隨著科技的快速進步，對於能源的要求快速成長，各類大型電器用品與電動車對於高能量密度與長循環壽命的要求，傳統的鋰離子二次電池陰極材料如LiCoO2、Li(Ni1/3Mn1/3Co1/3)O2、LiMn2O4、LiFePO4等已無法滿足能源應用的需求。而具備高比電容量與能量密度且有著良好循環壽命的過量鋰陰極材料因而備受重視，例如，0.5 Li2MnO3．0.5 LiMn1/3Ni1/3Co1/3O2(Li[Li0.2Ni0.13Mn0.54Co0.13]O2)。在晶體結構觀點，過量鋰陰極材料擁有獨特的固溶體層狀結構，藉由超晶格結構的活化可貢獻出~280 mAh/g的第一圈可逆電容量。然而低導電度和電容量的快速衰退的問題，為目前過量鋰正極材料商業化面臨的難題。
許多研究以表面改質的方式改善這些問題，包含了無機氧化金屬氧化物的表面改質、碳材料的塗佈增加導電性。為了能同時改善這些問題，因此本研究以有機/無機雙層塗佈製程，第一層讓正丙醇鋯與其進行水解，達到均勻塗佈一層無機金屬保護層於表面之目的；第二層利用高分子導電材料 PEDOT:PSS 與單層塗佈後的過量鋰粉體進行混拌，得到具有雙層塗佈的粉體。藉由 SEM、XRD、XPS、Raman 光譜之技術，以分析雙層塗佈後材料之特性。雙層塗佈中皆有不同操縱變因，以電化學的長圈數循環充放電測試與變速率循環充放電測試進行各個樣品的電性，從中尋找適當的參數。單層改質以 0.5 wt% ZrO2 的塗佈比例在長圈數測試後得到 74.8 %，優於未改質粉體 68.6 % 的電容量維持率，並且在循環前後的充放電曲線比較中可以看出極化現象明顯獲得抑制。雙層改質以 1.0 wt% PPS的塗佈比例在變速率測試中，在 2C 的高速率區間得到優於其他參數的優異電化學表現，且進行長圈數測試後，其極化現象相對於未改質樣品也被抑制。結果顯示，本研究成功於過量鋰材料表面進行雙層塗佈，並有效改善其電化學表現，使其能更有利應用於二次鋰離子陰極材料中。

With advances in technology, the rapid growth of the energy requirement, all kinds of large electrical appliances and electric vehicles meet demands on high energy density and long cycle life, therefore conventional lithium ion secondary battery cathode materials such as LiCoO2,Li(Ni1/3Mn1/3Co1/3)O2,LiMn2O4,LiFePO4, can’t fully satisfy the demand for energy applications. With the advantages of high specific capacity, energy density and good cycle life, Li-rich cathode materials have attracted more and more attention, for example, 0.5 Li2MnO3．0.5 LiMn1/3Ni1/3Co1/3O2 (Li[Li0.2Ni0.13Mn0.54Co0.13]O2, in brief).In the view point of crystal structure, the Li-rich cathode material is considered as a solid solution of unique layered structure, by activation of the super-lattice structure can contribute ~ 280 mAh / g reversible specific discharge capacity of the first cycle. However, the problem of low conductivity and rapid decline on capacity makes Li-rich material difficult to be commercialized.
There are numerous researches on surface modification to overcome these problems, including the surface modification of the inorganic metal oxide and carbon coating to increase the conductivity. To resolve these problems at the same time, in this study, uses a double layer coating process. The first layer coated by zirconium propoxide to form an uniform inorganic metal oxide protective layer. The second layer is coated by conductive polymer PEDOT: PSS by mixing with the ZrO2 coated Li-rich particles. By SEM, XRD, XPS, Raman spectra analysis, the material properties after double coating are characterized. There are different manipulating variables on single and double coating. With the long-term electrochemical and variable C-rate test, we can find the optimal ratio for both coating layer. Single layer modification by 0.5 wt% ZrO2 can get the retention 74.8 % after long cycle test, better than the unmodified sample’s (68.6 %), and make comparison of former and after charge-discharge curve, polarization phenomenon can be suppressed. After 1.0 wt% PPS coated sample, in the high-rate segment 2C is superior to other samples, having excellent electrochemical performance, and conduct long cycle test, the polarization compared to unmodified sample is suppressed. The result suggests that a successful double coating process on Li-rich materials is achieved and have effective improvement on the electrochemical performance, these could benefit to secondary Li-ion battery cathode material application.

