A heteropolyacid-doped modified cathode precursor, its preparation method and application

Abstract

This invention provides a heteropolyacid-doped modified cathode precursor, its preparation method, and its application. The chemical formula of the heteropolyacid-doped modified cathode precursor is Ni. x Co y Y z (X a M b O c ) n (OH) 2‑n Where Y includes Mn and / or Al, 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1, 0.00001≤n≤0.001, [X a M b O c [ ] is the anion of a heteropolyacid, X includes P and / or Si, M includes any one or a combination of at least two of Mo, W, V, Cr, Nb or Ta, and a:b:c = 1:(6-18):(18-62). This invention utilizes heteropolyacids to dope and modify the cathode precursor, achieving atomic-level dispersion and uniform distribution of the doping elements.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, and relates to a heteropolyacid doped modified cathode precursor, its preparation method and application. Background Technology

[0002] High specific capacity, high cycle stability, and high safety are the main goals pursued in ternary cathode materials, including high-nickel ternary cathodes and lithium-rich manganese-based ternary cathodes. Doping modification is the main means to achieve these goals. Common doping elements include Mo, W, V, Zr, Nb, Mg, P, and Si. The dopants used are usually nano-metal oxides or hydroxides, and water-soluble metal salts are used as dopants in co-precipitation systems.

[0003] CN114560515A discloses a method for preparing aluminum-coated ternary precursors using a sol-gel method. The method includes: A) dispersing Ni(NO3)2, Co(NO3)2, and Mn(NO3)2 in a deionized water solvent according to a dosage ratio. B) adding the solution from (1) dropwise to a citric acid-ethylene glycol solution, controlling the temperature and stirring continuously, and controlling the molar ratio of citric acid to metal ions to form a sol-gel system. C) heating the gel to a certain temperature to form a dry gel, then ball-milling it into powder. D) adding excess ammonia to an Al(NO3)3 solution, generating a precipitate, and then slowly adding nitric acid to generate an Al sol. E) dispersing the powder from (3) into the Al sol, heating, stirring, filtering, evaporating, and drying to obtain an Al-coated ternary material precursor.

[0004] CN112164798A discloses a surface-stability-enhanced cathode material and its preparation method. The preparation process is as follows: (1) Phosphoric acid, a salt containing element M, and water are mixed, heated, and stirred to obtain an M salt solution. The M element is selected from one or more of W, Mo, and V. (2) A dispersant and a salt containing element A are added to the M salt solution, and the pH is adjusted to obtain a mixed solution. The A element is selected from one or more of Mg, Ti, and Nb. (3) The mixed solution is subjected to a hydrothermal reaction to obtain a reaction solution. (4) The reaction solution is mixed and stirred with the cathode material to obtain a slurry. The slurry is filtered, washed, and dried to obtain a powder. (5) The powder is sintered in two stages under an oxygen atmosphere to obtain a surface-stability-enhanced cathode material. This method uses a hydrothermal reaction to prepare the reaction solution. The hydrothermal reaction temperature is 200-300℃, and the hydrothermal reactor is under high pressure. This method has high energy consumption, high safety risks, high cost, and is not suitable for large-scale industrial production.

[0005] The above-mentioned preparation process is complex, the operating cost is high, and the doping effect is poor, making it unsuitable for actual production. Summary of the Invention

[0006] The purpose of this invention is to provide a heteropolyacid-doped modified cathode precursor, its preparation method and application. This invention utilizes heteropolyacids to dope and modify the cathode precursor, achieving atomic-level dispersion and uniform distribution of the doping elements.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a heteropolyacid-doped modified cathode precursor, wherein the chemical formula of the heteropolyacid-doped modified cathode precursor is Ni. x Co y Y z (X a M b O c ) n (OH) 2-n Where Y includes Mn and / or Al, 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1, 0.00001≤n≤0.001, [X a M b O c [] is the anion of a heteropolyacid, X includes P and / or Si, M includes any one or at least two combinations of Mo, W, V, Cr, Nb or Ta (typical but non-limiting combinations include combinations of Mo and W, V and Cr, Mo and Nb, Mo, W and V, etc.), a:b:c = 1:(6 to 18):(18 to 62), for example: 1:12:40, 2:18:62, 1:6:18, 1:9:32 or 1:12:42, etc., not limited to the listed values, other unlisted values ​​within this range also apply.

