Doped modified nickel-cobalt-manganese-sodium positive electrode material, and preparation method therefor and use thereof

Abstract

A doped modified nickel-cobalt-manganese-sodium positive electrode material, and a preparation method therefor and a use thereof. The preparation method comprises the following steps: (1) mixing a doped metal M salt with a complexing agent solution to obtain an M- complexing solution; (2) injecting a nickel-cobalt-manganese mixed salt solution, a precipitant solution, ammonia and the M- complexing solution into a base solution in a concurrent flow mode, and carrying out coprecipitation reaction to obtain a precursor; and (3) mixing the precursor with a sodium source, and carrying out sintering treatment to obtain a doped modified nickel-cobalt-manganese-sodium positive electrode material. Compared with doping during sintering, directly doping the metal element in the precursor coprecipitation stage can simplify the preparation process of the positive electrode material, and can also reduce the cost consumption in material preparation.

Description

A doped modified nickel-cobalt-manganese-sodium cathode material and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of sodium ion batteries and relates to a doped and modified nickel-cobalt-manganese-sodium cathode material and a preparation method and application thereof. Background Art

[0002] Due to their abundant sodium resources, environmental friendliness, and low cost, sodium-ion batteries (SIBs) are considered to have the greatest potential for large-scale energy storage and as a replacement for batteries in lightweight electric vehicles. To date, a number of materials have been demonstrated as potential cathode materials for SIBs, including sodium-ion transition metal layered oxides, polyanionic compounds, and Bruce's blue compounds.

[0003] Nickel-cobalt-manganese ternary layered cathode materials have been extensively studied for their excellent sodium ion storage capacity. Research has found that while this P2-type layered material can release a high capacity, it undergoes irreversible phase transitions during the charge and discharge process, causing a decrease in the cathode material's discharge specific capacity. Furthermore, due to the large diameter of sodium ions, their insertion and removal processes can disrupt the material's surface lattice structure, undermining the stability of the electrode-electrolyte interface.

[0004] CN116332244A discloses a nickel-iron-manganese-based sodium ion battery positive electrode material and a preparation method thereof, which are used to solve the problem of poor cycle stability of existing nickel-iron-manganese-based positive electrode materials; the preparation method forms a magnesium-doped nickel-iron-manganese-based precursor by doping magnesium acetate into the nickel-iron-manganese-based precursor.

[0005] CN113851652A discloses a modified cobalt-free positive electrode material for a sodium ion battery, a preparation method thereof, and a sodium ion battery. The preparation method comprises: performing a first sintering treatment on a sodium source, a nickel source, a manganese source, and a dopant to obtain a first sintered product; and performing a second sintering treatment on the first sintered product and a coating agent to obtain a modified cobalt-free positive electrode material for a sodium ion battery.

[0006] The above-mentioned solution can improve the structure and electrochemical stability of the P2 phase material to a certain extent by doping with metal elements. However, traditional doping elements are introduced as additives during the later sintering process of the cathode material. Due to the high-temperature permeability of the doping elements, extremely high temperatures are required to diffuse into the cathode material, which greatly increases sintering energy consumption.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of this application is to provide a doped modified nickel-cobalt-manganese-sodium cathode material, a preparation method and application thereof. This application directly dopes metal elements in the precursor co-precipitation stage. Compared with doping during the sintering process, it can not only simplify the preparation process of the cathode material, but also reduce the cost consumption in material preparation.

[0010] To achieve this goal, this application adopts the following technical solutions:

[0011] In a first aspect, the present application provides a method for preparing a doped and modified nickel-cobalt-manganese-sodium cathode material, the preparation method comprising the following steps:

[0012] (1) mixing a doped metal M salt with a complexing agent solution to obtain an M-complexing solution;

[0013] (2) injecting nickel-cobalt-manganese mixed salt solution, precipitant solution, ammonia water and M-complex solution into the bottom liquid in parallel to carry out coprecipitation reaction to obtain a precursor;

[0014] (3) The precursor is mixed with a sodium source, and the mixture is sintered to obtain the doped modified nickel-cobalt-manganese-sodium cathode material.