1. Owens, B.B., Solid state electrolytes: overview of materials and applications during the last third of the Twentieth Century. Journal of Power Sources, 2000. 90(1): p. 2-8.
2. Goodenough, J.B. and Y. Kim, Challenges for Rechargeable Li Batteries. Chemistry of Materials, 2010. 22(3): p. 587-603.
3. de las Casas, C. and W. Li, A review of application of carbon nanotubes for lithium ion battery anode material. Journal of Power Sources, 2012. 208: p. 74-85.
4. T. Richard Jow, K.X., Oleg Borodin, Makoto Ue, Electrolytes for Lithium and Lithium-Ion Batteries, ed. O.B. Kang Xu, Makoto Ue. Vol. 58. 2014: Modern Aspects of Electrochemistry.
5. Julien, C., A. Mauger, K. Zaghib, and H. Groult, Comparative Issues of Cathode Materials for Li-Ion Batteries. Inorganics, 2014. 2(1): p. 132-154.
6. Padhi, A.K., Nanjundaswamy, K. S. & Goodenough, J. B., Phospho-olivines as Positive Electrode Materials for Rechargeable Lithium Batteries. Journal of the Electrochemical Society, 1997. 144.
7. Mizushima K, J.P., Wiseman PJ, Goodenough JB, LixCoO2 (0≦x≦1): A new cathode material for batteries of high energy density. Materials Research Bulletin, 1980. 15.
8. Lu, Z., L.Y. Beaulieu, R.A. Donaberger, C.L. Thomas, and J.R. Dahn, Synthesis, Structure, and Electrochemical Behavior of Li[Ni[sub x]Li[sub 1/3−2x/3]Mn[sub 2/3−x/3]]O[sub 2]. Journal of The Electrochemical Society, 2002. 149(6): p. A778.
9. Thackeray, M.M., S.-H. Kang, C.S. Johnson, J.T. Vaughey, R. Benedek, and S.A. Hackney, Li2MnO3-stabilized LiMO2 (M = Mn, Ni, Co) electrodes for lithium-ion batteries. Journal of Materials Chemistry, 2007. 17(30): p. 3112.
10. Lei, C.H., J. Bareño, J.G. Wen, I. Petrov, S.H. Kang, and D.P. Abraham, Local structure and composition studies of Li1.2Ni0.2Mn0.6O2 by analytical electron microscopy. Journal of Power Sources, 2008. 178(1): p. 422-433.
11. Yoon, S., C.W. Lee, Y.S. Bae, I. Hwang, Y.-K. Park, and J.H. Song, Method of Preparation for Particle Growth Enhancement of LiNi[sub 0.8]Co[sub 0.15]Al[sub 0.05]O[sub 2]. Electrochemical and Solid-State Letters, 2009. 12(11): p. A211.
12. Mohanty, D., J. Li, S.C. Nagpure, D.L. Wood, and C. Daniel, Understanding the structure and structural degradation mechanisms in high-voltage, lithium-manganese–rich lithium-ion battery cathode oxides: A review of materials diagnostics. MRS Energy & Sustainability, 2015. 2.
13. Xiang, X., J.C. Knight, W. Li, and A. Manthiram, Understanding the Influence of Composition and Synthesis Temperature on Oxygen Loss, Reversible Capacity, and Electrochemical Behavior ofxLi2MnO3-(1 –x)LiCoO2Cathodes in the First Cycle. The Journal of Physical Chemistry C, 2014. 118(41): p. 23553-23558.
14. Verde, M.G., H. Liu, K.J. Carroll, L. Baggetto, G.M. Veith, and Y.S. Meng, Effect of Morphology and Manganese Valence on the Voltage Fade and Capacity Retention of Li[Li2/12Ni3/12Mn7/12]O2. ACS Applied Materials & Interfaces, 2014. 6(21): p. 18868-18877.
