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Preparation and electrochemical properties of submicron LiNi0.6Co0.2Mn0.2O2 as cathode material for lithium ion batteries
Available online at www.sciencedirect.com
Scripta Materialia 65 (2011) 1077–1080 www.elsevier.com/locate/scriptamat
Preparation and electrochemical properties of submicron LiNi0.6Co0.2Mn0.2O2 as cathode material for lithium ion batteries Peng Yue, Zhixing Wang,⇑ Wenjie Peng, Lingjun Li, Huajun Guo, Xinhai Li, Qiyang Hu and Yunhe Zhang School of Metallurgical Science and Engineering, Central South University, Changsha 410083, People’s Republic of China Received 7 July 2011; accepted 14 September 2011 Available online 18 September 2011
Submicron LiNi0.6Co0.2Mn0.2O2 as a cathode material for lithium-ion batteries was prepared by a spray drying assisted solidstate method. The crystal structure, morphology and electrochemical properties of LiNi0.6Co0.2Mn0.2O2 were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, energy-dispersive spectroscopy and charge– discharge testing. Single-phase layered LiNi0.6Co0.2Mn0.2O2 was obtained. The material delivered a reversible charge/discharge capacity of 179.8 mAh g 1 at C/10, and showed excellent cycling performance and rate capability. Ó 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: LiNi0.6Co0.2Mn0.2O2; Layered structures; Electrochemical properties; Lithium-ion batteries
Lithium-ion batteries have proved to be the best energy-storage device found to date for portable electronic products and show great promise for application in hybrid electric vehicles and electric vehicles [1,2]. In comparison with commercial LiCoO2, the LiNi1 2xCoxMnxO2 series, which integrates features of LiCoO2, LiNiO2 and LiMnO2, have attracted much attention for its high capacity, low cost, good cycling stability and safety [3,4]. It is well known that the electrochemical properties of a cathode strongly depend on the method used to synthesize it, which affects the crystallinity, phase purity, particle morphology and cation mixing in the structure of cathode materials [5,6]. Commercial cathode materials in lithium-ion batteries are synthesized via conventional solid-state methods. However, it is difficult to control the morphology and element distribution of cathode materials synthesized by solid-state methods. Thus, many different approaches (e.g. sol–gel method [7], co-precipitation method [8]) are used to prepare fine-sized cathode materials with controlled morphologies. Spray drying is a useful method for the synthesis of cathode materials by which homogeneous precursor with element mixing at the atomic level could be easily obtained [9]. In this regard, we combined spray drying with a solid-state method to prepare LiNi0.6Co0.2
⇑ Corresponding
author. [email protected]
Tel./fax:
+86
731
88836633; e-mail:
Mn0.2O2. The as-prepared LiNi0.6Co0.2Mn0.2O2 possesses a well-developed layered crystalline structure and excellent electrochemical properties. Submicron LiNi0.6Co0.2Mn0.2O2 was prepared as follows. Stoichiometric amounts of Ni(CH3COO)24H2O, Mn(CH3COO)24H2O, Co(CH3COO)24H2O were dissolved in citric acid solution at a molar ratio of 3:1:1 to obtain the first solution. Then, NH3H2O was dripped into this solution in order to adjust the pH to 6–7. The resulting solution was dried to form a dry mixed precursor using a spray-drying instrument to produce a homogeneous precursor. The as-prepared precursor was initially decomposed at 400 °C in air, and then ground with LiOHH2O (7% molar ratio of lithium is in excess in order to compensate for any possible loss) in an agate mortar and annealed at 900 °C for 15 h. The material was analyzed by scanning electron microscopy (SEM; JEOL, JSM-5600LV), and transmission electron microscopy (TEM) combined with energydispersive spectrometry (EDS) using a Tecnai G2 20ST. Powder X-ray diffraction (XRD, Rint-2000, Rigaku) using Cu Ka radiation was employed to determine the structure of the synthesized material. The chemical composition of the synthesized material was determined by inductively coupled plasma spectrometry (ICP; IRIS intrepid XSP, Thermo Electron Corporation). The electrochemical properties were measured using a CR2025 coin-type cell. The working cathode consisted
1359-6462/$ - see front matter Ó 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.scriptamat.2011.09.020
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P. Yue et al. / Scripta Materialia 65 (2011) 1077–1080
Figure 1. XRD pattern of the submicron LiNi0.6Co0.2Mn0.2O2 material.
