Modified lithium-rich manganese-based positive electrode material, preparation method therefor, and use thereof

Abstract

Provided in the present application are a modified lithium-rich manganese-based positive electrode material, a preparation method therefor, and the use thereof. The preparation method comprises the following steps: (1) cocurrently injecting a mixed metal salt solution, a precipitant and a complexing agent into a base solution, and performing a primary coprecipitation reaction; (2) stopping injecting the mixed metal salt solution, cocurrently injecting a manganese salt solution, the precipitant and the complexing agent into the reaction solution, carrying out a secondary coprecipitation reaction, and performing low-temperature pre-sintering treatment on the obtained particles, so as to obtain a modified precursor; and (3) mixing the modified precursor with a lithium source, and performing sintering treatment to obtain the modified lithium-rich manganese-based positive electrode material. The present application can improve the structural stability of the interior of the material while ensuring a high specific surface area of the lithium-rich manganese-based positive electrode material. In addition, the spinel-phase manganese oxide can prevent performance deterioration of the material during charging and discharging processes.

Description

A modified lithium-rich manganese-based positive electrode material and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of lithium-ion batteries and relates to a modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof. Background Art

[0002] With the current hot topic of manganese-rich precursors, the application scope of lithium-ion batteries is becoming more and more extensive with the vigorous development of modern society and the continuous growth of demand. As the core material of lithium-ion batteries, the positive electrode material is one of the important factors for their performance and cycle life.

[0003] Lithium-rich manganese-based cathode materials are currently attracting much attention due to their low cost, low toxicity, and ease of preparation. However, issues such as cycle life and stability have become increasingly prominent, posing certain challenges to battery life and safety.

[0004] CN110970614A discloses a lithium-rich manganese-based positive electrode material, the tap density of which is 1.28 g / cm 3 , specific surface area 37.1m 2 / g; compared with the traditional use of lithium iron phosphate as the positive electrode material, its tap density is high, which increases the actual capacity of the positive electrode material, thereby increasing the overall energy density of the lithium-ion battery.

[0005] CN109742380A discloses a method for preparing a lithium-rich manganese-based positive electrode material. The method comprises mixing LiMnO4 and lithium acetate, dissolving them in water, and stirring to mix them evenly. Then, lithium nickel cobalt manganese oxide is added, slurried and stirred to mix evenly, and then spray-dried to obtain a mixture. The mixture is placed in a sagger and then calcined in a roller kiln. Air is blown into the kiln during the calcination process, and the material is cooled to a temperature of less than 60°C before being discharged. The cooled material is subjected to air flow crushing, followed by electromagnetic iron removal, and then sieved, passed through a 200-mesh sieve, and vacuum-packed to obtain the material.

[0006] High-surface-area lithium-manganese-rich batteries suffer from internal structural instability, impacting cycle life. The layered structure gradually transforms into a spinel structure, which gradually invades the interior during charge and discharge, further deteriorating the performance of the cathode material. Therefore, developing a novel cathode material preparation method that can improve the performance and cycle life of lithium-ion batteries is crucial.

[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 present application provides a modified lithium-rich manganese-based positive electrode material, a preparation method and an application thereof. The present application obtains a spinel phase structure by providing a manganese hydroxide coating layer on the surface of a lithium-rich manganese-based precursor and then performing low-temperature sintering. This can ensure the high specific surface area of ​​the lithium-rich manganese-based positive electrode material while improving the structural stability inside the material. The spinel phase manganese oxide can prevent the performance of the material from deteriorating during the charge and discharge process.

[0010] In a first aspect, the present application provides a method for preparing a modified lithium-rich manganese-based positive electrode material, the preparation method comprising the following steps:

[0011] (1) injecting a mixed metal salt solution, a precipitant, and a complexing agent into the bottom liquid in parallel to perform a one-step coprecipitation reaction;

[0012] (2) stopping the injection of the mixed metal salt solution, and injecting the manganese salt solution, the precipitant, and the complexing agent into the reaction solution in parallel to perform a two-step co-precipitation reaction, and performing a low-temperature pre-calcination treatment on the obtained particles to obtain a modified precursor;

[0013] (3) Mixing the modified precursor and a lithium source, and sintering the mixture to obtain the modified lithium-rich manganese-based positive electrode material.