[0015] In the process of preparing the nickel-cobalt-manganese ternary precursor by chemical coprecipitation, the present application adds doping elements, and through the control process, the doping elements are pre-complexed with the complexing agent to reduce their precipitation rate, ensuring that the doping elements are evenly distributed in the precursor bulk phase, thereby obtaining a sodium-based positive electrode material uniformly doped with metal elements. The introduction of doping elements can make the charge and discharge curve smoother and improve the capacity retention rate. The presence of doping metals can effectively inhibit the P2-O2 phase transition and maintain the P2 stacking structure of the triangular prism during the cycle, thereby greatly improving the structural stability of the positive electrode material and thus improving the cycle performance.

[0016] In one embodiment, the doping metal M salt in step (1) includes any one of Cr salt, Ti salt, V salt, Mo salt, Cu salt, W salt or Sn salt, or a combination of at least two thereof.

[0017] In one embodiment, the complexing agent solution includes oxalic acid solution and / or citric acid solution.

[0018] In one embodiment, the concentration of the metal M salt doped in the M-complex solution in step (1) is 0.1 to 0.3 mol / L, for example, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L or 0.3 mol / L.

[0019] In one embodiment, the total concentration of metal elements in the nickel-cobalt-manganese mixed salt solution in step (2) is 0.5 to 5 mol / L, for example, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L or 5 mol / L.

[0020] In one embodiment, the precipitant solution comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0021] In one embodiment, the concentration of the precipitant solution is 2 to 15 mol / L, for example, 2 mol / L, 5 mol / L, 8 mol / L, 10 mol / L or 15 mol / L.

[0022] In one embodiment, the concentration of the ammonia water is 4 to 12 mol / L, for example, 4 mol / L, 6 mol / L, 8 mol / L, 10 mol / L or 12 mol / L.

[0023] In one embodiment, the feeding rate of the nickel-cobalt-manganese mixed salt solution in step (2) is 3 to 100 L / h, for example, 3 L / h, 8 L / h, 20 L / h, 50 L / h or 100 L / h.

[0024] In one embodiment, the feed rate of the precipitant solution is 1 to 20 L / h, for example, 1 L / h, 5 L / h, 10 L / h, 15 L / h or 20 L / h.

[0025] In one embodiment, the feed rate of the ammonia solution is 0.5 to 5 L / h, for example, 0.5 L / h, 1 L / h, 2 L / h, 4 L / h or 5 L / h.

[0026] In one embodiment, the feeding rate of the M-complexing liquid is 1 to 10 L / h, for example, 1 L / h, 2 L / h, 5 L / h, 8 L / h or 10 L / h.

[0027] In one embodiment, the temperature of the coprecipitation reaction in step (2) is 50-80°C, for example, 50°C, 55°C, 60°C, 70°C or 80°C.

[0028] In one embodiment, the pH of the coprecipitation reaction is 9 to 13, for example, 9, 10, 11, 12 or 13.

[0029] In one embodiment, the coprecipitation is followed by washing and drying.

[0030] In one embodiment, the washing treatment includes alkali washing followed by water washing.

[0031] In one embodiment, the median particle size D50 of the precursor is 3 to 15 μm, for example, 3 μm, 5 μm, 8 μm, 10 μm or 15 μm.

[0032] In one embodiment, the temperature of the sintering treatment in step (3) is 600-1200°C, for example, 600°C, 700°C, 800°C, 1000°C or 1200°C.

[0033] In one embodiment, the sintering treatment time is 8-24°C, for example, 8°C, 10°C, 15°C, 20°C or 24°C.

[0034] In a second aspect, the present application provides a doped and modified nickel-cobalt-manganese-sodium cathode material, which is prepared by the method described in the first aspect.

[0035] In a third aspect, the present application provides a positive electrode plate, which comprises the doped and modified nickel-cobalt-manganese-sodium positive electrode material as described in the second aspect.

[0036] In a fourth aspect, the present application provides a sodium ion battery, which comprises the positive electrode sheet as described in the third aspect.

[0037] Compared with the prior art, this application has the following beneficial effects:

[0038] (1) The present application directly dopes metal elements in the precursor co-precipitation stage. Compared with doping during the sintering process, this can not only simplify the preparation process of the positive electrode material, but also reduce the cost consumption in material preparation. Doping with metal elements can make the charge and discharge curve smoother and improve the capacity retention rate.

