CN114464776B - Preparation method of ultrahigh-power ultrathin negative plate capable of being produced in batch - Google Patents

Abstract

The application discloses a preparation method of an ultra-high power ultra-thin negative plate capable of mass production in the technical field of chemical energy storage batteries, which comprises the following steps of preparing a negative active material, wherein the negative active material is one or more of hard carbon, soft carbon, graphite, mesophase carbon microspheres, lithium titanate, silicon carbon and silicon oxide, D90 of the negative active material is less than or equal to 5 mu m, and the specific surface area of the negative active material is greater than or equal to 5m ²/g. Mixing the raw materials of the negative plate together, kneading to form slurry, when the fineness of the slurry is less than or equal to a negative electrode active substance D90, finishing kneading, adding a binder and water into the kneaded slurry for dilution, regulating and controlling, sieving, putting into a coating machine, carrying out double-sided coating on a current collector, wherein the total thickness of the double-sided coating is less than or equal to 60 mu m, and carrying out high-temperature drying after coating to obtain the high-power ultrathin negative plate. The negative plate realizes 1500C limit discharge, and provides a new solving way for mass production of ultra-high power supply.

Description

A method for preparing ultra-high power ultra-thin negative electrode sheets capable of mass production

Technical Field

The present invention relates to the technical field of chemical energy storage batteries, and in particular to a method for preparing ultra-high power ultra-thin negative electrode sheets that can be mass-produced.

Background Art

With the development of science and technology, the military and civilian energy storage markets have higher and higher power requirements. In terms of pole piece preparation, there are currently the following main ways to improve battery rate performance: namely, to carry out high-performance ultra-thick pole piece preparation with supercapacitors as the direction, increase the active material load, and improve the specific power and specific energy of supercapacitors. Based on this, the current high-energy lithium-ion batteries, such as high-power lithium-ion batteries such as model aircraft and drones, are discharged at 30C, but the thickness of the negative pole piece is about 100μm, and the specific power of the battery is 3 to 5Kw/kg. However, its rate performance cannot meet the use requirements of ultra-high power weapons such as electronic cannons, laser weapons, and microwave weapons.

Summary of the invention

In view of the deficiencies of the prior art, the present invention designs a high-power ultra-thin negative electrode sheet.

One of the purposes of the present invention is to provide a method for preparing ultra-high power ultra-thin negative electrode sheets that can be mass-produced. The raw materials include negative electrode active materials, which are one or more of hard carbon, soft carbon, graphite, mesophase carbon microspheres, lithium titanate, silicon carbon, and silicon oxide. The negative electrode active materials have a D90 of ≤5μm and a specific surface area of greater than ≧ ^5m2 /g.

Furthermore, the raw materials also include a conductive agent, a thickener and a binder. The negative electrode active material, the conductive agent and the thickener are mixed together and kneaded into a slurry using a kneading process. When the slurry fineness is ≤ D90 of the negative electrode active material, the kneading is completed, the binder is added and mixed evenly, deionized water is added to dilute and regulate, the slurry is sieved, and the slurry is loaded into a coating machine to coat both sides of the current collector respectively. The total thickness of the double-sided coating is ≤60μm. After coating, it is dried at high temperature to obtain a high-power ultra-thin negative electrode sheet.

Furthermore, μ/σ of the slurry is less than 1 s/m, where μ is the slurry viscosity and σ is the surface tension of the slurry fluid.

Furthermore, the coater is a transfer coater or an extrusion coater.

Furthermore, high temperature drying is carried out in a vacuum drying oven, the drying temperature is 100°C to 200°C, the drying time is 2 to 100 hours, and the vacuum degree is ≥85Mpa.

Furthermore, the conductive agent is superconducting carbon black SP, the thickener is CMC, and the binder is SBR.

Furthermore, the current collector is copper foil.

The second object of the present invention is to provide a high-power ultra-thin negative electrode sheet prepared using the above method.

A third object of the present invention is to provide an application of a high-power ultra-thin negative electrode sheet in an ultra-high power power supply.

Working principle of the present invention: The raw materials of the present invention are selected from materials with small particle size, which greatly shortens the internal ion and electron transmission paths of the materials. At the same time, through the preparation of high-porous ultra-thin electrode sheets, the transmission channel of Li+ in the electrode sheets is widened and the Li+ transmission distance is shortened, and the transmission distance of electrons in the electrode sheets is also shortened. In combination with the kneading principle, mechanical stirring is used to make particles interact with each other, so as to solve the problem that high specific surface area and small particle size negative electrode materials are easy to agglomerate during the pulping process. Then, by regulating the slurry, a negative electrode slurry for ultra-thin coating that can be used for transfer coater or extrusion coater is prepared, and an ultra-high power negative electrode sheet with a thickness deviation of less than 1μm and no obvious coating defects is prepared, so that the negative electrode sheet achieves 1500C limit discharge, providing a new solution for mass production of ultra-high power power supplies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a diagram of the fineness of a successfully kneaded slurry in Example 1 of the present invention;

FIG2 is a test diagram of the double-sided thickness (excluding the current collector thickness) of the high-power ultra-thin pole piece of Example 1 of the present invention;

FIG3 is a 1500C second charge-discharge curve diagram of the electrode sheets prepared in Examples 1-2 and Comparative Examples 3-5 of the present invention.

