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Hydrothermal synthesis and electrochemistry of a manganese vanadium oxide, γ-MnV2O5
www.elsevier.nl/locate/elecom Electrochemistry Communications 1 (1999) 564–567
Hydrothermal synthesis and electrochemistry of a manganese vanadium oxide, g-MnV2O5 Fan Zhang, Peter Zavalij, M. Stanley Whittingham * Materials Research Center and Chemistry Department, State University of New York at Binghamton, Binghamton, NY 13902-6016, USA Received 3 September 1999; accepted 13 September 1999
Abstract A new manganese vanadium oxide MnV2O5 has been synthesized using a mild hydrothermal reaction. MnV2O5 crystallizes in the ˚ , bs3.5825(1) A ˚ , cs11.2653(2) A ˚ . It is isostructural to g-LiV2O5. It reacts orthorhombic system, space group Pnma, as9.7585(2) A readily and reversibly with lithium, with a stable capacity but with a large polarization. q1999 Elsevier Science S.A. All rights reserved. Keywords: Hydrothermal synthesis; Vanadium oxide; Manganese; Rietveld analysis; Lithium cathode
1. Introduction There has been much interest in the last two decades in layered manganese and vanadium oxides and their intercalation chemistry because of their potential use as secondary cathode materials for advanced lithium batteries [1–7]. A wide range of vanadium oxides has been synthesized by mild hydrothermal methods [8] and of these the layered LixV2O4 [9] and the double-sheet d-V2O5 structure [10] both show promising electrochemical behavior in lithium cells. Layered manganates have also been prepared using hydrothermal methods, for example, by the decomposition of aqueous permanganate solutions [3]. Of the alkali manganates, MxMnO2 where M is Li, Na, K or Rb, the potassium compound showed [4] the best reversibility; KxMnO2 prepared at elevated temperatures showed similar behavior [11]. Potassium stabilizes the structure by forming pillars between the MnO2 layers, thereby preventing the cubic close packing of the oxygen atoms required for conversion to the spinel-like lattice [12,13]. Replacement of the potassium pillars by a redoxactive pillar ion such as vanadium would be attractive, leading to a higher capacity. We recently reported the synthesis of such a pillared structure, Zn3(OH)2(V2O7)PH2O, which contains zinc oxyhydroxide sheets pillared by vanadium oxide pillars [14]. Our goal was to form such a structure with manganese(IV) oxide layers and vanadium(V) oxide pillars. Such pillars would * Corresponding author. Tel./fax: q1-607-777-4623; e-mail: stanwhit@ binghamton.edu
also contain vanadium in square pyramidal or octahedral coordination, as VO4 tetrahedra are not readily reducible without destruction of the lattice polyhedra. We have thus investigated the formation of vanadium-pillared manganese oxides through a systematic study of the hydrothermal reactions between vanadium and manganese oxides in the presence of organic structure-directing agents. Besides the known phases MnV2O6 and Mn2V2O7, we have isolated at least four other phases including a pipe-structure Mn7(OH)3(VO4)4 [15], d-MnxV2O5 and g-MnV2O5. This paper discusses the synthesis and characterization of the g-MnV2O5 phase.
2. Experimental MnV2O5 was prepared by the hydrothermal treatment of V2O5 from Alfa, with MnSO4 powder and diethanolamine from Aldrich in a 1:1:2 molar ratio, respectively; the pH of this solution was 6.06. The reaction mixture was heated in a 125 ml Teflon-lined Parr reactor for 72 h at 455 K. The resulting dark green powder was filtered and dried in air. The pH of the solution after reaction was almost neutral, pHs6.13. X-ray powder diffraction was performed using Cu Ka radiation on a Scintag XDS2000 u–u diffractometer equipped with a Ge(Li) solid-state detector. The data were collected with a step of 0.028; 2u from 10 to 708 with an exposure of 30 s per step, and 2u from 70 to 1258 with an exposure of 45 s per step. TGA data were obtained on a Perkin-Elmer model TGA 7, FT-IR data on a Perkin-Elmer 1500 series,
1388-2481/99/$ - see front matter q1999 Elsevier Science S.A. All rights reserved. PII S 1 3 8 8 - 2 4 8 1 ( 9 9 ) 0 0 1 1 3 - 7
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Article: 123
F. Zhang et al. / Electrochemistry Communications 1 (1999) 564–567
and electron microscopy data on an Electroscan 2020 environmental scanning electron microscope. Initial electrochemical studies were conducted in lithium cells using 1.5 M LiPF6 in a 2:1 dimethyl carbonate/ethylcarbonate mixture as the electrolyte; the vanadium oxide was mixed with 10% carbon black and 10% Teflon powder, and hot pressed for 20 min at 4408F. A MacPile potentiostat was used to cycle the cells.
