Process for preparing transition metal hydroxides

Abstract

The present invention relates to a process for preparing transition metal hydroxides with a mean particle diameter in the range from 6 to 12 m (D50), which comprises combining, in a stirred vessel, at least one solution of at least one transition metal salt with at least one solution of at least one alkali metal hydroxide to prepare an aqueous suspension of transition metal hydroxide, and, in at least one further compartment, continuously introducing a mechanical power in the range from 50 to 10 000 W/l in a proportion of the suspension in each case, based on the proportion of the suspension, and then recycling the proportion into the stirred vessel.

Claims

1. A process for preparing transition metal hydroxides having a mean particle diameter in the range from 6 to 12 m (D50), the process comprising: combining, in a stirred vessel, a solution of a transition metal salt with a solution of an alkali metal hydroxide to prepare an aqueous suspension of transition metal hydroxide; continuously withdrawing a volume of the suspension from the stirred vessel and supplying to at least one separately powered compartment; continuously introducing, in the at least one separately powered compartment, a mechanical power in the range from 50 to 10,000 W/l in each case, based on the volume of the suspension; and then recycling the volume from said at least one separately powered compartment back into the stirred vessel.

2. The process according to claim 1, wherein the transition metal is at least one selected from the group consisting of Cr, V, Mn, Ni, Fe, Co, Zn, and mixtures of one or more of the aforementioned with one another or with alkali metal, aluminum or magnesium.

3. The process according to claim 1 wherein an overall mean power in the range from 2 to 25 W/l is introduced based on overall suspension.

4. The process according to claim 1, wherein at least 20% of the mechanical power introduced overall is introduced at a power density of from 50 to 10,000 W/l.

5. The process according to claim 1, wherein the separately powered compartment is at least one selected from the group consisting of a pump, an insert, a mixing unit, a wet mill, a stirred tank and a homogenizer.

6. The process according to claim 1, wherein the separately powered compartment is connected to the stirred vessel via a pumped circulation system.

7. The process according to claim 1, wherein a mean solids content of the suspension in the range from 70 to 1000 g/l is employed.

8. The process according to claim 1, wherein the transition metal is selected from mixtures of Ni, Mn, Co and optionally at least one further metal selected from the group consisting of alkali metal, aluminum and magnesium.

9. The process according to claim 1, wherein precipitated transition metal hydroxide is removed from a mother liquor, and particles with a diameter greater than 50 m are removed.

10. The process according claim 9, wherein particles of transition metal hydroxide with a diameter greater than 30 m are removed.

Description

1. INVENTIVE EXAMPLE 1

(1) The reactor system was purged with 40 l (STP)/h of nitrogen (standard liters). Then solutions A and B were metered by means of metering pumps at constant mass flow (301 g/h and 200 g/h respectively) into the turbulent zone close to the stirrer blades of the stirred tank of the reactor system. A regulating device was used to keep the pH constant at 11.3 by means of addition of solution C. A suspension formed. The temperature of the suspension was adjusted to 45 C. The pH was adjusted to 11.3 by adding solution C (measured at 23 C.). The mean residence time of the suspension in the reactor system was 15 hours. After 3 days, the steady state had been attained.

(2) The stirrer output was 40 W, the power introduced in the assembly 45 W. The flow rate in the assembly was 1200 l/h.

(3) A suspension of transition metal hydroxide with a molar Ni:Co:Mn ratio of 33:34:33 was obtained. The transition metal hydroxide suspension obtained from the overflow was filtered through a suction filter; the filtercake was washed with water, 3% by weight of NaOH and water again, and dried at 105 C. over a period of 12 hours. The inventive transition metal hydroxide TM.1 thus obtainable (21.2% Ni; 22.1% Co; 20.3% Mn; formula Ni.sub.0.33Co.sub.0.34Mn.sub.0.33(OH).sub.1.17O.sub.0.83(SO.sub.4).sub.0.003) was sieved (mesh size 50 m) and the tamped density was determined.

