This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0132219 on October 23, 2019, and all contents disclosed in the literature of the Korean patent application are incorporated as a part of this specification.
[2]
The present invention relates to a battery case for a lithium secondary battery, and to a pouch-type battery case for suppressing deformation of an electrode assembly during an activation process.
background
[3]
As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. is being used
[4]
Lithium secondary batteries are largely classified into cylindrical batteries, prismatic batteries, pouch-type batteries, etc. according to their appearance, and are also classified into lithium ion batteries, lithium ion polymer batteries, lithium polymer batteries, etc. according to the type of electrolyte.
[5]
Due to the recent trend toward miniaturization of mobile devices, the demand for thin prismatic batteries and pouch-type batteries is increasing. This is a high situation.
[6]
In general, a pouch-type battery refers to a battery in which an electrode assembly and an electrolyte are sealed inside a pouch-type case of a laminate sheet including a resin layer and a metal layer. The electrode assembly accommodated in the battery case has a structure of a jelly-roll type (winding type), a stack type (stacking type), or a complex type (stacking/folding type). A pouch-type secondary battery forms a receiving part for mounting an electrode assembly in a laminate sheet, and heat-seals a separate sheet separated from the sheet or a sheet extending therefrom in a state where the electrode assembly is mounted in the receiving part manufactured by doing
[7]
1 shows a cross-sectional view of a laminate sheet of a pouch-type secondary battery. Referring to this, the laminate sheet 20 has a structure in which an outer layer 21, a barrier layer 22, and an inner layer 23 are sequentially stacked. The outer layer 21 functions to protect the battery from the outside, and the barrier layer 22 has a function of preventing the inflow or leakage of foreign substances such as gas and moisture and a function of improving the strength of the battery case. and the inner layer 23 has a function of enabling thermal fusion when sealing the battery case.
[8]
2 is a front view of a conventional battery cell in which the electrode assembly is accommodated in a pouch of a laminate sheet and the sealing process is completed, and FIG. 3 is a side view of the battery cell of FIG. Referring to these drawings, the battery case 10 is an accommodating part 11 in which the electrode assembly 1 is accommodated, a sealing part 13 formed by heat-sealing a laminate sheet, and a free space other than the accommodating part, which is generated during the activation process. and a gas pocket portion 12 capable of collecting gas. However, during the activation process, internal gas is generated as shown in FIG. 3, and since the barrier layer of the laminate sheet constituting the battery case is difficult to permeate gas, moisture, etc., and the expansion rate is small, the electrode is caused by the gas collected in the battery case. There was a problem causing expansion or deformation of the assembly. Although the degassing process of discharging the internal gas by puncturing the gas pocket after the activation process is performed, the internal gas generated before performing the deaeration process causes the above problems in the battery case.
[9]
In addition, in order to transport the battery cells during the activation process, the battery cells must be picked up using a transfer member such as tongs. There were difficulties in the process of picking up.
[10]
Accordingly, there is a need to develop a technology for a battery case that facilitates transport of the battery cell for a subsequent process while suppressing deformation of the electrode assembly caused by the gas generated during the activation process.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[11]
An object of the present invention is to provide a battery case capable of suppressing a phenomenon in which gas generated during an activation process deforms an electrode assembly prior to a degassing process.
[12]
In addition, an object of the present invention is to provide a battery cell in a form that is easily picked up by a transfer member by allowing the gas generated during the activation process to be easily discharged or the gas pocket is expanded.
means of solving the problem
[13]
The battery case of the present invention for solving the above problems is a battery case for a lithium secondary battery made of a laminate sheet including an outer layer/barrier layer/inner layer structure. 1 area; and a second region that is the remaining region except for the first region, wherein the laminate sheet constituting the first region does not include a barrier layer or includes a barrier layer in which a slit is formed.
[14]
A battery case according to an embodiment of the present invention includes a receiving unit in which an electrode assembly is accommodated; and a gas pocket in which gas generated during the activation process is collected, wherein the first region is formed in the gas pocket.