3. Results and discussion The manganese–vanadium compound was precipitated as well-formed dark brown large lathe-like sheets, as shown in Fig. 1. These sheets were around 1–2 mm thick, 10 mm across and 100 mm on an edge. Electron microprobe analysis showed that they contained manganese and vanadium in approximately a 1:2 ratio, and no sulfur was detected. The TGA analysis of this compound in oxygen is shown in Fig. 2. There is a 6% increase in weight from 380 to 5808C;
565
this gain corresponds to the addition of one oxygen atom. Xray analysis of the product after heating to 6508C in oxygen shows the formation of Mn(VO3)2 suggesting that the initial compound has the formula MnV2O5. The FT-IR spectrum showed a vanadyl group at 984 cmy1, with a sharp vanadium– oxygen band at 865.3 cmy1, and broad bands around 627.5, 570.8 and 395.3 cmy1. The X-ray diffraction pattern of the manganese compound (Fig. 3) was indexed in the orthorhombic system and space ˚ , bs group Pnma with cell parameters as9.7585(2) A ˚ ˚ 3.5825(1) A, cs11.2653(2) A. The crystal structure of MnV2O5 was determined from powder data using CSD crystallographic software [16]. Final Rietveld refinement was carried out using GSAS software [17]. The crystallographic data and atomic parameters are shown in Tables 1 and 2 respectively. This structure contains vanadium oxide sheets, made from VO5 square pyramids (SPs), between which the manganese ions reside. There are two independent vanadium atoms with similar square pyramidal (SP) coordination with doublebonded oxygen at the apex, whereas manganese has octahedral coordination. The interatomic distances are shown in Table 3. The vanadium SPs share edges to form two crystallographically independent chains along the b axis. The SPs alternate along the chain in up and down orientations. Unused corners of SP base are shared between different chains linking Table 1 Crystallographic data for g-MnV2O5
Fig. 1. Morphology of g-MnV2O5.
Chemical formula Space group ˚) a (A ˚) b (A ˚) c (A ˚ 3) Cell volume (A Density (g cmy3) Formula weight (g moly1) Formula units per cell Number of reflections Number of variables RBregg(F2) Rprof wRprof
MnV2O5 Pnma 9.7585(2) 3.58252(6) 11.2653(2) 393.83(1) 3.994 236.82 4 373 64 0.045 0.052 0.073
Table 2 Atomic parameters for g-MnV2O5 Atom
x/a
y/b
z/c
˚2 U(iso)=100/A
V1 V2 Mn O1 O2 O3 O4 O5
0.3737(2) 0.0559(2) 0.6704(1) 0.9638(4) 0.2814(5) 0.9262(5) 0.2453(6) 0.5704(6)
1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4
0.4984(1) 0.5951(1) 0.2801(1) 0.7186(4) 0.3778(4) 0.4587(4) 0.6342(4) 0.4517(4)
0.41(7) 0.32(8) 0.84(8) 0.33(9) 0.33(9) 0.33(9) 0.33(9) 0.33(9)
Fig. 2. TGA of g-MnV2O5 in oxygen at a heating rate of 38C miny1.
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Article: 123
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F. Zhang et al. / Electrochemistry Communications 1 (1999) 564–567
Fig. 3. Experimental (dotted), calculated (line) and difference (bottom) plots for g-MnV2O5. Vertical lines depict reflection positions.
Table 3 ˚ ) for g-MnV2O5 Interatomic distances (A V1 O2 O4 O5 O59 O50
V2 1.629(4) 1.978(5) 1.991(5) 1.955(2) 1.955(2)
O1 O3 O39 O30 O4
Mn 1.657(5) 1.990(5) 1.899(2) 1.899(2) 1.900(6)
O1 O19 O2 O4 O49 O5
2.324(3) 2.324(3) 2.083(4) 2.195(4) 2.195(4) 2.165(5)
them into a layer. The layers are stacked along the c axis. The apical oxygen atoms of SPs form octahedral cavities filled with manganese atoms (Fig. 4). It appears that the title compound is isostructural to the g-modification of LiV2O5 [18,19]. These two structures substantially differ only in ˚3 ˚ 3 for g-LiV2O5 and 393.8 A their cell volume, i.e., 373.2 A for MnV2O5. This difference is due to replacement of smaller Li with bigger Mn atoms between layers and therefore only ˚. the c axis increases significantly from 10.66 to 11.27 A The electrochemical behavior of the MnV2O5 phase is shown in Fig. 5. The initial cell voltage was 3.6 V. Initially over one lithium atom could be incorporated into the structure on discharge down to 2 V, after a charge to 4 V. This dropped to a steady value of 0.87 lithium atoms after three cycles, as shown in Fig. 6. The overall low discharge potential is related to the low oxidation states of the manganese and vanadium,
Tuesday Oct 26 09:36 AM
Fig. 4. Polyhedra representation of g-MnV2O5 crystal structure along the b axis. Vanadium square pyramids are shown in red color and manganese octahedra in blue.
