Secondary battery and device including the same

Abstract

A secondary battery according to an embodiment of the present invention includes an electrode assembly including a positive electrode, a negative electrode, and a separator, a battery case that houses the electrode assembly, and a protective member formed between the electrode assembly and the battery case, the protective member including a first protective layer, a second protective layer, and a modified member formed between the first protective layer and the second protective layer.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0110744 filed on September 1, 2022 and Korean Patent Application No. 10-2023-0114560 filed on August 30, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a secondary battery and a device including the same, and more particularly to a secondary battery with improved safety and a device including the same. [Background technology]

[0003] As technological development and demand for mobile devices increases, the demand for secondary batteries as an energy source is rapidly increasing. Therefore, much research is being conducted on secondary batteries that can meet various demands.

[0004] Secondary batteries are attracting much attention not only for use in mobile devices such as mobile phones, digital cameras, and notebook computers, but also as energy sources for power devices such as electric bicycles, electric cars, and hybrid electric cars.

[0005] Recently, attempts have been made to apply various materials in order to develop secondary batteries with good performance such as high energy density, long life, and durability. However, even in the case of secondary batteries with such improved properties, internal gas generation can be a problem in high potential and high temperature storage environments. Such gas generation can cause the internal volume of the secondary battery to increase or decrease. Such an increase or decrease in the volume of the internal components induces pressure on other components, and the generated pressure can lead to physical impact on other secondary battery components, resulting in a decrease in the function of the secondary battery or an explosion of the secondary battery. Furthermore, as the energy density and operating voltage of secondary batteries increase due to the improvement in performance of portable electronic devices, it is necessary to ensure safety against such volume changes of the internal components.

[0006] In addition, in the case of the secondary battery, self-heating occurs in a high potential and high temperature storage environment, and the accumulation of the self-heating causes thermal runaway, which may lead to an explosion of the secondary battery.

[0007] Therefore, it is necessary to ensure safety against thermal runaway caused by the volume change of the internal structure and the accumulation of the self-heating. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a secondary battery with improved safety and a device including the same.

[0009] The problems to be solved by the present invention are not limited to the problems described above, and problems not mentioned will be clearly understood by a person having ordinary skill in the art to which the present invention pertains from this specification and the accompanying drawings. [Means for solving the problem]

[0010] A secondary battery according to an embodiment of the present invention includes an electrode assembly including a positive electrode, a negative electrode, and a separator, a battery case that houses the electrode assembly, and a protective member formed between the electrode assembly and the battery case, the protective member including a first protective layer, a second protective layer, and a modified member formed between the first protective layer and the second protective layer.

[0011] When the internal temperature of the secondary battery increases, the modifying member is deformed, and the deformed modifying member can rupture the first protective layer and the second protective layer.

[0012] The modification member may be modified such that a deformed portion is formed in the modification member due to an increase in an internal temperature of the secondary battery.

[0013] The modifying member may rupture the first protective layer and the second protective layer such that the deformation portion forms a rupture portion in the first protective layer and the second protective layer.

[0014] The first protective layer may include a first material layer including a first case and a first material, and the second protective layer may include a second material layer including a second case and a second material, and the first material and the second material may be different materials.

[0015] The first layer of material may include a curing catalyst, and the second layer of material may include an adhesive.

[0016] The first and second protective layers may be ruptured, whereby the first and second substances come into contact with each other and react with each other.

[0017] A hardened layer may be formed on the inside of the battery case by reaction between the first material and the second material.

[0018] The first case and the second case may include one or more materials selected from the group consisting of low density polyethylene (LDPE), high density polyethylene (HDPE), oriented polypropylene (OPP), casting polypropylene (CPP), oriented nylon (ON), casting nylon (CN), and polyethylene terephthalate (PET).

[0019] The first material may include one or more materials selected from the group consisting of polyol, polyether polyol, and polyester polyol.

[0020] The second material may include one or more materials selected from the group consisting of toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI).

[0021] The content ratio of the first material and the second material may be from 30:70 to 70:30.

[0022] The modifying member may include a shape memory alloy layer or an electroactive polymer layer.

[0023] The secondary battery may further include a piezoelectric element coupled to the electroactive polymer layer.

