CaNis 및 MG-CaNis 전극의 퇴화거동에 미치는 불화처리의 영향

이창래; 오세진; 강성군; C. R. LEE; S. J. Oh; S. G. KANG

Korean Journal of Materials Research, Vol.9, No.6, 622-629, June, 1999

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CaNis 및 MG-CaNis 전극의 퇴화거동에 미치는 불화처리의 영향

The Effect of F-treatment on the Degradation Behavior of the CaNi5 and MG-CaNi5 Electrodes

이창래^†, 오세진, 강성군

한양대학교 공과대학 재료공학과

C. R. LEE^†, S. J. Oh, and S. G. KANG

Dept. Materials Eπgineering, Hanyang University, Seoul 133-791, Korea

E-mail:

초록

CaNi5 빛 기계척 분쇄된 MG-CaNi5 수소저장합금의 전기화학적 충 · 방전 특성에 미치는 K2TiF6 용액에서의 불화처리 빛 in-situ KF+ KOH 전해질에서 불화처리의 영향이 조사되었다. CaNi5 빛 MG-CaNi5 전극은 K2TiF6 용액에서 불화처리에 상관없이 나쁜 충 · 방전특성을 보였다. 이는 불화처리에 의해 형성된 불화물이 충 · 방전 과정에서 KOH 용액에서 분해되어 활성화 촉진이나 내식성 향상에 기여하지 못하기 때문이었다. 전극표변에 지속적이고 안정한 불화충을 형성하기 위하여 잉여의 불소이온을 공급한 2N KF + 6N KOH 전해질에서 CaNi5 합금의 경우 높은 방전용량을 유지하고 있어 내구성이 크게 향상되었음을 알 수 있었다. 그러나, MG-CaNi5의 경우에 있어서는 MG 시간이 증가할수록 방전용량의 감소와 퇴화속도의 증가 경향을 보였다.

Effects of the fluorination in the K2TiF6 solution and in-situ KF + KOH electrolyte on the electrochemical charge-discharge properties of CaNi5 and the Mg-CaNi5 electrodes were investigated. In-situ fluorination in the KF+ KOH electrolyte compared with pre-fluorination in the K 2TiF6 solution could improve the electrochemical cycling durability of CaNi5 and MG-CaNi5 electrodes. The fluorinated layer on the alloy surface by pre-fluorination to improve the activity and anti-corrosion of the electrodes was dissolved in the pure KOH electrolyte during the cycling. The fluorinated layer was formed continuously on the surface of the electrode by thee2N KF addition in the 6N KOH electrolyte. The excess F- ion addition in KOH electrolyte could improve the electrochemical cycling durability of CaNi5 and Mg-CaNi5 electrode. But, in case of MG-CaNi5 electrode, the discharge capacity of the electrode was reduced and the poor cycling property was shown with increasing of the MG process times.

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[1] Kabutomori T, “ Hydrogen Storage Alloys : Fundamentals and Frontier Technologies" , Tamura H, p. 132, New Technology New Science, Tokyo, (1998).

[2] Kumar MPS, Viswanathan B, Swany CS, Srinivasan V, J. Mater. Sci., 21(7), 2335 (1986)

[3] Li ZP, Suda S, The Electrochemical Society Proceedings, PV. 94-27, 78 (1994).

[4] Ishikawa H, Oguro K, Kato A, Suzuki H, Ishii E, J. Less-Common Metals, 120(1), 123 (1986)

[5] Sakai T, Ishikawa H, Oguro K, Iwakura C, Yoneyama H, J. Electrochem. Soc., 134(3), 558 (1987)

[6] Liu FJ, Suda S, J. Alloy. Compd., 190(1), 57 (1992)

[7] Wang XL, Suda S, J. Alloy. Compd., 227(1), 58 (1995)

[8] Sakashita M, Li ZP, Suda S, J. Alloy. Compd., 253-254, 500 (1997)

[9] Park HY, Lee BH, Cho WI, Cho BW, Lee SR, Ju JB, Yun KS, J. Korea Inst. Surf. Eng., 30(4), 262 (1997)

[10] Chang I, Lee BH, Cho WI, Jang H, Cho BW, Yun KS, J. Korean Electrochem. Soc., 1(1), 45 (1998)

[11] Kanda M, J. Met. Finish. Soc. Jpn., 48(12), 1169 (1997)

[12] Lee CR, Kang SG, J. Korean Electrochem. Soc., 2(2), 106 (1999)

[13] Liu FJ, Suda S, J. Alloy. Compd., 231(1-2), 742 (1995)

[14] Yongning L, Xianji Z, J. Alloy. Compd., 267, 231 (1998)

[15] Kumar MPS, Viswanathan B, Swamy CS, J. Mater. Sci., 24(12), 4387 (1989)

[16] NSRDS, “ JANAF Themochemical Tables" , 3rd ed., Am. Inst. Phys. Inc., New York (1986).

[17] Barin I, “ Thermochemical Data of Pure Suætances", VCH, New York (1989).

[18] Smithells CJ, Brandes EA, Brook GB, “ Smithells Metals Reference Book" , ButterworthHeinemann, London, 7th edn., (1992).

[19] Lide DR, Lide J, “CRC Handbook of Chemistry and Physics" , CRC Press, 79th edn., (June 1998).

[20] Li ZP, Suda S, J. Alloy. Compd., 231(1-2), 751 (1995)

[21] Sandrock GD, Murray JJ, Post ML, Taylor JB, Mater. Res. Bull., 17(7), 887 (1982)