NICKEL COMPOSITE HYDROXIDE AND PROCESS FOR PRODUCING SAME

Abstract

A nickel composite hydroxide containing reduced amounts of sulfate radicals and chlorine as impurities. The nickel composite hydroxide is represented by Ni.sub.1-x-yCo.sub.xAl.sub.y(OH).sub.2+α(0.05≦x≦0.01≦y≦0.2, x+y<0.4, and 0≦α<0.5), and includes spherical secondary particles formed by aggregation of plurality of plate-shaped primary particles, secondary particles have an average particle diameter of 3-20 μm, sulfate radical content of 1.0 mass % or less, chlorine content of 0.5 mass % or less, and carbonate radical content of 1.0-2.5 mass %. The nickel composite hydroxide is obtained by a process including a crystallization step in which crystallization is performed in reaction solution obtained by adding alkali solution to aqueous solution containing mixed aqueous solution containing nickel and cobalt, ammonium ion supplier, and aluminum source. The alkali solution is mixed aqueous solution of alkali metal hydroxide and carbonate, and ratio of carbonate to alkali metal hydroxide in mixed aqueous solution represented by [C0.sub.3.sup.2−]/[OH.sup.−]=0.002 or more but 0.050 or less.

Claims

1. A nickel composite hydroxide represented by a general formula: Ni.sub.z-x-yCo.sub.xAl.sub.y(OH).sub.2+α(0.05≦x≦0.35, 0.01≦y≦0.2, x+y<0.4, and 0≦α≦0.5), the nickel composite hydroxide comprising: spherical secondary particles formed by aggregation of a plurality of plate-shaped primary particles, wherein the secondary particles have an average particle diameter of 3 μm to 20 μm, a sulfate radical content of 1.0 mass % or less, a chlorine content of 0.5 mass % or less, and a carbonate radical content of 1.0 mass % to 2.5 mass %.

2. The nickel composite hydroxide according to claim 1 whose value of [(d90-d10)/average particle diameter], which is an index indicating dispersion of particle size distribution of the nickel composite hydroxide, is 0.55 or less

3. The nickel composite hydroxide according to claim 1 whose specific surface area is 15 m.sup.2/g to 60 m.sup.2/g.

4. A process for producing a nickel composite hydroxide by a crystallization reaction, the process comprising: a crystallization step in which crystallization is performed in a reaction solution obtained by adding an alkali solution to an aqueous solution containing a mixed aqueous solution containing nickel and cobalt, an ammonium ion supplier, and an aluminum source, wherein the alkali solution is a mixed aqueous solution of an alkali metal hydroxide and a carbonate, and a ratio of the carbonate to the alkali metal hydroxide in the mixed aqueous solution represented by [CO.sub.3.sup.2−]/[OH.sup.−] or more but 0.050 or less.

5. The process for producing a nickel composite hydroxide according to claim 4, wherein in the crystallization step, an aqueous sodium aluminate solution is used as the aluminum source, and a mole ratio of sodium to aluminum (Na/Al) in the aqueous sodium aluminate solution is L5 to 3.0.

6. The process for producing a nickel composite hydroxide according to claim 4, wherein the crystallization step comprises a nucleation step and a particle growth step, and wherein in the nucleation step, nucleation is performed in the reaction solution by adding the alkali solution to the aqueous solution such that a pH of the reaction solution is 12.0 to 13.4 as a pH measured on a basis of a liquid temperature of 25° C., and in the particle growth step, the alkali solution is added to the reaction solution containing nuclei formed in the nucleation step such that a pH of the reaction solution is 10.5 to 12.0 as a pH measured on a basis of a liquid temperature of 25° C.

7. The process for producing a nickel composite hydroxide according to claim 4, wherein the alkali metal hydroxide is at least one selected from lithium hydroxide, sodium hydroxide, and potassium hydroxide.

8. The process for producing a nickel composite hydroxide according to claim 4, wherein the carbonate is at least one selected from sodium carbonate, potassium carbonate, and ammonium carbonate.