[15]
In one embodiment of the present invention, the barrier layer is aluminum or an aluminum alloy.
[16]
In one embodiment of the present invention, the laminate sheet constituting the first region does not include a barrier layer. At this time, the outer layer of the laminate sheet of the first region,
[17]
One or two or more selected from the group consisting of polyamide, polyester, polyethylene, polypropylene (PP) and cyclic olefin copolymer (COC);
[18]
It may be one or more selected from the group consisting of low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), biaxially oriented polypropylene (BOPP), and cyclic olefin copolymer (COC).
[19]
In one embodiment of the present invention, the laminate sheet constituting the first region includes a barrier layer in which slits are formed. In this case, slits may not be formed in each of the inner and outer layers of the laminate sheet constituting the first region.
[20]
In one embodiment of the present invention, the first region is formed between the boundary where one end of the gas pocket part meets the accommodating part to the other end of the gas pocket part.
[21]
In one embodiment of the present invention, the inner layer is polypropylene or polyethylene.
[22]
A method of manufacturing a secondary battery according to the present invention includes the steps of accommodating an electrode assembly in the battery case and injecting an electrolyte; and performing an activation process in a state in which the battery case is sealed or gas-sealed.
[23]
In addition, the method of manufacturing a secondary battery according to the present invention may further include performing a degassing process for discharging internal gas by drilling one or more through-holes in the gas pocket after the activation process.
Effects of the Invention
[24]
In the battery case according to the present invention, a partial region of the laminate sheet constituting the gas pocket does not include a barrier layer for blocking gas and moisture, or a slit is formed only in the barrier layer, so that gas inside the battery case passes through the region is easy to be discharged, or the region of the region has relatively superior expansibility compared to other regions, so that the gas generated during the activation process moves to the region, thereby preventing deformation of the electrode assembly by the internal gas.
[25]
In addition, in the battery case according to the present invention, since the gas generated during the activation process is discharged, the degree of swelling of the gas pocket part due to the internal gas during the activation process is reduced, and it is easy to pick up the battery cell using the transfer member, so that the work efficiency in the process has the effect of improving
Brief description of the drawing
[26]
1 is a cross-sectional view of a general lamination sheet constituting a case of a pouch-type secondary battery.
[27]
2 is a front view of a battery cell in which an electrode assembly is inserted into a conventional battery case, and electrolyte injection and sealing are completed.
[28]
3 is a side view of the battery cell of FIG. 2, showing before/after an activation process.
[29]
FIG. 4 is a view showing a mode in which the battery cell of FIG. 2 is picked up.
[30]
5 is a front view of a battery cell in which an electrode assembly is inserted into a battery case according to an embodiment of the present invention, and electrolyte injection and sealing are completed.
[31]
6 is a side view of the battery cell of FIG. 5, showing before and after the activation process.
[32]
FIG. 7 is a view showing a mode in which the battery cell of FIG. 5 is picked up.
[33]
8 is a side view of a battery cell in which an electrode assembly is inserted into a battery case according to another embodiment of the present invention, and electrolyte injection and sealing are completed, showing before and after the activation process.
[34]
9 is a side view of a battery cell in which an electrode assembly is inserted into a battery case according to another embodiment of the present invention and electrolyte injection and sealing are completed, showing before and after an activation process.
[35]
10 to 12 are views showing a battery case according to various embodiments of the present invention.
Best mode for carrying out the invention
[36]
As used throughout the specification of the present invention, terms such as "comprises" or "have" are intended to designate the existence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, one It should be understood that it does not preclude the possibility of the presence or addition of or more other features or numbers, steps, operations, components, parts, or combinations thereof.
[37]
[38]
Hereinafter, the present invention will be described in detail.
