锂离子电池正极材料的改性和电池评价新方法研究
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摘要
为了提高锂离子电池正极材料LiMn_2O_4的电池容量和循环稳定性,前人实验过的方法不计其数,其中用元素Ti对LiMn_2O_4进行掺杂的方法,由于使结构更不稳定而被否定。但TiO_2结构中有允许锂离子迁移的通道,用TiO_2对LiMn_2O_4表面进行修饰,可以避免整体掺杂Ti元素所带来的弊端。本文用TiO_2以溶胶凝胶法对LiMn_2O_4进行了表面修饰,在LiMn_2O_4颗粒的表面形成了一种LiTixMn2-xO4固熔体。所得的产物TiO_2修饰的LiMn_2O_4(以下称TiO_2-LiMn_2O_4)作为正极材料在高温以及高电压下有明显改进的电化学性能:在55 oC下循环30周后,容量仍可保持初始容量的90%;而相同实验条件下LiMn_2O_4在55 oC下循环25周容量只能保持初始容量的30%。在较高电压范围3.0~4.8 V之间工作时,TiO_2-LiMn_2O_4材料循环60周后容量可以保持为初始容量85%,而LiMn_2O_4材料容量循环40周后容量为初始容量的70%.用交流阻抗法测试电池的阻抗,发现TiO_2-LiMn_2O_4电池较LiMn_2O_4电池阻抗得到了很大的降低.
电化学阻抗除了用在评价两种正极材料性能之外,还用于评价18650型商业锂离子电池性能.对18650商业电池进行了阻抗随循环次数、工作温度以及工作电压变化的测试。结果表明大量次数循环会引起阻抗的增加,引起阻抗增加的主要原因是电解质电阻(Re)的增加,而不是SEI电阻(Rsl),或者电荷转移电阻(Rct)的增加.
低温下(<-20 oC)锂离子电池无法正常工作,不论是充电过程还是放电过程,这一点与以往的研究结果不同。低温下电池有较差性能,主要因为正极电荷转移电阻(Rct)值增加了两个数量级。另外,论文还对荷电状态对阻抗的影响进行了研究,并对影响的原因进行了探索。
In order to improve the capacity and cycling stability of LiMn_2O_4 cathode of Lithium ion batteries, much effort was given by other researchers. The method of doping element Ti into spinel LiMn_2O_4 was abandoned for thorough doping Ti harms the structure stability by enlarging the electrostatic repulsion. However, TiO_2 consists of channels allowing Li ion to travel which reminds to modify the surface of LiMn_2O_4 using TiO_2 avoiding thorough doping Ti. The surface of spinel LiMn_2O_4 was modified with TiO_2 by a simple sol-gel method to improve its electrochemical performance at elevated temperatures and higher working potentials. Compared with pristine LiMn_2O_4, surface-modification improved the cycling stability of the material. The capacity retention of TiO_2-modified LiMn_2O_4 was more than 85% after 60 cycles at high potential cycles between 3.0 and 4.8 V at room temperature and near to 90% after 30 cycles at elevated temperature of 55°C at 1 C charge-discharge rate. Electrochemical impedance spectroscopy (EIS) was used to study the materials and impedance of TiO_2-modified LiMn_2O_4 is decreased greatly compared to the pristine LiMn_2O_4.
Electrochemical impedance spectroscopy (EIS) was also used to study the electrochemical performance of 18650 Li-ion batteries vs cycling, low temperatures and state of charge. Results show that the increase of battery resistance after long cycling is mainly from the Re(electrolyte resistance) but not Rsl or Rct.
At low temperatures (<-20°C), neither the discharge nor charge process can be carried out normally, which is inconsistent with the former belief. The poor performance of batteries at low temperatures is linked to the resistance increase of Rct by 2 magnitude grade. We also found that the SOC (state of charge) has impact on Rct, and additionally, gave the reasonable explanation.
电化学阻抗除了用在评价两种正极材料性能之外,还用于评价18650型商业锂离子电池性能.对18650商业电池进行了阻抗随循环次数、工作温度以及工作电压变化的测试。结果表明大量次数循环会引起阻抗的增加,引起阻抗增加的主要原因是电解质电阻(Re)的增加,而不是SEI电阻(Rsl),或者电荷转移电阻(Rct)的增加.