[0024] A device according to another embodiment of the present invention includes the secondary battery described above. Effect of the Invention

[0025] According to the embodiment, even if the temperature of the secondary battery of the present invention rises due to self-heating, the protective layer is destroyed by the shape memory alloy before thermal runaway occurs, and the curing catalyst and adhesive come into contact and react with each other to form a hardened layer on the inside of the case, thereby minimizing the possibility of thermal runaway occurring and maintaining the secondary battery in a safe state.

[0026] The effects of the present invention are not limited to the effects described above, and effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from this specification and the accompanying drawings. [Brief description of the drawings]

[0027] [Figure 1] 1 is a cross-sectional view showing a secondary battery according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of a portion A in FIG. 1, and is a cross-sectional view showing a protective member included in a secondary battery according to an embodiment of the present invention. [Diagram 3] 3 is a cross-sectional view showing a state in which the protective member in FIG. 2 is deformed due to a temperature rise in the secondary battery. [Figure 4] FIG. 4 is an enlarged view of part B in FIG. 3. [Diagram 5] FIG. 5 is a plan view showing a partial configuration of the secondary battery according to an embodiment of the present invention described with reference to FIGS. 1 to 4. [Figure 6] FIG. 2 is an enlarged cross-sectional view of a portion A in FIG. 1, showing a protective member included in a secondary battery according to another embodiment of the present invention. [Figure 7] 7 is a cross-sectional view showing a state in which the protective member in FIG. 6 is deformed due to a temperature rise in the secondary battery. [Figure 8]8 is a plan view showing a partial configuration of the secondary battery according to an embodiment of the present invention described with reference to FIGS. 6 and 7. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention may, however, be embodied in various different forms and should not be construed as being limited to the embodiments set forth herein, but rather may be practiced in a variety of different ways.

[0029] In order to clearly describe the present invention, parts that are not relevant to the description will be omitted, and the same reference numerals will be used to refer to the same or similar components throughout the specification.

[0030] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, and the present invention is not necessarily limited to those shown. In the drawings, thicknesses are enlarged to clearly show various layers and regions. In the drawings, the thicknesses of some layers and regions are exaggerated for convenience of explanation.

[0031] In addition, throughout the specification, when a part is said to "comprise" a certain element, this does not mean to exclude other elements, but may further include other elements, unless specifically stated to the contrary.

[0032] Also, throughout the specification, the term "on a plane" means when the part in question is viewed from above, and the term "on a cross section" means when the part in question is cut vertically and viewed from the side.

[0033] Hereinafter, the secondary battery according to the present embodiment will be described in detail with reference to the drawings.

[0034] FIG. 1 is a cross-sectional view showing a secondary battery according to an embodiment of the present invention.

[0035] Referring to FIG. 1, the secondary battery 100 of this embodiment includes an electrode assembly 10 including a positive electrode 11, a negative electrode 12, and a separator 13, a battery case 50 that houses the electrode assembly 10, and a protective member 40 formed between the electrode assembly 10 and the battery case 50, and the protective member 40 includes a first protective layer 41, a second protective layer 45, and a shape memory alloy layer 43 formed between the first protective layer 41 and the second protective layer 45.

[0036] The electrode assembly 10 includes a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12. A positive electrode tab 21 is formed on one side of the positive electrode 11, and a negative electrode tab 22 is formed on one side of the negative electrode 12, and the positive electrode tab 21 and the negative electrode tab 22 may be arranged side by side with a certain gap between them. The tabs may be connected to an external circuit by being connected to a positive electrode lead 31 and a negative electrode lead 32, respectively.

[0037] The electrode assembly 10, the positive electrode tab 21, and the negative electrode tab 22 may be sealed in a pouch-shaped battery case 50. The battery case 50 may be typically made of a laminate sheet including a resin layer and a metal layer. In this case, the positive electrode lead 31 and the negative electrode lead 32 may be partially exposed to the outside for electrical connection with the outside of the electrode assembly 10 and sealed in the pouch. However, the type of the battery case 50 is not limited thereto, and may be a square or cylindrical case.

