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

Abstract

The application discloses a modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof, and belongs to the technical field of positive electrode materials. The preparation method comprises the following steps: (1) adding an acid with high electronegativity into a solvent to obtain an acid solution; adding a MOF material into the acid solution, heating and reacting for a set time, and then performing solid-liquid separation to obtain a MOF material containing a high-electronegativity anion group; wherein the acid with high electronegativity is one or more of trifluoromethanesulfonic acid, trinitrobenzenesulfonic acid and cyanoacetic acid; (2) mixing the MOF material containing the high-electronegativity anion group with a lithium-rich manganese-based positive electrode material in a solid phase to obtain a modified lithium-rich manganese-based positive electrode material. In the application, the MOF material is treated by the acid with high electronegativity and then is compounded with the lithium-rich manganese-based positive electrode material, so that the ion transmission rate of the interface of the positive electrode material can be effectively improved, the polarization phenomenon of the positive electrode material can be reduced, and the rate performance of the material can be improved.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology, specifically relating to a modified lithium-rich manganese-based cathode material, its preparation method, and its application. Background Technology

[0002] Currently, the mainstream cathode materials on the market include lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), and ternary cathode materials (including NCM and NCA). Among these materials, lithium-rich manganese-based materials are considered the most promising cathode materials for next-generation lithium-ion batteries due to their ultra-high specific capacity, high voltage characteristics, and significant cost advantages. Lithium-rich manganese-based materials are the core materials for achieving breakthroughs in high energy density technology for power lithium batteries, boasting a specific capacity as high as 300 mAh / g, far exceeding the discharge specific capacity of currently commercially used lithium iron phosphate and ternary materials, almost twice the actual capacity of currently commercialized cathode materials. Compared with common lithium cobalt oxide and nickel-cobalt-manganese ternary cathode materials, lithium-rich manganese-based materials reduce costs and improve safety. However, lithium-rich manganese-based cathode materials suffer from rapid capacity decay and are prone to polarization during cycling; furthermore, their reaction kinetics are poor, resulting in poor ion and electron transport performance. These problems restrict the widespread commercial application of lithium-rich manganese-based cathode materials. Summary of the Invention

[0003] Therefore, the purpose of this invention is to provide a modified lithium-rich manganese-based cathode material, its preparation method, and its application.

[0004] In a first aspect, the present invention provides a method for preparing a modified lithium-rich manganese-based cathode material, comprising the following steps:

[0005] (1) Add a highly electronegative acid to a solvent to obtain an acidic solution; add the MOF material to the acidic solution, heat the reaction for a set time, and then separate the solid and liquid to obtain a MOF material containing highly electronegative anionic groups; wherein: the highly electronegative acid is one or more of trifluoromethanesulfonic acid (CF3SO3H), trinitrobenzenesulfonic acid (C6H3N3O9S), and cyanoacetic acid (C3H3NO2);

[0006] (2) After solid-phase mixing of MOF material containing highly electronegative anionic groups with lithium-rich manganese-based cathode material, modified lithium-rich manganese-based cathode material is obtained.

[0007] Preferably, in step (1), the MOF material is one or more of Mn-MOF, Ni-MOF, and Co-MOF; the solvent is one or more of ethanol, N,N-dimethylformamide, water, acetonitrile, dimethyl sulfoxide, and diethyl ether, and more preferably one or more of ethanol, N,N-dimethylformamide, acetonitrile, dimethyl sulfoxide, and diethyl ether.

[0008] Preferably, in step (1), the mass-to-volume ratio of the highly electronegative acid to the solvent is (2.5~5.5)g:(45~90)mL, and the mass-to-volume ratio of the MOF material to the acidic solution is 1g:(50~100)mL.

[0009] Preferably, in step (1), the heating temperature is 70~90℃ and the set time is 2~6h.

[0010] Preferably, in step (1), the method for preparing MOF materials includes the following steps:

[0011] After mixing the metal salt solution with the organic ligand solution, a hydrothermal reaction is carried out. After the reaction is completed, the solid and liquid are separated to obtain the MOF material.

[0012] More preferably, the metal salt is one or more of manganese salt, nickel salt, and cobalt salt, specifically one or more of manganese, nickel, and cobalt sulfates, nitrates, and chlorides; the concentration of the metal salt solution is 1~3 mol / L.

[0013] More preferably, the organic ligand is one or more of pyromellitic acid, phthalic acid, and isophthalic acid; the molar ratio of the metal salt to the organic ligand is 1:(5~10).

