Lithium manganate positive electrode material and modification method thereof

Abstract

The application belongs to the technical field of lithium ion batteries, and provides a lithium manganate positive electrode material and a modification method thereof.Carbonic manganese and lithium carbonate are ball milled to obtain a mixture; the mixture is sequentially subjected to first sintering and second sintering to obtain an original lithium manganate positive electrode material; the original lithium manganate positive electrode material is mixed with a dispersing agent and then subjected to a hydrothermal reaction, and the precipitate obtained in the reaction is tempered to obtain the lithium manganate positive electrode material.The application adjusts the element distribution on the surface of the lithium manganate positive electrode material through the hydrothermal method, inhibits the loss of active components and the corrosion of electrolyte on the surface of the material, and reduces side reactions; the lithium manganate positive electrode material obtained has a good cycle retention rate, has a standard cubic spinel structure, and belongs to the Fd3m space group; and the modification method can realize recycling of resources, reduce environmental pollution, has low requirements on a synthesis device, is simple to operate, and is suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a lithium manganate positive electrode material and a modification method thereof. BACKGROUND

[0002] Among all energy storage materials, lithium ion batteries are the most potential new energy materials. In the development process of lithium ion batteries, the only limiting factor is that the positive electrode material of lithium ion batteries is relatively expensive. With the development of new energy industry, the prices of elements such as Li, Mn and Ni are becoming more and more expensive. The innovative research and optimization of the positive electrode material have become the research focus of lithium ion batteries.

[0003] Spinel lithium manganate positive electrode material has become one of the hot positive electrode materials due to its high working voltage, extremely stable structure and extremely rich resources. However, the spinel lithium manganate positive electrode material is limited in its wide application due to the rapid decay of its electrochemical performance caused by the active substance dissolution brought by its own J-T effect and manganese disproportionation reaction (2Mn 3+ (solid)→Mn 2+ (solid) + Mn 4+ (solution)).

[0004] Therefore, it has good application prospect to develop a modification method of lithium manganate positive electrode material which is simple to operate, low in cost and can obtain excellent electrochemical performance. SUMMARY

[0005] The present application aims at providing a lithium manganate positive electrode material and a modification method thereof to overcome the shortcomings of the prior art.

[0006] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0007] The present application provides a modification method of lithium manganate positive electrode material, comprising the following steps:

[0008] 1) Ball milling manganese carbonate and lithium carbonate to obtain a mixture;

[0009] 2) sequentially performing first sintering and second sintering on the mixture to obtain an original lithium manganate positive electrode material;

[0010] 3) mixing the original lithium manganate positive electrode material and a dispersing agent, then performing a hydrothermal reaction, and tempering the precipitate obtained in the reaction to obtain a lithium manganate positive electrode material.

[0011] Preferably, the molar ratio of manganese carbonate to lithium carbonate in step 1) is 2:1-1.1.

[0012] Preferably, the rotation speed of the ball milling in step 1) is 500-700 r / min, the ball milling time is 1-3 h, and the ball-to-material ratio is 1:9-11.

[0013] Preferably, the first sintering temperature in step 2) is 450-550℃, the first sintering time is 4-6 h; the second sintering temperature is 800-900℃, and the second sintering time is 11-13 h.

[0014] Preferably, the heating rate of the first sintering and the second sintering in step 2) is independently 1-3℃ / min; and the first sintering and the second sintering are carried out in an oxygen atmosphere.

[0015] Preferably, the dispersant in step 3) is water; and the mass-to-volume ratio of the original lithium manganate positive electrode material and the dispersant is 1 g:40-60 mL.

[0016] Preferably, the mixing speed in step 3) is 700-900 r / min, and the mixing time is 0.2-0.8 h.

[0017] Preferably, the hydrothermal reaction temperature in step 3) is 100-200℃, and the hydrothermal reaction time is 4-6 h.

[0018] Preferably, the tempering temperature in step 3) is 450-550℃, the tempering time is 4-6 h, the heating rate to the tempering temperature is 1-3℃ / min, and the tempering is carried out in an oxygen atmosphere.

[0019] The application also provides a lithium manganate positive electrode material prepared by the modification method.

[0020] The application has the following advantages:

[0021] 1) The application adjusts the element distribution on the surface of the lithium manganate positive electrode material (Mn 3+ / Mn 4+ ratio, 4H + +2LiMn2O4=3MnO2+Mn 2+ +2Li + +2H2O) through the hydrothermal method, inhibits the loss of active components and the corrosion of electrolyte on the material surface, and reduces the side reactions; and different surface structure modified lithium manganate positive electrode materials are obtained by controlling the temperature.

