CN-224217466-U - Wound electrode assembly for forming a pole piece of the wound electrode assembly and a secondary battery

CN224217466UCN 224217466 UCN224217466 UCN 224217466UCN-224217466-U

Abstract

The present application relates to a wound electrode assembly for forming a pole piece of the wound electrode assembly and a secondary battery. The electrode plate comprises a current collector layer and an active material layer, wherein the active material layer is coated on at least one surface of the current collector layer, the active material layer comprises at least two target areas, the target areas correspond to bending parts of the winding electrode assembly, the target areas comprise a plurality of grooves formed in the active material layer, the grooves extend along the width direction of the electrode plate, the grooves are provided with top ends and bottom ends, and the section width of the grooves in the thickness direction of the electrode plate is gradually reduced from the top ends to the bottom ends. According to the pole piece, the grooves are formed in the target area of the active material layer, so that the extrusion stress of the active material layer in the bending area after being wound is reduced, the fracture risk in the hot pressing process can be reduced, and the occurrence of the light transmission problem is avoided.

Inventors

Lv Haiwang
JIANG YELIANG
WANG GANGQING
GAO LIPENG
TANG WEI
CAO HUI

Assignees

瑞浦兰钧能源股份有限公司

Dates

Publication Date: 20260508
Application Date: 20250407

Claims (10)

1. A pole piece for forming a coiled electrode assembly, comprising a current collector layer and an active material layer, wherein the active material layer is coated on at least one surface of the current collector layer; The active material layer includes at least two target areas corresponding to the bent portions of the rolled electrode assembly, the target areas include a plurality of grooves formed in the active material layer, the grooves extend in a width direction of the electrode sheet, the grooves have top and bottom ends, and a cross-sectional width of the grooves in a thickness direction of the electrode sheet is gradually reduced from the top end to the bottom end.
2. A pole piece according to claim 1, characterized in that between two adjacent grooves there is a thinned portion, the thickness of which is less than or equal to the coating thickness of the active substance layer.
3. The pole piece of claim 2, wherein the thinned portion has a bottom portion closer to the current collector layer and a top portion farther from the current collector layer, the thinned portion having a cross-sectional width in a thickness direction of the pole piece that gradually increases from the top portion to the bottom portion.
4. The pole piece of claim 1, wherein the plurality of grooves have a spacing therebetween.
5. A pole piece as claimed in claim 4, wherein the spacing increases or decreases progressively from the middle to both sides of the target area.
6. The pole piece of claim 1, wherein the bottom end is located at the current collector layer or at the active material layer.
7. A pole piece according to claim 1, characterized in that the tip of the groove has a first cross-sectional width W1 in the thickness direction of the pole piece, with a spacing W3 between adjacent grooves, wherein 0< W1 +.2 mm, and/or 0< W3 +.5 mm.
8. A pole piece according to claim 7, characterized in that w1=w3, or W1< W3.
9. The pole piece of claim 7, wherein the bottom end of the recess has a second cross-sectional width W2 in the thickness direction of the pole piece, wherein w2=0 and w1=w3.
10. A wound electrode assembly for a secondary battery, which is wound with the electrode sheet according to any one of claims 1 to 9, comprising a bent portion, wherein the active material layer located at the inner ring is separated by the grooves at the bent portion to form a plurality of gaps having a width of 0 or more.

Description

Wound electrode assembly for forming a pole piece of the wound electrode assembly and a secondary battery Technical Field The present application relates to the field of secondary batteries, and in particular, to a wound electrode assembly for forming a pole piece of the wound electrode assembly and a secondary battery. Background The secondary battery occupies a very critical position in the current energy storage field and is widely applied to various electronic equipment, electric automobiles and other aspects. In the production and manufacturing process of the secondary battery, the winding hot-pressing process has a non-negligible important influence on the performance and quality of the battery. However, in this process, as the coating surface density increases, the compaction design increases correspondingly. In the manufacturing process of the winding battery core, after the winding battery core is hot-pressed, the inner ring can be transparent or broken, and the safety of the battery core is seriously affected. In addition, the positive plate has certain limitations in terms of material selection and preparation process. In order to achieve high energy density and high multiplying power, the thickness of the polar plate is further controlled while the polar plate is increased in surface density, so that the compacted density is continuously increased. In this way, the problems of breakage, wrinkling and the like are easily generated in the winding hot-pressing process, and the light transmission phenomenon is further caused. These problems not only affect the quality and appearance of the finished product of the secondary battery, but also may cause a series of serious consequences such as increased internal resistance, accelerated capacity decay, reduced safety and the like of the secondary battery, thereby greatly limiting the improvement of the performance of the secondary battery and the expansion of the application range. Disclosure of utility model Aiming at the problem of light transmission caused by easy breakage in the hot-pressing process of battery winding, the application provides a winding type electrode assembly for forming a pole piece of the winding type electrode assembly and a secondary battery, which can solve and relieve the problem of breakage of the pole piece of the inner ring of a winding core in the hot-pressing process. The technical scheme adopted by the application for solving the technical problems is that the pole piece for forming the coiled electrode assembly comprises a current collector layer and an active material layer, wherein the active material layer is coated on at least one surface of the current collector layer, the active material layer comprises at least two target areas, the target areas correspond to bending parts of the coiled electrode assembly, the target areas comprise a plurality of grooves formed in the active material layer, the grooves extend along the width direction of the pole piece, the grooves are provided with top ends and bottom ends, and the section width of the grooves in the thickness direction of the pole piece is gradually reduced from the top ends to the bottom ends. In an embodiment of the present application, a thinned portion is provided between two adjacent grooves, and the thickness of the thinned portion is less than or equal to the coating thickness of the active material layer. In an embodiment of the present application, the thinned portion has a bottom portion near the current collector layer and a top portion distant from the current collector layer, and a cross-sectional width of the thinned portion in a thickness direction of the pole piece gradually increases from the top portion to the bottom portion. In an embodiment of the present application, a space is provided between the plurality of grooves, and a plurality of spaces are equal or unequal. In one embodiment of the present application, the distance gradually increases or decreases from the middle to both sides of the target area. In an embodiment of the application, the bottom end is located at the current collector layer or at the active material layer. In an embodiment of the application, the top ends of the grooves have a first section width W1 in the thickness direction of the pole piece, and a distance W3 is arranged between adjacent grooves, wherein 0< W1 is less than or equal to 2mm, and/or 0< W3 is less than or equal to 5mm. In one embodiment of the present application, w1=w3, or W1< W3. In an embodiment of the application, the bottom end of the groove has a second cross-sectional width W2 in the thickness direction of the pole piece, wherein w2=0 and w1=w3. The application also provides a coiled electrode assembly of a secondary battery, which is coiled by the pole piece, and comprises a bending part, wherein the active material layer positioned on the inner ring is separated by the groove at the bending part to form a plurality of gaps, and the width of