Figure 2. SEM image (a) and TEM image (b) of the submicron LiNi0.6Co0.2Mn0.2O2 material; EDS maps of (c) Ni, (d) Co and (e) Mn for the submicron LiNi0.6Co0.2Mn0.2O2 material.
P. Yue et al. / Scripta Materialia 65 (2011) 1077–1080
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Figure 3. The initial charge–discharge curves at varying rates (a), cycling performance (b) and CV curves between 2.8 and 4.3 V (c) of the submicron LiNi0.6Co0.2Mn0.2O2 material.
of 80 wt.% active material, 10 wt.% acetylene black as conducting agent and 10 wt.% poly (vinylidene fluoride) as binder. A lithium metal foil was used as anode. A polypropylene microporous film was used as the separator. LiPF6 (1 M) in a 1:1:1 (v/v/v) mixture of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and ethylene carbonate (EC) was used as electrolyte. Assembly of cells was carried out in a dry Ar-filled glovebox. The charge–discharge performance was carried out using a battery testing system (NEWARE battery cycler), between 2.8 and 4.3 V vs. a Li/Li+ electrode at room temperature. Figure 1 shows the XRD pattern of the submicron LiNi0.6Co0.2Mn0.2O2 material. The lattice parameters inserted in Figure 1 were calculated by the least-squares method from the XRD pattern. It is found that all diffraction peaks can be indexed on the basis of a layered 3m), and no exstructure of a-NaFeO2 (space group: R tra diffraction peaks from related secondary phases or impurities exist. The lattice parameters a and c are given ˚ , respectively, which are similar as 2.8714 and 14.2191 A ˚ and to the values reported previously (i.e. a = 2.866 A
˚ [10]; and a = 2.875 A ˚ and c = 14.231 A ˚ c = 14.195 A [11]). The degree of splitting of the doublets (0 0 6)/ (1 0 2) and (1 0 8)/(1 1 0), as well as the ratios of c/a and I(003)/I(104), have been used as a measurement of the structural ordering of the materials [12]. The intensity ratio of I(003)/I(104) is a sensitive parameter for determining the cation distribution in the lattice; a value lower than 1.2 indicates a high degree of cation mixing, due primarily to the occupancy of other ions in the lithium region, and the higher the ratio is, the lower the level of cation mixing and the more hexagonal the structure [13,14]. In addition, the c/a ratio of this material is greater than 4.9, a value that generally represents a material with layered characteristics [15]. Moreover, desirable cation ordering is manifested by the clear splitting of the (0 0 6)/(1 0 2) and (1 0 8)/(1 1 0) peaks, as seen in Figure 1. Thus, this layered LiNi0.6Co0.2Mn0.2O2 material can be expected to have good electrochemical properties. Figure 2 presents the SEM (a), TEM (b) and EDS (c, d, e) mapping of the submicron LiNi0.6Co0.2Mn0.2O2 material. As seen in Figure 2a, b, the LiNi0.6Co0.2
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P. Yue et al. / Scripta Materialia 65 (2011) 1077–1080
Table 1. Fade rate at various discharge rates. Discharge rate (C)
Discharge capacity (mAh g 1)
Fading rate per cycle (mAh g 1)
0.2 1 2 5
172.7 160.8 150.5 125.4
0.18 0.25 0.34 0.42
(0.10%) (0.16%) (0.22%) (0.33%)
The fade rate was calculated according to the equations: (Qn Qm)/N (mAh g 1 cycle) and [(Qn Qm)/QnN] 100%, where Qn, Qm are the discharge capacities observed at the nth and mth cycle, and N is the number of cycles.