[0009] Heteropoly acids are a general term for condensed oxyacids obtained by the condensation of different oxyacids, with the keggin type [PMo] as an example. 12 O 40 ] 4- Taking anions as an example, the PO4 tetrahedron is located at the center of the anionic structure and is surrounded by 12 MoO6 octahedra. The three octahedral structures are connected to form a trimetallic cluster {Mo3O}. 10 The four trimetallic clusters are connected at common angles to form a cage-like structure, which enables it to transport and store electrons. This invention dops the cathode precursor with heteropolyacids, resulting in a more uniform distribution of heteroatoms and metal elements in the precursor. This leads to more uniform diffusion during lithium-nickel mixing and sintering. Simultaneously, the heteroatoms and metal elements help reduce lithium-nickel mixing, delay the H2→H3 phase transition, and suppress oxygen loss, thereby improving the cathode's cycle performance.

[0010] Preferably, the doping amount of element M in the heteropolyacid-doped modified cathode precursor is 60 to 18000 ppm, more preferably 1000 to 10000 ppm, for example: 1000 ppm, 2000 ppm, 5000 ppm, 8000 ppm or 10000 ppm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0011] Preferably, the doping amount of X in the heteropolyacid-doped modified cathode precursor is 10 to 1000 ppm, more preferably 20 to 300 ppm, for example: 20 ppm, 50 ppm, 100 ppm, 200 ppm or 300 ppm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0012] In a second aspect, the present invention provides a method for preparing a heteropolyacid-doped modified cathode precursor as described in the first aspect, the method comprising the following steps:

[0013] A heteropolyacid solution is obtained by mixing the heteropolyacid with a solvent.

[0014] The cathode precursor is mixed with a heteropolyacid solution and then heated to obtain the heteropolyacid-doped modified cathode precursor.

[0015] In this invention, the heteropolyacid provides protons in water. The protons react with the hydroxide precursor to yield the corresponding metal ions. The anions of the heteropolyacid then combine with these metal ions to form precipitates. The method described in this invention can achieve atomic-level dispersion, with a uniform distribution of heteroatoms and polyatoms in the heteropolyacid anions. It has advantages such as simple operation, strong versatility, and uniform distribution of doped elements.

[0016] Preferably, the heteropolyacid includes any one or a combination of at least two of phosphomolybdic acid, phosphotungstic acid, silicotungstic acid, or silicotungstic acid. Typical but non-limiting combinations include combinations of phosphomolybdic acid and phosphotungstic acid, combinations of silicotungstic acid and silicotungstic acid, combinations of phosphomolybdic acid, phosphotungstic acid and silicotungstic acid, or combinations of phosphomolybdic acid, silicotungstic acid and silicotungstic acid, etc.

[0017] Preferably, the solvent includes ultrapure water and / or deionized water.

[0018] Preferably, the concentration of the heteropolyacid solution is 1 to 10 g / L, for example: 1 g / L, 2 g / L, 5 g / L, 8 g / L or 10 g / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] This invention can control the doping efficiency by adjusting the concentration of heteropolyacids and the heating temperature, thereby adjusting the doping amount of heteropolyacid anions and thus improving the performance of the cathode precursor.

[0020] Preferably, the positive electrode precursor includes any one or a combination of at least two of the following: ternary nickel-cobalt-manganese precursor, binary nickel-manganese precursor, ternary nickel-cobalt-aluminum precursor, or lithium-rich manganese-based precursor. Typical but non-limiting combinations include a combination of ternary nickel-cobalt-manganese precursor and binary nickel-manganese precursor, a combination of binary nickel-manganese precursor and ternary nickel-cobalt-aluminum precursor, or a combination of ternary nickel-cobalt-manganese precursor and lithium-rich manganese-based precursor.

