Ternary positive electrode material and preparation method thereof

Abstract

The invention discloses a ternary positive electrode material and a preparation method thereof, and relates to the field of battery positive electrode materials and preparation methods thereof.The ternary positive electrode material is prepared from a nickel-cobalt-manganese hydroxide precursor, lithium salt and an oxygen-enriched oxygen storage material, and the oxygen-enriched oxygen storage material is used for generating oxygen in the preparation process, converting bivalent nickel into trivalent nickel, and storing the trivalent nickel in the lithium salt. And the content of divalent nickel is reduced. According to the invention, the oxygen-rich oxygen storage material is adopted as an additive to sinter the ternary positive electrode material so as to dope and / or coat the ternary positive electrode material, and because oxygen is generated in the sintering preparation process of the oxygen-rich oxygen storage material, divalent nickel in the ternary positive electrode material can be better oxidized into trivalent nickel; the content of divalent nickel in the ternary positive electrode material is reduced, so that the lithium-nickel mixed arrangement degree in the ternary positive electrode material is reduced, migration of lithium ions in the charging and discharging process is facilitated, and the specific capacity and rate capability of the ternary positive electrode material are improved.

Description

Technical Field

[0001] The present invention relates to the field of battery positive electrode materials and preparation methods thereof, and in particular to a ternary positive electrode material and a preparation method thereof. Background Art

[0002] The ternary layered cathode material is prone to cation mixing during the material synthesis stage and electrochemical cycle process, that is, the transition metal ions at the 3a position in the layered structure partially occupy the lithium ions at the 3b position. The Ni ion radius is , the radius of Li ions is , the two ions have similar radii and easily occupy each other's sites, resulting in Li / Ni mixing. During the sintering process of high-nickel ternary layered materials, the divalent Ni in the material is difficult to be completely oxidized to trivalent Ni. Part of the divalent Ni in the material may migrate from the transition metal layer in the layered structure to the Li layer to form Li / Ni mixing. Therefore, a higher oxygen concentration and an appropriate excess of lithium are required during the sintering process of high-nickel ternary layered materials to reduce the degree of Li / Ni mixing. During the electrochemical cycle, Li ions escape from the material layers, resulting in a large number of vacancies. Some divalent Ni at the 3a position will spontaneously migrate to the Li layer to occupy the position of Li ions. Excessive divalent Ni occupying the Li ion layer will aggravate the transformation of the layered structure to the spinel structure or even the rock salt phase structure, causing serious capacity attenuation. It will inhibit lithium diffusion and increase the reaction impedance, resulting in irreversible capacity loss. Severe lithium-nickel mixing will affect the deintercalation and electrochemical performance of lithium ions. This structural defect will increase the internal resistance of the material and reduce the electrochemical activity. Severe Li + / Ni 2+ Ion mixing will reduce the distance between lithium ion layers and increase the impedance of the material. 2+ Entering the lithium ion layer will hinder Li + Migration path, limiting Li + On the other hand, the strong Ni-O bonds in the lithium layer weaken the electrostatic repulsion between the tightly packed metal oxides, thus limiting the movement space during the lithium ion insertion and extraction process. + / Ni 2+ The existence of ion disorder problem seriously restricts the rate performance and initial discharge capacity of high-nickel ternary layered cathode materials.

[0003] In view of this, this application is filed. Summary of the invention

[0004] The purpose of the present invention is to provide a ternary positive electrode material and a preparation method thereof, by adding an oxygen-rich oxygen storage material to the raw material to achieve modification of the ternary positive electrode material and generate oxygen during the preparation and sintering process, thereby reducing the content of divalent nickel, so as to solve the problem in the prior art that Ni is difficult to be completely oxidized to trivalent Ni, and part of the divalent Ni present in the material may migrate from the transition metal layer in the layered structure to the Li layer to form a Li / Ni mixed arrangement, thereby reducing the electrochemical performance of the ternary positive electrode material.

[0005] The present invention is achieved through the following technical scheme: An embodiment of the present invention provides a ternary positive electrode material, including a material prepared from a nickel-cobalt-manganese hydroxide precursor, a lithium salt and an oxygen-rich oxygen storage material, wherein the oxygen-rich oxygen storage material is used to generate oxygen during the preparation process to convert divalent nickel into trivalent nickel to reduce the divalent nickel content.