Mn0.2O2 material shows a near-spherical shape with submicron size (the average particle size is about 400 nm–1 lm). EDS elemental mappings (Fig. 2c–e) show a uniform distribution of Ni, Co and Mn, consistent with the LiNi0.6Co0.2Mn0.2O2 phase purity determined by XRD. ICP was employed to measure the final elemental ratio in the sample. The atomic ratio of Li:Ni:Co:Mn in the LiNi0.6Co0.2Mn0.2O2 material is determined to be 1.02:5.997:1.999:2.004, which is nearly equal to the determined stoichiometric ratio. Figure 3a illustrates the initial charge–discharge curves of the submicron LiNi0.6Co0.2Mn0.2O2 material. The initial charge and discharge capacities at C/10 (16 mA g 1) are 211.5 and 179.8 mAh g 1, respectively, in the voltage range of 2.8–4.3 V. The rates of discharge capacities corresponding to C/10, C/5, C/2, 1C, 2C and 3C are 179.8, 172.7, 167.8, 160.8, 150.5 and 135.6 mAh g 1, respectively. Even when discharged at 5C, a capacity as high as 125.4 mAh g 1 is achieved, indicating that the method employed in this study achieves excellent rate capability. Figure 3b and Table 1 show the cycling performance of the submicron LiNi0.6Co0.2Mn0.2O2 material and the fade rate of the capacity at various discharge rates. The discharge capacities of LiNi0.6Co0.2Mn0.2O2 at C/5 are 172.7 and 169.2 mAh g 1 on the 1st and 20th cycle, respectively. For the 1C rate, the discharge capacity is 150.6 mAh g 1 after 40 cycles and retains 93.7% of its original value. In order to test the cycling performance at high current density, material was discharged at 2C and 5C. The retention of material at 2C and 5C are 91% and 86.6%, respectively. It can be concluded that the capacity of the submicron LiNi0.6Co0.2Mn0.2O2 basically possesses better retention, and fades rapidly at higher rates. Overall, the high discharge capacity and stable cycling performance of the submicron LiNi0.6Co0.2Mn0.2O2 can be attributed to its well-defined structure. The CV curves of the submicron LiNi0.6Co0.2Mn0.2O2 for the first three cycles are shown in Figure 3c. The voltage was scanned from 2.8 to 4.3 V with a scan rate of 0.1 mV s 1. The LiNi0.6Co0.2Mn0.2O2 material exhibits only one redox couple in CV, which means that multiphase reactions during electrochemical cycling do not occur in the range of 2.8–4.3 V, in particular the
Mn3+/Mn4+ redox-reaction peaks in the 3 V region [16]. In the first cycle, a pair of redox peaks located at 3.90 V/3.71 V was observed. During the subsequent cycles, the oxidation peak shifts to a lower voltage of 3.81 V with lower intensity and remains steady, while the reduction peaks remained unchanged. The stable small gap (0.1 V) of the redox reaction peaks from the second cycle indicates the high electrochemical activity and cycling stability of the submicron LiNi0.6Co0.2 Mn0.2O2 [17]. In summary, submicron LiNi0.6Co0.2Mn0.2O2 as a cathode material for lithium-ion batteries was prepared by a spray drying assisted solid-state method. Singlephase LiNi0.6Co0.2Mn0.2O2 with a layered structure (a-NaFeO2-type structure, space group: R 3m) was obtained. The submicron LiNi0.6Co0.2Mn0.2O2 exhibited excellent rate capability, with 125.4 mAh g 1 delivered at 5C, and 179.8 mAh g 1 at C/10. The capacity retention upon cycling at 1C, 2C and 5C were 93.7%, 91% and 86.6%, respectively, after the 40th discharge. Further research is being carried out to optimize the crystal structure and to reduce the irreversible loss of capacity. This work was financially sponsored by the National Basic Research Program of China (973 Program, Contract No. 2007CB613607). [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]
