CN-122025844-A - Lithium ion battery cell and battery

Abstract

The invention relates to the technical field of batteries, in particular to a lithium ion battery core and a battery comprising the lithium ion battery core. The positive electrode plate, the diaphragm and the negative electrode plate are stacked and wound to form a winding core, the winding core comprises a flat area and a bending area, the positive electrode plate at least partially located in the flat area comprises a positive electrode current collector and a positive electrode active material layer located on at least one side surface of the positive electrode current collector, the positive electrode plate at least partially located in the bending area comprises a positive electrode current collector, a positive electrode active material layer located on at least one side surface of the positive electrode current collector and a functional layer located on at least one side surface of the positive electrode active material layer, which is far away from the positive electrode current collector, and the functional layer comprises graphene materials. The battery of the invention has better cycle performance and safety performance.

Inventors

• LI HUIFANG
• MENG XUEPING
• HU JIALI
• Sun Shangqing
• LIN YONGTAO

Assignees

• 珠海冠宇电池股份有限公司

Dates

Publication Date

20260512

Application Date

20241112

Claims (10)

1. 1. The lithium ion battery cell is characterized by comprising a positive plate, a diaphragm and a negative plate, wherein the positive plate, the diaphragm and the negative plate are laminated and wound to form a winding core, and the winding core comprises a straight area and a bending area; The positive plate at least partially positioned in the flat region comprises a positive current collector and a positive active material layer positioned on at least one side surface of the positive current collector; the positive plate at least partially positioned in the bending region comprises the positive current collector, the positive active material layer positioned on at least one side surface of the positive current collector and a functional layer positioned on at least one side surface of the positive active material layer, which is away from the positive current collector; The functional layer comprises graphene substances.
2. 2. The lithium ion battery cell according to claim 1, wherein a surface of the functional layer located on one side surface of the positive electrode sheet facing away from the positive electrode current collector has a plurality of concave portions; preferably, the concave portion is located on the functional layer on a side of the positive electrode sheet close to the winding center of the winding core.
3. 3. The lithium ion battery cell according to claim 1 or 2, wherein the graphene-based substance comprises at least one of graphene, graphene oxide, and reduced graphene oxide.
4. 4. The lithium ion battery cell according to claim 2, wherein the positive electrode active material layer includes a positive electrode active material, and a particle diameter Dv10 of the positive electrode active material and a depth d of the concave portion satisfy that Dv 10. Ltoreq.d. Ltoreq.25 μm.
5. 5. The lithium ion cell according to claim 2, wherein the depth d of the recess is 5-25 μm, preferably 10-20 μm; And/or the pitch of the concave parts is 20 μm to 500 μm, preferably 300 μm to 400 μm; And/or the area of orthographic projection of the concave part on the surface of the functional layer is 900 μm 2 -40000μm 2 , preferably 8000 μm 2 -10000μm 2 .
6. 6. The lithium ion cell of claim 1 or 2, wherein the raman spectrum of the functional layer has a D peak and a G peak, the ratio I D /I G of the intensity I D of the D peak to the intensity I G of the G peak being 1-2, preferably 1.2-2, more preferably 1.4-1.8.
7. 7. The lithium ion cell according to claim 1 or 2, wherein the area resistance of the positive electrode sheet located in the flat region is 100mΩ -10000mΩ, preferably 960mΩ -980mΩ; and/or the area resistance of the positive plate positioned in the bending area is 50mΩ -5000mΩ, preferably 300mΩ -900mΩ.
8. 8. The lithium ion cell according to claim 1 or 2, wherein the ratio of the thickness of the positive electrode active material layer to the thickness of the functional layer is (4-200): 1, preferably (20-80): 1.
9. 9. The lithium ion battery cell according to claim 1 or 2, wherein the winding core has the bending regions on both sides and the straight regions connected to the bending regions on both sides, the positive electrode sheet of the bending region on either side includes n layers from inside to outside, a dimension L of the functional layer on the nth layer of the positive electrode sheet in the direction of the winding core from inside to outside satisfies L=kχ pi x [ d1+d2+ (n-1) × (d1+2 x d2+d3) ], d1 is a thickness of the negative electrode sheet, d2 is a thickness of the separator, d3 is a thickness of the positive electrode sheet, n≥1, k is 1-1.2.
10. 10. A battery comprising a lithium-ion cell according to any one of claims 1-9.