[0006] Preferably, the oxygen-rich oxygen storage material includes one or a mixture of more of MnO2, CaO2, ZnO2, CeO2, SrO2, and MgO2.

[0007] Preferably, the content of the oxygen-rich oxygen storage material accounts for 0.2% to 1.5% of the total mass of the nickel-cobalt-manganese hydroxide precursor and the lithium salt.

[0008] Preferably, the oxygen-rich oxygen storage material includes MnO2, CaO2 and BaO2.

[0009] In order to better solve the above problems, an embodiment of the present invention further provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0010] S1: mixing a nickel-cobalt-manganese hydroxide precursor, a lithium salt and an oxygen-rich oxygen storage material to obtain a mixture;

[0011] S2: Sintering the mixture, cooling and sieving in sequence after sintering to obtain a ternary positive electrode material.

[0012] Preferably, the temperature at which the oxygen-rich oxygen storage material decomposes to generate oxygen is lower than the sintering temperature in S2.

[0013] Preferably, the sintering process in S2 includes first heating the temperature to 500-600°C at a rate of 1-5°C / min, keeping the temperature for 1-5 hours, and then heating the temperature to 700-950°C at a rate of 1-3°C / min for sintering, and the sintering time is 8-20 hours.

[0014] Preferably, the oxygen-rich oxygen storage material is a mixture of oxides having different decomposition temperatures to generate oxygen.

[0015] Preferably, the oxygen-rich oxygen storage material can modify the ternary positive electrode material.

[0016] Preferably, the mass ratio of the nickel-cobalt-manganese hydroxide precursor to the lithium salt is 1:0.45-0.55.

[0017] Compared with the prior art, the embodiments of the present invention have the following advantages and beneficial effects:

[0018] 1. The embodiment of the present invention uses an oxygen-rich oxygen storage material as an additive to sinter the ternary positive electrode material so as to dope and / or coat the ternary positive electrode material. Since the oxygen-rich oxygen storage material generates oxygen during the sintering preparation process, the divalent nickel in the ternary positive electrode material can be better oxidized to trivalent nickel, reducing the divalent nickel content in the ternary positive electrode material, thereby reducing the degree of lithium-nickel mixing in the ternary positive electrode material, which is more conducive to the migration of lithium ions during the charge and discharge process, thereby improving the specific capacity and rate performance of the ternary positive electrode material. At the same time, adding an appropriate amount of oxygen storage material can also be used as a doping material or / and coating material for the ternary positive electrode material to modify the ternary positive electrode material and improve the performance of the ternary positive electrode material. The oxygen-rich oxygen storage material is evenly mixed in the sample, and the generated oxygen can come into contact with the internal sample, and the prepared samples have less differences.

[0019] 2. In the embodiment of the present invention, since oxygen is generated during the preparation process of the oxygen storage material, the divalent nickel content in the ternary positive electrode material can be better reduced, the degree of lithium-nickel mixing in the ternary positive electrode material can be reduced, and it is more conducive to the migration of lithium ions during the charge and discharge process, thereby improving the specific capacity and rate performance of the ternary positive electrode material. At the same time, adding an appropriate amount of oxygen storage material can also be used as a doping material or / and coating material of the ternary positive electrode material to modify the ternary positive electrode material and improve the performance of the ternary positive electrode material.

[0020] 3. The embodiment of the present invention selects an oxygen-rich oxygen storage material whose decomposition temperature to generate oxygen is lower than the sintering temperature to facilitate the decomposition of the oxygen-rich oxygen storage material to generate oxygen. At the same time, an oxygen-rich oxygen storage material whose decomposition temperature to generate oxygen is close to or ahead of the temperature of the sintering reaction of the ternary positive electrode material is selected, so that the generated oxygen can be used to participate in the reaction of the ternary positive electrode material.