[0014] More preferably, the hydrothermal reaction temperature is 120~160℃ and the hydrothermal reaction time is 18~36h.

[0015] Preferably, in step (2), the chemical formula of the lithium-rich manganese-based cathode material is Li. 1+m Mn 1-m-n X n O2, where X is one or more of Ni, Co, Fe, Al, and Zn, 0.1≤m≤0.4, 0≤n<0.6.

[0016] Preferably, in step (2), the mass ratio of the MOF material containing highly electronegative anionic groups to the lithium-rich manganese-based cathode material is 0.01~0.05:1.

[0017] Preferably, in step (2), solid-phase mixing is performed by ball milling.

[0018] Secondly, the present invention provides a modified lithium-rich manganese-based cathode material, which is prepared by the aforementioned preparation method.

[0019] Thirdly, the present invention provides an application of the aforementioned modified lithium-rich manganese-based cathode material in lithium batteries.

[0020] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0021] (1) In this invention, the MOF material is treated with a highly electronegative acid and then combined with a lithium-rich manganese-based cathode material, which can effectively improve the ion transport rate at the cathode material interface, reduce the polarization phenomenon of the cathode material, and improve the rate performance of the material.

[0022] (2) The preparation method of the modified lithium-rich manganese-based cathode material in this invention is simple and easy to realize industrial production. Attached Figure Description

[0023] Figure 1 The graph shows the cycle performance of batteries assembled with the cathode materials prepared in Examples 1-6 and Comparative Example 1. Detailed Implementation

[0024] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0025] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0026] As mentioned above, in the first aspect, the present invention provides a method for preparing a modified lithium-rich manganese-based cathode material, comprising the following steps:

[0027] (1) Add a highly electronegative acid to a solvent to obtain an acidic solution; add the MOF material to the acidic solution, heat the reaction for a set time, and then separate the solid and liquid to obtain a MOF material containing highly electronegative anionic groups; wherein: the highly electronegative acid is one or more of trifluoromethanesulfonic acid (CF3SO3H), trinitrobenzenesulfonic acid (C6H3N3O9S), and cyanoacetic acid (C3H3NO2);

[0028] (2) After solid-phase mixing of MOF material containing highly electronegative anionic groups with lithium-rich manganese-based cathode material, modified lithium-rich manganese-based cathode material is obtained.

[0029] In this invention, MOF materials are thermally reacted with highly electronegative acid solutions. During the reaction, the anionic groups of the highly electronegative acid may exist in the pores or surface of the MOF materials through adsorption or complexation, resulting in MOF materials containing highly electronegative anionic groups. Therefore, when MOF materials containing highly electronegative anionic groups are used to modify lithium-rich manganese-based materials, their comprehensive electrochemical performance can be effectively improved.

[0030] Preferably, in step (1), the MOF material is one or more of Mn-MOF, Ni-MOF, and Co-MOF; the solvent is one or more of ethanol, N,N-dimethylformamide, water, acetonitrile, dimethyl sulfoxide, and diethyl ether, and more preferably one or more of ethanol, N,N-dimethylformamide, acetonitrile, dimethyl sulfoxide, and diethyl ether.

[0031] The solvent used in this invention is preferably an organic solvent. Organic solvents, as a medium, can reduce the degree of acid ionization and prevent highly electronegative acids from affecting the structure of MOF materials. Highly electronegative acids are all organic acids, which have stronger coordinating abilities and can maximize the formation of MOF materials with highly electronegative anionic groups.

[0032] Preferably, in step (1), the mass-to-volume ratio of the highly electronegative acid to the solvent is (2.5~5.5)g:(45~90)mL, including but not limited to 2.5:45, 4.5:45, 5.5:45, 2.5:60, 4.5:60, 5.5:60, 2.5:90, 4.5:90, 5.5:90, etc.; the mass-to-volume ratio of the MOF material to the acidic solution is 1g:(50~100)mL, including but not limited to 1g:50mL, 1g:60mL, 1g:70mL, 1g:80mL, 1g:90mL, 1g:100mL, etc.

[0033] In this invention, by controlling the ratio of MOF material, solvent and highly electronegative acid, it is possible to ensure that the MOF material can be loaded with a large number of highly electronegative anionic groups while avoiding damage to the structure of the MOF material.

[0034] Preferably, in step (1), the heating temperature is 70~90℃, including but not limited to 70℃, 75℃, 80℃, 85℃, 90℃, etc.; the set time is 2~6h, including but not limited to 2h, 3h, 4h, 5h, 6h, etc.

