EMD graphite composite positive electrode material and preparation method thereof

Abstract

The invention discloses an EMD graphite composite positive electrode material and a preparation method thereof, and particularly relates to the technical field of alkaline manganese batteries. The method comprises the following steps: carrying out ball milling, adding graphite in an EMD grinding process, carrying out grinding and mixing treatment, fully mixing the grinding ball with the graphite while the grinding ball becomes fine through EMD grinding under the conditions of proper grinding ball proportion and grinding, and carrying out low-speed neutralization and drying after the mixing treatment is finished, so as to obtain the EMD graphite composite positive electrode material. Compared with a positive electrode material obtained by mechanically mixing an EMD product and graphite, the EMD graphite composite positive electrode material obtained by the grinding and mixing treatment technology has the advantage that the electric capacity of a battery prepared from the EMD graphite composite positive electrode material is higher than that of an existing mechanically-mixed sample.

Description

Technical Field

[0001] The invention relates to the technical field of alkaline manganese batteries, and in particular to an EMD graphite composite positive electrode material and a preparation method thereof. Background Art

[0002] Most of EMD will be used as positive electrode material for alkaline manganese batteries. In the process of making EMD into positive electrode material, it is often necessary to mix it with graphite. However, the density of EMD is quite different from that of graphite. Therefore, in the commonly used mechanical stirring and mixing process, EMD and graphite often cannot achieve the best mixing effect. Graphite often floats to the upper layer of the material instead of being evenly wrapped on the surface of EMD, which will cause uneven mixing of the overall material. This will lead to low EMD utilization in the battery, a certain amount of EMD waste, and battery performance will also be affected.

[0003] Under the existing technology, EMD and graphite are mixed after the EMD production process is completed and during the battery production process. Since EMD has completed the crushing process, in order to ensure that the optimal particle size is not destroyed, it is difficult to use a more powerful mixing technology during the mixing of graphite and EMD, so that graphite and EMD are only dispersed, and the dispersion effect is very limited.

[0004] Chinese patent CN117038950A, a mixing method based on graphene and manganese dioxide and its device, the above-mentioned mixing method based on graphene and manganese dioxide includes the following steps: preparing graphene-carbon black composite powder. The graphene-carbon black composite powder and manganese dioxide are added to the mixing chamber of the mixing device respectively for mixing and stirring operations to obtain graphene-manganese dioxide composite powder. Wherein, during the mixing and stirring operation, the mixing chamber is blown. During the mixing and stirring operation, the mixing chamber is atomized. However, this patent mainly mixes graphene with manganese dioxide to obtain a graphene-manganese dioxide composite powder; this patent is carried out with finished manganese dioxide powder and graphene, but we are doing it in the grinding process of manganese dioxide production, not the finished manganese dioxide powder used. In addition, the patent also involves preparing a suspension of carbon black and graphene and re-drying, as well as atomized air flow mixing, which is more complicated in operation and process than the mechanical stirring process commonly used in the current alkaline manganese battery industry. Summary of the invention

[0005] To this end, the present invention provides an EMD graphite composite positive electrode material and a preparation method thereof to solve the above-mentioned problems.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] According to one aspect of the present invention, a method for preparing an EMD graphite composite positive electrode material is provided, the method comprising: adding graphite during the EMD grinding process, grinding and mixing by ball milling, fully mixing the EMD with the graphite while the EMD is ground into finer pieces, and after the mixing process is completed, performing low-speed neutralization and drying to obtain the EMD graphite composite positive electrode material.

[0008] Furthermore, the grinding frequency is 50 Hz to 150 Hz. If it is lower than 50 Hz, the EMD cannot be smoothly ground into powder, and the grinding efficiency is low; if it is higher than 150 Hz, the graphite structure will be destroyed due to excessive grinding intensity; the performance of the EMD will also be damaged due to intense grinding and excessive grinding temperature.

