A method of producing manganese metal or EMD by leaching a source of manganese with a solution comprising sulfuric acid to form a leach solution, adding one or more sulfides generated in a sulfide recycle stage to the leach solution in order to form sulfide precipitates comprising heavy metal sulfides, removing the sulfide precipitates from the leach solution, feeding the leach solution to one or more electrolytic cells, subjecting the purified leach solution to electrolysis so as to deposit manganese metal or EMD, reacting the sulfide precipitates with an acid to generate H.sub.2S, producing one or more sulfides from the H.sub.2S for recycle. Methods of producing manganese metal and a purified manganese sulfate solution are also provided.

A method of producing manganese metal or EMD by leaching a source of manganese with a solution comprising sulfuric acid to form a leach solution, adding one or more sulfides generated in a sulfide recycle stage to the leach solution in order to form sulfide precipitates comprising heavy metal sulfides, removing the sulfide precipitates from the leach solution, feeding the leach solution to one or more electrolytic cells, subjecting the purified leach solution to electrolysis so as to deposit manganese metal or EMD, reacting the sulfide precipitates with an acid to generate H.sub.2S, producing one or more sulfides from the H.sub.2S for recycle. Methods of producing manganese metal and a purified manganese sulfate solution are also provided.

Provided are an iridium-manganese oxide composite material and an iridium-manganese oxide composite electrode material that are inexpensive and have high catalytic activity for use in an anode catalyst for oxygen evolution associated with water electrolysis. Also provided are methods for producing the same. An iridium-manganese oxide composite material includes a manganese oxide and iridium distributed on at least a surface of the manganese oxide, the iridium having a metal valence of 3.1 or greater and 3.8 or less. An iridium-manganese oxide composite electrode material includes a conductive substrate formed of a fiber, with the iridium-manganese oxide composite material being coated on at least a portion of the conductive substrate.

Disclosed herein is an improved cathode material prepared from high purity electrolytic manganese dioxide. Also disclosed is a method for preparing high purity MnO.sub.2 and converting MnO.sub.2 particles to Mn.sub.2O.sub.3.

Disclosed herein is an improved cathode material prepared from high purity electrolytic manganese dioxide. Also disclosed is a method for preparing high purity MnO.sub.2 and converting MnO.sub.2 particles to Mn.sub.2O.sub.3.

To provide metal-containing trimanganese tetraoxide combined particles with which a metal-substituted lithium manganese oxide excellent as a cathode material for a lithium secondary battery can be obtained, and their production process. Metal-containing trimanganese tetraoxide combined particles containing a metal element (excluding lithium and manganese). Such metal-containing trimanganese tetraoxide combined particles can be obtained by a production process comprising a crystallization step of crystalizing a metal-substituted trimanganese tetraoxide not by means of metal-substituted manganese hydroxide from a manganese salt aqueous solution containing manganese ions and metal ions other than manganese.

To provide metal-containing trimanganese tetraoxide combined particles with which a metal-substituted lithium manganese oxide excellent as a cathode material for a lithium secondary battery can be obtained, and their production process. Metal-containing trimanganese tetraoxide combined particles containing a metal element (excluding lithium and manganese). Such metal-containing trimanganese tetraoxide combined particles can be obtained by a production process comprising a crystallization step of crystalizing a metal-substituted trimanganese tetraoxide not by means of metal-substituted manganese hydroxide from a manganese salt aqueous solution containing manganese ions and metal ions other than manganese.

A method for producing electrolytic manganese dioxide with high compact density where electrolytic manganese dioxide pieces are milled in a classifying mill to produce first milled manganese dioxide particles where 30% of the particles are larger than 200 mesh and up to 95% of the particles are smaller than 325 mesh. The first milled manganese dioxide particles are milled a second time to produce manganese dioxide particles having a second particle size distribution. Also, an electrolytic manganese dioxide particle composition, wherein when the particle size distribution of the composition is plotted as a function of base-10 logarithm of the particle size, a first peak is centered at a particle size from 40-100 m and contributes a minimum of 20% of the area under the curve of the overall particle size distribution and a maximum of 45% of the area under the curve of the overall particle size distribution.

The object of the present invention is to provide electrolytic manganese dioxide excellent in the middle rate discharge characteristic as compared with conventional electrolytic manganese dioxide, and a method for its production and its application. Electrolytic manganese dioxide characterized in that the potential as measured in a 40 wt % KOH aqueous solution by using a mercury/mercury oxide reference electrode as a standard is higher than 250 mV and less than 310 mV, and the volume of pores having a pore diameter of at least 2 nm and at most 50 nm is at most 0.0055 cm.sup.3/g. Of such electrolytic manganese dioxide, the volume of pores having a pore diameter of at least 2 nm and at most 200 nm is preferably at most 0.0555 cm.sup.3/g.

The object of the present invention is to provide electrolytic manganese dioxide excellent in the middle rate discharge characteristic as compared with conventional electrolytic manganese dioxide, and a method for its production and its application. Electrolytic manganese dioxide characterized in that the potential as measured in a 40 wt % KOH aqueous solution by using a mercury/mercury oxide reference electrode as a standard is higher than 250 mV and less than 310 mV, and the volume of pores having a pore diameter of at least 2 nm and at most 50 nm is at most 0.0055 cm.sup.3/g. Of such electrolytic manganese dioxide, the volume of pores having a pore diameter of at least 2 nm and at most 200 nm is preferably at most 0.0555 cm.sup.3/g.