[0035] Preferably, in step (1), the method for preparing MOF materials includes the following steps:

[0036] After mixing the metal salt solution and the organic ligand solution, a hydrothermal reaction is carried out. After the reaction is completed, the solid and liquid are separated to obtain the MOF material.

[0037] More preferably, the metal salt is one or more of manganese salt, nickel salt, and cobalt salt; specifically, it is one or more of manganese, nickel, and cobalt sulfate, nitrate, and chloride salts; the concentration of the metal salt solution is 1~3 mol / L, including but not limited to 1 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, etc.

[0038] The use of manganese, nickel, and manganese MOF materials in this invention can better improve the overall electrochemical performance of lithium-rich manganese-based materials.

[0039] More preferably, the organic ligand is one or more of pyromellitic acid, phthalic acid, and isophthalic acid; the molar ratio of the metal salt to the organic ligand is 1:(5~10), including but not limited to 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0040] More preferably, the hydrothermal reaction temperature is 120~160℃, including but not limited to 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 160℃, etc.; the hydrothermal reaction time is 18~36h, including but not limited to 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h, etc.

[0041] Preferably, in step (2), the chemical formula of the lithium-rich manganese-based cathode material is Li. 1+m Mn 1-m-n X n O2, where X is one or more of Ni, Co, Fe, Al, and Zn, 0.1≤m≤0.4, 0≤n<0.6.

[0042] Preferably, in step (2), the mass ratio of the MOF material with high electronegativity anion groups to the lithium-rich manganese-based cathode material is 0.01 to 0.05:1, including but not limited to 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, etc.

[0043] Preferably, in step (2), solid-phase mixing is performed by ball milling.

[0044] Secondly, the present invention provides a modified lithium-rich manganese-based cathode material, which is prepared by the aforementioned preparation method.

[0045] Thirdly, the present invention provides an application of the aforementioned modified lithium-rich manganese-based cathode material in lithium batteries.

[0046] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0047] Preparation Example 1: Lithium-rich manganese-based material Li 1.1 Mn 0.6 Co 0.3 O2 preparation

[0048] 0.067 mol MnSO4·H2O and 0.033 mol CoSO4·6H2O were dissolved in deionized water to prepare a 2 mol / L metal ion solution. This solution was then added to a continuous stirred tank reactor under a nitrogen atmosphere. 4 mol / L NaOH precipitant and 20 wt% NH3·H2O complexing agent were continuously added, maintaining the pH of the reaction solution within the range of 10-11. After 40 hours of complete reaction, the solid and liquid phases were separated. The solid product was washed with water, then with alcohol, and dried to obtain Mn. 0.67 Co 0.33 (OH)2. Add 0.1 mol Mn 0.67 Co 0.33 (OH)₂ was mechanically mixed with 0.123 mol of lithium hydroxide and then sintered at 980 °C for 20 h in a muffle furnace to finally obtain Li. 1.1 Mn 0.6 Co 0.3 O2.

[0049] Preparation Example 2: Lithium-rich manganese-based material Li 1.2 Mn 0.6 Fe 0.2 O2 preparation

[0050] 0.075 mol MnSO4·H2O and 0.025 mol FeSO4·6H2O were dissolved in deionized water to prepare a 2 mol / L metal ion solution. This solution was then added to a continuous stirred tank reactor under a nitrogen atmosphere. 4 mol / L NaOH precipitant and 20 wt% NH3·H2O complexing agent were continuously added to maintain the pH of the solution within the range of 10–11. After a complete reaction for 40 hours, the solid and liquid phases were separated. The solid product was washed with water, then with alcohol, and dried to obtain Mn. 0.75 Fe 0.25 (OH)2. Add 0.1 mol Mn 0.75 Fe 0.25 (OH)₂ was mechanically mixed with 0.154 mol of lithium hydroxide and then sintered at 1100 °C for 10 h in a muffle furnace to finally obtain Li. 1.2 Mn 0.6 Fe 0.2 O2.

[0051] Preparation Example 3: Preparation of Ni-MOF

[0052] 0.1 mol of nickel sulfate was dissolved in 35 mL of deionized water to obtain a nickel sulfate solution; 0.8 mol of phthalic acid was dispersed in 300 mL of DMF to obtain an organic ligand solution; the nickel sulfate solution and the organic ligand solution were mixed and placed in a polytetrafluoroethylene hydrothermal reactor, and the mixture was hydrothermally reacted at 140 °C for 24 h. After filtration, washing and drying, Ni-MOF material was obtained.

