EMD wet grinding preparation process and application

Abstract

The invention discloses an EMD wet grinding preparation process and application, and particularly relates to the technical field of alkaline manganese battery materials. The process comprises the following steps: taking a first part of EMD, adding water, carrying out wet grinding, screening, neutralizing, drying, and mixing with a second part of EMD to obtain an EMD mixed sample. According to the present invention, the heat generated during the grinding process is absorbed by using the specific heat capacity of water through the wet grinding manner, such that the grinding temperature is reduced compared with the dry grinding, and the OCV heat attenuation is weakened so as to obtain the EMD product with the high OCV.

Description

Technical Field

[0001] The invention relates to the technical field of alkaline manganese battery materials, and in particular to an EMD wet grinding preparation process and application. Background Art

[0002] EMD is an important raw material in the alkaline manganese battery industry, and open circuit voltage (OCV) is one of the important parameters of EMD. There are many factors that affect OCV, one of which is thermal attenuation. In the current EMD production process, after EMD is generated by electrolytic reaction, it will be peeled off first, and then the peeled EMD sheets will be ground into fine powder, and then neutralized and dried to obtain the finished product. In the process of grinding into fine powder, EMD will cause the OCV to decay due to collision and friction with the grinding roller and itself during grinding. Data show that the change in the open circuit voltage of EMD before and after grinding is reduced by about 20 millivolts. To this end, a grinding method that slows down the attenuation of OCV is designed, but one of the reasons for the attenuation of OCV is the increase in temperature, and dry grinding will inevitably cause the grinding process temperature to be too high, which in turn affects the quality of the product.

[0003] Chinese patent CN106604893A, a method for preparing electrolytic manganese dioxide with high compaction density, wherein electrolytic manganese dioxide fragments are ground in a graded mill to produce first ground manganese dioxide particles, wherein 30% of the particles are larger than 200 mesh, and up to 95% of the particles are smaller than 325 mesh. The first ground manganese dioxide particles are ground a second time to produce manganese dioxide particles with a second particle size distribution. However, this patent requires graded grinding, which is time-consuming and labor-intensive, and the preparation method is complicated, and does not utilize subsequent industrial mass production.

[0004] Chinese patent CN115663170A discloses a modified electrolytic manganese dioxide, a preparation method thereof and an alkaline manganese battery, wherein the preparation method comprises the following steps: (1) mixing electrolytic manganese dioxide, a group IIA compound and a conductive agent, and performing a first grinding to obtain a mixture; (2) sintering the obtained mixture, and performing a second grinding to obtain the modified electrolytic manganese dioxide. However, the patent still uses dry grinding and mixing, which cannot avoid the problems existing in dry grinding. Summary of the invention

[0005] To this end, the present invention provides an EMD wet grinding preparation process and application to solve the above-mentioned problems.

[0006] The particle size distribution (PSD) of the EMD fine powder produced by wet grinding is narrower than that produced by dry grinding. In the subsequent process of making batteries, EMD must be mechanically stamped into positive electrode rings. The distribution of PSD will directly affect the filling of solid particles, and therefore also affect the compaction density, strength and liquid absorption of the positive electrode ring, and these parameters are closely related to the capacity of the battery. However, the EMD fine powder after wet grinding does not have an advantage in compaction density because its distribution range is too narrow. By comparing the PSD of wet grinding and conventional dry grinding, and mixing EMD fine powder of other particle sizes with the wet-ground EMD mixed sample in a certain proportion, an EMD wet-ground mixed sample is obtained. Compared with the conventional dry-ground EMD mixed sample, the EMD sample of the present invention has significantly improved various performances, and the compaction density index has not been attenuated.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] According to the first aspect of the present invention, a wet grinding preparation process for EMD is provided, which comprises: first taking a first part of EMD, adding water to wet grind, and then screening, neutralizing, and drying, and then mixing with a second part of EMD to obtain an EMD mixed sample.

[0009] The present invention adopts wet grinding to grind EMD into fine powder. On the basis of the original grinding process, a certain amount of distilled water is added to absorb the heat generated during the grinding process to prevent the temperature from being too high, thereby reducing the thermal attenuation of OCV.

