Core-shell gradient ternary precursor, its preparation and use

Abstract

The present application provides a core-shell gradient ternary precursor, its preparation method and use, the preparation method including: (1) mixing terephthalic acid solution with liquid alkali to obtain terephthalic acid salt solution, adding nickel source solution to react, obtaining Ni-MOF solution, mixing Ni-MOF solution with ammonia water, adjusting pH, obtaining substrate solution; and (2) simultaneously adding nickel-cobalt-manganese ternary mixed salt solution, liquid caustic soda solution, and ammonia water solution to the substrate solution obtained in step (1) to carry out co-precipitation reaction, and aging to obtain the core-shell gradient ternary precursor. In the present application, Ni-MOF is prepared in advance, and the Ni-MOF is used as a core to carry out co-precipitation reaction to prepare a core-shell gradient precursor. In the preparation of a positive electrode material, the carbon in the core reacts with oxygen to reduce the oxidation state of nickel on the surface of the particles, thereby reducing the occurrence of cracks.

Description

[Technical Field]

[0001] The present application is in the field of lithium ion batteries and relates to a core-shell gradient ternary precursor, and its preparation and use. [Background technology]

[0002] To meet the high energy demands of electric vehicles, nickel-rich layered material LiNi l-x-y Mn x Co y O2(x+y≦0.4)(NCM) and LiNi 0.8 Co 0.15 Al 0.05 O2 is considered the most promising candidate for the cathode material. It has a capacity of 200mAh / g and a high voltage of 3.8V (vs. Li+ / Li). However, Li + / Ni 2+ Problems such as cation mixing, Li retention, poor thermal stability, and powdering limit the cycleability and rate capability of the battery. Scientists have attempted to improve the stability of the structure by using various strategies, including element doping, surface coating, and the formation of concentration gradients.

[0003] Chinese Patent Publication No. 112701271 discloses an element doping method based on a ternary precursor positive electrode material, which includes the steps of weighing and dissolving a soluble nickel salt, a soluble cobalt salt, and a soluble manganese salt in deionized water to obtain a ternary metal salt solution; preparing a basic complexing agent, mixing the basic complexing agent with the ternary metal salt solution to react, and then collecting, filtering, washing with water, and drying in sequence to obtain a ternary precursor powder.

[0004] Chinese Patent Publication No. 111422926 discloses a core-shell structured Al / La co-doped high-nickel ternary precursor, a method for preparing the same, and a cathode material prepared using the precursor. The preparation method is mainly divided into three steps: in the first step, an Al-doped high-nickel ternary precursor with rod-shaped primary particles is synthesized at a low pH; in the second step, the pH is adjusted to a high level based on the above, and the Al-doped high-nickel ternary precursor is used as a core to grow a La-doped high-nickel ternary precursor shell with needle-shaped primary particles, thereby synthesizing an Al / La co-doped high-nickel ternary precursor with a core-shell structure.

[0005] While element doping can significantly improve the cycling stability of cathode materials, it also leads to the problem of capacity fading. Applying a protective layer to secondary particles can isolate the active material from the electrolyte, but it cannot prevent grain boundary cracking within primary particles due to frequent volume changes during electrochemical cycling. As a result, the accumulated strain within each primary particle leads to the crushing of the secondary particles. While concentration gradients are a preferred method, the manufacturing process is tedious, severely limiting mass production. Summary of the Invention [Problem to be solved by the invention]

[0006] The following is a summary of the subject matter described in detail herein, which is not intended to limit the scope of protection of the claims.

