A method for preparing a negative electrode slurry for a sodium ion battery and the negative electrode slurry

Abstract

The present invention discloses a method for preparing a negative electrode slurry for a sodium ion battery and a negative electrode slurry. The method comprises the following steps: S1, preparing a CMC glue solution; S2, adding hard carbon and SP into a stirring pot at the same time, stirring to form a first slurry, wherein the SP is a conductive agent; S3, adding the CMC glue solution into the first slurry, stirring to form a second slurry, wherein the solid content of the second slurry is 73% to 76%; S4, adding the remaining CMC glue solution into the second slurry in batches, adding a solvent to adjust the solid content, and forming a third slurry; wherein the solid content of the third slurry is 48% to 52%; S5, adding SBR to the third slurry, stirring at a low speed under vacuum, and forming a fourth slurry; S6, sieving the fourth slurry to obtain a negative electrode slurry, wherein the solid content of the negative electrode slurry is 47% to 51%. The negative electrode slurry prepared by the preparation method of the present invention is well dispersed, so that the obtained negative electrode sheet has good adhesion and will not fall off.

Description

Technical Field

[0001] The present invention relates to the field of battery manufacturing, and in particular to a method for preparing a negative electrode slurry for a sodium ion battery, the negative electrode slurry prepared by the method, and a negative electrode sheet prepared from the negative electrode slurry. Background Art

[0002] As a green chemical power source, sodium secondary batteries (SIBs) have garnered widespread attention from researchers. However, SIBs are still in the preliminary research stage, and many technical challenges remain. One key area of ​​SIB research is the development of industrial-scale preparation processes for novel anodes for sodium-ion batteries. The consistency of SIBs is hampered by numerous factors, including raw materials, batching, coating, and cell preparation. Excluding the influence of raw materials, batching and coating during electrode manufacturing are key factors in battery consistency. Anode slurry shedding is common during mixing, coating, drying, rolling, and die-cutting. This shedding is largely influenced by the cohesiveness of the slurry mix, particularly the dispersion of the SBR. The order of addition and stirring rate during the process also affect the cohesiveness between the components. The key control factor in batching is achieving microscopically uniform dispersion within the slurry. The industrialized slurry mixing process for SIBs differs from that for lithium-ion batteries and cannot be copied. Instead, it is necessary to explore a suitable SIB anode preparation process. Summary of the Invention

[0003] In order to overcome the above shortcomings, the purpose of the present invention is to provide a method for preparing a negative electrode slurry for a sodium ion battery and a negative electrode slurry. The present invention studies the refined process steps, optimizes the batching process to improve the consistency of the slurry, and improves the distribution of various substances in the coating process.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is: a method for preparing a negative electrode slurry for a sodium ion battery, comprising the following steps:

[0005] S1, preparing CMC glue, wherein CMC is the abbreviation of sodium carboxymethyl cellulose;

[0006] S2. Add hard carbon and SP into a stirring pot at the same time and stir to form a first slurry, where SP is a conductive agent;

[0007] S3, adding CMC glue to the first slurry, stirring to form a second slurry, the solid content of the second slurry is 73% to 76%;

[0008] S4, adding the remaining CMC glue to the second slurry in batches, adding solvent to adjust the solid content, to form a third slurry; the solid content of the third slurry is 48-52%;

[0009] S5, adding SBR to the third slurry, stirring at a low speed under vacuum to form a fourth slurry;

[0010] S6. Screening the fourth slurry to obtain negative electrode slurry, wherein the solid content of the negative electrode slurry is 47-51%.

[0011] The present invention is further configured as follows: in S1, CMC powder and deionized water are added to a mixer, the stirring speed is 30-50 r / min, the dispersion speed is 800-1200 r / min, and stirring is carried out for 20-40 minutes, and then the stirring speed is 30-50 r / min, the dispersion speed is 2500-3500 r / min, and the stirring time is 200-300 minutes.

[0012] The present invention is further configured as follows: in S3, the solid content of the second slurry is 74%.