DETAILED DESCRIPTION

The specific embodiments of the present invention are further described in detail, but the present invention is not limited to these embodiments. Any improvement or substitution based on the basic spirit of the present embodiment still falls within the scope of protection required by the claims of the present invention.

The high-power ultra-thin electrode sheets of implementation cases 1 to 2 and the negative electrode sheets of comparison cases 1 to 3 were prepared as follows:

Example 1

Weigh a graphite material with a D90 of 5 μm and a specific surface area of 6 m ² /g, and add it to a CMC aqueous solution (the mass ratio of CMC to water is 1:40) together with a conductive agent SP for kneading. Among the raw materials of the negative electrode sheet, the mass ratio of the graphite material, the conductive agent SP, the binder SBR, and the thickener CMC is 95:1:2:2. Take a sample for fineness test every 1 hour of stirring, as shown in Figure 1, until the slurry fineness is 5 μm, ensure that the slurry has no agglomeration, kneading is completed, add a certain amount of SBR and continue stirring, add water to dilute to μ/σ of 0.3s/m, sieve, and use a transfer coater to coat both sides of the current collector respectively. The total thickness of the double-sided coating is 30 μm, as shown in Figure 2. The final high-power ultra-thin electrode sheet has a double-sided thickness (excluding the current collector thickness) of 30 μm. The coated electrode sheet is dried for 12 hours in an environment of 85 MPa vacuum and 120°C to obtain a high-power ultra-thin negative electrode sheet.

Example 2

Weigh a hard carbon material with a D90 of 4 μm and a specific surface area of 8 m ² /g, and add it to a CMC aqueous solution (the mass ratio of CMC to water is 1:40) together with a conductive agent SP for kneading. The raw materials of the negative electrode sheet have a mass ratio of 95:1:2:2 for the hard carbon material, conductive agent SP, binder SBR, and thickener CMC. Take a sample for fineness test every 1 hour of stirring until the slurry fineness is 4 μm to ensure that the slurry has no agglomeration. After kneading, add a certain amount of SBR and continue stirring. Add water to dilute to μ/σ of 0.3 s/m, sieve, and use a transfer coater to coat both sides of the current collector. The total thickness of the double-sided coating is 30 μm. The coated electrode sheet is dried in a vacuum environment of 85 MPa and 120°C for 12 hours to obtain a high-power ultra-thin negative electrode sheet.

Comparative Example 1

Weigh a graphite material with a D90 of 21 μm and a specific surface area of 1 m ² /g, and add it to a CMC aqueous solution (the mass ratio of CMC to water is 1:40) together with a conductive agent SP for kneading. The mass ratio of graphite material, conductive agent SP, binder SBR, and thickener CMC in the raw materials of the negative electrode sheet is 95:1:2:2. Take a sample for fineness test every 1 hour of stirring until the slurry fineness is less than 21 μm, add a certain amount of SBR and stir, add water to dilute μ/σ to 0.3 s/m, sieve, and use a transfer coater to coat the current collector. The coated electrode sheet is dried for 12 hours in an environment with a vacuum degree of 85 MPa and 120°C to obtain a negative electrode sheet.

Comparative Example 2

Weigh a graphite material with a D90 of 5 μm and a specific surface area of 6 m ² /g, and add it to a CMC aqueous solution (the mass ratio of CMC to water is 1:40) together with a conductive agent SP. The mass ratio of the graphite material, conductive agent SP, binder SBR, and thickener CMC in the raw materials of the negative electrode sheet is 95:1:2:2. Stir and mix. At this time, the slurry fineness is 18 μm. Add a certain amount of SBR and stir. Add water to dilute to μ/σ of 0.3 s/m, sieve, and use a transfer coater to coat the current collector. The coated electrode sheet is dried in an environment of 85 MPa vacuum and 120°C for 12 hours to obtain a negative electrode sheet.

Comparative Example 3

Weigh a graphite material with a D90 of 10 μm and a specific surface area of 1 m ² /g, and add it to a CMC aqueous solution (the mass ratio of CMC to water is 1:40) together with a conductive agent SP for kneading. The mass ratio of graphite material, conductive agent SP, binder SBR, and thickener CMC in the raw materials of the negative electrode sheet is 95:1:2:2. Take a sample for fineness test every 1 hour of stirring until the slurry fineness is less than 10 μm, add a certain amount of SBR and stir, add water to dilute to μ/σ of 0.3 s/m, sieve, and use a transfer coater to coat both sides of the current collector. The total thickness of the double-sided coating is 30 μm. The coated electrode sheet is dried in an environment of 85 MPa vacuum and 120°C for 12 hours to obtain a negative electrode sheet.

