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

Abstract

The invention belongs to the technical field of new energy materials, and discloses a modified manganese-based positive electrode material and a preparation method and application thereof. The preparation method comprises the following steps: mixing a manganese-based positive electrode material, a selenium source and an organic solvent, performing ultrasonic dispersion, and sequentially performing drying and ball milling on dispersion liquid to obtain a modified manganese-based material precursor; and sintering the modified manganese-based material precursor to obtain the modified manganese-based positive electrode material. The structural stability of the modified manganese-based positive electrode material provided by the invention is remarkably improved, a Mn-O-Se bond can be formed to enhance the structural stability of the material, the volume strain in the charging and discharging process is relieved, and the formation of microcracks of the material is inhibited. And moreover, side reaction on the surface of the electrode is restrained, so that capacity fading of the material caused by side reaction on an interface can be effectively avoided, and the material has relatively good long-cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and in particular to a modified manganese-based positive electrode material and a preparation method and application thereof. Background Art

[0002] With the rapid development of society, the global demand for energy and mineral resources and the awareness of protecting the natural environment have increased dramatically. The development of environmentally friendly, high-performance and low-cost energy storage devices has become the theme of today's society. In order to cope with this problem, chemical power sources as an energy storage method have entered the public eye. Chemical power sources use the conversion between electrical energy and chemical energy to achieve the storage and output of electrical energy. They not only have the technical characteristics of rapid response and two-way regulation, but also have the technical advantages of strong environmental adaptability, small-scale decentralized configuration and short construction period. Among the many chemical energy storage devices, lithium-ion batteries (LIBs) are considered to be the most promising energy storage devices and one of the most ideal energy storage power sources because of their high energy density, good charging efficiency, stable operating voltage, environmental friendliness and long service life. Among them, manganese-based positive electrode materials have high operating voltage, high energy density and 3DLi + Diffusion channel. In addition, manganese is considered to be one of the most promising positive electrode materials for lithium-ion batteries due to its abundant resources, low cost, and environmental friendliness. However, under high temperature conditions (55°C), a series of side reactions will occur in manganese-based positive electrode materials during the charging and discharging process, causing the electrochemical performance to decay rapidly. First, LiPF6 and carbonates in the electrolyte have poor stability under high pressure, which will induce side reactions with the positive electrode materials, resulting in material capacity decay and forming a thick and uneven interface film on the surface of the material, resulting in an increase in the charge transfer resistance on the surface, hindering the transmission of lithium ions. Secondly, the byproducts generated by the reaction of LiPF6 dissolved in the electrolyte with water will accelerate the dissolution of active substances such as Ni and Mn, thereby reducing the specific capacity of the positive electrode material. Summary of the invention

[0003] The purpose of the present invention is to provide a modified manganese-based positive electrode material and a preparation method and application thereof, so as to solve the problem that unmodified manganese-based positive electrode materials will undergo side reactions under high temperature conditions, resulting in rapid attenuation of electrochemical performance.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a modified manganese-based positive electrode material, comprising the following steps:

[0006] (1) mixing a manganese-based positive electrode material, a selenium source and an organic solvent, performing ultrasonic dispersion, and sequentially drying and ball milling the dispersion to obtain a modified manganese-based material precursor;

[0007] (2) sintering the modified manganese-based material precursor described in step (1) to obtain a modified manganese-based positive electrode material;

[0008] Wherein, in step (1), the manganese-based positive electrode material includes lithium manganese oxide or lithium nickel manganese oxide, and the selenium source includes selenium dioxide or selenium powder.

[0009] Preferably, in the preparation method, in step (1), the organic solvent comprises ethanol.

[0010] Preferably, in the preparation method, in step (1), the mass of the selenium source is 1-5% of the mass of the manganese-based positive electrode material; the mass volume ratio of the manganese-based positive electrode material to the organic solvent is 4g:100-150mL.

[0011] Preferably, in the preparation method, in step (1), the frequency of the ultrasonic dispersion is 40 to 80 kHz, the power is 500 to 1000 W, and the time is 30 to 60 min.

[0012] Preferably, in the preparation method, in step (1), the organic solvent is removed after ultrasonic dispersion; the organic solvent is removed by heating in a water bath; the water bath heating temperature is 70 to 80° C., and the time is 3 to 5 hours.

