CN118553853A - Pole piece, winding cell and battery - Google Patents

Abstract

The application provides a pole piece, a winding electric core and a battery. The pole piece comprises a current collector, an active material layer and an insulating layer. The current collector includes two opposing surfaces. At least one of the two surfaces of the current collector is provided with an active material layer. The current collector includes an empty foil region beyond the active material layer along the length of the current collector. The active material layer and the insulating layer are disposed along the length direction. One part of the insulating layer is overlapped with the empty foil area, and the other part is overlapped with the active substance layer. The insulating layer covers the edges of the active material layer. The pole piece can solve the problem of short circuit in the battery caused by the penetration of burrs on the current collector through the diaphragm.

Description

Electrode sheets, wound cells and batteries

The present invention is a divisional application of the invention patent application with application number 202210199797.7 filed on March 1, 2022 and invention name “Pole piece, wound battery cell and battery”.

Technical Field

The present application relates to the field of battery technology, and in particular to a pole piece, a wound battery cell and a battery.

Background Art

Batteries are widely used in products such as smartphones, power tools and new energy vehicles due to their high energy density, low self-discharge and good recyclability. However, batteries have certain safety risks, and battery safety issues have always restricted the progress of power battery industrialization.

The battery includes a battery cell. The battery cell includes a positive electrode sheet, a separator and a negative electrode sheet. The positive electrode sheet, the separator and the negative electrode sheet can form a winding core by a winding process. The separator is used to insulate and isolate the positive electrode sheet from the negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer covers the surface of the positive electrode current collector. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer covers the surface of the negative electrode current collector.

The positive electrode current collector and the negative electrode current collector are usually made of metal materials. Metal dust will be generated during the processing of the positive electrode current collector or the negative electrode current collector. The metal dust will adhere to the boundary between the current collector and the active material layer to form burrs. The burrs can easily penetrate the diaphragm, causing the positive electrode sheet and the negative electrode sheet to short-circuit through the burrs, causing the battery to heat up, and even the battery will catch fire and cause a fire.

Summary of the invention

The present application provides a pole piece, a wound battery cell and a battery, which can solve the problem that burrs on a current collector penetrate a diaphragm and cause a short circuit inside the battery.

In one aspect, the present application provides a pole piece, comprising:

a current collector including two opposing surfaces;

An active material layer, wherein at least one of the two surfaces of the current collector is provided with the active material layer, and along the length direction of the current collector, the current collector includes an empty foil area beyond the active material layer;

The insulating layer, the active material layer and the insulating layer are arranged along the length direction, a part of the insulating layer overlaps with the empty foil area, and another part overlaps with the active material layer, and the insulating layer covers the edge of the active material layer.

In the pole piece of the embodiment of the present application, the insulating layer provided can cover the burrs on the boundary between the current collector and the active material layer, thereby preventing the burrs from penetrating the diaphragm and causing electrical connection between adjacent pole pieces and short circuit after the wound battery cell is formed. This is beneficial to reducing the probability of battery heating or even fire due to short circuit, and reducing the possibility of safety hazards during battery use.

According to one embodiment of the present application, the active material layer includes a first layer body and a second layer body connected to each other, the first layer body and the second layer body are arranged along the length direction, the second layer body is located on the side of the first layer body close to the insulating layer, and the insulating layer partially covers at least a portion of the second layer body.

According to an embodiment of the present application, the thickness of the second layer gradually decreases along a direction away from the first layer.

According to one embodiment of the present application, the active material layer includes two second layer bodies located on both sides of the first layer body, and the pole piece includes two insulating layers respectively located on the second layer bodies on both sides. Along the length direction, an empty foil area is respectively arranged on both sides of the active material layer, and the pole piece also includes a pole ear arranged in the empty foil area, and the pole ear is arranged on the side of the insulating layer facing away from the active material layer.

According to an embodiment of the present application, active material layers are respectively provided on the two surfaces of the current collector, and along the length direction, the edges of the two active material layers facing the pole ears are flush with each other, and the edges of the two active material layers facing away from the pole ears are staggered with each other.

According to one embodiment of the present application, the portion of the current collector that extends beyond the second layer forms a hollow foil area, and along the length direction, an hollow foil area is provided on one side of the active material layer, and the edge of the active material layer away from the hollow foil area and the edge of the current collector away from the hollow foil area are aligned.

