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Ionic transport and electrochemical cell characteristic studies of a new polymer electrolyte (PEO + glass) system
April 1995
MaterialsLetters23 (1995) 129-132
Ionic transport and electrochemical cell characteristic studies of a new polymer electrolyte (PEO + glass) system M. Jaip,al Reddy, D. Srinivas Reddy, S. Sreepathi Rao, U.V. Subba Rao Department of Physics, Osmania University, Hyderabad 500 007, India
Received 13 September 1995;in final form 25 January 1995;accepted 26 January 1995
Abstract A new polymer electrolyte system, polyethylene oxide (PEO), complexed with a glass ( 15NaF-15Na@-70Bz03) has been investigated. The solvation of glass with PEO was confirmed by IR and optical absorption studies. The transport number measurements showed that the electrolyte was a mixed (ionic + electronic) conductor, the charge transport being mainly ionic (km = 0.93). Using this electrolyte, an electrochemical cell with configuration Nal (PEO + glass) /(I* + C +‘electrolyte) has been fabricated and its discharge characteristics studied (open circuit voltage (OCV) =2.12 V and short circuit current (SCC) = 100 pA). A :number of cell parameters evaluated are reported in this paper.
1. Introduction The solid polymer electrolytes, i.e. polymer salt complexes, are of technological interest due to their
possible application as solid electrolytes in different devices such as energy conversion units (batteries/fuel cells), e1ectrochromi.c display devices/smart windows, photoelectrochemical solar cells, etc. [ l-41. Many sodium-ion conducting polymer electrolytes have been reported based on PIEO, polypropylene oxide (PPO) , poly-bismethoxy ethoxy ethoxy phosphazene (MEEP) complexed with NaI, NaClO,, NaSCN, NaCF,SO, [ 571. Polyethylene oxide, in particular, is an exceptional polymer which dissolves high concentrations of a wide variety of salts to form polymeric electrolytes [S]. Most of the studies in this field are devoted to PEObased electrolytes using alkali salts, e.g. LiBF,, LiPF, and LiB(C,H,), [9], LiSCN [ lo], LiSO&F, and LiClO* [ll] and NaPF, [12], NaSCN [13]. Some Ag+-ion conducting polymer complexes with PEO are reported [ 14-161. The effect of addition of P_A1203 0167-577x/95/$09.50 0 1995Elsevier Science B.V. All rights reserved SSD10167-577x(95)00025-9
has been studied in PEO +LiClO, [ 171 and PEO + NaSCN [ 181 systems. Amita Chandra et al. [ 191 have studied a composite polymer electrolyte (PEO + NH4 + I + A1203) for improved film stability. In the present paper, the authors report a new polymer thin film electrolyte (PEO + glass ( lSNaF15Na,O-70B,O,) system. Several experimental techniques such as IR, optical absorption and transference number measurements have been employed to characterize this new polymer electrolyte system and the results thus obtained are reported. An electrochemical cell with configuration Na/ (PEO + glass) / (I*+C +electrolyte) has been fabricated and its discharge characteristics studied. The results of these investigations are reported in the present paper.
2. Experimental
Films of PEO (Aldrich MW = 6 X 10’) complexed with a fine powder of glass ( 15NaF-15Na@-70Bz03)
130
.I. Jaipal Reddy et al. /Materials
were prepared in the stoichiometric ratio (80 : 20) by a solution-cast technique using methanol (water free) as solvent. The solution was stirred and cast onto the polypropylene dishes and evaporated slowly at room temperature. The final product was vacuum dried thoroughly at 10e3 Torr. The infrared (IR) spectra of all the films have been obtained with the help of a Perkin-Elmer FTIR spectrophotometer (Model 1605) in the range 450-4500 cm-‘. For optical absorption studies in the UV/VIS region, a Shimadzu spectrophotometer (Model UV 3 100) was used. The “total ionic transport number”, t.3 was measured using Wagner’s polarization technique [ 201. In this technique, the freshly prepared film of PEO + glass was polarized in the configuration of Agl (PEO + glass) /Ag under dc bias (step potential of 1.5 V) . The resulting current was monitored as a function of time. An electrochemical cell using PEO + glass electrolyte was fabricated in the configuration Na/ (PEO+glass)/(I,+C+electrolyte). The details about the fabrication of the electrochemical cell are given elsewhere [ 161. The discharge characteristics of the cell were monitored for a constant load of 100 kfl.