nominally q2 and q4, respectively. A successful cathode will need a higher capacity with the manganese and vanadium ions reversed in position and in their highest oxidation states, e.g. VMn2O6.5.
StyleTag -- Journal: ELECOM (Electrochemistry Communications)
Article: 123
F. Zhang et al. / Electrochemistry Communications 1 (1999) 564–567
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Acknowledgements We thank the Department of Energy, Office of Transportation Technologies, through Lawrence Berkeley Laboratory for partial support of this work. We also thank Bill Blackburn for the electron microprobe studies.
References
Fig. 5. Electrochemical cycling of g-MnV2O5.
Fig. 6. Capacity of g-MnV2O5 on cycling.
4. Conclusions
A new manganese vanadium oxide g-MnV2O5 has been synthesized hydrothermally and its structure, isotypical to g-LiV2O5, was determined and refined by the Rietveld method. It is isostructural with g-LiV2O5, containing sheets of VO5 square pyramids between which manganese ions reside in octahedral sites. It intercalates one lithium atom in a reversible manner above 2 V.
Tuesday Oct 26 09:36 AM
[1] D.W. Murphy, P.A. Christian, F.J. Disalvo, J.N. Carides, J. Electrochem. Soc. 126 (1979) 497. [2] F. Leroux, D. Guyomard, Y. Piffard, Solid State Ionics 80 (1995) 307. [3] R. Chen, P. Zavalij, M.S. Whittingham, Chem. Mater. 8 (1996) 1275. [4] R. Chen, M.S. Whittingham, J. Electrochem. Soc. 144 (1997) L64. [5] C. Delmas, F. Capitaine, Abstr., 8th Int. Meet. Lithium Batteries 8 (1996) 470. [6] A.R. Armstrong, P.G. Bruce, Nature 381 (1996) 499. [7] A.R. Armstrong, R. Gitzendanner, A.D. Robertson, P.G. Bruce, Chem. Commun. (1998) 1833. [8] T.A. Chirayil, P.Y. Zavalij, M.S. Whittingham, Chem. Mater. 10 (1998) 2629. [9] T. Chirayil, P. Zavalij, M.S. Whittingham, J. Electrochem. Soc. 143 (1996) L193. [10] F. Zhang, P.Y. Zavalij, M.S. Whittingham, Mater. Res. Bull. 32 (1997) 701. [11] S.H. Kim, S.J. Kim, S.M. Oh, Chem. Mater. 11 (1999) 557. [12] M.S. Whittingham, R. Chen, T. Chirayil, P. Zavalij, Electrochem. Soc. Proc. 96-5 (1996) 76. [13] M.S. Whittingham, in: O. Yamamoto, M. Wakihara (Eds.), Lithium Batteries, Kodansha, Tokyo, 1998. [14] P.Y. Zavalij, F. Zhang, M.S. Whittingham, Acta Crystallogr., Sect. C 53 (1997) 1738. [15] F. Zhang, P.Y. Zavalij, M.S. Whittingham, J. Mater. Chem. 10 (1999) in press. [16] L.G. Akselrud, P.Y. Zavalii, Y.N. Grin, V.K. Pecharsky, B. Baumgartner, E. Wolfel, Mater. Sci. Forum 133–136 (1993) 335. [17] A.C. Larson, R.B. VonDreele, GSAS. General Structure Analysis System. User Guide, Los Alamos National Laboratory, Los Alamos, NM, USA, 1994. [18] D.N. Anderson, R.D. Willett, Acta Crystallogr., Sect. B 27 (1971) 1477. [19] J. Galy, J. Darriet, P. Hagenmuller, Chim. Miner. 8 (1971) 509.