[0021] Preferably, the temperature of the heating reaction is 40 to 90°C, for example: 40°C, 50°C, 60°C, 80°C or 90°C, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the heating reaction time is 0.5 to 8 hours, for example: 0.5 hours, 1 hour, 2 hours, 4 hours or 8 hours, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] Preferably, the stirring speed of the heating reaction is 100 to 500 rpm, for example: 100 rpm, 200 rpm, 300 rpm, 400 rpm or 500 rpm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Thirdly, the present invention provides a modified cathode material, which is prepared by mixing and sintering a heteropolyacid-doped modified cathode precursor as described in the first aspect with a lithium source.

[0025] Preferably, the lithium source includes lithium carbonate and / or lithium hydroxide.

[0026] Fourthly, the present invention provides a positive electrode sheet comprising a heteropolyacid-doped modified positive electrode material as described in the third aspect.

[0027] Fifthly, the present invention provides a lithium-ion battery comprising a positive electrode as described in the third aspect.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) This invention employs a wet process to modify the heteropolyacid doping of the cathode precursor, achieving atomic-level dispersion of dopant elements and resulting in a more uniform distribution. This facilitates the uniform diffusion of heteroatoms and polyatoms of the heteropolyacid during the sintering stage, significantly improving the charge-discharge and cycle performance of the material. Compared to the gel method, the method described in this invention is simpler, more compatible with existing precursor production lines, has lower production costs, and is easier for industrial production. Compared to the hydrothermal method, the method described in this invention has the advantages of lower risk and lower energy consumption.

[0030] (2) The battery obtained by the heteropolyacid doped modified cathode precursor of the present invention can achieve a first discharge capacity of 0.1C of more than 209 mAh / g and a cycle retention rate of more than 95.5% after 100 cycles. Attached Figure Description

[0031] Figure 1 This is the XRD pattern of the heteropolyacid-doped modified cathode precursor prepared in Example 1.

[0032] Figure 2 It is unmodified Ni 0.8 Co 0.1 Mn 0.1 XRD pattern of (OH)2 precursor.

[0033] Figure 3 This is a SEM image of the heteropolyacid-doped modified cathode precursor prepared in Example 1.

[0034] Figure 4 It is unmodified Ni 0.8 Co 0.1 Mn 0.1 SEM image of (OH)2 precursor.

[0035] Figure 5 This is the EDS image of the heteropolyacid-doped modified cathode precursor prepared in Example 1. Detailed Implementation

[0036] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0037] Example 1

[0038] This embodiment provides a heteropolyacid-doped modified cathode precursor, which is prepared by the following method:

[0039] (1) Take 34g of phosphomolybdic acid and add it to 10L of ultrapure water. Stir to dissolve and obtain phosphomolybdic acid solution;

[0040] (2) Take Ni 0.8 Co 0.1 Mn 0.1 5 kg of (OH)2 precursor was added to the above phosphomolybdic acid solution, heated to 60°C in a water bath, stirred at 400 rpm, and reacted for 4 h. Then, the mixture was centrifuged, washed with pure water, dried, sieved, and demagnetized to obtain the modified cathode precursor with a Mo doping amount of 4100 ppm and a P doping amount of 110 ppm.

[0041] Preparation of heteropolyacid-doped modified cathode precursor and unmodified Ni 0.8 Co0.1 Mn 0.1 The XRD pattern of the (OH)2 precursor is shown below. Figure 1-2 As shown, by Figure 1-2 It can be seen that the characteristic peaks (001), (100), (101), (102), (110), and (111) are characteristic peaks of nickel cobalt manganese hydroxide precursors. The diffraction peaks are consistent before and after the heteropoly acid doping modification, and there are no diffraction peaks of heteropoly acids.

