A method for producing electrolytic manganese dioxide with high compact density comprising: producing first milled manganese dioxide particles in a classifying mill from electrolytic manganese dioxide pieces by a process comprising dry or wet milling in a ball mill, roller mill or Raymond mill and classification, such that the first milled manganese dioxide particles have a particle size distribution where less than 30% of the first milled manganese dioxide particles are larger than 74 μm (200 mesh) and up to 95% of the first milled manganese dioxide particles are smaller than 44 μm (325 mesh); and milling the first milled manganese dioxide particles in a tumbling mill with milling media of a size of 5 mm to 100 mm for a time of more than 2 minutes to less than 720 minutes to produce second milled manganese dioxide particles, wherein the second milled manganese dioxide particles have a second particle size distribution, wherein when the particle size distribution of the second milled manganese dioxide particles is plotted as a function of base-10 logarithm of the particle size, the particle size distribution comprises a first peak centered at a particle size of 40-100 μm and contributing 20-45 % to the area under the curve of the overall particle size distribution, a second peak centered at a particle size of 15-25 μm, and a third peak centered at a particle size of 0.1-1.0 μm and having a contribution of 20% maximum to the area under the curve of the overall particle size distribution, the particle size distribution was measured by laser diffraction using a Micro Trac 3500 apparatus, the flow rate was set to 60%, the transparency was set to absorbing, particle shape was set to irregular, and a fluid index of 1.333 was used. producing first milled manganese dioxide particles in a classifying mill from electrolytic manganese dioxide pieces by a process comprising dry or wet milling in a ball mill, roller mill or Raymond mill and classification, such that the first milled manganese dioxide particles have a particle size distribution where less than 30% of the first milled manganese dioxide particles are larger than 74 μm (200 mesh) and up to 95% of the first milled manganese dioxide particles are smaller than 44 μm (325 mesh); and milling the first milled manganese dioxide particles in a tumbling mill with milling media of a size of 5 mm to 100 mm for a time of more than 2 minutes to less than 720 minutes to produce second milled manganese dioxide particles, wherein the second milled manganese dioxide particles have a second particle size distribution, wherein when the particle size distribution of the second milled manganese dioxide particles is plotted as a function of base-10 logarithm of the particle size, the particle size distribution comprises a first peak centered at a particle size of 40-100 μm and contributing 20-45 % to the area under the curve of the overall particle size distribution, a second peak centered at a particle size of 15-25 μm, and a third peak centered at a particle size of 0.1-1.0 μm and having a contribution of 20% maximum to the area under the curve of the overall particle size distribution, the particle size distribution was measured by laser diffraction using a Micro Trac 3500 apparatus, the flow rate was set to 60%, the transparency was set to absorbing, particle shape was set to irregular, and a fluid index of 1.333 was used.