According to one embodiment of the present application, active material layers are respectively provided on two surfaces of the current collector, and along the length direction, the two active material layers are respectively located at the edges of the empty foil area and are staggered with each other.

According to an embodiment of the present application, the thickness of the insulating layer is less than or equal to the thickness of the first layer body.

According to an embodiment of the present application, the thickness of the insulating layer is greater than 10 μm.

According to one embodiment of the present application, along the width direction of the current collector, the width of the insulating layer is greater than or equal to the width of the active material layer.

According to one embodiment of the present application, along the width direction of the current collector, the width of the insulating layer is greater than the width of the active material layer, and the difference between the width of the insulating layer and the width of the active material layer is less than or equal to 2 mm.

According to one embodiment of the present application, along the length direction, the size of the insulation layer ranges from 2 mm to 20 mm.

According to an embodiment of the present application, the insulating layer includes an insulating filler, and the resistivity of the insulating filler is greater than 10 ⁷ Ω·m.

According to an embodiment of the present application, the insulating layer further includes a binder, and the mass content of the binder in the insulating layer ranges from 1% to 10%.

On the other hand, the present application provides a wound battery cell, comprising a pole piece as described in the above embodiment.

On the other hand, the present application provides a battery, including a wound battery cell as described in the above embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

FIG1 is a schematic diagram of a battery structure according to an embodiment of the present application;

FIG2 is a schematic diagram of an exploded structure of a battery according to an embodiment of the present application;

FIG3 is a schematic diagram of a partial cross-sectional structure of a battery cell according to an embodiment of the present application;

FIG4 is a schematic diagram of a partially expanded cross-sectional structure of a pole piece according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a partially expanded cross-sectional structure of a pole piece according to another embodiment of the present application.

Description of reference numerals:

100, battery; 110, housing; 120, cover;

200. Winding the battery cell;

300, pole piece;

310, current collector; 311, empty foil area;

320, active material layer; 321, first layer body; 322, second layer body;

330, insulation layer;

340, ear;

400, diaphragm;

X, thickness direction; Y, length direction; Z, width direction.

The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments.

DETAILED DESCRIPTION

Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

The battery 100 of the embodiment of the present application may include a lithium-ion secondary battery, a lithium-sulfur battery, or a sodium-lithium-ion battery, etc., which is not limited in the present application. The battery 100 is generally divided into a square battery and a soft-pack battery according to the packaging method, which is not limited in the present application.

The device of the embodiment of the present application can be a mobile device such as a vehicle, a ship, a small aircraft, etc. Taking a vehicle as an example, the vehicle of the present application can be a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle. The battery 100 can be used as a driving power source for the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle. Exemplarily, the battery 100 provides electrical energy for the drive motor. The drive motor is connected to the wheels on the vehicle through a transmission mechanism to drive the vehicle to move. Specifically, the battery 100 can be horizontally arranged at the bottom of the vehicle.

As shown in Figures 1 and 2, the battery 100 includes a battery cell, a shell 110 and a cover 120. The shell 110 is used to accommodate the battery cell. After the battery cell is placed in the shell 110, the cover 120 is sealed and connected to the shell 110. The battery cell includes a positive electrode sheet, a separator 400 and a negative electrode sheet. The positive electrode sheet, the separator 400 and the negative electrode sheet are formed into a wound battery cell 200 using a winding process. The battery 100 mainly relies on the movement of lithium ions between the positive electrode sheet and the negative electrode sheet for charging and discharging. During the charging process of the battery 100, lithium ions are deintercalated from the positive electrode sheet and then embedded into the negative electrode sheet through the separator 400.

The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The positive electrode sheet and the negative electrode sheet can use the same coating process. Taking the positive electrode sheet as an example, in the coating process of the positive electrode sheet, the slurry is intermittently and evenly coated on the surface of the conveyed positive electrode current collector, and after drying, a positive electrode active material layer attached to the surface of the positive electrode current collector is formed, thereby forming a positive electrode sheet.

After the pole piece 300 is coated and dried, the peeling strength between the active material in the active material layer 320 and the current collector 310 is low, so the active material layer 320 can be rolled to enhance the bonding strength between the active material and the current collector 310, thereby preventing the active material from peeling off during the immersion of the electrolyte or the use of the battery 100. At the same time, the thickness of the pole piece 300 after rolling is reduced, thereby reducing the volume of the wound battery cell 200 and improving the energy density of the battery 100.