StyleTag -- Journal: ELECOM (Electrochemistry Communications)
Article: 123
Hydrothermal synthesis and electrochemistry of a manganese vanadium oxide, g-MnV2O5 Fan Zhang, Peter Zavalij, M. Stanley Whittingham * Materials Research Center and Chemistry Department, State University of New York at Binghamton, Binghamton, NY 13902-6016, USA Received 3 September 1999; accepted 13 September 1999
Abstract A new manganese vanadium oxide MnV2O5 has been synthesized using a mild hydrothermal reaction. MnV2O5 crystallizes in the ˚ , bs3.5825(1) A ˚ , cs11.2653(2) A ˚ . It is isostructural to g-LiV2O5. It reacts orthorhombic system, space group Pnma, as9.7585(2) A readily and reversibly with lithium, with a stable capacity but with a large polarization. q1999 Elsevier Science S.A. All rights reserved. Keywords: Hydrothermal synthesis; Vanadium oxide; Manganese; Rietveld analysis; Lithium cathode
1. Introduction There has been much interest in the last two decades in layered manganese and vanadium oxides and their intercalation chemistry because of their potential use as secondary cathode materials for advanced lithium batteries [1–7]. A wide range of vanadium oxides has been synthesized by mild hydrothermal methods [8] and of these the layered LixV2O4 [9] and the double-sheet d-V2O5 structure [10] both show promising electrochemical behavior in lithium cells. Layered manganates have also been prepared using hydrothermal methods, for example, by the decomposition of aqueous permanganate solutions [3]. Of the alkali manganates, MxMnO2 where M is Li, Na, K or Rb, the potassium compound showed [4] the best reversibility; KxMnO2 prepared at elevated temperatures showed similar behavior [11]. Potassium stabilizes the structure by forming pillars between the MnO2 layers, thereby preventing the cubic close packing of the oxygen atoms required for conversion to the spinel-like lattice [12,13]. Replacement of the potassium pillars by a redoxactive pillar ion such as vanadium would be attractive, leading to a higher capacity. We recently reported the synthesis of such a pillared structure, Zn3(OH)2(V2O7)PH2O, which contains zinc oxyhydroxide sheets pillared by vanadium oxide pillars [14]. Our goal was to form such a structure with manganese(IV) oxide layers and vanadium(V) oxide pillars. Such pillars would * Corresponding author. Tel./fax: q1-607-777-4623; e-mail: stanwhit@ binghamton.edu
also contain vanadium in square pyramidal or octahedral coordination, as VO4 tetrahedra are not readily reducible without destruction of the lattice polyhedra. We have thus investigated the formation of vanadium-pillared manganese oxides through a systematic study of the hydrothermal reactions between vanadium and manganese oxides in the presence of organic structure-directing agents. Besides the known phases MnV2O6 and Mn2V2O7, we have isolated at least four other phases including a pipe-structure Mn7(OH)3(VO4)4 [15], d-MnxV2O5 and g-MnV2O5. This paper discusses the synthesis and characterization of the g-MnV2O5 phase.
2. Experimental MnV2O5 was prepared by the hydrothermal treatment of V2O5 from Alfa, with MnSO4 powder and diethanolamine from Aldrich in a 1:1:2 molar ratio, respectively; the pH of this solution was 6.06. The reaction mixture was heated in a 125 ml Teflon-lined Parr reactor for 72 h at 455 K. The resulting dark green powder was filtered and dried in air. The pH of the solution after reaction was almost neutral, pHs6.13. X-ray powder diffraction was performed using Cu Ka radiation on a Scintag XDS2000 u–u diffractometer equipped with a Ge(Li) solid-state detector. The data were collected with a step of 0.028; 2u from 10 to 708 with an exposure of 30 s per step, and 2u from 70 to 1258 with an exposure of 45 s per step. TGA data were obtained on a Perkin-Elmer model TGA 7, FT-IR data on a Perkin-Elmer 1500 series,
1388-2481/99/$ - see front matter q1999 Elsevier Science S.A. All rights reserved. PII S 1 3 8 8 - 2 4 8 1 ( 9 9 ) 0 0 1 1 3 - 7
Tuesday Oct 26 09:36 AM
StyleTag -- Journal: ELECOM (Electrochemistry Communications)
Article: 123
F. Zhang et al. / Electrochemistry Communications 1 (1999) 564–567
and electron microscopy data on an Electroscan 2020 environmental scanning electron microscope. Initial electrochemical studies were conducted in lithium cells using 1.5 M LiPF6 in a 2:1 dimethyl carbonate/ethylcarbonate mixture as the electrolyte; the vanadium oxide was mixed with 10% carbon black and 10% Teflon powder, and hot pressed for 20 min at 4408F. A MacPile potentiostat was used to cycle the cells.
