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

Abstract

The application 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, sequentially performing drying and ball milling on the dispersion liquid to obtain a modified manganese-based material precursor; and sintering the modified manganese-based material precursor to obtain a modified manganese-based positive electrode material.The modified manganese-based positive electrode material provided by the application has significantly improved structural stability, can form a Mn-O-Se bond to enhance the structural stability of the material, relieve volume strain in the charging and discharging process, and inhibit the formation of material microcracks.Further, the electrode surface side reaction is suppressed, the capacity attenuation of the material caused by the interface side reaction can be effectively avoided, and the modified manganese-based positive electrode material has good long cycle stability.

Description

TECHNICAL FIELD

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

[0002] With the rapid development of society, the demand for energy and mineral resources and the awareness of protecting the natural environment have increased dramatically. Developing environmentally friendly, high-performance and low-cost energy storage devices has become the theme of today's society. In order to solve this problem, chemical power supply, a way of energy storage, has entered the public view. Chemical power supply uses the conversion between electrical energy and chemical energy to realize the storage and output of electrical energy, and has the technical characteristics of fast response and bidirectional regulation, and the technical advantages of strong environmental adaptability, small and dispersed configuration and short construction period. Among many chemical energy storage devices, lithium ion batteries (LIB) are considered to be one of the most promising energy storage devices and the most ideal energy storage power sources due to their high energy density, good charging efficiency, stable working voltage, environmental friendliness and long service life. Among them, manganese-based positive electrode materials have high working voltage, high energy density and 3D Li + diffusion channels. Moreover, manganese is considered to be one of the most promising lithium ion battery positive electrode materials due to its advantages of abundant resources, low cost and environmental friendliness. However, under high temperature conditions (55℃), the manganese-based positive electrode material will undergo a series of side reactions during the charging and discharging process, resulting in rapid decay of the electrochemical performance. First, LiPF6 and carbonates in the electrolyte have poor stability under high pressure, which will induce side reactions with the positive electrode material, resulting in capacity decay of the material, formation of a thick and uneven interface film on the material surface interface, and increase of the surface charge transfer resistance, hindering the transmission of lithium ions. Second, the by-products 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

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

[0004] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0005] The present application provides a preparation method of a modified manganese-based positive electrode material, comprising the following steps:

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

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

[0008] In step (1), the manganese-based positive electrode material comprises lithium manganate or lithium nickel manganate, and the selenium source comprises 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; and 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 40-80kHz, the power is 500-1000W, and the time is 30-60min.

[0012] Preferably, in the preparation method, in step (1), after the ultrasonic dispersion, the method further comprises removing the organic solvent; the removal of the organic solvent is achieved by water bath heating; the temperature of the water bath heating is 70-80℃, and the time is 3-5h.

[0013] Preferably, in the preparation method, in step (1), the rotation speed of the ball milling is 300-400r / min, the time is 3-5h, 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, sequentially performing first sintering and 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℃, the time is 4-6h, and the rate of increasing the temperature to the required sintering temperature is 2-5℃ / min.

[0016] The application further provides a modified manganese-based positive electrode material prepared by the preparation method.

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

[0018] According to the technical solution described above, compared with the prior art, the application has the following beneficial effects:

[0019] (1) The preparation method of the application combines ultrasonic dispersion and ball milling, and the organic solvent is evaporated by water bath heating after ultrasonic dispersion, so that the element selenium is more uniformly doped into the manganese-based positive electrode material, and the modified manganese-based positive electrode material is further synthesized by sintering.

[0020] (2) The structural stability of the modified manganese-based positive electrode material provided by the application is significantly improved. The modified positive electrode material can form Mn-O-Se bonds, enhance the structural stability of the material, relieve the volume strain in the charging and discharging process, and inhibit the formation of material microcracks. Moreover, the electrode surface side reaction is suppressed, which can effectively avoid the capacity attenuation of the material caused by the interface side reaction, 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 inhibit the corrosion of the electrolyte, promote the transmission of Li +

[0021] (3) The modified manganese-based positive electrode material provided by the application does not increase the cost of lithium ion battery preparation, and the production equipment involved is simple, the production cycle is short, the process is simple, and is suitable for large-scale production.

[0022] (4) The modification method of the application has wide adaptability and is suitable for lithium manganate, lithium nickel manganate, manganese-based positive electrode material, lithium cobaltate, ternary layered material or iron phosphate lithium positive electrode material, etc. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description.

[0024] Figure 1 It is a preparation process schematic diagram of the modified manganese-based positive electrode material.

[0025] Figure 2 It is an XRD diagram of the positive electrode material obtained in Examples 1-6 and Comparative Examples 1-2, wherein A is an XRD diagram of the positive electrode material obtained in Examples 4-6 and Comparative Example 2, and B is an XRD diagram of the positive electrode material obtained in Examples 1-3 and Comparative Example 1.