[0007] The purpose of this application is to provide a core-shell gradient ternary precursor, its preparation method, and use. In this application, Ni-MOF is prepared in advance, and a core-shell gradient precursor is prepared by co-precipitation using the Ni-MOF as a core. In the production of cathode materials, the carbon in the core reacts with oxygen to reduce the oxidation state of nickel on the particle surface, thereby reducing the occurrence of cracks. [Means for solving the problem]

[0008] To achieve the objectives of this application, this application adopts the following technical solutions:

[0009] In a first aspect, the present application provides a method for manufacturing a semiconductor device comprising: (1) mixing a terephthalic acid solution with a liquid alkali to obtain a terephthalate solution, adding a nickel source solution to react with the solution to obtain a Ni-MOF solution, and mixing the Ni-MOF solution with ammonia water to adjust the pH to obtain a substrate solution; (2) simultaneously adding a nickel-cobalt-manganese ternary mixed salt solution, a liquid caustic soda solution, and an aqueous ammonia solution to the substrate solution obtained in step (1), to carry out a co-precipitation reaction, and then aging to obtain the core-shell gradient ternary precursor.

[0010] In this application, Ni-MOF (the structure of the Ni-MOF is shown in Formula I) is prepared in advance, and then a coprecipitation reaction is carried out using the Ni-MOF as a core to prepare a core-shell gradient precursor. During the production of a cathode material, a protective layer containing a rock salt phase is formed on the surface of the precursor, which resists internal strain, inhibits further phase change, reduces the occurrence of cracks, and improves the cycle stability of the cathode material. This production method simplifies the production process and is suitable for mass production. [ka]

[0011] Preferably, in step (1), the molar concentration of the terephthalic acid solution is 1 to 3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L.

[0012] Preferably, the liquid alkali comprises potassium hydroxide solution.

[0013] Preferably, the molar concentration of the liquid alkali is 2 to 6 mol / L, for example, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, or 6 mol / L.

[0014] Preferably, the pH of the terephthalate solution is 6 to 7, for example, 6, 6.2, 6.5, 6.8 or 7.

[0015] Preferably, the nickel source solution comprises a nickel nitrate solution.

[0016] Preferably, the molar concentration of the nickel nitrate solution is 1 to 3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L.

[0017] Preferably, the molar ratio of the terephthalic acid to the nickel element in the nickel source is 1:(0.8 to 1.2), for example, 1:0.8, 1:0.9, 1:1, 1:1.1, or 1:1.2.

[0018] Preferably, in step (1), the reaction is carried out with stirring.

[0019] Preferably, the stirring time is 24 to 48 hours, for example, 24 hours, 30 hours, 36 hours, 40 hours, or 48 hours.

[0020] Preferably, the reaction is followed by filtration, washing, and drying.

[0021] Preferably, the cleaning agent comprises absolute ethanol.

[0022] Preferably, the drying temperature is 40 to 60°C, for example, 40°C, 45°C, 50°C, 55°C, or 60°C.

[0023] Preferably, in step (1), the mass concentration of aqueous ammonia in the substrate solution is 4 to 8 g / L, for example, 4 g / L, 5 g / L, 6 g / L, 7 g / L, or 8 g / L.

[0024] Preferably, the mass concentration of Ni-MOF in the substrate solution is 50 to 150 g / L, for example, 50 g / L, 80 g / L, 100 g / L, 120 g / L, or 150 g / L.

[0025] Preferably, the pH of the substrate solution is 11 to 12, for example, 11, 11.2, 11.5, 11.8, or 12.

[0026] Preferably, in step (2), the mass concentration of the solute in the nickel-cobalt-manganese ternary mixed salt solution is 80 to 120 g / L, for example, 80 g / L, 90 g / L, 100 g / L, 110 g / L, or 120 g / L.

[0027] Preferably, the rate at which the nickel-cobalt-manganese ternary mixed salt solution is added is 6 to 10 L / h, for example, 6 L / h, 7 L / h, 8 L / h, 9 L / h, or 10 L / h.

[0028] Preferably, the mass concentration of the liquid caustic soda solution is 28 to 32%, for example, 28%, 29%, 30%, 31%, or 32%.

