Title of invention: Battery cell pressurization device
technical field
[One]
Cross-Citation with Related Application(s)
[2]
This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0140360 on November 5, 2019, and all contents disclosed in the literature of the Korean patent application are incorporated as a part of this specification.
[3]
The present invention relates to a battery cell pressurizing device, and more particularly, to a battery cell pressurizing device using a shape memory material.
background
[4]
Secondary batteries that are easy to apply according to product groups and have electrical characteristics such as high energy density are universally applied to electric vehicles or hybrid vehicles driven by an electric drive source, as well as portable devices, and power storage devices. These secondary batteries are attracting attention as a new energy source for improving eco-friendliness and energy efficiency in that not only the primary advantage of being able to dramatically reduce the use of fossil fuels but also the fact that no by-products are generated from the use of energy.
[5]
Conventionally, nickel cadmium batteries or hydrogen ion batteries have been used as secondary batteries, but recently, compared to nickel-based secondary batteries, the memory effect hardly occurs, so charging and discharging are free, and lithium secondary batteries with a very low self-discharge rate and high energy density have been developed. It is used a lot.
[6]
Such a lithium secondary battery mainly uses a lithium-based oxide and a carbon material as a positive electrode active material and a negative electrode active material, respectively. A lithium secondary battery includes a secondary battery cell in which a positive electrode plate and a negative electrode plate to which the positive electrode active material and the negative electrode active material are respectively applied with a separator interposed therebetween, and an exterior material for sealingly housing the secondary battery cell together with an electrolyte, that is, a battery case.
[7]
A lithium secondary battery consists of a positive electrode, a negative electrode, a separator and an electrolyte interposed therebetween, and is divided into a lithium ion battery, a lithium polymer battery, etc. depending on which positive active material and negative active material are used. In general, the electrodes of these lithium secondary batteries are formed by coating a positive electrode or negative electrode active material on a current collector such as an aluminum or copper sheet, mesh, film, foil, or the like, and then drying it.
[8]
On the other hand, in the secondary battery, the positive electrode plate, the negative electrode plate, and the separator need to be uniformly adhered as a whole so that the reaction can occur evenly in all parts of the secondary battery. Accordingly, there is a demand for development of a device for pressurizing the secondary battery cells in a balanced manner.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[9]
An object of the present invention is to provide a battery cell pressurizing device that implements a constant pressure.
[10]
However, the problems to be solved by the embodiments of the present invention are not limited to the above problems and may be variously expanded within the scope of the technical idea included in the present invention.
means of solving the problem
[11]
The battery cell pressurization device according to an embodiment of the present invention includes a first press plate and a second press plate for pressurizing the battery cells, forming a space therebetween so that the battery cells are disposed, the first press plate and at least one pressing member of the second pressing plate is formed of a shape memory material.
[12]
After the pressing member stores a shape suitable for the battery cell at a temperature at which the battery cell is driven, the deformation of the pressing member due to volume expansion after the battery cell is driven acts as a force to return to the original shape. The battery cell can be pressurized.
[13]
A gap between the first pressure plate and the second pressure plate may increase due to volume expansion of the battery cell.
[14]
The upper surface of the first pressure plate and the lower surface of the second pressure plate may be pressed by the thickness direction expansion of the battery cell, so that the shapes of the first pressure plate and the second pressure plate may change.
[15]
When the volume of the battery cell is reduced, a gap between the first pressure plate and the second pressure plate may decrease.
[16]
The shape memory material may include a shape memory polymer.
[17]
In the battery cell, a positive electrode, a negative electrode, and an electrode assembly having a separator structure interposed between the positive electrode and the negative electrode may be sealed in the battery case together with an electrolyte.
[18]
The first pressure plate is in contact with the lower surface of the battery case, the second pressure plate is in contact with the upper surface of the battery case, and the side of the battery case positioned between the first pressure plate and the second pressure plate is can be exposed to the outside.
[19]
The first pressure plate and the second pressure plate may be coupled by a coupling pin.
[20]
The coupling pin is formed in plurality, and may be formed of a spring.
[21]
The coupling pins may be formed in plurality, and may be formed of a shape memory material.
[22]
The bonding pin may be formed of a shape memory polymer.
[23]
A distance between the first pressure plate and the second pressure plate may be equal to or greater than the thickness of the battery cell.
[24]
The battery cell may be a lithium metal cell.
[25]
The first pressure plate and the second pressure plate may have a larger area than the battery cell.
Effects of the Invention
[26]
According to embodiments, by using a battery cell pressurizing device using a shape memory material for a lithium metal cell, it is possible to generate a restoring force according to a change in the volume of the battery cell, thereby implementing a positive pressure jig effect. Therefore, it is possible to provide a large force required for a lithium metal cell by an excellent shape restoring force with a light weight.