[0039] (2) The modified nickel-cobalt-manganese-sodium cathode material described in this application can produce a battery with an initial discharge capacity of more than 124.4 mAh / g at 0.1C, a capacity retention rate of more than 91.9% after 100 cycles, and a capacity retention rate of more than 87.4% after 100 cycles at 1C. The electrochemical performance of the modified nickel-cobalt-manganese-sodium cathode material is improved differently with the addition of different doping elements. The titanium-doped cathode has high cycle stability and a high capacity retention rate at high rates. The tin-doped cathode material has a high initial discharge capacity. The molybdenum-doped cathode also exhibits good electrochemical performance.

[0040] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0042] FIG1 is a SEM image of the doped and modified nickel-cobalt-manganese-sodium cathode material described in Example 1. DETAILED DESCRIPTION

[0043] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0044] Example 1

[0045] This embodiment provides a doped and modified nickel-cobalt-manganese-sodium cathode material. The preparation method of the doped and modified nickel-cobalt-manganese-sodium cathode material is as follows:

[0046] (1) Add titanyl sulfate to a 0.2 mol / L oxalic acid solution to prepare a 0.3 mol / L Ti-oxalic acid mixed solution for later use;

[0047] (2) nickel sulfate, cobalt sulfate, and manganese sulfate solutions are mixed in a molar ratio of 2:2:6 to obtain a nickel-cobalt-manganese mixed salt solution with a total metal ion concentration of 0.5 mol / L. The nickel-cobalt-manganese mixed salt solution, 5 mol / L sodium hydroxide solution, 6 mol / L ammonia water, and Ti-oxalic acid mixed solution are added to a reactor for reaction. The feed rate of the nickel-cobalt-manganese mixed solution is 3 L / h, the feed rate of the NaOH solution is 1 L / h, the feed rate of the ammonia solution is 0.5 L / h, and the feed rate of the Ti-oxalic acid mixed solution is 1 L / h. A coprecipitation reaction is carried out under a N2 atmosphere at a reaction temperature of 50°C and a pH value of 10 to 11. The reaction is stopped after about 50 hours and the average particle size reaches 5 μm. After the reaction is completed, the product of the coprecipitation reaction is centrifuged and washed with alkali solution and water in sequence to obtain the precursor;

[0048] (3) Sodium carbonate and precursor powder are weighed and mixed evenly according to a molar ratio of Na / M=1.03:1, calcined at 600°C for 8h, and ground and sieved to obtain the doped modified nickel-cobalt-manganese-sodium cathode material.

[0049] The SEM image of the doped modified nickel-cobalt-manganese-sodium cathode material is shown in FIG1 .

[0050] Example 2

[0051] This embodiment provides a doped and modified nickel-cobalt-manganese-sodium cathode material. The preparation method of the doped and modified nickel-cobalt-manganese-sodium cathode material is as follows:

[0052] (1) Add tin sulfate to 0.02 mol / L citric acid solution to prepare a 0.3 mol / L Sn-citric acid mixed solution for later use;

[0053] (2) nickel sulfate, cobalt sulfate, and manganese sulfate solutions are mixed in a molar ratio of 1:2:7 to obtain a nickel-cobalt-manganese mixed salt solution with a total metal ion concentration of 5 mol / L, and the nickel-cobalt-manganese mixed salt solution, 15 mol / L sodium hydroxide solution, 12 mol / L ammonia water, and Sn-citric acid mixed solution are added to a reactor for reaction. The feed rate of the nickel-cobalt-manganese mixed solution is 100 L / h, the feed rate of the NaOH solution is 20 L / h, the feed rate of the ammonia solution is 5 L / h, and the feed rate of the Ti-oxalic acid mixed solution is 1.5 L / h. A coprecipitation reaction is carried out under a N2 atmosphere at a reaction temperature of 50°C and a pH value of 11 to 12. The reaction is stopped after about 100 hours when the average particle size reaches 15 μm. After the reaction is completed, the product of the coprecipitation reaction is centrifuged and washed with alkali solution and water in sequence to obtain the precursor;

[0054] (3) Sodium carbonate and precursor powder are weighed and mixed evenly according to a molar ratio of Na / M=1.03:1, calcined at 1200°C for 24h, and ground and sieved to obtain the doped modified nickel-cobalt-manganese-sodium cathode material.