[0029] Preferably, the rate at which the liquid caustic soda solution is added is 2 to 3 L / h, such as 2 L / h, 2.2 L / h, 2.5 L / h, 2.8 L / h, or 3 L / h.

[0030] Preferably, the mass concentration of the aqueous ammonia solution is 10 to 20%, for example, 10%, 12%, 15%, 18%, or 20%.

[0031] Preferably, the rate at which the aqueous ammonia solution is added is 0.1 to 0.6 L / h, for example, 0.1 L / h, 0.2 L / h, 0.3 L / h, 0.4 L / h, 0.5 L / h, or 0.6 L / h.

[0032] Preferably, in step (2), the stirring speed of the coprecipitation reaction is 200 to 400 rpm, for example, 200 rpm, 250 rpm, 300 rpm, 350 rpm, or 400 rpm.

[0033] Preferably, the pH of the coprecipitation reaction is 10 to 12, for example, 10, 10.5, 11, 11.5, or 12.

[0034] Preferably, the temperature of the coprecipitation reaction is 40 to 60°C, for example, 40°C, 45°C, 50°C, 55°C, or 60°C.

[0035] Preferably, the particle diameter is continuously monitored during the coprecipitation reaction, and until the particle diameter meets the requirement, a high-performance concentrator is used in the reaction to collect all particles so that they are returned to the reaction vessel, and the reaction is continued to grow, and the particle diameter D 50 When the thickness reaches 3 to 4 μm (for example, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, or 4 μm), the supply is stopped and the reaction is continued until the material is completely reacted.

[0036] In a second aspect, the present application provides a core-shell gradient ternary precursor produced by the method of the first aspect.

[0037] In the production of cathode materials, the core-shell gradient ternary precursor of the present application allows the carbon in the core to react with oxygen, thereby reducing the oxidation state of the nickel on the surface of the particles and reducing the occurrence of cracks.

[0038] In a third aspect, the present application provides a core-shell gradient ternary cathode material made with the core-shell gradient ternary precursor according to the second aspect.

[0039] In a fourth aspect, the present application provides a positive electrode plate comprising the core-shell gradient ternary positive electrode material according to the third aspect.

[0040] In a fifth aspect, the present application provides a lithium ion battery comprising the positive electrode plate according to the fourth aspect. [Effects of the Invention]

[0041] Compared with the prior art, the present application has the following beneficial effects: In this application, Ni-MOF is prepared in advance, and then a coprecipitation reaction is carried out using the Ni-MOF as the core to prepare a core-shell gradient precursor. In the production of cathode materials, the carbon in the core of the core-shell gradient ternary precursor reacts with oxygen, reducing the oxidation state of nickel on the particle surface and reducing the occurrence of cracks.

[0042] Other aspects can be understood upon review and understanding of the detailed description and drawings. [Brief explanation of the drawings]

[0043] [Figure 1] 1 is a process flow chart of the manufacturing method of Example 1 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0044] The technical solutions of the present application are further described below through specific embodiments. Those skilled in the art will appreciate that the above examples are merely provided to facilitate understanding of the present application, and should not be construed as particularly limiting the present application. [Example]

[0045] Example 1 This embodiment provides a core-shell gradient ternary precursor, and the preparation method of the core-shell gradient ternary precursor is as follows:

[0046] (1) 50 L of 1 mol / L terephthalic acid was added to a 200 L reactor, mechanical stirring was initiated, and 50 L of 2 mol / L potassium hydroxide solution was added to convert the terephthalic acid to potassium terephthalate (pH: 6-7). Next, 50 L of 1 mol / L nickel nitrate solution was added dropwise to the potassium terephthalate solution at a flow rate of 2 L / h. Immediately after this, a large amount of green precipitate was generated. The precipitate was stirred for 36 hours, filtered, washed three times with ethanol, washed five times with pure water, and dried at 50 °C to obtain Ni-MOF.