Brief description of the drawing
[27]
1 is a side view illustrating a secondary battery cell arrangement in a battery cell pressurizing device according to an embodiment of the present invention.
[28]
FIG. 2 is a front view of the battery cell pressurizing device of FIG. 1 .
[29]
3 is a perspective view illustrating a structure of a lithium secondary battery.
[30]
4 is a graph regarding the elastic modulus according to temperature.
Modes for carrying out the invention
[31]
Hereinafter, with reference to the accompanying drawings, various embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. The present invention may be embodied in several different forms and is not limited to the embodiments described herein.
[32]
In order to clearly explain the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar elements throughout the specification.
[33]
In addition, since the size and thickness of each component shown in the drawings are arbitrarily indicated for convenience of description, the present invention is not necessarily limited to the illustrated bar. In order to clearly express various layers and regions in the drawings, the thicknesses are enlarged. And in the drawings, for convenience of description, the thickness of some layers and regions are exaggerated.
[34]
Further, when a part of a layer, film, region, plate, etc. is said to be “on” or “on” another part, it includes not only cases where it is “directly on” another part, but also cases where another part is in between. . Conversely, when we say that a part is "just above" another part, we mean that there is no other part in the middle. In addition, to be "on" or "on" the reference part means to be located above or below the reference part, and to necessarily mean to be located "on" or "on" in the direction opposite to the gravitational force no.
[35]
In addition, throughout the specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.
[36]
In addition, throughout the specification, when referring to "planar", it means when the target part is viewed from above, and "in cross-section" means when viewed from the side when a cross-section of the target part is vertically cut.
[37]
1 is a side view illustrating a secondary battery cell arrangement in a battery cell pressurizing device according to an embodiment of the present invention. FIG. 2 is a front view of the battery cell pressurizing device of FIG. 1 . 3 is a perspective view illustrating a structure of a lithium secondary battery. 4 is a graph regarding the elastic modulus according to temperature.
[38]
1 and 2 , the battery cell pressing device 500 according to the present embodiment includes a pair of pressing plates 100a and 100b coupled by a plurality of coupling pins 120 , and a pair of pressing plates. It includes a battery cell (1) positioned between (100a, 100b). The coupling pin 120 according to the present embodiment may be formed of a spring.
[39]
The plurality of coupling pins 120 may be disposed at four corners on the plane of the pressing plates 100a and 100b. Due to the coupling shape of the coupling pin 120 , the first pressure plate 100a and the second pressure plate 100b may be disposed to be spaced apart from each other. A space in which the battery cell 1 can be disposed is formed between the spaced apart first and second pressure plates 100a and 100b. The inner width of the space in which the battery cell 1 is disposed, that is, the interval between the pressure plates 100a and 100b, may be the same as the thickness of the battery cell 1 or may be slightly larger than the thickness of the battery cell 1 .
[40]
The electrode leads 31 and 32 protrude in one direction of the battery cell 1 according to the present embodiment, and the electrode leads 31 and 32 are two coupling pins positioned on one side of the pressing plates 100a and 100b. It may protrude between 120 .
[41]
At least one of the pressing plates 100a and 100b according to the present embodiment is a pressing member formed of a shape memory material. A shape memory material refers to a material with a shape memory effect that memorizes a shape memorized at a certain temperature, deforms it to a completely different shape by applying force, and then returns to its original shape when heated.
[42]
The pressing member formed of the shape memory material according to the present embodiment stores a shape suitable for the battery cell 1 at the temperature at which the battery cell 1 is driven, and then, after the battery cell 1 is driven, The deformation of the pressing member may act as a force to return to the original shape, thereby pressing the battery cell 1 . In other words, when the battery cell 1 swells, the battery cell 1 pushes the pressing member formed of the shape memory material. by pressing the battery cell (1). Specifically, when the battery cell 1 shown in FIGS. 1 and 2 expands in the thickness direction, the upper surface of the first pressure plate 100a and the lower surface of the second pressure plate 100b are pressed, and thus Accordingly, the shapes of the first and second pressure plates 100a and 100b are changed. That is, the gap between the first pressure plate 100a and the second pressure plate 100b increases due to the volume expansion of the battery cell 1 . After that, when heat is applied to the battery cell pressurizing device 500 , restoring force to return to the original shape occurs in the first and second pressurizing plates 100a and 100b , and this restoring force is applied to the battery cell 1 , so that the battery cell The volume expansion of (1) can be suppressed. When the expanded volume of the battery cell 1 is reduced by discharging, the gap between the first pressure plate 100a and the second pressure plate 100b may be reduced.
