A method for preparing nickel-containing positive electrode active material

Abstract

The present invention belongs to the field of battery material preparation, and specifically relates to a method for preparing a nickel-containing positive electrode active material, wherein a composite material containing a nickel hydroxide precursor and a lithium source is placed in a stainless steel reaction vessel, heated to T1 under negative pressure, then introduced into a medium oxygen atmosphere and kept warm for transformation treatment, and then subjected to a demagnetization treatment to obtain a composite modified material; the volume of oxygen in the medium oxygen atmosphere is 70-80v%, the temperature of T1 is 500-585°C; the composite modified material is sintered under an oxygen-rich atmosphere at a temperature of T2 to obtain the nickel-containing positive electrode active material, wherein the volume of the oxygen-rich atmosphere is greater than or equal to 90v%, and the temperature of T2 is 700-900°C. The preparation method of the present invention can obtain excellent electrochemical performance, and can also significantly reduce production costs.

Description

Technical Field

[0001] The invention belongs to the field of battery materials, and in particular relates to the field of preparation of positive electrode active materials. Background Art

[0002] The production process of lithium-ion battery positive electrode materials is a relatively complex process. In addition to the redox reaction, it also involves the process of solid solution. In the production of low-nickel ternary materials, due to the relatively low nickel content, the material activity is relatively small under high temperature conditions, and the requirements for reaction conditions are not so harsh. The entire production process is well controlled and the consistency of the products produced is relatively good. However, the high-nickel ternary positive electrode has a relatively high nickel content and reacts under the action of oxygen, which is more demanding for the entire reaction conditions, and is prone to side reactions or lithium atoms occupying the site, resulting in deterioration of electrical performance.

[0003] During the melting reaction, high-nickel ternary is sensitive to oxygen content and temperature. Slight fluctuations will lead to performance differences in the product, resulting in poor consistency. The production capacity of high-nickel ternary is relatively low, and the amount of each sagger is relatively small. If the amount of sagger is too much, it will lead to excessive dehydrated water vapor, affecting the oxygen content of the atmosphere. Moreover, the dehydrated water vapor, under the action of high temperature and alkali, will corrode the furnace wall and exhaust pipe, resulting in a reduction in the service life of the expensive atmosphere furnace body, and the corrosion of the pipe will lead to the introduction of magnetic foreign matter, resulting in excessive magnetic anomalies. Summary of the invention

[0004] In view of the problems of low efficiency, high cost, poor electrochemical performance and performance consistency in the preparation of existing positive electrode active materials, the purpose of the present invention is to provide a method for preparing nickel-containing positive electrode active materials, aiming to provide a method for preparing active materials with low magnetic anomaly, high performance and high quality stability based on low-cost stainless steel equipment.

[0005] Both the hydroxide precursor and the lithium source contain rich bases. Before preparation, the bases need to be pre-treated. However, the existing idea is mainly to treat the precursor and the lithium source separately, and the production efficiency of this type of process needs to be improved. There are still few technical solutions in the prior art that mix the hydroxide precursor and the lithium source and then perform a one-pot synchronous treatment. The main difficulty is that there are differences in the thermal behavior of the two, and it is difficult to achieve the simultaneous removal of the bases of the two in one pot. In addition, the hydroxide precursor and the lithium source are prone to equipment corrosion during the base treatment process, and when the two are jointly treated, there will be a superposition effect on the equipment corrosion, which will greatly cause the active material magnetic anomaly to exceed the standard (mainly low magnetic and non-magnetic iron-based components), affecting its electrochemical properties and affecting its quality stability. For the problem of weak magnetic anomaly, it is mainly compounded in the active material by embedding and encapsulation, and it is difficult to transform into a strong magnetic component. In addition, during the transformation process, it is also easy to cause the structure and properties of the active material to deteriorate, affecting the performance of the active material. Therefore, in view of the influence of magnetic anomalies, the existing technology mainly uses ceramic reaction equipment to react, aiming to reduce the introduction of magnetic anomalies, but the equipment cost and maintenance cost of this method are high, and it is difficult to apply in large-scale production. There is no good magnetic anomaly conversion treatment method in the existing technology. To this end, in view of the problems that the hydroxide precursor and lithium source in the existing technology are difficult to treat the base in one pot, and the one-pot base treatment stage is prone to high corrosion, non-magnetic and weakly magnetic magnetic anomaly impurities, and unsatisfactory electrochemical performance, the present invention provides the following solutions:

[0006] A method for preparing a nickel-containing positive electrode active material, comprising the steps of:

[0007] Step (1):

[0008] The composite material containing the nickel hydroxide precursor and the lithium source is placed in a stainless steel reaction container, the temperature is raised to T1 under negative pressure, a neutral oxygen atmosphere is introduced and the temperature is kept for transformation treatment, and then a demagnetization treatment is performed to obtain a composite modified material;

[0009] The volume of oxygen in the neutral oxygen atmosphere is 70-80v%, and the temperature of T1 is 500-585°C;

[0010] Step (2):

[0011] The composite modified material is sintered in an oxygen-rich atmosphere at a temperature of T2 to obtain the nickel-containing positive electrode active material, wherein the volume of the oxygen-rich atmosphere is greater than or equal to 90v%, and the temperature of T2 is 700-900°C.

[0012] The present invention provides a one-pot alkali treatment idea for a nickel hydroxide precursor and a lithium source in a stainless steel reaction device. The invention solves the technical problems that are easily faced by the one-pot transformation treatment of stainless steel equipment, such as the mismatch of thermal behaviors of components, unsatisfactory alkali transformation effect, excessive non-magnetic and low-magnetic magnetic anomaly impurities due to strong corrosion during the transformation process, unsatisfactory electrochemical properties, unstable preparation quality, etc. The one-pot transformation treatment can be realized in stainless steel equipment, which can significantly reduce the production cost and equipment maintenance cost. In addition, low-magnetic anomaly and high-performance active materials can be obtained, and the quality consistency of materials can be improved.

[0013] The technical solution of the present invention can theoretically be used for the preparation of hydroxide-type precursors with different nickel contents. Preferably, the nickel-containing hydroxide precursor is a nickel-rich hydroxide precursor, in which the molar ratio of Ni to the total metal is greater than or equal to 50 mol%;

[0014] Preferably, the chemical formula of the nickel-containing hydroxide precursor is: Ni x Co y Mn1 -x-y (OH)2; wherein x is 0.5 to 1; and y is 0 to 0.5 (preferably 0.01 to 0.3).

[0015] Preferably, the lithium source is at least one of LiOH and lithium carbonate;

[0016] Preferably, in the composite, the molar ratio of the metal in the nickel hydroxide precursor to the lithium in the lithium source is 1:1 to 1.2.

[0017] Preferably, the stainless steel reaction vessel is an austenitic stainless steel reaction vessel; preferably a stainless steel rotary kiln. The present invention can use stainless steel reaction equipment for reaction, and based on the control of process and parameters, it can solve the non-magnetic and weakly magnetic magnetic impurities caused by stainless steel equipment, which helps to significantly reduce the equipment preparation cost, avoid the product purification cost, and obtain high-performance active materials.

[0018] In the present invention, the pre-negative pressure treatment, the T1 transformation under a medium oxygen atmosphere and the combined control of its oxygen partial pressure and temperature, and the combined control of the T2 sintering process and temperature under an oxygen-rich atmosphere are the key to synergistically improving the one-pot alkali treatment effect, reducing magnetic anomalies, and improving the electrochemical properties of the prepared materials.

[0019] In the present invention, negative pressure temperature raising treatment is performed in advance, and the negative pressure is less than or equal to 0.5 atm, preferably less than or equal to 0.1 atm. The atm refers to standard atmospheric pressure.

[0020] Preferably, the heating rate to T1 is 1-20° C. / min.

[0021] In the present invention, after the negative pressure treatment, the transformation treatment is innovatively carried out under the medium oxygen partial pressure T1. Based on the joint control of the oxygen partial pressure and the T1 temperature, synergy can be achieved, which can synergistically improve the one-pot base transformation effect. In addition, the non-magnetic or magnetic anisotropic components can be unexpectedly transformed with high selectivity, and the degradation of the electrode material can be avoided.

[0022] In the present invention, the neutral oxygen atmosphere is a mixed gas of oxygen and protective gas, and the protective gas is at least one of nitrogen and inert gas;

[0023] Preferably, the transformation treatment time is 10-15 hours.

[0024] In the present invention, thanks to the T1 transformation treatment under negative pressure and medium oxygen atmosphere, the low-magnetic and non-magnetic components can be transformed into strong magnetic components with high selectivity, so that the composite modified material can be obtained based on conventional demagnetization treatment.

[0025] In the present invention, the composite modified material can be directly subjected to the calcination treatment of step (2). In addition, in a preferred embodiment of the present invention, the composite modified material and an additive are mixed and then sintered, and the additive is at least one of tungsten oxide, aluminum oxide, zirconium oxide, boron oxide, and strontium oxide.