J.M. Tarascon, M. Armand, Nature 414 (2001) 359. M.S. Whittingham, Chem. Rev. 104 (2004) 4271. S.H. Ju, Y.C. Kang, J. Power Sources 178 (2008) 387. W.B. Luo, X.H. Li, J.R. Dahn, Chem. Mater. 22 (2010) 5065. P.S. Whitfield, I.J. Davidson, L.M.D. Cranswick, I.P. Swainson, P.W. Stephens, Solid State Ionics 176 (2005) 463. B. Lin, Z.Y. Wen, Z.H. Gu, S.H. Huang, J. Power Sources 175 (2008) 564. R. Santhanam, B. Rambabu, J. Power Sources 195 (2010) 4313. W.B. Luo, F. Zhou, X.M. Zhao, Z.H. Lu, X.H. Li, J.R. Dahn, Chem. Mater. 22 (2010) 1164. S.H. Park, S.W. Oh, S.T. Myung, Y.C. Kang, Y.K. Sun, Solid State Ionics 176 (2005) 481. H. Cao, Y. Zhang, J. Zhang, B.J. Xia, Solid State Ionics 177 (2006) 3303. H. Cao, Y. Zhang, J. Zhang, B.J. Xia, Solid State Ionics 176 (2005) 1207. S.W. Oh, S.H. Park, C.W. Park, Y.K. Sun, Solid State Ionics 171 (2004) 167. M. Wang, Y.B. Chen, F. Wu, Y.F. Su, L. Chen, D.L. Wang, Electrochim. Acta 55 (2010) 8815. Y.M. Choi, S.I. Pyun, S.I. Moon, Solid State Ionics 89 (1996) 43. F. Wu, M. Wang, Y.F. Su, L.Y. Bao, S. Chen, J. Power Source 195 (2010) 2900. J.M. Paulsen, C.L. Thomas, J.R. Dahn, J. Electrochem. Soc. 147 (2000) 861. Z.D. Huang, X.M. Liu, B. Zhao, S.W. Oh, P.C. Ma, J.K. Kim, Scripta Mater. 64 (2011) 122.
Scripta Materialia 65 (2011) 1077–1080 www.elsevier.com/locate/scriptamat
Preparation and electrochemical properties of submicron LiNi0.6Co0.2Mn0.2O2 as cathode material for lithium ion batteries Peng Yue, Zhixing Wang,⇑ Wenjie Peng, Lingjun Li, Huajun Guo, Xinhai Li, Qiyang Hu and Yunhe Zhang School of Metallurgical Science and Engineering, Central South University, Changsha 410083, People’s Republic of China Received 7 July 2011; accepted 14 September 2011 Available online 18 September 2011
Submicron LiNi0.6Co0.2Mn0.2O2 as a cathode material for lithium-ion batteries was prepared by a spray drying assisted solidstate method. The crystal structure, morphology and electrochemical properties of LiNi0.6Co0.2Mn0.2O2 were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, energy-dispersive spectroscopy and charge– discharge testing. Single-phase layered LiNi0.6Co0.2Mn0.2O2 was obtained. The material delivered a reversible charge/discharge capacity of 179.8 mAh g 1 at C/10, and showed excellent cycling performance and rate capability. Ó 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: LiNi0.6Co0.2Mn0.2O2; Layered structures; Electrochemical properties; Lithium-ion batteries