15. Hong, J., H.-D. Lim, M. Lee, S.-W. Kim, H. Kim, S.-T. Oh, G.-C. Chung, and K. Kang, Critical Role of Oxygen Evolved from Layered Li–Excess Metal Oxides in Lithium Rechargeable Batteries. Chemistry of Materials, 2012. 24(14): p. 2692-2697.
16. <2015-Structural-and-Chemical-Evolution-of-Li-and-Mn-Rich-Layered-Cathode-Material-sup.pdf>.
17. Liang, L., K. Du, W. Lu, Z. Peng, Y. Cao, and G. Hu, Synthesis and characterization of LiNi0.6CoxMn0.4-xO2 (x = 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3) with high-electrochemical performance for lithium-ion batteries. Electrochimica Acta, 2014. 146: p. 207-217.
18. Park, S.H., S.H. Kang, I. Belharouak, Y.K. Sun, and K. Amine, Physical and electrochemical properties of spherical Li1+x(Ni1/3Co1/3Mn1/3)1−xO2 cathode materials. Journal of Power Sources, 2008. 177(1): p. 177-183.
19. Johnson, C.S., N. Li, C. Lefief, and M.M. Thackeray, Anomalous capacity and cycling stability of xLi2MnO3•(1−x)LiMO2 electrodes (M=Mn, Ni, Co) in lithium batteries at 50°C. Electrochemistry Communications, 2007. 9(4): p. 787-795.
20. Wang, J., G. Yuan, M. Zhang, B. Qiu, Y. Xia, and Z. Liu, The structure, morphology, and electrochemical properties of Li1+xNi1/6Co1/6Mn4/6O2.25+x/2 (0.1 ≤ x ≤ 0.7) cathode materials. Electrochimica Acta, 2012. 66: p. 61-66.
21. Jeong, J.-H., B.-S. Jin, W.-S. Kim, G. Wang, and H.-S. Kim, The influence of compositional change of 0.3Li2MnO3•0.7LiMn1−xNiyCo0.1O2 (0.2 ≤ x ≤ 0.5, y = x − 0.1) cathode materials prepared by co-precipitation. Journal of Power Sources, 2011. 196(7): p. 3439-3442.
22. Lee, D.K., S.H. Park, K. Amine, H.J. Bang, J. Parakash, and Y.K. Sun, High capacity Li[Li0.2Ni0.2Mn0.6]O2 cathode materials via a carbonate co-precipitation method. Journal of Power Sources, 2006. 162(2): p. 1346-1350.
23. Cho, T.H., S.M. Park, M. Yoshio, T. Hirai, and Y. Hideshima, Effect of synthesis condition on the structural and electrochemical properties of Li[Ni1/3Mn1/3Co1/3]O2 prepared by carbonate co-precipitation method. Journal of Power Sources, 2005. 142(1-2): p. 306-312.
24. Wang, D., I. Belharouak, L.H. Ortega, X. Zhang, R. Xu, D. Zhou, G. Zhou, and K. Amine, Synthesis of high capacity cathodes for lithium-ion batteries by morphology-tailored hydroxide co-precipitation. Journal of Power Sources, 2015. 274: p. 451-457.
25. Zhu, Z. and L. Zhu, Synthesis of layered cathode material 0.5Li2MnO3•0.5LiMn1/3Ni1/3Co1/3O2 by an improved co-precipitation method for lithium-ion battery. Journal of Power Sources, 2014. 256: p. 178-182.
26. Liao, D.-q., C.-y. Xia, X.-m. Xi, C.-x. Zhou, K.-s. Xiao, X.-q. Chen, and S.-b. Qin, Sol–gel preparation of Li-rich layered cathode material for lithium ion battery with polymer polyacrylic acid + citric acid chelators. Journal of Sol-Gel Science and Technology, 2016. 78(2): p. 403-410.
