WO2017197639A1 - Battery cell and method for forming same - Google Patents

Abstract

The present application relates to the field of power-storage device production, and in particular, to a battery cell and a method for forming same. The battery cell is formed by alternately winding an anode pole piece, a cathode pole piece, and an isolating membrane; the section of the battery cell is of a rounded-corner square structure with four vertex angles being rounded corners. The forming method comprises: a. placing a battery cell to be pressed among a top plane, a bottom plane and two side planes, one side of the battery cell to be pressed perpendicular to the thickness direction being in contact with the bottom plane, and a certain spacing existing between the battery cell to be pressed and each side plane; b. performing hot pressing on the battery cell to be pressed by means of hot pressing, so that the battery cell to be pressed is squeezed by the top plane, the bottom plane and the two side planes together until the battery cell, the section of which is of a rounded-corner square structure with four vertex angles being rounded corners, is formed; and c. shaping to form the battery cell. By means of the forming method provided by the present application, a battery cell, the section of which is of a rounded-corner square structure, can be formed, and the volume energy density of a lithium ion battery is improved.

Description

Battery core and method of forming the same Technical field

The present application relates to the field of energy storage device production, and in particular, to a battery core and a method for forming the same.

Background technique

Problems such as environmental pollution and energy shortage have become increasingly prominent in recent years. Lithium-ion batteries have been widely used in communications and electronic devices, energy storage power stations, new energy vehicles, etc. due to their green environmental protection, high energy density, low self-discharge, long cycle life, etc., which improve energy efficiency and The protection of the environment plays an important role.

The main structure of the lithium ion battery includes an anode pole piece, a cathode pole piece, a separator film, an electrolyte, and an outer casing. The anode and cathode pole pieces and the separator are alternately wound together to form a battery core, which is packaged by external packaging and liquid injection, and then formed into a complete lithium ion battery through a process such as capacity formation.

In order to improve the volumetric energy density of lithium ion batteries, related technologies generally perform hot press shaping on the cells to reduce the thickness of the cells. However, in the process of thickness compression, the cell gradually protrudes to both sides, causing the side of the cell to have an R angle whose radius is almost equal to half the thickness of the cell (see Figure 1), in the case where the thickness of the cell is constant. The larger the R angle is, the larger the width of the cell is, and the more space is wasted, and the volumetric energy density loss is also greater.

Summary of the invention

The present application provides a battery cell and a method of forming the same, which can reduce the loss of volumetric energy density.

A first aspect of the present application provides a battery core formed by alternately winding an anode pole piece, a cathode pole piece, and a separator, the cross section of which is a rounded square structure having four rounded corners.

Preferably, the anode pole piece, the cathode pole piece and the separator are all of uniform thickness.

Preferably, the radius of the apex angle is not less than the sum of the thicknesses of the single layer of the anode pole piece, the cathode pole piece and the separator, and the thickness of the battery core is T, the apex angle Radius Less than T/2.

Preferably, the four apex angles r of the cells are equal.

A second aspect of the present application provides a method of forming a battery cell, comprising the steps of:

a. placing the piezoelectric core to be placed between the top plane, the bottom plane, and the two side planes, wherein the side of the piezoelectric core perpendicular to the thickness direction is in contact with the bottom plane. The piezoelectric core is spaced apart from each of the side planes;

b. hot pressing the piezoelectric core to be pressed, so that a top plane and the bottom plane and the two side planes co-extrude the piezoelectric core until the cross section is four vertex angles Rounded square structure with rounded corners;

c. Forming, forming the battery core.

Preferably, in the step a, the bottom plane and the side planes on both sides together form a placement area, and the to-be-piezoelectric core is placed on the side of the bottom plane and the sides The placement area formed by the plane.

Preferably, in the step a, the side planes on both sides are the same distance from the center of the piezoelectric core to be piezoelectric.

Preferably, in the step b, the side plane is fixed, and the piezoelectric core is subjected to thickness compression after being pressed in the thickness direction, and both sides are convex and are in contact with the side plane and are pressed. .

Preferably, in the step b, the bottom plane and the side plane are both fixed, the top plane moves downward and presses the piezoelectric core to be pressed, and the piezoelectric core is pressed The thickness is compressed, the sides are convex and are in contact with the side plane and are pressed.

Preferably, in the step b, the hot pressing moving speed is 10 to 2000 mm/min, the hot pressing temperature is 70 to 90 ° C, the hot pressing pressure is 3 to 5 t, and the hot pressing time is 150 s.

Preferably, before the step a, the method further comprises the following steps:

d. Adjust the spacing between the two side planes.

The technical solution provided by the present application can achieve the following beneficial effects:

The forming method provided by the present application can form a battery core having a rounded square structure in cross section, thereby more fully utilizing the space on both sides of the battery core, and improving the volumetric energy density of the lithium ion battery.