Lithium-ion batteries have proved to be the best energy-storage device found to date for portable electronic products and show great promise for application in hybrid electric vehicles and electric vehicles [1,2]. In comparison with commercial LiCoO2, the LiNi1 2xCoxMnxO2 series, which integrates features of LiCoO2, LiNiO2 and LiMnO2, have attracted much attention for its high capacity, low cost, good cycling stability and safety [3,4]. It is well known that the electrochemical properties of a cathode strongly depend on the method used to synthesize it, which affects the crystallinity, phase purity, particle morphology and cation mixing in the structure of cathode materials [5,6]. Commercial cathode materials in lithium-ion batteries are synthesized via conventional solid-state methods. However, it is difficult to control the morphology and element distribution of cathode materials synthesized by solid-state methods. Thus, many different approaches (e.g. sol–gel method [7], co-precipitation method [8]) are used to prepare fine-sized cathode materials with controlled morphologies. Spray drying is a useful method for the synthesis of cathode materials by which homogeneous precursor with element mixing at the atomic level could be easily obtained [9]. In this regard, we combined spray drying with a solid-state method to prepare LiNi0.6Co0.2
⇑ Corresponding
author. [email protected]
Tel./fax:
+86
731
88836633; e-mail:
Mn0.2O2. The as-prepared LiNi0.6Co0.2Mn0.2O2 possesses a well-developed layered crystalline structure and excellent electrochemical properties. Submicron LiNi0.6Co0.2Mn0.2O2 was prepared as follows. Stoichiometric amounts of Ni(CH3COO)24H2O, Mn(CH3COO)24H2O, Co(CH3COO)24H2O were dissolved in citric acid solution at a molar ratio of 3:1:1 to obtain the first solution. Then, NH3H2O was dripped into this solution in order to adjust the pH to 6–7. The resulting solution was dried to form a dry mixed precursor using a spray-drying instrument to produce a homogeneous precursor. The as-prepared precursor was initially decomposed at 400 °C in air, and then ground with LiOHH2O (7% molar ratio of lithium is in excess in order to compensate for any possible loss) in an agate mortar and annealed at 900 °C for 15 h. The material was analyzed by scanning electron microscopy (SEM; JEOL, JSM-5600LV), and transmission electron microscopy (TEM) combined with energydispersive spectrometry (EDS) using a Tecnai G2 20ST. Powder X-ray diffraction (XRD, Rint-2000, Rigaku) using Cu Ka radiation was employed to determine the structure of the synthesized material. The chemical composition of the synthesized material was determined by inductively coupled plasma spectrometry (ICP; IRIS intrepid XSP, Thermo Electron Corporation). The electrochemical properties were measured using a CR2025 coin-type cell. The working cathode consisted
1359-6462/$ - see front matter Ó 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.scriptamat.2011.09.020
1078
P. Yue et al. / Scripta Materialia 65 (2011) 1077–1080
Figure 1. XRD pattern of the submicron LiNi0.6Co0.2Mn0.2O2 material.
Figure 2. SEM image (a) and TEM image (b) of the submicron LiNi0.6Co0.2Mn0.2O2 material; EDS maps of (c) Ni, (d) Co and (e) Mn for the submicron LiNi0.6Co0.2Mn0.2O2 material.
P. Yue et al. / Scripta Materialia 65 (2011) 1077–1080
1079
Figure 3. The initial charge–discharge curves at varying rates (a), cycling performance (b) and CV curves between 2.8 and 4.3 V (c) of the submicron LiNi0.6Co0.2Mn0.2O2 material.