[0038] In this embodiment, the protective member 40 is formed between the electrode assembly 10 and the battery case 50. As shown in FIG. 1, the protective member 40 is formed between the electrode assembly 10 and the battery case 50, and may be formed on both the upper and lower parts of the electrode assembly 10, but is not limited thereto, and may be located corresponding to only one side of the electrode assembly 10.

[0039] Fig. 2 is an enlarged view of part A in Fig. 1, and is a cross-sectional view showing a protective member included in a secondary battery according to an embodiment of the present invention. Fig. 3 is a cross-sectional view showing a state in which the protective member in Fig. 2 is deformed due to a temperature rise in the secondary battery. Fig. 4 is an enlarged view of part B in Fig. 3. Fig. 5 is a plan view of a part of the configuration of a secondary battery according to an embodiment of the present invention, viewed from above.

[0040] 2, the protective member 40 may include a first protective layer 41, a second protective layer 45, and a shape memory alloy layer 43 formed between the first protective layer 41 and the second protective layer 45. In this case, in FIGS. 1 and 2, the first protective layer 41 is shown to be located on the battery case 50 side, and the second protective layer 45 is shown to be located on the electrode assembly 10 side, but this is not limited thereto, and the second protective layer 45 may be located on the battery case 50 side, and the first protective layer 41 may be located on the electrode assembly 10 side. In addition, the first protective layer 41 and the second protective layer 45 may be located on the lead part side such as the positive electrode lead 31 or the negative electrode lead 32 or in the part where the pouch case (battery case 50) is sealed, as long as they do not interfere with the operation of the cell.

[0041] 5, the shape memory alloy layer 43 may be formed to have a smaller area than the first protective layer 41 and the second protective layer 45. Although the first protective layer 41 is omitted in FIG. 5, it is self-evident that the first protective layer 41 is formed on the top of the shape memory alloy layer 43.

[0042] 2 and 4, the first protective layer 41 may include a first case 41a and a first material layer 41b including a first material, and the second protective layer 45 may include a second case 45a and a second material layer 45b including a second material. The first material 41b and the second material 45b may be different materials.

[0043] Therefore, in Figures 2 and 4, the shape memory alloy layer 43 is located between the first protective layer 41 and the second protective layer 45, and the first material layer 41b and the second material layer 45b are separated by the first case 41a and the second case 45a so that they do not come into contact with each other. In this case, the first material layer 41b and the second material layer 45b do not react with each other, and the secondary battery 100 operates normally.

[0044] On the other hand, in the case of secondary battery 100, self-heating may occur in a high potential and high temperature storage environment, and when the internal temperature of secondary battery 100 increases due to such self-heating of secondary battery 100, shape memory alloy layer 43 may be deformed.

[0045] 3 and 4, when the internal temperature of the secondary battery 100 rises, the shape memory alloy layer 43 is deformed at a temperature before thermal runaway occurs, and the deformed shape memory alloy layer 43 can rupture the first protective layer 41 and the second protective layer 45. As an example, since thermal runaway occurs at about 140°C to 150°C, the shape memory alloy layer 43 can operate at about 130°C or less.

[0046] At this time, the shape memory alloy layer 43 may be deformed such that a deformed portion 43 ′ is formed in the shape memory alloy layer 43 due to an increase in the internal temperature of the secondary battery 100 .

[0047] Specifically, a shape memory alloy is a material that returns to its undeformed shape when heated above a certain temperature, and through this phenomenon, a deformed portion 43' can be formed in the shape memory alloy layer 43 when the internal temperature of the secondary battery 100 rises.

[0048] Therefore, the shape memory alloy layer 43 rupturing the first protective layer 41 and the second protective layer 45 may be the deformation portion 43' rupturing the first protective layer 41 and the second protective layer 45. More specifically, the deformation portion 43' may form rupture portions 41a', 45a' in the first protective layer 41 and the second protective layer 45 to rupture the first protective layer 41 and the second protective layer 45.

[0049] In particular, the rupture parts 41a' and 45a' may be formed on the first case 41a and the second case 45a. That is, by forming the rupture parts 41a' and 45a' on the first case 41a and the second case 45a, respectively, the first material layer 41b and the second material layer 45b may be exposed to the outside of the first case 41a and the second case 45a, respectively.