[0013] Preferably, in the preparation method, in step (1), the rotation speed of the ball mill is 300-400 r / min, the time is 3-5 h, and the ball-to-material ratio is 1:10-20.

[0014] Preferably, in the preparation method, in step (1), the preparation method of the manganese-based positive electrode material comprises the following steps: mixing and grinding a lithium source and a manganese source, and sequentially performing a first sintering and a second sintering to obtain a manganese-based positive electrode material.

[0015] Preferably, in the preparation method, in step (2), the sintering temperature is 500-600° C., the time is 4-6 hours, and the rate of heating to the desired sintering temperature is 2-5° C. / min.

[0016] The present invention also provides a modified manganese-based positive electrode material obtained by the preparation method.

[0017] The present invention also provides an application of the modified manganese-based positive electrode material in a lithium ion battery.

[0018] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The preparation method of the present invention combines ultrasonic dispersion with ball milling, and after ultrasonic dispersion, the organic solvent is evaporated by heating in a water bath, so that the element selenium is more evenly doped into the manganese-based positive electrode material, and further sintering is performed to synthesize a modified manganese-based positive electrode material.

[0020] (2) The structural stability of the modified manganese-based positive electrode material provided by the present invention is significantly improved. The modified positive electrode material can form Mn-O-Se bonds, enhance the structural stability of the material, alleviate the volume strain during the charge and discharge process, and inhibit the formation of microcracks in the material. In addition, the side reactions on the electrode surface are curbed, which can effectively avoid the capacity decay of the material caused by the interface side reactions, and has good long-cycle stability. The modified manganese-based positive electrode material can form a buffer layer on the surface of the material, effectively inhibiting the erosion of the electrolyte and promoting Li + The modified manganese-based positive electrode material preparation method of the present invention is suitable for the existing positive electrode material preparation method, such as solid phase method and wet chemical method, and has wide applicability.

[0021] (3) The modified manganese-based positive electrode material provided by the present invention will not increase the cost of preparing lithium-ion batteries, and the production equipment involved is simple, the production cycle is short, the process is simple, and it is suitable for large-scale production.

[0022] (4) The modification method of the present invention has wide adaptability and is applicable to lithium manganese oxide, lithium nickel manganese oxide, manganese-based positive electrode materials, lithium cobalt oxide, ternary layered materials or lithium iron phosphate positive electrode materials, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art are briefly introduced below.

[0024] Figure 1 Schematic diagram of the preparation process of modified manganese-based positive electrode materials;

[0025] Figure 2 are XRD patterns of the positive electrode materials obtained in Examples 1 to 6 and Comparative Examples 1 to 2, wherein A is the XRD pattern of the positive electrode materials obtained in Examples 4 to 6 and Comparative Example 2, and B is the XRD pattern of the positive electrode materials obtained in Examples 1 to 3 and Comparative Example 1;

[0026] Figure 3 The figures are the cycle performance test results of the batteries obtained in Application Examples 1 to 6 and Comparative Application Examples 1 to 2, wherein A is the initial discharge specific capacity diagram of Application Example 2 and Comparative Application Example 1, B is the initial discharge specific capacity diagram of Application Example 5 and Comparative Application Example 2, C is the cycle performance diagram of Application Examples 1 to 3 and Comparative Application Example 1, and D is the cycle performance diagram of Application Examples 4 to 6 and Comparative Application Example 2. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing a modified manganese-based positive electrode material, comprising the following steps:

[0028] (1) mixing a manganese-based positive electrode material, a selenium source and an organic solvent, performing ultrasonic dispersion, and sequentially drying and ball milling the dispersion to obtain a modified manganese-based material precursor;

[0029] (2) sintering the modified manganese-based material precursor described in step (1) to obtain a modified manganese-based positive electrode material;

[0030] Wherein, in step (1), the manganese-based positive electrode material includes lithium manganese oxide or lithium nickel manganese oxide, and the selenium source includes selenium dioxide or selenium powder.

[0031] In the present invention, the specific method of mixing the manganese-based positive electrode material, the selenium source and the organic solvent and performing ultrasonic dispersion in step (1) preferably includes the following steps:

[0032] The selenium source and the organic solvent are mixed and ultrasonically dispersed, and the manganese-based positive electrode material is added to the obtained mixed solution and ultrasonically dispersed.