of 80 wt.% active material, 10 wt.% acetylene black as conducting agent and 10 wt.% poly (vinylidene fluoride) as binder. A lithium metal foil was used as anode. A polypropylene microporous film was used as the separator. LiPF6 (1 M) in a 1:1:1 (v/v/v) mixture of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and ethylene carbonate (EC) was used as electrolyte. Assembly of cells was carried out in a dry Ar-filled glovebox. The charge–discharge performance was carried out using a battery testing system (NEWARE battery cycler), between 2.8 and 4.3 V vs. a Li/Li+ electrode at room temperature. Figure 1 shows the XRD pattern of the submicron LiNi0.6Co0.2Mn0.2O2 material. The lattice parameters inserted in Figure 1 were calculated by the least-squares method from the XRD pattern. It is found that all diffraction peaks can be indexed on the basis of a layered 3m), and no exstructure of a-NaFeO2 (space group: R tra diffraction peaks from related secondary phases or impurities exist. The lattice parameters a and c are given ˚ , respectively, which are similar as 2.8714 and 14.2191 A ˚ and to the values reported previously (i.e. a = 2.866 A
˚ [10]; and a = 2.875 A ˚ and c = 14.231 A ˚ c = 14.195 A [11]). The degree of splitting of the doublets (0 0 6)/ (1 0 2) and (1 0 8)/(1 1 0), as well as the ratios of c/a and I(003)/I(104), have been used as a measurement of the structural ordering of the materials [12]. The intensity ratio of I(003)/I(104) is a sensitive parameter for determining the cation distribution in the lattice; a value lower than 1.2 indicates a high degree of cation mixing, due primarily to the occupancy of other ions in the lithium region, and the higher the ratio is, the lower the level of cation mixing and the more hexagonal the structure [13,14]. In addition, the c/a ratio of this material is greater than 4.9, a value that generally represents a material with layered characteristics [15]. Moreover, desirable cation ordering is manifested by the clear splitting of the (0 0 6)/(1 0 2) and (1 0 8)/(1 1 0) peaks, as seen in Figure 1. Thus, this layered LiNi0.6Co0.2Mn0.2O2 material can be expected to have good electrochemical properties. Figure 2 presents the SEM (a), TEM (b) and EDS (c, d, e) mapping of the submicron LiNi0.6Co0.2Mn0.2O2 material. As seen in Figure 2a, b, the LiNi0.6Co0.2
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P. Yue et al. / Scripta Materialia 65 (2011) 1077–1080
Table 1. Fade rate at various discharge rates. Discharge rate (C)
Discharge capacity (mAh g 1)
Fading rate per cycle (mAh g 1)
0.2 1 2 5
172.7 160.8 150.5 125.4
0.18 0.25 0.34 0.42
(0.10%) (0.16%) (0.22%) (0.33%)
The fade rate was calculated according to the equations: (Qn Qm)/N (mAh g 1 cycle) and [(Qn Qm)/QnN] 100%, where Qn, Qm are the discharge capacities observed at the nth and mth cycle, and N is the number of cycles.
Mn0.2O2 material shows a near-spherical shape with submicron size (the average particle size is about 400 nm–1 lm). EDS elemental mappings (Fig. 2c–e) show a uniform distribution of Ni, Co and Mn, consistent with the LiNi0.6Co0.2Mn0.2O2 phase purity determined by XRD. ICP was employed to measure the final elemental ratio in the sample. The atomic ratio of Li:Ni:Co:Mn in the LiNi0.6Co0.2Mn0.2O2 material is determined to be 1.02:5.997:1.999:2.004, which is nearly equal to the determined stoichiometric ratio. Figure 3a illustrates the initial charge–discharge curves of the submicron LiNi0.6Co0.2Mn0.2O2 material. The initial charge and discharge capacities at C/10 (16 mA g 1) are 211.5 and 179.8 mAh g 1, respectively, in the voltage range of 2.8–4.3 V. The rates of discharge capacities corresponding to C/10, C/5, C/2, 1C, 2C and 3C are 179.8, 172.7, 167.8, 160.8, 150.5 and 135.6 mAh g 1, respectively. Even when discharged at 5C, a capacity as high as 125.4 mAh g 1 is achieved, indicating that the