[39]
The present invention provides a battery case for a lithium secondary battery made of a laminate sheet including an outer layer/barrier layer/inner layer structure, comprising: a first region that is a region in which gas is easily discharged or is relatively well expanded; and a second region that is a region other than the first region, wherein the laminate sheet constituting the first region does not include a barrier layer or includes a barrier layer in which a slit is formed. .
[40]
The manufacturing process of a lithium secondary battery includes a process of inserting an electrode assembly into a battery case made of a laminate sheet, injecting electrolyte, and sealing the electrode assembly to perform an activation process. During the activation process, a large amount of gas is generated by chemical action and side reactions between the electrolyte and the electrode, and these gases are discharged through a separate process of the degassing process. Therefore, after the activation process is started and before the degassing process is performed, the internal gas fills the battery case, which may cause swelling or deformation of the electrode assembly. This is caused by the fact that the laminate sheet used as the battery case includes a barrier layer made of a metallic material through which air or water vapor is difficult to permeate. Accordingly, the internal gas generated during the activation process is blocked from the outside by the barrier layer and cannot be discharged, and as it gathers inside the battery case, the battery case is inflated like a balloon.
[41]
Accordingly, the present invention has been devised to have a structure in which the internal gas generated during the activation process is easily discharged or the internal gas is easily collected in the gas pocket part instead of the receiving part.
[42]
The battery case of the present invention is characterized in that the laminate sheet constituting a partial region does not include a barrier layer or includes a barrier layer in which a slit is formed, unlike the laminate sheet constituting the other regions. A typical laminate sheet has a barrier layer made of a metallic material in order to provide a function of preventing the inflow or leakage of foreign substances such as gas and moisture and a function of improving the strength of the battery case, but due to such a barrier layer, the activation process The gas generated during the process cannot be discharged and fills the inside of the battery case. In the battery case of the present invention, the first region, which is a partial region, is made of a laminate sheet for easy gas discharge or relatively good expansion. and to configure the second area, which is the remaining area except for the first area, with a conventional laminate sheet.
[43]
5 is a front view of the battery case 100 according to an embodiment of the present invention. Referring to this, the battery case 100 has a receiving part 110 in which the electrode assembly 1 of a positive electrode/separator/negative electrode structure is accommodated. ), a gas pocket portion 120 disposed on the upper portion of the housing to collect gas generated during the activation process, and a sealing portion 130 for sealing the inside of the battery case, and the gas pocket portion 120 ) includes a first region 121 that is a region in which gas is easily discharged or expands relatively well. The first region may have a predetermined width and extend in a direction parallel to the sealing part 130 of the battery case.
[44]
10 shows the shape of the first area according to still another embodiment of the present invention. Referring to FIG. 10 , the first regions 121 having a plurality of rectangular shapes on the gas pocket part 120 may be arranged in a line in a direction parallel to the sealing part 130 .
[45]
Preferably, the first region 121 is formed between the boundary at which the accommodating part 110 contacts one end of the gas pocket part 120 and the other end of the gas pocket part 120 . This is because, if a significant amount of the electrolyte is accommodated in the housing in which the electrode assembly is accommodated, and there is no barrier layer in the laminate sheet constituting the housing, the electrolyte may leak.
[46]
The area occupied by the first region may be appropriately selected according to the air permeability of the inner/outer layer material constituting the laminate sheet and the chemical properties of the electrode assembly and the electrolyte. Specifically, the area occupied by the first region may be 5% to 50% based on the area of ​​the gas pocket, but is not limited thereto.
[47]
In order to facilitate the discharge of gas from the first region or to provide relatively good expansion, the laminate sheet constituting the first region does not include a barrier layer or includes a slit barrier layer. Since the laminate sheet which does not contain a barrier layer is excellent in the permeability of gas and water|moisture content compared with the laminate sheet which contains a barrier layer, discharge|emission of gas becomes easy. Even if the laminate sheet in which the slit is formed in the barrier layer includes the barrier layer, the gas can be discharged through the slit of the barrier layer, so that the gas is easily discharged.