[0050] Therefore, when the secondary battery 100 of this embodiment self-heats, the first protective layer 41 and the second protective layer 45 burst, allowing the first material layer 41b and the second material layer 45b to come into contact with each other and react with each other.

[0051] In this case, the first material layer 41b may include a curing catalyst, and the second material layer 45b may include an adhesive.

[0052] Therefore, a hardened layer may be formed on the inside of the battery case 50 by a reaction between the first material layer 41b and the second material layer 45b. Such a hardened layer strengthens the inner wall of the battery case 50, and not only can it delay a temperature rise due to self-heating, but it can also delay and suppress the occurrence of thermal runaway through the delay in the temperature rise.

[0053] In order to burst due to the deformation of the shape memory alloy layer 43, the first case 41a and the second case 45a may contain one or more materials selected from the group consisting of low density polyethylene (LDPE), high density polyethylene (HDPE), oriented polypropylene (OPP), casting polypropylene (CPP), oriented nylon (ON), casting nylon (CN), and polyethylene terephthalate (PET). The material is a material that can burst due to a predetermined pressure generated by the formation of the deformation portion 43' in the shape memory alloy layer 43. The thickness of the first case 41a and the second case 45a may be 10 μm to 50 μm. If the thickness is less than 10 μm, the first case 41a and the second case 45a may be destroyed even by a small impact, and a hardened layer may be formed, which is not preferable. If the thickness exceeds 50 μm, the first case 41a and the second case 45a are not destroyed despite the deformation of the shape memory alloy layer 43, and a hardened layer is not formed, which is not preferable.

[0054] Also, the first material layer 41b may include one or more materials selected from the group consisting of polyol, polyether polyol, and polyester polyol.

[0055] The second material layer 45b may include one or more materials selected from the group consisting of toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI).

[0056] Thus, a compound such as polyurethane may be formed by reaction between the first material layer 41b and the second material layer 45b to form a hardened layer.

[0057] In order to effectively induce a reaction between the first material layer 41b and the second material layer 45b upon contact, the content ratio of the first material layer 41b and the second material layer 45b may be from 30:70 to 70:30.

[0058] The first substance and the second substance may be semi-solid substances having a viscosity in the range of 10 to 90000 cP. If the viscosity is too low, the first substance or the second substance may flow out and react even if the first case 41a and the second case 45a are not destroyed, which is undesirable, whereas if the viscosity is too high, even if the first case 41a and the second case 45a are destroyed, a sufficient reaction does not occur between the first substance and the second substance, making it difficult to form a hardened layer, which is undesirable.

[0059] Under normal operating conditions, the secondary battery 100 can operate normally without forming a hardened layer because the first material layer 41b and the second material layer 45b are separated by the shape memory alloy layer 43 and the cases 41a and 45a. Also, when the internal temperature of the secondary battery 100 rises due to various causes such as abnormal conditions such as overcharging, high potential, or high temperature storage, the shape memory alloy layer 43 is deformed and the first material layer 41b and the second material layer 45b come into contact with each other and react to form a hardened layer, thereby strengthening the inner wall of the battery case 50 and delaying the thermal runaway phenomenon caused by additional temperature rise, thereby further improving the safety of the secondary battery.

[0060] Fig. 6 is an enlarged view of part A in Fig. 1, and is a cross-sectional view showing a protective member included in a secondary battery according to another embodiment of the present invention. Fig. 7 is a cross-sectional view showing a state in which the protective member in Fig. 6 is deformed due to a temperature rise in the secondary battery. Fig. 8 is a plan view seen from above of a part of the configuration of the secondary battery described in Figs. 6 and 7 according to an embodiment of the present invention.

[0061] 6, the protective member 46 according to this embodiment may include a first protective layer 41, a second protective layer 45, and a modified member formed between the first protective layer 41 and the second protective layer 45. Instead of the shape memory alloy layer 43 described in the embodiment of FIGS. 2 to 5, the modified member may include a piezoelectric element 47 and an electroactive polymer layer 48.

[0062] According to this embodiment, at least one electroactive polymer layer 48 may be electrically and / or physically connected to the piezoelectric element 47. Referring to Fig. 8, the piezoelectric element 47 may be in contact with the electroactive polymer layer 48 at a portion of both side surfaces, and may be connected to the piezoelectric element 47 through a connecting member 49. Through this connecting structure, an electrical signal generated when pressure is applied to the piezoelectric element 47 may be transmitted to the electroactive polymer layer 48 through the connecting member 49.

