The chemical formula of manganese oxide is MnO2. It has a black-brown colour. It is found naturally as pyrolusite and is one of the main sources of manganese in nature.
It is used in dry cell batteries: alkaline and Leclanche cells (zinc-carbon). Approximately 500,000 tonnes are consumed annually.
MnO2 is also useful for many chemical reactions. It can react with oxidizing acids such as sulfuric acid and nitric acid, and it resists the attack of halogens (except hydrofluoric acid).
There are a number of other compounds that are commonly called manganese oxides, but this is the most common. Most people associate MnO2 with the innards of a dry cell battery, but it is actually found in many other applications including ceramics and glassmaking.
It can be prepared by adding hydrogen peroxide to potassium permanganate. The resulting manganese dioxide is insoluble in water, but soluble in acid.
In the lab, it is used as an oxidizing agent to prepare manganese compounds. It is a moderately strong oxidizing agent and is non-stoichiometric.
Because it is a non-stoichiometric oxide, it is susceptible to dehydration by heating. It is also prone to corrode stainless steels and other metals if it is stored in them.
It is available in powder, sputtering targets, tablets and nanopowder. It is usually pulled from D cell zinc alkaline batteries and is very low grade.