Reduction of Gas Desorption in Graphite Anode Used in Lithium Ion Battery by Hydrogen Plasma Irradiation

Abstract

In order to reduce amount of electrolyte solvent desorbed from anode material in lithium ion battery, hydrogen plasma irradiation for the anode material was conducted. During the irradiation, the sample was negatively biased. Natural graphite sample after the hydrogen plasma irradiation was soaked in propylene carbonate (PC) used as electrolyte solvent. Then, the gas desorption behavior was investigated by using a technique of thermal desorption spectroscopy (TDS). The amount of gasses in the sample irradiated by hydrogen plasma due to the PC was reduced compared with case in the non-irradiated sample. The reduction by the irradiation became large with the increase of negative bias voltage. The reduction also increased with the ‰uence and became roughly constant in the higher ‰uence regime. In order to discuss this mechanism, the sample without the soaking in PC was heated up to 1173 K. H 2 desorption at high temperature region, around 1173 K, increased for the irradiated sample, compared with non-irradiated sample. This result suggests that implanted hydrogen ions form C H bond with carbon of active sites and then the C H bond might prevent the PC from adsorbing during the subsequent soaking.