The positive electrode current collector and the negative electrode current collector are usually made of metal materials. Metal dust will be generated during the processing of the positive electrode current collector or the negative electrode current collector. The metal dust will adhere to the boundary between the current collector 310 and the active material layer 320 to form burrs. The burrs can easily penetrate the diaphragm 400, causing the positive electrode sheet and the negative electrode sheet to be connected through the burrs and short-circuited, causing the battery 100 to generate heat, and even the battery 100 will catch fire and cause a fire.

Based on the above problems, the applicant has improved the structure of the pole piece 300 , and the embodiments of the present application are further described below.

As shown in FIG. 3 and FIG. 4 , the pole piece 300 of the embodiment of the present application includes a current collector 310, an active material layer 320 and an insulating layer 330. Along the thickness direction X of the current collector 310, the current collector 310 includes two opposite surfaces. At least one of the two surfaces of the current collector 310 is provided with an active material layer 320. In some examples, both surfaces of the current collector 310 may be provided with an active material layer 320.

Along the length direction Y of the current collector 310, the current collector 310 includes an empty foil area 311 that exceeds the active material layer 320. It should be noted that the surface of the current collector 310 located in the empty foil area 311 is not provided with the active material layer 320. The active material layer 320 and the insulating layer 330 are arranged along the length direction Y. A portion of the insulating layer 330 overlaps the empty foil area 311, and another portion overlaps the active material layer 320. The insulating layer 330 covers the edge of the active material layer 320, that is, the edge of the active material layer 320 is located below the insulating layer 330.

The current collector 310 is usually made of metal materials. In some examples, the metal sheet can be cut into current collectors 310 of different sizes by laser cutting. Metal dust is generated during the laser cutting of the metal sheet. After the metal sheet is laser cut to form the current collector 310, the metal dust will adhere to the boundary between the current collector 310 and the active material layer 320 to form burrs. When the burrs penetrate the diaphragm 400, the burrs connect the two pole pieces 300 with opposite polarities, which will cause a short circuit inside the battery 100.

In the pole piece 300 of the embodiment of the present application, the insulating layer 330 provided can cover the burrs on the boundary between the current collector 310 and the active material layer 320, thereby preventing the burrs from penetrating the diaphragm 400 and causing electrical connection and short circuit between adjacent pole pieces 300 after the wound battery cell 200 is formed, which is beneficial to reducing the probability of heating of the battery 100 or even fire due to short circuit, and reducing the possibility of safety hazards during the use of the battery 100.

In some achievable embodiments, as shown in FIG. 4 and FIG. 5 , the active material layer 320 of the embodiment of the present application includes a first layer body 321 and a second layer body 322 connected to each other. The first layer body 321 and the second layer body 322 are arranged along the length direction Y. The second layer body 322 is located on a side of the first layer body 321 close to the insulating layer 330, and a portion of the insulating layer 330 covers at least a portion of the second layer body 322.

In the rolling process after the coating process, the roller rolls the active material layer 320 along the length direction Y of the current collector 310, thereby improving the bonding strength between the active material in the active material layer 320 and the current collector 310. The roller gradually moves from the current collector 310 to the active material layer 320, and the edge of the active material layer 320 is first subjected to the roller pressure of the roller, which is prone to powdering, thereby affecting the performance of the battery 100. It should be noted that the powdering phenomenon refers to the part of the active material layer 320 coated on the current collector 310 falling off from the current collector 310.

The edge of the active material layer 320 of the embodiment of the present application is provided with an insulating layer 330. Therefore, on the one hand, the insulating layer 330 can relieve the roller pressure of the pressure roller on the edge of the active material layer 320, thereby reducing the possibility of powder falling from the edge of the active material layer 320; on the other hand, a part of the insulating layer 330 is also stacked with the empty foil area 311, and the binder contained in the insulating layer 330 can improve the bonding force between the edge of the active material layer 320 and the current collector 310, so that when the pressure roller acts on the edge of the active material layer 320, the phenomenon of powder falling from the edge of the active material layer 320 can be more effectively avoided.

In some examples, the first layer 321 and the second layer 322 may be made of the same material. The first layer 321 and the second layer 322 may also be an integrated structure, thereby improving the coating efficiency of the active material layer 320 and further improving the processing efficiency of the pole piece 300 .

In some achievable manners, as shown in FIG4 and FIG5 , the thickness of the second layer 322 gradually decreases in a direction away from the first layer 321 , that is, the thickness of the second layer 322 gradually increases in a direction approaching the first layer 321 .

