing[J]. CIESC Journal, 2025, 76(7): 3733-3741.

李欣然, 常龙娇, 罗绍华, 李永兵, 杨瑞芬, 侯增磊, 邹杰. Ho掺杂诱导NCM622局域电子重构抑制阳离子混排的改性机制研究[J]. 化工学报, 2025, 76(7): 3733-3741.

Figures/Tables 8

Fig.1 NCM622 preparation flow

Fig.2 (a) XRD patterns of pure phase and Ho-doped samples; (b) Local amplified XRD patterns; (c) SEM images of the two materials

Fig.3 (a) XRD refinement of pure phase and Ho-doped samples; (b) Crystal structure and unit cell parameters of the two materials

Fig.4 (a) The first charge-discharge curves of pure phase and Ho-doped samples; (b) Rate performance; (c) Long cycle performance at 0.1C charge-discharge rate; (d)Electrochemical impedance curve

Fig.5 (a) XRD patterns of pure phase and Ho-doped samples after cycling; (b) SEM images of the two samples after cycles;(c) TEM image of Ho-doped NCM622 and the FFT of the corresponding region

Fig.6 Mechanism of NCM622 modification

Fig.7 (a) The band structure and (b) partial density of states of Ho-doped NCM622

Table 1 Comparison of properties of NCM622 doped with different rare earths

材料	比容量/(mAh·g^-1)	文献
LiNi_0.55Co_0.2Mn_0.2Ho_0.05O₂	196.82	本文
LiNi_0.595Co_0.2Mn_0.2Nd_0.005O₂	160.1	[35]
LiNi_0.59Co_0.2Mn_0.2La_0.01O₂	151.8	[35]
LiNi_0.595Co_0.2Mn_0.2Eu_0.005O₂	153.1	[35]
LiNi_0.6Co_0.2Mn_0.2O₂-1/24Ce doped	248	[30]

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