[0013] The present invention is further configured as follows: in S4, first stirring at a stirring speed of 30 to 50 r / min and a dispersion speed of 400 to 600 r / min for 10 to 20 minutes; then opening the pot and scraping the wall, and then stirring at a stirring speed of 30 to 50 r / min and a dispersion speed of 2500 to 3000 r / min for 240 to 360 minutes to form a third slurry.

[0014] The present invention is further configured as follows: in S4, the solid content of the third slurry is 50%.

[0015] The present invention is further configured as follows: in S4, the solvent is a mixed solvent of water, NMP and ethanol, wherein NMP is N-methylpyrrolidone.

[0016] The present invention is further configured as follows: in S5, after adding SBR to the third slurry, stirring is carried out for 20 to 40 minutes at a stirring speed of 30 to 50 r / min and a dispersion speed of 400 to 600 r / min. The SBR is a water-based styrene-butadiene latex with a solid content of 40%.

[0017] The present invention is further configured as follows: in S6, the solid content of the negative electrode slurry is 49%.

[0018] A negative electrode slurry is prepared according to the above-mentioned method for preparing the negative electrode slurry for a sodium ion battery.

[0019] A negative electrode sheet for a sodium ion battery is prepared using the negative electrode slurry described above.

[0020] The present invention has the following beneficial effects:

[0021] 1) The present invention adjusts the viscosity of the slurry before adding SBR, so that the slurry is fully and evenly dispersed. Good dispersion will make the coating consistency of the prepared negative electrode sheet better and without obvious particle scratches.

[0022] 2) The present invention adjusts the dispersion speed of SBR and adopts low-speed stirring instead of high-speed stirring. This is to ensure the uniformity of SBR dispersion in the slurry, improve the adhesion of the negative electrode sheet, prevent the electrode sheet from falling off, and ensure the quality of the negative electrode sheet.

[0023] 3) Add CMC glue in batches and control the solid content of the slurry to ensure uniform dispersion of the negative electrode slurry.

[0024] 4) Adding a small amount of NMP can make the coating solvent evaporate more evenly; at the same time, adding a small amount of alcohol can have a defoaming effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a comparison chart of the resistivity of the negative electrode sheet in Example 7 of the present invention;

[0026] Figure 2 This is a schematic diagram of a disassembled battery after the first charge and discharge and full charging in Example 3 of the present invention;

[0027] Figure 3 This is a schematic diagram of the disassembled battery after the first charge and discharge and full charging in Example 4 of the present invention. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0029] In the following examples, the solids content of the second, third, and negative electrode slurries was measured as follows: After preparing the slurries, 5-20 g of the slurry was placed on aluminum foil and spread using a 100 μm-thick applicator. The wet film was then dried in a 100°C oven for 15-30 minutes until dry. The solids content was calculated as (wet film weight - dry film weight) / (wet film weight - base aluminum foil weight) * 100%.

[0030] Example 1

[0031] A method for preparing a negative electrode slurry for a sodium ion battery comprises the following steps:

[0032] S1, prepare CMC glue;

[0033] Add 37.5g of CMC powder (sodium carboxymethyl cellulose) and 1837.5g of deionized water into a blender. Stir slowly at first, with a stirring speed of 30r / min and a dispersion speed of 800r / min. Stir for 20min to pre-disperse the CMC powder. Then switch to high-speed stirring, with a stirring speed of 30r / min, a dispersion speed of 2500r / min, and a stirring time of 200min. Then let it stand for 30min to form a CMC glue.

