CN103367703A - A negative pole piece of a lithium-ion battery and a battery comprising the pole piece - Google Patents

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a negative pole piece of a lithium ion battery. The arrangement of the crack structure can greatly improve the absorption speed of the pole piece to the electrolyte, and reduce the standing time of the lithium ion battery after liquid injection. In the lithium ion battery adopting the crack structure, the existence of the crack provides a highway for the rapid transmission of the electrolyte in the pole piece, and the charge-discharge rate performance of the battery is greatly improved. In addition, the invention also discloses a lithium ion battery.

Description

A negative pole piece of a lithium-ion battery and a battery comprising the pole piece

technical field

The invention belongs to the technical field of lithium ion batteries, and in particular relates to a negative pole piece of a lithium ion battery and a battery including the pole piece.

Background technique

Since the large-scale commercialization of lithium-ion batteries, they have been widely used in portable electrical appliances such as laptops, cameras, and mobile communications due to their advantages of high energy density and high power density. Although the market demand is increasing, the competition faced by lithium-ion battery manufacturers is also becoming more and more fierce. On the one hand, the fierce competition is reflected in the comparison of the performance of lithium-ion batteries, and on the other hand, it is reflected in the level of battery manufacturing costs.

In order to improve the competitiveness of products, lithium-ion battery manufacturers have been working on improving battery performance and reducing battery manufacturing costs. Among the many technical efforts, most of the technologies can only meet the requirements of one aspect, either can only improve the performance of the battery, or can only reduce the cost of the battery. Therefore, those technical efforts and innovations that can simultaneously improve battery performance and reduce battery manufacturing costs are undoubtedly very attractive to lithium-ion battery manufacturers.

Contents of the invention

One of the purposes of the present invention is to: aim at the deficiencies of the prior art, and provide a kind of negative pole piece of lithium-ion battery, the negative pole piece of the present invention has very fast absorption speed to electrolyte; The final static time, thereby reducing the manufacturing time cost of the battery, and the performance of the battery charge and discharge rate will be significantly improved.

In order to achieve the above object, the present invention provides a negative pole piece of a lithium ion battery, the technical solution is as follows: a negative pole piece of a lithium ion battery, the negative pole piece is provided with a crack structure, and the opening of the crack structure is arranged at pole piece surface. The crack structure can be prepared during the coating and drying process of the pole piece, or through the process of bending the pole piece after drying. The crack can be straight or curved; the crack direction can be along the width of the pole piece direction or along the length direction of the pole piece, or along the two directions of the width direction and the length direction of the pole piece. Cracks can run through the entire thickness of the pole piece from the surface of the pole piece, or only through part of the thickness of the pole piece; compared with the latter, the improvement of the electrolyte absorption speed and battery rate performance of the former is more significant.

For the currently commonly used commercial lithium-ion batteries, under normal circumstances, there will be no crack structure in the battery pole piece. In the cold pressing process of the battery pole piece without crack structure, many holes on the surface of the pole piece will be blocked, because there is a rolling process in the cold pressing process of the pole piece. Test the electrolyte absorption rate of the cold-pressed pole piece, and it is easy to find that the absorption rate of the electrode solution is very slow, because many pores on the surface have been blocked. The existence of the cracks in the pole piece of the new structure disclosed by the present invention provides a high-speed channel for the electrolyte to penetrate into the pole piece, and these cracks are difficult to be completely blocked during the cold pressing process, so the absorption speed of the electrolyte can be greatly improved, Decreased the rest time after the cell is filled with liquid.

The active material in the negative electrode sheet is at least one of graphite, silicon, silicon-carbon alloy and tin alloy.

The width of the crack in the crack structure is 1-20um, and the width of the crack should be at least more than 1um, otherwise it will be difficult to improve the electrolyte absorption speed due to capillary action; but the crack width should not be too large, Otherwise, it will have a great impact on the impedance of the battery, the structural stability of the pole piece, and the energy density of the battery.

Preferably, the width of the cracks in the crack structure is 1-5um.

The length of the cracks in the crack structure is at least 5um, and the length of the cracks should not be too small, otherwise it is easy to be blocked during the cold pressing process.

The surface density of the cracks in the crack structure is 10~10000m/m2 ^, the surface density of the cracks in the crack structure is 10~10000m/ ^m2 , the surface density of the cracks should not be too small, otherwise the liquid absorption of the pole piece The improvement effect of the performance and the rate performance of the battery is not obvious; the surface density should not be too large, otherwise it will have a great impact on the impedance of the battery, the structural stability of the pole piece, and the energy density of the battery.

Preferably, the surface density of the cracks in the crack structure is 100-1000m/m ² .

The cross-sectional shape of the cracks in the crack structure is at least one of triangle, trapezoid and rectangle.

Another object of the present invention is to provide a lithium-ion battery, comprising a positive pole piece, a negative pole piece, a diaphragm and an electrolyte disposed between the positive pole piece and the negative pole piece, and the lithium-ion battery adopts the above-mentioned The negative pole piece with a crack structure is used as a lithium ion battery pole piece.