The above general description and the following detailed description are merely exemplary and are not intended to limit the application.

DRAWINGS

1 is a schematic view showing the outline structure of a battery cell provided by the background art of the present application;

2 is a schematic cross-sectional structural view of a battery cell according to an embodiment of the present application;

3 is a schematic structural view of a battery core according to an embodiment of the present application;

4 is a schematic overall structural view of a cell hot pressing device according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a mating structure of a bottom hot press block and a side hot press block according to an embodiment of the present application.

Reference mark:

10-anode pole piece;

12-cathode pole piece;

14-isolation film;

20-power mechanism;

22-hot pressing mechanism;

220-top hot pressing block;

222- bottom hot pressing block;

222a-fixed hole;

224-side hot pressing block;

226-active hot pressing block;

226a-bar-shaped hole;

24-fixed mechanism;

240-first fixed plate;

242-second fixed plate;

244-connecting column;

246-third fixed plate;

26-guide mechanism;

260-guide plate;

262-bearings.

The drawings herein are incorporated in and constitute a part of the specification,

detailed description

The present application will be further described in detail below through specific embodiments and with reference to the accompanying drawings. The terms "front", "back", "left", "right", "upper" and "lower" as used herein are referenced to the state of the cells in the drawing and the state of the cell hot pressing device.

As shown in FIG. 2, the embodiment of the present application provides a battery core, which is formed by alternately winding an anode pole piece 10, a cathode pole piece 12, and a separator film 14, which is different from the battery core in the related art. The cross section of the cell in the example is a rounded square structure in which the four corners are rounded.

Referring to FIG. 1, in the related art, since the cells are not limited on both sides during the forming process, a large R angle is formed, which causes waste of the internal volume of the lithium ion battery, thereby reducing the volume energy of the battery. density. Specifically, it is assumed that the main body width (the spacing between the R angles on both sides) of the cell is W1, the thickness of the cell is T, and the diameter of the R angle is equal to the thickness T of the cell, and the total area occupied by the cross section of the cell M1=T(W1+T)=TW1+T ² .

However, the cross section of the cell in this embodiment is rounded to a square structure, so that there is only a small rounded corner r at the four apex angles, see FIG. 3, assuming the body width of the cell (between the r angles on both sides) The pitch is W2, the thickness of the cell is still T, and the total area occupied by the cross section of the cell M2=T(W2+2r)=TW2+2rT.

Since the width of the cell is limited during the hot pressing in this embodiment, W2 < W1, and since the cell at this time has rounded corners only at the ends of the side, the radius r of the rounded corner cannot reach T/. 2, therefore 2r < T, therefore, M2 < M1, that is to say, in the case where the thickness T of the cell and the actual cross-sectional area are the same, the total area of the cross section of the cell formed in this embodiment is smaller than that in the related art. The solution therefore takes up less volume and has a higher volumetric energy density.

In the related art, since there are no constraints on both sides of the battery cell, the magnitude of the R angle is not well grasped at the time of hot pressing, and the pole piece may be broken. In order to prevent the pole piece from being broken, the anode pole piece 10, the cathode pole piece 12, and the separator 14 in the present embodiment are preferably kept uniform in thickness, and the partial thickness is not reduced even at the rounded corners, so that the strength of the round corners can be improved. Thereby avoiding breakage of the pole pieces. The radius r values of the four apex angles are preferably equal to increase the regularity of the cell and the energy density. Moreover, this embodiment can also avoid the breakage of the pole piece by adjusting the radius r of the apex angle. In general, the radius r of the apex angle cannot be smaller than the sum of the thicknesses of the single layer of the anode pole piece, the cathode pole piece and the separator film, and the radius r of the apex angle is also less than T/2. .

In order to form the battery cell in the above embodiment, the embodiment provides a form of forming a battery cell. The law includes the following steps:

a. The piezoelectric core is placed such that the piezoelectric core is located between the top plane, the bottom plane and the two side planes, wherein one side of the piezoelectric core perpendicular to the thickness direction is in contact with the bottom plane, and the piezoelectric core is to be There is a certain distance from each side plane.

The purpose of this step is to place the cell waiting for hot pressing in a hot press space consisting of a top plane, a bottom plane, and two side planes, ready for hot pressing. Considering the problem of the equalization of the pressing force on both sides of the cell during the hot pressing, it is preferable to set the side planes on both sides to be the same distance from the center of the piezoelectric core.

At this time, the bottom plane and the side planes on both sides can be together to form a placement area, and the piezoelectric core is placed in a placement area formed by the bottom plane and the side planes on both sides. In this placement area, the spacing between the two side planes can be fixed or not adjustable, or it can be adjusted. That is, step d is performed before the piezoelectric core is placed, and the spacing between the two side planes is adjusted, and then step a is performed.

