富锂层状氧化物作为锂离子电池正极材料具有高比容量优势. 采用草酸盐共沉淀法制备Li(Li0.22Ni0.17Mn0.61)O2，并用YF3包覆电极. 采用X-射线衍射（XRD）、扫描电子显微镜（SEM）和X-射线能谱分析（EDS）表征材料结构、观察材料形貌. 研究结果表明，材料颗粒尺寸在100 ~ 200 nm范围，YF3包覆不会改变材料结构和形貌. 电化学恒流充放电测试表明，YF3包覆Li(Li0.22Ni0.17Mn0.61)O2电极的比容量，尤其倍率比容量，明显提高. 60 mA.g-1电流密度包覆电极材料30周循环后其比容量保持在220 mAh.g-1以上，1500 mA.g-1电流密度其比容量仍可达150 mAh.g-1. 电化学阻抗谱（EIS）测试结果表明，YF3包覆电极电荷转移电阻和扩散阻抗均明显降低，电化学性能改善.
冯欣
,
李国然
,
叶世海
,
高学平
. YF3包覆Li(Li0.22Ni0.17Mn0.61)O2正极材料的性能[J]. 电化学, 2012
, 18(4)
: 322
-327
.
DOI: 10.61558/2993-074X.2925
The Li(Li0.22Ni0.17Mn0.61)O2 was prepared with oxalic co-precipitation and coated with an YF3 layer by a chemical deposition method. The as-prepared and YF3-coated Li-rich materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results demonstrate that the as-prepared and YF3-coated Li(Li0.22Ni0.17Mn0.61)O2 materials have a typical layered structure and are composed of sphere-like particles with a diameter of 100~200 nm. Galvanostatic charge-discharge tests show that the discharge capacity of the YF3-coated Li(Li0.22Ni0.17Mn0.61)O2 is obviously improved. At the low current density of 60 mA.g-1, the discharge capacity reaches 240 mAh.g-1, and remains 220 mAh.g-1 after 30 cycles. At the high current density of 1500 mA.g-1, the discharge capacity still keeps 150 mAh.g-1, showing an excellent high-rate capability. Electrochemical impedance spectra (EIS) reveal that the YF3-coated Li(Li0.22Ni0.17Mn0.61)O2 shows lower charge-transfer resistance and diffusion impedance as compared with the as-prepared Li(Li0.22Ni0.17Mn0.61)O2.
[1] Lu Z H, MacNeil D D, Dahn J R. Layered cathode materials Li[NixLi(1/3–2x/3)Mn(2/3–x/3)]O2 for lithium-ion batteries [J]. Electrochemical and Solid-State Letters, 2001, 4(11): A191-A194.
[2] Kim J S, Johnson C S, Vaughey J T, et al．Electrochemical and structural properties of xLi2MO3?(1-x)LiMn0.5Ni0.5O2 electrodes for lithium batteries (M=Ti, Mn, Zr; 0≤x≤0.3) [J]. Chemistry of Materials, 2004, 16(10): 1996-2006.
[3] Armstrong A R, Holzapfel M, Novak P, et al. Demonstrating oxygen loss and associated structural reorganization in the lithium battery cathode Li[Ni0.2Li0.2Mn0.6]O2 [J]. Journal of the American Chemical Society, 2006(26), 128: 8694-8698.
[4] Johnson C S, Li N C, Lefief C, et al. Synthesis characterization and electrochemistry of lithium battery electrodes: xLi2MnO3(1-x)LiMn0.333Ni0.333Co0.333O2 (0 ≤ x ≤ 0.7) [J]. Chemistry of Materials, 2008, 20(19): 6095-6106.
[5] Wu C R, Zhao C C, Wang Z X, et al. Li-rich layer-structured cathode materials for Li-ion batteries [J]. Progress in Chemistry, 2011, 23(10): 2038-2044.
[6] Myung S T, Izumi K, Komaba S, et al. Role of alumina coating on Li-Ni-Co-Mn-O particles as positive electrode material for lithium-ion batteries [J]. Chemistry of Materials, 2005, 17(14): 3695-3704.
[7] Zheng J M, Zhang Z R, Wu X B, et al. The effects of AlF3 coating on the performance of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 positive electrode material for lithium-ion battery [J]. Journal of The Electrochemical Society, 2008, 155(10): A775-A782.
[8] Zhao Y J, Zhao C S, Feng H L, et al. Enhanced electrochemical performance of Li[Li0.2Ni0.2Mn0.6]O2 modified by manganese oxide coating for lithium-ion batteries [J]. Electrochemical and Solid-State Letters, 2011, 14(1): A1-A5.
[9] Li J G, Wang L, Zhang Q, et al. Electrochemical performance of SrF2-coated LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion batteries [J]. Journal of Power Sources, 2009, 190(1): 149-153.
[10] Cao J N, Cao G S, Yu H M, et al. Synthesis and electrochemical performance of YF3-coated LiMn2O4 cathode materials for Li-ion batteries [J]. Rare Metals, 2011, 30(1): 39-43.
[11] Wei G Z, Lu X, Ke F S, et al. Crystal habit-tuned nanoplate material of Li[Li1/3–2x/3NixMn2/3–x/3]O2 for high-rate performance lithium-ion batteries [J]. Advanced Materials, 2010, 22(39): 4364-4367.
[12] Thackeray M M, Kang S H, Johnson C S, et al. Li2MnO3-stabilized LiMO2 (M = Mn, Ni, Co) electrodes for lithium-ion batteries [J]. Journal of Materials Chemistry, 2007, 17(30): 3112-3125.
[13] Wu Y, Manthiram A. Structural stability of chemically delithiated layered (1-z)Li[Li1/3Mn2/3]O2- zLi[Mn0.5?yNi0.5?yCo2y]O2 solid solution cathodes [J]. Journal of Power Sources, 2008, 183(2): 749-754.
[14] Meng Y S, Ceder G, Grey C P, et al. Understanding the crystal structure of layered LiNi0.5Mn0.5O2 by electron diffraction and powder diffraction simulation [J]. Electrochemical and Solid-State Letters, 2004, 7(6): A155- A158.
[15] Edstr?m K, Gustafsson T, Thomas J O. The cathode-electrolyte interface in the Li-ion battery [J]. Electrochimca Acta, 2004, 50(2/3): 397-403.
[16] Wang H Y, Tang A D, Huang K L, et al. Uniform AlF3 thin layer to improve rate capability of LiNi1/3Co1/3Mn1/3O2 material for Li-ion batteries [J]. Transactions of Nonferrous Metals Society China, 2010, 20(5): 803-808.
[17] Kuang F, Zhang D, Li Y J, et al. Electrochemical impedance spectroscopy analysis for oxygen reduction reaction in 3.5% NaCl solution [J]. Journal of Solid State Electrochemistry, 2009, 13(3): 385-390.
[18] Lee D J, Lee K S, Myung S T, et al. Improvement of electrochemical properties of Li1.1Al0.05Mn1.85O4 achieved by an AlF3 coating [J]. Journal of Power Sources, 2011, 196(3): 1353-1357.
