(1)Journal of the Korean Chemical Society 2002, Vol
7
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전체 글
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(3) * †. /RRC-HECS ( )
(4) (2002. 9. 26 ) †. Solvent Effect on Anode Performance in Lithium Ion Batteries Kwang-il Chung†, Jung -Hwan Cho, Woo-Jong Sim, and Yong-Kook Choi* Department of Chemistry and RRC-HECS, Chonnam National University, Kwangju 500-757, Korea † Anycell Inc. R&D Center, Kwangju 506-258, Korea (Received September 26, 2002). . , ! " #$% &'()* +,- ./% 0* 1 2345. 6 78 9 : ; <= >? @A BCD EF- C/ GHD HI JK LMN O P* Q 1 2345. <= >? @A BCD EF- , C/ .R- ST HIU J K O P* VW% XY34Z [ \]% ^_345. `aVb, (c db, ef d gb, hEijb % H3k XYD l JmA, ST HI- JK ST HIn. o <= >? @A BC D EF- , C/ pq5. : , STHI, HIn., ABSTRACT. We have studied to find the optimum electrolyte that satisfied high ionic conductivity, large electrochemical window, etc in Li-ion battery. And also studied were the effect of a passive film on carbon anode surface, which is formed by solvent decomposition during the initial charge process. Electrochemical properties of the passive film formed on carbon anode surface investigated and explained as the volumetric ratio of the mixed solvents. The results of scanning electron microscopy, chronopotentiometry, cyclic voltammetry, impedance spectroscopy revealed that the electrochemical properties of the passive film were varied with the ionic conductivity of the electrolyte including the mixed solvents. Keywords: Li-ion Battery, Mixed Solvents, Solvent Decomposition, Ionic Conductivity. - * 4 V rst u d v Q ;w x y 1 rz r u {| 2} ~ Iv Q 5. Q - Q uW N ? C/ Q 6 ./ HR Q ~ 2PL 5. , ./ HR Q * , ! " #$% &'()* +,- ./ 1. 2-7. 8. % 0* r 2PL 5. 6 78 9 : ; <= >? @A BCD EF- C/ GHD H I JK LMN O P* Q 2PL 5. ; <= ? @A HIn.~ ]3k BCD EF- C/% Z3* 2P5. [Q l -3A ./ [ JK ST HI Cn JK EF- ,, , C/ pK 5Z ZPL 5. [ `s .R XD * >n ( 9,10. 11. 12,13. 528. 14,15.
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(6) . 529. Fig. 1. SEM images of the surface of the original MPCF electrode (a, b) and the surface of the MPCF electrode after initial charge (c, d).. j QPL Z, HIn. <
(7) - ^_ HIn. 1 Q (j- PL 5. Li- - ./ HR UHR 1 GH3Z * * HR ./ % GH 3* Vv U. - { d% ¡ * ¢£ Z, HIn.~ BCD EF UHI >n ¤3 ¥¦5. HIn.* - Hw% §()* Ur¨ ©ª&, [ «C- ¬~ <= >? @A BCD EF .* > ~, .* ~ { 3 ¥¦ ®D HIn. ©ª% (¯ 5. [°~ HIn. ©ª L± * ²,5. ³ Q HIn. ©ª% ] ,~ ()´* l 5. HIn. ©ª <= >? ®~ µ¶P* ¡LA, <= >? ·P* `¸% XY ¹ 5. º HIn. ©ª »eQ @A©ª |
(8) K 78 ¼ µ¶(co-intercalation)D ½ n.©ª P ¥¦5. JK HIn. ©ª µ¶P* (¾ 0.3 V 3)5 ¿À 16. 17-20. 2002, Vol. 46, No. 6. 2PLÁ Q5. = * <= >? @A BCD EF- , C/ .R- ST HIU JK LMN O P*r1 XY34Z [ \]% ^_3Z 345. ÂQ ST HIU JK HIn. 1 XY34 z [ \]% .Ã3Z 345. Ä, ST HIU J K O3* .R- , C/ EF- , C/ HIn. LMN ÅW% Z * 1 Z 345. Q 1 3k `aVb, (c db, efd gb, Æb, hEijb GHP5.. (Cell)
(9) . Mesophase pitch-based ? MPCF ÇvÈ6 1 Z 3 Q lT(polyvinyldifluoride, PVDF) [Z C% W¸() Q (KS-15)~ C Pz, 3É- Ê1 nËHI(N-methylpyrrolidone, NMP)1 H3k ¡UÌ~ ST3k Í carbon fiber(MPCF).