Comparative Example 4

Weigh the graphite material with a certain D90 of 5μm and a specific surface area of ^6m2 /g, and SP, add them into CMC aqueous solution (the mass ratio of CMC to water is 1:40) for kneading, and the material layer of the negative electrode sheet, conductive agent SP, binder SBR, thickener CMC, according to the mass ratio of 95:1:2:2. Take samples for fineness test every 1h of stirring until the slurry fineness is 5μm, add a certain amount of SBR and stir, add water to dilute to 0.3s/m, sieve, and use a transfer coater to coat both sides of the current collector respectively. The total thickness of the double-sided coating is 30μm. The coated electrode sheet is dried for 12h in an environment of vacuum degree 85Mpa and 85℃ to obtain a negative electrode sheet.

Comparative Example 5

Weigh the graphite material with a certain D90 of 5μm and a specific surface area of ^6m2 /g, and SP, add them into CMC aqueous solution (the mass ratio of CMC to water is 1:40) for kneading, and the material layer of the negative electrode sheet, conductive agent SP, binder SBR, thickener CMC, according to the mass ratio of 95:1:2:2. Take samples for fineness test every 1h of stirring until the slurry fineness is 5μm, add a certain amount of SBR and stir, add water to dilute to 0.3s/m, and use a transfer coater for coating. The total thickness of the double-sided coating slurry is 80μm, dry at 120℃ for 12h, and the vacuum degree is 85Mpa.

The current collectors of Examples 1 to 2 and Comparative Examples 1 to 5 are made of 9 μm copper foil, and current collectors of other thicknesses or materials are also applicable.

Table 1 Relevant parameters of the negative electrode sheets provided in Examples 1-2 and Comparative Examples 1-5.

As can be seen from Table 1, in Example 1 and Comparative Examples 1 and 2, it can be seen that the material particles are too large or the slurry is agglomerated, resulting in excessive slurry fineness, making it impossible to prepare uniform ultra-thin electrode sheets.

Application Examples

The negative electrode sheets of the lithium ion capacitors of implementation cases 1-2 and comparative cases 3-4 were prepared as follows, double-sided coating was performed, and stacked cells of about 1Ah were assembled according to the company's production process.

As can be seen from Figure 3, implementations 1 to 2 can perform 1500C discharge, indicating that the weight of the active material has little effect on pulse charge and discharge. Comparative Example 3 cannot perform 1500C discharge, indicating that the particle size and specific surface area of the material are the limiting factors of the limit discharge. Comparative Example 4 can perform 1500C second charge and discharge, but the voltage drop is large, indicating that the drying temperature has an impact on the limit discharge of the electrode. It is possible that high temperature can achieve high-temperature pore formation and increase and widen the Li ⁺ transmission channel. Comparative Example 5 cannot perform 1500C second charge and discharge, indicating that the electrode thickness is the limiting factor of the extremely high rate discharge.

The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims (5)

1. A method for preparing an ultra-high power ultra-thin negative electrode sheet capable of mass production, characterized in that the raw materials include a negative electrode active material, the negative electrode active material is one or more of hard carbon, soft carbon, graphite, mesophase carbon microspheres, lithium titanate, silicon carbon, and silicon oxide, the negative electrode active material D90≤5μm, and the specific surface area is greater than≧ ^5m2 /g; the raw materials also include a conductive agent, a thickener, and a binder, the negative electrode active material, the conductive agent, and the thickener are mixed together, and a kneading process is adopted to knead the negative electrode active material, when the slurry fineness is ≤D90 of the negative electrode active material, the kneading is terminated, the binder is added and mixed evenly, deionized water is added to dilute and control, the slurry is sieved, the μ/σ of the slurry is <1s/m, the slurry is loaded into a coating machine, and the double sides of the current collector are coated respectively, the total thickness of the double-sided coating is ≤60μm, and high-temperature drying is performed after coating, the drying temperature is 120°C, and the drying time is 12h to obtain a high-power ultra-thin negative electrode sheet. 2. The method for preparing an ultra-high power ultra-thin negative electrode sheet capable of mass production according to claim 1, characterized in that the coating machine is a transfer coater or an extrusion coater. 3. The method for preparing an ultra-high power ultra-thin negative electrode sheet capable of mass production according to claim 2, characterized in that: high-temperature drying is carried out in a vacuum drying oven with a vacuum degree ≥ 85Mpa. 4. An ultra-high power ultra-thin negative electrode sheet prepared by the method according to any one of claims 1 to 3. 5. Application of an ultra-high power ultra-thin negative electrode sheet prepared by the method according to any one of claims 1 to 3 in an ultra-high power power supply.