[0042] Preparation of heteropolyacid-doped modified cathode precursor and unmodified Ni 0.8 Co 0.1 Mn 0.1 SEM image of (OH)2 precursor as shown in Figure Figure 3-4 As shown, by Figure 3-4 It can be seen that the morphology of the secondary particles did not change before and after the heteropolyacid doping modification, and there were no segregations on the surface of the secondary particles.

[0043] The EDS diagram of the heteropolyacid-doped modified cathode precursor is shown below. Figure 5 As shown, by Figure 5 It can be seen that the Mo and P elements are evenly distributed in the heteropolyacid-doped modified cathode precursor prepared by this invention.

[0044] Example 2

[0045] This embodiment provides a heteropolyacid-doped modified cathode precursor, which is prepared by the following method:

[0046] (1) Take 17g of silicotungstic acid and add it to 10L of ultrapure water. Stir to dissolve and obtain a silicotungstic acid solution.

[0047] (2) Take Ni 0.8 Co 0.1 Mn 0.1 5 kg of (OH)2 precursor was added to the above silicotungstic acid solution, heated to 75°C in a water bath, stirred at 400 rpm, and reacted for 4 h. Then, the mixture was centrifuged, washed with pure water, dried, sieved, and demagnetized to obtain the modified cathode precursor with W doping amount of 2400 ppm and Si doping amount of 30 ppm.

[0048] Example 3

[0049] This embodiment provides a heteropolyacid-doped modified cathode precursor, which is prepared by the following method:

[0050] (1) Take 43g of phosphotungstic acid and add it to 10L of ultrapure water. Stir to dissolve and obtain phosphotungstic acid solution;

[0051] (2) Take Ni 0.83 Co 0.06 Mn0.11 5 kg of (OH)2 precursor was added to the above phosphotungstic acid solution, heated to 65°C in a water bath, stirred at 500 rpm, and reacted for 4 h. Then, the mixture was centrifuged, washed with pure water, dried, sieved, and demagnetized to obtain the modified cathode precursor with W doping amount of 6500 ppm and P doping amount of 90 ppm.

[0052] Example 4

[0053] This embodiment provides a heteropolyacid-doped modified cathode precursor, which is prepared by the following method:

[0054] (1) Take 70g of molybdic acid and add it to 10L of ultrapure water. Stir to dissolve and obtain an aqueous solution of molybdic acid.

[0055] (2) Take Ni 0.83 Co 0.06 Mn 0.11 5 kg of (OH)2 precursor was added to the above aqueous solution of molybdic acid, heated to 75°C in a water bath, stirred at 350 rpm for 4 h, and then centrifuged, washed with pure water, dried, sieved and demagnetized to obtain the modified cathode precursor with Mo doping of 8200 ppm and Si doping of 200 ppm.

[0056] Example 5

[0057] The only difference between this embodiment and Embodiment 1 is that the mass of phosphomolybdic acid used in step (1) is 4g and the Mo doping amount is 520ppm. Other conditions and parameters are exactly the same as in Embodiment 1.

[0058] Example 6

[0059] The only difference between this embodiment and Embodiment 1 is that the mass of phosphomolybdic acid used in step (1) is 175g and the Mo doping amount is 20500pm. Other conditions and parameters are exactly the same as in Embodiment 1.

[0060] Example 7

[0061] The only difference between this embodiment and Embodiment 1 is that the mass of phosphomolybdic acid used in step (1) is 3.2g and the amount of P doping is 10ppm. Other conditions and parameters are exactly the same as in Embodiment 1.

[0062] Example 8

[0063] The only difference between this embodiment and Embodiment 1 is that the mass of phosphomolybdic acid used in step (1) is 168g and the amount of P doping is 540ppm. Other conditions and parameters are exactly the same as in Embodiment 1.

