CN115117305A - A kind of preparation method of high compacted density pole piece - Google Patents

Abstract

The invention relates to the technical field of lithium battery pole pieces, and discloses a preparation method of a high compaction density pole piece, which comprises the following steps: 1) coating an A1 coating and a B1 coating on two sides of the pole piece foil respectively; 2) drying the A1 coating and the B1 coating; 3) coating A2 coating and B2 coating on the surfaces of the dried A1 coating and B1 coating; 4) drying the A2 coating and the B2 coating; the surface coating A and the surface coating B are arranged in a staggered manner in the extending direction of the pole piece foil; 5) and rolling the pole piece to the designed thickness. Design surface density is achieved through twice coating, coating surface density and thickness consistency are improved, meanwhile, staggered design is adopted between two coatings, the fact that coatings on two surfaces of a pole piece are sequentially subjected to step stress when the pole piece is rolled is achieved, the problem of material falling caused by overlarge compaction density of a coating head area when the pole piece is rolled under the design of gap coating high compaction density is effectively solved, the rolling appearance reject ratio of the pole piece is reduced, and meanwhile, the pressure drop consistency of a lithium battery is improved.

Description

A kind of preparation method of high compacted density pole piece

technical field

The patent of the present invention relates to the technical field of lithium battery pole pieces, in particular, to a preparation method of a high compacted density pole piece.

Background technique

The pole piece structure has an important impact on the electrical performance and safety of lithium-ion batteries. For the pole piece structure with discontinuous gap coating, whether the equipment is a transfer coating operation or an extrusion coating operation, it is affected by the rheology and thixotropy of the slurry, and the initial coating line position coating (coating The thickness of the head) is often thicker than that of the intermediate coating, and the thickness of the coating at the end of the coating (coating tail) is obviously thinner than that of the intermediate coating.

In the prior art, when the pole piece is designed to be aligned with single- and double-sided coatings, the empty foil area of the pole piece first passes through the slit of the roller press, and then the double-sided coating passes through the slit of the roller press. Force, which often leads to the excessive compaction density in the coating head area and the phenomenon of material dropping. After the dropping of the pole piece, it not only affects the winding design margin of the negative electrode covering the positive electrode in the length direction of the pole piece, but also the falling powder material may fall into the battery. The internal risk of the winding core affects the consistency of the voltage drop of the battery, and even leads to a potential safety hazard for the battery in severe cases.

In order to improve the energy density of lithium-ion batteries, the pole piece design with high compaction density is often pursued, which further increases the risk of excessively compacted coating in the area of the alignment coating head.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for preparing a high-density pole piece, which aims to solve the problem of material dropout of the coating head during rolling under the single and double-sided alignment design of traditional pole piece coating in the prior art.

The present invention is realized in this way, a kind of preparation method of high compacted density pole piece, comprises the following steps:

1) Coating A1 coating and B1 coating respectively on both sides of the pole piece foil;

2) drying the A1 coating and the B1 coating;

3) Recoat A2 coating on the dried A1 coating surface; recoat B2 coating on the dried B1 coating surface;

4) drying the A2 coating and the B2 coating; the A1 coating and the A2 coating form the A surface coating of the pole piece, and the B1 coating and the B2 coating form the B surface coating of the pole piece; the A surface coating The layer and the B-side coating are arranged in a dislocation along the extension direction of the pole piece foil;

5) Roll the pole piece to the design thickness.

Optionally, in step 1), the coating head of the A1 coating and the coating tail of the B1 coating are located at the same end of the pole piece, and the coating tail of the A1 coating and the coating head of the B1 coating are located at the other end of the pole piece. .

Optionally, in step 3), the coating head and the coating tail of the A2 coating are respectively aligned with the coating tail and the coating head of the A1 coating, and the coating head and the coating tail of the B2 coating are respectively aligned with the coating tail and the coating tail of the B1 coating. The applicator head is aligned.

Optionally, in the rolling movement direction of the pole piece, the end of the B-side coating is longer than the end of the A-side coating by a displacement length L.