[0014] The present application pre-prepares a lithium-rich manganese-based precursor core by a conventional co-precipitation method, further co-precipitates on the surface of the core to form a manganese hydroxide surface coating layer, and forms a surface spinel structure of a lithium-rich manganese-based precursor structure by low-temperature pre-sintering. During the preparation process of the modified lithium-rich manganese-based precursor, a heterogeneous structure is formed on the surface, thereby enhancing the structural stability of the high specific surface area polycrystalline positive electrode material, and mass production is simple, and it can be shared with the existing ternary positive electrode material production line.

[0015] In one embodiment, the molar ratio of nickel, cobalt and manganese in the mixed metal salt solution of step (1) is Ni:Co:Mn=x:yc, x+y+c=1, 0.1 <x<0.5,0≤y<0.1,0.5<c<0.8。

[0016] In one embodiment, the total molar concentration of the metal elements in the mixed metal salt solution is 1.6 to 2.4 mol / L, for example, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L or 2.4 mol / L.

[0017] In one embodiment, the precipitating agent comprises an alkali solution.

[0018] In one embodiment, the concentration of the precipitant is 8 to 12 mol / L, for example, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L or 12 mol / L.

[0019] In one embodiment, the complexing agent comprises aqueous ammonia.

[0020] In one embodiment, the concentration of the complexing agent is 0.5 to 1.5 mol / L, for example, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L or 1.5 mol / L.

[0021] In one embodiment, the base solution includes a precipitant and a complexing agent.

[0022] In one embodiment, the pH of the base solution is 9 to 12, for example, 9, 9.5, 10, 11 or 12.

[0023] In one embodiment, the concentration of aqueous ammonia in the base solution is 12 to 14 g / L, for example, 12 g / L, 12.5 g / L, 13 g / L, 13.5 g / L or 14 g / L.

[0024] In one embodiment, the temperature of the one-step coprecipitation reaction in step (1) is 40-60°C, for example, 40°C, 45°C, 50°C, 55°C or 60°C.

[0025] In one embodiment, the stirring speed of the one-step coprecipitation reaction is 200-380 rpm, for example, 200 rpm, 250 rpm, 280 rpm, 300 rpm or 380 rpm.

[0026] In one embodiment, the endpoint of the one-step coprecipitation reaction is that the particle size D501 of the particles in the system is 6 to 18 μm, for example, 6 μm, 8 μm, 10 μm, 15 μm or 18 μm.

[0027] In one embodiment, the concentration of the manganese salt solution in step (2) is 1.5 to 2.5 mol / L, for example, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L or 2.5 mol / L.

[0028] In one embodiment, the stirring speed of the two-step co-precipitation reaction in step (2) is 200-380 rpm, for example, 200 rpm, 250 rpm, 280 rpm, 300 rpm or 380 rpm.

[0029] In one embodiment, the endpoint of the two-step coprecipitation reaction is that the particle size of the particles in the system is D502-D501=0.02-2 μm, for example: 0.02 μm, 0.25 μm, 1 μm, 1.5 μm or 2 μm.

[0030] In one embodiment, the temperature of the low-temperature pre-calcination treatment in step (2) is 100-300°C, for example, 100°C, 150°C, 200°C, 250°C or 300°C, etc., and can be optionally 120-200°C.

[0031] In one embodiment, the low-temperature pre-firing atmosphere includes air and / or oxygen.

[0032] In one embodiment, the low-temperature pre-firing time is 10 to 20 hours, for example, 10 hours, 12 hours, 15 hours, 18 hours or 20 hours.

[0033] In one embodiment, the lithium source in step (3) includes lithium carbonate and / or lithium hydroxide.

[0034] In one embodiment, the sintering temperature is 800-900°C, for example, 800°C, 820°C, 850°C, 880°C or 900°C.

[0035] In one embodiment, the sintering treatment time is 10 to 15 hours, for example, 10 hours, 11 hours, 12 hours, 14 hours or 15 hours.

[0036] In a second aspect, the present application provides a modified lithium-rich manganese-based positive electrode material, which is prepared by the method described in the first aspect.

[0037] In a third aspect, the present application provides a positive electrode plate, which comprises the modified lithium-rich manganese-based positive electrode material as described in the second aspect.

[0038] In a fourth aspect, the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises the positive electrode sheet as described in the third aspect.