[43]
In particular, in a lithium metal battery, a dendrite phenomenon that induces an explosion or shortens the lifespan may occur. The dendrite phenomenon refers to a branch-shaped crystal that occurs on the surface of lithium metal. In other words, the battery cell pressurization device according to the present embodiment may be applied to implement a necessary pressurization when a lithium dendrite phenomenon occurs in a lithium metal battery.
[44]
The battery cell 1 to which the battery cell pressurization device according to this embodiment is applied corresponds to a lithium metal cell, and the lithium metal cell has a large volume expansion during charging and discharging, and when pressurized, the charge/discharge cycle (cycle) ), the lifespan performance is superior. Therefore, in the case of a lithium metal cell, a pressurization device is absolutely necessary.
[45]
When driving a lithium metal cell, a large pressure of up to 4 MPa is required, and a thick and heavy battery cell pressurization device made of a metal material with great rigidity can be used. It can be disadvantageous in terms of large energy density, which is the biggest advantage of Therefore, when the pressing member formed of the shape memory material according to the present embodiment is used, a small and light pressing device can be implemented while applying a large force. Lifespan performance may be improved when a spring jig capable of realizing a constant pressure is used compared to when a stereotaxic jig having a fixed thickness is used among the battery cell pressurization devices. According to the present embodiment, a positive pressure jig such as a spring jig may be implemented by using a pressing member formed of a shape memory material.
[46]
The shape memory effect is exhibited by the pressing member of the shape memory material according to the present embodiment, and a restoring force is generated according to a change in the volume of the battery cell 1 , which appears as a static pressure jig effect.
[47]
As shown in FIG. 3 , the battery cell according to this embodiment includes an electrode assembly 20 including a positive electrode, a negative electrode, and a separator interposed therebetween in the battery case 10 . The electrode tabs 21 and 22 protruding from the positive and negative electrodes of the electrode assembly 20 are electrically connected to the electrode leads 31 and 32 of the positive and negative electrodes, respectively, and may be installed to be exposed to the outside of the battery case 10 . have.
[48]
According to this embodiment, the first pressure plate 100a is in contact with the lower surface of the battery case 10 , the second pressure plate 100b is in contact with the upper surface of the battery case 10 , and the first pressure plate 100a is in contact with the upper surface of the battery case 10 . ) and the side of the battery case 10 positioned between the second pressure plate 100b may be exposed to the outside. At this time, it is preferable that the side of the battery case 10 has four surfaces, and all of the four surfaces are exposed to the outside. For the reason of having such a structure, a case in which a shape memory alloy is formed in the battery case itself surrounding the battery cell will be described as a comparative example.
[49]
Unlike a cell included in a lithium ion battery, the lithium metal cell to which an embodiment of the present invention is applied not only has a very large volume change during one charge and discharge, and the cycle is repeated because of continuous lithium dendrite formation. thickness continues to increase. If the plate for pressurization is fixed up to the side of the battery case 10, if the pressurizing device is configured to have a thickness corresponding to SOC100 of the battery cell, the thickness difference is very large in the SOC0 state, so that no pressure is applied. In addition, when the end of life (EOL) is reached through repeated charging and discharging, the thickness of the battery cell may increase significantly than the initial SOC100, and thus a greater pressure than the initial may be applied. Therefore, in the comparative example in which the shape memory alloy is used as the battery case itself, the side surfaces are all fixed, and it is difficult to apply a constant pressure to the battery cell. In addition, when the battery cell is pressurized using the battery case corresponding to the comparative example, it is difficult to evenly transmit force to the electrode area. This is because, in the case of a battery case such as a can type, when the volume expands, the surface of the expanding battery case is curved in a curve, making it difficult to evenly pressurize the electrode.
[50]
The shape memory material according to the present embodiment may be a shape memory polymer. Compared to shape memory alloys, shape memory polymers are capable of high elastic deformation, and have advantages of low cost, low density, excellent shape resilience and high tensile strength.
[51]
According to the present embodiment, since the shape memory polymer is used for the pressure plate included in the pressure device, it is possible to provide a large force of about 400% or more of the restoring force required when applied to a lithium metal cell.
[52]
In addition, referring to FIG. 4 , which is a graph of elastic modulus according to temperature, steel refers to ferrous metal, SMA refers to shape memory alloy, and SMP refers to shape memory polymer. As for the modulus of elasticity, SMP is lower than SMA in the temperature range specified in the graph. This indicates that SMP can stretch better than SMA. As the battery cell 1 shown in FIGS. 1 and 2 expands to increase the thickness of the battery cell 1 , the gap between the pressing plates 100a and 100b of the battery cell pressing device 500 increases to increase the battery cell 1 ) must be constant. At this time, since the SMP is stretched well compared to the SMA, the pressure applied to the battery cell 1 is smaller than that of the SMA. Therefore, compared to SMA, SMP is more suitable as a positive pressure jig type for lithium metal batteries. The source of the graph of Fig. 4 is Tobushi, Hisaaki, Shunichi Hayashi, and Yoshiki Sugimoto. "Two-way bending properties of shape memory composite with SMA and SMP." Materials 2.3 (2009): 1180-1192.