Optionally, the dislocation length L≥(r(h ₁ -s)-(h ₁ -s) ² /4) ^0.5 , where the roll radius of the rolling machine is r, the roll gap width of the rolling machine is s, and the pole piece is The design thickness after rolling is h ₁ .

Optionally, in step 5), when the pole piece passes through the roll slit of the roller press, the empty foil area, the single-sided coated area and the double-sided coated area of the pole piece sequentially pass through the roller slit of the roller press.

Optionally, in step 5), the pole piece is rolled to the design thickness corresponding to the pole piece coating compaction density of 1.0-2.5 g/cm ³ , and the design thickness h1 of the pole piece after roll pressing is 50-200 μm.

Optionally, when the pole piece passes through the roll slit of the roller press, the B-side coating with the B1 coating tail enters the roll slit of the roller press before the A-side coating with the A1 coating head.

Optionally, in step 1), the areal densities of the A1 coating and the B1 coating are respectively 10%-90% of the designed areal densities of the A-side coating and the B-side coating of the pole piece.

Optionally, the pole piece is a negative pole piece or a positive pole piece of a lithium battery.

Compared with the prior art, the present invention provides a method for preparing a pole piece with high compaction density, which achieves the designed surface density through two coats, improves the surface density and thickness consistency of the coating, and at the same time, between the two coatings. The dislocation design is adopted to realize that the coatings on both sides of the pole piece are successively stressed in steps when being rolled, which effectively alleviates the excessive compaction density of the coating head area when the pole piece is rolled under the high compaction density design of gap coating. The resulting material drop problem not only reduces the appearance defect rate of the pole piece rolling, but also improves the pressure drop consistency of the lithium battery.

Description of drawings

Fig. 1 is the schematic diagram of the preparation method of a kind of high compacted density pole piece provided by the invention;

FIG. 2 is a schematic diagram of the winding of a negative electrode sheet and a positive electrode sheet prepared by a method for preparing a high compacted density polar sheet provided by the present invention.

Description of reference numbers:

100-A topcoat, 110-A1 coating, 120-A2 coating, 111-A1 coating head, 112-A1 coating tail; 200-B top coating, 210-B1 coating, 220-B2 coating, coating head of 211-B1 coating, coating tail of 212-B1 coating; 300-pole sheet foil; 410-upper roll, 420-lower roll;

1- negative electrode sheet; 2- positive electrode sheet, 21- single-sided coating, 22- double-sided coating.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

The implementation of the present invention will be described in detail below with reference to specific embodiments.

The same or similar numbers in the drawings of this embodiment correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation or a specific orientation. structure and operation, so the terms describing the positional relationship in the accompanying drawings are only used for exemplary illustration, and should not be construed as a limitation on this patent, and those of ordinary skill in the art can understand the specific meanings of the above terms according to specific situations.

Referring to Figures 1-2, it is a preferred embodiment provided by the present invention.

A preparation method of a high compaction density pole piece, comprising the following steps:

1) coating A1 coating 110 and B1 coating 210 on both sides of the pole piece foil 300 respectively;

2) drying the A1 coating 110 and the B1 coating 210;

3) recoating A2 coating 120 on the surface of the dried A1 coating 110; recoating the B2 coating 220 on the surface of the dried B1 coating 210;

4) drying the A2 coating 120 and the B2 coating 220; the A1 coating 110 and the A2 coating 120 form the A surface coating 100 of the pole piece, and the B1 coating 210 and the B2 coating 220 form the B surface coating of the pole piece Layer 200; A-side coating 100 and B-side coating 200 are arranged in a dislocation along the extending direction of the pole piece foil 300;

5) Roll the pole piece to the design thickness.

This embodiment provides a method for preparing a pole piece with high compaction density. The designed surface density is achieved through two coatings, which improves the surface density and thickness consistency of the coating. When the pole piece is rolled, the coatings on both sides are successively stressed in steps, which effectively alleviates the problem of material drop caused by the excessive compaction density of the coating head area when the pole piece is rolled under the high compaction density design of gap coating. It not only reduces the appearance defect rate of pole piece rolling, but also improves the pressure drop consistency of lithium batteries.

