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Mesocarbon microbeads (MCMB) is one of the promising carbon materials as anodes for rechargeable lithium batteries among commercially available carbon materials. We have examined the correlation between carbon structures and chargedischarge characteristics of the MCMBs prepared at different heat‐treatment temperatures. It was found that the MCMB heat‐treated at 700°C possesses a tremendously high charge‐discharge capacity of 750 Ah kg−1 . This suggests that there is another mechanism for the charge‐discharge reaction besides a graphite intercalation compound mechanism which is well known. Therefore, we propose a cavity mechanism in which intercrystallite spaces in MCMB are capable of storing lithium species.

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Carbon is one of the best candidate materials for the negative electrode of rechargeabte lithium batteries; however, the electrochemical characteristics are not fully understood in terms of the structure of the materials. The relationship linking the volume ration of the graphitic structure (P1) of mesocarbon microbeads (MCMBs) and the electrochemical characteristics has been examined, and it was found that the capacity in the range between 0 to 0.25 V (vs. Li/Li +) in 1 tool 9 -~ LiC1OJethylene carbonate (EC) + 1,2-diethoxyethane (DEE) electrolyte increased with an increase of the P1 of the MCMBs. This result shows that the lithium storage mechanism in this potential range is the lithium-intercalation reaction into the graphitic layers with the AB or ABC stacking. On the other hand, MCMB heat-treatment temperature (HTT) 1000~showed much larger capacity in the range between 0.25 to 1.3 V than higher HTT MCMBs, and it is suggested the interaction among each graphite layer is weaker in nongraphitized carbon than that in well-graphitized ones.