9. The process for producing a nickel composite hydroxide according to claim 4, wherein in the crystallization step, an ammonia concentration of the reaction solution is maintained in a range of 3 g/L to 25 g/L.

10. The process for producing a nickel composite hydroxide according to claim 4, wherein in the crystallization step, a reaction temperature is maintained in a range of 20° C. to 80° C.

Description

EXAMPLES

[0134] Hereinbelow, the present invention will be described in more detail with reference to examples and comparative examples, but is not limited to these examples. It is to be noted that the examples and the comparative examples were evaluated based on measurement results obtained using devices and methods that will be described below.

[0135] A nickel composite hydroxide obtained by a crystallization step described in each of Examples 1 to 15 and Comparative Examples 1 to 3 was washed, subjected to solid-liquid separation, and dried to collect a powder, and the powder was subjected to various analyses by the following methods.

[0136] The composition of the nickel composite hydroxide was determined by measuring a sample obtained by dissolving the nickel composite hydroxide in nitric acid with an inductively-coupled plasma (ICP) emission spectrometer (ICPS-8100 manufactured by SHIMADZU CORPORATION).

[0137] The sulfate radical content of the nickel composite hydroxide was determined by measuring the amount of a sulfur element in a sample obtained by dissolving the nickel composite hydroxide in nitric acid with an ICP emission spectrometer (ICPS-8100 manufactured by SHIMADZU CORPORATION) and then converting the measured amount of a sulfur element into the mount of SO.sub.4.

[0138] The chlorine content of the nickel composite hydroxide was measured with an automatic titrator (COM-1600 manufactured by HIRANUMA SANGYO Co., Ltd.).

[0139] The carbonate radical content of the nickel composite hydroxide was determined by measuring the total carbon element content of the nickel composite hydroxide with a carbon/sulfur analyzer (CS-600 manufactured by LECO) and converting the measured total carbon element content into the amount of CO.sub.3.

[0140] The specific surface area of the nickel composite hydroxide was measured by a BET method using a specific surface area analyzer (QUANTASORB QS-10 manufactured by Yuasa-Ionics Co., Ltd.).

[0141] A lithium nickel composite oxide was produced and evaluated in the following manner. The nickel composite hydroxide particles produced in each of Examples and Comparative Examples were heat-treated in an air flow (oxygen: 21 vol %) at 700° C. for 6 hours, and nickel composite oxide particles were collected. Then, lithium hydroxide was weighed so that the ratio of Li/Me was 1.025, and was mixed with the collected nickel composite oxide particles to prepare a mixture. The mixing was performed using a shaker mixer (TURBULA Type T2C manufactured by Willy A Bachofen (WAB)).

[0142] Then, the obtained mixture was subjected to pre-calcination at 500° C. for 4 hours and then finally calcined at 730° C. for 24 hours in an oxygen flow (oxygen: 100 vol %), cooled, and then disintegrated to obtain a lithium nickel composite oxide.

[0143] The sulfate radical content of the obtained lithium nickel composite oxide was determined by measuring the amount of a sulfur element in a sample obtained by dissolving the lithium nickel composite oxide in nitric acid with an ICP emission spectrometer (ICPS-8100 manufactured by SHIMADZU CORPORATION) and then converting the measured amount of a sulfur element into the amount of SO.sub.4.

[0144] The Li site occupancy factor of the lithium nickel composite oxide, which represents crystallinity, was calculated by Rietveld refinement from a diffraction pattern obtained using an X-ray diffractometer (X'Pert PRO manufactured by PANalytical).

[0145] It is to be noted that in each of Examples and Comparative Examples, a nickel composite hydroxide was produced using special grade reagents manufactured by Wako Pure Chemical industries, Ltd.

Example 1

[0146] A nickel composite hydroxide was produced in the following manner using the process according to the present invention.

[0147] First, 0.9 L of water was placed in a reaction vessel (5 L), and the temperature in the reaction vessel was set to 50° C. while the water in the reaction vessel was stirred. Nitrogen gas was flowed into the reaction vessel to create a nitrogen atmosphere. At this time, the concentration of oxygen in the internal space of the reaction vessel was 2.0%.