[0055] Example 3

[0056] This embodiment provides a doped and modified nickel-cobalt-manganese-sodium cathode material. The preparation method of the doped and modified nickel-cobalt-manganese-sodium cathode material is as follows:

[0057] (1) Add molybdenum sulfate to 0.1 mol / L oxalic acid solution to prepare a 0.3 mol / L Mo-oxalic acid mixed solution for standby use;

[0058] (2) nickel sulfate, cobalt sulfate, and manganese sulfate solutions are mixed in a molar ratio of 2:3:5 to obtain a nickel-cobalt-manganese mixed salt solution with a total metal ion concentration of 2 mol / L, and the nickel-cobalt-manganese mixed salt solution, 6 mol / L sodium hydroxide solution, 6 mol / L ammonia water, and Mo-oxalic acid mixed solution are added to a reactor for reaction. The feed rate of the nickel-cobalt-manganese mixed solution is 50 L / h, the feed rate of the NaOH solution is 50 L / h, the feed rate of the ammonia water solution is 3 L / h, and the feed rate of the Ti-oxalic acid mixed solution is 10 L / h. A coprecipitation reaction is carried out under a N2 atmosphere at a reaction temperature of 50°C and a pH value of 9.5 to 10. The reaction is continued for about 80 hours until the average particle size reaches 8 μm, and the reaction is stopped. After the reaction is completed, the product of the coprecipitation reaction is centrifuged and washed with alkali solution and water in sequence to obtain the precursor;

[0059] (3) Sodium carbonate and precursor powder are weighed and mixed evenly according to a molar ratio of Na / M=1.03:1, calcined at 1000°C for 20 hours, and ground and sieved to obtain the doped modified nickel-cobalt-manganese-sodium cathode material.

[0060] Example 4

[0061] The only difference between this embodiment and embodiment 1 is that the concentration of the metal Ti salt doped in the Ti-oxalic acid solution (ie, the metal M salt doped in the M-complex solution) is 0.05 mol / L.

[0062] Example 5

[0063] The only difference between this embodiment and embodiment 1 is that the concentration of the metal Ti salt doped in the Ti-oxalic acid solution (ie, the metal M salt doped in the M-complex solution) is 0.5 mol / L.

[0064] Comparative Example 1

[0065] The only difference between this comparative example and Example 1 is that no titanium salt is added, and other conditions and parameters are exactly the same as those in Example 1.

[0066] Comparative Example 2

[0067] The only difference between this comparative example and Example 1 is that the doping metal salt is directly mixed with the nickel-cobalt-manganese salt solution. Other conditions and parameters are exactly the same as those in Example 1.

[0068] Comparative Example 3

[0069] The only difference between this comparative example and Example 1 is that the doping metal salt solution is fed separately, and the other conditions and parameters are exactly the same as those in Example 1.

[0070] Performance testing:

[0071] The sodium ion battery positive electrode material obtained in the above examples and comparative examples was mixed with conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1 to prepare a slurry, which was then coated on aluminum foil to form a positive electrode sheet; the prepared positive electrode sheet and the sodium metal sheet were assembled into a sodium ion button battery, wherein the electrolyte was obtained by dissolving sodium perchlorate with a concentration of 1 mol / L in polycarbonate (PC) / fluoroethylene carbonate (FEC) (mass ratio 97:3); after the button battery assembly was completed, it was left to stand for 2 hours, and the capacity and charge and discharge cycle tests were carried out as follows: the charge and discharge voltage range was 2.5-4.05V, the cycle rate was 0.1C-1C, and the rated gram capacity was 125mAh / g. The test results are shown in Table 1:

[0072] Table 1

[0073] As can be seen from Table 1, from Examples 1-3, the 0.1C initial discharge specific capacity of the battery made of the modified nickel-cobalt-manganese-sodium cathode material described in the present application can reach more than 124.4mAh / g, the capacity retention rate can reach more than 91.9% after 100 cycles, and the capacity retention rate can reach more than 87.4% after 100 cycles at 1C. The performance of the modified nickel-cobalt-manganese-sodium cathode material is improved differently with the different doping elements. The titanium-doped cathode has high cycle stability and a higher capacity retention rate at high rates. The tin-doped cathode material has a high initial discharge capacity. The molybdenum-doped cathode also exhibits good electrochemical properties.

