阳离子无序和表面化学残留物对层状氧化物阴极初始库仑效率影响的研究

doi:10.13208/j.electrochem.2219001

摘要/Abstract

摘要：

锂层状氧化物LiNi_0.6Co_0.2Mn_0.2O₂（NCM622）是电动汽车高能锂离子电池中最有前途的正极材料之一。然而，目前NCM622的一个问题是其初始库仑效率（ICE）只有约87%，比LiCoO₂或LiFePO₄至少低6%。在本工作中，我们研究了在烧结过程中形成的表面化学残留物（如LiOH和Li₂CO₃）和Li/Ni阳离子混排对ICE的影响。结果表明，当烧结温度从825 ^oC提高到900 ^oC时，样品的ICE从80.80%提高到86.68%，而相应的Li/Ni阳离子混排和表面化学残留物也有所减少。进一步地，我们使用HNO₃溶液洗涤去除825 ^oC烧结后的样品的表面残留物，发现尽管Li/Ni阳离子紊乱有所增加，但ICE提高3.57%。这些结果表明，通过适当的烧结工艺和后处理技术将表面残留量和Li/Ni阳离子混排降至最低是获得高ICE并改善NCM622电化学性能的关键。

关键词: 锂层状氧化物, 首圈库仑效率, 表面残碱, 锂镍阳离子混排

Abstract:

Lithium layered oxide LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) is one of the most promising cathode materials in high-energy lithium-ion batteries for electric vehicles. However, one drawback for NCM622 is that its initial coulombic efficiency (ICE) is only about 87%, which is at least 6% lower than that of LiCoO₂ or LiFePO₄. In this work, we investigated the effects of surface chemical residues (e.g., LiOH and Li₂CO₃) and Li/Ni cation disorder resulted during the sintering on the ICE. We found that the ICE of the as-prepared samples could be boosted from 80.80% to 86.68% as the sintering temperatures were increased from 825 to 900 ^oC. The corresponding Li/Ni cation disorder and surface chemical residues were also reduced with the increasing sintering temperatures. Furthermore, the ICE of the sample sintered at 825 ^oC could be enhanced by 3.57% after washing with HNO₃ solution to remove the surface residues despite the Li/Ni cation disorder being increased. These results demonstrate that minimizing the amount of surface residuals and the degree of Li/Ni cation disorder through an appropriate sintering process and post-treatment technology is critical to achieve a high ICE and improve the electrochemical performances of NCM622.

Key words: lithium layered oxide cathode, initial coulombic efficiency, surface chemical residues, Li/Ni cation disorder

刘晋利, 吴涵峰, 刘志北, 吴英强, 王莉, 卑凤利, 何向明. 阳离子无序和表面化学残留物对层状氧化物阴极初始库仑效率影响的研究[J]. 电化学（中英文）, 2022, 28(11): 2219001.

Jin-Li Liu, Han-Feng Wu, Zhi-Bei Liu, Ying-Qiang Wu, Li Wang, Feng-Li Bei, Xiang-Ming He. Insight into the Effects of Cation Disorder and Surface Chemical Residues on the Initial Coulombic Efficiency of Layered Oxide Cathode[J]. Journal of Electrochemistry, 2022, 28(11): 2219001.