[0047] (2) A 100g / L nickel-cobalt-manganese ternary mixed salt solution, a 30% mass concentration liquid caustic soda solution, and a 15% mass concentration aqueous ammonia solution were fed at feed rates of 8L / h, 2.65L / h, and 0.8L / h, respectively, and simultaneously added to a reactor containing a substrate solution with a temperature of 58°C, an aqueous ammonia concentration of 8g / L, a Ni-MOF content of 100g / L, and a pH of 11.8. The coprecipitation reaction was carried out at a stirring speed of 380 rpm. During the reaction, the pH of the reaction system was controlled at 11.3, the ammonia concentration at 6.5g / L, and the temperature at 58°C. High-purity nitrogen gas was continuously introduced. The particle size was monitored during the reaction, and until the particle size requirement was met, a high-performance concentrator was used to collect all the particles and return them to the reactor to continue the reaction and growth. The particle size D 50 When the particle size reached 4 μm, the feed was stopped and the reaction was continued until the material was fully reacted. After centrifugation, washing, and baking, the core-shell gradient ternary precursor with the Ni-MOF core was obtained.

[0048] A process flow chart of the manufacturing method is shown in FIG.

[0049] Example 2 This embodiment provides a core-shell gradient ternary precursor, and the preparation method of the core-shell gradient ternary precursor is as follows:

[0050] (1) 50 L of 1.2 mol / L terephthalic acid was added to a 200 L reactor, mechanical stirring was initiated, and 50 L of 2.4 mol / L potassium hydroxide solution was added to convert the terephthalic acid to potassium terephthalate (pH: 6-7). Next, 50 L of 1.3 mol / L nickel nitrate solution was added dropwise to the potassium terephthalate solution at a flow rate of 2 L / h. Immediately after this, a large amount of green precipitate was generated. The precipitate was stirred for 38 hours, filtered, washed three times with ethanol, washed five times with pure water, and dried at 50 °C to obtain Ni-MOF.

[0051] (2) A 100g / L nickel-cobalt-manganese ternary mixed salt solution, a 32% mass concentration liquid caustic soda solution, and a 16% mass concentration aqueous ammonia solution were fed at feed rates of 8L / h, 2.65L / h, and 0.8L / h, respectively, and simultaneously added to a reactor containing a substrate solution with a temperature of 58°C, an aqueous ammonia concentration of 8g / L, a Ni-MOF content of 100g / L, and a pH of 11.8. The coprecipitation reaction was carried out at a stirring speed of 380 rpm. During the reaction, the pH of the reaction system was controlled at 11.3, the ammonia concentration at 6.5g / L, and the temperature at 58°C. High-purity nitrogen gas was continuously introduced. The particle size was monitored during the reaction, and until the particle size requirement was met, a high-performance concentrator was used to collect all the particles and return them to the reactor to continue the reaction and growth. The particle size D 50 When the particle size reached 3.5 μm, the feed was stopped and the reaction was continued until the material was fully reacted. After centrifugation, washing, and baking, the core-shell gradient ternary precursor with the Ni-MOF core was obtained.

[0052] Example 3 The present example differs from Example 1 only in that the concentration of nickel nitrate was 0.6 mol / L, and the remaining conditions and parameters were exactly the same as those of Example 1.

[0053] Example 4 In this example, the only difference from Example 1 was that the concentration of nickel nitrate was 1.5 mol / L, and the remaining conditions and parameters were exactly the same as those of Example 1.

[0054] Example 5 In this example, the only difference from Example 1 was that the pH was controlled at 9 during the reaction, and the remaining conditions and parameters were exactly the same as those in Example 1.

[0055] Example 6 In this example, the only difference from Example 1 was that the pH was controlled at 12 during the reaction, and the other conditions and parameters were exactly the same as those in Example 1.

[0056] Example 7 The present example differs from Example 1 only in that the particle size of the precursor was 2.5 μm, and the remaining conditions and parameters were exactly the same as those of Example 1.