[0009] Furthermore, the grinding time is 300s to 1800s. If it is less than 300s, the grinding effect of EMD is poor, and the particle size is too coarse to be screened smoothly; if it is more than 1800s, the grinding effect is too strong, and the EMD particles are too fine, which affects the compaction density.

[0010] Furthermore, the ratio of the mass of the grinding balls to the mass of the EMD in the ball mill should be 2-6: 1. If it is lower than 2: 1, the amount of EMD added is too much, the grinding effect is poor, and the particle size is coarse; if it is higher than 6: 1, the amount of EMD added is too little, the production efficiency is too low, and the particle size is fine.

[0011] Furthermore, the grinding balls of the ball mill are selected to be mixed in 5 specifications, namely φ15, φ12, φ9, φ5, and φ2; mm.

[0012] Furthermore, the ratio of the grinding balls φ15, φ12, φ9, φ5 and φ2 of the ball mill is: 1-3:3-5:7-9:12-17:100-300.

[0013] Furthermore, the grinding medium loading accounts for 20-80% of the volume of the ball mill cylinder, and more preferably, the grinding medium loading accounts for 20-50% of the volume of the ball mill cylinder.

[0014] Furthermore, the grinding medium loading amount of the planetary mill is: V=φVt; wherein V is the actual loading volume of the grinding medium, φ is the loading coefficient, φ is between 0.2-0.5, and Vt is the effective volume of the ball mill cylinder.

[0015] Furthermore, the calculation formula of the effective volume Vt of the cylinder is: Vt = π (D 2 / 4-d 2 )L; D is the inner diameter of the ball mill cylinder, d is the shaft diameter of the ball mill (this needs to be considered if there is a shaft occupying space such as center feeding), and L is the length of the ball mill cylinder.

[0016] Furthermore, the amount of graphite added is 1-3% of the EMD content.

[0017] Furthermore, the low-speed neutralization stirring speed is 100-600 rpm. If it is lower than 100 rpm, the stirring intensity is too low, which is not conducive to the neutralization reaction of hydrogen ions; if it is higher than 600 rpm, the stirring intensity is too high, which will cause the EMD to separate from the graphite.

[0018] After EMD is ground and mixed with graphite, it is already a mixture of EMD and graphite. However, the ground EMD still needs to be neutralized. If the stirring intensity is too high during the neutralization process, there is a high probability that the EMD and graphite will be separated due to excessive centrifugal force, causing the graphite coated on the surface of the EMD to be separated. Therefore, this technology also makes some improvements to the neutralization process, appropriately reducing the stirring intensity to prevent a large amount of separation of EMD and graphite.

[0019] According to another aspect of the present invention, an EMD graphite composite positive electrode material is provided, and the positive electrode material is prepared by the above method.

[0020] The present invention has the following advantages:

[0021] Under the same battery formula, the EMD graphite composite positive electrode material obtained by the grinding and mixing processing technology of the present invention is compared with the positive electrode material obtained by mechanically mixing the EMD product and graphite. The capacity of the battery made by the positive electrode material is higher than that of the existing mechanically mixed samples.

[0022] The EMD positive electrode material prepared by the present invention is more suitable for the alkaline manganese battery industry, improves the utilization rate of EMD, and improves the performance of the battery. DETAILED DESCRIPTION

[0023] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0024] Example 1

[0025] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1% of graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 50Hz, the grinding time is 1800s, the grinding ball mass is 300g, the filling rate is 20%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 2:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 100rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0026] Example 2

[0027] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1.5% of graphite during the grinding process of 100g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 115Hz, the grinding time is 600s, the grinding ball mass is 300g, the filling rate is 25%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 3:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 200rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0028] Example 3

[0029] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 3% graphite during the grinding process of 50g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 130Hz, the grinding time is 400s, the grinding ball mass is 300g, the filling rate is 20%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 6:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 400rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0030] Example 4

[0031] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 2.5% of graphite during the grinding process of 80g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 150Hz, the grinding time is 300s, the grinding ball mass is 300g, the filling rate is 25%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 4:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 600rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0032] Example 5

