Preparation method of solvation structure surface of battery positive electrode material

Abstract

The invention discloses a preparation method of a solvation structure surface of a battery positive electrode material, and relates to the field of material surface modification.The method comprises the following steps that S1, a lithium ion battery material or a sodium ion battery material and a sodium dihydrogen bis (dimethoxyethoxy) aluminate solution are fully stirred to react in a container filled with argon; s2, after the reaction is finished, centrifugally washing the reacted solid by using a solvent; and S3, transferring the centrifugally washed material into a drying oven, drying in an inert gas atmosphere to remove the residual solvent, and finally obtaining the lithium ion or sodium ion battery material with the solvated structure surface, so that the problems of non-uniform coating, complex process and serious environmental pollution in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the field of material surface modification, and particularly to a preparation method for the solvation structure surface of a cathode material for a battery. Background Art

[0002] The cathode material for a lithium / sodium battery is one of the core components of a lithium / sodium battery. The properties of the cathode material for a lithium / sodium battery affect the lifespan, energy density, and rate performance of the lithium / sodium battery. Surface modification has been proven to be one of the effective means to improve the cathode material for a lithium / sodium battery. Although there are many surface modification methods that can be used for the cathode material for a lithium / sodium battery, most of these modification methods involve solid-phase mixing or high-temperature annealing, and the modification methods are complex and uneconomical. Therefore, developing a simple surface modification technology has great application potential.

[0003] Existing surface modification methods such as solid-phase mixing - high-temperature annealing and liquid-phase coating - high-temperature annealing generally have the disadvantages of uneven coating and poor consistency, and problems such as complex processes and high energy consumption brought about by high-temperature annealing. In addition, existing surface modification technologies introduce schemes such as coherent phase transformation, element doping, and compound coating layers, and the processes are relatively complex. Summary of the Invention

[0004] The present invention provides a preparation method for the solvation structure surface of a cathode material for a battery, which solves the problems of uneven coating, complex process, and large environmental pollution existing in the prior art.

[0005] To solve this technical problem, the present invention provides the following technical solutions:

[0006] A preparation method for the solvation structure surface of a cathode material for a battery, comprising the following steps:

[0007] S1. React a lithium-ion battery material or a sodium-ion battery material with a sodium bis(dimethoxyethoxy)aluminate solution in a container filled with argon under sufficient stirring;

[0008] S2. After the reaction, use a solvent to centrifuge and wash the reacted solid;

[0009] S3. Transfer the centrifuged and washed material to an oven and dry it in an inert gas atmosphere to remove the residual solvent, and finally obtain a lithium-ion or sodium-ion battery material with a solvation structure surface.

[0010] Preferably, the solvent of the sodium bis(dimethoxyethoxy)aluminate solution in step S1 is an oil-soluble solvent.

[0011] Preferably, the oil-soluble solvent includes a short-chain alkane substituted derivative selected from long-chain alkanes or benzene;

[0012] Preferably, the long-chain alkane is selected from octane or heptane; the short-chain alkane-substituted derivative of benzene is selected from any one of benzene, toluene or ethylbenzene.

[0013] Preferably, the stirring reaction time in step S1 is 1 - 3 h.

[0014] The length of the reaction time affects the thickness of the solvation structure on the surface of the cathode material, and the thickness of the solvation structure on the surface further affects the cycle stability of the cathode material.

[0015] Preferably, the mass fraction of sodium dihydrobis(dimethoxyethoxy) aluminate in the solution in step S1 is 10% - 50%.

[0016] Preferably, the lithium-ion battery material is selected from any one of lithium iron phosphate, lithium manganese iron phosphate, lithium-rich manganese-based cathode material, lithium cobaltate cathode material or ternary cathode material; the sodium-ion battery material is selected from any one of sodium iron sulfate, sodium iron phosphate, sodium iron pyrophosphate, sodium vanadium phosphate, Prussian blue or P2 / O3 phase layered sodium-ion cathode material.

[0017] Preferably, the liquid-solid ratio of the sodium dihydrobis(dimethoxyethoxy) aluminate solution to the lithium-ion battery material or the sodium-ion battery material in step S1 is 3 - 10.

[0018] Preferably, in step S2, the centrifugal rotation speed ≥ 2500 r / min, the centrifugal solid-liquid ratio is 2 - 10, the centrifugal time is 10 - 30 min, and the number of centrifugations is 3 - 5 times.

