Insight into the state of the ZrO2 coating on a LiCoO2 thin-film electrode using the ferrocene redox reaction
- 382 Downloads
Metal oxide coating on positive active materials in lithium-ion batteries is an effective way to improve its cycleability. However, coating state of the metal oxide layer and the mechanism of the improvement have not been fully understood. In this paper, the coated state of ZrO2 on a LiCoO2 thin-film electrode was investigated using a ferrocene redox reaction, and the role of the ZrO2-coating on the degradation phenomena of the LiCoO2 was investigated. The redox behavior of ferrocene revealed that the ZrO2 layer did not cover the entire surface area of LiCoO2, that is, the ZrO2 layer was not compact and contained cracks. In addition, a lithium-ion deficit phase (Li1−x CoO2) was irreversibly formed on the uncovered LiCoO2 areas. In spite of the imperfect ZrO2 layer, the formation of the lithium-ion deficit phase inside the bulk was suppressed. It is clarified that a partial ZrO2 coating on the LiCoO2 is sufficient to suppress the growth of the lithium-ion deficit phase inside the bulk of LiCoO2.
KeywordsLiCoO2 thin-film electrode ZrO2 coating Ferrocene redox reaction Degradation mechanism Surface electron conductivity
This work was partially supported by CREST, JST (JPMJCR12C1). Funidng was provided by Core Research for Evolutional Science and Technology.
- 3.Aurbach D, Markovsky B, Rodkin A, Levi E, Cohen YS, Kim H-J, Schmidt M (2002) On the capacity fading of LiCoO2 intercalation electrodes: the effect of cycling, storage, temperature, and surface film forming additives. Electrochim Acta 47:4291–4306. doi: 10.1016/S0013-4686(02)00417-6 CrossRefGoogle Scholar
- 8.Hirayama M, Sonoyama N, Abe T, Minoura M, Ito M, Mori D, Yamada A, Kanno R, Terashima T, Takano M, Tamura K, Mizuki J (2007) Characterization of electrode/electrolyte interface for lithium batteries using in situ synchrotron X-ray reflectometry: a new experimental technique for LiCoO2 model electrode. J Power Sources 168:493–500. doi: 10.1016/j.jpowsour.2007.03.034 CrossRefGoogle Scholar
- 9.Takamatsu D, Koyama Y, Orikasa Y, Mori S, Nakatsutsumi T, Hirano T, Tanida H, Arai H, Uchimoto Y, Ogumi Z (2012) First in situ observation of the LiCoO2 electrode/electrolyte interface by total-reflection X-ray absorption spectroscopy. Angew Chem Int Ed 51:1–6. doi: 10.1002/anie.201203910 CrossRefGoogle Scholar
- 18.Miyashiro H, Yamanaka A, Tabuchi M, Seki S, Nakayama M, Ohno Y, Kobayashi Y, Mita Y, Usami A, Wakihara M (2006) Improvement of degradation at elevated temperature and at high state-of-charge storage by ZrO2 coating on LiCoO2. J Electrochem Soc 153:A348–A353. doi: 10.1149/1.2149306 CrossRefGoogle Scholar