[0034] S2. Add 2362.5 g of hard carbon and 30 g of SP into a stirring pot at the same time and stir for 15 min to form a first slurry at a stirring speed of 40 r / min and a dispersion speed of 800 r / min;

[0035] S3, adding 875.6g of CMC glue to the first slurry, stirring for 60min at a stirring speed of 30r / min to form a second slurry, the solid content of the second slurry being 73.7%;

[0036] S4, adding the remaining 999.4g of CMC glue, 518g of water, 81g of NMP, and 65g of ethanol to the second slurry in batches, stirring for 15min at a stirring speed of 30r / min and a dispersion speed of 400r / min; after scraping the wall, start vacuum high-speed stirring at a stirring speed of 30r / min and a dispersion speed of 2500r / min, and stir for 240min to form a third slurry. The solid content of the third slurry is 49.3%;

[0037] S5. Add 175 g of SBR to the third slurry, stir at a low speed under vacuum for 30 min, at a stirring speed of 30 r / min and a dispersion speed of 400 r / min to form a fourth slurry;

[0038] S6. Screening the fourth slurry to obtain negative electrode slurry, wherein the solid content of the negative electrode slurry is 49%.

[0039] Example 2

[0040] A method for preparing a negative electrode slurry for a sodium ion battery, characterized by comprising the following steps:

[0041] S1, prepare CMC glue;

[0042] Add 37.5g of CMC powder (sodium carboxymethyl cellulose) and 1837.5g of deionized water into a blender, stir slowly at first, with a stirring speed of 50r / min and a dispersion speed of 800r / min, and stir for 40min to pre-disperse the CMC powder; then switch to high-speed stirring, with a stirring speed of 50r / min, a dispersion speed of 3000r / min, and a stirring time of 300min, and then let it stand for 30min to form a CMC glue;

[0043] S2. Add 2362.5 g of hard carbon and 30 g of SP (conductive agent) into a stirring pot at the same time and stir for 15 min to form a first slurry at a stirring speed of 40 r / min and a dispersion speed of 800 r / min.

[0044] S3, adding 847.5g of CMC glue to the first slurry, stirring for 60min at a stirring speed of 50r / min to form a second slurry, the solid content of the second slurry being 74.4%;

[0045] S4, adding the remaining 999.4g of CMC glue, 320g of water, 50g of NMP, and 40g of ethanol to the second slurry in batches, stirring for 20min at a stirring speed of 50r / min and a dispersion speed of 600r / min; after scraping the wall, start vacuum high-speed stirring at a stirring speed of 50r / min and a dispersion speed of 3000r / min, and stir for 360min to form a third slurry. The solid content of the third slurry is 52%;

[0046] S5. Add 175 g of SBR (40% concentration) to the third slurry, and stir at a low speed under vacuum for 50 min at a stirring speed of 50 r / min and a dispersion speed of 600 r / min to form a fourth slurry;

[0047] S6. Sieve the fourth slurry to obtain negative electrode slurry, wherein the solid content of the negative electrode slurry is 51.5%.

[0048] Example 3

[0049] A method for preparing a negative electrode slurry for a sodium ion battery, characterized by comprising the following steps:

[0050] S1, prepare CMC glue;

[0051] Add 37.5g of CMC powder and 1837.5g of deionized water into a blender. Stir slowly at first, with a stirring speed of 40r / min and a dispersion speed of 1000r / min, and stir for 30min to pre-disperse the CMC powder; then switch to high-speed stirring, with a stirring speed of 40r / min, a dispersion speed of 2700r / min, and a stirring time of 240min. Then let it stand for 30min to form a CMC glue solution.

[0052] S2. Add 2362.5 g of hard carbon and 30 g of SP (conductive agent) into a stirring pot at the same time and stir for 15 min to form a first slurry at a stirring speed of 40 r / min and a dispersion speed of 800 r / min.

[0053] S3, adding 862.5g of CMC glue to the first slurry, stirring for 60min at a stirring speed of 30r / min to form a second slurry, the solid content of the second slurry being 74%;

[0054] S4, the remaining 1012.5g of CMC glue, 400g of water, 62.5g of NMP, and 50g of ethanol were added to the second slurry in batches, and stirred for 15min at a stirring speed of 40r / min and a dispersion speed of 500r / min; after scraping the wall, vacuum high-speed stirring was turned on, the stirring speed was 40r / min, the dispersion speed was 2700r / min, and stirring was carried out for 240min to form a third slurry. The solid content of the third slurry was 50.8%;

[0055] S5. Add 175 g of SBR (binder) to the third slurry, and stir at a low speed under vacuum for 30 min at a stirring speed of 40 r / min and a dispersion speed of 500 r / min to form a fourth slurry;

[0056] S6. Sieve the fourth slurry to obtain negative electrode slurry, wherein the solid content of the negative electrode slurry is 50.5%.