[0010] The fine powder of EMD after wet grinding of the present invention has a narrower distribution range of PSD than that of dry grinding, when other conditions remain unchanged. And the particle size is also different with different grinding time. The present invention first makes multiple groups of wet-milled EMD mixed samples with different grinding times, first selects the wet-milled samples with suitable particle sizes, and then mixes them with other EMD mixed samples with different particle sizes in a certain proportion. The mixed samples no longer have a large attenuation in compaction density, and do not affect the OCV improvement brought by wet grinding.

[0011] Furthermore, the amount of water added is 20% to 100% of the amount of the first part of EMD; if the amount of distilled water is less than 20%, the cooling effect is not obvious; if it is greater than 100%, too much water will overflow the grinding jar and affect the grinding effect.

[0012] Furthermore, the grinding time is 300s to 1200s; if it is less than 300s, the grinding effect of EMD is poor, and the particle size is coarse and cannot be smoothly sieved; if it is more than 1200s, the grinding effect is too strong, and the EMD particles are too fine, affecting the compaction density.

[0013] Furthermore, the median diameter of the particles after wet grinding is 10 μm to 30 μm.

[0014] Furthermore, the average diameter of the particles after wet grinding is 15 to 50 μm, preferably the median diameter is 13 to 18 μm, and the average diameter is 20 to 30 μm.

[0015] Furthermore, the median diameter of the second portion EMD is 20 μm to 50 μm.

[0016] Furthermore, the average diameter of the second part EMD is 30-70 μm, preferably the median diameter is 25-30 μm, and the average diameter is 30-45 μm.

[0017] Furthermore, the ratio of the wet-milled EMD to the second portion of EMD is 1:1 to 1:10.

[0018] The second part of EMD is prepared by dry grinding. After dry grinding, the median diameter is 20 μm to 50 μm and the average diameter is 30 to 70 μm; preferably, the median diameter is 25 to 30 μm; and the average diameter is 30 to 45 μm.

[0019] According to the second aspect of the present invention, an EMD is provided, and the EMD is prepared by using the above-mentioned EMD wet grinding preparation process.

[0020] According to a third aspect of the present invention, there is provided a use of the EMD as described above in an alkaline manganese battery.

[0021] The present invention has the following advantages:

[0022] The present invention uses the specific heat capacity of water through wet grinding to absorb the heat generated during the grinding process, so that the grinding temperature is lower than that of dry grinding, the thermal attenuation of OCV is weakened, and an EMD product with a higher OCV is obtained.

[0023] The preparation process of the present invention can improve the uniformity of EMD particles: the first part of EMD can be wet-milled and screened to obtain particles with relatively uniform particle size. After being mixed with the second part of EMD, the overall particle distribution is more reasonable. In some application scenarios (such as battery materials), this uniform particle distribution helps to improve the consistency of product performance.

[0024] The preparation process of the present invention can optimize chemical properties: the neutralization step can adjust the chemical properties such as the pH of the first part of EMD to a more ideal state. After mixing with the second part of EMD, it can reduce adverse chemical reactions that may be caused by differences in chemical properties, thereby improving the chemical stability of the product.

[0025] The preparation process of the present invention has the characteristics of flexible product preparation: by changing the ratio of the first part of EMD and the second part of EMD, the characteristics of the final EMD mixed sample can be flexibly adjusted. DETAILED DESCRIPTION

[0026] 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.

[0027] Grinding frequency: 50-150 Hz; Screening rate: 60%-90%.

[0028] The relationship between wet grinding time and particle size is shown in Table 1.

[0029] Others: For the first part, take 150g of EMD, add 75ml of distilled water, change the grinding time, and see the relationship between wet grinding time and particle size.

[0030] Table 1

[0031] Wet grinding time / s Median diameter / μm Average diameter / μm 300 19.2 32.1 400 17.4 29.8 600 14.8 23.1 800 13.1 22.7 1200 11.8 20.9

[0032] Example 1

[0033] This embodiment provides an EMD wet grinding preparation process:

[0034] Take 150g of the first part of EMD, add 75ml of distilled water, and grind for 400s. After wet grinding, screen, neutralize and dry, select the first EMD after wet grinding with a median diameter of 10μm and an average diameter of 15μm, and mix it with the second part of EMD with a median diameter of 25μm and an average diameter of 38μm. The ratio of the two is 1:5, and the EMD mixed sample is obtained.