27. Xiang, Y., Z. Yin, Y. Zhang, and X. Li, Effects of synthesis conditions on the structural and electrochemical properties of the Li-rich material Li[Li0.2Ni0.17Co0.16Mn0.47]O2 via the solid-state method. Electrochimica Acta, 2013. 91: p. 214-218.
28. Kou, J., L. Chen, Y. Su, L. Bao, J. Wang, N. Li, W. Li, M. Wang, S. Chen, and F. Wu, Role of Cobalt Content in Improving the Low-Temperature Performance of Layered Lithium-Rich Cathode Materials for Lithium-Ion Batteries. ACS Applied Materials & Interfaces, 2015. 7(32): p. 17910-17918.
29. Wang, C., F. Zhou, C. Ren, J. Kong, Z. Tang, J. Li, C. Yu, and W.-P. Tang, Influence of Co increment on the electrochemical properties of Li1.2[Mn0.52−0.5xNi0.2−0.5xCo0.08+x]O2 cathode materials for lithium-ion batteries. Journal of Alloys and Compounds, 2015. 643: p. 223-230.
30. Xiang, X., J.C. Knight, W. Li, and A. Manthiram, Understanding the Effect of Co3+Substitution on the Electrochemical Properties of Lithium-Rich Layered Oxide Cathodes for Lithium-Ion Batteries. The Journal of Physical Chemistry C, 2014. 118(38): p. 21826-21833.
31. <ie034085z.pdf>.
32. Song, B., M.O. Lai, Z. Liu, H. Liu, and L. Lu, Graphene-based surface modification on layered Li-rich cathode for high-performance Li-ion batteries. Journal of Materials Chemistry A, 2013. 1(34): p. 9954.
33. Song, B., H. Liu, Z. Liu, P. Xiao, M.O. Lai, and L. Lu, High rate capability caused by surface cubic spinels in Li-rich layer-structured cathodes for Li-ion batteries. Scientific Reports, 2013. 3.
34. Mohanty, D., S. Kalnaus, R.A. Meisner, K.J. Rhodes, J. Li, E.A. Payzant, D.L. Wood, and C. Daniel, Structural transformation of a lithium-rich Li1.2Co0.1Mn0.55Ni0.15O2 cathode during high voltage cycling resolved by in situ X-ray diffraction. Journal of Power Sources, 2013. 229: p. 239-248.
35. Sun, Y.-K., M.-J. Lee, C.S. Yoon, J. Hassoun, K. Amine, and B. Scrosati, The Role of AlF3 Coatings in Improving Electrochemical Cycling of Li-Enriched Nickel-Manganese Oxide Electrodes for Li-Ion Batteries. Advanced Materials, 2012. 24(9): p. 1192-1196.
36. Shunmugasundaram, R., R. Senthil Arumugam, and J.R. Dahn, High Capacity Li-Rich Positive Electrode Materials with Reduced First-Cycle Irreversible Capacity Loss. Chemistry of Materials, 2015. 27(3): p. 757-767.
37. Lee, J. and W. Choi, Surface Modification of Over-Lithiated Layered Oxides with PEDOT:PSS Conducting Polymer in Lithium-Ion Batteries. Journal of the Electrochemical Society, 2015. 162(4): p. A743-A748.
38. Li, C., H.P. Zhang, L.J. Fu, H. Liu, Y.P. Wu, E. Rahm, R. Holze, and H.Q. Wu, Cathode materials modified by surface coating for lithium ion batteries. Electrochimica Acta, 2006. 51(19): p. 3872-3883.
39. Hou, P., X. Wang, D. Song, X. Shi, L. Zhang, J. Guo, and J. Zhang, Design, synthesis, and performances of double-shelled LiNi0.5Co0.2Mn0.3O2 as cathode for long-life and safe Li-ion battery. Journal of Power Sources, 2014. 265: p. 174-181.
40. Wu, F., N. Li, Y. Su, H. Lu, L. Zhang, R. An, Z. Wang, L. Bao, and S. Chen, Can surface modification be more effective to enhance the electrochemical performance of lithium rich materials? J. Mater. Chem., 2012. 22(4): p. 1489-1497.