[0057] Example 4

[0058] A method for preparing a negative electrode slurry for a sodium ion battery, characterized by comprising the following steps:

[0059] S1, prepare CMC glue;

[0060] Add 37.5g of CMC powder (sodium carboxymethyl cellulose) and 1837.5g of deionized water into a blender. Stir slowly at first, with a stirring speed of 40r / min and a dispersion speed of 1000r / min. Stir for 30min to pre-disperse the CMC powder. Then switch to high-speed stirring, with a stirring speed of 40r / min, a dispersion speed of 2700r / min, and a stirring time of 240min. Then let it stand for 30min to form a CMC glue.

[0061] S2. Add 2362.5 g of hard carbon and 30 g of SP (conductive agent) into a stirring pot at the same time and stir for 15 min to form a first slurry at a stirring speed of 40 r / min and a dispersion speed of 800 r / min.

[0062] S3, adding a portion of CMC glue to the first slurry, stirring for 60 minutes at a stirring speed of 30 r / min to form a second slurry;

[0063] S4. Add the remaining CMC glue, 400g water, 62.5g NMP, and 50g ethanol to the second slurry, stir for 15min at a stirring speed of 40r / min and a dispersion speed of 500r / min; after scraping the wall, open the vacuum high-speed stirring, stir at a speed of 40r / min and a dispersion speed of 2700r / min, and stir for 240min to form a third slurry;

[0064] S5. Add 175 g of SBR (binder) to the third slurry, and stir at a low speed under vacuum for 30 min at a stirring speed of 40 r / min and a dispersion speed of 500 r / min to form a fourth slurry;

[0065] S6. Sieve the fourth slurry to obtain negative electrode slurry, wherein the solid content of the negative electrode slurry is 50.5%.

[0066] Example 5

[0067] S1, prepare CMC glue;

[0068] Add 37.5g of CMC powder (sodium carboxymethyl cellulose) and 1837.5g of deionized water into a blender. Stir slowly at first, with a stirring speed of 40r / min and a dispersion speed of 1000r / min. Stir for 30min to pre-disperse the CMC powder. Then switch to high-speed stirring, with a stirring speed of 40r / min, a dispersion speed of 2700r / min, and a stirring time of 240min. Then let it stand for 30min to form a CMC glue.

[0069] S2. Add 2362.5 g of hard carbon and 30 g of SP (conductive agent) into a stirring pot at the same time and stir for 15 min to form a first slurry at a stirring speed of 40 r / min and a dispersion speed of 800 r / min.

[0070] S3, adding 862.5g of CMC glue to the first slurry, stirring for 60min at a stirring speed of 30r / min to form a second slurry, the solid content of the second slurry being 75%;

[0071] S4, the remaining 1012.5g of CMC glue, 400g of water, 62.5g of NMP, and 50g of ethanol were added to the second slurry in batches, and stirred for 15min at a stirring speed of 40r / min and a dispersion speed of 500r / min; after scraping the wall, vacuum high-speed stirring was turned on, the stirring speed was 40r / min, the dispersion speed was 2700r / min, and stirring was carried out for 240min to form a third slurry. The solid content of the third slurry was 50.8%;

[0072] S5. Add 175 g of SBR to the third slurry and stir at high speed for 30 min at a dispersion speed of 2700 r / min to form a fourth slurry;

[0073] S6. Sieve the fourth slurry to obtain negative electrode slurry, wherein the solid content of the negative electrode slurry is 50.5%.