[0064] Example 9

[0065] The only difference between this embodiment and Embodiment 1 is that the heating reaction temperature is 30°C, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0066] Example 10

[0067] The only difference between this embodiment and Embodiment 1 is that the heating reaction temperature is 100°C, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0068] Comparative Example 1

[0069] This comparative example uses a physical mixing and sintering method to modify the cathode material with phosphomolybdic acid doping, including the following steps:

[0070] Ni 0.80 Co 0.10 Mn 0.10 The (OH)₂ precursor was mixed uniformly with lithium hydroxide and phosphomolybdic acid. The ratio of the total molar amounts of nickel, cobalt, and manganese, the molar amounts of lithium, molar amounts of molars, and the molar amounts of phosphorus was 1:1.03:0.0039:0.0003. The Mo content was Ni. 0.80 Co 0.10 Mn 0.10 The (OH)2 precursor contains 0.42% by mass, and the P content is Ni 0.80 Co 0.10 Mn 0.10 The (OH)2 precursor was 0.011% by mass, and then subjected to two-stage sintering in an oxygen atmosphere. The first stage sintering temperature was 420℃, the holding time was 4h, and the heating rate was 2℃ / min; the second stage sintering temperature was 720℃, the holding time was 8h, and the heating rate was 2℃ / min. (The finished product is a positive electrode material, so it does not need to be mixed with lithium source for sintering again).

[0071] Comparative Example 2

[0072] The only difference between this comparative example and Example 1 is that phosphomolybdic acid is not added; all other conditions and parameters are exactly the same as in Example 1.

[0073] Performance testing:

[0074] The precursor and lithium hydroxide mixture prepared in the examples and comparative examples were placed in a box furnace, with the total molar ratio of metal elements to lithium elements being 1:1.03. Two-stage sintering was performed under an oxygen atmosphere: the first stage sintering temperature was 420℃, held for 4 hours, and the heating rate was 2℃ / min; the second stage sintering temperature was 720℃, held for 8 hours, and the heating rate was 2℃ / min. After sintering, the mixture was cooled to room temperature to obtain the corresponding cathode material. A battery was then fabricated and its performance was tested. The test results are shown in Table 1.

[0075] Table 1

[0076] 0.1C initial discharge capacity (mAh / g) 100-week retention rate (%) Example 1 213.5 97.5 Example 2 211.5 96.6 Example 3 210.2 96.1 Example 4 209.0 95.5 Example 5 213.7 90.2 Example 6 210.2 97.5 Example 7 213.5 91.1 Example 8 210.3 97.6 Example 9 213.4 89.8 Example 10 209.8 97.6 Comparative Example 1 207.3 81.5 Comparative Example 2 205.5 65.2

[0077] As can be seen from Table 1, and from Examples 1-4, the battery obtained by the heteropolyacid doped modified cathode precursor of the present invention can achieve a first discharge capacity of 0.1C of more than 209 mAh / g and a cycle retention rate of more than 95.5% after 100 cycles.

[0078] A comparison of Examples 1 and 5-6 shows that the doping amount of element M in the heteropolyacid-doped modified cathode precursor of the present invention affects its performance. When the doping amount of element M is controlled between 1000 and 10000 ppm, the performance of the heteropolyacid-doped modified cathode precursor is better. If the doping amount of element M is too large, the discharge capacity is reduced; if the doping amount of element M is too small, the cycle performance is reduced.

[0079] A comparison of Examples 1 and 7-8 shows that the doping amount of element X in the heteropolyacid-doped modified cathode precursor of the present invention affects its performance. When the doping amount of element X is controlled between 20 and 300 ppm, the performance of the heteropolyacid-doped modified cathode precursor is better. If the doping amount of element X is too large, the discharge capacity is reduced; if the doping amount of element X is too small, the cycle performance is reduced.

[0080] A comparison of Examples 1 and 9-10 shows that the heating reaction temperature affects the performance of the heteropolyacid-doped modified cathode precursor during the preparation process of the present invention. Controlling the heating reaction temperature between 40 and 90°C results in a better performance of the heteropolyacid-doped modified cathode precursor. If the heating reaction temperature is too high, the doping amount is too large, which leads to a decrease in discharge capacity. If the heating reaction temperature is too low, the doping amount is too small, which leads to a decrease in cycle performance.