[48]
The laminate sheet constituting the first region will be described in detail.
[49]
A first embodiment of the laminate sheet constituting the first region does not include a barrier layer, and the materials of the outer layer and the inner layer are the same as those of a conventional laminate sheet.
[50]
In the first embodiment, since the outer layer of the laminate sheet constituting the first region must have excellent resistance from the external environment in order to protect the battery from the outside, excellent tensile strength and weather resistance compared to the thickness are required. For example, polyamide-based resin such as nylon, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyester-based resin such as polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP) ) and the like, polystyrene-based resins such as polystyrene, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, and the like may be used. These materials may be used alone or in combination of two or more.
[51]
In the first embodiment, the inner layer of the laminate sheet constituting the first region functions to heat-seal the battery case during gas sealing or sealing. Since the thermal fusion may be performed at a temperature of 100° C. to 200° C., the inner layer material is made of a material having a melting point in the temperature range. In addition, since the inner layer serves to ensure insulation, it has low hygroscopicity in order to suppress the penetration of the electrolyte, and must not be expanded or eroded by the electrolyte. Preferred examples of the inner layer material include, but are not limited to, polyethylene, polyethylene acrylic acid, unstretched polypropylene, polyamide, polyamide imide, polyimide, and mixtures or copolymers thereof.
[52]
In the first embodiment, the laminate sheet constituting the first region does not include a barrier layer, but consists only of an outer layer and an inner layer, and the material of the outer layer and the inner layer is the above polymer material, so a conventional laminate sheet and comparatively better scalability. Accordingly, the internal gas generated during the activation process naturally moves from the accommodating part, which is not expanded due to the barrier layer, to the first region with good expandability. 8 is a side view of the battery cell in which the electrode assembly 1 is inserted into the battery case according to the first embodiment of the present invention, and electrolyte injection and sealing are completed, before and after the activation process. Referring to FIG. As the barrier layer is removed, the laminate sheet constituting the first region 121 has relatively excellent expandability compared to the laminate sheet constituting the remaining regions except for the first region. Therefore, the gas generated during the activation process has a tendency to move to the first region 121, which expands well. Accordingly, most of the internal gas is collected in the first region 121 positioned on the gas pocket part 121 , and the laminate sheet of the first region expands, and only a small amount of gas is stored in the battery cell accommodating part 110 . will remain in Accordingly, the volume expansion rate of the battery cell accommodating part 110 is reduced, so that the tongs can easily pick up the battery cell in a subsequent process.
[53]
[54]
A second embodiment of the laminate sheet constituting the first region of the present invention is composed of an outer layer material that does not include a barrier layer and has better air permeability compared to a conventional outer layer material of the laminate sheet. 6 shows the side of the battery cell after the electrode assembly 1 is inserted into the battery case according to the second embodiment and the electrolyte injection and sealing are completed, before and after the activation process. Referring to FIG. 6 , the laminate sheet constituting the first region 121 is the same as the first embodiment in that it does not include a barrier layer, but an outer layer of the laminate sheet constituting the first region 121 . It differs from the first embodiment in that it is a material having a property of allowing gas to pass through but blocking moisture.
[55]
Specific examples of the outer layer material having a property of passing gas well but blocking moisture include low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), biaxially oriented polypropylene (BOPP) and cyclic olefins. One or two or more selected from the group consisting of copolymer (COC). When the outer layer of the laminate sheet constituting the first region is made of the polymer material, since the performance of blocking moisture is excellent compared to the general outer layer material, the moisture barrier performance of the first region is similar to that of the laminate sheet including the barrier layer or It can be kept at a slightly lower level.
[56]
Referring to FIG. 6 , in the laminate sheet constituting the first region 121 , the barrier layer is removed, the gas of the outer layer passes well, and the internal gas (a) generated during the activation process is well passed through the first region. is emitted Accordingly, the battery cell accommodating part 110 is not expanded by the internal gas. Accordingly, as shown in FIG. 7 , the pick-up of the battery cell is facilitated.