3. Results and discussion The complexation of PEO with glass has been confirmed using infrared (IR) and optical absorption studies. The IR spectra of PEO (pure), PEO + glass and glass are shown in Fig. 1. The following changes have been observed in the IR spectra by comparison of complexed PEO with that of the pure PEO and glass: (1) The peaks observed in PEO at 470.6, 1628.9, 1807.4, 2167.1, 2237.6 and 2355.1 cm-’ were found to be disappearing in the PEO + glass complexed film. Similarly, the peaks found at 461.2, 709.5, 825.5, 879.0, 943.8, 1002.9, 1133.7, 2437.4, 2613.7 and 3362.9 cm- ’ in the glass also disappeared in the complexed PEO. (2) New peaks around 528.2 and 1595.8 cm-’ were observed in the PEO + glass complex. (3) The peaks observed in PEO at 951.7, 1237.7, 1960.1 and 4000.4 cm- ’ were found to be shifted to 956.1, 1241.5, 1966.7 and 4012.2 cm-‘, respectively, in the complexed PEO. Similarly, the peaks observed
ktters
23 (1995) 129-132
WAVENUMBER
(Cm-‘,
Fig.1.Infmedspectraof(a)PEO(pure);(b)PEO+glassand(c) glass.
in the glass at 1277.3, 1347.6 and 1478.6 cm-’ were shifted to 1282.0, 1346.4 and 1468.3 cm-‘, respectively, in the complexed PEO. The appearance of new peaks other than those of the constituent materials PEO and glass and changes (disappearance and shifting) in the existing peaks in the IR spectra directly suggest the complexation of the glass with polymer. For further confirmation, the UV/visible spectra of the PEO (pure), glass and PEO + glass films have been recorded in the wavelength range 190-800 nm and are shown in Fig. 2. The results of IR and optical absorption studies clearly indicate the complexation of the glass with PEO. The transference numbers corresponding to ionic (ri,) and electronic (r& of the PEO +glass system have been evaluated using Wagner’s polarization technique [ 201. In this technique, the dc current was monitored as a function of time on application of fixed dc voltage across the Ag/ (PEO + glass) /Ag cell. After polarization of the cell with 1.5 V dc, the current versus time graph was obtained which is shown in Fig. 3. The calculated transference numbers ( ti, and r,,,) are given in Table 1. The value of the ionic transference number, riO,,has been found to be eO.93. This indicates that the charge transport in the PEO+glass complex is
131
J. Jaipal Reddy et al. /Materials L&ten 23 (1995) 129-132
Table 1 Transference number data, open circuit voltage (OCV) and short circuit current (SCC) for the PEO + glass cell Film
PEO +
Transference number
glass
40”
be
0.93
0.07
tia(Anode)
A
OCV (V)
SCC (W
2.12
100
Connecting wire
-tCathodej (a)
Fig. 2. Optical absorption spectra of (a) PEO (pure); PEO + glass and (c) glass.
(b)
mainly ionic. It is thus obvious that the material is a mixed (electronic + i’onic) conductor, the major contribution being from the ionic part. The diagram of the electrochemical cell and the circuit diagram used for the characterization of the cell are shown in Fig. 4. The discharge characteristics of
Be TIME (min)
Compwition
lb0
1 120
Fig. 4. (a) Diagram of the electrochemical cell. (b) Circuit used for the study of cell characteristics.
the Na/ (PEO + glass) / ( I2 + C + electrolyte) cell at ambient temperature for a constant load of 100 kfi are shown in Figs. 5a and 5b. The open circuit voltage (OCV) and short circuit current (SCC) of the cell have been determined to be 2.12 V and 100 p,A respectively (shown in Table 1) . The cell parameters evaluated are as follows: cell weight 0.521 g; area of the cell 1.34 cm’; current density 74.6 p,A/cm*; discharge time for the plateau region 51 h; discharge capacity 1.96 p,A/ h; power density 0.407 W/kg and energy density 20.757 W h/kg.
(PEO ~GLASS(I~N~F-~SN~,O-~~G~~~)SY~~~ (80:20)
(b)
140
4. Conclusions
-B
Fig. 3. Polarization current versus time graph for the complexed PBO + glass film.
