How to refine manganese metal from manganese(IV) oxide found in batteries?
You may heat mixture of $\ce{MnO2}$ with charcoal to higher than $\pu{850 °C},$ in the absence of air. Manganese will be produced in the solid state by reduction of the oxide. But it is sensitive to air oxidation and easily reoxidized. So better use an excess of charcoal. In the industry, rough $\ce{MnO2}$ out of the mine is first reduced to $\ce{MnO}$ by $\ce{CO}$, then leached and reduced into $\ce{Mn}$ metal by a solution of $\ce{Fe^{2+}}$ in the absence of air. Metallic manganese is then dissolved in sulfuric acid and then reduced by electrolysis. See &quot;Manganese metal&quot; over Wikipedia.