[0026] There are no special requirements for the equipment in the roasting stage, for example, it can be a tubular furnace, a ceramic rotary kiln, a stainless steel rotary kiln, a rail kiln or a push plate kiln.

[0027] Preferably, the oxygen-rich atmosphere is pure oxygen, or a mixture of oxygen and protective gas, and the protective gas is at least one of nitrogen and an inert gas.

[0028] Preferably, the sintering time is 10-15 hours.

[0029] Beneficial Effects

[0030] The present invention provides a one-pot alkali treatment idea for a nickel hydroxide precursor and a lithium source in a stainless steel reaction device. The invention solves the technical problems that are easily faced by the one-pot transformation treatment of stainless steel equipment, such as the mismatch of thermal behaviors of components, unsatisfactory alkali transformation effect, excessive non-magnetic and low-magnetic magnetic anomaly impurities due to strong corrosion during the transformation process, unsatisfactory electrochemical properties, unstable preparation quality, etc. The one-pot transformation treatment can be realized in stainless steel equipment, which can significantly reduce the production cost and equipment maintenance cost. In addition, low-magnetic anomaly and high-performance active materials can be obtained, and the quality consistency of materials can be improved.

[0031] The process of the present invention can increase the production capacity by more than 2 times, extend the service life of the kiln by 50%, reduce the production cost by more than 20%, and significantly improve the electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Figure 1 shows the first cycle capacity test results of the active materials prepared for each case;

[0033] Figure 2 Figure 1 shows the results of the first efficacy tests of the active materials prepared for each case; DETAILED DESCRIPTION

[0034] Example 1

[0035] Step (1):

[0036] Lithium hydroxide and Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor (the molar ratio of Li / (Ni-Co-Mn) is 1.1:1) is mixed and placed in a rotary kiln in a stainless steel (316L) chamber, and the temperature is increased (the heating rate is 10°C / min) to 500°C (marked as T1) under a negative pressure of 0.05atm (marked as P), and then 70v% oxygen-nitrogen composite gas (marked as Q1) is introduced, and the temperature is maintained at T1 for 3 hours for insulation transformation treatment, and then demagnetization treatment is carried out to obtain a composite modified material.

[0037] Step (2):

[0038] The composite modified material was sintered in a 95v% oxygen-nitrogen mixed gas (marked as Q2) at a temperature of 700°C (marked as T2) for 10 hours to obtain an active material.

[0039] Example 2

[0040] Compared with Example 1, the only difference is that the negative pressure is 0.2 atm, and other operations and parameters are the same as Example 1.

[0041] Example 3

[0042] Compared with Example 1, the only difference is that the oxygen volume content of Q1 is 80v%, the temperature of T1 is 580°C, and the other operations and parameters are the same as Example 1.

[0043] Example 4

[0044] Compared with Example 1, the only difference is that the oxygen volume content of Q2 is 90v%, the temperature of T2 is 880°C, and the other operations and parameters are the same as Example 1.

[0045] Example 5

[0046] Compared with Example 1, the only difference is that the precursor is Ni 0.6 Co 0.2 Mn 0.2 (OH)2 precursor, other operations and parameters are the same as in Example 1.

[0047] Comparative Example 1

[0048] Compared with Example 1, the only difference is that the pressure of P is 1 atm (that is, the stage of heating to T1 is not carried out under negative pressure), and other operations and parameters are the same as Example 1.

[0049] Comparative Example 2

[0050] Compared with Example 1, the only difference is that the oxygen volume content of Q1 is 50v%, and other operations and parameters are the same as Example 1.

[0051] Comparative Example 3

[0052] Compared with Example 1, the only difference is that the oxygen volume content of Q1 is 90v%, and other operations and parameters are the same as Example 1.

[0053] Comparative Example 4

[0054] Compared with Example 1, the only difference is that the temperature of T1 is 450° C., and other operations and parameters are the same as Example 1.

[0055] Comparative Example 5

[0056] Compared with Example 1, the only difference is that the temperature of T1 is 650° C., and other operations and parameters are the same as Example 1.

[0057] Comparative Example 6

[0058] Compared with Example 1, the only difference is that the oxygen volume content of Q2 is 80v%, and other operations and parameters are the same as Example 1.

[0059] Comparative Example 7

[0060] Compared with Example 1, the only difference is that the temperature of T2 is 650° C., and other operations and parameters are the same as Example 1.