低温下(<-20 oC)锂离子电池无法正常工作,不论是充电过程还是放电过程,这一点与以往的研究结果不同。低温下电池有较差性能,主要因为正极电荷转移电阻(Rct)值增加了两个数量级。另外,论文还对荷电状态对阻抗的影响进行了研究,并对影响的原因进行了探索。
In order to improve the capacity and cycling stability of LiMn_2O_4 cathode of Lithium ion batteries, much effort was given by other researchers. The method of doping element Ti into spinel LiMn_2O_4 was abandoned for thorough doping Ti harms the structure stability by enlarging the electrostatic repulsion. However, TiO_2 consists of channels allowing Li ion to travel which reminds to modify the surface of LiMn_2O_4 using TiO_2 avoiding thorough doping Ti. The surface of spinel LiMn_2O_4 was modified with TiO_2 by a simple sol-gel method to improve its electrochemical performance at elevated temperatures and higher working potentials. Compared with pristine LiMn_2O_4, surface-modification improved the cycling stability of the material. The capacity retention of TiO_2-modified LiMn_2O_4 was more than 85% after 60 cycles at high potential cycles between 3.0 and 4.8 V at room temperature and near to 90% after 30 cycles at elevated temperature of 55°C at 1 C charge-discharge rate. Electrochemical impedance spectroscopy (EIS) was used to study the materials and impedance of TiO_2-modified LiMn_2O_4 is decreased greatly compared to the pristine LiMn_2O_4.
Electrochemical impedance spectroscopy (EIS) was also used to study the electrochemical performance of 18650 Li-ion batteries vs cycling, low temperatures and state of charge. Results show that the increase of battery resistance after long cycling is mainly from the Re(electrolyte resistance) but not Rsl or Rct.
At low temperatures (<-20°C), neither the discharge nor charge process can be carried out normally, which is inconsistent with the former belief. The poor performance of batteries at low temperatures is linked to the resistance increase of Rct by 2 magnitude grade. We also found that the SOC (state of charge) has impact on Rct, and additionally, gave the reasonable explanation.
引文
[1] 陈海龙.纳米锂离子电池阴极材料制备和性能研究:[硕士学位论文]. 北京:清华大学化学系,2002
[2] 吴宇平, 万春容, 姜长印, 等. 锂离子二次电池. 北京: 化学工业出版社, 2002
[3] M. Yoshio, H. Tanaka, K. Tominaya, et al. J. Electrochem. Soc., 1992, 40: 347~353
[4] G.X. Wang, S. Zhong. Synthesis and characterization of LiNiO2 compounds as cathodes for rechargeable lithium batteries. J. Power Sources, 1998, 76: 141~146
[5] Kweon, Ho-Jin, Kim. Modification of LixNi1?yCoyO2 by applying a surface coating of MgO. J. Power Sources, 2000, 88: 255~261
[6] A. Rougier, P. Gravereau, C. Delmas. Optimization of the composition of the Li1–zNi1+zO2 electrode materials: structural, magnetic, and electrochemical studies. J. Electrochem. Soc., 1996, 143: 1168~1175
[7] M. Yoshio, H. Nakamura. Lithiated manganese dioxide, Li0.33MnO2, as a 3V cathode for lithium batteries. Electrochim. Acta, 1999, 45: 273~283
[8] B. Banov, A. Momchilov. Li0.33MnO2-cathode material for secondary lithium batteries. J. Power Sources, 1999, 82: 562~565
[9] Y. Juji, Y. Mikya, JP0837027, 1996
[10] Y. Matsumura, S. Wang, J. Mondori. Mechanism leading to irreversible capacity loss in Li ion rechargeable batteries. J. Electrochem. Soc., 1995, 142: 2914~2918
[11] I. Kootschau, M.N. Richard, J.R. Dahn. Orthorhombic LiMnO2 as a high capacity cathode for Li-ion cells. J. Electrochem. Soc., 1995, 142: 2906~2910
[12] 周恒辉, 慈云祥. 锂离子电池阴极材料. 化学进展, 1998, 3: 85~91
[13] M.M. Thackeray. Structure Considerations of layered and spinel lithiated oxides for lithium ion batteries. J. Electrochem. Soc., 1995, 142: 2558~2563