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参考文献 40

[1]	Wu Y Q, Xie L Q, Ming H, Guo Y J, Hwang J Y, Wang W X, He X M, Wang L M, Alshareef H N, Sun Y K, Ming J. An empirical model for the design of batteries with high energy density[J]. ACS Energy Lett., 2020, 5(3): 807-816.
[2]	Zhang B, Wang L, Zhang H, Xu H, He X M. Revelation of the transition-metal doping mechanism in lithium manganese phosphate for high performance of lithium-ion batteries[J]. Battery Energy, 2022, 1(4): 20220020.
[3]	Xue H J, Wu Y Q, Zou Y G, Shen Y B, Liu G, Li Q, Yin D M, Wang L M, Ming J. Unraveling metal oxide role in exfoliating graphite: new strategy to construct high-performance graphene-modified SiO_x-based anode for lithium-ion batteries[J]. Adv. Funct. Mater., 2020, 30(21): 1910657.
[4]	Wu Y Q, Ming H, Li M L, Zhang J L, Wahyudi W, Xie L Q, He X M, Wang J, Wu Y P, Ming J. New organic complex for lithium layered oxide modification: ultrathin coating, high-voltage, and safety performances[J]. ACS Energy Lett., 2019, 4(3): 656-665.
[5]	Zhang B, He Y F, Gao H Q, Wang X D, Liu J L, Xu H, Wang L, He X M. Unraveling the doping mechanisms in lithium iron phosphate[J]. Energy Mater., 2022, 2: 200013.
[6]	Li W D, Dolocan A, Oh P, Celio H, Park S, Cho J, Manthiram A. Dynamic behaviour of interphases and its implication on high-energy-density cathode materials in lithium-ion batteries[J]. Nat. Commun., 2017, 8: 14589. doi: 10.1038/ncomms14589 pmid: 28443608
[7]	Ryu H H, Park K J, Yoon C S, Sun Y K. Capacity fading of Ni-rich Li[Ni_xCo_yMn_1-_x_-_y]O₂ (0.6≤ x ≤ 0.95) cathodes for high-energy-density lithium-Iion batteries: bulk or surface degradation?[J]. Chem. Mater., 2018, 30(3): 1155-1163.
[8]	Wu Y Q, Xie L Q, He X M, Zhuo L H, Wang L M, Ming J. Electrochemical activation, voltage decay and hysteresis of Li-rich layered cathode probed by various cobalt content[J]. Electrochim. Acta, 2018, 265: 115-120.
[9]	Fan L, Wei S Y, Li S Y, Li Q, Lu Y Y. Recent progress of the solid-state electrolytes for high-energy metal-based batteries[J]. Adv. Energy Mater., 2018, 8(11): 1702657.
[10]	Wu Y Q, Ming J, Zhuo L H, Yu Y C, Zhao F Y. Simultaneous surface coating and chemical activation of the Li-rich solid solution lithium rechargeable cathode and its improved performance[J]. Electrochim. Acta, 2013, 113: 54-62.
[11]	Jun D W, Yoon C S, Kim U H, Sun Y K. High-energy density core-shell structured Li[Ni_0.95Co_0.025Mn_0.025]O₂ cathode for lithium-ion batteries[J]. Chem. Mater., 2017, 29(12): 5048-5052.
[12]	Lee W, Muhammad S, Kim T, Kim H, Lee E, Jeong M, Son S, Ryou J H, Yoon W S. New insight into Ni-rich layered structure for next-generation Li rechargeable batteries[J]. Adv. Energy Mater., 2018, 8(4): 1701788.
[13]	Liu W, Li X F, Xiong D B, Hao Y C, Li J W, Kou H R, Yan B, Li D J, Lu S G, Koo A, Adair K, Sun X L. Significantly improving cycling performance of cathodes in lithium ion batteries: the effect of Al₂O₃ and LiAlO₂ coatings on LiNi_0.6Co_0.2Mn_0.2O₂[J]. Nano Energy, 2018, 44: 111-120.
[14]	Lee S W, Kim M S, Jeong J H, Kim D H, Chung K Y, Roh K C, Kim K B. Li₃PO₄ surface coating on Ni-rich LiNi_0.6Co_0.2Mn_0.2O₂ by a citric acid assisted sol-gel method: improved thermal stability and high-voltage performance[J]. J. Power Sources, 2017, 360: 206-214.