[57]
[58]
A third embodiment of the laminate sheet constituting the first region of the present invention includes a barrier layer with slits. At this time, it is preferable that the slit is formed only in the barrier layer, and the slit is not formed in the outer layer and the inner layer. This is because, if the slits are formed in the outer layer and the inner layer, the electrolyte may leak during the activation process and negatively affect the battery performance. 9 is a side view of a battery cell in which the electrode assembly 1 is inserted into the battery case according to the third embodiment, and electrolyte injection and sealing are completed, before and after the activation process. Referring to FIG. 9 , the laminate sheet constituting the first region 121 does not include a barrier layer, and since the outer layer is made of a material with good air permeability, the gas is easily discharged, and internal gas generated during the activation process ( a) is well drained through the first zone.
[59]
11 to 12 show various slit shapes according to the third embodiment. The slits of the barrier layer according to the third embodiment may be formed in a straight line in the gas pocket portion 120 as shown in FIG. 11 , or may be formed in a cross shape as shown in FIG. 12 .
[60]
[61]
Hereinafter, the laminate sheet constituting the second region in the battery case of the present invention will be described. In the present invention, the second region refers to a region other than the first region. The laminate sheet constituting the second region is different from the laminate sheet of the first region, and a conventional laminate sheet can be used.
[62]
A typical laminate sheet may include an outer layer/barrier layer/inner layer structure. Since the outer layer must have excellent resistance from the external environment in order to protect the battery from the outside, excellent tensile strength and weather resistance compared to its thickness are required. For example, polyamide-based resin such as nylon, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyester-based resin such as polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP) ) and the like, polystyrene-based resins such as polystyrene, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, and the like may be used. These materials may be used alone or in combination of two or more.
[63]
The barrier layer, in addition to the function of preventing the inflow or leakage of foreign substances such as gas and moisture, to exhibit a function of improving the strength of the battery case, aluminum or aluminum alloy may be used, and these may be used alone or in combination of two or more have.
[64]
The inner layer functions to heat-seal the battery case during temporary sealing or sealing. Since the thermal fusion may be performed at a temperature of 100° C. to 200° C., the inner layer material is made of a material having a melting point in the temperature range. In addition, since the inner layer serves to ensure insulation, it has low hygroscopicity in order to suppress the penetration of the electrolyte, and must not be expanded or eroded by the electrolyte. Preferred examples of the inner layer material include, but are not limited to, polyethylene, polyethylene acrylic acid, unstretched polypropylene, polyamide, polyamide imide, polyimide, and mixtures or copolymers thereof.
[65]
In general, polyolefin-based resins such as polypropylene have low adhesion to metal, and in order to improve adhesion, the surface of the barrier layer facing the inner layer is chemically and/or physically formed so that a plurality of irregularities can be formed. can be processed. Such irregularities may be formed, for example, by sand blasting or chemical etching on the surface of the barrier layer, and improvement of adhesion by securing a wider surface area can be expected. The size of the unevenness is not particularly limited, but it is preferably 10 to 100 μm in size to provide a high bonding force between the layers.
[66]
The laminate sheet may have a structure that further includes an adhesive layer between the outer layer and the barrier layer and/or between the barrier layer and the inner layer. The adhesive layer serves to supplement adhesion between the barrier layer and the outer layer and between the barrier layer and the inner layer.
[67]
As the adhesive layer, for example, an adhesive containing a resin such as an epoxy-based, phenol-based, melamine-based, polyimide-based, polyester-based, or urethane-based adhesive may be used, and (modified) polypropylene or (modified) polyethylene resin is melted. A melt-extruded resin layer formed by extrusion coating may be used.
