Effect of Activated Carbon on Re-Conversion Reaction of Cu/LiCl/C Electrode with LiPF6/Methyl Difluoroacetate Electrolyte
Katsuo Hashizaki *
Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-Koen, Kasuga, Fukuoka 816-8580, Japan and Office of Society-Academia Collaboration for Innovation, Kyoto University, Uji-shi, Kyoto 611-0011, Japan.
Shinsaku Dobashi
Office of Society-Academia Collaboration for Innovation, Kyoto University, Uji-shi, Kyoto 611-0011, Japan and Research and Innovation Center, Mitsubishi Heavy Industries, Ltd., Nagasaki-shi, Nagasaki 851-0392, Japan.
Shigeto Okada
Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-Koen, Kasuga, Fukuoka 816-8580, Japan.
Toshiro Hirai
Office of Society-Academia Collaboration for Innovation, Kyoto University, Uji-shi, Kyoto 611-0011, Japan.
Jun-ichi Yamaki
Office of Society-Academia Collaboration for Innovation, Kyoto University, Uji-shi, Kyoto 611-0011, Japan.
Zempachi Ogumi
Office of Society-Academia Collaboration for Innovation, Kyoto University, Uji-shi, Kyoto 611-0011, Japan.
*Author to whom correspondence should be addressed.
Abstract
Transition-metal chlorides are known to suffer from dissolution in organic solvents. However, our previous investigation revealed that in the Li/CuCl2 battery, the dissolution of CuCl2 cathode materials could be suppressed by using LiPF6/methyl difluoroacetate (MFA; CHF2COOCH3) electrolyte. And, the Cu/LiCl electrode could both charge and discharge in LiPF6/methyl difluoroacetate (MFA) electrolyte as the re-conversion reaction cathode of Li/CuCl2 battery. However, the capacity is only half the theoretical value of 399 mAh g–1. This is because cuprous is hardly oxidized to cupric during charging due to copper disproportionation reaction.
In this study, activated carbon was added to the Cu/LiCl electrode in order to promote the production of CuCl2, and to improve the capacity. The physical properties of the activated carbon were found to have significant effects: activated carbon with a large specific surface area and micropore volume enabled CuCl2 deposition, and improved the capacity of the Cu/LiCl/C electrode to approximately 300 mAh g–1.
Keywords: Lithium ion battery, Li/CuCl2 battery, MFA, activated carbon, conversion, re-conversion.