[15]	Chen Z Q, Wang J, Huang J X, Fu T, Sun G Y, Lai S B, Zhou R, Li K, Zhao J B. The high-temperature and high-humidity storage behaviors and electrochemical degradation mechanism of LiNi_0.6Co_0.2Mn_0.2O₂ cathode material for lithium ion batteries[J]. J. Power Sources, 2017, 363: 168-176.
[16]	Liu S Y, Dang Z Y, Liu D, Zhang C C, Huang T, Yu A S. Comparative studies of zirconium doping and coating on LiNi_0.6Co_0.2Mn_0.2O₂ cathode material at elevated temperatures[J]. J. Power Sources, 2018, 396: 288-296.
[17]	Yuan J, Wen J W, Zhang J B, Chen D M, Zhang D W. Influence of calcination atmosphere on structure and electrochemical behavior of LiNi_0.6Co_0.2Mn_0.2O₂ cathode material for lithium-ion batteries[J]. Electrochim. Acta, 2017, 230: 116-122.
[18]	Choi J, Manthiram A. Investigation of the irreversible capacity loss in the layered LiNi_1/3Mn_1/3Co_1/3O₂ cathodes[J]. Electrochem. Solid-State Lett., 2005, 8(8): C102-C105.
[19]	Hu Q, Wu Y Z, Ren D S, Liao J Y, Song Y Z, Liang H M, Wang A P, He Y F, Wang L, Chen Z H, He X M. Revisiting the initial irreversible capacity loss of LiNi_0.6Co_0.2-Mn_0.2O₂ cathode material batteries[J]. Energy Stor. Mater., 2022, 50: 373-379.
[20]	Hong C Y, Leng Q Y, Zhu J P, Zheng S Y, He H J, Li Y X, Liu R, Wan J J, Yang Y. Revealing the correlation between structural evolution and Li⁺ diffusion kinetics of nickel-rich cathode materials in Li-ion batteries[J]. J. Mater. Chem. A, 2020, 8(17): 8540-8547.
[21]	Zhou H, Xin F X, Pei B, Whittingham M S. What limits the capacity of layered oxide cathodes in lithium batteries?[J]. ACS Energy Lett., 2019, 4(8): 1902-1906. doi: 10.1021/acsenergylett.9b01236
[22]	Zhao E Y, Fang L C, Chen M M, Chen D F, Huang Q Z, Hu Z B, Yan Q B, Wu M M, Xiao X L. New insight into Li/Ni disorder in layered cathode materials for lithium ion batteries: a joint study of neutron diffraction, electrochemical kinetic analysis and first-principles calculations[J]. J. Mater. Chem. A, 2017, 5(4): 1679-1686.
[23]	Chen M M, Zhao E Y, Chen D F, Wu M M, Han S B, Huang Q Z, Yang L M, Xiao X L, Hu Z B. Decreasing Li/Ni disorder and improving the electrochemical performances of Ni-rich LiNi_0.8Co_0.1Mn_0.1O₂ by Ca doping[J]. Inorg. Chem., 2017, 56(14): 8355-8362.
[24]	Kasnatscheew J, Evertz M, Streipert B, Wagner R, Klopsch R, Vortmann B, Hahn H, Nowak S, Amereller M, Gentschev A C, Lamp P, Winter M. The truth about the 1st cycle coulombic efficiency of LiNi_1/3Co_1/3Mn_1/3O₂(NCM) cathodes[J]. Phys. Chem. Chem. Phys., 2016, 18(5): 3956-3965. doi: 10.1039/c5cp07718d pmid: 26771035
[25]	Wei H X, Tang L B, Huang Y D, Wang Z Y, Luo Y H, He Z J, Yan C, Mao J, Dai K H, Zheng J C. Comprehensive understanding of Li/Ni intermixing in layered transition metal oxides[J]. Mater. Today, 2021, 51: 365-392.
[26]	Huang Z J, Wang Z X, Zheng X B, Guo H J, Li X H, Jing Q, Yang Z H. Structural and electrochemical properties of Mg-doped nickel based cathode materials LiNi_0.6Co_0.2-Mn_0.2-_xMg_xO₂ for lithium ion batteries[J]. RSC Adv., 2015, 5(108): 88773-88779.
[27]	Huang Z J, Wang Z X, Jing Q, Guo H J, Li X H, Yang Z H. Investigation on the effect of Na doping on structure and Li-ion kinetics of layered LiNi_0.6Co_0.2Mn_0.2O₂ cathode material[J]. Electrochim. Acta, 2016, 192: 120-126.