[0033] In the present invention, the manganese-based positive electrode material in step (1) is lithium manganese oxide or lithium nickel manganese oxide, preferably lithium nickel manganese oxide.

[0034] In the present invention, in step (1), the method for preparing the manganese-based positive electrode material comprises the following steps: mixing and grinding a lithium source and a manganese source, and sequentially performing a first sintering and a second sintering to obtain a manganese-based positive electrode material.

[0035] In the present invention, the lithium source preferably includes LiOH·H2O or Li2CO3, and more preferably LiOH·H2O.

[0036] In the present invention, the manganese source preferably includes MnCO3, Mn3O4, MnO2 or (Mn 1.5 Ni 0.5 )OH2 (nickel manganese hydroxide), more preferably MnCO3, MnO2 or (Mn 1.5 Ni 0.5 )OH2, more preferably MnCO3 or (Mn 1.5 Ni 0.5 )OH2.

[0037] In the present invention, the molar ratio of the lithium source to the manganese source is preferably 2:1 to 1.08, more preferably 2:1 to 1.05, and more preferably 2:1.05.

[0038] In the present invention, the mixing and grinding conditions are not limited, and any method known to those skilled in the art can be used.

[0039] In the present invention, the equipment for the first sintering and the second sintering is preferably a muffle furnace.

[0040] In the present invention, the temperature of the first sintering is preferably 400-500°C, more preferably 450-500°C, and more preferably 480°C; the time is preferably 4-6h, more preferably 4-5h, and more preferably 4h; the rate of heating to the desired first sintering temperature is preferably 2-5°C / min, more preferably 2-3°C / min, and more preferably 3°C / min.

[0041] In the present invention, the temperature of the second sintering is preferably 780-850°C, more preferably 800-850°C, and more preferably 800°C; the time is preferably 10-14h, more preferably 10-13h, and more preferably 13h; the rate of heating to the desired second sintering temperature is preferably 2-5°C / min, more preferably 2-3°C / min, and more preferably 3°C / min.

[0042] In the present invention, the selenium source in step (1) includes selenium dioxide or selenium powder, preferably selenium powder.

[0043] In the present invention, the organic solvent in step (1) preferably comprises ethanol.

[0044] In the present invention, the mass of the selenium source in step (1) is preferably 1-5% of the mass of the manganese-based positive electrode material, more preferably 1-3%, and more preferably 3%.

[0045] In the present invention, the mass volume ratio of the manganese-based positive electrode material to the organic solvent in step (1) is preferably 4 g: 100-150 mL, more preferably 4 g: 100-120 mL, and more preferably 4 g: 120 mL.

[0046] In the present invention, the frequency of the ultrasonic dispersion in step (1) is preferably 40 to 80 kHz, more preferably 45 to 65 kHz, and more preferably 50 kHz; the power is preferably 500 to 1000 W, more preferably 800 to 1000 W, and more preferably 1000 W; the time is preferably 30 to 60 min, more preferably 45 to 60 min, and more preferably 60 min.

[0047] In the present invention, step (1) preferably further comprises removing the organic solvent after ultrasonic dispersion.

[0048] In the present invention, the method of removing the organic solvent is preferably heating in a water bath.

[0049] In the present invention, the water bath heating temperature is preferably 70-80°C, more preferably 70-75°C, more preferably 75°C; the heating time is preferably 3-5h, more preferably 4-5h, more preferably 4h.

[0050] In the present invention, the specific method of drying in step (1) is preferably vacuum drying.

[0051] In the present invention, the drying temperature in step (1) is preferably 80-120°C, more preferably 100-120°C, and more preferably 110°C; the drying time is preferably 10-12h, more preferably 11-12h, and more preferably 12h.

[0052] In the present invention, the equipment for ball milling in step (1) is preferably a planetary ball mill.

[0053] In the present invention, the rotation speed of the ball mill in step (1) is preferably 300-400 r / min, more preferably 350-400 r / min, more preferably 350 r / min; the time is preferably 3-5 h, more preferably 4-5 h, more preferably 4 h; the ball-to-material ratio is preferably 1:10-20, more preferably 1:15-20, more preferably 1:15.

[0054] In the present invention, the grinding balls used in the ball milling in step (1) are preferably zirconia grinding balls.