[14] H. Berg, H. Rundlov, J.O. Thomas. The LiMn2O4 to lambda-MnO2 phase transition studied by in situ neutron diffraction. Solid State Ionics, 2001, 144: 65 ~69
[15] W. Liu, G.C. Farrington, F. Chaput, et al. Synthesis and electrochemical studies of spinel phase LiMn2O4 cathode materials prepared by the pechini process. J. Electrochem. Soc., 1998, 143: 879~884
[16] A.S. Yu, H.Q. Wu. The electrochemical intercalation reaction of lithium into spinel phase [Mn2O4]. 1. thermodynamic behavior. Acta Chimica Sinica, 1994,52: 763-766
[17] M. Benaissa, M. Joseyacaman, T.D. Xiao, et al. Microstructural study of hollandite-type MnO2 nano-fibers. Appl. Phys. Lett., 1997, 70: 2120~2122
[18] 崔万秋, 杨丽芬. 锂离子电池阴极材料 Li1+xMn2O4 的合成与特性. 功能材料, 1998, 29: 378~380
[19] 吴晓梅, 杨清河. 电化学, 1998, 4: 365~371
[20] I. Hiroshi, S. Kyuta. JP0831459, 1996
[21] S.T. Myung, H.T. Chung. Effect of mixing sequence on the electrode characteristics of lithium-ion rechargeable batteries. J. Power Sources, 1999, 84: 32~38
[22] K.T. Hwang, W.S. Um,et al. Powder synthesis and electrochemical properties of LiMn2O4 prepared by an emulsion-drying method. J. Power Sources, 1998, 74: 169~174
[23] E. Rossen, J.N. Reimers, J.R. Dahn. Synthesis and electrochemistry of spinel LT---LiCoO2 Solid State Ionics,1993, 62: 53~60
[24] R.J. Gummow, A. Kock, M.M. Thackeray. Improved capacity retention in rechargeable 4V lithium manganese oxide (spinel) cells. Solid State Ionics, 1994, 69: 59~62
[25] 孔海霞. 电化学阻抗谱图法 TiO2 薄膜光电极能带结构和催化活性研究: [硕士学位论文]. 太原: 太原理工大学应用化学系, 2004
[26] 曹楚南, 张鉴清. 电化学阻抗谱导论. 北京: 科学出版社, 2002
[27] 吴宇平, 万春容, 姜长印, 等. 锂离子二次电池. 北京: 化学工业出版社, 2002. 32~33
[28] 吴宇平, 万春容, 姜长印, 等. 锂离子二次电池. 北京: 化学工业出版社, 2002. 34~40
[29] L. Kavan, M. Gr?izel, J. Rathousk, et al. Nanocrystalline TiO2 (anatase) electrodes: Surface morphology, adsorption, and electrochemical properties. J. Electrochem. Soc., 1996, 143: 394~400
[30] M. Wagemaker, A.A. van Well, G.J. Kearley, et al. The life and times of lithium in anatase TiO2. Solid State Ionics, 2004, 175: 191~193
[31] L. Hernan, J. Morales, L. Sanchez, et al. Use of Li-M-Mn-O [M = Co, Cr, Ti] spinels prepared by a sol-gel method as cathodes in high-voltage lithium batteries. Solid State Ionics, 1999, 118: 179 ~185
[32] Y. Sun, Z. Wang, L. Chen, et al. Improved electrochemical performances of surface-modified spinel LiMn2O4 for long cycle life lithium-ion batteries. J. Electrochem. Soc., 2003, 150: A1294~A1298
[33] S.S. Zhang, K. Xu, T.R Jow. Electrochemical impedance study on the low temperature of Li-ion batteries. Electrochim. Acta, 2004, 49: 1057~1061
[34] G. Nagasubramanian. Electrical characteristics of 18650 Li-ion cells at low temperatures. J. Appl. Electrochem., 2001, 31: 99~104
[35] S.S. Zhang, K. Xu, T.R. Jow. The low temperature performance of Li-ion batteries. J. Power Sources, 2003, 115: 137~140
[36] J. Fan. On the discharge capability and its limiting factors of commercial 18650 Li-ion cell at low temperatures. J. Power Sources, 2003, 117: 170~178
[37] C.K. Huang, J.S. Sakamoto. The limits of low-temperature performance of Li-ion cells. J. Electrochem. Soc., 2000, 147: 2893~2896
[38] H.P. Lin, D. Chua, M. Salomon, et al. Low-temperature behavior of Li-ion cells. Electrochem. Solid-State Lett., 2001, 4: A71~A73
[39] S.S. Zhang, K. Xu, T.R. Jow. Low temperature performance of graphite electrode in Li-ion cells. Electrochim. Acta, 2002, 48: 241~246