[0039] Compared with the related art, this application has the following beneficial effects:

[0040] (1) The present application provides a manganese hydroxide coating layer on the surface of a lithium-rich manganese-based precursor and then performs low-temperature sintering to obtain a spinel phase structure. This can ensure a high specific surface area of ​​the lithium-rich manganese-based positive electrode material while improving the structural stability of the material. The spinel phase manganese oxide can prevent the performance of the material from deteriorating during the charge and discharge process.

[0041] (2) The modified lithium-rich manganese-based positive electrode material described in this application has a specific capacity of more than 237.85 mAh / g at 4.5 V, an initial efficiency of more than 87.6%, and a capacity retention rate of more than 80% with a cycle number of more than 1792 cycles.

[0042] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] 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.

[0044] FIG1 is an SEM image of the modified lithium-rich manganese-based precursor prepared in Example 1 of the present application.

[0045] FIG2 is an SEM image of the modified lithium-rich manganese-based precursor prepared in Example 2 of the present application. DETAILED DESCRIPTION

[0046] 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.

[0047] Example 1

[0048] This embodiment provides a modified lithium-rich manganese-based positive electrode material. The preparation method of the modified lithium-rich manganese-based positive electrode material is as follows:

[0049] (1) preparing a sulfate solution A containing nickel ions and manganese ions and having a total ion concentration of 2 mol / L, wherein the molar ratio of nickel ions to manganese ions is 30:70, using industrial liquid caustic soda with a concentration of 10 mol / L as a precipitant solution B, using 1 mol / L ammonia water as a complexing agent solution C, preparing a bottom liquid E containing the precipitant solution and the complexing agent solution in a reactor, wherein the pH of the bottom liquid E is controlled at 9-12, the ammonia water concentration of the bottom liquid E is 13 g / L, nitrogen is introduced as a protective gas, and the mixed salt solution A, the precipitant solution B, and the complexing agent solution C are co-flow-injected into the bottom liquid E, and a co-precipitation reaction is carried out by stirring at 300 rpm to obtain seed particles with a D50 of 11.8 μm;

[0050] (2) preparing a sulfate solution D containing manganese ions and having a total ion concentration of 2 mol / L, pausing the introduction of solution A, and injecting the salt solution D, the precipitant solution B, and the complexing agent solution C into the reaction solution in parallel, stirring at 300 rpm for a coprecipitation reaction to obtain spherical particles with a D50 of 12 μm. The washed spherical particles were pre-calcined at 150° C. for 15 h to obtain a modified precursor. The SEM image of the modified precursor is shown in FIG1 ;

[0051] (3) The modified precursor was mixed with lithium carbonate according to Li / M=1.2:1, and calcined at 850°C in an air atmosphere for 12 hours to obtain the modified lithium-rich manganese-based positive electrode material.

[0052] Example 2

[0053] This embodiment provides a modified lithium-rich manganese-based positive electrode material. The preparation method of the modified lithium-rich manganese-based positive electrode material is as follows:

[0054] (1) preparing a sulfate solution A containing nickel ions and manganese ions and having a total ion concentration of 1.6 mol / L, wherein the molar ratio of nickel ions to manganese ions is 40:60, using industrial liquid caustic soda with a concentration of 8 mol / L as a precipitant solution B, using 0.5 mol / L ammonia water as a complexing agent solution C, preparing a bottom liquid E containing the precipitant solution and the complexing agent solution in a reactor, wherein the pH of the bottom liquid E is controlled at 9-12, the ammonia water concentration of the bottom liquid E is 12 g / L, nitrogen is introduced as a protective gas, and the mixed salt solution A, the precipitant solution B, and the complexing agent solution C are co-flow-injected into the bottom liquid E, and the mixture is stirred at 200 rpm for a coprecipitation reaction to obtain seed particles with a D50 of 8 μm;

[0055] (2) preparing a sulfate solution D containing manganese ions and having a total ion concentration of 2 mol / L, pausing the introduction of solution A, and injecting the salt solution D, the precipitant solution B, and the complexing agent solution C into the reaction solution in parallel, stirring at 300 rpm for a coprecipitation reaction to obtain spherical particles with a D50 of 8.5 μm. The washed spherical particles were pre-calcined at 100° C. for 20 h to obtain a modified precursor. The SEM image of the modified precursor is shown in FIG2 ;

[0056] (3) The modified precursor was mixed with lithium carbonate according to Li / M=1.2:1, and calcined at 800°C in an air atmosphere for 15 hours to obtain the modified lithium-rich manganese-based positive electrode material.