[0057] Example 8 The present example differs from Example 1 only in that the particle size of the precursor was 4.5 μm, and the remaining conditions and parameters were exactly the same as those of Example 1.

[0058] Comparative Example 1 In this comparative example, the only difference compared to Example 1 is that Ni-MOF was replaced with carbon microspheres, and the rest of the conditions and parameters were exactly the same as those in Example 1.

[0059] Performance Test The precursors obtained in Examples 1 to 8 and Comparative Example 1 were mixed with a lithium source, LiOH, and the resulting samples were calcined at 800°C for 16 hours under pure oxygen. During high-temperature calcination, Ni-MOF-74 carbonized and reacted with the precursor, resulting in the formation of the final NMC811. The cathode material, conductive agent SuperP (conductive carbon black), and binder PVDF (polyvinylidene fluoride) were mixed in a 90:5:5 ratio to form a slurry. This slurry was then uniformly applied to an aluminum foil current collector and baked in an oven at 80°C for 12 hours. The resulting cathode was then cut into 12 mm diameter positive electrode plates. The anode consisted of a 18 mm diameter, 1 mm thick lithium foil, the separator a Celgard polyethylene porous membrane, and the electrolyte a mixture of equal parts ethylene carbonate (EC) and diethyl carbonate (DEC) with 1 mol / L LiPF6 (lithium iron phosphate) electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled in a glove box where the moisture and oxygen content was less than 0.1 ppm to form a 2032 button battery. The battery was left for 12 hours before undergoing a performance test. The test results are shown in Table 1. [Table 1]

[0060] As can be seen from Table 1, in Examples 1 to 8, after batteries were fabricated using the precursors of the present invention, the 0.1C initial discharge specific capacity was 190.2 mAh / g or more, the 1C initial discharge specific capacity was 170 mAh / g or more, the 1C 100th cycle discharge specific capacity was 164.7 mAh / g or more, and the 1C 100th cycle capacity retention rate was 96.8% or more.

[0061] Comparing Example 1 with Examples 3 and 4, it was found that the molar ratio of nickel to terephthalic acid in the Ni-MOF preparation process affected the quality of the Ni-MOF and the performance of the precursor. By controlling the molar ratio of nickel to terephthalic acid to 0.8-1.2:1, the Ni-MOF produced was of high quality and more suitable for preparing the core of the core-shell gradient ternary precursor.

[0062] Comparing Examples 1 and 5-6, the pH of the substrate solution affects the quality of the core-shell gradient ternary precursor. By controlling the pH during the reaction between 10.5 and 11.5, the core-shell gradient ternary precursor was of high quality. If the pH during the reaction was too high, the ternary precursor produced contained too many small particles, all cores, and no spheres. If the pH during the reaction was too low, the primary particles of the ternary precursor produced were particularly coarse, preventing the formation of regular spheres.

[0063] Comparing Example 1 with Examples 7 and 8, the particle size of the core-shell gradient ternary precursor influences the performance of the resulting core-shell gradient ternary material. By controlling the particle size of the core-shell gradient ternary precursor to 3-4 μm, the resulting core-shell gradient ternary material exhibited excellent performance. However, if the particle size of the core-shell gradient ternary precursor is too large, cracks will occur and the electrochemical specific surface area will be too small, thereby affecting the performance of the cathode material. If the particle size of the core-shell gradient ternary precursor is too small, the cathode material produced from the precursor will not be able to form stable Li diffusion paths, resulting in a decrease in the initial charge / discharge capacity of the cathode material.

[0064] Comparing Example 1 and Comparative Example 1, in this application, a coprecipitation reaction is carried out using Ni-MOF as a core to prepare a core-shell gradient precursor. During the production of the cathode material, a protective layer containing a rock salt phase is formed on the surface of the precursor, which resists internal strain, inhibits further phase change, reduces the occurrence of cracks, and improves the cycle stability of the cathode material.