[68]
In the laminate sheet constituting the second region, the outer layer may have a thickness of 5 to 40 µm, the barrier layer may have a thickness of 5 to 100 µm, and the inner layer may have a thickness of 10 to 50 µm. When the thicknesses are too thin, it is difficult to expect a blocking function and strength improvement. On the contrary, when the thicknesses are too thick, workability is deteriorated and an increase in the thickness of the sheet is caused, which is not preferable.
[69]
[70]
The present invention provides a method for manufacturing a secondary battery in which an activation process is performed using the battery case. A method of manufacturing a secondary battery according to the present invention includes the steps of accommodating an electrode assembly in the battery case and injecting an electrolyte; and performing an activation process in a state in which the battery case is sealed or gas-sealed.
[71]
The activation process is a concept including an aging process for sufficiently impregnating the electrolyte into a battery that has been sealed and injected with an electrolyte, and an activation process for activating the battery by charging/discharging to a predetermined SOC. . In the activation process, in order to prevent gas, etc. from being trapped between the electrode and the separator, a process of pressurizing at a constant pressure simultaneously with charging/discharging or after charging/discharging may be included.
[72]
In one specific example, the method of manufacturing a secondary battery according to the present invention may further include, after the activation process, performing a degassing process for discharging internal gas by drilling one or more through-holes in the gas pocket part. can
[73]
In the method of manufacturing a secondary battery according to the present invention, as the internal gas generated during the activation process is discharged through the first region or moves to the first region where expansion is relatively good, the electrode assembly is swelled by the internal gas. It has the effect of suppressing the phenomenon of ringing or deformation. In addition, for the subsequent process, when the battery cell is picked up with a transfer member such as tongs, since the internal gas is discharged from the battery case, there is an effect that the pickup is easier compared to the battery cell in which the battery case is expanded with the internal gas. There is also the advantage of convenience.

WE CLAIMS

[Claim 1]A battery case for a lithium secondary battery made of a laminate sheet including an outer layer/barrier layer/inner layer structure, the battery case comprising: a first region that is a region in which gas is easily discharged or is relatively well expanded; and a second area that is a remaining area except for the first area, wherein the laminate sheet constituting the first area does not include a barrier layer or includes a barrier layer in which a slit is formed.
[Claim 2]
According to claim 1, wherein the battery case, The electrode assembly is accommodated in the receiving portion; and a gas pocket in which gas generated during the activation process is collected, wherein the first region is formed in the gas pocket.
[Claim 3]
The battery case according to claim 1, wherein the barrier layer is made of aluminum or an aluminum alloy.
[Claim 4]
The battery case according to claim 1, wherein the laminate sheet constituting the first region does not include a barrier layer.
[Claim 5]
The battery case according to claim 1, wherein the laminate sheet constituting the first region includes a barrier layer having slits formed therein.
[Claim 6]
The battery case of claim 4 , wherein the first region is formed between a boundary where one end of the gas pocket part meets the accommodating part and the other end of the gas pocket part.
[Claim 7]
5. The method of claim 4, wherein the outer layer of the laminate sheet in the first region is one or more selected from the group consisting of polyamide, polyester, polyethylene, polypropylene (PP) and cyclic olefin copolymer (COC). Characterized by the battery case.
[Claim 8]
5. The method of claim 4, wherein the outer layer of the laminate sheet of the first region is low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), biaxially oriented polypropylene (BOPP) and cyclic olefin copolymer (COC). A battery case, characterized in that one or two or more selected from the group consisting of.
[Claim 9]
The battery case according to claim 1, wherein the inner layer is made of polypropylene or polyethylene.
[Claim 10]
The battery case according to claim 5, wherein no slits are formed in the inner and outer layers of the laminate sheet in the first region.
[Claim 11]
accommodating the electrode assembly in the battery case of claim 1 and injecting an electrolyte; and performing an activation process in a state in which the battery case is sealed or temporarily sealed.
[Claim 12]
The method of claim 11 , further comprising performing a degassing process for discharging internal gas by drilling one or more through-holes in the gas pocket after the activation process.