For a battery assembled from the pole pieces of the new structure disclosed by the present invention, the presence of cracks can improve the charge-discharge rate performance of the battery. In the same way, for a battery pole piece without cracks, since some pores on the surface of the pole piece are blocked during the cold pressing process, lithium ions will be greatly constrained to migrate back and forth through the surface pores of the pole piece during the charge and discharge process; in addition, The migration of lithium ions in the thickness direction of the pole piece is also limited by the tortuous transmission path, because the high compaction density determines that there is no direct electrolyte channel inside the pole piece for lithium ions to migrate directly from the surface layer of the pole piece to the bottom layer. The existence of cracks in the pole piece of the new structure disclosed by the present invention not only solves the bottleneck restriction of the fast migration of lithium ions back and forth through the holes on the surface of the pole piece, but also solves the restriction of the tortuous transmission path of the rapid migration of lithium ions inside the pole piece Therefore, the rate performance of the battery can be significantly improved.

Description of drawings

Fig. 1 is a schematic structural diagram of Embodiment 1 of the present invention.

Fig. 2 is a schematic structural diagram of Embodiment 2 of the present invention.

Fig. 3 is a schematic structural diagram of Embodiment 3 of the present invention.

Fig. 4 is a schematic structural diagram of Embodiment 4 of the present invention.

Fig. 5 is a schematic structural diagram of Embodiment 5 of the present invention.

Detailed ways

The present invention and its beneficial effects will be described in detail below with reference to the drawings and embodiments, but the embodiments of the present invention are not limited thereto.

Embodiment 1, as shown in Figure 1, a kind of negative pole pole piece of lithium ion battery, negative pole pole piece 1 is provided with crack structure, and crack structure opening is arranged on pole piece surface layer, and the surface density of the crack 3 of its crack structure is 100m/ mm ² , the width of the crack 3 is 5um, the length of the crack 3 is 5um, the cross-sectional shape of the crack 3 is triangular, and the thickness of the pole piece is completely penetrated by the crack 3 . The used negative pole piece 1 is to adopt graphite as the active material, and the distribution ratio of each component in the negative pole piece 1 is, graphite: superconducting carbon: sodium carboxymethyl cellulose: styrene-butadiene rubber=96%:1.0%:1.0%: 2.0%. The negative electrode sheet 1 is cold-pressed (compaction density 1.70g/cc), and assembled with the positive electrode sheet, separator, electrolyte and packaging bag to form a finished battery cell. In order to characterize the absorption speed of the new structure negative pole piece 1 to the electrolyte, we drop 0.1g of electrolyte on the cold-pressed negative pole piece 1, and then measure the time required for the pole piece to completely absorb 0.1g of electrolyte, and Recorded in Table 1 for comparison. In addition, we will also conduct 3C discharge and 3C charge rate tests on the batteries, and the test results are recorded in Table 1 for comparison.

Example 2, as shown in Figure 2, differs from Example 1 in that the surface density of the crack 3 in this example is 1000m/mm ² , the width of the crack 3 is 12um, the length of the crack 3 is 8um, and the crack 3 is The cross-sectional shape is trapezoidal, and the thickness of the pole piece is completely penetrated by cracks 3 . The negative electrode sheet 1 used uses silicon as the active material, and is prepared by stirring according to the negative electrode formula (silicon: superconducting carbon: sodium carboxymethyl cellulose: styrene-butadiene rubber = 96%: 1.0%: 1.0%: 2.0%) to obtain the negative electrode slurry, and then the negative electrode slurry is coated on the copper foil current collector to prepare the negative electrode sheet, and then the negative electrode sheet is cold-pressed (the compaction density is 1.70g/cc), and the positive electrode sheet, separator, electrolyte and The packaging bag is assembled into a finished cell.

Others are the same as in Embodiment 1 and will not be repeated here.

Embodiment 3, as shown in FIG. 3 , differs from Embodiment 2 in that the surface density of the crack 3 in this embodiment is 10m/mm ² , the width of the crack 3 is 1um, the length of the crack 3 is 9um, and the crack 3 is The cross-sectional shape is rectangular, and the thickness of the pole piece is not completely penetrated with cracks. The negative pole piece 1 used is to adopt silicon-carbon alloy as the active material, and the distribution ratio of each component in the negative pole piece 1 is, silicon-carbon alloy: superconducting carbon: sodium carboxymethyl cellulose: styrene-butadiene rubber=96%:1.0% :1.0%:2.0%. After the negative pole piece 1 is cold-pressed (compaction density 1.70g/cc), it is assembled with the positive pole piece, separator, electrolyte and packaging bag to form a finished battery cell.

Others are the same as in Embodiment 2 and will not be repeated here.

