Development of Secondary Batteries by suing Graphite Intercalation Compounds

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The purpose of the present research project is to understand the basic electrochemical reactions on graphite intercalation compounds (GICs) which have high activity by keeping electrochemicall active materials in the gallery of graphite structure and also have high electrical conductivity.1. Development of secondary batteries with acceptor-type GICs.Ternary Ni (OH) _2-Fe (OH) _3 and Ni (OH) _2-Cu (OH) _2-GICs were prepared from corresponding metal chlorides-GICs by electrolysis in KOH aqueous solution. A secondary battery by using Ni (OH) _2-GICs as cathode showed excellent performance of charging and discharging processes. The activation energy for the discharging process in these ternary GICs was determined to be about 2 kcal/mol, which was roughly half of that in a conventional electrode of a mixture of Ni (OH) _2 and graphite powders. This low value of activation energy was supposed to make the discharge with large current density possible.The formation of bromine-GICs was found by … More anodic oxidation of host graphite in KBr aqueous solution. On the process of reduction, two potential plateaux were observed, which seemed to correspond to stage transformation processes during de-intercalation. This suggests a new possibility to develop a secondary battery with simple construction.2. Fundamental studies on the development of secondary batteries with donor-type GICs.Electrochemical intercalation and de-intercalation of alkali metal ions (Li^+, Na^+, K^+ and Rb^+) were studied by cyclic voltammetry. Well-defined intercalation and de-intercalation processes were detected and the stage-2 GICs with respective alkali metal ions were obtained by electrochemical intercalation. From the changes of electrode potential with time, K-GIC was suggested to have low degree of self discharging.Potassium-GICs could absorb large amount of gases, such as hydrogen, ammonia, tetrahydrofuran, benzene, etc. The changes of electrical conductivity, magnetoresistance and Hall coefficient of the K-GICs with the absorption of these gases were studied in-situ. A back-donnation of conduction electrons from graphite to intercalate layers were observed by the absorption of ammonia. Less