Provided is a method for manufacturing a nickel and cobalt mixed sulfide that is capable of stabilizing nickel and cobalt concentrations in the sulfidation end solution at low levels and of limiting decreases in nickel and cobalt recovery rates without increasing cost even when processing with a sulfuric acid acidic solution containing nickel and cobalt and a high iron ions concentration as the sulfidation start solution. This method for manufacturing a nickel and cobalt mixed sulfide is a method for generating a sulfidation reaction by blowing hydrogen sulfide gas into a sulfuric acid acidic solution comprising nickel and cobalt to obtain a mixed sulfide, wherein: the sulfuric acid acidic solution, which is the sulfidation start solution, contains iron ions at a rate of 1.0-4.0 g/L; and the sulfidation reaction is generated by blowing hydrogen sulfide gas into the sulfidation start solution and adding sodium hydrogensulfide (NaHS) obtained by absorbing hydrogen sulfide gas-containing exhaust gas, generated by the sulfidation, in an alkaline solution.

An object is to provide a method of manufacturing a hexafluorophosphate, that can simply and easily manufacture an inexpensive and high-quality hexafluorophosphate while suppressing the manufacturing cost, an electrolytic solution containing a hexafluorophosphate, and an electricity storage device including the electrolytic solution. The present invention relates to a method of manufacturing a hexafluorophosphate, which comprises reacting at least a phosphorus compound with a fluoride represented by MF_s·r(HF), wherein 0 ≤ r ≤ 6, 1 ≤ s ≤ 3, and M is at least one kind selected from the group consisting of Li, Na, K, Rb, Cs, NH₄, Ag, Mg, Ca, Ba, Zn, Cu, Pb, Al and Fe, to produce a hexafluorophosphate represented by the chemical formula M(PF₆)_s.

The present invention relates to lithium secondary batteries comprising a negative electrode, a positive electrode, a separator and a lithium-based electrolyte carried in an aprotic solvent, and to the electrolyte compositions, and to methods for purifying battery active materials. The electrolyte comprises at least one solvent and a lithium salt of the formula:



         Li₂B₁₂F_xH_12-x-yZ_y



where x+y is from 3 to 12, and x and y are independently from 0 to 12, and Z comprises at least one of Cl and Br.

In the manufacturing method of hexafluorophosphate (MPF₆: M = Li, Na, K, Rb, Cs, NH₄, and Ag) of the present invention, at least a H_xPO_yF_z aqueous solution, a hydrofluoric acid aqueous solution, and MF · r (HF) are used as raw materials (wherein, r ≥ 0, 0 ≤ x ≤ 3, 0 ≤ y ≤ 4, and 0 ≤ z ≤ 6). According to the above description, a manufacturing method of hexafluorophosphate can be provided which is capable of manufacturing hexafluorophosphate (GPF₆: G = Li, Na, K, Rb, Cs, NH₄, and Ag) at a low cost in which the raw materials can be easily obtained, the control of the reaction is possible, and the workability is excellent.

The present invention relates to lithium secondary batteries comprising a negative electrode, a positive electrode, a separator and a lithium-based electrolyte carried in an aprotic solvent, and to the electrolyte compositions, and to methods for purifying battery active materials. The electrolyte comprises at least one solvent and a lithium salt of the formula:



         Li₂B₁₂F_xH_12-x-yZ_y



where x+y is from 3 to 12, and x and y are independently from 0 to 12, and Z comprises at least one of Cl and Br.

Um sowohl eine konzentrierte, möglichst wenig gelöstes Salz enthaltende Natronlauge als auch ein Festsalz mit möglichst geringem Gehalt an NaOH zu erhalten, werden die beim Eindampfen und Abkühlen der Natronlauge aus der NaCl-Elektrolyse anfallenden Mehrfachsalze zersetzt. Dazu wird im Seitenstrom zum Lauge-Hauptstrom der Eindamp-__- fanlage der entnommene Salzbrei zunächst eingedickt, und ein Teil der Natronlauge mit großem NaOH-Gehalt wird durch Lauge mit geringerem NaOH-Gehalt ersetzt. Die Mehrfachsalze werden in einem ebenfalls im Seitenstrom liegenden Zersetzer mittels Natronlauge mit weniger als 30 % NaOH-Gehalt zersetzt. Bei diesem Verfahren wird weder bereits auskristallisiertes Salz aufgelöst noch die Salzbelastung im Haupt-Laugestrom erhöht. Der Verlust an NaOH wird gegenüber den bisher üblichen Verfahren merklich herabgesetzt.