Specifically, the pole piece foil 300 can be copper foil or aluminum foil, and the upper and lower surfaces of the pole piece foil 300 are coated with A surface coating 100 and B surface coating 200 respectively, which can be applied to the positive electrode or negative electrode of the lithium battery. . Usually, the foil of the negative electrode is made of copper foil, and the foil of the positive electrode is made of aluminum foil.

For example, the negative electrode material of lithium battery includes high-density artificial graphite, conductive agent, binder and other materials (these materials use the negative electrode material of lithium battery in the prior art), and the design compaction density of negative electrode roll pressing is 1.8 g/cm ³ , the negative electrode raw materials are mixed into a uniform slurry that meets technical specifications such as viscosity, solid content, and fineness through the set slurrying process, and then the slurry is sprayed to the Copper foil upper and lower surfaces.

The materials of the A-side coating 100 and the B-side coating 200 may be the same, for example, both are negative electrode materials. When preparing the positive electrode sheet structure, the materials of the A-side coating 100 and the B-side coating 200 are positive electrode materials.

Specifically, in step 1), the coating head 111 of the A1 coating and the coating tail 212 of the B1 coating are located at the same end of the pole piece, and the coating tail 112 of the A1 coating and the coating head 211 of the B1 coating are located at the pole piece the other end of the . This indicates that the coating directions of A1 coating 110 and B1 coating 210 are opposite, eg, A1 coating 110 is coated from front to back, while B1 coating 210 is coated from back to front. The coating directions of the A1 coating 110 and the B1 coating 210 are opposite, so that the coating consistency is better, and the positions of the coating heads of the A1 coating 110 and the B1 coating 210 can be staggered to avoid the coating head of the double-sided coating. The same end of the pole piece leads to the problem that the thickness of the coating head is too large and the material is easy to drop.

Specifically, in step 3), the coating head and the coating tail of the A2 coating 120 are respectively aligned with the coating tail 112 and the coating head of the A1 coating, and the coating head and the coating tail of the B2 coating 220 are respectively aligned with the coating head and the coating tail of the B1 coating 210. The coating tail and the coating head are aligned.

The coating direction of the A2 coating layer 120 is opposite to that of the A1 coating layer 110, and the coating direction of the B2 coating layer 220 is opposite to the coating direction of the B1 coating layer 210, so that the A surface coating 100 and the B surface can be better guaranteed. The consistency of the thickness of the coating layer 200 avoids the problem of rolling material dropout that may be caused by inconsistent thickness.

Specifically, in the rolling moving direction of the pole piece (ie, the moving direction of the pole piece in FIG. 1 ), the end of the B-side coating layer 200 is longer than the end of the A-side coating layer 100 by a displacement length L. In step 5), when the pole piece passes through the roll slit of the roller press, the empty foil area, the single-sided coated area and the double-sided coated area of the pole piece sequentially pass through the roller slit of the roller press.

The starting position of coating is the coating head of the coating, and the position at the end of coating is the coating tail. The thickness of the coating (coating head) at the starting coating line is often thicker than that of the intermediate coating, and the thickness of the coating (coating tail) at the end of coating is obviously thinner than that of the intermediate coating, which is determined by the coating process itself of.

The end of the B-side coating 200 is longer than the end of the A-side coating 100 by a misalignment length L. When the pole piece structure is rolled along its moving direction, the pole piece foil is the first to enter the roll slit of the rolling machine. Empty foil area of material 300, then only one side coated area (e.g. B side coat 200) and both sides coated area (A side coat 100 and B side coat 200 both enter the slit) are sequentially rolled without overlapping The gap length of the coating layer 200 and the coating layer 100 on the A side make the coatings on both sides bear the force successively, which effectively relieves the gap coating and the high compaction density design. The problem of material drop caused by excessive compaction density in the head area.