3. Results and discussion The manganese–vanadium compound was precipitated as well-formed dark brown large lathe-like sheets, as shown in Fig. 1. These sheets were around 1–2 mm thick, 10 mm across and 100 mm on an edge. Electron microprobe analysis showed that they contained manganese and vanadium in approximately a 1:2 ratio, and no sulfur was detected. The TGA analysis of this compound in oxygen is shown in Fig. 2. There is a 6% increase in weight from 380 to 5808C;
565
this gain corresponds to the addition of one oxygen atom. Xray analysis of the product after heating to 6508C in oxygen shows the formation of Mn(VO3)2 suggesting that the initial compound has the formula MnV2O5. The FT-IR spectrum showed a vanadyl group at 984 cmy1, with a sharp vanadium– oxygen band at 865.3 cmy1, and broad bands around 627.5, 570.8 and 395.3 cmy1. The X-ray diffraction pattern of the manganese compound (Fig. 3) was indexed in the orthorhombic system and space ˚ , bs group Pnma with cell parameters as9.7585(2) A ˚ ˚ 3.5825(1) A, cs11.2653(2) A. The crystal structure of MnV2O5 was determined from powder data using CSD crystallographic software [16]. Final Rietveld refinement was carried out using GSAS software [17]. The crystallographic data and atomic parameters are shown in Tables 1 and 2 respectively. This structure contains vanadium oxide sheets, made from VO5 square pyramids (SPs), between which the manganese ions reside. There are two independent vanadium atoms with similar square pyramidal (SP) coordination with doublebonded oxygen at the apex, whereas manganese has octahedral coordination. The interatomic distances are shown in Table 3. The vanadium SPs share edges to form two crystallographically independent chains along the b axis. The SPs alternate along the chain in up and down orientations. Unused corners of SP base are shared between different chains linking Table 1 Crystallographic data for g-MnV2O5
Fig. 1. Morphology of g-MnV2O5.
Chemical formula Space group ˚) a (A ˚) b (A ˚) c (A ˚ 3) Cell volume (A Density (g cmy3) Formula weight (g moly1) Formula units per cell Number of reflections Number of variables RBregg(F2) Rprof wRprof
MnV2O5 Pnma 9.7585(2) 3.58252(6) 11.2653(2) 393.83(1) 3.994 236.82 4 373 64 0.045 0.052 0.073
Table 2 Atomic parameters for g-MnV2O5 Atom
x/a
y/b
z/c
˚2 U(iso)=100/A
V1 V2 Mn O1 O2 O3 O4 O5
0.3737(2) 0.0559(2) 0.6704(1) 0.9638(4) 0.2814(5) 0.9262(5) 0.2453(6) 0.5704(6)
1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4
0.4984(1) 0.5951(1) 0.2801(1) 0.7186(4) 0.3778(4) 0.4587(4) 0.6342(4) 0.4517(4)
0.41(7) 0.32(8) 0.84(8) 0.33(9) 0.33(9) 0.33(9) 0.33(9) 0.33(9)
Fig. 2. TGA of g-MnV2O5 in oxygen at a heating rate of 38C miny1.
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StyleTag -- Journal: ELECOM (Electrochemistry Communications)
Article: 123
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F. Zhang et al. / Electrochemistry Communications 1 (1999) 564–567
Fig. 3. Experimental (dotted), calculated (line) and difference (bottom) plots for g-MnV2O5. Vertical lines depict reflection positions.
Table 3 ˚ ) for g-MnV2O5 Interatomic distances (A V1 O2 O4 O5 O59 O50
V2 1.629(4) 1.978(5) 1.991(5) 1.955(2) 1.955(2)
O1 O3 O39 O30 O4
Mn 1.657(5) 1.990(5) 1.899(2) 1.899(2) 1.900(6)
O1 O19 O2 O4 O49 O5
2.324(3) 2.324(3) 2.083(4) 2.195(4) 2.195(4) 2.165(5)
them into a layer. The layers are stacked along the c axis. The apical oxygen atoms of SPs form octahedral cavities filled with manganese atoms (Fig. 4). It appears that the title compound is isostructural to the g-modification of LiV2O5 [18,19]. These two structures substantially differ only in ˚3 ˚ 3 for g-LiV2O5 and 393.8 A their cell volume, i.e., 373.2 A for MnV2O5. This difference is due to replacement of smaller Li with bigger Mn atoms between layers and therefore only ˚. the c axis increases significantly from 10.66 to 11.27 A The electrochemical behavior of the MnV2O5 phase is shown in Fig. 5. The initial cell voltage was 3.6 V. Initially over one lithium atom could be incorporated into the structure on discharge down to 2 V, after a charge to 4 V. This dropped to a steady value of 0.87 lithium atoms after three cycles, as shown in Fig. 6. The overall low discharge potential is related to the low oxidation states of the manganese and vanadium,
Tuesday Oct 26 09:36 AM
Fig. 4. Polyhedra representation of g-MnV2O5 crystal structure along the b axis. Vanadium square pyramids are shown in red color and manganese octahedra in blue.