[0074] By comparison of Example 1 and Example 4-5, it can be seen that during the preparation process of the doped modified nickel-cobalt-manganese sodium cathode material described in the present application, the concentration of the doped metal M salt in the M-complex solution will affect its performance. The concentration of the doped metal M salt in the M-complex solution is controlled at 0.1 to 0.3 mol / L, and the performance of the doped modified nickel-cobalt-manganese sodium cathode material is better. If the concentration of the doped metal M salt in the M-complex solution is too high, the discharge specific capacity will be reduced and the electrochemical performance will deteriorate because the doping element does not provide capacity; if the concentration of the doped metal M salt in the M-complex solution is too low, the improvement of the material by the doping element is limited, and the cycle performance is poor.

[0075] By comparing Example 1 with Comparative Examples 1-3, it can be seen that the present application reduces its precipitation rate by pre-complexing the doping element with a complexing agent through a controlled process, ensuring that the doping element is evenly distributed in the precursor bulk phase, thereby producing a sodium cathode material uniformly doped with metal elements. The introduction of doping elements can make the charge and discharge curve smoother and improve the capacity retention rate. The presence of the doping metal can effectively inhibit the P2-O2 phase transition and maintain the P2 stacking structure of the triangular prism during the cycle, thereby greatly improving the structural stability of the positive electrode material and thus improving the cycle performance.

[0076] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A preparation method of a doped and modified sodium nickel cobalt manganese oxide cathode material, comprising the following steps: (1) Mixing a doped metal M salt with a complexing agent solution to obtain an M-complexing solution; (2) Injecting a nickel cobalt manganese mixed salt solution, a precipitant solution, ammonia water, and the M-complexing solution into a bottom solution in a co-current manner to carry out a co-precipitation reaction to obtain a precursor; (3) Mixing the precursor with a sodium source and performing a sintering treatment to obtain the doped and modified sodium nickel cobalt manganese oxide cathode material.

2. The preparation method according to claim 1, wherein the doped metal M salt in step (1) includes any one or a combination of at least two of Cr salt, Ti salt, V salt, Mo salt, Cu salt, W salt, or Sn salt; optionally, the complexing agent solution includes an oxalic acid solution and / or a citric acid solution.

3. The preparation method according to claim 1 or 2, wherein the concentration of the doped metal M salt in the M-complexing solution in step (1) is 0.1 - 0.3 mol / L.

4. The preparation method according to any one of claims 1 - 3, wherein the total concentration of metal elements in the nickel cobalt manganese mixed salt solution in step (2) is 0.5 - 5 mol / L; optionally, the precipitant solution includes a sodium hydroxide solution and / or a potassium hydroxide solution; optionally, the concentration of the precipitant solution is 2 - 15 mol / L; optionally, the concentration of the ammonia water is 4 - 12 mol / L.

5. The preparation method according to any one of claims 1 - 4, wherein the feeding rate of the nickel cobalt manganese mixed salt solution in step (2) is 3 - 100 L / h; optionally, the feeding rate of the precipitant solution is 1 - 20 L / h; optionally, the feeding rate of the ammonia water is 0.5 - 5 L / h; optionally, the feeding rate of the M-complexing solution is 1 - 10 L / h.

6. The preparation method according to any one of claims 1 - 5, wherein the temperature of the co-precipitation reaction in step (2) is 50 - 80 °C; optionally, the pH of the co-precipitation reaction is 9 - 13; optionally, washing and drying treatments are performed after the co-precipitation; optionally, the washing treatment includes alkali washing followed by water washing; optionally, the median particle size D50 of the precursor is 3 - 15 μm.

7. The preparation method according to any one of claims 1 - 6, wherein the temperature of the sintering treatment in step (3) is 600 - 1200 °C; optionally, the time of the sintering treatment is 8 - 24 h.

8. A doped and modified sodium nickel cobalt manganese oxide cathode material prepared by the method according to any one of claims 1 - 7.

9. A positive electrode plate comprising the doped and modified sodium nickel cobalt manganese oxide cathode material according to claim 8.

10. A sodium ion battery comprising the positive electrode plate according to claim 9.

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