[40] E.J. Plichta, W.K. Behl. A low-temperature electrolyte for lithium and lithium-ion batteries. J. Power Sources, 2000, 88: 192~196
[41] B.V. Ratnakumar, M.C. Smart, S. Surampudi. Effects of SEI on the kinetics of lithium intercalation. J. Power Sources, 2001, 97–98: 137~139
[42] M. Mohamedi, D. Takahashi, T. Itoh. Electrochemical stability of thin film LiMn2O4 cathode in organic electrolyte solutions with different compositions at 55 degrees C. Electrochim. Acta, 2002, 47: 3483~3489
[43] J. Vetter. Ageing mechanisms in lithium-ion batteries. J. Power Sources, 2005, 147: 269~281
[44] G. Nagasubramanian. Two- and three-electrode impedance studies on 18650 Li-ion cells. J. Power Sources, 2000, 87: 226~229
[45] J.Y. Song. Two- and three-electrode impedance spectroscopy of lithium-ion batteries. J. Power Sources, 2002, 111: 255~267
[46] V.G. Kumar, N. Munichandraiah, A.K. Shukla. Electrode impedance parameters and internal resistance of a sealed LiC/Li1-xCoO2 lithium-ion rechargeable battery. J. Appl. Electrochem., 1997, 27: 43~49
[2] 吴宇平, 万春容, 姜长印, 等. 锂离子二次电池. 北京: 化学工业出版社, 2002
[3] M. Yoshio, H. Tanaka, K. Tominaya, et al. J. Electrochem. Soc., 1992, 40: 347~353
[4] G.X. Wang, S. Zhong. Synthesis and characterization of LiNiO2 compounds as cathodes for rechargeable lithium batteries. J. Power Sources, 1998, 76: 141~146
[5] Kweon, Ho-Jin, Kim. Modification of LixNi1?yCoyO2 by applying a surface coating of MgO. J. Power Sources, 2000, 88: 255~261
[6] A. Rougier, P. Gravereau, C. Delmas. Optimization of the composition of the Li1–zNi1+zO2 electrode materials: structural, magnetic, and electrochemical studies. J. Electrochem. Soc., 1996, 143: 1168~1175
[7] M. Yoshio, H. Nakamura. Lithiated manganese dioxide, Li0.33MnO2, as a 3V cathode for lithium batteries. Electrochim. Acta, 1999, 45: 273~283
[8] B. Banov, A. Momchilov. Li0.33MnO2-cathode material for secondary lithium batteries. J. Power Sources, 1999, 82: 562~565
[9] Y. Juji, Y. Mikya, JP0837027, 1996
[10] Y. Matsumura, S. Wang, J. Mondori. Mechanism leading to irreversible capacity loss in Li ion rechargeable batteries. J. Electrochem. Soc., 1995, 142: 2914~2918
[11] I. Kootschau, M.N. Richard, J.R. Dahn. Orthorhombic LiMnO2 as a high capacity cathode for Li-ion cells. J. Electrochem. Soc., 1995, 142: 2906~2910
[12] 周恒辉, 慈云祥. 锂离子电池阴极材料. 化学进展, 1998, 3: 85~91
[13] M.M. Thackeray. Structure Considerations of layered and spinel lithiated oxides for lithium ion batteries. J. Electrochem. Soc., 1995, 142: 2558~2563
[14] H. Berg, H. Rundlov, J.O. Thomas. The LiMn2O4 to lambda-MnO2 phase transition studied by in situ neutron diffraction. Solid State Ionics, 2001, 144: 65 ~69
[15] W. Liu, G.C. Farrington, F. Chaput, et al. Synthesis and electrochemical studies of spinel phase LiMn2O4 cathode materials prepared by the pechini process. J. Electrochem. Soc., 1998, 143: 879~884
[16] A.S. Yu, H.Q. Wu. The electrochemical intercalation reaction of lithium into spinel phase [Mn2O4]. 1. thermodynamic behavior. Acta Chimica Sinica, 1994,52: 763-766
[17] M. Benaissa, M. Joseyacaman, T.D. Xiao, et al. Microstructural study of hollandite-type MnO2 nano-fibers. Appl. Phys. Lett., 1997, 70: 2120~2122
[18] 崔万秋, 杨丽芬. 锂离子电池阴极材料 Li1+xMn2O4 的合成与特性. 功能材料, 1998, 29: 378~380
[19] 吴晓梅, 杨清河. 电化学, 1998, 4: 365~371
[20] I. Hiroshi, S. Kyuta. JP0831459, 1996
[21] S.T. Myung, H.T. Chung. Effect of mixing sequence on the electrode characteristics of lithium-ion rechargeable batteries. J. Power Sources, 1999, 84: 32~38
