Method for producing nickel powder having low carbon concentration and low sulfur concentration

A method of producing nickel powder having low carbon and sulfur concentrations, the method sequentially comprising:

• a complexing treatment of adding a complexing agent to a nickel sulfate aqueous solution to prepare a solution containing nickel complex ions;
• a hydrogen reduction treatment of charging the solution containing nickel complex ions in a pressure vessel, maintaining the solution at a solution temperature of 150 to 250° C., and blowing hydrogen gas into the solution containing nickel complex ions to perform hydrogen reduction to produce nickel powder;
• a water-washing treatment of washing the nickel powder with water of which amount is at least equal to and at most 5 times larger than a weight of the nickel powder at a solution temperature of 50 to 90° C., or of subjecting a mixture of the nickel powder and water to ultrasonic washing at atmospheric pressure or below, to thereby produce nickel powder having a content level of sulfur reduced by 95% from the content level of sulfur in the nickel powder obtained in the hydrogen reduction treatment and having a content level of carbon reduced by 65% from the content level of the carbon in the nickel powder obtained in the hydrogen reduction treatment;
• and
• a roasting treatment of roasting the nickel powder washed with water in a mixed gas atmosphere of hydrogen having a concentration of 2 to 4% by weight and nitrogen, and thereby causing the content level of the sulfur to be reduced further from the content level of the sulfur obtained in the water-washing treatment and causing the content level of the carbon to be reduced further from the content level of the carbon obtained in the water-washing treatment nickel.