(10) . 530. Î34Z [ * 1 cm ~ 345. ÏD ? - @A% `aV~ XY¹ l1 Fig. 1(a), 1(b) ÐÑ5. MPCF* ÒV Ó 8 µmZ Ôr Õ^Ö,] ×45. ØÙ XYD MPCF - @A Iv Ú_3Z ÛÜ345. [ ØÙ ½ XYQ ?@A Fig. 1(c), 1(d)ÝÞ × @A EF BCPL 5. º 9 : HIn. «C <= >? @A ¬~ ]3k XYD º5. ¸? 1.44 cm -foil% GH345. ÂQ polypropylene(PP) /microporous membrane(Celgard #2500)% Separator~ GH3k ß ?c- »à% u345. á (ÙH cell sandwich-type- yâã~ CD 2? (j Z, ¸? ä?- ¨¹% å3Z 5. . ./ HR e r battery grade] ./ HI% Aldrich G ¶3k È ¸- 1 3 æZ ç~ GH345. = ØÙ G HD ./ HR ethylene carbonate(EC; Aldrich, 98%) 6 diethl cabonate(DEC; Grant Chemical, Battery grade) 1 k r >E UÌ(x:y)~ STQ HR% HI~ 3Z, lithium hexafluorophosphate(LiPF6; Aldrich, Battery grade)- ./ % èL 1.0 M LiPF /EC : DEC(x:y) 1 Ò Ï3k GH345. . MPCF ? Q B,] :é u ØÙ WonATechG- WBCS 3000 battery cycler1 Hê5. Galvanostatic cycling :(intercalation) 0.0 V(vs. Li/Li )s, u(deintercalation) 2.0 V(vs. Li/Li )s~ potential range1 Q345. ¥ g Ï$ 0.5 mA/cm 5. ef d g Ø Ù% 3k EG&G PAR M273A potentiostat/galvanostat 1 l3k Æ34z, ÆD l* M270 software program~ Ý345. ¥ scan rate* 1 mV/ sec~ 3.0 V~0.0 V(vs. Li/Li )s Æ345. 1 Æ3 . MODEL 1671 (JENCO electronics. Ltd.)1 GH345. Î KClHR ¡ ë~ ZPL * Pt ?% Æ cell èL ¸ ì% l345. ÆD ¸ ì % H3k ST HIU JK ÏD ./ HR 1 ¸ Æ345. g Impedence Ø Ù EG&G PAR M5210 Lock-in Amplifier1 EG&G PAR M273A potentiostat/galvanostat6 l3k GH 345. Impedence Æ nÃ% Q programing 2. 20,21. 2. * M398% PC6 l3k L345. ¥ - frequency range* 100 kHz~10 mHz 4z, gíî- ï ±5 mV~ 345. ðñ g impedence ØÙ open circuit voltage(OCV) 2345. lithium- òQ Ë ¥¦ UC ] Ar~ Î D glove box Ñ ÆH 1 C 34Z, ðñ ØÙ ±25 C - Ø ¼Ñn- ó% ô* ¸õ öL÷5. software. impedence analyser. o. >EU)1 .R~ 3 k CD cell 0.5 mA/cm - g1 ] r3k :éu ØÙ% 2345. :éu ØÙl ; 9 :éu øÚ- » ;wù- Hw Q d O 1 Fig. 2 (345. XYD :éu H 1.0 M LiPF6/EC : DEC(x:y,. 2. 6. +. +. 2. +. Fig. 2. Initial charge-discharge curves of the MPCF electrode in 1 M LiPF6 / EC : DME(x:y) solutions; ich = idis = 0.5 A/cm2 and x:y is from 1:9 to 7:3. Journal of the Korean Chemical Society.