[0055] In the present invention, the sintering equipment in step (2) is preferably a muffle furnace.

[0056] In the present invention, the sintering temperature in step (2) is preferably 500-600°C, more preferably 500-550°C, and more preferably 550°C; the time is preferably 4-6h, more preferably 5-6h, and more preferably 5h; the rate of heating to the desired sintering temperature is preferably 2-5°C / min, more preferably 2-4°C / min, and more preferably 3°C / min.

[0057] The present invention also provides a modified manganese-based positive electrode material obtained by the preparation method.

[0058] The present invention also provides an application of the modified manganese-based positive electrode material in a lithium ion battery.

[0059] In the present invention, the application method is not limited, and any method known to those skilled in the art may be used.

[0060] In the present invention, the lithium ion battery is preferably a CR2025 button battery.

[0061] In the present invention, the lithium-ion battery preferably includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.

[0062] In the present invention, the method for preparing the positive electrode sheet preferably comprises the following steps:

[0063] The modified manganese-based positive electrode material, conductive carbon black, a binder and an organic solvent are mixed to obtain a positive electrode slurry; the positive electrode slurry is coated on an aluminum foil, dried, dried in a vacuum drying oven, and cut to obtain a positive electrode sheet.

[0064] In the present invention, the binder is preferably polyvinylidene fluoride (PVDF).

[0065] In the present invention, the organic solvent is preferably N-methylpyrrolidone (NMP).

[0066] In the present invention, the mass ratio of the modified manganese-based positive electrode material, the conductive carbon black and the binder is not limited, and a solution familiar to those skilled in the art can be adopted. Specifically in the embodiment of the present invention, the mass ratio of the modified manganese-based positive electrode material, the conductive carbon black and the binder is preferably 8:1:1.

[0067] In the present invention, the mixing method is preferably grinding. The grinding time is preferably 15 to 30 minutes, more preferably 20 to 30 minutes, and more preferably 25 minutes.

[0068] In the present invention, the drying temperature is preferably 80 to 120° C., more preferably 80 to 100° C., and more preferably 90° C.; the drying time is preferably 10 to 12 h, more preferably 11 to 12 h, and more preferably 12 h.

[0069] In the present invention, the negative electrode sheet is preferably a lithium sheet.

[0070] In the present invention, the separator is preferably a Celgard 2400 separator.

[0071] In the present invention, the electrolyte is preferably a 5V high-voltage electrolyte (manufacturer is Duoduo Chemical Reagent, brand name is LB-111).

[0072] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0073] Example 1

[0074] This embodiment provides a method for preparing a modified manganese-based positive electrode material, comprising the following steps, as shown in the process Figure 1 As shown:

[0075] (1) LiOH·H2O and (Mn 1.5 Ni 0.5 )OH2 is put into a mortar and ground for 30 minutes until it is evenly ground; the ground material is put into a crucible, placed in a muffle furnace, heated to 480°C at 3°C / min and kept warm for 4 hours, then heated to 780°C at 3°C / min and kept warm for 13 hours, and cooled with the furnace to obtain lithium nickel manganese oxide;

[0076] (2) Pour selenium powder into ethanol and place it in an ultrasonic tank for ultrasonic dispersion. The frequency of ultrasonic dispersion is 50kHz, the power is 1000W, and the time is 30min, so that the selenium powder is uniformly dissolved in ethanol; add lithium nickel manganese oxide to the obtained mixed solution and continue ultrasonic dispersion. The frequency of ultrasonic dispersion is 50kHz, the power is 1000W, and the time is 30min, so that the lithium nickel manganese oxide is uniformly dispersed, wherein the mass of selenium powder is 3% of the mass of lithium nickel manganese oxide, and the mass volume ratio of lithium nickel manganese oxide to ethanol is 4g:100mL; then, place the mixed solution obtained by ultrasonic dispersion in a 70℃ water bath and stir for 4h until the ethanol is completely evaporated; then, place the above materials in a vacuum drying oven at 110℃ and dry for 10h; place the vacuum dried material in a ball mill (grinding balls are zirconium oxide grinding balls), and ball mill for 3h in a planetary ball mill at a ball-to-material ratio of 1:10 and a rotation speed of 350r / min to obtain a modified manganese-based material precursor;

[0077] (3) The modified manganese-based material precursor of step (2) was poured into a crucible and placed in a muffle furnace, the temperature was raised to 550° C. at 2° C. / min and kept at that temperature for 5 h, and then naturally cooled to room temperature to obtain a modified manganese-based positive electrode material, which was recorded as 1% Se-LMNO.