[0026] Figure 3 It is a cycle performance test result of the battery obtained in Application Examples 1-6 and Comparative Application Examples 1-2, wherein A is an initial discharge specific capacity diagram of Application Example 2 and Comparative Application Example 1, B is an initial discharge specific capacity diagram of Application Example 5 and Comparative Application Example 2, C is a cycle performance diagram of Application Examples 1-3 and Comparative Application Example 1, and D is a cycle performance diagram of Application Examples 4-6 and Comparative Application Example 2. DETAILED DESCRIPTION​

[0027] The application provides a preparation method of 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 performing drying and ball milling on the dispersion liquid to obtain a modified manganese-based material precursor;

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

[0030] In step (1), the manganese-based positive electrode material comprises lithium manganate or lithium nickel manganate, and the selenium source comprises selenium dioxide or selenium powder.

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

[0032] The selenium source is mixed with the organic solvent to perform ultrasonic dispersion, and the manganese-based positive electrode material is added to the obtained mixture to perform ultrasonic dispersion.

[0033] In the application, the manganese-based positive electrode material in step (1) is lithium manganate or lithium nickel manganate, and preferably is lithium nickel manganate.

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

[0035] In the application, the lithium source preferably comprises LiOH H2O or Li2CO3, and is further preferably LiOH H2O.

[0036] In the application, the manganese source preferably comprises MnCO3, Mn3O4, MnO2 or (Mn 1.5 Ni 0.5 )OH2 (nickel manganate hydroxide), and is further preferably MnCO3, MnO2 or (Mn 1.5 Ni 0.5 )OH2, and is more preferably MnCO3 or (Mn 1.5 Ni 0.5 )OH2.

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

[0038] In the application, the mixing and grinding conditions are not limited, and a scheme well known to those skilled in the art can be used.

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

[0040] In the present application, the temperature of the first sintering is preferably 400-500℃, further preferably 450-500℃, more preferably 480℃; the time is preferably 4-6h, further preferably 4-5h, more preferably 4h; the rate of heating to the required first sintering temperature is preferably 2-5℃ / min, further preferably 2-3℃ / min, more preferably 3℃ / min.

[0041] In the present application, the temperature of the second sintering is preferably 780-850℃, further preferably 800-850℃, more preferably 800℃; the time is preferably 10-14h, further preferably 10-13h, more preferably 13h; the rate of heating to the required second sintering temperature is preferably 2-5℃ / min, further preferably 2-3℃ / min, more preferably 3℃ / min.

[0042] In the present application, the selenium source of step (1) comprises selenium dioxide or selenium powder, preferably selenium powder.

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

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

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

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

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

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

[0049] In the present application, the temperature of the water bath heating is preferably 70-80℃, further preferably 70-75℃, and more preferably 75℃; and the time is preferably 3-5h, further preferably 4-5h, and more preferably 4h.

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

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

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

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

[0054] In the present application, the grinding ball used in the ball milling in step (1) is preferably a zirconium oxide grinding ball.

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

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

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

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

[0059] In the present application, the method for the application is not limited, and can be performed by using a method well known to those skilled in the art.

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

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

[0062] In the present application, the preparation method of the positive electrode sheet preferably comprises the following steps:

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

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

[0065] In the present application, the organic solvent is preferably N-methyl pyrrolidone (NMP).

[0066] In the present application, the mass ratio of the modified manganese-based positive electrode material, the conductive carbon black and the binder is not limited and can be determined by those skilled in the art. In the embodiments of the present application, 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 application, the mixing method is preferably grinding. The grinding time is preferably 15-30 min, further preferably 20-30 min, and more preferably 25 min.

[0068] In the present application, the drying temperature is preferably 80-120℃, further preferably 80-100℃, and more preferably 90℃; the time is preferably 10-12h, further preferably 11-12h, and more preferably 12h.

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

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

[0071] In the present application, the electrolyte is preferably a 5V high-voltage electrolyte (manufacturer: Duoduo Chemical Reagents, model: LB-111).

