Lignin as an Additive Compound to Storage Batteries I.

The functional group and the reaction mechanism of lignin as a battery additive were studied on a small alkaline storage battery specially prepared. The capacity of battery increased with addition of catechol, guaiacol and many chelating agents such as EDTA, as well as with that of lignin. Demethylation of guaiacol in the electrolytic solution was observed and it was proved that the catechol residue reacts as a functional group of lignin in alkaline storage batteries, which is just the same as in the case of lead storage batteries. A significant increase in Cd+2 ion in electrolytic solution was found with addition of lignin and chelating agents including catechol derivatives, which suggested that the increase in capacity should be connected with the chelating effect of the additives with heavy metalic ions of cathode. The Cd+2 ion increased slightly during discharging process and decreased during charging, but the quantity of electricity transported with the Cd0-Cd+2 transformation was too small to interpret the whole increase in capacity.From the potential-time curves of charge-discharge cycle before and after addition of lignin and chelating agents, it is suggested that lignin makes the grain of cathode active material minute quickly during charging process, resulting in an increase in discharging capacity.Attempt was made to probe the mechanism of capacity increase with lignin both from the chelating effect and adsorption of lignin : Dissolved Cd+2-lignin complex will make the grain of active material minute when it deposites on cathode and dissolution of Cd+2 into electrolytic solution will also cause a minuteness of the grain. Violent adsorption of lignin or Cd+2-lignin complex is expected on the surface of cathode, for lignin has a chelating ability with active material. The transformation of Cd0 to Cd+2 or of its reverse on the cathode surface will occur at the opening of the vigorously adsorbed lignin molecule, resulting in rugged surface of cathode. The increase in surface area caused by minimized active material grain will bring with it also discharging capacity increase.