[0078] Example 2

[0079] This embodiment provides a method for preparing a modified manganese-based positive electrode material, comprising the following steps:

[0080] (1) LiOH·H2O and (Mn 1.5 Ni 0.5 )OH2 is put into a mortar and ground for 30 minutes until it is evenly ground; the ground material is put into a crucible, placed in a muffle furnace, heated to 500°C at 2°C / min and kept warm for 6 hours, then heated to 800°C at 2°C / min and kept warm for 13 hours, and cooled with the furnace to obtain lithium nickel manganese oxide;

[0081] (2) Pour selenium powder into ethanol and place it in an ultrasonic tank for ultrasonic dispersion. The frequency of ultrasonic dispersion is 50kHz, the power is 1000W, and the time is 30min, so that the selenium powder is uniformly dissolved in ethanol; add lithium nickel manganese oxide to the obtained mixed solution and continue ultrasonic dispersion. The frequency of ultrasonic dispersion is 50kHz, the power is 1000W, and the time is 30min, so that the lithium nickel manganese oxide is uniformly dispersed, wherein the mass of selenium powder is 3% of the mass of lithium nickel manganese oxide, and the mass volume ratio of lithium nickel manganese oxide to ethanol is 4g:120mL; then, place the mixed solution obtained by ultrasonic dispersion in a 75°C water bath and stir for 4h until the ethanol is completely evaporated; then, place the above materials in a vacuum drying oven at 100°C and dry for 12h; place the vacuum-dried material in a ball mill (grinding balls are zirconium oxide grinding balls), and ball mill it in a planetary ball mill at a ball-to-material ratio of 1:15 and a rotation speed of 400r / min for 4h to obtain a modified manganese-based material precursor;

[0082] (3) The modified manganese-based material precursor of step (2) was poured into a crucible and placed in a muffle furnace, the temperature was raised to 500° C. at 3° C. / min and kept at this temperature for 5 h, and then naturally cooled to room temperature to obtain a modified manganese-based positive electrode material, which was recorded as 3% Se-LMNO.

[0083] Example 3

[0084] This embodiment provides a method for preparing a modified manganese-based positive electrode material, comprising the following steps:

[0085] (1) LiOH·H2O and (Mn 1.5 Ni 0.5 )OH2 is put into a mortar and ground for 30 minutes until it is evenly ground; the ground material is put into a crucible, placed in a muffle furnace, heated to 450°C at 5°C / min and kept warm for 5 hours, then heated to 850°C at 5°C / min and kept warm for 10 hours, and cooled with the furnace to obtain lithium nickel manganese oxide;

[0086] (2) Pour selenium powder into ethanol and place it in an ultrasonic tank for ultrasonic dispersion. The frequency of ultrasonic dispersion is 50kHz, the power is 1000W, and the time is 30min, so that the selenium powder is uniformly dissolved in ethanol; add lithium nickel manganese oxide to the obtained mixed solution and continue ultrasonic dispersion. The frequency of ultrasonic dispersion is 50kHz, the power is 1000W, and the time is 30min, so that the lithium nickel manganese oxide is uniformly dispersed, wherein the mass of selenium powder is 5% of the mass of lithium nickel manganese oxide, and the mass volume ratio of lithium nickel manganese oxide to ethanol is 4g:150mL; then, place the mixed solution obtained by ultrasonic dispersion in an 80°C water bath and stir for 4h until the ethanol is completely evaporated; then, place the above materials in a vacuum drying oven at 120°C and dry for 10h; place the vacuum-dried material in a ball mill (the grinding balls are zirconium oxide grinding balls), and ball mill it in a planetary ball mill at a ball-to-material ratio of 1:20 and a rotation speed of 350r / min for 5h to obtain a modified manganese-based material precursor;

[0087] (3) The modified manganese-based material precursor of step (2) was poured into a crucible and placed in a muffle furnace, and the temperature was raised to 500° C. at 4° C. / min and kept at this temperature for 6 h, and then naturally cooled to room temperature to obtain a modified manganese-based positive electrode material, which was recorded as 5% Se-LMNO.