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(12) . 531. Table 1. Initial charge-discharge capacities and initial discharge voltage as volumetric ratio of the mixed slovents 1.0 M LiPF6 / EC : DEC Initial charge capacity Initial discharge capacity (x:y), volume ratio) (mAh/g) (mAh/g) 1:9 2:8 3:7 4:6 5:5 6:4 7:3. 372 446 519 569 473 337 188. 257 302 385 421 415 300 115. w 9 u ì% Table 1 ÐÑ5. 9 u ì [ú- øÚ û@~ @(3 45. Table 1 JmA ST HIU JK 9 Ur ¨ Hw ~ pq5. ü Ur¨ Hw GHD ? / .R JK pK 5. = ØÙ XY D Ur¨ Hw- ýG,] }* ÏD MPCF ? - Ø þA, ;w- aÿQ } -. Ð l~ »D5. [ EC- 7w L± rQ Vv* Q } L l 1 % *, º .R- ST HIU}~ ]3k HIn.- pK l~ »3 45. ST HIU JK XYD 9 u ìO * EC- 7w r7 JK §35r 5( r345. 9 u ì } JK pK* HR }~ ]3k, Â* HI n . -. BCD EF- }~ ]3k pK/ 5. ü 9 u ì- O3 VW 9 u Hw- O VW ¡
(13) 345. º 9 u r u Hw ÅW% Z % (GQ5. ST HIU J HI n. 1 »3 3k ef d gb% H34Z [ l1 Fig. 3 (345. ¥ GHD d * 3 V > 0 Vs4z, dOfÌ 1 mV/sec45. d OfÌ JK HIn. r ¹ ¥¦, áá- .R% U3 3k ¡Q dOfÌ % GH3k Æ34Z % U345. Z D ç -3A, 1.0 M LiPF /EC : DEC(1:1=5:5) .R DEC f\ n. E* Ó 2 V, EC f\ n. E* Ó 0.5 V XYP5. Fig. 3 XYD H I n. E ST HIU JK Óc- }r 5. DEC- >E 7w % DEC- n. E * - uW~ 34Z, 2 n. 21. 6. 2002, Vol. 46, No. 6. Irreversible capactiy (mAh/g). Initial discharge voltage (V vs. Li/Li+). 115 144 134 148 58 37 73. 0.143 0.140 0.094 0.076 0.086 0.121 0.270. Fig. 3. Cyclic voltammograms of the MPCF electrode in 1 M LiPF6 / EC : DME(x:y) solutions; scan rate is 1 mV/sec and x:y is from 1:9 to 7:3.. ©ª~ P* ß- n. Er Ø XYP 5. ©~ DEC- >E 7w LZ, EC- > E 7w L, DEC n. E* - uW~ 34Z, [ E* ££ rsA 3~ T÷5. [5r EC- 7w È |/.