(4) To determine the tamped density in an electrode material, a portion of the transition metal hydroxide TM.1 was mixed with lithium carbonate and heat treated at 900 C. For this purpose, 41.18 g of lithium carbonate (99.6% Li.sub.2CO.sub.3, sieved, 100%<50 m) were mixed with 90.35 g of transition metal hydroxide TM.1 in a ball mill, and the mixture was transferred to a crucible and calcined in a muffle furnace (heat to 350 C. for 107 minutes, hold for 4 hours, heat to 675 C. for 107 minutes, hold for 4 hours, heat to 900 C. for 75 minutes, hold for 6 hours; then cool to room temperature in the furnace). The resulting material was sieved<32 m and the tamped density was determined.

2. COMPARATIVE EXAMPLE C-2

(5) The procedure was as described in 1, except that the assembly and the pumped circulation system were closed.

(6) A suspension of transition metal hydroxide with a molar Ni:Co:Mn ratio of 33:34:33 was obtained. The metal hydroxide suspension obtained from the overflow was filtered through a suction filter; the filtercake was washed with water, 3% by weight of NaOH and water again, and dried at 105 C. over a period of 12 hours. The transition metal hydroxide C-TM.2 thus obtainable (22.2% Ni; 22.2% Co; 20.0% Mn) was sieved (mesh size 50 m) and the tamped density was determined.

(7) To determine the tamped density in an electrode material (cathode material), a portion of the transition metal hydroxide C-TM.2 was mixed with lithium carbonate and heat treated at 900 C. For this purpose, 41.26 g of lithium carbonate (99.4% Li.sub.2CO.sub.3, sieved, 100%<50 m) were mixed with 89.23 g of transition metal hydroxide C-TM.2 in a ball mill, and the mixture was transferred to a crucible and calcined (heat to 350 C. for 107 minutes, hold for 4 hours, heat to 675 C. for 107 minutes, hold for 4 hours, heat to 900 C. for 75 minutes, hold for 6 hours; then cool to room temperature in the furnace). The resulting material was sieved<32 m and the tamped density was determined.

3. COMPARATIVE EXAMPLE C-3

(8) The procedure was as described in 1, except that a smaller assembly with a capacity of 0.015 l was selected. The flow rate in the assembly was 300 l/h. As a result, only 8 W/53 W, i.e. 15% of the mechanical power, was introduced in the compartment, i.e. at higher power density.

(9) A suspension of transition metal hydroxide with a molar Ni:Co:Mn ratio of 33:34:33 was obtained. The transition metal hydroxide suspension obtained from the overflow was filtered through a suction filter; the filtercake was washed with water, 3% by weight of NaOH and water again, and dried at 105 C. over a period of 12 hours. The transition metal hydroxide C-TM.3 thus obtainable (21.6% Ni; 22.1% Co; 19.8% Mn; formula Ni.sub.0.33Co.sub.0.34Mn.sub.0.33(OH).sub.1.14O.sub.0.86(SO.sub.4).sub.0.003) was sieved (mesh size 50 m) and the tamped density was determined.

(10) To determine the tamped density in an electrode material (cathode material), a portion of the transition metal hydroxide C-TM.3 was mixed with lithium carbonate and heat treated at 900 C. For this purpose, 41.26 g of lithium carbonate (99.4% Li.sub.2CO.sub.3, sieved, 100%<50 m) were mixed with 90.64 g of transition metal hydroxide C-TM.3 in a ball mill, and the mixture was transferred to a crucible and calcined (heat to 350 C. for 107 minutes, hold for 4 hours, heat to 675 C. for 107 minutes, hold for 4 hours, heat to 900 C. for 75 minutes, hold for 6 hours; then cool to room temperature in the furnace). The resulting material was sieved<32 m and the tamped density was determined.

(11) TABLE-US-00001 TABLE 1 Stirred As- TD of (D50) of (D50) tank As- sembly hy- hy- TD of of stirrer sembly power drox- drox- mixed mixed Exam- output output density ide ide oxide oxide ple (W) (W) (W/l) (kg/l) (m) (kg/l) (m) TM.1 40 45 1071 2.26 7.5 2.34 7.7 C-TM.2 39 2.02 6.9 2.14 7.6 C-TM.3 45 8 544 2.05 7.2 2.01 8.2 TD: tamped density, measured with an STAV II tamping volumeter, from Engelsmann, Ludwigshafen, 2000 taps.