高镍三元正极材料的包覆与掺杂改性研究进展

doi:10.15541/jim20190568

摘要/Abstract

摘要：

随着新能源汽车的加速发展, 镍钴锰/铝酸锂三元正极材料、特别是高镍(镍含量大于50%)材料作为后起之秀, 由于其性能和成本的综合指标优于传统的钴酸锂和磷酸铁锂, 引起了学术界和产业界极大的研究兴趣。但是受其本身晶体结构和表面结构的限制, 三元正极材料也存在安全性较差、循环稳定性不足等缺点。近年来, 科研工作者为解决这些问题、并进一步提升三元材料的性能, 在材料改性技术方面开展了大量工作, 取得了令人瞩目的研究成果。本文从改性元素对三元正极材料结构以及对电化学性能改善的机理出发, 介绍了包覆和掺杂两种改性技术的研究进展, 并在此基础上对三元正极材料的发展方向做出展望。

关键词: 镍钴锰酸锂, 包覆, 掺杂, 机理

Abstract:

In recent years, the development of new energy vehicles industry is accelerating. Lithium nickel cobalt manganese/aluminum oxide ternary cathode materials (NCM/NCA), especially with the nickel content ≥50%, has aroused great interest in both academia and industry. This is mainly due to the fact that the aggregative parameters of performance and cost of NCM/NCA are superior to those of traditional cathode materials, such as LiCoO₂ and LiFePO₄. However, the application of NCM/NCA is affected by a number of drawbacks, including poor safety and insufficient cycle stability and so on, which are mainly attributed to its crystal and surface structure. Researchers have carried out various efforts to solve these problems and further improve the performance of NCM/NCA. Some remarkable results have been achieved in the past few years. In this review, the latest research progress on coating and doping of Ni-rich ternary cathode materials is summarized from the view on the mechanism of structural and electrochemical improvement of NCM/NCA. Finally, the perspective for the development of NCM/NCA cathode materials is also prospected.

Key words: lithium nickel cobalt manganese oxide, coating, doping, mechanism

中图分类号:

O646

柏祥涛,班丽卿,庄卫东. 高镍三元正极材料的包覆与掺杂改性研究进展[J]. 无机材料学报, 2020, 35(9): 972-986.

BAI Xiangtao,BAN Liqing,ZHUANG Weidong. Research Progress on Coating and Doping Modification of Nickel Rich Ternary Cathode Materials[J]. Journal of Inorganic Materials, 2020, 35(9): 972-986.

图/表 11

图1 时间分辨XRD(TR-XRD)测试过程中氧的质谱分析(O2, m/z=32) (上)及NCM相变温度区域(下)[19]

Fig. 1 Mass spectroscopy profiles for the oxygen (O2, m/z=32) collected simultaneously during measurement of TR-XRD (upper panel) and the corresponding temperature region of the phase transitions for NCM (lower panel) [19]

图2 NCM523高电压循环过程中的降解机制和相变[20]

Fig. 2 Degradation mechanisms of NCM523 and phase transformation after cycle tests under high-voltage conditions[20]

图3 NCM523裸样和包覆样的第5周放电曲线(3.0~4.6 V)[49]

Fig. 3 5th discharge profiles of pristine and coated NCM523 (3.0~4.6 V)[49] (a) 1C; (b) 3C; (c) 6C

表1 不同包覆量时锂离子电池的放电比容量[52]

Table 1 Discharge capacities of Li-ion batteries with different coating amounts[52]

Sample	Discharge capacity /(mAh·g^-1)
Sample	0.1C /3 cycles	1C /5 cycles	2C /5 cycles	5C /5 cycles	10C /5 cycles	0.1C /5 cycles*
0	196.8	168.9	155.8	131.8	94.5	184.6
1wt%	213.9	185.5	170.2	148.1	121.6	207.2
2wt%	203.8	161.1	147.9	122.6	92.1	195.7

图4 循环150次后(a)裸样和(b) Li3PO4包覆的NCM622 (1wt%)的表面副产物示意图[53]

Fig. 4 Schematic illustration of byproducts on the surfaces of (a) bare and (b) lithium phosphate-coated NCM622 after cycling 150 times[53]

图5 100周循环(4.7 V)后正极材料颗粒内部微裂纹的(a~d)SEM照片及其(e)形成示意图[81]

Fig. 5 (a-d) SEM images of the cathode cracks in the particles cycled 100 times (4.7 V), and (e) schematic diagram showing crack formation[81]

图6 在(a) 45 ℃ (4.3、4.4、4.5、4.6 V, C/3)和(b) 30 ℃ (2.8~4.3 V, 不同倍率)条件下NCM523裸样和Mo掺杂样的循环曲线[96]

Fig. 6 Typical cycling performance of undoped and Mo-doped NCM523 at (a) 45 ℃ (4.3, 4.4, 4.5, and 4.6 V, C/3 rate) and (b) 30 ℃ (2.8-4.3 V, different rates)[96]

图7 可能的Ni2+迁移形成尖晶石相机制[104]

Fig. 7 Suggested mechanism for Ni2+ migration leading to a partial spinel nucleus[104] Red: oxygen atoms; Grey: Ni atoms; Violet: Mn atoms; Blue: cobalt atoms

表2 不同物质掺杂NCM622的循环和倍率性能[104]

Table 2 Cycling performances and rate capabilities of NCM622 with different doping agents[104]

Sample	Cycling performance (1C@200*)		Rate performance
Sample	3.0-4.4 V	3.0-4.6 V	16C/0.5C
Pristine	75.59%	72.99%	64.94%
Zr	87.61%	81.05%	73.94%
Zr/Ti	94.20%	91.71%	79.57%

图8 不同正极材料的(a)循环性能和(b) DSC曲线[115]

Fig. 8 (a) Cycling performance and (b) DSC results of different cathodes[115]

图9 无序层状相包覆层的示意图[133]

Fig. 9 Schematic illustration of the disordered layered phase coating layer[133]

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