In the rolling process, along the length direction Y, the pressure roller acts on the second layer 322 and the first layer 321 in sequence from one end of the current collector 310. As the thickness of the second layer 322 gradually increases, the force of the pressure roller acting on the second layer 322 also gradually increases, thereby alleviating the roller pressure on the second layer 322 and reducing the probability of powder loss in the second layer 322.

In some examples, in order to improve the energy density of the battery 100, the pole piece 300 is usually processed by gap coating, so part of the current collector 310 is the empty foil area 311. In the coating process, the slurry will gradually decrease when it is applied to the empty foil area 311, so that the part of the current collector 310 located in the empty foil area 311 will not be coated with the active material layer 320. The area where the slurry gradually decreases forms a second layer 322 with a gradually decreasing thickness.

In some achievable ways, as shown in FIG. 4 , the active material layer 320 of the embodiment of the present application includes two second layer bodies 322 located on both sides of the first layer body 321. The pole piece 300 includes two insulating layers 330 located on the second layer bodies 322 on both sides. Along the length direction Y, an empty foil area 311 is respectively provided on both sides of the active material layer 320. The pole piece 300 also includes a pole ear 340 provided in the empty foil area 311. The pole ear 340 is provided on the side of the insulating layer 330 facing away from the active material layer 320.

In some examples, the wound cell 200 may adopt a structure in which the pole tab 340 is placed in front. The pole tab 340 is disposed in one of the empty foil areas 311 of the current collector 310. Exemplarily, the pole tab 340 and the current collector 310 may be fixed by a welding process. After the wound cell 200 undergoes the winding process, along the thickness direction X, the pole tab 340 is located on a fold of the wound cell 200 near the center area. A distance is provided between the pole tab 340 and the second layer 322, thereby reserving sufficient operating space for coating the insulating layer 330 to improve the processing efficiency of the pole piece 300.

In some examples, when the wound battery cell 200 adopts a structure in which the tab 340 is placed in front, an empty foil area 311 is provided on both sides of the active material layer 320. The insulating layer 330 is provided in the empty foil area 311 close to the starting direction of the roller movement. In the rolling process, the roller gradually acts on the active material layer 320 from the current collector 310. Providing the insulating layer 330 at the edge of the active material layer 320 can alleviate the force of the roller, thereby avoiding the phenomenon of powder falling due to the force on the edge of the active material layer 320 close to the starting direction of the roller movement.

In some achievable ways, the two surfaces of the current collector 310 of the embodiment of the present application are each provided with an active material layer 320. Along the length direction Y, the edges of the two active material layers 320 facing the pole ear 340 are flush with each other, and the edges of the two active material layers 320 facing away from the pole ear 340 are staggered from each other, so that the lengths of the active material layers 320 on the two side surfaces of the current collector 310 are different. It should be noted that, as shown in Figures 4 and 5, staggering means that the extension lengths of the active material layers 320 on the upper and lower sides are different, that is, the projections of the boundaries of the active material layers 320 on the upper and lower sides away from the pole ear 340 in the thickness direction X do not overlap.

In some examples, the active material layer 320 may contain a positive electrode active material. Along the thickness direction X, the length of the active material layer 320 beyond the upper surface of the current collector 310 is greater than the length of the active material layer 320 beyond the lower surface of the current collector 310, that is, along the length direction Y, the lengths of the active material layer 320 on both sides of the current collector 310 are different.

After the wound cell 200 is formed by the winding process, the side of the current collector 310 of the outermost pole piece 300 of the wound cell 200 away from the pole tab 340 will not play an energy role. Therefore, the provision of the empty foil area 311 can reduce the size of the wound cell 200, thereby facilitating the improvement of the energy density of the battery 100. The active material layer 320 on the side of the current collector 310 facing the pole tab 340 can interact with the active layer containing the negative electrode active material on the inside. Therefore, increasing the effective contact area of the active material layer 320 on the side of the current collector 310 facing the pole tab 340 can improve the energy density of the battery 100.