[0022] 2) The lithium manganate positive electrode material has a high discharge specific capacity, which can reach 121.0 mAh·g -1 ; and the cycle retention rate after 200 cycles is still 105.8 mAh·g -1 , which is much higher than the discharge specific capacity and cycle retention rate of the original lithium manganate positive electrode material.

[0023] 3) The lithium manganate positive electrode material of the present application has a standard cubic spinel structure and belongs to the Fd3m space group.

[0024] 4) The modification method of the lithium manganate positive electrode material can realize recycling of resources, reduce environmental pollution, has low requirements on the synthesis equipment, is simple to operate, and is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 XRD patterns of the original lithium manganate positive electrode material of Example 1 and the lithium manganate positive electrode materials of Examples 1-3;

[0026] Figure 2 SEM images of the original lithium manganate positive electrode material of Example 1 and the lithium manganate positive electrode material of Example 2, wherein (A) is the SEM image of the original lithium manganate positive electrode material of Example 1, and (B) is the SEM image of the lithium manganate positive electrode material of Example 2;

[0027] Figure 3 Cycle performance curves of the original lithium manganate positive electrode material of Example 1 and the lithium manganate positive electrode material of Example 2. DETAILED DESCRIPTION

[0028] The present application provides a modification method of a lithium manganate positive electrode material, comprising the following steps:

[0029] 1) Ball milling manganese carbonate and lithium carbonate to obtain a mixture;

[0030] 2) sequentially performing first sintering and second sintering on the mixture to obtain an original lithium manganate positive electrode material;

[0031] 3) mixing the original lithium manganate positive electrode material and a dispersant, then performing hydrothermal reaction, tempering the precipitate obtained by the reaction, and obtaining a lithium manganate positive electrode material.

[0032] In the present application, the manganese carbonate and lithium carbonate in step 1) are preferably analytically pure substances.

[0033] In the present application, the molar ratio of the manganese carbonate and lithium carbonate in step 1) is preferably 2:1-1.1, further preferably 2:1.02-1.08, and more preferably 2:1.04-1.06.

[0034] In the present application, the rotation speed of the ball milling in step 1) is preferably 500-700 r / min, further preferably 550-650 r / min, and more preferably 600 r / min; the ball milling time is preferably 1-3 h, further preferably 1.5-2.5 h, and more preferably 2 h; and the ball-to-material ratio of the ball milling is preferably 1:9-11, further preferably 1:9.5-10.5, and more preferably 1:10.

[0035] In the present application, the temperature of the first sintering in step 2) is preferably 450-550℃, further preferably 480-520℃, and more preferably 500℃; the first sintering time is preferably 4-6 h, further preferably 4.5-5.5 h, and more preferably 5 h; the temperature of the second sintering is preferably 800-900℃, further preferably 820-880℃, and more preferably 840-860℃; and the second sintering time is preferably 11-13 h, further preferably 11.5-12.5 h, and more preferably 12 h.

[0036] In the present application, the heating rate of the first sintering and the second sintering in step 2) is independently preferably 1-3℃ / min, further preferably 1.5-2.5℃ / min, and more preferably 2℃ / min; and the first sintering and the second sintering are preferably performed in an oxygen atmosphere.

[0037] In the present application, after the second sintering in step 2) is completed, the obtained product is preferably cooled, and the cooling temperature is preferably 20-30℃, further preferably 22-28℃, and more preferably 24-26℃.

[0038] In the present application, the dispersant in step 3) is preferably water; and the mass-to-volume ratio of the original lithium manganate positive electrode material to the dispersant is preferably 1 g:40-60 mL, further preferably 1 g:45-55 mL, and more preferably 1 g:50 mL.

[0039] In the present application, the mixing speed in step 3) is preferably 700-900 r / min, further preferably 750-850 r / min, and more preferably 800 r / min; and the mixing time is preferably 0.2-0.8 h, further preferably 0.3-0.6 h, and more preferably 0.4-0.5 h.

[0040] In the present application, the temperature of the hydrothermal reaction in step 3) is preferably 100-200℃, further preferably 120-180℃, and more preferably 140-160℃; and the hydrothermal reaction time is preferably 4-6 h, further preferably 4.5-5.5 h, and more preferably 5 h.