[0072] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0073] Example 1

[0074] The present embodiment provides a preparation method of a modified manganese-based positive electrode material, comprising the following steps, and the flow chart is as shown in Figure 1 ​

[0075] (1) Put LiOH H2O and (Mn 1.5 Ni 0.5 )OH2 with a molar ratio of 2:1 into a mortar and grind for 30 min, grind uniformly; Put the ground material into a crucible, place it in a muffle furnace, heat to 480℃ at a rate of 3℃ / min, keep for 4h, then heat to 780℃ at a rate of 3℃ / min, keep for 13h, cool with the furnace, get lithium nickel manganese oxide;

[0076] (2) Pour selenium powder into ethanol, place it in an ultrasonic tank for ultrasonic dispersion, the frequency of ultrasonic dispersion is 50kHz, the power is 1000W, the time is 30min, make the selenium powder uniformly dissolved in ethanol; Add lithium nickel manganese oxide to the obtained mixture and continue ultrasonic dispersion, the frequency of ultrasonic dispersion is 50kHz, the power is 1000W, the time is 30min, make the lithium nickel manganese oxide uniformly dispersed, wherein the mass of selenium powder is 3% of the mass of lithium nickel manganese oxide, the mass-volume ratio of lithium nickel manganese oxide to ethanol is 4g:100mL; Then, put the mixture obtained by ultrasonic dispersion into a 70℃ water bath for stirring for 4h until the ethanol is completely evaporated; Then, place the above material in a 110℃ vacuum drying oven and dry for 10h; Put the vacuum dried material into a ball mill tank (the grinding ball is zirconia grinding ball), ball mill in a planetary ball mill at a ball-material ratio of 1:10, a rotation speed of 350r / min for 3h, get the modified manganese-based material precursor;

[0077] (3) Pour the modified manganese-based material precursor of step (2) into a crucible and place it in a muffle furnace, heat to 550℃ at a rate of 2℃ / min, keep for 5h, cool to room temperature naturally, get the modified manganese-based positive electrode material, marked as 1%Se-LMNO.

[0078] Example 2

[0079] The embodiment provides a preparation method of a modified manganese-based positive electrode material, comprising the following steps:

[0080] (1) Put LiOH H2O and (Mn 1.5 Ni 0.5 )OH2 with a molar ratio of 2:1.05 into a mortar and grind for 30 min, grind uniformly; Put the ground material into a crucible, place it in a muffle furnace, heat to 500℃ at a rate of 2℃ / min, keep for 6h, then heat to 800℃ at a rate of 2℃ / min, keep for 13h, cool with the furnace, get lithium nickel manganese oxide;

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

[0082] (3) Pour the modified manganese-based material precursor of step (2) into a crucible and place it in a muffle furnace. Increase the temperature to 500℃ at a rate of 3℃ / min and maintain it for 5 h. Naturally cool it to room temperature to obtain a modified manganese-based positive electrode material, which is denoted as 3%Se-LMNO.

[0083] Example 3

[0084] The present embodiment provides a preparation method of a modified manganese-based positive electrode material, which comprises the following steps:

[0085] (1) Put LiOH·H2O and (Mn 1.5 Ni 0.5 )OH2 with a molar ratio of 2:1.08 into a mortar and grind them for 30 min until they are uniformly ground. Place the ground material in a crucible and place it in a muffle furnace. Increase the temperature to 450℃ at a rate of 5℃ / min and maintain it for 5 h. Then, increase the temperature to 850℃ at a rate of 5℃ / min and maintain it for 10 h. Cool it with the furnace to obtain lithium nickel manganese oxide.

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

[0087] (3) Put the modified manganese-based material precursor of step (2) into a crucible and place it in a muffle furnace, and heat it to 500℃ at a rate of 4℃ / min and keep it for 6h, and then naturally cool it to room temperature to obtain a modified manganese-based positive electrode material, which is recorded as 5%Se-LMNO.

[0088] Example 4

[0089] The present embodiment provides a preparation method of a modified manganese-based positive electrode material, comprising the following steps:

[0090] (1) Put LiOH·H2O and MnCO3 with a molar ratio of 2:1 into a mortar and grind for 30min until they are evenly ground; then put the ground materials into a crucible and place it in a muffle furnace, heat it to 500℃ at a rate of 2℃ / min, keep it for 4h, then heat it to 800℃ at a rate of 2℃ / min, keep it for 10h, and then cool it with the furnace to obtain lithium manganate;

[0091] Step (2) is different from step (2) of example 1 in that the lithium nickel manganate is replaced with lithium manganate prepared in step (1) of example 4, and other parameter conditions are the same as those in 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] The present embodiment provides a preparation method of a modified manganese-based positive electrode material, comprising the following steps:

[0095] (1) Put LiOH·H2O and MnCO3 with a molar ratio of 2:1.05 into a mortar and grind for 30min until they are evenly ground; then put the ground materials into a crucible and place it in a muffle furnace, heat it to 480℃ at a rate of 3℃ / min, keep it for 4h, then heat it to 780℃ at a rate of 3℃ / min, keep it for 13h, and then cool it with the furnace to obtain lithium manganate;

[0096] Step (2) is different from step (2) of example 2 in that the lithium nickel manganate is replaced with lithium manganate prepared in step (1) of example 5, and other parameter conditions are the same as those in 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] The present embodiment provides a preparation method of a modified manganese-based positive electrode material, comprising the following steps:

[0100] (1) LiOH·H2O and MnCO3 with a molar ratio of 2:1.08 were placed in a mortar and ground for 30 min until uniform. The ground material was placed in a crucible, placed in a muffle furnace, heated to 450℃ at 5℃ / min and held for 6 h, then heated to 850℃ at 5℃ / min and held for 10 h. The material was then cooled with the furnace to obtain lithium manganese oxide.