[0033] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1% of graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 50Hz, the grinding time is 1800s, the grinding ball mass is 600g, the filling rate is 50%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 2:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 100rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0034] Example 6

[0035] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1.5% graphite during the grinding process of 200g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 115Hz, the grinding time is 600s, the grinding ball mass is 600g, the filling rate is 60%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 3:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 200rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0036] Example 7

[0037] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 2% graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 115Hz, the grinding time is 900s, the grinding ball mass is 600g, the filling rate is 50%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 4:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 200rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0038] Example 8

[0039] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 3% graphite during the grinding process of 300g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 150Hz, the grinding time is 600s, the grinding ball mass is 600g, the filling rate is 80%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 2:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 600rpm and a drying temperature of 60°C to obtain an EMD graphite composite positive electrode material.

[0040] Comparative Example 1

[0041] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1% of graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 45Hz, the grinding time is 1800s, the grinding ball mass is 300g, the filling rate is 20%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 2:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 100rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0042] Comparative Example 2

[0043] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1% of graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 200Hz, the grinding time is 1800s, the grinding ball mass is 300g, the filling rate is 20%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 2:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 100rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0044] Comparative Example 3

[0045] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1% of graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 50Hz, the grinding time is 1900s, the grinding ball mass is 300g, the filling rate is 20%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 2:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 100rpm and a drying temperature of 60°C to obtain an EMD graphite composite positive electrode material.

[0046] Comparative Example 4

[0047] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1% of graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 150Hz, the grinding time is 250s, the grinding ball mass is 300g, the filling rate is 20%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 2:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 100rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0048] Comparative Example 5

[0049] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1% of graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 50Hz, the grinding time is 1800s, the grinding ball mass is 600g, the filling rate is 50%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 4:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 100rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0050] Comparative Example 6

[0051] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1% of graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 50Hz, the grinding time is 1200s, the grinding ball mass is 600g, the filling rate is 50%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 4:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 100rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0052] Comparative Example 7

[0053] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1% of graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 150Hz, the grinding time is 1800s, the grinding ball mass is 600g, the filling rate is 50%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 4:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 80rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0054] Comparative Example 8

[0055] This embodiment 1 provides a preparation method of an EMD graphite composite positive electrode material, the method comprising: adding 1% of graphite during the grinding process of 150g of EMD, grinding and mixing with a planetary mill, the grinding frequency is 150Hz, the grinding time is 1800s, the grinding ball mass is 600g, the filling rate is 50%, and the ratio of the grinding ball mass to the EMD mass in the planetary mill should be 4:1; while the EMD is ground into fine particles, it is fully mixed with the graphite, and after the mixing treatment is completed, low-speed neutralization stirring is performed at a speed of 650rpm and a drying temperature of 60°C to obtain the EMD graphite composite positive electrode material.

[0056] Comparative Example 9

[0057] Conventional EMD products on the market add 10% graphite and are directly mixed mechanically to obtain positive electrode materials.

[0058] Experimental Example 1

[0059] The materials of Examples 1-8 and Comparative Examples 1-9 were ground and mixed, then passed through a 60-mesh sieve, neutralized and dried at a low speed, and then mixed and granulated. During granulation, graphite was added to 6% of the total mass. After granulation by a granulator, the positive electrode sheets were made by a tablet press to make button batteries for various tests. The obtained data are shown in Table 1.

[0060] Table 1

[0061]

[0062]

[0063] As can be seen from Table 1, 600g grinding ball + 150g EMD performed best, and the neutralization stirring speed of 200rpm performed best. At other speeds, the carbon content and conductivity decreased to varying degrees.

[0064] The finer the EMD is ground, the higher the resistance will be, the capacitance will increase slightly, the compaction density will increase, and the screening rate will also increase. The carbon content after neutralization is mainly related to the stirring rate. This indicator is tested by the carbon sulfur instrument. The faster the stirring rate, the more graphite is lost and the lower the carbon content will be; but if the stirring rate is too low, the neutralization degree is insufficient, the hydrogen ion content in the EMD is too high, and the capacitance will be affected.

