Lithium-rich nickel-manganese-cobalt cathode powders for lithium-ion batteries

Abstract

The invention provides a dual component lithium-rich layered oxide positive electrode material for a secondary battery, the material consisting of a single-phase lithium metal oxide with space group R-3m and having the general formula Li.sub.1+.sub.bN.sub.1bO.sub.2, wherein 0.155b0.25 and N=Ni.sub.xMn.sub.yCO.sub.zZr.sub.cA.sub.d, with 0.10x0.40, 0.30y0.80, 0<z0.20, 0.005c0.03, and 0d0.10, and wherein x+y+z+c+d=1, with A being a dopant comprising at least one element, and the material further consisting of a Li.sub.2ZrO.sub.3 component.

Claims

1. A dual component lithium-rich layered oxide positive electrode material for a secondary battery, the material comprising a single-phase lithium metal oxide component and a Li.sub.2ZrO.sub.3 component, wherein the single-phase lithium metal oxide component has a general formula Li.sub.1+bN.sub.1bO.sub.2, wherein 0.155b0.25 and N=Ni.sub.xMn.sub.yCo.sub.zZr.sub.cA.sub.d, wherein 0.10x0.40, 0.30y0.80, 0<z0.20, 0.005c0.03, 0d0.10, wherein x+y+z+c+d=1, with A being a dopant comprising at least one element, and wherein the Li.sub.2ZrO.sub.3 component is distributed in the layered oxide material.

2. The dual component lithium-rich layered oxide positive electrode material of claim 1, wherein 0.205<b0.25.

3. The dual component lithium-rich layered oxide positive electrode material of claim 2, wherein the Li.sub.2ZrO.sub.3 component is homogeneously distributed in the layered oxide material.

4. The dual component lithium-rich layered oxide positive electrode material of claim 1, wherein 0.15x0.30, 0.50y0.75, 0.05<z0.15, 0.01c0.03, and 0d0.10.

5. The dual component lithium metal oxide powder of claim 1, wherein the dopant A comprises one or more elements selected from the group consisting of Al, Mg, Ti, Cr, V, W, Nb and Ru.

6. The dual component lithium metal oxide powder of claim 1, wherein 0.15x0.25, 0.55y0.70, and 0.05z0.15.

7. The dual component lithium metal oxide powder of claim 1, wherein x=0.220.02, y=0.670.05, z=0.110.05 and 0.18b0.21.

8. A method for preparing the dual component lithium-rich layered oxide positive electrode material according to claim 1, comprising: providing a precursor comprising Ni, Mn and Co, providing a precursor comprising Zr that is insoluble in water, providing a precursor comprising dopant A, providing a precursor comprising Li, preparing a dry mixture comprising the precursors of Ni, Mn and Co; lithium, Zr and A, wherein the amounts of the different elements are stoichiometrically controlled to reach a general formula Li.sub.1+bN.sub.1bO.sub.2, with 0.155b0.25 and N=Ni.sub.xMn.sub.yCo.sub.zZr.sub.cA.sub.d, with 0.10x0.40, 0.30y0.80, 0<z0.20, 0.005c0.03, and 0d0.10, and wherein x+y+z+c+d=1, heating the mixture to a sintering temperature of at least 700 C., sintering the mixture at the sintering temperature for a period of time, and cooling the sintered mixture.

9. The method according to claim 8, wherein 0.205<b0.25.

10. The method according to claim 8, wherein the step of providing a precursor comprising Ni, Mn and Co comprises: providing separate sources of Ni, Mn and Co, the sources being one of nitrates, sulfates or oxalates, mixing stoichiometrically controlled quantities of the separate sources in a water-based liquid to reach a general formula Ni.sub.xMn.sub.yCo.sub.z, adding a precipitation agent that is either a hydroxide or a carbonate, whereby the precursor, being a NiMnCo oxy-hydroxide or a NiMnCo carbonate is precipitated.

11. The method according to claim 8, wherein the Zr precursor is ZrO.sub.2.

12. The method according to claim 8, wherein the Zr precursor is a sub-micron sized ZrO.sub.2 powder having a D50<500 nm and a BET40 m.sup.2/g.

13. The method according to claim 8, wherein the precursor of the dopant A is one or more compounds selected from the group consisting of Al.sub.2O.sub.3, TiO.sub.2, MgO, WO.sub.3, Cr.sub.2O.sub.3, V.sub.2O.sub.5, Nb.sub.2O.sub.5 and RuO.sub.2.