[0088] Example 4

[0089] This embodiment provides a method for preparing a modified manganese-based positive electrode material, comprising the following steps:

[0090] (1) LiOH·H2O and MnCO3 in a molar ratio of 2:1 are put into a mortar and ground for 30 minutes until the grinding is uniform; the ground material is put into a crucible, placed in a muffle furnace, heated to 500°C at 2°C / min and kept at this temperature for 4 hours, then heated to 800°C at 2°C / min and kept at this temperature for 10 hours, and cooled with the furnace to obtain lithium manganate;

[0091] The difference between step (2) and step (2) of Example 1 is that the lithium nickel manganese oxide is replaced by the lithium manganese oxide prepared in step (1) of Example 4, and the other parameter conditions are the same as those of step (2) of Example 1;

[0092] Step (3) is the same as step (3) of Example 1, and the obtained modified manganese-based positive electrode material is recorded as 1% Se-LMO.

[0093] Example 5

[0094] This embodiment provides a method for preparing a modified manganese-based positive electrode material, comprising the following steps:

[0095] (1) LiOH·H2O and MnCO3 in a molar ratio of 2:1.05 are put into a mortar and ground for 30 minutes until the grinding is uniform; the ground material is put into a crucible, placed in a muffle furnace, heated to 480°C at 3°C / min and kept at this temperature for 4 hours, then heated to 780°C at 3°C / min and kept at this temperature for 13 hours, and cooled with the furnace to obtain lithium manganate;

[0096] The difference between step (2) and step (2) of Example 2 is that the lithium nickel manganese oxide is replaced by the lithium manganese oxide prepared in step (1) of Example 5, and the other parameter conditions are the same as those of step (2) of Example 2;

[0097] Step (3) is the same as step (3) of Example 2, and the obtained modified manganese-based positive electrode material is recorded as 3% Se-LMO.

[0098] Example 6

[0099] This embodiment provides a method for preparing a modified manganese-based positive electrode material, comprising the following steps:

[0100] (1) LiOH·H2O and MnCO3 in a molar ratio of 2:1.08 are put into a mortar and ground for 30 minutes until the grinding is uniform; the ground material is put into a crucible, placed in a muffle furnace, heated to 450°C at 5°C / min and kept at this temperature for 6 hours, then heated to 850°C at 5°C / min and kept at this temperature for 10 hours, and cooled with the furnace to obtain lithium manganate;

[0101] The difference between step (2) and step (2) of Example 3 is that the lithium nickel manganese oxide is replaced by the lithium manganese oxide prepared in step (1) of Example 6, and the other parameter conditions are the same as those of step (2) of Example 3;

[0102] Step (3) is the same as step (3) of Example 3, and the obtained modified manganese-based positive electrode material is recorded as 5% Se-LMO.

[0103] Comparative Example 1

[0104] This comparative example provides a method for preparing a lithium nickel manganese oxide positive electrode material, which is the same as step (1) of Example 2.

[0105] Comparative Example 2

[0106] This comparative example provides a method for preparing a lithium manganese oxide positive electrode material, which is the same as step (1) of Example 5.

[0107] The positive electrode materials obtained in Examples 4 to 6 and Comparative Example 2 were subjected to XRD testing. The results are as follows: Figure 2 As shown in A. Figure 2 From A in the figure, we can see that the modified lithium manganese oxide positive electrode material is the same as the original lithium manganese oxide positive electrode material, without the generation of secondary phase and impurity peaks, and all diffraction peaks point to the spinel standard card, belonging to the Fd3m space group, which is a standard lithium manganese oxide positive electrode material.

[0108] The positive electrode materials obtained in Examples 1 to 3 and Comparative Example 1 were subjected to XRD testing. The results are as follows: Figure 2 As shown in B. Figure 2 From B in FIG, it can be seen that the modified lithium nickel manganese oxide positive electrode material is consistent with the original lithium nickel manganese oxide positive electrode material, and no secondary phase and impurity peak are generated, indicating that doping does not affect the crystal structure of lithium nickel manganese oxide.