[0074] Example 6

[0075] A method for preparing a negative electrode slurry for a sodium ion battery, characterized by comprising the following steps:

[0076] S1, prepare CMC glue;

[0077] Add 37.5g of CMC powder (sodium carboxymethyl cellulose) and 1837.5g of deionized water into a blender. Stir slowly at first, with a stirring speed of 40r / min and a dispersion speed of 1000r / min. Stir for 30min to pre-disperse the CMC powder. Then switch to high-speed stirring, with a stirring speed of 40r / min, a dispersion speed of 2700r / min, and a stirring time of 240min. Then let it stand for 30min to form a CMC glue.

[0078] S2. Add 2362.5 g of hard carbon and 30 g of SP (conductive agent) into a stirring pot at the same time and stir for 15 min to form a first slurry at a stirring speed of 40 r / min and a dispersion speed of 800 r / min.

[0079] S3, adding a portion of CMC glue to the first slurry, stirring for 60 minutes at a stirring speed of 30 r / min to form a second slurry;

[0080] S4. Add the remaining CMC glue, 400g water, 62.5g NMP, and 50g ethanol to the second slurry, stir for 15min at a stirring speed of 40r / min and a dispersion speed of 500r / min; after scraping the wall, open the vacuum high-speed stirring, stir at a speed of 40r / min and a dispersion speed of 2700r / min, and stir for 240min to form a third slurry;

[0081] S5. Add 175 g of SBR (binder) to the third slurry and stir at high speed for 30 min at a dispersion speed of 2700 r / min to form a fourth slurry;

[0082] S6. Sieve the fourth slurry to obtain negative electrode slurry, wherein the solid content of the negative electrode slurry is 50.5%.

[0083] Example 7

[0084] The negative electrode slurries prepared in Examples 3, 4, 5, and 6 were passed through a coating machine die head and extrusion-dispensed or transfer-coated onto aluminum foil to form a uniform wet film that met the surface density standard. The film was then passed through a coating machine oven at a speed of 2 to 10 m / min to dry into negative electrode sheets with a weight loss of less than 0.3%. Weight loss = (weight of the electrode sheet after coating - weight after drying) / weight of the electrode sheet after coating * 100%.

[0085] The four groups of negative electrode sheets were coated and then subjected to weight loss tests. The test data are shown in Table 1:

[0086] Table 1

[0087] Example weightlessness(%) Example 3 0.137 Example 4 0.245 Example 5 0.253 Example 6 0.282

[0088] Example 3 The negative electrode sheet prepared according to the method for preparing the negative electrode slurry for sodium ion batteries provided by the present invention has a minimum weight loss of 0.137%.

[0089] The four groups of negative electrode sheets were rolled and then tested for surface resistance. Figure 1 We can see that the resistivity of the negative electrode sheet made from the negative electrode slurry prepared in Example 3 is the lowest.

[0090] Compare with Figure 2 and attached Figure 3 The negative electrode sheet prepared with the negative electrode slurry prepared in Example 3 has good adhesion and will not fall off after being fully charged and disassembled after the first charge and discharge.

[0091] The four groups of negative electrode sheets were rolled and then subjected to peel strength tests. The test data are shown in Table 2:

[0092] Table 2

[0093]

[0094]

[0095] Example 3 The negative electrode sheet prepared according to the method for preparing the negative electrode slurry for sodium ion batteries provided by the present invention has a peel strength of 76 N / m.

[0096] Compared with Example 3, Example 4 is different in that Example 4 does not limit the solid content of the slurry after adding CMC glue in batches, only adds CMC glue in batches, and does not determine the solid content of the slurry before adding SBR. The peel strength is 50N / m.

[0097] Compared with Example 3, Example 5 differs in that after SBR is added in Example 4, the slurry is stirred at a high speed, the dispersion speed is 2700 r / min, and the peel strength is 48 N / m.

[0098] Compared with Example 3, Example 6 is different in that Example 6 does not limit the solid content of the slurry after adding CMC glue in batches, only adds CMC glue in batches, and does not determine the solid content of the slurry before adding SBR; and after adding SBR, the slurry is stirred at a high speed, with a dispersion speed of 2700 r / min, and its peel strength is 44 N / m.