Preferably, the dislocation length L≥(r(h ₁ -s)-(h ₁ -s) ² /4) ^0.5 , wherein the roll radius of the rolling machine is r, the roll gap width of the rolling machine is s, and the pole piece roll The design thickness after pressing is h ₁ .

When the thickness of the pole piece foil 300 is h ₂ , when the lower roller 420 just touches the coating tail position of the B-side coating 200 and the upper roller 410 contacts the coating head of the A-side coating 100, the dislocation length is the smallest,

Dislocation length L≥(r ² -(r+(sh ₂ )/2-(h ₁ -h ₂ )/2) ² ) ^0.5 =(r(h ₁ -s)-(h ₁ -s) ² /4) ^0.5 ,

If the dislocation length is too long, the material will be wasted, and if the dislocation length is too short, it will not be able to solve the problem of high compaction coating drop. The dislocation length calculated by the above formula is a more suitable dislocation length, and it has also been verified in engineering practice, so that the yield of the pole piece preparation is guaranteed.

Optionally, in step 5), the pole piece is rolled to the design thickness corresponding to the pole piece coating compaction density of 1.0-2.5 g/cm ³ , and the design thickness h1 of the pole piece after roll pressing is 50-200 μm.

Optionally, in step 1), the areal densities of the A1 coating 110 and the B1 coating 210 are respectively 10%-90% of the designed areal densities of the A-side coating 100 and the B-side coating 200 of the pole piece. The designed areal density of the A-side coating 100 or the B-side coating 200 can be achieved by two coats, which can better improve the coating areal density and thickness consistency.

In the following specific embodiment: a 18650 type cylindrical lithium ion battery, the negative electrode comprises materials such as artificial graphite with high compaction density, a conductive agent, a binder and the like, and the negative electrode rolling design compaction density is 1.8g/cm ³ , The negative electrode raw materials are mixed into a uniform slurry that meets the technical indicators such as viscosity, solid content, and fineness through the set slurrying process, and then the slurry is sprayed onto the copper in two times by a double-die extrusion coating machine. Foil surface, including the following steps:

1) Coat the surface of the copper foil with the anode slurry A1 coating 110 and B1 coating 210 in a gap at the same time. Both ends of the A1 coating 110 and B1 coating 210 are designed with dislocation, and the coating head 111 and the coating tail of the A1 coating are respectively The coating tail and coating head of B1 coating 210 are at the same end of the pole piece;

2) drying the A1 coating 110 and the B1 coating 210;

3) Coating A2 coating 120 and B2 coating 220 simultaneously on the surfaces of A1 coating 110 and B1 coating 210 for the second time, wherein the coating tail and coating head of A2 coating 120 are respectively the same as the coating head of A1 coating 110 Aligned with the coating tail, the coating head and coating tail of the B2 coating 220 overlap with the coating tail and coating head of the B1 coating 210 respectively;

4) drying A2 coating 120 and B2 coating 220;

5) After the dried negative electrode sheet passes through the gap between the upper roller 410 and the lower roller 420 of the roller press, it is rolled to a design thickness of 140 μm.

Further, in step 3), two coating production processes are used to form the A surface coating 100 or the B surface coating 200, which can counteract the surface density and thickness consistency of the coating caused by the thicker coating head and the thin coating tail. For poor problems, the difference in thickness between the coating in the edge area and the coating in the middle area can be controlled within ±2μm.

Further, the roll radius of the roller press used is r=400cm, the roll gap width of the upper and lower rollers of the roller press is s=120μm, the design thickness of the pole piece after rolling is h ₁ =130μm, and the thickness of the foil is h ₂ =9μm, according to The coating dislocation length L≥(r ² -(r+(sh ₂ )/2-(h ₁ -h ₂ )/2) ² ) ^0.5 is calculated, the negative electrode coating dislocation length L≥6.3mm.

