MULTI-STEP PROCESS FOR MAKING CATHODE ACTIVE MATERIALS, AND CATHODE ACTIVE MATERIALS

Abstract

The present invention is related to a process for making an electrode active material wherein said process comprises the following steps: (a) Providing a hydroxide TM(OH).sub.2 or at least one oxide TMO or at least one oxyhydroxide of TM or a combination of at least two of the foregoing wherein TM is one or more metals and contains at least 97 mol-% Ni and, optionally, in total up to 3 mol-% of at least one metal selected from Al, Ti, Zr, V, Co, Zn, Ba, and Mn; (b) mixing said hydroxide TM(OH).sub.2 or oxide TMO or oxyhydroxide of TM or combination with a source of lithium and a source of Mg wherein the molar amount of (Li+Mg) corresponds to 75 to 95 mol-% of TM; (c) treating the mixture obtained from step (b) thermally at a temperature in the range of from 450 to 650° C., thereby obtaining an intermediate; (d) mixing the intermediate from step (c) with a source of Li and with at least one compound of a metal M.sup.1 selected from Al, Zr, Co, Mn, Nb, Ta, Mo, and W; (e) treating the mixture obtained from step (d) thermally at a temperature in the range of from 500 to 850° C.

Claims

1. Process for making an electrode active material wherein said process comprises the following steps: (a) Providing a hydroxide TM(OH)2 or at least one oxide TMO or at least one oxyhydroxide of TM or a combination of at least two of the foregoing wherein TM is one or more metals and contains at least 97 mol-% Ni and, optionally, in total up to 3 mol-% of at least one metal selected from Al, Ti, Zr, V, Co, Zn, Ba, and Mn, (b) mixing said hydroxide TM(OH)2 or oxide TMO or oxyhydroxide of TM or combination with a source of lithium and a source of Mg wherein the molar amount of (Li+Mg) corresponds to 75 to 95 mol-% of TM, (c) treating the mixture obtained from step (b) thermally at a temperature in the range of from 450 to 650° C., thereby obtaining an intermediate, (d) mixing the intermediate from step (c) with a source of Li and with at least one compound of a metal M1 selected from Al, Zr, Co, Mn, Nb, Ta, Mo, and W, (e) treating the mixture obtained from step (d) thermally at a temperature in the range of from 500 to 850° C.

2. Process according to claim 1, wherein the total molar ratio of (Li+Mg) to (TM+M1) is in the range of from 1:1 to 1.05:1.

3. Process according to claim 1, wherein in step (b), the molar ratio of Li to Mg is in the range of from 200:1 to 25:1.

4. Process according to claim 1, wherein the source of Mg is selected from Mg(OH)2 and MgO.

5. Process according to claim 1, wherein in step (b), a source of Al is added.

6. Process according to claim 1, wherein the temperature in step (e) is higher than in step (c).

7. Process according to claim 1, steps (c) and (e) are performed in an atmosphere of at least 80 vol-% oxygen.

8. Process according to claim 1, wherein the molar ratio of M1 to TM is in the range of from 1:50 to 1:250.

9. Particulate electrode active material according to the general formula (LiaMgb)1+x(TMcM1d)1−xO2, wherein TM contains at least 97 mol-% Ni and, optionally, up to 1 mol-% of at least one metal selected from Ti, Al, Zr, V, Co, Zn, Ba, and Mn, M1 is selected from Al, Zr, Co, Mn, Nb, Ta, Mo, and W, a:b is in the range of from 40:1 to 200:1, and a+b=1 c:d is in the range of from 50:1 to 250:1, and c+d=1, total molar ratio of (Li+Mg) to (TM+M.sup.1) is in the range of from 1:1 to 1.05:1, 0.00≤x≤0.05.

10. Particulate electrode active material according to claim 9, wherein TM is nickel.

11. Particulate electrode active material according to claim 9, wherein M1 is Al, Co, Zr or combinations of at least two of the foregoing.

12. Particulate electrode active material according to claim 9, wherein said electrode active material is comprised from secondary particles that are agglomerates of primary particles, and M1 is enriched at the surface of the primary particles.

13. Cathode containing (A) at least one electrode active material according to claim 9, (B) carbon in electrically conductive form, (C) a binder material.

14. Cathode according to claim 13 containing (A) 80 to 98% by weight cathode active material, (B) 1 to 17% by weight of carbon, (C) 3 to 10% by weight of binder material, percentages referring to the sum of (A), (B) and (C).

15. Electrochemical cell containing at least one cathode according to claim 13.

Description

[0147] The present invention is further illustrated by the following working examples.

[0148] Average particle diameters (D50) were determined by dynamic light scattering (“DLS”). Percentages are % by weight unless specifically noted otherwise.