(14) . 532. Table 2. Ionic conductivitites as the change of the volumetric ratio of the mixed solvents 1.0 M LiPF6 / EC : DEC (x:y), volume ratio). Ionic conductivity (S/cm). 1:9 2:8 3:7 4:6 5:5 6:4 7:3. 3.2×10−3 4.0×10−3 5.2×10−3 5.9×10−3 5.7×10−3 4.0×10−3 4.1×10−3. Vv* 5( DEC n. Er - uW~ 345. a Q ç6 ", HIn. ©ª 78 k3 ¥¦ HI n. Er .R - C Xr % º~ »345. Ä, .R- C Vv HI6 78 ©ª ?~ r ±N PL, HIn.* - uW~ Q ¡L º~ « áP5. JK .R- 1 Æ3k H I n. - O 1 _3Z Q5. ST HIU JK ÆD 1 Table 2 ÐÑ5. XYD l JmA, £ r ¸,~ Z Ì DEC6 £ * & Ì EC- ST U JK ì ~ 5mN Ð 5. XYD VW EC- >E nÌ r7JK r35r, EC- >E Ur 50% ¸ r¹ Vv EC- £C ¥¦ 5( §34 5. JK ÏD ./ HR ST HIU JK ~ 5 C% Z 5. ef d g b XYD HIn. E VW U. A, r ST HIU* HIn. Er - uW~ 3k XYPZ, r ST HIU* - uW~ 3k XYP 5. Ä, HI n. - O ÅW% ä ;#Q ]r [ .R- h% ]¹ 5. Table 1 ÐÑi 9 u ì- O # ]% 0 3k .R- HIn. «C -. <= ? @A BCD EF % Æê5. ST HIU JK : ÊD MPCF?- hE ij1 Æ34Z, [ l1 Fig. 4 ÐÑ5. Æ D hEij l1 Nyquest plot% GH3k .R. EF % Æ3k [ O 1 XY345.. Fig. 4. Impedance spectra of the MPCF electrode in 1 M LiPF6 / EC : DEC(x:y) after the initial charge until 0.0 V; x:y is from 1:9 to 7:3.. ÂQ áá- % 3N Æ3 .* = ( j TùQ , !r!~1 3Z [ ! r!~6 ÆD l1 "#$% (& } r +r P Ï'3Z 345. -. .R <= >?- A% @`3 .. ()( !% H3k ÐùQ !r!~ ( P5. = * (Q !r! ~1 H3k ST HIU JK ÆD .R. EF % Æ34Z [ O 1 Fig. 5 ÐÑ 5. k XYD .R - O * EF. - O 6 U3k ST HIU JK [ *3 æ+5. [ EF - O * EC- 7w r ¹ §35r 5( r3* , O 1 45. Q O - VW -- 9 u ì- O (Table 1)6 . ¡
(15) 7% k 5. [ .R JK O 3* HR [ O r æ+ ¥¦ 9 u ì- O , ÅW % æ+% º~ GÊD5. 5( /. ST H IU JK 9 u ì- O * HI n.~ BCD EF- , C/ JK O 7% ] 345. 22. Journal of the Korean Chemical Society.
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(17) . Fig. 5. Plots of solution resistances and film resistance vs. volume fraction of EC after the initial charge until 0.0 V.. Fig. 4* 9 : ÊD MPCF ?% GH3 4 ¥¦ ÆD hEij* .R EF. 0 <= >? - 3 Q 78 XYP5. ÝÞ STD r 1 k * hEij l* áá- Cn% n3r L 2Z C¼,~ n345 3ÈK í3 L2 5. Q ¦1 .l3A ST HIU JK 3. 533. Fig. 7. Plots of film resistance vs. volume fraction of EC after the initial charge until 0.5 V.. È T,] EF - O 1 XY3 3k : Ê (£- 1 Ï'345. 9 : øÚ(Fig. 2) ef d g øÚ(Fig. 3) ]êi ºÝÞ HI- n. * Ó 2 V6 0.5 V(vs. Li/Li ) X YP5. ü ~ : Ê (£- 1 0.5 V ~ 3k :% ÉÊ(4 ½, hEij1 Æ345. 5N ÆD hEij l* 1 Z 6 * ©ª k3* 0.3 V 3- 5 ÆD l°~, 3 - c7ô Ò EF XQ l1 % 5. l1 Fig. 6 ÐÑ5. ÆD hEij l~> ST HIU JK <= >? @A BCD EF-. O 1 Fig. 7 ÐÑ5. k XYD VWC Fig. 5 k º "+5. JK ST HIU JK O D 9 u ì á HIU n .PL «CD EF- ì JK O PZ, ü ì -. u Hw ÅW% 6+ % ]345. +. . Fig. 6. Impedance spectra of the MPCF electrode in 1 M LiPF6 / EC : DEC(x:y) after the initial charge until 0.5 V; x:y is from 1:9 to 7:3. 2002, Vol. 46, No. 6. = <= >? @A BCD EF- , C/ .R- ST HIU JK LMN O PZ *r1 XY345. `aVb~ ]Q l, 9 : ½ <= ? @A HIn. ©ª«C~ EF BCPL 5. (c db e f d gb~ ]Q l, HI n. * G HD HI- STU JK }r 5. HI n..