IR and optical absorption spectra clearly indicate the complexation of the glass with PEO. The polymer elec-
J. Jaipal Reddy et al. /Materials Letters 23 (1995) 129-132
(PEO t GLASS)
Head, Department of Chemistry, Osmania University for his help in recording IR spectra. SSR and UVS are grateful to UGC, New Delhi, for awarding them a research project on polymer electrolytes and batteries.
S.&em
(8O:20)Composition Load ‘100 un
References [ 11 J.R. Mac&Bum and C.A. Vincent, eds., Polymer electrolyte
\ 8
16 TIME
24 (hfs)
32
+o
48
56
--.
Fig. 5. (a), (b) Discharge characteristics of an electrochemical cell for a constant load of 100 kn.
trolyte (PEO + glass) is found to be a mixed (ionic + electronic) conductor, the charge transport in the PEO +glass system being mainly ionic and (Gon = 0.93). The open circuit voltage (OCV) short circuit current (XC) obtained for an electrochemical cell with configuration Na/ (PEO + glass) / (I*+C +electrolyte) are found to be 2.12 V and 100 PA, respectively.
Acknowledgement
The authors thank Professor S.V. Suryanarayana, Head, Department of Physics, Osmania University, Hyderabad, Professor V. Haribabu, Professor M.N. Chary and Dr. K.N. Reddy for their encouragement and Professor Suresh Chandra, BHU, Varanasi, for his help and valuable guidance. The authors also thank the
reviews (Elsevier, Amsterdam, 1987). [2] M.B. Armand, Ann. Rev. Mater. Sci. 16 (1986) 245. [ 31 M.A. Ratner and D.F. Shriver, Chem. Rev. 88 (1988) 109. [4] J.R. Owen, in: Superionic solids and solid electrolytes-recent trends, eds. A.L. Laskar and S. Chandra (Academic Press, New York, 1989) p. 111. [5] D. Fauteux, M.D. Lupien and C.D. Robitaille, J. Electrochem. Sot. 134 (1987) 2761. [6] S.G. Greenbaum, Y.S. Pak, M.C. Wintersgill, J.J. Fontanella and J.W. Schultz, J. Electrochem. Sot. 135 (1988) 235. [ 71 S.G. Greenbaum, K.J. Ademic, Y .S. Pak, M.C. Wintersgill and J.J. Fontanella, Solid State Ionics 28-30 (1988) 1042. [8] M.B. Armand, in: Polymer electrolyte reviews, eds. J.R. MacCallum and C.A. Vincent (Elsevier, Amsterdam, 1987) p. 1. [ 91 E.A. Reitman, M.L. Kaplan and R.J. Cava, Solid State Ionics 17 (1985) 67. [lo] P.R. Sorenson and T. Jacobson, Electrochim. Acta 27 (1982) 1675. [ 111 D. Fauteux andC. Robitaille, J. Electrochem. Sot. 133 (1986) 307. [ 121 S.A. Hashmi, Amita Chandra and S. Chandra, in: Solid state ionics: materials and applications, eds. B.V.R. Chowdati et al. (World Scientific, Singapore, 1992) p. 567. [ 131 Y.L. Lee and B. Crist, J. Appl. Phys. 60 ( 1986) 2683. [ 141 T.M.A. Abrantes, L.J. Alcacer andC.A.C. Sequeira, SolidState lonics 18/19 (1986) 315. [ 151 S. Chandra, S.A. Hashmi, M. Saleem and R.C. Agrawal, Solid State Ionics 66 ( 1993). [ 161 S. Sreepathi Rao, K.V. Satyanarayana Rao, Md. Shareefuddin and U.V. Subba Rao, Solid State Ionics 67 (1994) 331. [ 171 J.E. Weston and B.C.H. Steele, Solid State Ionics 7 ( 1982) 75. [ 181 He Yuankang, Chen Zhusheng and Zhang Zhiyi, in: Materials for solid state ionics, eds. B.V.R. Chowdari and S. Radhakrishna (World Scientific, Singapore, 1986) p. 333. [ 191 Amita Chandra, P.C. Srivastava and S. Chandra, in: Solid state ionics: materials and applications, eds. B.V.R. Chowdary et al. (World Scientific, Singapore, 1992) p. 397. [20] J.B. Wagner and C. Wagner, J. Chem. Phys. 26 (1957) 1597.