[28]	Yoon C S, Choi M J, Jun D W, Zhang Q, Kaghazchi P, Kim K H, Sun Y K. Cation ordering of Zr-doped LiNiO₂ cathode for lithium-ion batteries[J]. Chem. Mater., 2018, 30(5): 1808-1814.
[29]	Liu S Y, Chen X, Zhao J Y, Su J M, Zhang C C, Huang T, Wu J H, Yu A S. Uncovering the role of Nb modification in improving the structure stability and electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂ cathode charged at higher voltage of 4.5 V[J]. J. Power Sources, 2018, 374: 149-157.
[30]	Jo J H, Jo C H, Yashiro H, Kim S J, Myung S T. Re-heating effect of Ni-rich cathode material on structure and electrochemical properties[J]. J. Power Sources, 2016, 313: 1-8.
[31]	Noh H J, Youn S, Yoon C S, Sun Y K. Comparison of the structural and electrochemical properties of layered Li[Ni_xCo_yMn_z]O₂ (x = 1/3, 0.5, 0.6, 0.7, 0.8 and 0.85) cathode material for lithium-ion batteries[J]. J. Power Sources, 2013, 233: 121-130.
[32]	Eom J, Kim M G, Cho J. Storage characteristics of LiNi_0.8-Co_0.1+_xMn_0.1-_xO₂ (x = 0, 0.03, and 0.06) cathode materials for lithium batteries[J]. J. Electrochem. Soc., 2008, 155(3): A239-A245.
[33]	Shen Y B, Wu Y Q, Xue H J, Wang S H, Yin D M, Wang L M, Cheng Y. Insight into the coprecipitation-controlled crystallization reaction for preparing lithium-layered oxide cathodes[J]. ACS Appl. Mater. Interfaces, 2021, 13(1): 717-726.
[34]	Shaju K M, Rao G V S, Chowdari B V R. Performance of layered Li(Ni_1/3Co_1/3Mn_1/3)O₂ as cathode for Li-ion batteries[J]. Electrochim. Acta, 2002, 48(2): 145-151.
[35]	Su Y F, Chen G, Chen L, Li W K, Zhang Q Y, Yang Z R, Lu Y, Bao L Y, Tan J, Chen R J, Chen S, Wu F. Exposing the {010} planes by oriented self-assembly with nano-sheets to improve the electrochemical performances of Ni-rich Li[Ni_0.8Co_0.1Mn_0.1]O₂ microspheres[J]. ACS Appl. Mater. Interfaces, 2018, 10(7): 6407-6414.
[36]	Hua W B, Liu W Y, Chen M Z, Indris S, Zheng Z, Guo X D, Bruns M, Wu T H, Chen Y X, Zhong B H, Chou S L, Kang Y M, Ehrenberg H. Unravelling the growth mechanism of hierarchically structured Ni_1/3Co_1/3Mn_1/3(OH)₂ and their application as precursors for high-power cathode materials[J]. Electrochim. Acta, 2017, 232: 123-131.
[37]	Matienzo L J, Yin L I, Grim S O, Jr S W E. X-ray photoelectron spectroscopy of nickel compounds[J]. Inorg. Chem., 1973, 12: 2762-2769.
[38]	Kim K S, Winograd N. X-ray photoelectron spectroscopic studies of nickel-oxygen surfaces using oxygen and argon ion-bombardment[J]. Surf. Sci., 1974, 43(2): 625-643.
[39]	Tan B J, Klabunde K J, Sherwood P M A. XPS studies of solvated metal atom dispersed (SMAD) catalysts. Evidence for layered cobalt-manganese particles on alumina and silica[J]. J. Am. Chem. Soc., 1991, 113: 855-861.
[40]	Aoki A. X-ray Photoelectron spectroscopic studies on ZnS: MnF₂ Phosphors[J]. Jpn. J. Appl. Phys., 1976, 15: 305-311.

T (^oC)	a (Å)	b (Å)	c (Å)	V (Å³)	c/a	Li/Ni disorder (%)	R_wp (%)	R_exp (%)	Chi²
800	2.86875	2.86875	14.22397	101.3764	4.95825	2.712	7.30	5.27	1.92
825	2.86907	2.86907	14.22614	101.4143	4.95845	2.856	7.19	5.37	1.80
850	2.86918	2.86918	14.22696	101.3764	4.95855	2.568	7.89	5.15	2.35
875	2.86944	2.86944	14.22756	101.4504	4.95831	2.436	8.14	5.09	2.56
900	2.86944	2.86944	14.22770	101.4514	4.95835	1.896	7.89	4.90	2.59