[0021] 4. The embodiment of the present invention selects a variety of oxygen-rich oxygen storage materials with different decomposition temperatures for mixed use to avoid excessive concentration of oxygen production, which results in the oxygen being discharged before it has a chance to contact the ternary positive electrode material. Selecting a variety of oxygen-rich oxygen storage materials with different decomposition temperatures can continuously generate oxygen during the heating process, allowing the ternary positive electrode material to always be kept in an oxygen atmosphere, making it easier for oxygen to enter the interior of the ternary positive electrode, and the internal divalent nickel is more easily oxidized to trivalent nickel. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0023] Figure 1 This is a SEM scan of the ternary positive electrode material prepared in Example 1 of the present invention;

[0024] Figure 2 XRD comparison diagram of the ternary positive electrode materials prepared in Examples 1-6 of the present invention and Comparative Example 1; DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0026] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The present invention provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0028] Add nickel-cobalt-manganese hydroxide precursor, lithium salt and oxygen-enriched oxygen storage material into a high-speed mixer barrel at one time according to the calculated weight ratio. After mixing evenly using a high-speed mixer, put the mixture into a clean sagger, use a tubular furnace, heat the temperature to 500-600°C at a heating rate of 1-5°C / min for 1-5h, then heat the temperature to 700-950°C at a heating rate of 1-3°C / min for 8-20h, cool naturally to room temperature after sintering, take out the sample and sieve it through a 400-mesh sieve to obtain a ternary positive electrode material; the oxygen-enriched oxygen storage material includes any combination of one or more of MnO2, CaO2, ZnO2, CeO2, SrO2, MgO2, etc., and the oxygen-enriched oxygen storage material includes but is not limited to the above materials.

[0029] The decomposition temperatures of common oxygen storage materials are as follows: MnO2 decomposition temperature is 500-600℃, CaO2 decomposes at 400℃ with reaction 2CaO2=2CaO+O2↑, ZnO2 decomposes at 150℃ to release oxygen, BaO2 loses part of its oxygen at around 790℃ and turns into BaO, and MgO2 decomposes into oxygen and magnesium oxide at 300℃.

[0030] The total amount of oxygen-rich oxygen storage material added should be between 0.2% and 1.5%. If the amount added is too little, less oxygen is produced, and less divalent nickel is oxidized, which has little effect on improving the performance of the ternary positive electrode. If the amount added is too much, there will be too much inactive substance in the sample, resulting in a decrease in the performance of the ternary positive electrode material.

[0031] The temperature range in which the oxygen-rich oxygen storage material decomposes to produce oxygen should be lower than the final sintering temperature to facilitate the decomposition of the oxygen-rich oxygen storage material to produce oxygen.

[0032] At the same time, the decomposition temperature of the oxygen-rich oxygen storage material is preferably close to or slightly earlier than the temperature range in which the ternary positive electrode material reaction requires the participation of oxygen, so that the generated oxygen can be used to participate in the ternary positive electrode material reaction.

[0033] A variety of oxygen-rich storage materials with different decomposition temperatures should be selected to avoid excessive concentration of oxygen, which will result in the oxygen being discharged before it has a chance to come into contact with the ternary positive electrode material. Selecting a variety of oxygen-rich storage materials with different decomposition temperatures can allow oxygen to be continuously produced during the heating process, allowing the ternary positive electrode material to always remain in an oxygen atmosphere, making it easier for oxygen to enter the interior of the ternary positive electrode, and the internal divalent nickel is more easily oxidized to trivalent nickel.

[0034] Example 1

[0035] The present invention provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0036] 200g of nickel-cobalt-manganese hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2, 92g of lithium hydroxide monohydrate, and 0.5% of the total mass of MnO2 of nickel-cobalt-manganese hydroxide precursor and lithium salt were fully mixed in a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, heated to 500°C at 3°C / min in a tube furnace, kept warm for 2h, and then heated to 800°C at 1.5°C / min for sintering for 12h. After sintering, naturally cooled to room temperature, took out the sample, sieved with a 400-mesh sieve, and obtained a ternary positive electrode material. Sample SEM as shown Figure 1 As shown, the primary particles were fully developed and the sample preparation was good.

[0037] Example 2

[0038] The present invention provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0039] 200g of nickel-cobalt-manganese hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2, 92g lithium hydroxide monohydrate, 0.25% MnO2 and 0.25% CaO2 accounting for the total mass of nickel cobalt manganese hydroxide precursor and lithium salt are fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, heated to 500°C at 3°C / min in a tube furnace for 2h, and then heated to 800°C at 1.5°C / min for sintering for 12h. After sintering, naturally cool to room temperature, take out the sample, sieve with a 400-mesh sieve, and obtain a once-sintered ternary positive electrode material.