[0065] The above are only specific embodiments of the present application, but the applicant declares that the scope of protection of the present application is not limited thereto, and it is obvious to those skilled in the art that any modifications or replacements that can be easily conceived by those skilled in the art within the technical scope revealed by the present application are included in the scope of protection and disclosure of the present application.

Claims

1. (1) mixing a terephthalic acid solution with a liquid alkali to obtain a terephthalate solution, adding a nickel source solution to react with the solution to obtain a Ni-MOF solution, and mixing the Ni-MOF solution with ammonia water to adjust the pH to obtain a substrate solution; (2) adding nickel-cobalt-manganese ternary mixed salt solution, liquid caustic soda solution, and aqueous ammonia solution to the substrate solution obtained in step (1) simultaneously to carry out co-precipitation reaction, and then aging to obtain a core-shell gradient ternary precursor; A method for producing a core-shell gradient ternary precursor, comprising:

2. In step (1), the molar concentration of the terephthalic acid solution is 1 to 3 mol / L. The method of claim 1.

3. The method of claim 1 , wherein the liquid alkali comprises potassium hydroxide solution.

4. The method according to claim 1, wherein the liquid alkali has a molar concentration of 2 to 6 mol / L.

5. The method according to claim 1, wherein the pH of the terephthalate solution is 6 to 7.

6. The method of claim 1 , wherein the nickel source solution comprises a nickel nitrate solution.

7. The method according to claim 6, wherein the molar concentration of the nickel nitrate solution is 1 to 3 mol / L.

8. 2. The method according to claim 1, wherein the molar ratio of the terephthalic acid to the nickel element in the nickel source is 1:(0.8 to 1.2).

9. The method according to claim 1 , wherein in step (1), stirring is performed during the reaction.

10. The method according to claim 9, wherein the stirring time is 24 to 48 hours.

11. The method of claim 1, wherein after the reaction in step (1), the resulting Ni-MOF solution is filtered, washed, and dried, and then mixed with aqueous ammonia.

12. The method of claim 11 , wherein the cleaning agent comprises absolute ethanol.

13. The method according to claim 11, wherein the drying temperature is 40 to 60°C.

14. The method according to claim 1, wherein in step (1), the mass concentration of aqueous ammonia in the substrate solution is 4 to 8 g / L.

15. The method according to claim 1, wherein the mass concentration of the Ni-MOF in the substrate solution is 50 to 150 g / L.

16. The method according to claim 1, wherein the substrate solution has a pH of 11 to 12.

17. The method according to claim 1, wherein in step (2), the mass concentration of the solute in the nickel-cobalt-manganese ternary mixed salt solution is 80 to 120 g / L.

18. 2. The method according to claim 1, wherein the nickel-cobalt-manganese ternary mixed salt solution is added at a rate of 6 to 10 L / h.

19. The method of claim 1, wherein the mass concentration of the liquid caustic soda solution is 28 to 32%.

20. The method of claim 1, wherein the rate of adding the liquid caustic soda solution is 2 to 3 L / h.

21. The method according to claim 1, wherein the mass concentration of the aqueous ammonia solution is 10 to 20%.

22. The method according to claim 1, wherein the rate at which the aqueous ammonia solution is added is 0.1 to 0.6 L / h.

23. 2. The method according to claim 1, wherein in step (2), the stirring speed of the coprecipitation reaction is 200 to 400 rpm.

24. 2. The method according to claim 1, wherein the pH during the coprecipitation reaction is 10 to 12.

25. The method according to claim 1, wherein the temperature of the coprecipitation reaction is 40 to 60°C.

26. During the coprecipitation reaction, the particle diameter is continuously monitored, and until the particle diameter meets the requirement, a high-performance concentrator is used to collect all particles and return them to the reactor, allowing them to react and grow continuously. 50 2. The method of claim 1, wherein the feeding is stopped when the thickness reaches 3-4 μm, and the reaction is continued until the material is completely reacted.

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