Description

(1) In order to explain the invention in more detail, the following examples and counter example are provided, which refer to the following figures:

(2) FIG. 1: Relationship of Li/M versus Unit cell Volume measured from X-ray diffraction (XRD);

(3) FIG. 2: Cross-sectional SEM image;

(4) FIG. 3: EDS mapping of Zr in Example 4.

(5) In order to evaluate the materials prepared according to the invention, they are submitted to the following Coin cell test: a half cell (coin cell) is assembled by placing a separator (from Celgard) between the positive electrode and a piece of lithium metal as negative electrode, and dropping an electrolyte1M LiPF.sub.6 in EC/DMC (1:2)between separator and electrodes. All the cell tests in the Examples below follow the procedure shown in Table 1. The C-rate is defined as 160 mAh/g. For example, 0.1C means that the cell will be charged or discharged in 10 hours. E-Curr and V stand for the end current and cut-off voltage, respectively. At the first cycle, the DQ0.05C (discharge capacity of the first cycle at a rate of 0.05C) and IRRQ (irreversible capacity) are determined. The rate performance can be calculated from the subsequent six cycles. The performance of cycle stability is obtained from cycle #8 to #32. The capacity fading at 0.1C is represented by Q.sub.fade0.1C (%/100). With DQ8 and DQ31 referring to the discharge capacity of cycle #8 and #31 respectively, the Q.sub.fade0.1C (%/100) could be obtained through the following formula: (1(DQ31/DQ8))/22*100*100. The performance of the discharge voltage stability is obtained from cycle #8 to #32. The voltage fading at 0.1C is represented by V.sub.fade0.1C (V/100). With DV8 and DV31 referring to the average discharge voltage of cycle #8 and #31 respectively, the V.sub.fade0.1C (V/100 cycle) could be obtained through the following formula: (DV8/DV31))/22*100.

(6) TABLE-US-00001 TABLE 1 coin cell testing procedure Charge Discharge Cycle # C-rate E-Curr V C-rate E-Curr V 1 0.05 4.6 0.05 2.0 2 0.25 0.05 C 4.6 0.10 2.0 3 0.25 0.05 C 4.6 0.20 2.0 4 0.25 0.05 C 4.6 0.50 2.0 5 0.25 0.05 C 4.6 1.00 2.0 6 0.25 0.05 C 4.6 2.00 2.0 7 0.25 0.05 C 4.6 3.00 2.0 8 0.25 0.05 C 4.6 0.10 2.0 9 0.25 0.05 C 4.6 1.00 2.0 10-30 0.25 0.05 C 4.6 0.50 2.0 31 0.25 0.05 C 4.6 0.10 2.0 32 0.25 0.05 C 4.6 1.0 2.0

(7) The materials according to this invention were measured in a commercial X-ray diffractometer to obtain crystal structural information. A Rigaku D/MAX 2200 PC diffractometer equipped with a Cu (K-Alpha) target X-ray tube and a diffracted beam monochromator at room temperature in the 15 to 70 2-Theta () degree range was applied. The lattice parameters (a and c axis of the unit cell) of the different phases were calculated from the X-ray diffraction patterns using full pattern matching and Rietveld refinement methods. The volume of the unit cell of the examples was calculated by using the following equation:

(8) $V_{\mathrm{unit}\mathrm{cell}}=a^2*c*\frac{\sqrt[2]{3}}{6}$

(9) The invention will now be illustrated in the following Examples:

Example 1

(10) A powder according to the invention is manufactured by the following steps:

(11) (a) Blending of lithium, Nickel-Manganese-Cobalt precursor and Zr precursor: lithium carbonate, a mixed NiMnCo carbonate and ZrO.sub.2 are homogenously blended a vertical single-shaft mixer by a dry powder mixing process. The blend ratio is targeted to obtain Li.sub.1.197 (Ni.sub.0.218Mn.sub.0.663Co.sub.0.109Zr.sub.0.01).sub.0.803O.sub.2, which can be easily verified by an analysis technique such as ICP.

(12) (b) Synthesizing in an oxidizing atmosphere: the powder mixture from step (a) is sintered in a box furnace in an oxidizing atmosphere. The sintering temperature is 800 C. and the dwell time is 10 hrs. Dry air is used as an oxidizing gas.

(13) (c) Milling: after sintering, the sample is milled in a grinding machine to a particle size distribution with D50=10-12 m.