[0019] The rotation speed, centrifugal time, etc. during the centrifugal washing process affect the residual amount of sodium dihydrobis(dimethoxyethoxy) aluminate. Excessive residual amount of sodium dihydrobis(dimethoxyethoxy) aluminate will cause a decrease in the effective active substances of the cathode material.

[0020] Preferably, in step S3, the drying temperature is 120 - 180 °C, the drying time is 5 - 12 h, and the inert gas is argon.

[0021] The drying time affects the residual amount of solvent in the cathode material. Excessive residual amount of solvent will cause a decrease in the electrochemical performance of the cathode material. The drying temperature should be 120 - 180 °C and the drying time should be 5 - 12 h to ensure the complete removal of the solvent without causing energy waste.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] In this solution, first, a solvated structure is formed on the surface of the cathode material for lithium / sodium batteries through a one-step liquid-phase reaction between the cathode material and sodium bis(2-methoxyethoxy)aluminum hydride (commonly known as Red-Al). Finally, the modified cathode material is prepared through washing, centrifugation, and drying, and it exhibits excellent electrochemical performance, which can effectively improve the electrochemical performance such as the initial Coulombic efficiency, cycle stability, and rate performance of the cathode material for lithium / sodium batteries.

[0024] The modification method developed in this invention has a simple process flow, does not involve secondary high-temperature sintering, reduces the preparation cost, is environmentally friendly, has extremely high universality, and the technology has high application value.

[0025] The modification method developed in this invention is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not constitute a limitation to the embodiments of the present invention. In the drawings:

[0027] Figure 1 is a flow chart of the preparation method of this solution;

[0028] Figure 2 is a SEM comparison chart of Comparative Example 1 and Example 1;

[0029] Figure 3 is a TEM comparison chart of Comparative Example 1 and Example 1;

[0030] Figure 4 is a SEM comparison chart of Comparative Example 2 and Example 2;

[0031] Figure 5 is a TEM comparison chart of Comparative Example 2 and Example 2;

[0032] Figure 6 is a 1C cycle performance chart of Example 1 and Comparative Example 1;

[0033] Figure 7 is a 0.1C first-cycle curve chart of Example 1 and Comparative Example 1;

[0034] Figure 8 is a 1C cycle performance chart of Example 2 and Comparative Example 2;

[0035] Figure 9 is a 0.1C first-cycle curve chart of Example 2 and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0036] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with embodiments. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0037] The preparation method of the solvation structure surface of the cathode material of the battery in this solution includes the following steps:

[0038] S1. Stir and react the lithium-ion battery material or sodium-ion battery material with sodium bis(dimethoxyethoxy)aluminate solution in a container filled with argon.

[0039] In the illustrated embodiment, the lithium-ion battery material is selected from a lithium-rich manganese-based cathode material, a lithium cobalt oxide cathode material, or a ternary cathode material; other lithium-ion battery materials such as lithium iron phosphate, lithium manganese iron phosphate, or the sodium-ion battery materials such as sodium iron sulfate, sodium iron phosphate, sodium pyrophosphate iron, sodium vanadium phosphate, Prussian blue, or P2 / O3 phase layered sodium-ion cathode material can also be selected as the modification material; the solvent of the sodium bis(dimethoxyethoxy)aluminate solution is an oil-soluble solvent. In the illustrated embodiment, long-chain alkane heptane and short-chain alkane substituted derivative toluene are selected as the solvent; long-chain alkanes such as octane or short-chain alkane substituted derivatives such as benzene and ethylbenzene can also be selected; the mass fraction of sodium bis(dimethoxyethoxy)aluminate in the solution is 10%-50%, the stirring reaction time is 1-3 h; the liquid-solid ratio of the sodium bis(dimethoxyethoxy)aluminate solution to the lithium-ion battery material or sodium-ion battery material is 3-10.

[0040] S2. After the reaction is completed, use a solvent to centrifuge and wash the reacted solid; the centrifugation speed is ≥2500 revolutions / min, the centrifugation solid-liquid ratio is 2-10, the centrifugation time is 10-30 min, and the number of centrifugation times is 3-5 times.

[0041] S3. Transfer the centrifuged and washed material to an oven and dry it in an inert gas atmosphere to remove the residual solvent, and finally obtain a lithium-ion or sodium-ion battery material with a solvation structure surface; the drying temperature is 120-180 °C, the drying time is 5-12 h, and the inert gas is argon.