[0148] Then, appropriate amounts of a 25% aqueous sodium hydroxide solution and 25% ammonia water were added to the water contained in the reaction vessel so that the pH of the reaction solution in the vessel was adjusted to 12.8 as a pH measured on the basis of a liquid temperature of 25° C. Further, the concentration of ammonia in the reaction solution was adjusted to 10 g/L.

[0149] Then, nickel sulfate and cobalt chloride were dissolved in water to prepare a 2.0 mol/L mixed aqueous solution. The mixed aqueous solution was adjusted so that the mole ratio among the metal elements was Ni:Co=0.84:0.16. Separately, sodium aluminate was dissolved in a predetermined amount of water, and a 25% aqueous sodium hydroxide solution was added thereto so that the ratio of sodium to aluminum was 1.7. Further, sodium hydroxide and sodium carbonate were dissolved in water so that [CO.sub.3.sup.2−]/[OH.sup.−] was 0.025 to prepare an alkali solution.

[0150] The mixed aqueous solution was added to the reaction solution in the reaction vessel at 12.9 mL/min. At the same time, the aqueous sodium aluminate solution, 25% ammonia water, and the alkali solution were also added to the reaction solution in the reaction vessel at constant rates so that the pH of the reaction solution was controlled to be 12.8 (nucleation pH) while the concentration of ammonia in the reaction solution was maintained at 10 g/L. In this way, nucleation was performed by crystallization for 2 minutes 30 seconds. The addition rate of the aqueous sodium aluminate solution was adjusted so that the mole ratio among the metal elements in a slurry was Ni:Co:Al=81:16:3.

[0151] Then, 64% sulfuric acid was added until the pH of the reaction solution reached 11.6 (particle growth pH) as a pH measured on the basis of a liquid temperature of 25° C. Then, after the pH of the reaction solution reached 11.6 as a pH measured on the basis of a liquid temperature of 25° C., particle growth was performed by crystallization for 4 hours by again supplying the mixed aqueous solution, the aqueous sodium aluminate solution, 25% ammonia water, and the alkali solution while controlling the pH at 11.6 to obtain a nickel composite hydroxide.

Example 2

[0152] In Example 2, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the alkali solution was prepared so that [CO.sub.3.sup.2−]/[OH.sup.−] was 0.003.

Example 3

[0153] In Example 3, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example I except that the alkali solution was prepared so that [CO.sub.3.sup.2−]/[OH.sup.−] was 0.040.

Example 4

[0154] In Example 4, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that when sodium aluminate was dissolved in a predetermined amount of water, a 25% aqueous sodium hydroxide solution was added so that the ratio of sodium to aluminum was 1.0.

Example 5

[0155] In Example 5, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that when sodium aluminate was dissolved in a predetermined amount of water, a 25% aqueous sodium hydroxide solution was added so that the ratio of sodium to aluminum was 3.5.

Example 6

[0156] In Example 6, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the pH in the nucleation step was 13.6.

Example 7

[0157] In Example 7, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the pH in the nucleation step was 11.8.

Example 8

[0158] In Example 8, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the pH in the particle growth step was 12.3.

Example 9

[0159] In Example 9, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the pH in the particle growth step was 10.2.

Example 10

[0160] In Example 10, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the addition rate of the aqueous sodium aluminate solution was adjusted so that the mole ratio among the metal elements in a slurry was Ni:Co:Al=78:15:7.

Example 11

[0161] In Example 11, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the addition rate of the aqueous sodium aluminate solution was adjusted so that the mole ratio among the metal elements in a slimy was Ni:Co:Al=74:14:12.

Example 12

[0162] Example 12, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the addition rate of the aqueous sodium aluminate solution was adjusted so that the mole ratio among the metal elements in a slurry was Ni:Co:Al=69:13:18.

Example 13

[0163] In Example 13, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the alkali solution was prepared using potassium hydroxide as an alkali metal hydroxide and potassium carbonate as a carbonate.