[0081] A comparison of Example 1 and Comparative Example 1 shows that, under the same Mo and P doping amounts, the heteropolyacid-doped modified Ni precursor proposed in this invention... 0.80 Co 0.10 Mn 0.10 The (OH)2 and mixed lithium calcination schemes are superior to direct physical mixing and calcination, with significant improvements in discharge capacity and cycle performance.

[0082] A comparison between Example 1 and Comparative Example 2 shows that the ternary precursor Ni 0.80 Co 0.10 Mn 0.10 After modification by heteropolyacid doping and lithium-mixing sintering, the 0.1C discharge capacity of (OH)2 increases significantly, and the cycle performance is greatly improved, with a cycle retention rate of over 95% after 100 cycles.

[0083] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A heteropolyacid-doped modified cathode precursor, characterized in that, The chemical formula of the heteropolyacid-doped modified cathode precursor is Ni. x Co y Y z (X a M b O c ) n (OH) 2-n Wherein, Y includes Mn and / or Al, 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1, 0.00001≤n≤0.001, X includes P and / or Si, M includes any one or at least two of Mo, W, V, Cr, Nb or Ta, and a:b:c=1:(6~18):(18~62); The doping amount of element M in the heteropolyacid-doped modified cathode precursor is 60~18000ppm, and the doping amount of element X in the heteropolyacid-doped modified cathode precursor is 10~1000ppm. The heteropolyacid-doped modified cathode precursor was prepared by the following method: A heteropolyacid solution is obtained by mixing the heteropolyacid with a solvent. The cathode precursor is mixed with a heteropolyacid solution and then heated to obtain the heteropolyacid-doped modified cathode precursor.

2. The heteropolyacid-doped modified cathode precursor as described in claim 1, characterized in that, The doping amount of element M in the heteropolyacid-doped modified cathode precursor is 1000~10000ppm.

3. The heteropolyacid-doped modified cathode precursor as described in claim 1, characterized in that, The doping amount of X in the heteropolyacid-doped modified cathode precursor is 20~300ppm.

4. A method for preparing a heteropolyacid-doped modified cathode precursor as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: A heteropolyacid solution is obtained by mixing the heteropolyacid with a solvent. The cathode precursor is mixed with a heteropolyacid solution and then heated to obtain the heteropolyacid-doped modified cathode precursor.

5. The preparation method according to claim 4, characterized in that, The heteropolyacids include any one or a combination of at least two of phosphomolybdic acid, phosphotungstic acid, silicotungstic acid, or silicotomolybdic acid.

6. The preparation method according to claim 4, characterized in that, The solvent includes ultrapure water and / or deionized water.

7. The preparation method according to claim 4, characterized in that, The concentration of the heteropolyacid solution is 1~10 g / L.

8. The preparation method according to claim 4, characterized in that, The cathode precursor includes any one or a combination of at least two of the following: ternary nickel-cobalt-manganese precursor, binary nickel-manganese precursor, ternary nickel-cobalt-aluminum precursor, or lithium-rich manganese-based precursor.

9. The preparation method according to claim 4, characterized in that, The temperature of the heating reaction is 40~90℃.

10. The preparation method according to claim 4, characterized in that, The heating reaction time is 0.5 to 8 hours.

11. The preparation method according to claim 4, characterized in that, The stirring speed for the heating reaction is 100~500 rpm.

12. A modified cathode material, characterized in that, The modified cathode material is prepared by mixing and sintering the heteropolyacid-doped modified cathode precursor as described in any one of claims 1-3 with a lithium source.

13. A positive electrode plate, characterized in that, The positive electrode sheet comprises the modified positive electrode material as described in claim 12.

14. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode as described in claim 13.

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