In some examples, in order to improve the energy density of the battery 100, the pole piece 300 is usually processed by gap coating, that is, a hollow foil area 311 is provided in a part of the current collector 310. When the slurry is coated to the adjacent hollow foil area 311, there will be fluctuations in the length direction Y and the thickness direction X, and it is difficult to maintain the consistency of the fluctuation effect of each pole piece 300 through a simple process. Therefore, when the fluctuation causes the capacity of the positive electrode active material on one pole piece 300 to be greater than the capacity of the negative electrode active material on another pole piece 300, the lithium ions deintercalated from the positive electrode active material cannot be completely embedded in the negative electrode active material, and the lithium ions are precipitated on the pole piece 300 containing the negative electrode active material, thereby causing lithium precipitation.

In this embodiment, the active material layer 320 of the pole piece 300 may contain positive electrode active material. Providing the insulating layer 330 at the edge of the active material layer 320 can reduce the area of the active material layer 320, thereby avoiding the lithium precipitation phenomenon caused by the capacity of the positive electrode active material on the active material layer 320 being greater than the capacity of the negative electrode active material on the pole piece 300 with opposite polarity.

In some examples, active material layers 320 are provided on both surfaces of the current collector 310. Insulating layers 330 are provided in the empty foil areas 311 on both sides of the active material layer 320, that is, the number of insulating layers 330 can be four. In the rolling process, the roller gradually acts on the active material layer 320 from the empty foil area 311 on the current collector 310 close to the active material layer 320, and moves through the entire active material layer 320 to the current collector 310 of another empty foil area 311 to complete the entire rolling process. In the starting area of the roller movement, the insulating layer 330 adjacent to the empty foil area 311 in this area can relieve the edge of the active material layer 320 from the force of the roller. In the area where the roller is about to leave the active material layer 320, the insulating layer 330 adjacent to the empty foil area 311 in this area can relieve the edge of the active material layer 320 from the force of the roller, thereby avoiding the phenomenon of powder falling on both edges of the active material layer 320.

In some examples, the active material layer 320 includes an active material, a binder, and a conductive agent. For example, the mass content of the binder in the active material layer 320 is 0.5% to 5%. The mass content of the conductive agent is 0.2% to 4%. For example, the active material can be lithium cobalt oxide, lithium iron phosphate, or lithium nickel cobalt manganese oxide.

In some examples, the current collector 310 may be an aluminum foil. The thickness of the aluminum foil ranges from 4 μm to 20 μm. For example, the thickness of the aluminum foil may be 8 μm, 10 μm, or 15 μm.

In some achievable ways, as shown in FIG. 5 , the portion of the current collector 310 of the embodiment of the present application that exceeds the second layer 322 forms an empty foil area 311. Along the length direction Y, an empty foil area 311 is provided on one side of the active material layer 320. The edge of the active material layer 320 away from the empty foil area 311 and the edge of the current collector 310 away from the empty foil area 311 are aligned, so that the effective contact area of the active material layer 320 away from the empty foil area 311 can be increased, which is beneficial to improve the energy density of the battery 100.

In some examples, the wound cell 200 may adopt a structure in which the tab 340 is placed in the middle or a structure in which multiple tabs 340 are placed. Exemplarily, the wound cell 200 adopts a structure in which the tab 340 is placed in the middle. The structure in which the tab 340 is placed in the middle is to weld the tab 340 to the middle area of the pole piece 300, thereby optimizing the distribution of current density on the pole piece 300 during the charge and discharge process of the battery 100, reducing the internal resistance of the battery 100, and realizing fast charging of the battery 100.

In some achievable embodiments, as shown in FIG5 , active material layers 320 are respectively provided on the two surfaces of the current collector 310. Along the length direction Y, the two active material layers 320 are respectively located at the edges of the empty foil area 311 and staggered with each other, so that the lengths of the active material layers 320 on the two side surfaces of the current collector 310 are different.

In some achievable embodiments, referring to FIG. 4 and FIG. 5 , the thickness of the insulating layer 330 in the embodiment of the present application is less than or equal to the thickness of the first layer body 321 .

A portion of the insulating layer 330 covers a portion of the surface of the empty foil area 311 of the current collector 310, and another portion covers the edge of the second layer 322. The thickness of the second layer 322 decreases in the direction away from the first layer 321, and the thickness of the first layer 321 is the largest. The thickness of the insulating layer 330 is less than or equal to the thickness of the first layer 321, so that on the one hand, the problem that the thickness of the wound battery cell 200 after winding is supported by the insulating layer 330 and becomes larger in the area coated with the insulating layer 330 can be avoided, and the overall thickness consistency of the wound battery cell 200 can be ensured; on the other hand, the problem that the pole piece 300 and the separator 400 in the wound battery cell 200 after winding are supported by the insulating layer 330 and are not in close contact can be avoided, thereby avoiding the loose contact between the pole piece 300 and the separator 400, which increases the movement path of lithium ions and ultimately causes the problem of lithium deposition in the wound battery cell 200.