Example 14

[0164] In Example 14, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that sodium carbonate was changed to ammonium carbonate and the ammonia concentration was adjusted to 20 g/L.

Example 15

[0165] In Example 15, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the temperature in the reaction vessel was set to 35° C.

Comparative Example 1

[0166] In Comparative Example 1, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example I except that the alkali solution was prepared using only sodium hydroxide so that [CO.sub.3.sup.2−]/[OH.sup.−] was 0.

Comparative Example 2

[0167] In Comparative Example 2, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the alkali solution was prepared so that [CO.sub.3.sup.2−]/[OH.sup.−] was 0.001.

Comparative Example 3

[0168] In Comparative Example 3, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the alkali solution was prepared so that [CO.sub.3.sup.2−]/[OH.sup.−] was 0.055.

Evaluation

[0169] The production conditions of the nickel composite hydroxides obtained in Examples 1 to 15 and Comparative Examples 1 to 3 are shown in Table 1. Further, the evaluation results of the nickel composite hydroxides are shown in Table 2, and the evaluation results of the lithium nickel composite oxides are shown in Table

[0170] As shown in Table 2, the nickel composite hydroxides obtained in Examples 1 to 15 have an average particle diameter of 3 to 20.sub.4m, a sulfate radical content of 1.0 mass % or less, a chlorine content of 0.5 mass % or less, and a carbonate radical content of 1.0 mass % to 2.5 mass %. Further, as can be seen from Table 3, the lithium nickel composite oxides obtained in Examples 1 to 15 have a Li site occupancy factor, which represents crystallinity, of higher than 99.0%, and are therefore excellent in crystallinity and useful as a positive electrode active material.

[0171] On the other hand, as shown in Tables 1 and 2, in Comparative Examples 1 and 2, [CO.sub.3.sup.2−]/[OH.sup.−] representing the mixing ratio between the alkali metal hydroxide and the carbonate in the alkali solution was lower than 0.002, and therefore the sulfate radical content and the chlorine content were high. Further, as shown in Table 3, the lithium nickel composite oxides obtained in Comparative Examples 1 and 2 had a Li site occupancy factor, which represents crystallinity, of lower than 99.0%, and were therefore inferior to that obtained in Example 1 having the same composition ratio.

[0172] In Comparative Example 3, [CO.sub.3.sup.2−]/[OH.sup.−] representing the mixing ratio between the alkali metal hydroxide and the carbonate in the alkali solution was higher than 0.050, and therefore the carbonate radical content was high. Further, the lithium nickel composite oxide obtained in Comparative Example 3 had a Li site occupancy factor, which represents crystallinity, of lower than 99.0%, and was therefore inferior to that obtained in Example I having the same composition ratio.

[0173] Further, the nickel composite hydroxides obtained in Examples 1 to 3 and 10 to 15, in which Na/Al in sodium aluminate was in the range of 1.5 to 3.0, the pH in the nucleation step was in the range of 12.0 to 13.4, and the pH in the particle growth step was in the range of 10.5 to 12.0, had a narrower particle size distribution and a more appropriate specific surface area as compared to the nickel composite hydroxides obtained in Examples 4 to 9 in which one of these conditions was not satisfied.

[0174] As can be seen from the above results, when nickel composite hydroxide particles are produced using the process for producing a nickel composite hydroxide according to the present invention, a lithium nickel composite oxide having high crystallinity is obtained, and such a lithium nickel composite oxide is useful as a positive electrode material for high-capacity non-aqueous electrolyte secondary batteries.