[0042] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as limiting the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0043] Example 1

[0044] As Figure 1As shown, a surface modification method for a lithium-rich manganese-based cathode material includes the following steps:

[0045] Immerse the lithium-rich oxide manganese-based cathode material in a 10% sodium bis(dimethoxyethoxy)aluminate toluene solution with a liquid-solid ratio of 5, and react at room temperature for 2 h.

[0046] Centrifuge and wash the reaction mixture with toluene solution 3 times at 5000 rpm with a centrifuge liquid-solid ratio of 2.5, and centrifuge for 10 min each time.

[0047] Put the centrifuged solid in an oven at 120 °C for 10 h to obtain the modified lithium-rich oxide manganese-based cathode material;

[0048] Use the prepared lithium-rich oxide manganese-based cathode material as the electrode material to assemble coin-type half-cells respectively: the modified lithium-rich oxide manganese-based cathode material is mixed with polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) at a mass ratio of 80:10:10, dispersed in N-methylpyrrolidone (NMP) to form a uniform slurry, and then evenly coated on the aluminum foil with a doctor blade and dried at 120 °C for 6 h. The prepared electrode sheet is subjected to double-roll pressing and then cut into circular pieces with a diameter of 14 mm, and the active material loading is 2-3 mg, which is used as the working electrode; lithium is used as the counter electrode, the separator is a Celgard PP membrane, and the electrolyte is composed of 1 M LiPF6 dissolved in a mixed solvent of ethylene methyl carbonate (EMC), dimethyl carbonate (DMC), and ethylene carbonate (EC) with a mass ratio of 1:1:1, and charge-discharge tests are carried out.

[0049] Example 2

[0050] Example 1 of the present invention provides a surface modification method for a lithium cobalt oxide cathode, including the following steps:

[0051] Immerse the lithium cobalt oxide cathode material in a 30% sodium bis(dimethoxyethoxy)aluminate toluene solution with a liquid-solid ratio of 4, and react at room temperature for 1 h.

[0052] Centrifuge and wash the reaction mixture with toluene solution 4 times at 5000 rpm with a centrifuge liquid-solid ratio of 3, and centrifuge for 20 min each time.

[0053] Put the centrifuged solid in an oven at 120 °C for 12 h to obtain the modified lithium cobalt oxide cathode material;

[0054] The prepared lithium cobaltate material was used as the electrode material to assemble coin-type half-cells respectively: the modified lithium cobaltate was mixed with polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) at a mass ratio of 90:5:5, dispersed in N-methylpyrrolidone (NMP) to form a uniform slurry, then evenly coated on aluminum foil with a scraper, and dried at 120 °C for 6 hours. The prepared electrode sheet was subjected to double-roll pressing, and then cut into circular pieces with a diameter of 14 mm, and the active material loading was 2-3 mg, which was used as the working electrode; lithium was used as the counter electrode, the separator was Celgard PP membrane, and the electrolyte was composed of 1 M LiPF6 dissolved in a mixed solvent of ethylene methyl carbonate (EMC), dimethyl carbonate (DMC), and ethylene carbonate (EC) with a mass ratio of 1:1:1, and charge-discharge tests were carried out.

[0055] Example 3

[0056] This example provides a surface modification method for a high-nickel ternary cathode, including the following steps:

[0057] The high-nickel ternary cathode material was immersed in a heptane solution of sodium bis(dimethoxyethoxy)aluminate with a mass fraction of 50%, the liquid-solid ratio was 10, and the reaction was carried out at room temperature for 3 h;

[0058] The reaction solution was centrifugally washed 5 times with toluene solution at 2500 rpm, the centrifugal solid-liquid ratio was 10, and each centrifugation was 30 min;

[0059] The solid obtained by centrifugation was dried at 180 °C for 5 h to obtain the modified ternary cathode material;

[0060] The prepared ternary cathode material was used as the electrode material to assemble coin-type half-cells respectively: the modified ternary cathode material was mixed with polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) at a mass ratio of 80:10:10, dispersed in N-methylpyrrolidone (NMP) to form a uniform slurry, then evenly coated on aluminum foil with a scraper, and dried at 120 °C for 6 hours. The prepared electrode sheet was subjected to double-roll pressing, and then cut into circular pieces with a diameter of 14 mm, and the active material loading was 2-3 mg, which was used as the working electrode; lithium was used as the counter electrode, the separator was Celgard PP membrane, and the electrolyte was composed of 1 M LiPF6 dissolved in a mixed solvent of ethylene methyl carbonate (EMC), dimethyl carbonate (DMC), and ethylene carbonate (EC) with a mass ratio of 1:1:1, and charge-discharge tests were carried out. The capacity retention rate was measured to be 87.56% after 400 cycles at 1C rate.