Example 4, as shown in Figure 4, differs from Example 3 in that the surface density of the crack 3 in this example is 10000m/mm ² , the width of the crack 3 is 20um, the length of the crack 3 is 12um, and the crack 3 is The cross-sectional shape is triangular and trapezoidal, and the thickness of the pole piece is completely penetrated by cracks 3 . The negative pole piece 1 used is tin alloy as the active material, prepared by stirring according to the negative electrode formula (tin alloy: superconducting carbon: sodium carboxymethyl cellulose: styrene-butadiene rubber = 96%: 1.0%: 1.0%: 2.0%) The negative electrode slurry is obtained, and then the negative electrode slurry is coated on the copper foil current collector to prepare the negative electrode sheet, and then the negative electrode sheet is cold-pressed (the compaction density is 1.70g/cc), and the positive electrode sheet, separator, electrolytic Liquid and packaging bags are assembled into finished cells.

Others are the same as in Embodiment 3 and will not be repeated here.

Example 5, as shown in Figure 5, differs from Example 4 in that the cracks 3 in this example have an areal density of 500m/mm ² , the width of the cracks 3 is 7um, the length of the cracks 3 is greater than 22um, and the cracks The cross-sectional shape of 3 is triangular, rectangular and trapezoidal, and the thickness of the pole piece runs through the crack 3 completely. Negative pole piece 1 used is to adopt graphite and tin alloy as active material, and the distribution ratio of each component in negative pole piece 1 is: graphite+tin alloy: superconducting carbon: sodium carboxymethyl cellulose: styrene-butadiene rubber=96%: 1.0%: 1.0%: 2.0%, stirring and preparing the negative electrode slurry, then coating the negative electrode slurry on the copper foil current collector to prepare the negative electrode sheet, and then cold pressing the negative electrode sheet (the compacted density is 1.70g/ cc), assembled with the positive pole piece, separator, electrolyte and packaging bag to form a finished battery cell.

Comparative example 1, the negative pole piece of this comparative example has no crack structure. The negative electrode sheet used is also obtained by stirring, coating, and cold pressing (the compacted density is 1.70g/cc). The distribution ratio of each component in the negative electrode sheet is graphite: superconducting carbon: sodium carboxymethyl cellulose: styrene-butadiene rubber = 96%: 1.0%: 1.0%: 2.0%. In order to characterize the absorption speed of the negative electrode sheet to the electrolyte in this comparative example, we drop 0.1g of electrolyte solution on the negative electrode sheet after cold pressing, and then measure the time required for the electrode sheet to completely absorb the 0.1g electrode solution, and Recorded in Table 1 for comparison. In addition, we will also conduct 3C discharge and 3C charge rate tests on the batteries, and the test results are recorded in Table 1 for comparison.

Table 1: The time required for the negative electrode sheet to absorb 0.1g of electrolyte in Examples 1-5 and Comparative Example 1, and the test results of 3C discharge rate performance and electric rate after the electrode sheet is assembled into a battery.

As can be seen from Table 1, after adopting the lithium-ion battery pole piece with the crack structure proposed by the present invention, the absorption speed of the electrolyte by the pole piece has been greatly improved; when the negative electrode pole piece in the battery has a crack structure, the battery The charging rate performance will be significantly improved.

According to the disclosure and teaching of the above specification, those skilled in the art to which the present invention pertains can also change and modify the above embodiment. Therefore, the present invention is not limited to the above-mentioned specific implementation manners, and any obvious improvement, substitution or modification made by those skilled in the art on the basis of the present invention shall fall within the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (9)

1. the cathode pole piece of a lithium ion battery, it is characterized in that: described cathode pole piece is provided with crack structtire, and described crack structtire opening is arranged on the pole piece top layer.

2. the cathode pole piece of lithium ion battery according to claim 1 is characterized in that: the active material in the described cathode pole piece is at least a in graphite, silicon, silicon-carbon alloy and the ashbury metal.

3. the cathode pole piece of lithium ion battery according to claim 1, it is characterized in that: the width of the crackle in the described crack structtire is 1 ~ 20um.

4. the cathode pole piece of lithium ion battery according to claim 3, it is characterized in that: the width of the crackle in the described crack structtire is 1 ~ 5um.

5. the cathode pole piece of lithium ion battery according to claim 1 is characterized in that: the length of the crackle in the described crack structtire is 5um at least.

6. the cathode pole piece of lithium ion battery according to claim 1, it is characterized in that: the surface density of the crackle in the described crack structtire is 10 ~ 10000m/m ²

7. the cathode pole piece of lithium ion battery according to claim 6, it is characterized in that: the surface density of the crackle in the described crack structtire is 100 ~ 1000m/m ²

8. the cathode pole piece of lithium ion battery according to claim 1 is characterized in that: the cross sectional shape of the crackle in the described crack structtire is at least a in triangle, the trapezoidal and rectangle.

9. lithium ion battery, comprise anode pole piece, cathode pole piece, be arranged at barrier film and electrolyte between described anode pole piece and the described cathode pole piece, it is characterized in that: each cathode pole piece with crack structtire is as electrodes of lithium-ion batteries in the described lithium ion battery employing claim 1 ~ 8.

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