nominally q2 and q4, respectively. A successful cathode will need a higher capacity with the manganese and vanadium ions reversed in position and in their highest oxidation states, e.g. VMn2O6.5.
StyleTag -- Journal: ELECOM (Electrochemistry Communications)
Article: 123
F. Zhang et al. / Electrochemistry Communications 1 (1999) 564–567
567
Acknowledgements We thank the Department of Energy, Office of Transportation Technologies, through Lawrence Berkeley Laboratory for partial support of this work. We also thank Bill Blackburn for the electron microprobe studies.
References
Fig. 5. Electrochemical cycling of g-MnV2O5.
Fig. 6. Capacity of g-MnV2O5 on cycling.
4. Conclusions
A new manganese vanadium oxide g-MnV2O5 has been synthesized hydrothermally and its structure, isotypical to g-LiV2O5, was determined and refined by the Rietveld method. It is isostructural with g-LiV2O5, containing sheets of VO5 square pyramids between which manganese ions reside in octahedral sites. It intercalates one lithium atom in a reversible manner above 2 V.
Tuesday Oct 26 09:36 AM
[1] D.W. Murphy, P.A. Christian, F.J. Disalvo, J.N. Carides, J. Electrochem. Soc. 126 (1979) 497. [2] F. Leroux, D. Guyomard, Y. Piffard, Solid State Ionics 80 (1995) 307. [3] R. Chen, P. Zavalij, M.S. Whittingham, Chem. Mater. 8 (1996) 1275. [4] R. Chen, M.S. Whittingham, J. Electrochem. Soc. 144 (1997) L64. [5] C. Delmas, F. Capitaine, Abstr., 8th Int. Meet. Lithium Batteries 8 (1996) 470. [6] A.R. Armstrong, P.G. Bruce, Nature 381 (1996) 499. [7] A.R. Armstrong, R. Gitzendanner, A.D. Robertson, P.G. Bruce, Chem. Commun. (1998) 1833. [8] T.A. Chirayil, P.Y. Zavalij, M.S. Whittingham, Chem. Mater. 10 (1998) 2629. [9] T. Chirayil, P. Zavalij, M.S. Whittingham, J. Electrochem. Soc. 143 (1996) L193. [10] F. Zhang, P.Y. Zavalij, M.S. Whittingham, Mater. Res. Bull. 32 (1997) 701. [11] S.H. Kim, S.J. Kim, S.M. Oh, Chem. Mater. 11 (1999) 557. [12] M.S. Whittingham, R. Chen, T. Chirayil, P. Zavalij, Electrochem. Soc. Proc. 96-5 (1996) 76. [13] M.S. Whittingham, in: O. Yamamoto, M. Wakihara (Eds.), Lithium Batteries, Kodansha, Tokyo, 1998. [14] P.Y. Zavalij, F. Zhang, M.S. Whittingham, Acta Crystallogr., Sect. C 53 (1997) 1738. [15] F. Zhang, P.Y. Zavalij, M.S. Whittingham, J. Mater. Chem. 10 (1999) in press. [16] L.G. Akselrud, P.Y. Zavalii, Y.N. Grin, V.K. Pecharsky, B. Baumgartner, E. Wolfel, Mater. Sci. Forum 133–136 (1993) 335. [17] A.C. Larson, R.B. VonDreele, GSAS. General Structure Analysis System. User Guide, Los Alamos National Laboratory, Los Alamos, NM, USA, 1994. [18] D.N. Anderson, R.D. Willett, Acta Crystallogr., Sect. B 27 (1971) 1477. [19] J. Galy, J. Darriet, P. Hagenmuller, Chim. Miner. 8 (1971) 509.
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Article: 123