[0035] Example 2

[0036] This embodiment provides an EMD wet grinding preparation process:

[0037] Take 150g of the first part of EMD, add 75ml of distilled water, and grind for 1200s. After wet grinding, screen, neutralize and dry, select the first EMD after wet grinding with a median diameter of 25μm and an average diameter of 30μm, and mix it with the second part of EMD with a median diameter of 20μm and an average diameter of 30μm in a ratio of 1:5 to obtain an EMD mixed sample.

[0038] Example 3

[0039] This embodiment provides an EMD wet grinding preparation process:

[0040] Take 150g of the first part of EMD, add 75ml of distilled water, and grind for 600s. After wet grinding, screen, neutralize and dry, select the first EMD after wet grinding with a median diameter of 30μm and an average diameter of 50μm, and mix it with the second part of EMD with a median diameter of 50μm and an average diameter of 70μm in a ratio of 1:6 to obtain an EMD mixed sample.

[0041] Example 4

[0042] This embodiment provides an EMD wet grinding preparation process:

[0043] Take 150g of the first part of EMD, add 100ml of distilled water, and grind for 600s. After wet grinding, screen, neutralize and dry, select the first EMD after wet grinding with a median diameter of 25μm and an average diameter of 30μm, and mix it with the second part of EMD with a median diameter of 25μm and an average diameter of 38μm in a ratio of 1:3 to obtain an EMD mixed sample.

[0044] Example 5

[0045] This embodiment provides an EMD wet grinding preparation process:

[0046] Take 150g of the first part of EMD, add 75ml of distilled water, and grind for 800s. After wet grinding, screen, neutralize and dry, select the first EMD after wet grinding with a median diameter of 25μm and an average diameter of 30μm, and mix it with the second part of EMD with a median diameter of 25μm and an average diameter of 38μm in a ratio of 1:6 to obtain an EMD mixed sample.

[0047] Example 6

[0048] This embodiment provides an EMD wet grinding preparation process:

[0049] Take 150g of the first part of EMD, add 75ml of distilled water, and grind for 600s. After wet grinding, screen, neutralize and dry, select the first EMD after wet grinding with a median diameter of 25μm and an average diameter of 30μm, and mix it with the second part of EMD with a median diameter of 25μm and an average diameter of 38μm in a ratio of 1:10 to obtain an EMD mixed sample.

[0050] Example 7

[0051] This embodiment provides an EMD wet grinding preparation process:

[0052] Take 150g of the first part of EMD, add 75ml of distilled water, and grind for 600s. After wet grinding, screen, neutralize and dry, select the first EMD after wet grinding with a median diameter of 25μm and an average diameter of 30μm, and mix it with the second part of EMD with a median diameter of 25μm and an average diameter of 38μm in a ratio of 1:1 to obtain an EMD mixed sample.

[0053] Example 8

[0054] This comparative example provides an EMD wet grinding preparation process:

[0055] Take 150g of the first part of EMD, add 150ml of distilled water, and grind for 600s. After wet grinding, screen, neutralize and dry, select the first EMD after wet grinding with a median diameter of 25μm and an average diameter of 30μm, and mix it with the second part of EMD with a median diameter of 20μm and an average diameter of 30μm in a ratio of 1:5 to obtain an EMD mixed sample.

[0056] Example 9

[0057] This comparative example provides an EMD wet grinding preparation process:

[0058] Take 150g of the first part of EMD, add 30ml of distilled water, and grind for 600s. After wet grinding, screen, neutralize and dry, select the first EMD after wet grinding with a median diameter of 25μm and an average diameter of 30μm, and mix it with the second part of EMD with a median diameter of 20μm and an average diameter of 30μm in a ratio of 1:5 to obtain an EMD mixed sample.

[0059] Example 10

[0060] This comparative example provides an EMD wet grinding preparation process:

[0061] Take 150g of the first part of EMD, add 150ml of distilled water, and grind for 300s. After wet grinding, screen, neutralize and dry, select the first EMD after wet grinding with a median diameter of 25μm and an average diameter of 30μm, and mix it with the second part of EMD with a median diameter of 20μm and an average diameter of 30μm in a ratio of 1:5 to obtain an EMD mixed sample.