[53]
In a state in which the battery cell 1 is disposed inside the battery cell pressurization device and the first and second pressure plates 100a and 100b are coupled to each other by the coupling pin 120 , the activation and aging process is performed on the battery cell 1 . When the battery cell 1 expands, the thickness increases. Herein, although the activation and aging process before product shipment has been mentioned, the present invention is not limited to these process steps, and the battery cell pressurization apparatus according to an embodiment of the present invention is also applicable to the battery cell driving step.
[54]
The pair of pressure plates 100a and 100b are made of a shape memory material, and are coupled to each other by the coupling pins 120 , so that they are lightweight and convenient to handle. In the battery cell pressurizing device according to an embodiment of the present invention having the above configuration, the pressurizing plates 100a and 100b are made of a shape memory material, so that the weight can be reduced, and since the weight is light, energy density per weight like a drone It is also suitable for use in batteries where
[55]
In the above-described embodiment, it has been described that the coupling pin 120 is formed of a spring, but as a modified embodiment, the coupling pin 120 may be formed of a shape memory material. In this regard, when the distance between the first pressure plate 100a and the second pressure plate 100b increases due to volume expansion of the battery cell 1 , the length of the coupling pin 120 may also increase. Since the coupling pin 120 itself is formed of a shape memory material, a restoring force is generated, and volume expansion of the battery cell 1 can be further suppressed by this restoring force. The coupling pin 120 may also be formed of a shape memory polymer.
[56]
Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the
[57]
Explanation of symbols
[58]
1: battery cell
[59]
10: battery case
[60]
20: electrode assembly
[61]
100a, 100b: pressure plate
Claims
[Claim 1]
A space is formed therebetween so that the battery cells are disposed, and a first pressure plate and a second pressure plate are provided for pressing the battery cells, wherein at least one pressing member of the first pressure plate and the second pressure plate comprises: A battery cell pressurizing device formed of a shape memory material.
[Claim 2]
The force of claim 1 , wherein the pressing member stores a shape suitable for the battery cell at a temperature at which the battery cell is driven, and then the deformation of the pressing member due to volume expansion after driving the battery cell returns to its original shape A battery cell pressurizing device to act as a pressurizing the battery cell.
[Claim 3]
The battery cell pressurizing device of claim 2, wherein a gap between the first pressurizing plate and the second pressurizing plate increases due to volume expansion of the battery cells.
[Claim 4]
The method of claim 3, wherein the upper surface of the first pressure plate and the lower surface of the second pressure plate are pressed by the thickness direction expansion of the battery cell, so that the shapes of the first pressure plate and the second pressure plate are changed. battery cell pressurization device.
[Claim 5]
The battery cell pressurizing device of claim 3 , wherein when the volume of the battery cell is reduced, a gap between the first pressurizing plate and the second pressurizing plate is reduced.
[Claim 6]
The battery cell pressurization device of claim 5 , wherein the shape-memory material includes a shape-memory polymer.
[Claim 7]
The battery cell pressurizing device of claim 1, wherein the battery cell includes a positive electrode, a negative electrode, and an electrode assembly having a separator structure interposed between the positive electrode and the negative electrode, together with an electrolyte, sealed inside the battery case.
[Claim 8]
The method of claim 7, wherein the first pressure plate is in contact with the lower surface of the battery case, the second pressure plate is in contact with the upper surface of the battery case, located between the first pressure plate and the second pressure plate A battery cell pressurizing device in which the side of the battery case is exposed to the outside.
[Claim 9]
The battery cell pressing device of claim 1, wherein the first pressing plate and the second pressing plate are coupled by a coupling pin.
[Claim 10]
The battery cell pressing device of claim 9, wherein the coupling pins are formed in plurality and are formed of a spring.
[Claim 11]
The battery cell pressing device of claim 9 , wherein a plurality of coupling pins are formed and formed of a shape memory material.
[Claim 12]
The battery cell pressing device of claim 11 , wherein the coupling pin is formed of a shape memory polymer.
[Claim 13]
The battery cell pressing device of claim 1, wherein a gap between the first pressing plate and the second pressing plate is equal to or greater than a thickness of the battery cell.
[Claim 14]
The battery cell pressurization device of claim 1, wherein the battery cell is a lithium metal cell.
[Claim 15]
The battery cell pressing device of claim 1 , wherein the first pressing plate and the second pressing plate have a larger area than the battery cell.