[0149] LiOH.Math.OH was purchased from Rockwood Lithium. Mg(OH).sub.2 was purchased from Sigma Aldrich, Al.sub.2O.sub.3 was purchased from Sasol, and Zr(OH).sub.4 from Luxfer Mel Technologies

[0150] As a mixer, a blender (Kinematica) was used.

I. Manufacture of a Base Cathode Active Material, LiNiO.SUB.2

I.1 Manufacture of a Precursor

[0151] Step (a.1): A spherical Ni(OH).sub.2 precursor was obtained by combining aqueous nickel sulfate solution (1.65 mol/kg solution) with an aqueous 25 wt. % NaOH solution and using ammonia as complexation agent. The pH value was set at 12.6. The freshly precipitated Ni(OH).sub.2 was washed with water, sieved and dried at 120° C. for 12 hours. The resultant Ni(OH).sub.2 (“P-CAM.1”) had an average particle diameter D50 of 10 μm.

II. Manufacture of Inventive Cathode Active Materials, and of Comparative Cathode Active Materials

II.1 Manufacture of C-CAM.1

[0152] Step (b.1): An amount of 50 g of P-CAM.1 was mixed with 22.80 g LiOH.Math.H.sub.2O, 0.32 g Mg(OH).sub.2, 0.15 g Al.sub.2O.sub.3 and 0.25 g Zr(OH).sub.4. [0153] Step (c.1): The resultant mixture was poured into an alumina crucible and heated to 600° C. for one hour and then to 700° C. for 6 hours under oxygen atmosphere (10 exchanges/hour) with a heating rate of 10° C. min.sup.−1 for the first temperature ramp and 3° C. min.sup.−1 for the second ramp. Said heat treatment was performed in laboratory furnace (Linn High Therm). C-CAM.1 was obtained. C-CAM.1 was cooled to 120° C. at a cooling rate of 10° C. min.sup.−1 and transferred into a dry room for further processing.

[0154] Neither a step (d) nor (e) was performed.

[0155] Subsequently, the resultant C-CAM.1 was sieved using a mesh size of 32 μm to C-CAM.1 with 1.0 mol % Mg, 0.55 mol % Al, 0.24 mol % Zr and molar ratio (Li+Mg)/(Ni+Al+Zr)=1.01.

II.2 Manufacture of CAM.2

[0156] Step (b.2): An amount of 50 g of P-CAM.1 was mixed with 17.67 g LiOH.Math.H.sub.2O, 0.25 g Mg(OH).sub.2, and 0.15 g Al.sub.2O.sub.3. [0157] Step (c.2): The resultant mixture was poured into quartz glass bulb that was part of a rotary kiln and heated to 600° C. for one hour under oxygen atmosphere (100 exchanges/hour) with a heating rate of 10° C. min.sup.−1. The rotational speed was 20 rpm. An intermediate was obtained. The resultant intermediate was cooled to ambient temperature at a cooling rate of 10° C. min.sup.−1 and transferred into a dry room for further processing. The composition was 63 wt % Ni, 0.13 wt % Al, 0.18 wt % Mg and 5.51 wt % Li. [0158] Step (d.2): An amount of 40 g of the intermediate from step (c.2) was mixed with 5.23 g Li—OH.Math.H.sub.2O, 0.09 g Mg(OH).sub.2 and 0.21 g Zr(OH).sub.4 using a blender. A mixture was obtained. [0159] Step (e.2): The mixture from step (d.2) was poured into an alumina crucible and heated to 700° C. for 6 hours under oxygen atmosphere (10 exchanges/hour) with a heating rate of 3° C. min.sup.−1 in a laboratory furnace. The resultant CAM.2 was cooled to 120° C. at a cooling rate of 10° C. min.sup.−1 and transferred to a dry room for further processing.

[0160] Subsequently, CAM.2 was sieved using a mesh size of 32 μm with 0.70 mol % Mg, 0.45 mol % Al, 0.24 mol % Zr and molar ratio (Li+Mg)/(Ni+Al+Zr)=1.02 (measured by ICP-OES).

