Stephen Thurgate

A new class of rechargeable manganese dioxide electrode (MnO2) in aqueous electrolyte is described. Intercalation of lithium from the LiOH electrolyte into the vacant sites of a host MnO2 has been achieved electrochemically is good news. The formation of a lithium carbonate layer from a LiOH electrolyte acts as a barrier for protons while permitting lithium ion insertion in aqueous solutions forming lithium intercalated manganese dioxide (LixMnO2) upon discharge. This novel mechanism may be a key in transferring primary to secondary batteries using LiOH as electrolyte.

Intercalation of lithium into the vacant sites of a host compound can be achieved electrochemically using non-aqueous electrolytes. The use of aqueous electrolyte is less common because of the reactivity of many lithium intercalation compounds with water. Here we propose that lithium could be intercalated using aqueous solutions, lithium hydroxide as the electrolyte. The X-ray photoelectron spectroscopy (SIMS) data on the discharged material indicate that lithium is intercalated into the host structure of EMD without the destruction of its core structure. A significant improvement on cell performance was obtained by adding small amounts (<3 wt%) of titanium disulphide (TiS2) to the cathode.

The discharge characteristics of manganese dioxide cathode in the presence of small amounts (1, 3 and 5 wt. %) of titanium disulphide (TiS2) additive has been investigated in an alkaline cell using aqueous lithium hydroxide as the electrolyte. The incorporation of small amounts of TiS2 additives into manganese dioxide (MnO2) was found to improve the battery discharge capacity from 150 to 270 mAh/g. However, increasing the additive from 3 to 5 wt. % causes a decrease in the discharge capacity. Hence, the objective is to gain insight into the role of TiS2 in MnO2 and its mechanism. For this purpose, we have used transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS) and secondary ion mass spectrometry (SIMS). The valence state determination and the depth profile analysis of the discharged MnO2 were performed using EELS and SIMS techniques.

The electrochemical behavior of lithium manganese phosphate (LIMnPO4) as a cathode material has been investigated in a saturated aqueous lithium hydroxide electrolyte. The crystal structure and surface characterization of the olivine type L1MnPO4 and the products which arc formed on its oxidation and subsequent reduction were studied. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Secondary ion mass spectrometry (SIMS) were used for these investigations. LIMnPO4 is found to be reversibly delithiated on electro oxidation.