After step a is completed, the next step begins:

b. The piezoelectric core is hot pressed by hot pressing, so that a top plane and a bottom plane and two side planes are co-extruded to the piezoelectric core until a rounded square having a cross section of four corners is formed. Structure of the battery.

During the extrusion process, the top plane and the bottom plane and the two side planes can be moved together in the middle to squeeze the battery in all directions. However, considering the mode of handling and coordination is poor, it is not recommended. It is generally preferred to use the side plane to be fixed and to compress the thickness of the piezoelectric core after being pressed in the thickness direction, and the both sides are convex and contact with the side plane and pressed. In this way, only the top plane or the bottom plane can be manipulated to achieve full-scale compression of the piezoelectric core, and the handling is stronger, and since the two side planes are fixed, the force applied to the piezoelectric core is passive. Force is also easier to control accurately. The best way is to fix the bottom plane and the side planes, move the top plane down and squeeze the piezoelectric core. During the hot pressing process, since the upper and lower sides of the cell are all squeezed, the cell is filled into the four corners, and the volumetric energy density is also increased while forming the rounded corners.

In this process, the load of the pole piece can also be adjusted by controlling various parameters of the hot pressing process to control the quality of the battery core. In this embodiment, the hot pressing moving speed can be maintained in the range of 10 to 2000 mm/min, the hot pressing temperature is maintained at 70 to 90 ° C, and the hot pressing pressure is 3 to 5 t. The hot pressing time is about 150s. Generally, the slower the speed, the better the battery core rate and its consistency, but the production efficiency is lower; the faster the speed, the higher the efficiency, and the better the yield of the extruded product. By adjusting various parameters, it is also possible to adapt to the cell requirements of different r values. For example, when the cell T to be pressed is small (the cell is very thin), the required r angle is small, and the hot pressing temperature and the hot pressing pressure can also be relatively small.

Then take the final step:

c. Complete the hot pressing to shape the battery.

After shaping, the battery can be removed and a new cycle can be restarted.

In order to achieve the above forming method, the embodiment further provides a cell hot pressing device, as shown in FIG. 4, the main components thereof include a power mechanism 20 and a hot pressing mechanism 22, and may further include a fixing mechanism 24 in addition thereto. And a guiding mechanism 26.

The hot pressing mechanism 22 includes a top plane, a bottom plane and two side planes, and the top plane, the bottom plane and the two side planes together form a hot pressing space for the thermal piezoelectric core, and these planes can be set in several On top of the mutually independent components, for example, in the present embodiment, the hot press mechanism 22 includes a top hot press block 220, a bottom hot press block 222, and two side hot press blocks 224, the top plane being located on the top hot press block 220. The bottom plane is located on the bottom hot stamping block 222, and the two side planes are respectively located on the two side hot stamping blocks 224. The power mechanism 20 is connected to the hot pressing mechanism 22, and drives the hot pressing mechanism 22 to move, reducing the hot pressing space, thereby pressing the piezoelectric core in all directions to increase the volumetric energy density of the battery core.

During the hot pressing process, the top hot press block 220 is preferably driven by the power mechanism 20, while the bottom hot press block 222 and the two side hot press blocks 224 remain relatively fixed.

Since the thickness and width of the different cell types are different, in order to enable the cell thermocompression device to adapt to more types of cell hot pressing processes, one of the two side thermocompression blocks 224 may be connected. All are designed as movable active heat blocks 226. Considering the simplified structure and operation, only one of them can be used as the movable hot press block 226, and the other one can be fixedly coupled to the bottom hot press block 222. The movable hot block 226 is movably coupled to the bottom hot block 222 and can change the spacing between the two side hot press blocks to accommodate cells of different widths.

As shown in FIG. 5, a strip hole 226a may be disposed on the movable hot press block 226. The strip hole 226a extends in the same direction as the pitch direction of the two side heat press blocks 224, and the bottom hot press block 222 is disposed on the bottom. The fixing hole 222a is inserted through the strip hole 226a through a bolt (not shown) and is coupled with the fixing hole 222a to connect the movable hot pressing block 226 with the bottom hot pressing block 222.

The fixing mechanism 24 is used to fix the power mechanism 20 and the hot pressing mechanism 22. In the hot pressing mode in which the top hot pressing block 220 is pressed, the power mechanism 20, such as the cylinder, is fixed to the fixing mechanism 24, and the bottom hot pressing block 222 is fixed on the fixing mechanism 24, and the other two side hot pressing blocks are fixed. 224 are all fixed by the bottom hot pressing block 222. Of course, it is also possible to directly fix the side hot pressing blocks 224 directly to the fixing mechanism 24.