II.3 Manufacture of CAM.3

[0161] Step (b.3): An amount of 50 g of P-CAM.1 was mixed with 17.67 g LiOH.Math.H.sub.2O, 0.25 g Mg(OH).sub.2, and 0.15 g Al.sub.2O.sub.3. [0162] Step (c.3): The resultant mixture was poured into an alumina crucible and heated to 600° C. for one hour and then to 700° C. for 6 hours under oxygen atmosphere (10 exchanges/hour) with a heating rate of 10° C. min.sup.−1 for the first temperature ramp and 3° C. min.sup.−1 for the second ramp. Said heat treatment was performed in laboratory furnace (Linn High Therm). An intermediate was obtained. The resultant intermediate was cooled to ambient temperature at a cooling rate of 10° C. min.sup.−1 and transferred into a dry room for further processing. The composition was 63 wt % Ni, 0.15 wt % Al, 0.21 wt % Mg and 5.79 wt % Li. [0163] Step (d.3): An amount of 40 g of the intermediate from step (c.3) was mixed with 4.37 g LiOH.Math.H.sub.2O, 0.06 g Mg(OH).sub.2 and 0.21 g Zr(OH).sub.4 using a blender. A mixture was obtained. [0164] Step (e.3): The mixture from step (d.2) was poured into an alumina crucible and heated to 700° C. for 6 hours under oxygen atmosphere (10 exchanges/hour) with a heating rate of 3° C. min.sup.−1 in a laboratory furnace. The resultant CAM.3 was cooled to 120° C. at a cooling rate of 10° C. min.sup.−1 and transferred to a dry room for further processing.

[0165] Subsequently, CAM.3 was sieved using a mesh size of 32 μm with 0.8 mol % Mg, 0.5 mol % Al, 0.24 mol % Zr and molar ratio (Li+Mg)/(Ni+Al+Zr)=1.01 (measured by ICP-OES).

III. Electrochemical Testing

III.1 Cathode Manufacture, General Protocol:

[0166] Electrode manufacture: Electrodes contained 94% of the respective CAM or C-CAM.1, 3% carbon black (Super C65) and 3% binder (polyvinylidene fluoride, Solef 5130). Slurries with a total solids content of 61% were mixed in N-methyl-2-pyrrolidone (planetary mixer, 24 minutes, 2,000 rpm) and cast onto aluminum foil tape by a box-type coater. After drying of the electrode tapes for 16 h at 120° C. in vacuo and calendaring, circular electrodes with a diameter of 14 mm were punched, weighed and dried at 120° C. under vacuum for 12 hours before entering in an Ar filled glove box. Average loading: 8 mg/cm.sup.2, electrode density: 3 g/cm.sup.3.

III.2 Coin Cell Manufacture

[0167] Coin-type electrochemical cells were assembled in an argon-filled glovebox. Anode: 0.58 mm thick Li foil, separated from the cathode by a glass fiber separator (Whatman GF/D). An amount of 95 μl of 1 M LiPFe.sub.6 in ethylene carbonate (EC):ethylmethyl carbonate (EMC), 3:7 by weight, was used as the electrolyte. After assembly, the cells were crimped closed in an automated crimper. The cells were then transferred to a climate chamber and connected to a battery cycler (Series4000, MACCOR).

III.3 Coin Cell Testing.

[0168] All tests were performed at 25° C. Cells were galvanostatically cycled at a Maccor 4000 battery cycler between 3.1 and 4.3 V at room temperature by applying the following C-rates until 70% of the initial discharge capacity is reached at a certain discharge step:

[0169] The test protocol consisted of an initial formation & rate test part, starting with two cycles at C/10. For all cycles, the voltage window was set to 3.0-4.3 V. As an initial 1C rate, 200 mA g.sup.−1 were assumed. For all subsequent cycles, the charge was set to CCCV at C/2 and 4.3 V for 30 min or until the current drops below C/100. The cells were discharged at C/5 for five cycles before stepwise increasing the discharge rate (C/10, C/5, C/2, 1C, 2C, 3C). The 1C rate was then adapted to the capacity of the 1C discharge. Following the rate test, the state of charge dependent cell resistance was determined by the DCIR method. After a short potential relaxation, a current pulse of 400 mA g.sup.−1 is applied for 10 s. Following each current pulse, the cell is discharged at C/5 for 30 min before repeat until the cell voltage drops below 3 V. After this initial period, the cells were alternatively cycled for two cycles at C/10 discharge and 50 cycles at 1C discharge. In each second C/10 cycle, the cell potential was relaxed for 5 min at 100, 50 and 25% SOC before applying a 30 s current pulse at 100 mA g.sup.−1 to calculate the cell resistance by the DCIR method, 2.5C rate discharge pulse for 30 minutes.

TABLE-US-00001 TABLE 1 Capacities from Coin Half Cell testing 15.sup.th cycle 1.sup.st cycle 1.sup.st cycle 2.sup.nd cycle 11.sup.th cycle discharge/ charge/ discharge/ discharge/ discharge/ mAh g.sup.−1 mAh g.sup.−1 mAh g.sup.−1 mAh g.sup.−1 mAh g.sup.−1 0.1 C sample 0.1 C 0.1 C 0.1 C 1 C retention C-CAM.1 245.9 201.6 206.1 191.0 203.5 CAM.2 251.8 215.9 220.6 201.4 212.7 CAM.3 249.1 209.8 216.4 198.0 210.5