[0061] Comparative Example 1

[0062] The differences between this comparative example and Example 1 are as follows: The unmodified lithium-rich oxide manganese-based cathode material is used as the electrode material to assemble a coin-type half-cell. The unmodified lithium-rich oxide manganese-based cathode material is mixed with polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) at a mass ratio of 80:10:10, dispersed in N-methylpyrrolidone (NMP) to form a uniform slurry, and then evenly coated on aluminum foil with a scraper and dried at 120 °C for 6 hours. The prepared electrode sheet is subjected to double-roll pressing and then cut into circular pieces with a diameter of 14 mm, and the active material loading is 2-3 mg, which is used as the working electrode; lithium is used as the counter electrode, the separator is a Celgard PP membrane, and the electrolyte is composed of 1 M LiPF6 dissolved in a mixed solvent of ethylene methyl carbonate (EMC), dimethyl carbonate (DMC), and ethylene carbonate (EC) with a mass ratio of 1:1:1, and charge-discharge tests are carried out.

[0063] Comparative Example 2

[0064] The differences between this comparative example and Example 2 are as follows: The unmodified lithium cobalt oxide cathode material is used as the electrode material to assemble a coin-type half-cell. The unmodified lithium cobalt oxide cathode material is mixed with polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) at a mass ratio of 90:5:5, dispersed in N-methylpyrrolidone (NMP) to form a uniform slurry, and then evenly coated on aluminum foil with a scraper and dried at 120 °C for 6 hours. The prepared electrode sheet is subjected to double-roll pressing and then cut into circular pieces with a diameter of 14 mm, and the active material loading is 2-3 mg, which is used as the working electrode; lithium is used as the counter electrode, the separator is a Celgard PP membrane, and the electrolyte is composed of 1 M LiPF6 dissolved in a mixed solvent of ethylene methyl carbonate (EMC), dimethyl carbonate (DMC), and ethylene carbonate (EC) with a mass ratio of 1:1:1, and charge-discharge tests are carried out.

[0065] The SEM comparison diagrams of the materials before and after modification in Comparative Example 1 and Example 1 are as Figure 2 shown. As Figure 2 (a) in shows the SEM image of the unmodified lithium-rich oxide manganese-based cathode material in Comparative Example 1. As Figure 2 (b) in shows the SEM image of the modified lithium-rich oxide manganese-based cathode material in Example 1. It can be seen that the surface sites of the modified material increase. The TEM comparison diagrams of the materials before and after modification in Comparative Example 1 and Example 1 are as Figure 3 shown; Figure 3 (a) in is the TEM image of the unmodified lithium-rich oxide manganese-based cathode material in Comparative Example 1, Figure 3 (b) in is the TEM image of the modified lithium-rich oxide manganese-based cathode material in Example 1. It can be seen that after modification, a solvation structure is formed on the material surface.

[0066] Similarly, the SEM comparison diagrams of the materials before and after modification in Comparative Example 2 and Example 2 are as follows Figure 4 shown. As Figure 4 (a) in shows the SEM diagram of the unmodified lithium cobalt oxide cathode material in Comparative Example 1. As Figure 4 (b) in shows the SEM diagram of the modified lithium cobalt oxide cathode material in Example 1. It can be seen that the surface sites of the modified material increase. The TEM comparison diagrams of the materials before and after modification in Comparative Example 2 and Example 2 are as follows Figure 5 shown; Figure 5 (a) in is the TEM diagram of the unmodified lithium cobalt oxide cathode material in Comparative Example 1, Figure 5 (b) in is the TEM diagram of the modified lithium cobalt oxide cathode material in Example 1. It can be seen that after modification, a solvation structure is formed on the surface of the material.