[0109] Application Examples 1 to 3, Comparative Application Example 1

[0110] (1) The positive electrode materials obtained in Examples 1 to 3 and Comparative Example 1, conductive carbon black (manufacturer Duoduo Chemical Reagent, model super C65) and PVDF (molecular weight 1 million) were mixed and ground at a mass ratio of 8:1:1 for 15 min, and NMP was added thereto and mixed to obtain a positive electrode slurry; the positive electrode slurry was uniformly coated on aluminum foil, and the loading amount was 4 mg·cm -2, drying, drying in a vacuum drying oven at 120°C for 12h, cutting to obtain a positive electrode sheet;

[0111] (2) The positive electrode sheet, lithium sheet, Celgard 2400 separator, and 5V high-voltage electrolyte (manufacturer Duoduo Chemical Reagent, brand LB-111) obtained in step (1) were assembled into CR2025 button-type batteries.

[0112] Application Examples 4 to 6, Comparative Application Example 2

[0113] (1) The positive electrode materials obtained in Examples 4 to 6 and Comparative Example 2, conductive carbon black (manufacturer Duoduo Chemical Reagent, model super C65) and PVDF (molecular weight 1 million) were mixed and ground for 15 min at a mass ratio of 8:1:1, and NMP was added thereto and mixed to obtain a positive electrode slurry; the positive electrode slurry was uniformly coated on aluminum foil, and the loading amount was 4 mg cm -2 , drying, drying in a vacuum drying oven at 80°C for 12h, cutting to obtain a positive electrode sheet;

[0114] (2) The positive electrode sheet, lithium sheet, Celgard 2400 separator, and 5V high-voltage electrolyte (manufacturer Duoduo Chemical Reagent, brand LB-111) obtained in step (1) were assembled into CR2025 button-type batteries.

[0115] The assembled batteries of Application Examples 1 to 6 and Comparative Application Examples 1 to 2 were placed in the blue power test system for cycle performance testing. The results are as follows: Figure 3 shown. Figure 3 A and B are the initial discharge specific capacities of the materials before and after modification. It can be seen that the discharge specific capacity of the modified material is almost the same as that of the original material. Figure 3 C and D in the figure are the cycle performance of the materials before and after modification. It can be seen that the modified positive electrode material has long cycle stability, which is much higher than the cycle retention rate of the original positive electrode material.

[0116] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a modified manganese-based positive electrode material, characterized in that: The following steps are involved: (1) mixing a manganese-based positive electrode material, a selenium source and an organic solvent, performing ultrasonic dispersion, and sequentially drying and ball milling the dispersion to obtain a modified manganese-based material precursor; (2) sintering the modified manganese-based material precursor described in step (1) to obtain a modified manganese-based positive electrode material; Wherein, in step (1), the manganese-based positive electrode material includes lithium manganese oxide or lithium nickel manganese oxide, and the selenium source includes selenium dioxide or selenium powder.

2. The preparation method according to claim 1, characterized in that: In step (1), the organic solvent includes ethanol.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), the mass of the selenium source is 1-5% of the mass of the manganese-based positive electrode material; the mass volume ratio of the manganese-based positive electrode material to the organic solvent is 4g:100-150mL.

4. The preparation method according to claim 3, characterized in that: In step (1), the frequency of the ultrasonic dispersion is 40 to 80 kHz, the power is 500 to 1000 W, and the time is 30 to 60 min.

5. The preparation method according to claim 1, characterized in that: In step (1), after ultrasonic dispersion, the process further comprises removing the organic solvent; the method for removing the organic solvent is water bath heating; the water bath heating temperature is 70 to 80° C., and the time is 3 to 5 hours.

6. The preparation method according to claim 4, characterized in that: In step (1), the rotation speed of the ball mill is 300-400 r / min, the time is 3-5 h, and the ball-to-material ratio is 1:10-20.

7. The preparation method according to claim 1 or 2, characterized in that: In step (1), the method for preparing the manganese-based positive electrode material comprises the following steps: mixing and grinding a lithium source and a manganese source, and sequentially performing a first sintering and a second sintering to obtain a manganese-based positive electrode material.

8. The preparation method according to claim 1 or 6, characterized in that: In step (2), the sintering temperature is 500-600° C., the time is 4-6 hours, and the rate of heating to the desired sintering temperature is 2-5° C. / min.

9. The modified manganese-based positive electrode material obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the modified manganese-based positive electrode material according to claim 9 in lithium-ion batteries.

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