Equilibrium Potentials of Spinel‐Type Manganese Oxide in Aqueous Solutions

Equilibrium potentials of spinel‐type manganese oxide, , were measured in various aqueous solutions. The electrode showed a near‐Nernstian response to lithium ions and not to other alkali metal and alkaline earth metal ions in the concentration range between . The selectivity coefficents for lithium ions against sodium, and potassium ions and protons were found to be: , , and . The equilibrium potential was stable and pH‐independent over a wide pH range (pH 4 to 9.5) in a solution with a lithium ion concentration above 5 mmol/dm3. The thermodynamic parameters for Li+ insertion/extraction with were evaluated from the temperature dependence of the equilibrium potentials in the temperature range between 298.15 and 318.15 K.