method employed in this study achieves excellent rate capability. Figure 3b and Table 1 show the cycling performance of the submicron LiNi0.6Co0.2Mn0.2O2 material and the fade rate of the capacity at various discharge rates. The discharge capacities of LiNi0.6Co0.2Mn0.2O2 at C/5 are 172.7 and 169.2 mAh g 1 on the 1st and 20th cycle, respectively. For the 1C rate, the discharge capacity is 150.6 mAh g 1 after 40 cycles and retains 93.7% of its original value. In order to test the cycling performance at high current density, material was discharged at 2C and 5C. The retention of material at 2C and 5C are 91% and 86.6%, respectively. It can be concluded that the capacity of the submicron LiNi0.6Co0.2Mn0.2O2 basically possesses better retention, and fades rapidly at higher rates. Overall, the high discharge capacity and stable cycling performance of the submicron LiNi0.6Co0.2Mn0.2O2 can be attributed to its well-defined structure. The CV curves of the submicron LiNi0.6Co0.2Mn0.2O2 for the first three cycles are shown in Figure 3c. The voltage was scanned from 2.8 to 4.3 V with a scan rate of 0.1 mV s 1. The LiNi0.6Co0.2Mn0.2O2 material exhibits only one redox couple in CV, which means that multiphase reactions during electrochemical cycling do not occur in the range of 2.8–4.3 V, in particular the
Mn3+/Mn4+ redox-reaction peaks in the 3 V region [16]. In the first cycle, a pair of redox peaks located at 3.90 V/3.71 V was observed. During the subsequent cycles, the oxidation peak shifts to a lower voltage of 3.81 V with lower intensity and remains steady, while the reduction peaks remained unchanged. The stable small gap (0.1 V) of the redox reaction peaks from the second cycle indicates the high electrochemical activity and cycling stability of the submicron LiNi0.6Co0.2 Mn0.2O2 [17]. In summary, submicron LiNi0.6Co0.2Mn0.2O2 as a cathode material for lithium-ion batteries was prepared by a spray drying assisted solid-state method. Singlephase LiNi0.6Co0.2Mn0.2O2 with a layered structure (a-NaFeO2-type structure, space group: R 3m) was obtained. The submicron LiNi0.6Co0.2Mn0.2O2 exhibited excellent rate capability, with 125.4 mAh g 1 delivered at 5C, and 179.8 mAh g 1 at C/10. The capacity retention upon cycling at 1C, 2C and 5C were 93.7%, 91% and 86.6%, respectively, after the 40th discharge. Further research is being carried out to optimize the crystal structure and to reduce the irreversible loss of capacity. This work was financially sponsored by the National Basic Research Program of China (973 Program, Contract No. 2007CB613607). [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]
J.M. Tarascon, M. Armand, Nature 414 (2001) 359. M.S. Whittingham, Chem. Rev. 104 (2004) 4271. S.H. Ju, Y.C. Kang, J. Power Sources 178 (2008) 387. W.B. Luo, X.H. Li, J.R. Dahn, Chem. Mater. 22 (2010) 5065. P.S. Whitfield, I.J. Davidson, L.M.D. Cranswick, I.P. Swainson, P.W. Stephens, Solid State Ionics 176 (2005) 463. B. Lin, Z.Y. Wen, Z.H. Gu, S.H. Huang, J. Power Sources 175 (2008) 564. R. Santhanam, B. Rambabu, J. Power Sources 195 (2010) 4313. W.B. Luo, F. Zhou, X.M. Zhao, Z.H. Lu, X.H. Li, J.R. Dahn, Chem. Mater. 22 (2010) 1164. S.H. Park, S.W. Oh, S.T. Myung, Y.C. Kang, Y.K. Sun, Solid State Ionics 176 (2005) 481. H. Cao, Y. Zhang, J. Zhang, B.J. Xia, Solid State Ionics 177 (2006) 3303. H. Cao, Y. Zhang, J. Zhang, B.J. Xia, Solid State Ionics 176 (2005) 1207. S.W. Oh, S.H. Park, C.W. Park, Y.K. Sun, Solid State Ionics 171 (2004) 167. M. Wang, Y.B. Chen, F. Wu, Y.F. Su, L. Chen, D.L. Wang, Electrochim. Acta 55 (2010) 8815. Y.M. Choi, S.I. Pyun, S.I. Moon, Solid State Ionics 89 (1996) 43. F. Wu, M. Wang, Y.F. Su, L.Y. Bao, S. Chen, J. Power Source 195 (2010) 2900. J.M. Paulsen, C.L. Thomas, J.R. Dahn, J. Electrochem. Soc. 147 (2000) 861. Z.D. Huang, X.M. Liu, B. Zhao, S.W. Oh, P.C. Ma, J.K. Kim, Scripta Mater. 64 (2011) 122.