In some achievable embodiments, the thickness of the insulating layer 330 is greater than 10 μm along the thickness direction X. The height of the burrs generated during the processing of the current collector 310 is less than 10 μm. Therefore, the thickness of the insulating layer 330 is greater than the height of the burrs, which can prevent the burrs from penetrating the diaphragm 400 and causing a short circuit between the two pole pieces 300.

In some embodiments, along the width direction Z of the current collector 310 , the width of the insulating layer 330 is greater than or equal to the width of the active material layer 320 .

In some examples, the width of the insulating layer 330 may be equal to the width of the active material layer 320. During the coating process of the insulating layer 330, when the width of the insulating layer 330 is greater than the width of the active material layer 320, the portion of the insulating layer 330 that exceeds the active material layer 320 may be trimmed to avoid the insulating layer 330 being too wide and increasing the overall size of the wound battery cell 200, thereby affecting the energy density of the battery 100.

In some examples, the width of the insulating layer 330 may be greater than the width of the active material layer 320. Along the width direction Z of the current collector 310, the insulating layer 330 completely covers the edge of the active material layer 320, so that during the rolling process, the entire edge of the active material layer 320 is protected by the insulating layer 330, which can effectively prevent the edge of the active material layer 320 from falling off under the action of the roller.

In some implementations, along the width direction Z of the current collector 310 , the width of the insulating layer 330 is greater than the width of the active material layer 320 . The difference between the width of the insulating layer 330 and the width of the active material layer 320 is less than or equal to 2 mm.

The difference between the width of the insulating layer 330 and the width of the active material layer 320 should be as small as possible, so as to avoid the insulating layer 330 being too wide and increasing the overall size of the wound battery cell 200 , thereby affecting the energy density of the battery 100 .

In some achievable embodiments, along the length direction Y, the size of the insulating layer 330 ranges from 2 mm to 20 mm.

Along the length direction Y, the range of values of the size of the insulating layer 330 will affect the energy density and processing efficiency of the battery 100. In the winding process, when the width of the insulating layer 330 is large and forms one of the layers of the wound battery cell 200, the thickness of the wound battery cell 200 will increase, and the large width of the insulating layer 330 will also cause the corresponding empty foil area 311 to increase accordingly, and the empty foil area 311 is not provided with an active material layer 320, that is, the portion of the wound battery cell 200 with an increased thickness is not provided with an active material layer 320, thereby reducing the energy density of the battery 100.

In some examples, the wound battery cell 200 adopts a structure in which the pole tab 340 is placed in front. An active material layer 320 is provided on each of the two surfaces of the current collector 310. Along the length direction Y, the edges of the two active material layers 320 facing the pole tab 340 are flush with each other. An insulating layer 330 is provided on the active material layer 320 near the pole tab 340. The width of the insulating layer 330 is small. On the one hand, it will affect the insulation effect, and there is a possibility that the insulating layer 330 does not completely cover the burrs, thereby causing a short circuit inside the battery 100; on the other hand, along the length direction Y, due to the position deviation between adjacent pole pieces 300, the small width of the insulating layer 330 will increase the difficulty of adjusting the alignment between adjacent pole pieces 300, thereby reducing the processing efficiency of the pole pieces 300.

In some implementations, the insulating layer 330 includes an insulating filler, and the resistivity of the insulating filler is greater than 10 ⁷ Ω·m.

The resistivity value of the insulating filler should be as large as possible. A larger resistivity value can make the insulating layer 330 have a better insulating effect, so that the insulating layer 330 covering the burrs can have a better isolation effect, avoiding electrical connection between the pole pieces 300 and short circuit.

In some examples, the insulating filler may be at least one of an oxide, a carbide, a nitride, or an inorganic salt.

In some achievable embodiments, the insulating layer 330 further includes a binder, and the mass content of the binder in the insulating layer 330 ranges from 1% to 10%.

The insulating layer 330 containing a binder is coated on the active material layer 320 , which can improve the adhesion between the active material layer 320 and the insulating layer 330 , thereby more effectively preventing the active material layer 320 from falling off during the rolling process.

In some examples, the binder is polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polytetrafluoroethylene, polyhexafluoropropylene, or polymethyl methacrylate.