[0067] The test results of Example 1 and Comparative Example 1 are as follows Figure 6 shown. For the unmodified lithium-rich oxide manganese-based cathode material in Comparative Example 1, the capacity retention rate after 400 cycles at a current rate of 1C is 77.61%. While for the material modified in Example 1, the capacity retention rate after 400 cycles at a current rate of 1C is 91.02%, and the capacity retention rate is increased by 17%. As Figure 7 shown, the 0.1C first-cycle discharge efficiency of the modified material is also significantly higher than that of the unmodified material.

[0068] In Example 2, the dried material was assembled into a coin-type half-cell and charge-discharge tests were carried out. As Figure 8 shown, the measured capacity retention rate after 400 cycles at a current rate of 1C is 82.23%, which is much higher than 40.65% of the unmodified lithium cobalt oxide, and the performance after modification is improved by 102%. As Figure 9 shown, the 0.1C first-cycle discharge efficiency of the modified material is also significantly higher than that of the unmodified lithium cobalt oxide material.

[0069] In summary, in this solution, through a one-step liquid-phase reaction of the cathode material with sodium bis(dimethoxyethoxy)aluminate (commonly known as Red-Al), a solvation structure is formed on the surface of the lithium / sodium battery cathode material; finally, the modified cathode material is prepared through washing, centrifugation and drying, which can effectively improve the electrochemical properties such as the first Coulomb efficiency, cycle stability and rate performance of the lithium / sodium battery cathode material.

[0070] The above specific embodiments have further detailed the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above is only the specific embodiment of the present invention and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Preparation method for the surface of the solvation structure of a battery cathode material, characterized in that It includes the following steps: S1. Stir and react the lithium-ion battery material or sodium-ion battery material with the sodium bis(dimethoxyethoxy)aluminate solution in a container filled with argon; S2. After the reaction, use a solvent to centrifuge and wash the reacted solid; S3. Transfer the centrifuged and washed material to an oven, dry it in an inert gas atmosphere to remove the residual solvent, and finally obtain the lithium-ion or sodium-ion battery material with a solvated structure on the surface.

2. The preparation method of the surface of the solvation structure of the cathode material of the battery according to claim 1, characterized in that In step S1, the solvent of the sodium bis(dimethoxyethoxy)aluminate solution is an oil-soluble solvent.

3. The preparation method of the surface of the solvation structure of the cathode material of the battery according to claim 2, characterized in that, The oil-soluble solvent includes a short-chain alkane-substituted derivative selected from long-chain alkanes or benzene.

4. The preparation method of the solvation structure surface of the cathode material of the battery according to claim 3, wherein The long-chain alkane is selected from octane or heptane; the short-chain alkane-substituted derivative of benzene is selected from any one of benzene, toluene or ethylbenzene.

5. The preparation method of the solvation structure surface of the cathode material of the battery according to claim 1, wherein, In step S1, the stirring reaction time is 1 - 3 h.

6. The preparation method of the solvation structure surface of the cathode material of the battery according to claim 1, wherein, In step S1, the mass fraction of sodium bis(dimethoxyethoxy)aluminate in the solution is 10% - 50%.

7. The preparation method of the surface of the solvation structure of the battery cathode material according to claim 1, wherein, The lithium-ion battery material is selected from any one of lithium iron phosphate, lithium manganese iron phosphate, lithium-rich manganese-based cathode material, lithium cobalt oxide cathode material or ternary cathode material; the sodium-ion battery material is selected from any one of sodium iron sulfate, sodium iron phosphate, sodium iron pyrophosphate, sodium vanadium phosphate, Prussian blue or P2 / O3-phase layered sodium-ion cathode material.

8. The preparation method of the surface of the solvation structure of the battery cathode material according to claim 1, characterized in that, In step S1, the liquid-solid ratio of the sodium bis(dimethoxyethoxy)aluminate solution to the lithium-ion battery material or sodium-ion battery material is 3 - 10.

9. The preparation method of the surface of the solvation structure of the battery cathode material according to claim 1, characterized in that, In step S2, the centrifugation speed is ≥2500 rpm, the centrifugation solid-liquid ratio is 2 - 10, the centrifugation time is 10 - 30 min, and the number of centrifugation times is 3 - 5 times.

10. The preparation method of the solvation structure surface of the cathode material for lithium-ion batteries according to claim 1, characterized in that, In step S3, the drying temperature is 120 - 180 °C, the drying time is 5 - 12 h, and the inert gas is argon.

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