Example 2

(14) A powder according to the invention is manufactured by the following steps:

(15) (a) Blending of lithium, Nickel-Manganese-Cobalt precursor and Zr precursor: lithium carbonate, a mixed NiMnCo carbonate and ZrO.sub.2 are homogenously blended a vertical single-shaft mixer by a dry powder mixing process. The blend ratio is targeted to obtain Li.sub.1.201 (Ni.sub.0.218Mn.sub.0.663Co.sub.0.109ZrO.sub.0.01).sub.0.799O.sub.2, which can be easily verified by an analysis technique such as ICP.

(16) (b) Synthesizing in an oxidizing atmosphere: The powder mixture from step (a) is sintered in a box furnace in an oxidizing atmosphere. The sintering temperature is 800 C. and the dwell time is 10 hrs. Dry air is used as an oxidizing gas.

(17) (c) Milling: after sintering, the sample is milled in a grinding machine to a particle size distribution with D50=10-12 m.

Example 3

(18) A powder according to the invention is manufactured by the following steps:

(19) (a) Blending of lithium, Nickel-Manganese-Cobalt precursor and Zr precursor: lithium carbonate, a mixed NiMnCo carbonate and ZrO.sub.2 are homogenously blended a vertical single-shaft mixer by a dry powder mixing process. The blend ratio is targeted to obtain Li.sub.1.203 (Ni.sub.0.218Mn.sub.0.663Co.sub.0.109Zr.sub.0.01).sub.0.797O.sub.2, which can be easily verified by an analysis technique such as ICP.

(20) (b) Synthesizing in an oxidizing atmosphere: The powder mixture from step (a) is sintered in a box furnace in an oxidizing atmosphere. The sintering temperature is 850 C. and the dwell time is 10 hrs. Dry air is used as an oxidizing gas.

(21) (c) Milling: after sintering, the sample is milled in a grinding machine to a particle size distribution with D50=10-12 m.

Example 4

(22) A powder according to the invention is manufactured in by the following steps:

(23) (a) Blending of lithium, Nickel-Manganese-Cobalt precursor and Zr precursor: lithium carbonate, a mixed NiMnCo carbonate and ZrO.sub.2 are homogenously blended a vertical single-shaft mixer by a dry powder mixing process. The blend ratio is targeted to obtain Li.sub.1.210 (Ni.sub.0.218Mn.sub.0.663Co.sub.0.109Zr.sub.0.01).sub.0.790O.sub.2, which can be easily verified by an analysis technique such as ICP.

(24) (b) Synthesizing in an oxidizing atmosphere: The powder mixture from step (a) is sintered in a box furnace in an oxidizing atmosphere. The sintering temperature is 850 C. and the dwell time is 10 hrs. Dry air is used as an oxidizing gas.

(25) (c) Milling: after sintering, the sample is milled in a grinding machine to a particle size distribution with D50=10-12 m.

Counter Example 1

(26) A powder according to the invention is manufactured by the following steps:

(27) (a) Blending of lithium and Nickel-Manganese-Cobalt precursor: lithium carbonate and a mixed NiMnCo carbonate are homogenously blended a vertical single-shaft mixer by a dry powder mixing process. The blend ratio is targeted to obtain Li.sub.1.197(Ni.sub.0.22Mn.sub.0.67Co.sub.0.11).sub.0.803O.sub.2, which can be easily verified by an analysis technique such as ICP.

(28) (b) Synthesizing in an oxidizing atmosphere: The powder mixture from step (a) is sintered in a box furnace in an oxidizing atmosphere. The sintering temperature is 800 C. and the dwell time is 10 hrs. Dry air is used as an oxidizing gas.

(29) (c) Milling: after sintering, the sample is milled in a grinding machine to a particle size distribution with D50=10-12 m.

Counter Example 2

(30) A powder according to the invention is manufactured by the following steps:

(31) (a) Blending of lithium and Nickel-Manganese-Cobalt precursor: lithium carbonate and a mixed NiMnCo carbonate are homogenously blended a vertical single-shaft mixer by a dry powder mixing process. The blend ratio is targeted to obtain Li.sub.1.201(Ni.sub.0.22Mn.sub.0.67Co.sub.0.11).sub.0.799O.sub.2, which can be easily verified by an analysis technique such as ICP.

(32) (b) Synthesizing in an oxidizing atmosphere: The powder mixture from step (a) is sintered in a box furnace in an oxidizing atmosphere. The sintering temperature is 800 C. and the dwell time is 10 hrs. Dry air is used as an oxidizing gas.