[0057] Example 3

[0058] This embodiment provides a modified lithium-rich manganese-based positive electrode material. The preparation method of the modified lithium-rich manganese-based positive electrode material is as follows:

[0059] (1) preparing a sulfate solution A containing nickel ions and manganese ions and having a total ion concentration of 2.4 mol / L, wherein the molar ratio of nickel ions to manganese ions is 30:70, using industrial liquid caustic soda with a concentration of 8 mol / L as a precipitant solution B, using 0.5 mol / L ammonia water as a complexing agent solution C, preparing a bottom liquid E containing the precipitant solution and the complexing agent solution in a reactor, wherein the pH of the bottom liquid E is controlled at 9-12, the ammonia water concentration of the bottom liquid E is 14 g / L, nitrogen is introduced as a protective gas, and the mixed salt solution A, the precipitant solution B, and the complexing agent solution C are co-flow-injected into the bottom liquid E, and the mixture is stirred at 380 rpm for a coprecipitation reaction to obtain seed particles with a D50 of 10 μm;

[0060] (2) preparing a sulfate solution D containing manganese ions and having a total ion concentration of 2.5 mol / L, pausing the introduction of solution A, and injecting the salt solution D, the precipitant solution B, and the complexing agent solution C into the reaction solution in parallel, stirring at 380 rpm for a coprecipitation reaction to obtain spherical particles with a D50 of 10.25 μm. The washed spherical particles were pre-calcined at 300°C for 10 h to obtain a modified precursor;

[0061] (3) The modified precursor was mixed with lithium carbonate according to Li / M=1.2:1, and calcined at 900°C in an air atmosphere for 10 hours to obtain the modified lithium-rich manganese-based positive electrode material.

[0062] Example 4

[0063] The only difference between this embodiment and embodiment 1 is that the concentration of manganese in solution D is 1 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0064] Example 5

[0065] The only difference between this embodiment and embodiment 1 is that the concentration of manganese in solution D is 3 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0066] Example 6

[0067] The only difference between this embodiment and embodiment 1 is that the low-temperature pre-firing temperature is 100° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0068] Example 7

[0069] The only difference between this embodiment and embodiment 1 is that the low-temperature pre-firing temperature is 300° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0070] Comparative Example 1

[0071] The only difference between this comparative example and Example 1 is that solution D is not added, and other conditions and parameters are exactly the same as those in Example 1.

[0072] Comparative Example 2

[0073] The only difference between this comparative example and Example 1 is that no low-temperature pre-firing treatment is performed, and other conditions and parameters are exactly the same as those in Example 1.

[0074] Performance testing:

[0075] The positive electrode material, acetylene black, and polyvinylidene fluoride were added to N-methyl-2-pyridine in a mass ratio of 8:1:1 to prepare a solution. The solution was then evenly applied to aluminum foil, dried, and punched into a thin sheet. The battery electrode, elemental sodium sheet, glass fiber separator, electrolyte spacer, spring, and battery case were assembled into a button cell in an Ar glove box. The battery performance was tested, and the test results are shown in Table 1:

[0076] Table 1

[0077] As can be seen from Table 1, from Examples 1-3, the specific capacity of the modified lithium-rich manganese-based positive electrode material described in this application at 4.5V can reach more than 237.85mAh / g, the first efficiency can reach more than 87.6%, and the number of cycles with a capacity retention rate of more than 80% can reach more than 1792 cycles.

[0078] By comparing Example 1 with Examples 4-5, it can be seen that in the preparation process of the modified lithium-rich manganese-based positive electrode material described in the present application, the concentration of the manganese salt solution used will affect its performance. The manganese salt concentration is controlled at 1.5-2.5 mol / L, and the performance of the modified lithium-rich manganese-based positive electrode material is better. If the manganese salt concentration is too low, the coating layer is too thin. If the manganese salt concentration is too high, the reaction process parameters fluctuate more, which makes it easy to produce small particles; and the coating layer is too thick, which affects the performance of the positive electrode material.