TABLE-US-00001 TABLE 1 pH in pH in Concentration Reaction [CO.sub.3.sup.2]/ nucleation particle Alkali metal of ammonia temperature Ni:Co:Al [OH] Na/Al step growth step hydroxide Carbonate [g/L] [° C.] Example 1 81:16:3 0.025 1.7 12.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 2 81:16:3 0.003 1.7 12.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 3 81:16:3 0.040 1.7 12.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 4 81:16:3 0.025 1.0 12.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 5 81:16:3 0.025 3.5 12.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 6 81:16:3 0.025 1.7 13.6 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 7 81:16:3 0.025 1.7 11.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 8 81:16:3 0.025 1.7 12.8 12.3 Sodium hydroxide Sodium carbonate 10 50 Example 9 81:16:3 0.025 1.7 12.8 10.2 Sodium hydroxide Sodium carbonate 10 50 Example 10 78:15:7 0.025 1.7 12.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 11 74:14:12 0.025 1.7 12.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 12 69:13:18 0.025 1.7 12.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 13 81:16:3 0.025 1.7 12.8 11.6 Potassium hydroxide Potassium carbonate 10 50 Example 14 81:16:3 0.025 1.7 12.8 11.6 Sodium hydroxide Ammonium carbonate 20 50 Example 15 81:16:3 0.025 1.7 12.8 11.6 Sodium hydroxide Sodium carbonate 10 35 Comparative 81:16:3 — 1.7 12.8 11.6 Sodium hydroxide — 10 50 Example 1 Comparative 81:16:3 0.001 1.7 12.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 2 Comparative 81:16:3 0.055 1.7 12.8 11.6 Sodium hydroxide Sodium carbonate 10 50 Example 3

TABLE-US-00002 TABLE 2 Carbonate Average particle (d90-d10)/ Specific surface Sulfate radical Chlorine radical diameter average particle area [mass %] [mass %] [mass %] [μm] diameter [m.sup.2/g] Example 1 0.58 0.11 1.3 7.2 0.48 36 Example 2 0.45 0.09 2.4 6.9 0.47 34 Example 3 0.67 0.15 1.0 7.0 0.49 40 Example 4 0.60 0.12 1.2 7.1 0.57 52 Example 5 0.61 0.12 1.4 7.3 0.58 61 Example 6 0.57 0.11 1.5 5.9 0.57 65 Example 7 0.62 0.14 1.3 7.7 0.59 41 Example 8 0.61 0.13 1.4 5.1 0.60 45 Example 9 0.62 0.14 1.6 7.0 0.59 50 Example 10 0.62 0.13 1.5 6.8 0.51 41 Example 11 0.65 0.12 1.4 6.7 0.51 45 Example 12 0.64 0.13 1.5 6.5 0.53 46 Example 13 0.56 0.12 1.2 7.5 0.49 38 Example 14 0.55 0.11 1.4 7.3 0.48 33 Example 15 0.60 0.12 1.3 6.5 0.51 42 Comparative Example 1 1.20 0.61 0.5 7.1 0.49 31 Comparative Example 2 1.10 0.54 0.6 7.0 0.47 32 Comparative Example 3 0.55 0.10 3.1 7.5 0.59 62

TABLE-US-00003 TABLE 3 Sulfate radical content Li site of the lithium nickel occupancy composite oxide [mass %] factor Example 1 0.57 99.2 Example 2 0.46 99.3 Example 3 0.68 99.1 Example 4 0.61 99.1 Example 5 0.61 99.0 Example 6 0.56 99.0 Example 7 0.61 99.2 Example 8 0.62 99.1 Example 9 0.62 99.0 Example 10 0.63 99.1 Example 11 0.66 99.0 Example 12 0.64 99.0 Example 13 0.62 99.2 Example 14 0.55 99.2 Example 15 0.54 99.1 Comparative Example 1 1.20 98.4 Comparative Example 2 1.20 98.6 Comparative Example 3 0.58 98.1

[0175] The nickel composite hydroxide according to the present invention can be used as a precursor of a battery material not only for electric cars driven only by electric energy but also for so-called hybrid cars that also use a combustion engine such as a gasoline engine or a diesel engine. It is to be noted that power sources for electric cars include not only power sources for electric cars drive only by electric energy but also power sources for so-called hybrid cars that also use a combustion engine such as a gasoline engine or a diesel engine, and a non-aqueous electrolyte secondary battery using a positive electrode active material obtained using the nickel composite hydroxide according to the present invention as a precursor can also be suitably used as a power source for such hybrid cars.