Cathodic activity of deep-sea manganese nodule in Leclanché-type test dry cell

The present study has examined the performance of the manganese nodule by incorporating it into the Leclanché cathode mix of D-size test cells.It has been found that, with the particular species collected from the Pacific Ocean, off-shore California, the value of O.C.V. was about 1.62 V, which is quite close to the value with naturally occurring manganese dioxide ores of battery grade. An intermittent discharge on a 4 Ω load, down to a cut-off voltage of 0.75 V, showed approximately half the service duration time obtained with E.M.D.However, when taking into consideration a low MnO₂ content of about 38% in the deep-sea ore tested and the various constituent elements present therein together, the exhibited performance as battery cathode active material was quite surprising.Digestion of the deep-sea nodule with hot sulfuric acid revealed that almost all the original content of MnO₂ was retained in the digested residue, while a 10–20 per cent portion of the accompanying elements was brought into the digesting solution. The “up-graded” MnO₂ product of nodule showed a better battery performance in accordance with the increase in MnO₂ content.These results suggest that the MnO₂ phase present in the manganese nodule might be quite similar to the one possessed by the cathode active γ-MnO₂ species, and that the MnO₂ crystalline net work formation mechanisms involved in “autoclave” of the deep sea might have something in common with the anode oxidation product synthesized by electrolysis.