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

[0102] Step (3) is the same as step (3) in Example 3, and the resulting modified manganese-based cathode material is denoted as 5% Se-LMO.

[0103] Comparative Example 1

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

[0105] Comparative Example 2

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

[0107] The cathode materials obtained in Examples 4-6 and Comparative Example 2 were subjected to XRD analysis, and the results are as follows: Figure 2 As shown in A in the diagram. From Figure 2 As can be seen from A in the diagram, the modified lithium manganese oxide cathode material is the same as the original lithium manganese oxide cathode material, with no secondary phase or impurity peaks generated. All diffraction peaks point to the spinel standard card, belonging to the Fd3m space group, and are standard lithium manganese oxide cathode materials.

[0108] The cathode materials obtained in Examples 1-3 and Comparative Example 1 were subjected to XRD analysis, and the results are as follows: Figure 2 As shown in B in the diagram. (By...) Figure 2 As shown in B, the modified lithium nickel manganese oxide cathode material is consistent with the original lithium nickel manganese oxide cathode material, with no secondary phase or impurity peaks generated, indicating that doping does not affect the crystal structure of lithium nickel manganese oxide.

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

[0110] (1) The positive electrode materials obtained in Examples 1-3 and Comparative Example 1, conductive carbon black (manufacturer: Duoduo Chemical Reagent, model: Super C65) and PVDF (molecular weight 1 million) were mixed and ground for 15 min at a mass ratio of 8:1:1. NMP was added and the mixture was stirred to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated onto aluminum foil with a loading of 4 mg·cm³. -2, drying, drying at 120 DEG C in a vacuum drying oven for 12h, cutting to obtain the positive electrode sheet;

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

[0112] Application Examples 4-6 and Comparative Application Example 2

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

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

[0115] The batteries assembled in Application Examples 1-6 and Comparative Application Examples 1-2 are subjected to cycle performance tests in a blue electricity test system, and the results are shown in Table 1. Figure 3 Figure 3 A and B in Table 1 are the initial discharge specific capacities of the materials before and after modification, and 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 Table 1 are the cycle performances of the materials before and after modification, and 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 only describes preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.​

Claims

1. A method for preparing a modified manganese-based positive electrode material, characterized by, The method comprises the following steps: (1) 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 the dispersion liquid to obtain a modified manganese-based material precursor; (2) sintering the modified manganese-based material precursor of step (1) to obtain a modified manganese-based positive electrode material; In step (1), the manganese-based positive electrode material comprises lithium manganate or lithium nickel manganate, and the selenium source comprises selenium dioxide or selenium powder; in step (1), the organic solvent comprises ethanol; In step (1), the preparation method of the manganese-based positive electrode material comprises the following steps: mixing a lithium source and a manganese source, and sequentially performing first sintering and second sintering to obtain a manganese-based positive electrode material; The lithium source comprises LiOH·H2O or Li2CO3; The manganese source includes MnCO3, Mn3O4, MnO2or (Mn 1.5 Ni 0.5 )OH2; The first sintering is performed at a temperature of 400-500 DEG C for 4-6 h, and the temperature is raised to the required first sintering temperature at a rate of 2-5 DEG C / min; The second sintering is performed at a temperature of 780-850 DEG C for 10-14 h, and the temperature is raised to the required second sintering temperature at a rate of 2-5 DEG C / min; In step (1), the ultrasonic dispersion is performed at a frequency of 40-80 kHz and a power of 500-1000 W for 30-60 min; In step (1), after the ultrasonic dispersion, the organic solvent is removed; the removal of the organic solvent is performed by water bath heating; the water bath heating is performed at a temperature of 70-80 DEG C for 3-5 h; In step (1), the ball milling is performed at a speed of 300-400 r / min for 3-5 h, and the ball-to-material ratio is 1:10-20; In step (2), the sintering is performed at a temperature of 500-600 DEG C for 4-6 h, and the temperature is raised to the required sintering temperature at a rate of 2-5 DEG C / min.

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

3. The modified manganese-based positive electrode material prepared by the method of claim 1 or 2.

4. The application of the modified manganese-based positive electrode material of claim 3 in lithium ion batteries.

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