MaterialsLetters23 (1995) 129-132
Ionic transport and electrochemical cell characteristic studies of a new polymer electrolyte (PEO + glass) system M. Jaip,al Reddy, D. Srinivas Reddy, S. Sreepathi Rao, U.V. Subba Rao Department of Physics, Osmania University, Hyderabad 500 007, India
Received 13 September 1995;in final form 25 January 1995;accepted 26 January 1995
Abstract A new polymer electrolyte system, polyethylene oxide (PEO), complexed with a glass ( 15NaF-15Na@-70Bz03) has been investigated. The solvation of glass with PEO was confirmed by IR and optical absorption studies. The transport number measurements showed that the electrolyte was a mixed (ionic + electronic) conductor, the charge transport being mainly ionic (km = 0.93). Using this electrolyte, an electrochemical cell with configuration Nal (PEO + glass) /(I* + C +‘electrolyte) has been fabricated and its discharge characteristics studied (open circuit voltage (OCV) =2.12 V and short circuit current (SCC) = 100 pA). A :number of cell parameters evaluated are reported in this paper.
1. Introduction The solid polymer electrolytes, i.e. polymer salt complexes, are of technological interest due to their
possible application as solid electrolytes in different devices such as energy conversion units (batteries/fuel cells), e1ectrochromi.c display devices/smart windows, photoelectrochemical solar cells, etc. [ l-41. Many sodium-ion conducting polymer electrolytes have been reported based on PIEO, polypropylene oxide (PPO) , poly-bismethoxy ethoxy ethoxy phosphazene (MEEP) complexed with NaI, NaClO,, NaSCN, NaCF,SO, [ 571. Polyethylene oxide, in particular, is an exceptional polymer which dissolves high concentrations of a wide variety of salts to form polymeric electrolytes [S]. Most of the studies in this field are devoted to PEObased electrolytes using alkali salts, e.g. LiBF,, LiPF, and LiB(C,H,), [9], LiSCN [ lo], LiSO&F, and LiClO* [ll] and NaPF, [12], NaSCN [13]. Some Ag+-ion conducting polymer complexes with PEO are reported [ 14-161. The effect of addition of P_A1203 0167-577x/95/$09.50 0 1995Elsevier Science B.V. All rights reserved SSD10167-577x(95)00025-9
has been studied in PEO +LiClO, [ 171 and PEO + NaSCN [ 181 systems. Amita Chandra et al. [ 191 have studied a composite polymer electrolyte (PEO + NH4 + I + A1203) for improved film stability. In the present paper, the authors report a new polymer thin film electrolyte (PEO + glass ( lSNaF15Na,O-70B,O,) system. Several experimental techniques such as IR, optical absorption and transference number measurements have been employed to characterize this new polymer electrolyte system and the results thus obtained are reported. An electrochemical cell with configuration Na/ (PEO + glass) / (I*+C +electrolyte) has been fabricated and its discharge characteristics studied. The results of these investigations are reported in the present paper.
2. Experimental
Films of PEO (Aldrich MW = 6 X 10’) complexed with a fine powder of glass ( 15NaF-15Na@-70Bz03)
130
.I. Jaipal Reddy et al. /Materials
were prepared in the stoichiometric ratio (80 : 20) by a solution-cast technique using methanol (water free) as solvent. The solution was stirred and cast onto the polypropylene dishes and evaporated slowly at room temperature. The final product was vacuum dried thoroughly at 10e3 Torr. The infrared (IR) spectra of all the films have been obtained with the help of a Perkin-Elmer FTIR spectrophotometer (Model 1605) in the range 450-4500 cm-‘. For optical absorption studies in the UV/VIS region, a Shimadzu spectrophotometer (Model UV 3 100) was used. The “total ionic transport number”, t.3 was measured using Wagner’s polarization technique [ 201. In this technique, the freshly prepared film of PEO + glass was polarized in the configuration of Agl (PEO + glass) /Ag under dc bias (step potential of 1.5 V) . The resulting current was monitored as a function of time. An electrochemical cell using PEO + glass electrolyte was fabricated in the configuration Na/ (PEO+glass)/(I,+C+electrolyte). The details about the fabrication of the electrochemical cell are given elsewhere [ 161. The discharge characteristics of the cell were monitored for a constant load of 100 kfl.