[0053] Preparation Example 4: Preparation of Mn-MOF

[0054] 0.1 mol of manganese nitrate was dissolved in 100 mL of deionized water to obtain a manganese nitrate solution; 0.5 mol of isophthalic acid was dispersed in 300 mL of DMF to obtain an organic ligand solution; the manganese sulfate solution and the organic ligand solution were mixed and placed in a polytetrafluoroethylene hydrothermal reactor. After hydrothermal reaction at 120 °C for 36 h, the product was filtered, washed and dried to obtain the Mn-MOF material.

[0055] Preparation Example 5: Preparation of Co-MOF

[0056] 0.1 mol of cobalt nitrate was dissolved in 50 mL of deionized water to obtain a cobalt nitrate solution; 1 mol of trimesic acid was dispersed in 500 mL of DMF to obtain an organic ligand solution; the cobalt nitrate solution and the organic ligand solution were mixed evenly and placed in a polytetrafluoroethylene hydrothermal reactor. After hydrothermal reaction at 160 °C for 18 h, the product was filtered, washed and dried to obtain the Co-MOF material.

[0057] Example 1

[0058] 4.5 g of trifluoromethanesulfonic acid was dissolved in 60 mL of DMF to form organic solution A. 1 g of the Ni-MOF material prepared in Preparation Example 3 was dispersed in organic solution A. After heating at 80 °C for 4 h, solid-liquid separation was performed to obtain the MOF material containing highly electronegative anionic groups. 0.15 g of the MOF material containing highly electronegative anionic groups and 5 g of the Li-MOF material prepared in Preparation Example 1 were then mixed. 1.1 Mn 0.6 Co 0.3 O2 material was ball-milled for solid-phase mixing to obtain modified lithium-rich manganese-based cathode material.

[0059] Comparative Example 1

[0060] 0.15g of Ni-MOF material and 5g of Li prepared in Example 1 were used. 1.1 Mn 0.6 Co 0.3 O2 material was ball-milled for solid-phase mixing to obtain modified lithium-rich manganese-based cathode material.

[0061] Example 2

[0062] The solution is basically the same as in Example 1, except that DMF is replaced with an equal volume of deionized water, i.e., 4.5g of trifluoromethanesulfonic acid is dissolved in 60mL of deionized water to form solution A.

[0063] Example 3

[0064] The method is basically the same as in Example 1, except that: 0.05g of MOF material containing highly electronegative anionic groups and 5g of Li prepared in Example 1 were used. 1.1 Mn 0.6 Co 0.3 O2 material was ball-milled for solid-phase mixing.

[0065] Example 4

[0066] The method is basically the same as in Example 1, except that: 0.25g of MOF material containing highly electronegative anionic groups and 5g of Li prepared in Example 1 were used. 1.1 Mn 0.6 Co 0.3 O2 material was ball-milled for solid-phase mixing.

[0067] Example 5

[0068] 1.0 g of cyanoacetic acid and 1.5 g of trifluoromethanesulfonic acid were dissolved in 90 mL of ethanol to form organic solution A. 0.96 g of the Co-MOF material prepared in Preparation Example 5 was dispersed in organic solution A. After heating at 90 °C for 2 h, solid-liquid separation was performed to obtain the MOF material containing highly electronegative anionic groups. 0.15 g of the MOF material containing highly electronegative anionic groups and 5 g of the Li prepared in Preparation Example 2 were then... 1.2 Mn 0.6 Fe 0.2 O2 material was ball-milled for solid-phase mixing to obtain modified lithium-rich manganese-based cathode material.

[0069] Example 6

[0070] 5.4 g of trinitrobenzenesulfonic acid was dissolved in 45 mL of deionized water to form solution A. 0.96 g of the Mn-MOF material prepared in Preparation Example 4 was dispersed in solution A. After heating at 70 °C for 6 h, solid-liquid separation was performed to obtain the MOF material containing highly electronegative anionic groups. 0.15 g of the MOF material containing highly electronegative anionic groups and 5 g of Li2O3 prepared in Preparation Example 2 were then mixed. 1.2 Mn 0.6 Fe 0.2 O2 material was ball-milled for solid-phase mixing to obtain modified lithium-rich manganese-based cathode material.