[0065] If the grinding frequency is lower than 50Hz, EMD cannot be ground into powder smoothly; if it is higher than 150Hz, the graphite structure will be destroyed due to excessive grinding intensity; EMD will also be damaged due to severe grinding performance;

[0066] When the grinding time is less than 300s, the grinding effect of EMD is poor, and the particle size is too coarse to be screened smoothly; when the grinding time is more than 1800s, the grinding effect is too strong, and the EMD particles are too fine, which affects the compaction density;

[0067] When the ratio of the mass of grinding balls to the mass of EMD in the planetary mill is lower than 2:1, too much EMD is added, the grinding effect is poor, and the particle size is coarse; when it is higher than 6:1, too little EMD is added, the production efficiency is too low, and the particle size is fine.

[0068] During the neutralization process, if the stirring speed is lower than 100 rpm, the stirring intensity is too low, which is not conducive to the neutralization reaction of hydrogen ions; if it is higher than 600 rpm, the stirring intensity is too high, which will cause the EMD to separate from the graphite.

[0069] Conductivity is shown by resistance. The stronger the conductivity, the lower the resistance. Under other conditions, the higher the utilization rate of EMD, the greater the capacity. The compaction density is generally related to the amount of graphite added. The more graphite is added, the lower the compaction density. The alkaline manganese battery industry requires products with higher compaction density.

[0070] The present invention limits the ratio of graphite to EMD and the parameters selected for ball milling, and finally obtains a positive electrode material that is a graphite composite EMD positive electrode material. This has lower resistance and higher compaction density than a manganese dioxide / graphite nanosheet composite in which manganese dioxide particles are uniformly dispersed on the surface of graphite nanosheets, and is more suitable for the alkaline manganese battery industry.

[0071] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for preparing an EMD graphite composite positive electrode material, characterized in that: The method comprises: during the EMD grinding process, adding a certain amount of graphite during the grinding process, using a ball mill for grinding and mixing treatment, and by controlling the grinding conditions, while the EMD is ground to be fine, fully mixing with the graphite, and after the mixing treatment is completed, performing low-speed neutralization and drying to obtain the EMD graphite composite positive electrode material.

2. The method for preparing an EMD graphite composite positive electrode material according to claim 1, characterized in that: The grinding frequency is 50 Hz to 150 Hz.

3. The method for preparing an EMD graphite composite positive electrode material according to claim 1, characterized in that: The grinding time is 300s to 1800s.

4. The method for preparing an EMD graphite composite positive electrode material according to claim 1, characterized in that: The ratio of the mass of the grinding balls to the mass of the EMD in the ball mill should be 2-6:

1.

5. The method for preparing an EMD graphite composite positive electrode material according to claim 1, characterized in that: The grinding balls of the ball mill are selected to be mixed in 5 specifications, namely φ15, φ12, φ9, φ5, and φ2; mm.

6. The method for preparing an EMD graphite composite positive electrode material according to claim 5, characterized in that: The ratio of the grinding balls of the ball mill is φ15, φ12, φ9, φ5 and φ2 is: 1-3:3-5:7-9:12-17:100-300.

7. The method for preparing an EMD graphite composite positive electrode material according to claim 1, characterized in that: The grinding medium filling amount accounts for 20-80% of the volume of the planetary mill cylinder.

8. The method for preparing an EMD graphite composite positive electrode material according to claim 1, characterized in that: The graphite addition amount is 1-3% of the EMD content.

9. The method for preparing an EMD graphite composite positive electrode material according to claim 1, characterized in that: The low-speed neutralization stirring speed is 100-600 rpm.

10. An EMD graphite composite positive electrode material, characterized in that: The positive electrode material is prepared by any method of claims 1-9.

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