3. Results and discussion The complexation of PEO with glass has been confirmed using infrared (IR) and optical absorption studies. The IR spectra of PEO (pure), PEO + glass and glass are shown in Fig. 1. The following changes have been observed in the IR spectra by comparison of complexed PEO with that of the pure PEO and glass: (1) The peaks observed in PEO at 470.6, 1628.9, 1807.4, 2167.1, 2237.6 and 2355.1 cm-’ were found to be disappearing in the PEO + glass complexed film. Similarly, the peaks found at 461.2, 709.5, 825.5, 879.0, 943.8, 1002.9, 1133.7, 2437.4, 2613.7 and 3362.9 cm- ’ in the glass also disappeared in the complexed PEO. (2) New peaks around 528.2 and 1595.8 cm-’ were observed in the PEO + glass complex. (3) The peaks observed in PEO at 951.7, 1237.7, 1960.1 and 4000.4 cm- ’ were found to be shifted to 956.1, 1241.5, 1966.7 and 4012.2 cm-‘, respectively, in the complexed PEO. Similarly, the peaks observed
ktters
23 (1995) 129-132
WAVENUMBER
(Cm-‘,
Fig.1.Infmedspectraof(a)PEO(pure);(b)PEO+glassand(c) glass.
in the glass at 1277.3, 1347.6 and 1478.6 cm-’ were shifted to 1282.0, 1346.4 and 1468.3 cm-‘, respectively, in the complexed PEO. The appearance of new peaks other than those of the constituent materials PEO and glass and changes (disappearance and shifting) in the existing peaks in the IR spectra directly suggest the complexation of the glass with polymer. For further confirmation, the UV/visible spectra of the PEO (pure), glass and PEO + glass films have been recorded in the wavelength range 190-800 nm and are shown in Fig. 2. The results of IR and optical absorption studies clearly indicate the complexation of the glass with PEO. The transference numbers corresponding to ionic (ri,) and electronic (r& of the PEO +glass system have been evaluated using Wagner’s polarization technique [ 201. In this technique, the dc current was monitored as a function of time on application of fixed dc voltage across the Ag/ (PEO + glass) /Ag cell. After polarization of the cell with 1.5 V dc, the current versus time graph was obtained which is shown in Fig. 3. The calculated transference numbers ( ti, and r,,,) are given in Table 1. The value of the ionic transference number, riO,,has been found to be eO.93. This indicates that the charge transport in the PEO+glass complex is
131
J. Jaipal Reddy et al. /Materials L&ten 23 (1995) 129-132
Table 1 Transference number data, open circuit voltage (OCV) and short circuit current (SCC) for the PEO + glass cell Film
PEO +
Transference number
glass
40”
be
0.93
0.07
tia(Anode)
A
OCV (V)
SCC (W
2.12
100
Connecting wire
-tCathodej (a)
Fig. 2. Optical absorption spectra of (a) PEO (pure); PEO + glass and (c) glass.
(b)
mainly ionic. It is thus obvious that the material is a mixed (electronic + i’onic) conductor, the major contribution being from the ionic part. The diagram of the electrochemical cell and the circuit diagram used for the characterization of the cell are shown in Fig. 4. The discharge characteristics of
Be TIME (min)
Compwition
lb0
1 120
Fig. 4. (a) Diagram of the electrochemical cell. (b) Circuit used for the study of cell characteristics.
the Na/ (PEO + glass) / ( I2 + C + electrolyte) cell at ambient temperature for a constant load of 100 kfi are shown in Figs. 5a and 5b. The open circuit voltage (OCV) and short circuit current (SCC) of the cell have been determined to be 2.12 V and 100 p,A respectively (shown in Table 1) . The cell parameters evaluated are as follows: cell weight 0.521 g; area of the cell 1.34 cm’; current density 74.6 p,A/cm*; discharge time for the plateau region 51 h; discharge capacity 1.96 p,A/ h; power density 0.407 W/kg and energy density 20.757 W h/kg.
(PEO ~GLASS(I~N~F-~SN~,O-~~G~~~)SY~~~ (80:20)
(b)
140
4. Conclusions
-B
Fig. 3. Polarization current versus time graph for the complexed PBO + glass film.