[22] K.T. Hwang, W.S. Um,et al. Powder synthesis and electrochemical properties of LiMn2O4 prepared by an emulsion-drying method. J. Power Sources, 1998, 74: 169~174
[23] E. Rossen, J.N. Reimers, J.R. Dahn. Synthesis and electrochemistry of spinel LT---LiCoO2 Solid State Ionics,1993, 62: 53~60
[24] R.J. Gummow, A. Kock, M.M. Thackeray. Improved capacity retention in rechargeable 4V lithium manganese oxide (spinel) cells. Solid State Ionics, 1994, 69: 59~62
[25] 孔海霞. 电化学阻抗谱图法 TiO2 薄膜光电极能带结构和催化活性研究: [硕士学位论文]. 太原: 太原理工大学应用化学系, 2004
[26] 曹楚南, 张鉴清. 电化学阻抗谱导论. 北京: 科学出版社, 2002
[27] 吴宇平, 万春容, 姜长印, 等. 锂离子二次电池. 北京: 化学工业出版社, 2002. 32~33
[28] 吴宇平, 万春容, 姜长印, 等. 锂离子二次电池. 北京: 化学工业出版社, 2002. 34~40
[29] L. Kavan, M. Gr?izel, J. Rathousk, et al. Nanocrystalline TiO2 (anatase) electrodes: Surface morphology, adsorption, and electrochemical properties. J. Electrochem. Soc., 1996, 143: 394~400
[30] M. Wagemaker, A.A. van Well, G.J. Kearley, et al. The life and times of lithium in anatase TiO2. Solid State Ionics, 2004, 175: 191~193
[31] L. Hernan, J. Morales, L. Sanchez, et al. Use of Li-M-Mn-O [M = Co, Cr, Ti] spinels prepared by a sol-gel method as cathodes in high-voltage lithium batteries. Solid State Ionics, 1999, 118: 179 ~185
[32] Y. Sun, Z. Wang, L. Chen, et al. Improved electrochemical performances of surface-modified spinel LiMn2O4 for long cycle life lithium-ion batteries. J. Electrochem. Soc., 2003, 150: A1294~A1298
[33] S.S. Zhang, K. Xu, T.R Jow. Electrochemical impedance study on the low temperature of Li-ion batteries. Electrochim. Acta, 2004, 49: 1057~1061
[34] G. Nagasubramanian. Electrical characteristics of 18650 Li-ion cells at low temperatures. J. Appl. Electrochem., 2001, 31: 99~104
[35] S.S. Zhang, K. Xu, T.R. Jow. The low temperature performance of Li-ion batteries. J. Power Sources, 2003, 115: 137~140
[36] J. Fan. On the discharge capability and its limiting factors of commercial 18650 Li-ion cell at low temperatures. J. Power Sources, 2003, 117: 170~178
[37] C.K. Huang, J.S. Sakamoto. The limits of low-temperature performance of Li-ion cells. J. Electrochem. Soc., 2000, 147: 2893~2896
[38] H.P. Lin, D. Chua, M. Salomon, et al. Low-temperature behavior of Li-ion cells. Electrochem. Solid-State Lett., 2001, 4: A71~A73
[39] S.S. Zhang, K. Xu, T.R. Jow. Low temperature performance of graphite electrode in Li-ion cells. Electrochim. Acta, 2002, 48: 241~246
[40] E.J. Plichta, W.K. Behl. A low-temperature electrolyte for lithium and lithium-ion batteries. J. Power Sources, 2000, 88: 192~196
[41] B.V. Ratnakumar, M.C. Smart, S. Surampudi. Effects of SEI on the kinetics of lithium intercalation. J. Power Sources, 2001, 97–98: 137~139
[42] M. Mohamedi, D. Takahashi, T. Itoh. Electrochemical stability of thin film LiMn2O4 cathode in organic electrolyte solutions with different compositions at 55 degrees C. Electrochim. Acta, 2002, 47: 3483~3489
[43] J. Vetter. Ageing mechanisms in lithium-ion batteries. J. Power Sources, 2005, 147: 269~281
[44] G. Nagasubramanian. Two- and three-electrode impedance studies on 18650 Li-ion cells. J. Power Sources, 2000, 87: 226~229
[45] J.Y. Song. Two- and three-electrode impedance spectroscopy of lithium-ion batteries. J. Power Sources, 2002, 111: 255~267
[46] V.G. Kumar, N. Munichandraiah, A.K. Shukla. Electrode impedance parameters and internal resistance of a sealed LiC/Li1-xCoO2 lithium-ion rechargeable battery. J. Appl. Electrochem., 1997, 27: 43~49