Further, referring to FIG. 2, in the cylindrical lithium-ion battery winding structure, the coating of the negative electrode sheet 1 should be able to completely cover the coating of the positive electrode sheet 2, and the coating in the edge area will not fall off during rolling, then the coating should not fall off during rolling. The dislocation length between the A-side coating and the B-side coating at the inner end of the negative electrode sheet 1 in the inner ring of the core is designed to be 8 mm, and the dislocation between the A-side coating and the B-side coating of the negative electrode sheet 1 on the outer ring of the core is designed to be 8 mm. The length is designed to be 55mm.

Referring to the preparation method of the above high-density negative electrode sheet, both sides of the positive electrode sheet foil are also coated with a single-sided coating 21 and a double-sided coating 22, respectively, and the single-sided coating 21 and the double-sided coating 22 are also in a dislocation design. , wherein the end of the double-sided coating 22 extends the end dislocation length L of the single-sided coating 21 . According to the winding structure of the positive electrode sheet 2 and the negative electrode sheet 1 designed above, the coating of the negative electrode sheet 1 can completely cover the coating of the positive electrode sheet 2, and the coating in the edge area will not fall off during rolling. In practice, The yield of lithium battery pole pieces has been greatly improved.

The negative electrode sheet 1 produced according to the requirements of the above-mentioned embodiment, the consistency of the coating thickness is obviously improved, the negative electrode sheet 1 after rolling has a good appearance, and there is no abnormal phenomenon such as material drop in the edge area of the coating.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (10)

1. A preparation method of a high compaction density pole piece is characterized by comprising the following steps:

1) coating an A1 coating and a B1 coating on two sides of the pole piece foil respectively;

2) drying the A1 coating and the B1 coating;

3) coating an A2 coating on the surface of the dried A1 coating; coating a B2 coating on the surface of the dried B1 coating;

4) drying the A2 coating and the B2 coating; the A1 coating and the A2 coating form an A top coating of the pole piece, and the B1 coating and the B2 coating form a B top coating of the pole piece; the surface coating A and the surface coating B are arranged in a staggered manner in the extending direction of the pole piece foil;

5) and rolling the pole piece to the designed thickness.

2. The method of claim 1, wherein in step 1), the head of the a1 coating and the tail of the B1 coating are located at the same end of the pole piece, and the tail of the a1 coating and the head of the B1 coating are located at the other end of the pole piece.

3. The method of claim 2, wherein in step 3), the head and tail of the a2 coating are aligned with the head and tail of the a1 coating, respectively, and the head and tail of the B2 coating are aligned with the head and tail of the B1 coating, respectively.

4. The method of claim 3, wherein the end of the B-side coating is longer than the end of the A-side coating by a misalignment length L in the rolling direction of the pole piece.

5. The method of claim 4, wherein the length of the dislocation is L ≧ (r (h) or more ₁ -s)-(h ₁ -s) ² /4) ^0.5 Wherein the radius of the roller press is r, the width of the roller gap of the roller press is s, and the designed thickness of the rolled pole piece is h ₁ 。

6. A process for preparing a high compaction density electrode sheet according to any one of claims 1 to 5 wherein in step 5) the bare foil area, the single coated area only and the double coated area of the electrode sheet are passed sequentially through the nip of a roll press as the electrode sheet is passed through the nip of the roll press.

7. The method for preparing a high compaction density pole piece according to claim 6, wherein the pole piece is rolled in the step 5) until the compaction density of the pole piece coating corresponding to the designed thickness is 1.0-2.5 g/cm ³ Design thickness h of rolled pole piece ₁ Is 50 to 200 μm.

8. The method of claim 6 wherein the B-side coating with the B1 coating tail is fed into the roll slot of the roll press before the a-side coating with the a1 coating head as the pole piece passes through the roll slot of the roll press.

9. The method for preparing a high compaction density pole piece according to any one of claims 1 to 5, wherein in step 1), the areal density of the A1 coating and the B1 coating is 10% to 90% of the designed areal density of the A top coating and the B top coating of the pole piece, respectively.

10. The method for preparing a high compaction density pole piece according to any one of claims 1 to 5 wherein the pole piece is a negative pole piece or a positive pole piece of a lithium battery.

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