(33) (c) Milling: after sintering, the sample is milled in a grinding machine to a particle size distribution with D50=10-12 m.

Counter Example 3

(34) A powder according to the invention is manufactured by the following steps:

(35) (a) Blending of lithium and Nickel-Manganese-Cobalt precursor: lithium carbonate and a mixed NiMnCo carbonate are homogenously blended a vertical single-shaft mixer by a dry powder mixing process. The blend ratio is targeted to obtain Li.sub.1.203(Ni.sub.0.22Mn.sub.0.67Co.sub.0.11).sub.0.797O.sub.2, which can be easily verified by an analysis technique such as ICP.

(36) (b) Synthesizing in an oxidizing atmosphere: The powder mixture from step (a) is sintered in a box furnace in an oxidizing atmosphere. The sintering temperature is 850 C. and the dwell time is 10 hrs. Dry air is used as an oxidizing gas.

(37) (c) Milling: after sintering, the sample is milled in a grinding machine to a particle size distribution with D50=10-12 m.

Counter Example 4

(38) A powder according to the invention is manufactured by the following steps:

(39) (a) Blending of lithium and Nickel-Manganese-Cobalt precursor: lithium carbonate and a mixed NiMnCo carbonate are homogenously blended a vertical single-shaft mixer by a dry powder mixing process. The blend ratio is targeted to obtain Li.sub.1.20(Ni.sub.0.22Mn.sub.0.67Co.sub.0.11).sub.0.790O.sub.2, which can be easily verified by an analysis technique such as ICP.

(40) (b) Synthesizing in an oxidizing atmosphere: The powder mixture from step (a) is sintered in a box furnace in an oxidizing atmosphere. The sintering temperature is 850 C. and the dwell time is 10 hrs. Dry air is used as an oxidizing gas.

(41) (c) Milling: after sintering, the sample is milled in a grinding machine to a particle size distribution with D50=10-12 m.

(42) Discussion:

(43) FIG. 1 shows the volume of the unit cell of the crystal structure of the different Examples and Counter Examples. Li/M is the target value calculated from the molecular formula of each example and counter example. The volume of the Examples and Counter Examples does not differ much, and follows the same trend versus the Li/M. Considering the similar ionic radii of Zr.sup.4+ and Ni.sup.2+ or Co.sup.3+, Zr.sup.4+ doping will not results in dramatic change of lattice constant and volume of the unit cell. This indicates that the Zr or most of it is doped into the crystal structure. The XRD pattern of the powder of Example 4 indicates the presence of the secondary phase Li.sub.2ZrO.sub.3. FIG. 2 shows the cross-sectional SEM images of Example 4 and FIG. 3 shows the EDS mapping of the element Zr. It shows that Zr element distributes homogenously in the NMC particle. It indicated that Li.sub.2ZrO.sub.3 also homogenously distributes in the bulk of obtained Li-rich NMC particles. Table 2 summarizes the coin cell performance of the Examples and Counter Examples. Example 1 shows an improved cycle stability versus Counter Example 1, with a comparable voltage stability. Example 2 shows a significant improvement in both cycle stability and voltage stability. Similar results are obtained when comparing Example 3 vs. Counter Example 3 and Example 4 vs. Counter Example 4. It is clear that the doped Zr improves the electrochemical performance of lithium-rich NMC, especially for the issue of voltage fading. Example 4 has the best voltage stability of all examples. It indicates that the presence of a secondary phase Li.sub.2ZrO.sub.3 homogenously distributed in the layered oxide could further improve the voltage stability. This may be due to the fact that Li.sub.2ZrO.sub.3 in the bulk could help to suppress the phase transition of layered structure to spinel structure. Meanwhile, Zr doping keeps the high energy density of this type of cathode materials.

(44) TABLE-US-00002 TABLE 2 Comparison of cycle stability at different cycle conditions 1.sup.st DC Capacity Q.sub.fade0.1 C V.sub.fade0.1 C (mAh/g) (%) (V/100 cycle) Example 1 280.87 16.12 0.305 Counterexample 1 287.99 19.26 0.298 Example 2 278.59 19.03 0.259 Counterexample 2 291.25 23.02 0.305 Example 3 278.16 12.47 0.222 Counterexample 3 281.70 15.02 0.293 Example 4 267.16 6.22 0.218 Counterexample 4 271.13 20.18 0.269