[0079] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation process of the modified lithium-rich manganese-based positive electrode material described in the present application, the temperature of low-temperature pre-firing will affect its performance. By controlling the temperature of low-temperature pre-firing at 120-200°C, the performance of the modified lithium-rich manganese-based positive electrode material is better. If the temperature of low-temperature pre-firing is too low, the contact time with the oxidizing gas is too long, resulting in an excessively thick coating layer. If the temperature of low-temperature pre-firing is too high, the precursor structure is easily destroyed, resulting in poor positive electrode performance.

[0080] From the comparison between Example 1 and Comparative Example 1, it can be seen that the present application coats a manganese hydroxide coating layer on the surface of the lithium-rich manganese-based precursor. The spinel coating layer can inhibit the structural transformation of the lithium-rich manganese positive electrode material during the cycle, resulting in faster performance degradation.

[0081] From the comparison between Example 1 and Comparative Example 2, it can be seen that the present application can form a layer of surface spinel structure on the surface of the precursor through low-temperature pre-firing, thereby enhancing the structural stability of the high specific surface area polycrystalline positive electrode material.

[0082] 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 method for preparing a modified lithium-rich manganese-based positive electrode material, comprising the following steps: (1) injecting a mixed metal salt solution, a precipitant and a complexing agent into a bottom liquid in parallel to perform a one-step coprecipitation reaction; (2) stopping the injection of the mixed metal salt solution, injecting the manganese salt solution, the precipitant and the complexing agent into the reaction solution in parallel to perform a two-step co-precipitation reaction, and performing a low-temperature pre-calcination treatment on the obtained particles to obtain a modified precursor; (3) The modified precursor and a lithium source are mixed and sintered to obtain the modified lithium-rich manganese-based positive electrode material.

2. The preparation method according to claim 1, wherein The molar ratio of nickel, cobalt and manganese in the mixed metal salt solution of step (1) is Ni:Co:Mn=x:yc, x+y+c=1,0.1 <x<0.5,0≤y<0.1,0.5<c<0.8; Optionally, the total molar concentration of the metal elements in the mixed metal salt solution is 1.6 to 2.4 mol / L; Optionally, the precipitant comprises alkali solution; Optionally, the concentration of the precipitant is 8 to 12 mol / L; Optionally, the complexing agent includes aqueous ammonia; Optionally, the concentration of the complexing agent is 0.5 to 1.5 mol / L; Optionally, the base solution includes a precipitant and a complexing agent; Optionally, the pH of the base solution is 9 to 12; Optionally, the concentration of ammonia water in the base solution is 12-14 g / L.

3. The preparation method according to claim 1 or 2, wherein: The temperature of the one-step coprecipitation reaction in step (1) is 40-60° C. Optionally, the stirring speed of the one-step coprecipitation reaction is 200 to 380 rpm; Optionally, the endpoint of the one-step coprecipitation reaction is that the particle size D501 of particles in the system is 6 to 18 μm.

4. The preparation method according to any one of claims 1 to 3, wherein The concentration of the manganese salt solution in step (2) is 1.5 to 2.5 mol / L.

5. The preparation method according to any one of claims 1 to 4, wherein: The stirring speed of the two-step coprecipitation reaction in step (2) is 200-380 rpm; Optionally, the endpoint of the two-step coprecipitation reaction is that the particle size of the particles in the system is D502-D501=0.02-2 μm.

6. The preparation method according to any one of claims 1 to 5, wherein: The temperature of the low-temperature pre-sintering treatment in step (2) is 100-300° C., and can be optionally 120-200° C.; Optionally, the atmosphere of the low-temperature pre-firing includes air and / or oxygen; Optionally, the low-temperature pre-burning time is 10 to 20 hours.

7. The preparation method according to any one of claims 1 to 6, wherein: The lithium source in step (3) includes lithium carbonate and / or lithium hydroxide; Optionally, the sintering temperature is 800-900°C; Optionally, the sintering treatment time is 10 to 15 hours.

8. A modified lithium-rich manganese-based positive electrode material, wherein: The modified lithium-rich manganese-based positive electrode material is prepared by the method as described in any one of claims 1 to 7.

9. A positive electrode sheet, wherein: The positive electrode plate comprises the modified lithium-rich manganese-based positive electrode material as claimed in claim 8.

10. A lithium ion battery, wherein: The lithium-ion battery comprises the positive electrode sheet as claimed in claim 9.

Images