IR and optical absorption spectra clearly indicate the complexation of the glass with PEO. The polymer elec-
J. Jaipal Reddy et al. /Materials Letters 23 (1995) 129-132
(PEO t GLASS)
Head, Department of Chemistry, Osmania University for his help in recording IR spectra. SSR and UVS are grateful to UGC, New Delhi, for awarding them a research project on polymer electrolytes and batteries.
S.&em
(8O:20)Composition Load ‘100 un
References [ 11 J.R. Mac&Bum and C.A. Vincent, eds., Polymer electrolyte
\ 8
16 TIME
24 (hfs)
32
+o
48
56
--.
Fig. 5. (a), (b) Discharge characteristics of an electrochemical cell for a constant load of 100 kn.
trolyte (PEO + glass) is found to be a mixed (ionic + electronic) conductor, the charge transport in the PEO +glass system being mainly ionic and (Gon = 0.93). The open circuit voltage (OCV) short circuit current (XC) obtained for an electrochemical cell with configuration Na/ (PEO + glass) / (I*+C +electrolyte) are found to be 2.12 V and 100 PA, respectively.
Acknowledgement
The authors thank Professor S.V. Suryanarayana, Head, Department of Physics, Osmania University, Hyderabad, Professor V. Haribabu, Professor M.N. Chary and Dr. K.N. Reddy for their encouragement and Professor Suresh Chandra, BHU, Varanasi, for his help and valuable guidance. The authors also thank the
reviews (Elsevier, Amsterdam, 1987). [2] M.B. Armand, Ann. Rev. Mater. Sci. 16 (1986) 245. [ 31 M.A. Ratner and D.F. Shriver, Chem. Rev. 88 (1988) 109. [4] J.R. Owen, in: Superionic solids and solid electrolytes-recent trends, eds. A.L. Laskar and S. Chandra (Academic Press, New York, 1989) p. 111. [5] D. Fauteux, M.D. Lupien and C.D. Robitaille, J. Electrochem. Sot. 134 (1987) 2761. [6] S.G. Greenbaum, Y.S. Pak, M.C. Wintersgill, J.J. Fontanella and J.W. Schultz, J. Electrochem. Sot. 135 (1988) 235. [ 71 S.G. Greenbaum, K.J. Ademic, Y .S. Pak, M.C. Wintersgill and J.J. Fontanella, Solid State Ionics 28-30 (1988) 1042. [8] M.B. Armand, in: Polymer electrolyte reviews, eds. J.R. MacCallum and C.A. Vincent (Elsevier, Amsterdam, 1987) p. 1. [ 91 E.A. Reitman, M.L. Kaplan and R.J. Cava, Solid State Ionics 17 (1985) 67. [lo] P.R. Sorenson and T. Jacobson, Electrochim. Acta 27 (1982) 1675. [ 111 D. Fauteux andC. Robitaille, J. Electrochem. Sot. 133 (1986) 307. [ 121 S.A. Hashmi, Amita Chandra and S. Chandra, in: Solid state ionics: materials and applications, eds. B.V.R. Chowdati et al. (World Scientific, Singapore, 1992) p. 567. [ 131 Y.L. Lee and B. Crist, J. Appl. Phys. 60 ( 1986) 2683. [ 141 T.M.A. Abrantes, L.J. Alcacer andC.A.C. Sequeira, SolidState lonics 18/19 (1986) 315. [ 151 S. Chandra, S.A. Hashmi, M. Saleem and R.C. Agrawal, Solid State Ionics 66 ( 1993). [ 161 S. Sreepathi Rao, K.V. Satyanarayana Rao, Md. Shareefuddin and U.V. Subba Rao, Solid State Ionics 67 (1994) 331. [ 171 J.E. Weston and B.C.H. Steele, Solid State Ionics 7 ( 1982) 75. [ 181 He Yuankang, Chen Zhusheng and Zhang Zhiyi, in: Materials for solid state ionics, eds. B.V.R. Chowdari and S. Radhakrishna (World Scientific, Singapore, 1986) p. 333. [ 191 Amita Chandra, P.C. Srivastava and S. Chandra, in: Solid state ionics: materials and applications, eds. B.V.R. Chowdary et al. (World Scientific, Singapore, 1992) p. 397. [20] J.B. Wagner and C. Wagner, J. Chem. Phys. 26 (1957) 1597.