[0040] Example 3

[0041] The present invention provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0042] 200g of nickel-cobalt-manganese hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2, 92g lithium hydroxide monohydrate, 0.2% MnO2, 0.2% CaO2 and 0.1% BaO2 accounting for the total mass of nickel cobalt manganese hydroxide precursor and lithium salt are fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, heated to 500°C at 3°C / min in a tube furnace for 2h, and then heated to 800°C at 1.5°C / min for sintering for 12h. After sintering, naturally cool to room temperature, take out the sample, sieve with a 400-mesh sieve, and obtain a once-sintered ternary positive electrode material.

[0043] Example 4

[0044] The present invention provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0045] 200g of nickel-cobalt-manganese hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05(OH)2, 92g of lithium hydroxide monohydrate, and MnO2 accounting for 2% of the total mass of nickel-cobalt-manganese hydroxide precursor and lithium salt are fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, heated to 500°C at 3°C / min in a tube furnace for 2h, and then heated to 800°C at 1.5°C / min for sintering for 12h. After sintering, naturally cool to room temperature, take out the sample, sieve with a 400-mesh sieve, and obtain a ternary positive electrode material.

[0046] Example 5

[0047] The present invention provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0048] 200g of nickel-cobalt-manganese hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2, 92g of lithium hydroxide monohydrate, and 0.1% of MnO2 in the total mass of nickel-cobalt-manganese hydroxide precursor and lithium salt were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, heated to 500°C at 3°C / min in a tube furnace for 2h, and then heated to 800°C at 1.5°C / min for sintering for 12h. After sintering, naturally cool to room temperature, take out the sample, sieve with a 400-mesh sieve, and obtain a ternary positive electrode material.

[0049] Example 6

[0050] The present invention provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0051] 200g of nickel-cobalt-manganese hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2, 92g of lithium hydroxide monohydrate, and 0.5% of the total mass of ZnO2 of nickel-cobalt-manganese hydroxide precursor and lithium salt were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, heated to 500°C at 3°C / min in a tube furnace for 2h, and then heated to 800°C at 1.5°C / min for sintering for 12h. After sintering, naturally cool to room temperature, take out the sample, sieve with a 400-mesh sieve, and obtain a ternary positive electrode material.

[0052] Comparative Example 1

[0053] The present invention provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0054] 200g of nickel-cobalt-manganese hydroxide precursor Ni 0.83 Co0.12 Mn 0.05 (OH)2 and 92g of lithium hydroxide monohydrate were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, heated to 500°C at 3°C / min in a tube furnace, kept for 2h, and then heated to 800°C at 1.5°C / min for sintering for 12h. After sintering, the sample was naturally cooled to room temperature, taken out, sieved with a 400-mesh sieve, and a ternary positive electrode material was obtained.

[0055] Test: The ternary positive electrode materials prepared in Examples 1-6 and Comparative Example 1 were tested by XRD and refined, and the results of lithium-nickel mixing of each sample were shown in Table 1 below; the above ternary positive electrode materials were assembled into button-type CR2032 batteries for cycle testing. The specific process of button battery preparation is as follows: the prepared ternary material, Super P and polyvinylidene fluoride were weighed in a mass ratio of 95:3:2, mixed evenly, added with an appropriate amount of NMP and stirred for 3 hours to obtain a viscous slurry, and evenly coated on aluminum foil using a coating machine, baked at 120°C in a vacuum oven for 8 hours, and pressed using a roller press, and finally cut into pole pieces with a diameter of 12 mm. A pure lithium sheet with a diameter of 16 mm was used as the negative electrode sheet, a mixed solution of 1 mol / L LiPF6+DEC / EC (volume ratio 1:1) was used as the electrolyte, and a 18 mm poly Celgard propylene microporous membrane was used as the diaphragm, and assembled into a button-type CR2032 battery in a glove box filled with argon. The prepared button cell was charged and discharged using the Xinwei test channel at a voltage of 3.0 to 4.3 V and at rates of 0.1C, 0.33C, and 1C. The test results of the discharge specific capacity are shown in Table 2 below:

[0056] Table 1

[0057]

[0058] Table 2

[0059]