[0061] The active materials prepared in Examples 1 to 6 and Comparative Examples 1 to 7 were subjected to electrochemical measurements, and the battery assembly and testing methods are shown in Table 1;

[0062] Table 1

[0063]

[0064] The test results of each case are shown in Table 2. Figure 1 and 2 ;

[0065]

[0066] The magnetic anomaly (in ppm) content of active materials in each case is shown in Table 3:

[0067] Table 3

[0068] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Magnetic anomaly 5 4 6 8 9 100 800 704 655 760

[0069] For each typical case (such as Example 1 and Comparative Examples 1 to 5), three batches were repeated, and the electrochemical performance was measured using the method of Example 1. The relative error of the results of each batch was calculated, and the quality stability of the process was measured based on the relative error.

[0070] The relative error is calculated as follows: (test results of each batch - average test results) / average test results * 100%;

[0071] The test results are shown in Table 4:

[0072] Case Maximum capacity relative error Maximum first effect relative error Maximum cycle relative error Example 1 2.2％ 1.6％ 2％ Comparative Example 1 7.9％ 5.6％ 6.3％ Comparative Example 2 5.5％ 4.9％ 5.1％ Comparative Example 3 4.8％ 3.8％ 3.9％ Comparative Example 4 5.2％ 4.7％ 4.2％ Comparative Example 5 5.2％ 5.1％ 4.7％

[0073] By adopting the method of the present invention, better quality stability can be obtained.

[0074] Example 6

[0075] Compared with Example 1, the only difference is that in step 2, the composite modified material (based on the total molar amount of Ni-Co-Mn) and WO3 are mixed in a molar ratio of 1:0.01, and then calcined under Q2 / T2. The other calcination parameters are the same as Example 1. The electrochemical properties are measured according to the method of Example 1, and the results are: the first capacity is 211mha / h, the first effect is 93.1%, and the 50-cycle retention rate is 99.3%.

Claims

1. A method for preparing a nickel-containing positive electrode active material, characterized in that the steps include: Step (1): The composite material containing the nickel hydroxide precursor and the lithium source is placed in a stainless steel reaction container, and the temperature is raised to T1 under negative pressure, and then a medium oxygen atmosphere is introduced and the temperature is kept to perform a transformation treatment, and then a demagnetization treatment is performed to obtain a composite modified material; the pressure of the negative pressure is less than or equal to 0.5atm; The volume of oxygen in the neutral oxygen atmosphere is 70-80v%, and the temperature of T1 is 500-585°C; Step (2): The composite modified material is sintered in an oxygen-rich atmosphere at a temperature of T2 to obtain the nickel-containing positive electrode active material, wherein the volume of oxygen in the oxygen-rich atmosphere is greater than or equal to 90v%, and the temperature of T2 is 700-900°C.

2. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The nickel-containing hydroxide precursor is a nickel-rich hydroxide precursor, in which the molar ratio of Ni to the total metal is greater than or equal to 50 mol%.

3. The method for preparing a nickel-containing positive electrode active material according to claim 2, characterized in that: The chemical formula of the nickel-containing hydroxide precursor is: Ni x Co y Mn1 -x-y (OH)2; wherein x is 0.5~1; and y is 0~0.

5.

4. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The lithium source is at least one of LiOH and lithium carbonate.

5. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: In the composite, the molar ratio of the metal in the nickel hydroxide precursor to the lithium in the lithium source is 1:1-1.

2.

6. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The stainless steel reaction container is an austenitic stainless steel reaction container.

7. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The stainless steel reaction container is a stainless steel rotary kiln.

8. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The negative pressure is less than or equal to 0.1 atm.

9. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The heating rate to T1 is 1~20℃ / min.

10. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The neutral oxygen atmosphere is a mixed gas of oxygen and protective gas, and the protective gas is at least one of nitrogen and inert gas.

11. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The transformation process takes 10 to 15 hours.

12. The method for preparing a nickel-containing positive electrode active material according to any one of claims 1 to 11, characterized in that: In step (2), the composite modified material and the additive are mixed and then sintered, and the additive is at least one of tungsten oxide, aluminum oxide, zirconium oxide, boron oxide, and strontium oxide.

13. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The firing stage is carried out in a tube furnace, ceramic rotary kiln, stainless steel rotary kiln, rail kiln or push plate kiln.

14. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The oxygen-rich atmosphere is pure oxygen or a mixture of oxygen and protective gas, and the protective gas is at least one of nitrogen and an inert gas.

15. The method for preparing a nickel-containing positive electrode active material according to claim 1, characterized in that: The sintering time is 10-15h.

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