start-ver=1.4 cd-journal=joma no-vol=79 cd-vols= no-issue= article-no= start-page=380 end-page=387 dt-received= dt-revised= dt-accepted= dt-pub-year=2014 dt-pub=201411 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=In situ7Li nuclear magnetic resonance study of the relaxation effect in practical lithium ion batteries en-subtitle= kn-subtitle= en-abstract= kn-abstract=Lithium ion cells comprising actual components of positive electrodes (LiCoO2, LiNixCoyAlz, and LiMn2O4) and negative electrodes (graphite and hard carbon) were assembled for in situ7Li nuclear magnetic resonance (NMR) experiments. The 7Li NMR measurements of the cells revealed a grelaxation effecth after overcharging: a decrease of the signal assigned to Li metal deposited on the negative electrode surface by overcharging. The reduction of the Li metal signal was inversely proportional to the increase of the signal of lithium stored in carbon. Therefore, the effect was ascribed to absorption of deposited lithium into the carbon of negative electrodes. The effect, which occurred rapidly in a few hours, reached an equilibrium state at 8?15 h. The slight shift of deposited metal suggests that dendritic Li easily re-dissolved, although larger Li particles remained. A hard carbon electrode has a greater effect of Li metal relaxation than graphite electrodes do, which is explainable by the bufferable structure of the carbon. Results are expected to be important for the discussion of the state of lithium, and for safer battery design. en-copyright= kn-copyright= en-aut-name=GotohKazuma en-aut-sei=Gotoh en-aut-mei=Kazuma kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=IzukaMisato en-aut-sei=Izuka en-aut-mei=Misato kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=AraiJuichi en-aut-sei=Arai en-aut-mei=Juichi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=OkadaYumika en-aut-sei=Okada en-aut-mei=Yumika kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=SugiyamaTeruyasu en-aut-sei=Sugiyama en-aut-mei=Teruyasu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=TakedaKazuyuki en-aut-sei=Takeda en-aut-mei=Kazuyuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=IshidaHiroyuki en-aut-sei=Ishida en-aut-mei=Hiroyuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= affil-num=1 en-affil= kn-affil=Graduate School of Natural Science & Technology, Okayama University affil-num=2 en-affil= kn-affil=Graduate School of Natural Science & Technology, Okayama University affil-num=3 en-affil= kn-affil=Yamaha Motor Co., Ltd. affil-num=4 en-affil= kn-affil=Yamaha Motor Co., Ltd. affil-num=5 en-affil= kn-affil=Division of Chemistry, Graduate School of Science, Kyoto University affil-num=6 en-affil= kn-affil=Natl Inst Mat Sci affil-num=7 en-affil= kn-affil=Graduate School of Natural Science & Technology, Okayama University END