[0060] Conclusion, by Figure 2It can be seen that the ternary positive electrode materials synthesized in the embodiments and comparative examples are in good condition, and the data in Table 1 are obtained through refinement. It can be seen from Tables 1 and 2 that the comparison between Example 1 and Comparative Example 1 shows that the doped ternary positive electrode lithium-nickel mixed array prepared by sintering with oxygen-rich oxygen storage materials is lighter, and has better capacity and rate performance. This is because more oxygen is generated during the sintering process, and it is easier to oxidize divalent nickel into trivalent nickel, thereby reducing the divalent nickel content in the ternary positive electrode material, reducing the degree of lithium-nickel mixing in the ternary positive electrode material, and being more conducive to the migration of lithium ions during the charge and discharge process, thereby improving the specific capacity and rate performance of the ternary positive electrode material. By comparing Example 1, Example 2 and Example 3, it can be seen that the doped ternary positive electrode lithium-nickel mixed array prepared by sintering with a variety of oxygen-rich oxygen storage materials with different decomposition temperatures is lighter, and has better capacity and rate performance. This is Since the oxygen generation time is dispersed, oxygen is continuously generated during the heating process, so that the ternary positive electrode material is always kept in an oxygen atmosphere, which is convenient for oxygen to enter the interior of the ternary positive electrode, and the internal divalent nickel is more easily oxidized to form trivalent nickel; from the comparison of Example 1, Example 4 and Example 5, it can be seen that the proportion of oxygen-rich oxygen storage material added is preferably 0.2% to 1.5%. When the amount added is too little, less oxygen is generated, less divalent nickel is oxidized, and the performance improvement is small. When the amount added is too much, there are too many inactive substances in the sample and the performance is reduced; from the comparison of Example 1 and Example 6, it can be seen that when the decomposition temperature of the added oxygen-rich oxygen storage material is close to the temperature range in which the ternary positive electrode material requires oxygen to participate in the reaction, the doped ternary positive electrode lithium-nickel mixed array prepared by sintering is lighter and has better capacity and rate performance. This is because the generated oxygen is easy to react with the ternary positive electrode material.

[0061] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A ternary positive electrode material, characterized in that: The invention comprises a material prepared from a nickel-cobalt-manganese hydroxide precursor, a lithium salt and an oxygen-rich oxygen storage material. The oxygen-rich oxygen storage material is used to generate oxygen during the preparation process to convert divalent nickel into trivalent nickel to reduce the content of divalent nickel.

2. A ternary positive electrode material according to claim 1, characterized in that: The oxygen-rich oxygen storage material includes one or a mixture of multiple of MnO2, CaO2, ZnO2, CeO2, SrO2, and MgO2.

3. A ternary positive electrode material according to claim 2, characterized in that: The content of the oxygen-rich oxygen storage material accounts for 0.2% to 1.5% of the total mass of the nickel-cobalt-manganese hydroxide precursor and the lithium salt.

4. A ternary positive electrode material according to claim 3, characterized in that: The oxygen-rich oxygen storage material includes MnO2, CaO2 and BaO2.

5. A method for preparing the ternary positive electrode material according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: mixing a nickel-cobalt-manganese hydroxide precursor, a lithium salt and an oxygen-rich oxygen storage material to obtain a mixture; S2: Sintering the mixture, cooling and sieving in sequence after sintering to obtain a ternary positive electrode material.

6. The method for preparing a ternary positive electrode material according to claim 5, characterized in that: The temperature at which the oxygen-rich oxygen storage material decomposes to generate oxygen is lower than the sintering temperature in S2.

7. The method for preparing a ternary positive electrode material according to claim 6, characterized in that: The sintering process in S2 includes first heating the temperature to 500-600°C at a rate of 1-5°C / min, keeping the temperature for 1-5 hours, and then heating the temperature to 700-950°C at a rate of 1-3°C / min for sintering. The sintering time is 8-20 hours.

8. The method for preparing a ternary positive electrode material according to claim 7, characterized in that: The oxygen-rich oxygen storage material is a mixture of oxides having different decomposition temperatures to generate oxygen.

9. The method for preparing a ternary positive electrode material according to claim 8, characterized in that: The oxygen-rich oxygen storage material can modify the ternary positive electrode material.

10. The method for preparing a ternary positive electrode material according to claim 5, characterized in that: The mass ratio of the nickel-cobalt-manganese hydroxide precursor to the lithium salt is 1:0.45-0.55.

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