[0062] Embodiment 11

[0063] This comparative example provides an EMD wet grinding preparation process:

[0064] 150 g of the first part of EMD was first taken, and 75 ml of distilled water was added. The grinding time was 600 s. After wet grinding, it was sieved, neutralized, and dried. The first EMD after wet grinding with a median diameter of 25 μm and an average diameter of 30 μm was selected and mixed with the second part of EMD with a median diameter of 25 μm and an average diameter of 38 μm. The ratio was 1:4, and the EMD mixed sample was obtained.

[0065] Comparative Example 1

[0066] This comparative example provides an EMD dry grinding preparation process:

[0067] Take 150 g of EMD; grind for 950 seconds; do not add distilled water; do not mix with other samples.

[0068] Comparative Example 2

[0069] This comparative example provides an EMD wet grinding preparation process:

[0070] Take 150g of EMD, add 75ml of distilled water, grind for 950s, do not mix with other samples, the median diameter after grinding is 25μm and the average diameter is 30μm.

[0071] Comparative Example 3

[0072] This comparative example provides an EMD wet grinding preparation process:

[0073] Take 150g of the first part of EMD, add 75ml of distilled water, and grind for 800s. Select the first EMD after wet grinding with a median diameter of 25μm and an average diameter of 30μm, and mix it with the second part of EMD with a median diameter of 25μm and an average diameter of 38μm in a ratio of 1:4. After mixing, sieve, neutralize and dry, the EMD mixed sample is obtained.

[0074] The EMD mixed samples of Examples 1-11 and Comparative Examples 1-3 were subjected to OCV test and various tests after being granulated and pressed into button batteries. The data are shown in Table 2.

[0075] Table 2

[0076]

[0077] As shown in Table 1, the OCV, capacitance and liquid absorption of the EMD mixed sample after wet grinding are improved, but the compaction density is reduced due to the narrow PSD distribution. Therefore, the subsequent mixing with other particle size samples is to make the PSD distribution of the wet grinding sample reasonable so that the compaction density will no longer have a significant attenuation.

[0078] Comparative Example 1 is a normal dry-grinding sample, and other indicators except compaction density are low; Comparative Example 2 is a sample that is wet-grinded but not mixed. Although OCV and liquid absorption are improved, the capacitance is reduced because the compaction density drops sharply, so the concept of mixed samples is introduced. Compared with Comparative Example 2, the compaction density of the mixed sample is improved, so the capacitance is improved.

[0079] The OCV of the wet-milled EMD samples was significantly improved by about 10mV compared to the normal dry-milled EMD samples. In addition, the liquid absorption was also improved, and its electrical properties were also improved accordingly. The decrease in compaction density of the wet-milled samples and the mixed samples was smaller.

[0080] 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. An EMD wet grinding preparation process, characterized in that: The process comprises: firstly taking a first part of EMD, adding water to perform wet grinding, screening, neutralizing, and drying, and then mixing with a second part of EMD to obtain an EMD mixed sample.

2. The EMD wet grinding preparation process according to claim 1, characterized in that: The amount of water added is 20% to 100% of the amount of the first part of EMD.

3. The EMD wet grinding preparation process according to claim 1, characterized in that: The wet grinding time is 300s to 1200s.

4. The EMD wet grinding preparation process according to claim 1, characterized in that: The median diameter of the particles after wet grinding is 10 μm to 30 μm.

5. The EMD wet grinding preparation process according to claim 4, characterized in that: The average diameter of the particles after wet grinding is 15 to 50 μm.

6. The EMD wet grinding preparation process according to claim 1, characterized in that: The median diameter of the second portion EMD is 20 μm to 50 μm.

7. The EMD wet grinding preparation process according to claim 6, characterized in that: The average diameter of the second portion EMD is 30-70 μm.

8. The EMD wet grinding preparation process according to claim 1, characterized in that: The ratio of the wet-ground EMD to the second part of EMD is 1:1 to 1:

10.

9. An EMD, characterized in that: The EMD is prepared by the EMD wet grinding preparation process described in any one of claims 1-8.

10. Use of the EMD as claimed in claim 9 in an alkaline manganese battery.

Images