[0041] In the present application, the precipitate in step 3) is preferably a precipitate sequentially subjected to washing and drying, the washing reagent is preferably ultrapure water, the drying temperature is preferably 70-90℃, further preferably 75-85℃, more preferably 80℃, and the drying time is preferably 22-26h, further preferably 23-25h, more preferably 24h.

[0042] In the present application, the temperature for tempering in step 3) is preferably 450-550℃, further preferably 480-520℃, more preferably 500℃, the tempering time is preferably 4-6h, further preferably 4.5-5.5h, more preferably 5h, the heating rate to the tempering temperature is preferably 1-3℃ / min, further preferably 1.5-2.5℃ / min, more preferably 2℃ / min, and the tempering is preferably performed in an oxygen atmosphere.

[0043] The present application also provides a lithium manganate positive electrode material prepared by the modification method.

[0044] The technical solutions provided by the present application are described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0045] Example 1

[0046] 2 mol of manganese carbonate (analytical pure) and 1 mol of lithium carbonate (analytical pure) were ball milled in a ball mill with a rotation speed of 600 r / min for 2h at a ball-to-material ratio of 1:10 (the milling balls were zirconia balls), to obtain a mixture; the mixture was placed in a crucible and then put into a tube furnace filled with oxygen, the tube furnace was heated to 500℃ at a rate of 2℃ / min, sintered at 500℃ for 5h, then the tube furnace was heated to 800℃ at a rate of 2℃ / min, sintered at 800℃ for 12h, and the product was cooled to 20℃, to obtain a raw lithium manganate positive electrode material.

[0047] 1g of the raw lithium manganate positive electrode material and 50mL of ultrapure water were placed in the inner liner of a high-pressure reaction kettle, then mixed on a magnetic stirrer with a speed of 800r / min for 0.5h, then transferred to the outer liner of the high-pressure kettle, and subjected to hydrothermal reaction in a forced air drying oven at a temperature of 100℃ for 5h; after the reaction, the obtained precipitate was washed with ultrapure water, and then dried in a forced air drying oven at a temperature of 80℃ for 24h; the dried precipitate was placed in a tube furnace filled with oxygen, the tube furnace was heated to 500℃ at a rate of 2℃ / min, and then tempered at 500℃ for 5h, to obtain a lithium manganate positive electrode material.

[0048] Example 2

[0049] 2 mol of manganese carbonate (analytical grade) and 1.05 mol of lithium carbonate (analytical grade) were ball-milled at 500 r / min for 1 h at a ball-to-material ratio of 1:9 (using zirconia balls) to obtain a mixture. The mixture was placed in a crucible and then placed in a tube furnace filled with oxygen. The temperature of the tube furnace was increased to 450 °C at a rate of 1 °C / min, and sintered at 450 °C for 4 h. Then, the temperature of the tube furnace was increased to 850 °C at a rate of 1 °C / min, and sintered at 850 °C for 11 h. The product was cooled to 25 °C to obtain the original lithium manganese oxide cathode material.

[0050] 1g of raw lithium manganese oxide cathode material and 40mL of ultrapure water were placed in the liner of a high-pressure reactor and mixed for 0.2h on a magnetic stirrer at 700r / min. The mixture was then transferred to the outer liner of the high-pressure reactor and hydrothermally reacted in a forced-air drying oven at 150℃ for 4h. After the reaction, the precipitate was washed with ultrapure water and dried in a forced-air drying oven at 70℃ for 22h. The dried precipitate was then placed in a tube furnace filled with oxygen and heated to 450℃ at a rate of 1℃ / min. The furnace was then tempered at 450℃ for 6h to obtain the lithium manganese oxide cathode material.

[0051] Example 3

[0052] 2 mol of manganese carbonate (analytical grade) and 1.1 mol of lithium carbonate (analytical grade) were ball-milled at 700 r / min for 3 h at a ball-to-material ratio of 1:11 (using zirconia balls) to obtain a mixture. The mixture was placed in a crucible and then placed in a tube furnace filled with oxygen. The temperature of the tube furnace was increased to 550 °C at a rate of 3 °C / min, and sintered at 550 °C for 6 h. Then, the temperature of the tube furnace was increased to 900 °C at a rate of 3 °C / min, and sintered at 900 °C for 13 h. The product was cooled to 30 °C to obtain the original lithium manganese oxide cathode material.