[0071] The positive electrode materials prepared in Examples 1-6 and Comparative Example 1 were assembled into batteries. The positive electrode material, conductive graphite, and PVDF were weighed and ground according to a mass ratio of 8:1:1. Then, an appropriate amount of N-methylpyrrolidone (NMP) was added, and grinding and stirring were continued to form a uniform slurry. The slurry was then evenly coated onto aluminum foil using a mold to a thickness of 200 μm, and dried in a drying oven at 90°C for 10 hours. The coated foil was then cut into 12 mm diameter discs. Using the discs as the positive electrode and lithium foil as the negative electrode, the batteries were assembled in a glove box according to the coin cell assembly sequence using an electrolyte (including solvent and LiPF6, where the LiPF6 concentration was 1 mol / L, and the electrolyte solvent was a mixture of EC, DEC, and DMC with a volume ratio of 1:1:1). The assembled batteries were subjected to performance testing. The assembled batteries, which had been left to stand overnight, were placed in a LAND2001CT battery test chamber for charge-discharge testing. The test was conducted at 25°C, 1C, and a cycle voltage of 2.8~4.7V, with 100 cycles. The test results are shown below. Figure 1 See Table 1.

[0072] Table 1

[0073]

[0074] from Figure 1 As can be seen from the data in Table 1, the specific capacity and cycle performance of the battery assembled with the cathode material prepared in Example 1 are significantly improved compared to Comparative Example 1. This may be because the highly electronegative anionic groups can increase the ion transport rate of the cathode material, reduce polarization, and thus improve the overall electrochemical performance of the cathode material. Compared with Example 1, Example 2 used water as a solvent for the highly electronegative acid. The specific capacity and cycle stability of the battery assembled with the corresponding cathode material are somewhat lower than those of Example 1. This may be because the highly electronegative acid has a high degree of ionization in aqueous solution, and the acidity is too strong, slightly damaging the MOF framework, resulting in a decrease in its specific capacity and cycle stability. In Examples 3 and 4, the performance of the cathode material prepared by adding MOF material containing highly electronegative anionic groups fluctuates to some extent, indicating that there is an optimal addition amount of MOF material containing highly electronegative anionic groups. In Examples 5 and 6, the process parameters were adjusted, and the specific capacity and cycle stability of the battery assembled with the corresponding cathode material fluctuated to some extent, but the overall performance was good.

[0075] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified lithium-rich manganese-based cathode material, characterized in that, Includes the following steps: (1) Add a highly electronegative acid to a solvent to obtain an acidic solution; add the MOF material to the acidic solution, heat the reaction for a set time, and then separate the solid and liquid to obtain a MOF material containing highly electronegative anionic groups; wherein: the highly electronegative acid is one or more of trifluoromethanesulfonic acid, trinitrobenzenesulfonic acid, and cyanoacetic acid; (2) After solid-phase mixing of MOF material containing highly electronegative anionic groups with lithium-rich manganese-based cathode material, modified lithium-rich manganese-based cathode material is obtained. In step (1), the MOF material is one or more of Mn-MOF, Ni-MOF, and Co-MOF; the solvent is one or more of ethanol, N,N-dimethylformamide, water, acetonitrile, dimethyl sulfoxide, and diethyl ether; the mass-volume ratio of highly electronegative acid to solvent is (2.5~5.5)g:(45~90)mL; the mass-volume ratio of MOF material to acidic solution is 1g:(50~100)mL; the heating temperature is 70~90℃, and the set time is 2~6h.

2. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 1, characterized in that, In step (1), the preparation method of MOF material includes the following steps: After mixing the metal salt solution with the organic ligand solution, a hydrothermal reaction is carried out. After the reaction is completed, the solid and liquid are separated to obtain the MOF material.

3. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 2, characterized in that, The metal salt is one or more of manganese salt, nickel salt, and cobalt salt, specifically one or more of manganese, nickel, and cobalt sulfates, nitrates, and chlorides; the concentration of the metal salt solution is 1~3 mol / L; The organic ligand is one or more of pyromellitic acid, phthalic acid, and isophthalic acid; the molar ratio of the metal salt to the organic ligand is 1:(5~10).

4. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 1, characterized in that, In step (2), the chemical formula of the lithium-rich manganese-based cathode material is Li 1+m Mn 1-m-n X n O2, where X is one or more of Ni, Co, Fe, Al, and Zn, 0.1≤m≤0.4, 0≤n<0.

6.

5. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 1, characterized in that, In step (2), the mass ratio of the MOF material containing highly electronegative anion groups to the lithium-rich manganese-based cathode material is 0.01~0.05:

1.

6. A modified lithium-rich manganese-based cathode material, characterized in that, It is prepared by any of the preparation methods described in claims 1 to 5.

7. A lithium battery, characterized in that, Including the modified lithium-rich manganese-based cathode material as described in claim 6.

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