41. Her, L.-J., J.-L. Hong, and C.-C. Chang, Preparation and electrochemical characterizations of poly(3,4-dioxyethylenethiophene)/LiCoO2 composite cathode in lithium-ion battery. Journal of Power Sources, 2006. 157(1): p. 457-463.
42. Shi, S.J., J.P. Tu, Y.Y. Tang, X.Y. Liu, Y.Q. Zhang, X.L. Wang, and C.D. Gu, Enhanced cycling stability of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 by surface modification of MgO with melting impregnation method. Electrochimica Acta, 2013. 88: p. 671-679.
43. Zhang, X., I. Belharouak, L. Li, Y. Lei, J.W. Elam, A. Nie, X. Chen, R.S. Yassar, and R.L. Axelbaum, Structural and Electrochemical Study of Al2O3and TiO2Coated Li1.2Ni0.13Mn0.54Co0.13O2Cathode Material Using ALD. Advanced Energy Materials, 2013. 3(10): p. 1299-1307.
44. Wang, Z., E. Liu, L. Guo, C. Shi, C. He, J. Li, and N. Zhao, Cycle performance improvement of Li-rich layered cathode material Li[Li0.2Mn0.54Ni0.13Co0.13]O2 by ZrO2 coating. Surface and Coatings Technology, 2013. 235: p. 570-576.
45. Wang, Z., S. Luo, J. Ren, D. Wang, and X. Qi, Enhanced electrochemical performance of Li-rich cathode Li[Li0.2Mn0.54Ni0.13Co0.13]O2 by surface modification with lithium ion conductor Li3PO4. Applied Surface Science, 2016. 370: p. 437-444.
46. Hu, S.-K., G.-H. Cheng, M.-Y. Cheng, B.-J. Hwang, and R. Santhanam, Cycle life improvement of ZrO2-coated spherical LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries. Journal of Power Sources, 2009. 188(2): p. 564-569.
47. McQueen, T., Q. Huang, J.W. Lynn, R.F. Berger, T. Klimczuk, B.G. Ueland, P. Schiffer, and R.J. Cava, Magnetic structure and properties of theS=5／2triangular antiferromagnetα−NaFeO2. Physical Review B, 2007. 76(2).
48. West, W.C., J. Soler, M.C. Smart, B.V. Ratnakumar, S. Firdosy, V. Ravi, M.S. Anderson, J. Hrbacek, E.S. Lee, and A. Manthiram, Electrochemical Behavior of Layered Solid Solution Li2MnO3−LiMO2 (M = Ni, Mn, Co) Li-Ion Cathodes with and without Alumina Coatings. Journal of The Electrochemical Society, 2011. 158(8): p. A883.
49. Xue, L., X. Li, Y. Liao, L. Xing, M. Xu, and W. Li, Effect of particle size on rate capability and cyclic stability of LiNi0.5Mn1.5O4 cathode for high-voltage lithium ion battery. Journal of Solid State Electrochemistry, 2014. 19(2): p. 569-576.
50. Hy, S., F. Felix, J. Rick, W.-N. Su, and B.J. Hwang, DirectIn situObservation of Li2O Evolution on Li-Rich High-Capacity Cathode Material, Li[NixLi(1–2x)/3Mn(2–x)/3]O2(0 ≤x≤0.5). Journal of the American Chemical Society, 2014. 136(3): p. 999-1007.
51. Nardes, A.M., M. Kemerink, M.M. de Kok, E. Vinken, K. Maturova, and R.A.J. Janssen, Conductivity, work function, and environmental stability of PEDOT:PSS thin films treated with sorbitol. Organic Electronics, 2008. 9(5): p. 727-734.
52. Ruther, R.E., A.F. Callender, H. Zhou, S.K. Martha, and J. Nanda, Raman Microscopy of Lithium-Manganese-Rich Transition Metal Oxide Cathodes. Journal of the Electrochemical Society, 2014. 162(1): p. A98-A102.
53. Kim, Y.-S., M.-H. Chang, E.-J. Lee, D.-W. Ihm, and J.-Y. Kim, Improved electrical conductivity of PEDOT-based electrode films hybridized with silver nanowires. Synthetic Metals, 2014. 195: p. 69-74.