[0053] 1g of raw lithium manganese oxide cathode material and 60mL of ultrapure water were placed in the liner of a high-pressure reactor and mixed for 0.8h on a magnetic stirrer at 900r / min. The mixture was then transferred to the outer liner of the high-pressure reactor and hydrothermally reacted in a forced-air drying oven at 200℃ for 6h. After the reaction, the precipitate was washed with ultrapure water and dried in a forced-air drying oven at 90℃ for 26h. The dried precipitate was then placed in a tube furnace filled with oxygen and heated to 550℃ at a rate of 3℃ / min. The furnace was then tempered at 550℃ for 4h to obtain the lithium manganese oxide cathode material.

[0054] The original lithium manganese oxide cathode material of Example 1 ( Figure 1 The XRD patterns of the original sample and the lithium manganese oxide cathode materials of Examples 1-3 are shown in the figure. Figure 1 As shown, byFigure 1 It can be seen that the lithium manganese oxide cathode material is the same as the original lithium manganese oxide cathode material. There is no secondary phase or impurity peak formation. All diffraction peaks point to the spinel LiMn2O4 standard card (JCPDS35-0782), which belongs to the Fd3m space group and is a standard lithium manganese oxide cathode material.

[0055] SEM images of the original lithium manganese oxide cathode material in Example 1 and the lithium manganese oxide cathode material in Example 2 are shown below. Figure 2 As shown, (A) is a SEM image of the original lithium manganese oxide cathode material of Example 1, and (B) is a SEM image of the lithium manganese oxide cathode material of Example 2. Figure 2 It can be seen that both the original lithium manganese oxide cathode material and the lithium manganese oxide cathode material have a polyhedral structure of 400-800nm, and the particle surface is smooth with no impurity particles attached.

[0056] The original lithium manganese oxide cathode material from Example 1 was used respectively. Figure 3 The original sample and the lithium manganese oxide cathode material from Example 2 were mixed with conductive carbon and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1 and coated onto an aluminum foil with a thickness of 200 nm. The mixture was then dried in a vacuum drying oven at 120°C and 0.08 MPa for 12 hours to obtain the electrode sheet. The electrode sheet was then assembled with lithium to form a 2025 coin cell. The assembled battery was then placed in a Blue Electric testing system for cycle performance testing. The cycle performance curve is shown in the figure. Figure 3 As shown, by Figure 3 It can be seen that lithium manganese oxide cathode material has a high discharge specific capacity, reaching 121.0 mAh·g. -1 After 200 cycles, the cycle retention rate still reached 105.8 mAh·g. -1 It is far superior to the discharge specific capacity and cycle retention rate of the original lithium manganese oxide cathode material.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for modifying lithium manganese oxide cathode material, characterized in that, It includes the following steps: 1) Manganese carbonate and lithium carbonate were ball-milled to obtain a mixture; 2) The mixture is subjected to a first sintering and a second sintering in sequence to obtain the original lithium manganese oxide cathode material; 3) The original lithium manganese oxide cathode material and dispersant are mixed and subjected to hydrothermal reaction. The precipitate obtained from the reaction is then tempered to obtain the lithium manganese oxide cathode material. In step 1), the molar ratio of manganese carbonate to lithium carbonate is 2:1 to 1.

1. Step 3) The tempering temperature is 450-550℃, the tempering time is 4-6h, the rate of heating to the tempering temperature is 1-3℃ / min, and the tempering is carried out in an oxygen atmosphere.

2. The modification method according to claim 1, characterized in that, Step 1) The ball milling speed is 500-700 r / min, the ball milling time is 1-3 h, and the ball-to-material ratio is 1:9-11.

3. The modification method according to claim 2, characterized in that, Step 2) The temperature of the first sintering is 450-550℃ and the time of the first sintering is 4-6h; the temperature of the second sintering is 800-900℃ and the time of the second sintering is 11-13h.

4. The modification method according to claim 3, characterized in that, Step 2) The heating rates of the first sintering and the second sintering are independent, ranging from 1 to 3 °C / min; the first sintering and the second sintering are carried out in an oxygen atmosphere.

5. The modification method according to claim 4, characterized in that, Step 3) The dispersant is water; the mass-to-volume ratio of the original lithium manganese oxide cathode material to the dispersant is 1g:40-60mL.

6. The modification method according to claim 5, characterized in that, The mixing speed in step 3) is 700-900 r / min, and the mixing time is 0.2-0.8 h.

7. The modification method according to claim 6, characterized in that, The hydrothermal reaction in step 3) is carried out at a temperature of 100–200°C for 4–6 hours.

8. The lithium manganese oxide cathode material prepared by the modification method according to any one of claims 1 to 7.

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