In some examples, the insulating layer 330 can be formed by spraying, sputtering, deposition, etc.

The present application also provides a wound battery cell 200, comprising a pole piece 300 as in any of the above embodiments. The pole piece 300 and the separator 400 are wound to form the wound battery cell 200 through a winding process.

The present application also provides a battery 100, comprising a wound cell 200 as in any of the above embodiments. The wound cell 200 is placed in a housing 110 and then injected with electrolyte, and the cover 120 and the housing 110 are sealed to form the battery 100. Exemplarily, the cover 120 and the housing 110 may be sealed by welding.

In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, or it can be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

In the embodiments of the present application, the devices or elements referred to or implied must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present application. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise precisely and specifically specified.

The terms "first", "second", "third", "fourth", etc. (if any) in the description and claims of the embodiments of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example.

In addition, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, method, product, or apparatus.

The term "plurality" in this article refers to two or more than two. The term "and/or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character "/" in this article generally indicates that the previous and next associated objects are in an "or" relationship; in a formula, the character "/" indicates that the previous and next associated objects are in a "division" relationship.

It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

It can be understood that in the embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

Claims (15)

1. A pole piece, comprising:

a current collector including two opposing surfaces;

An active material layer, at least one of the two surfaces of the current collector being provided with the active material layer, the current collector including an empty foil region beyond the active material layer along a length direction of the current collector;

the active material layer and the insulating layer are arranged along the length direction, one part of the insulating layer is overlapped with the empty foil area, the other part of the insulating layer is overlapped with the active material layer, and the insulating layer covers the edge of the active material layer;

the pole piece is positioned in the empty foil area, and the pole piece is arranged on one side of the insulating layer, which is opposite to the active material layer;

The active material layer comprises a first layer body and a second layer body which are connected, the first layer body and the second layer body are arranged along the length direction, the second layer body is positioned at one side of the first layer body, which is close to the insulating layer, and at least part of the second layer body is covered by part of the insulating layer;

The two surfaces of the current collector are respectively provided with the active material layers, and the edges of the two active material layers, which are respectively positioned in the empty foil area, are staggered along the length direction.

2. The pole piece of claim 1, wherein the thickness of the second layer decreases progressively in a direction away from the first layer.

3. The pole piece according to claim 1, characterized in that the active material layer comprises two second layer bodies located on both sides of the first layer body, the pole piece comprises two insulating layers located on the second layer bodies on both sides respectively, and one empty foil area is arranged on both sides of the active material layer along the length direction respectively.

4. A pole piece according to claim 3, characterized in that the two surfaces of the current collector are each provided with the active material layer, the edges of the two active material layers facing the pole lugs being flush with each other in the length direction, the edges of the two active material layers facing away from the pole lugs being offset from each other.

5. A pole piece according to claim 1, characterized in that the portion of the current collector that exceeds the second layer forms the hollow foil area, one side of the active substance layer being provided with one of the hollow foil areas along the length direction, the active substance layer being arranged in alignment away from the edges of the hollow foil area and the current collector being arranged away from the edges of the hollow foil area.

6. A pole piece according to claim 5, characterized in that the two surfaces of the current collector are each provided with the active substance layer, the edges of the two active substance layers at the empty foil areas being offset from each other in the length direction.

7. The pole piece of claim 1, wherein the thickness of the insulating layer is less than or equal to the thickness of the first layer body.

8. The pole piece of claim 7, wherein the insulating layer has a thickness greater than 10 μm.

9. The pole piece of claim 1, wherein the width of the insulating layer is greater than or equal to the width of the active material layer along the width direction of the current collector.

10. The pole piece of claim 1, wherein the width of the insulating layer is greater than the width of the active material layer in the width direction of the current collector, and the difference between the width of the insulating layer and the width of the active material layer is less than or equal to 2mm.

11. A pole piece according to claim 1, characterized in that the dimension of the insulating layer along the length direction has a value in the range of 2mm to 20mm.

12. The pole piece of claim 1, wherein the insulating layer comprises an insulating filler having a resistivity greater than 10 ⁷ Ω -m.

13. The pole piece of claim 12, wherein the insulating layer further comprises a binder, the mass content of the binder in the insulating layer ranging from 1% to 10%.

14. A wound cell comprising a pole piece according to any one of claims 1 to 13.

15. A battery comprising a wound cell as claimed in claim 14.