[0099] The data in Table 2 indicate that the negative electrode sheets produced according to the sodium-ion battery negative electrode slurry preparation method provided by the present invention exhibit the highest peel strength, thus resolving the issue of chipping during strip die-cutting. The present invention achieves this by adjusting the slurry viscosity before adding SBR, ensuring uniform SBR dispersion. This uniform dispersion results in excellent adhesion and prevents chipping of the resulting negative electrode sheets. Furthermore, by adjusting the SBR dispersion rate, employing low-speed stirring rather than high-speed stirring, the uniformity of SBR dispersion in the slurry is ensured, preventing SBR demulsification and thus guaranteeing the quality of the negative electrode sheets. The present invention also adds CMC glue in batches, controlling the slurry solids content, which is also a key factor in ensuring uniform dispersion of the negative electrode slurry. Furthermore, the addition of a small amount of NMP ensures more uniform solvent evaporation during the coating and baking process, preventing excessive evaporation from affecting the consistency of the electrode dressing and the tendency for the conductive agent and binder to float, thereby affecting the quality of the electrode sheets. A small amount of alcohol can be used to defoam, particularly when laboratory equipment lacks vacuum extraction capabilities.

[0100] The above embodiments are only for illustrating the technical concept and features of the present invention. Its purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. It cannot be used to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a negative electrode slurry for a sodium ion battery, characterized in that: The steps include: S1, prepare CMC glue; S2. Add hard carbon and SP into a stirring pot and stir to form a first slurry; S3, adding CMC glue to the first slurry, stirring to form a second slurry, the solid content of the second slurry is 73% to 76%; S4, adding the remaining CMC glue to the second slurry in batches, adding solvent to adjust the solid content to form a third slurry, the solid content of the third slurry is 48-52%; S5. Add SBR to the third slurry, stir at a low speed under vacuum at a stirring speed of 30 to 50 r / min and a dispersion speed of 400 to 600 r / min to form a fourth slurry; S6. Screening the fourth slurry to obtain negative electrode slurry, wherein the solid content of the negative electrode slurry is 47-51%.

2. The method for preparing a negative electrode slurry for a sodium ion battery according to claim 1, wherein: In S1, CMC powder and deionized water are added to the mixer, the stirring speed is 30-50 r / min, the dispersion speed is 800-1200 r / min, and the stirring time is 20-40 min; then the high-speed stirring is switched to 30-50 r / min, the dispersion speed is 2500-3500 r / min, and the stirring time is 200-300 min.

3. The method for preparing a negative electrode slurry for a sodium ion battery according to claim 1, wherein: In S3, the solid content of the second slurry is 74%.

4. The method for preparing a negative electrode slurry for a sodium ion battery according to claim 1, wherein: In S4, first, stir at a stirring speed of 30 to 50 r / min and a dispersion speed of 400 to 600 r / min for 10 to 20 min; Then open the pot and scrape the wall, and then stir at a stirring speed of 30-50 r / min and a dispersion speed of 2500-3000 r / min for 240-360 minutes to form a third slurry.

5. The method for preparing a negative electrode slurry for a sodium ion battery according to claim 1, wherein: In S4, the solid content of the third slurry is 50%.

6. The method for preparing a negative electrode slurry for a sodium ion battery according to claim 1, wherein: In S4, the solvent is a mixed solvent of water, NMP and ethanol.

7. The method for preparing a negative electrode slurry for a sodium ion battery according to claim 1, wherein: In S5, SBR is added to the third slurry and stirred for 20 to 40 minutes.

8. The method for preparing a negative electrode slurry for a sodium ion battery according to claim 1, wherein: In S6, the solid content of the negative electrode slurry is 49%.

9. A negative electrode slurry prepared according to the method for preparing a negative electrode slurry for a sodium ion battery according to any one of claims 1 to 8.

10. A negative electrode sheet for a sodium ion battery, prepared using the negative electrode slurry according to claim 9.

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