(18) . 534. * .R- 6 8 Xr 5. º HIn. ©ª ¡L ¥ [ ©ª k3 ¥¦, - JK HI n. r pK÷5. ÂQ 9 u ì S T HIUJK O 345. [ [Q O *, h Eijb% H3k ]Q l, .R- - ÅWK 5* HIn.~ BCD EF-. ¸XXr 5. JK - - :é u øÚ XYP* HI n. -Q 9: * .R- C JK [ ì pK/ Z, 9 u ì uHw HIn. «C ~ BCD EF- C/ JK pK/ % = 1 ¾3k ]345. = ;¦ 2001< U \ -. öL÷z §G=>
(19) 5.. 1. Extended Abstracts, 8th Int. Meeting on Lithium Batteries, Nagoya, Japan, 1996, June 16-21. 2. Dahn, J. R.; Sleigh, A.K.; Shi, H.; Way, B.M.; Weydanz, W. J.; Reimers, J. N.; Zhong, Q.; Sacken, U. Von. in Lithium Batteries, Elsevier, Amsterdam, 1993. 3. Sawai, K.; Iwakoshi, Y.; Ohzuku, T. J. Solid State Ioincs, 1994, 69, 273. 4. Dahn, J. R.; Sacken, U vom.; Juzkew, M. W.; Al-Janaby, H. J. Eletrochem. Soc. 1991, 138, 2207. 5. Ohzuku, T.; Ueda, A.; Hirai, T. J. Chem.Express 1992, 7, 193. 6. Yamaura, J.; Ozaki, Y.; Morita, A.; Ohta, A. J. Power. Sources 1993, 43, 241. 7. Manev, V.; Naidenov, I.; Puresheva, B.; Pistoia, G.; J. Power Sources 1995, 57, 133. 8. Nishio, K.; Yoshimura, S.; Saito, T. J. Power Sources 1995, 55, 115. 9. Besenhard, J. O.; Winter, M.; Yaug, J.; Biberacher, W. J. Power Sources 1995, 54, 228. 10. Inaba, M.; Siroma, Z.; Kawatate, Y.; Funabiki, A.; Ogumi, Z. J. Power Sources 1997, 68, 221. 11. Ue, M.; Mori, S. J. Electrochem. Soc. 1995, 142, 2577. 12. Chung, K-i.; Chung, M-W.; Kim, W-S.; Kim, S-K.; Sung, Y-E.; Choi, Y-K. Bull. Korean Chem. Soc. 2001, 22, 189. 13. Ratnakumar, B. V.; Smart, M. C. J. Power Sources 2001, 97, 139. 14. Choi, Y-K.; Park, J-G.; Chung, K-i.; Choi B-d.; Kim, W-S. Microchemal J. 2000, 64, 227. 15. Aurbach, Doron.; Ein-Eli, Yair.; Markovsky, Boris.; Zaban Arie.; Schechter, Alexander. J.Eletrochem. Soc. 1994, 94, 28. 16. Deutscher, R. L.; Florence T. M.; Woods, R. J. Power Sources 1995, 55, 41. 17. Ein-Eli, Y.; Thomas S. R.; Koch, V. R. J. Electrochem. Soc. 1999, 144, 1159. 18. Osaka, T.; Momma, T.; Matsumoto Y.; Uchida, Y. J. Electrochem. Soc. 1997, 144, 1709. 19. Winter, M.; Imhof, R.; Joho, F.; Novak, P. J. Power Sources 1999, 81, 818. 20. Choi, Y-K.; Chung, K-i.; Kim, W-S.; Sung, Y-E.; Park, S-M. J. Power Sources 2002, 104, 132. 21. Choi, Y-K.; Chung, K-i.; Kim, W-S.; Sung, Y-E. Microchemical J. 2001, 68, 61. 22. Umeda, M.; Dokko, K.; Fujita, Y.; Mohamedi, M.; Uehida I.; Selman, J.R. J. Electrochem. Acta. 2001, 47, 885.. Journal of the Korean Chemical Society.
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