As shown in FIG. 4, the fixing mechanism 24 in this embodiment includes a first fixing plate 240, a second fixing plate 242, and a connecting post 244, and may further include a third fixing plate 246. The first fixing plate 240 is disposed in parallel with the second fixing plate 242, and the third fixing plate 246 is disposed on a side of the second fixing plate 242 facing away from the first fixing plate 240, and is also disposed in parallel with the second fixing plate. Both are fixedly connected by a connecting post 244. The first fixing plate 240 and the second fixing plate 242 are mainly used for fixing the power mechanism 20 and the hot pressing mechanism 22, and the third positioning plate can improve the stability of the fixing mechanism 24 itself, and the connecting column 244 can be simultaneously set. Multiple roots to secure the connection from multiple directions. The power mechanism 20 and the hot pressing mechanism 22 are both located between the first fixing plate 240 and the second fixing plate 242, wherein the power mechanism 20 is fixed on the lower surface of the first fixing plate 240, and the bottom hot pressing block 222 is disposed in the first Two fixed plates 242.

In order to make the movement process of the top hot press block 220 smoother and prevent radial displacement due to other forces, the guide mechanism 26 is also provided in this embodiment. The guide mechanism 26 includes a guide plate 260 and may also include a bearing 262. The guiding plate 260 is disposed in parallel with the first fixing plate 240 and the second fixing plate 242. The guiding plate 260 is provided with a guiding hole 260a. The connecting post 244 passes through the guiding hole (not shown), the power mechanism 20 and the guiding plate. The upper surface of the 260 is connected, and the top hot stamping block 220 is fixed to the lower surface of the guide plate 260. The power mechanism 20 first drives the guide plate 260 to move, and the guide plate 260 moves the top hot press block 220 to move during the movement. At the same time, since the connecting post 244 passes through the guiding hole on the guiding plate 260, the guiding plate 260 can only move along the axial direction of the connecting post 244, thereby guiding. The bearing 262 is fixed in the guide hole and sleeved on the periphery of the connecting post 244, and can function to reduce friction.

The battery core hot pressing device provided by the embodiment of the present invention can be hot pressed to form a battery core having a rounded square structure in cross section, thereby more fully utilizing the space on both sides of the battery core and improving the volumetric energy density of the lithium ion battery. In addition, it has the characteristics of convenient operation and wide application range.

The above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and various changes and modifications may be made to the present application. Where is the essence of this application Any modifications, equivalent substitutions, improvements, etc. made within the principles of God and Principles shall be covered by this application.

Claims (11)

A battery core is formed by alternately winding an anode pole piece, a cathode pole piece and a separator film, wherein the cross section of the battery core is a rounded square structure in which all four corners are rounded. The battery cell according to claim 1, wherein said anode pole piece, said cathode pole piece, and said separator are each of uniform thickness. The battery cell according to claim 1 or 2, wherein a radius of the apex angle is not less than a sum of thicknesses of the single layer of the anode pole piece, the cathode pole piece, and the separator. The thickness of the cell is T, and the radius of the apex angle is less than T/2. The battery cell according to claim 3, wherein the four apex angles r of the cells are equal. A method of forming a battery cell according to any one of claims 1 to 4, comprising the steps of: a. placing the piezoelectric core to be placed between the top plane, the bottom plane, and the two side planes, wherein the side of the piezoelectric core perpendicular to the thickness direction is in contact with the bottom plane. The piezoelectric core is spaced apart from each of the side planes; b. hot pressing the piezoelectric core to be pressed, so that a top plane and the bottom plane and the two side planes co-extrude the piezoelectric core until the cross section is four vertex angles Rounded square structure with rounded corners; c. Forming, forming the battery core. The method of forming a battery cell according to claim 5, wherein in the step a, the bottom plane and the side planes on both sides together form a placement area, and the piezoelectric core is placed In the placement area formed by the bottom plane and the side planes on both sides. The method of forming a battery cell according to claim 6, wherein in the step a, the side planes of the two sides are the same distance from the center of the piezoelectric core to be piezoelectric. The method of forming a battery cell according to claim 6, wherein in the step b, the side plane is fixed, and the piezoelectric core is subjected to thickness compression in the thickness direction, and both sides are compressed. Protruding and contacting the side plane and pressing. A method of forming a battery cell according to claim 8, wherein said step b The bottom plane and the side plane are both fixed, the top plane moves downward and squeezes the piezoelectric core to be pressed, and the piezoelectric core is compressed after being pressed, and the two sides are convex. And contacting the side plane and pressing. The method for forming a battery cell according to any one of claims 5 to 9, wherein in the step b, the hot pressing moving speed is 10 to 2000 mm/min, the hot pressing temperature is 70 to 90 ° C, and the hot pressing pressure is It is 3 to 5 tons and the hot pressing time is 150 seconds. The method of forming a battery cell according to any one of claims 5 to 9, wherein the step a further comprises the following steps: d. Adjust the spacing between the two side planes.

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