[0063] Specifically, the pressure increases due to an increase in the internal temperature of the secondary battery 100 and / or the generation of gas, and such pressure may be transmitted to the piezoelectric element 47. When pressure is applied to the piezoelectric element 47, the electroactive polymer layer 48 is operated by the electric current generated thereby, and as an example, as shown in FIG. 7, physical deformation of the electroactive polymer layer 48 may occur, and a deformed portion 48' may be formed in the electroactive polymer layer 48. Such a deformed portion 48' may cause the first protective layer 41 and the second protective layer 45 to rupture. The shape of the deformed portion 48' shown in FIG. 7 is an example, and the shape of the deformed portion 48' in FIG. 7 can be deformed by the contraction and expansion of the electroactive polymer layer 48 due to the movement and diffusion of ions in response to a change in external voltage.

[0064] Except for the above description of electroactive polymer layer 48, the contents described in the embodiment of FIGS. 2 to 5 are all applicable to this embodiment.

[0065] The secondary battery according to the present embodiment may be applied to various devices, specifically, to transportation means such as electric bicycles, electric cars, and hybrid vehicles, but is not limited thereto, and may be applied to various devices using secondary batteries.

[0066] Although the 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 made by those skilled in the art using the basic concept of the present invention defined in the following claims also belong to the scope of the present invention. [Explanation of symbols]

[0067] 10: Electrode assembly 21: Positive electrode tab 22: Negative electrode tab 31: Positive lead 32: Negative lead 40: Protective material 41:1st protective layer 43: Shape memory alloy layer 45:Second protective layer 47: Piezoelectric element 48: Electroactive polymer layer 50: Battery case 100: Secondary battery

Claims

1. an electrode assembly including a positive electrode, a negative electrode, and a separator; a battery case that houses the electrode assembly; a protective member formed between the electrode assembly and the battery case, The protective member is A first protective layer; A second protective layer; a modified member formed between the first protective layer and the second protective layer.

2. When the internal temperature of the secondary battery increases, the modification member is deformed, The secondary battery of claim 1 , wherein the deformed modification member ruptures the first protective layer and the second protective layer.

3. The modification of the modified member is The secondary battery according to claim 2 , wherein a deformation portion is formed in the modified member due to an increase in an internal temperature of the secondary battery.

4. The modification member causes the first protective layer and the second protective layer to rupture, The secondary battery according to claim 3 , wherein the deformation portion forms a rupture portion in the first protective layer and the second protective layer.

5. the first protective layer includes a first case and a first material layer including a first material, and the second protective layer includes a second case and a second material layer including a second material; The secondary battery according to claim 4 , wherein the first material and the second material are different materials from each other.

6. the first substance includes a curing catalyst; The secondary battery according to claim 5 , wherein the second material comprises an adhesive.

7. The secondary battery according to claim 5 , wherein the first and second protective layers are ruptured, whereby the first and second materials come into contact with each other and react with each other.

8. The secondary battery according to claim 5 , wherein a hardened layer is formed on the inside of the battery case by a reaction between the first material and the second material.

9. 6. The secondary battery of claim 5, wherein the first case and the second case include one or more materials selected from the group consisting of low density polyethylene (LDPE), high density polyethylene (HDPE), oriented polypropylene (OPP), casting polypropylene (CPP), oriented nylon (ON), casting nylon (CN), and polyethylene terephthalate (PET).

10. The secondary battery of claim 5 , wherein the first material includes at least one material selected from the group consisting of polyol, polyether polyol, and polyester polyol.

11. 6. The secondary battery of claim 5, wherein the second material comprises one or more materials selected from the group consisting of toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI).

12. The secondary battery according to claim 5 , wherein a content ratio of the first material and the second material is from 30:70 to 70:

30.

13. The secondary battery according to claim 1 , wherein the modification member comprises a shape memory alloy layer or an electroactive polymer layer.

14. The secondary battery of claim 13 , further comprising a piezoelectric element coupled to the electroactive polymer layer.

15. A device comprising the secondary battery of claim 1.

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