Description

Lithium ion battery cell and battery Technical Field The invention relates to the technical field of batteries, in particular to a lithium ion battery core and a battery comprising the lithium ion battery core. Background With the development of lithium ion battery technology, higher requirements are put on the power of the battery. In the multiplying power discharging process of the high-power battery, the first problem is that lithium is easy to separate out from a bending area of the battery, so that the risk of short circuit of the battery is increased, the risk of thermal runaway of the battery is increased, and the second problem is that the temperature of the surface of the battery is higher, the temperature rise is larger, and the risk of thermal runaway of the battery is higher. Therefore, it is important to improve the easiness of lithium precipitation in the bending region of a high-power battery and to reduce the risk of thermal runaway due to a large increase in the surface temperature of the battery. Disclosure of Invention The invention aims to solve the problems that lithium is easy to separate out from a bending area of a high-power battery and high thermal runaway risk is caused by large surface temperature rise in the prior art, and provides a lithium ion battery cell and a battery comprising the lithium ion battery cell. The positive plate in the lithium ion battery core is provided with the functional layer in a specific area, and the functional layer is provided with the graphene substance, so that the integral resistance of the positive plate can be reduced and the heat dissipation capacity of the positive plate can be improved on the premise of less influence on normal deintercalation of lithium ions, and the occurrence of thermal runaway can be effectively delayed. The bending area of the winding core is provided with the functional layer, so that the migration speed of lithium ions from the positive electrode plate to the negative electrode plate can be slowed down, the problem that lithium is easy to separate out from the bending area is effectively solved, the problem of heat accumulation caused by larger stress of the bending area can be solved, and the risk of thermal runaway of the battery is further reduced. The battery comprising the lithium ion battery core has better cycle performance and safety performance. The high-power battery in the related art has the problems that lithium is easy to separate out from a bending area and the risk of thermal runaway is high. The inventor of the present invention has found through research that, firstly, in the high-rate discharge process, the temperature rise of the battery mainly comes from electrochemical reaction heat participated by lithium ions and heat generation of pole piece impedance power loss, especially the positive pole piece, and the poor conductivity of the positive active material in the positive pole piece leads to large impedance of the positive pole piece and slow heat transfer. Second, in the high-rate charging process, since the transmission speed of lithium ions is fast, and in the bending region of the battery, especially when the positive electrode sheet near the winding center corresponds to the negative electrode sheet deviating from the winding center, the negative electrode sheet cannot completely accommodate lithium ions extracted from the positive electrode sheet, which may cause precipitation of lithium ions at the position. In order to ensure that the winding structure of the winding core is not easy to loosen, the binding force born by the bending area is larger than that of the straight area, and the positive plate of the bending area is in close contact with the diaphragm and the negative plate, so that heat at the part of the bending area is difficult to release, heat is accumulated, and thermal runaway is easy to cause. Based on the above findings, the inventors of the present invention have conducted a great deal of targeted studies and have proposed the following: The invention provides a lithium ion battery cell, which comprises a positive plate, a diaphragm and a negative plate, wherein the positive plate, the diaphragm and the negative plate are laminated and wound to form a winding core, the winding core comprises a straight area and a bending area, the positive plate at least partially positioned in the straight area comprises a positive current collector and a positive active material layer positioned on at least one side surface of the positive current collector, the positive plate at least partially positioned in the bending area comprises the positive current collector, the positive active material layer positioned on at least one side surface of the positive current collector and a functional layer positioned on at least one side surface of the positive active material layer, which is far away from the positive current collector, and the functional layer comprises graphene substances. Th