KR102072673B1 - Lithium Secondary Battery - Google Patents

Abstract

The present invention is an electrode assembly; A battery case accommodating the electrode assembly; A lead terminal extending from the electrode assembly and including a first lead terminal and a second lead terminal drawn out of the battery case; And a first insulating member disposed at a portion where the battery case and the first lead terminal cross each other, a first insulating member disposed at a portion where the battery case and the second lead terminal cross each other, and having a thickness different from that of the first insulating member. The present invention relates to a lithium secondary battery comprising an insulating member including an insulating member.

Description

Lithium Secondary Battery

The present invention relates to a lithium secondary battery.

As the use of portable devices such as video cameras, portable telephones and portable PCs is activated, the importance of secondary batteries mainly used as driving power thereof is increasing. Among the secondary batteries, lithium secondary batteries have higher energy density per unit weight and can be rapidly charged as compared with other secondary batteries such as lead acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries.

One of the important research tasks in lithium secondary batteries is to improve stability. Generally, lithium secondary batteries are caused by high temperature and high pressure inside the battery caused by abnormal operating conditions of the battery such as internal short circuit, charged state exceeding the allowable current or voltage, exposure to high temperature, impact from dropping, etc. Explosion can happen. In order to prevent such an explosion, the gas generated inside the lithium secondary battery should be effectively discharged. However, when the gas generated from the inside is discharged in various directions, the gas is not easily discharged to the outside and only the discharge time is long, resulting in a decrease in stability of the lithium secondary battery.

KR 2013-0064465 A

An object of the present invention is to provide a lithium secondary battery that reduces the risk of ignition and explosion by inducing and discharging the gas inside the battery generated in a high temperature and / or high pressure conditions in a specific position and a specific direction.

An object of the present invention is to provide a lithium secondary battery that can induce and discharge the gas inside the battery generated in a high temperature and / or high pressure conditions in a specific position and a specific direction without the addition of additional components and processes.

In order to solve the above problems and other problems, the present invention is an electrode assembly; A battery case accommodating the electrode assembly; A lead terminal extending from the electrode assembly and including a first lead terminal and a second lead terminal drawn out of the battery case; And a first insulating member disposed at a portion where the battery case and the first lead terminal cross each other, a first insulating member disposed at a portion where the battery case and the second lead terminal cross each other, and having a thickness different from that of the first insulating member. Provided is a lithium secondary battery comprising an insulating member including an insulating member.

The lithium secondary battery of the present invention may reduce the risk of ignition and explosion by inducing and discharging the gas generated while the electrolyte is evaporated under high temperature and / or high pressure in a specific position and in a specific direction.

The lithium secondary battery of the present invention may induce and discharge the gas generated as the electrolyte is vaporized in a specific position and in a specific direction only by controlling the thickness of the insulating member located on the lead terminal without adding a separate component and adding a process.

1 is an exploded perspective view of a lithium secondary battery according to an embodiment of the present invention.
2 is a photograph taken with a general camera after the gas ejection of the lithium secondary battery according to an embodiment of the present invention.
FIG. 3 is a photograph taken with an optical microscope of a cross section of an AB portion of a lithium secondary battery according to an exemplary embodiment of the present invention. FIG.

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concepts of terms in order to best describe their invention. It should be interpreted as meanings and concepts corresponding to the technical idea of the present invention based on the principle that the present invention.

And while the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is an exploded perspective view of a rechargeable battery according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a secondary battery according to an embodiment of the present invention includes an electrode assembly 110, a battery case 120 accommodating the electrode assembly 110, and an electrode extending from the electrode assembly 110. Tabs 130 and lead terminals 140 connected to the electrode tabs 130.

The electrode assembly 110 included in the secondary battery according to the exemplary embodiment of the present invention includes an electrode 150 and a separator 160. The electrode 150 is divided into a first electrode 151 and a second electrode 152 according to the electrical polarity. The electrode assembly 110 may have a stack structure in which the first electrode 151, the separator 160, and the second electrode 152 are sequentially stacked. The stacked structure may increase battery capacity by increasing the number of stacked layers of the electrodes 150 in the electrode assembly 110 or by increasing the area of the electrodes 150. The electrode assembly 110 may also be formed as a wound structure in which a separator is disposed between the sheet-shaped first electrode 151 and the second electrode 152 and wound in a roll shape. The shape is not particularly limited as long as it is a shape used in the technical field of the present invention.

The electrode 150 may include an electrode current collector 150a and an active material layer 150c disposed on at least one surface of the electrode current collector 150a. The first electrode 151 or the second electrode 152 may be an anode or a cathode, respectively.

The positive electrode may include a current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The cathode active material layer may be formed of a mixture of a cathode active material, a conductive agent, and a binder, and the mixture may further include a filler. The negative electrode may include a negative electrode current collector and a negative electrode active material positioned on the negative electrode current collector. The negative electrode may further include a conductive material, a binder, a filler, and the like.

The positive electrode current collector has a high conductivity without causing a chemical change in the lithium secondary battery according to an embodiment of the present invention. The positive electrode current collector may increase the adhesion of the positive electrode active material by forming minute unevenness on the surface, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric. Specific examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum. And the stainless steel may be surface treated with carbon, nickel, titanium, silver, and the like on the surface.

Specific examples of the positive electrode active material include layered compounds such as lithium transition metal oxide, lithium cobalt oxide (LiCoO ₂ ), and lithium nickel oxide (LiNiO ₂ ); Compounds substituted with one or two transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 - x} O ₄ (x = 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Lithium manganese composite oxides represented by the formula LiNi _{1 - x} M _x O ₂ (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Spinel-structure lithium manganese oxide represented by LiNi _x Mn _{2 - x} O ₄ ; LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ ; Nickel cobalt manganese oxide etc. are mentioned.

The conductive material has conductivity without causing chemical change in the lithium secondary battery according to the embodiment of the present invention. Specific examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or conductive materials such as polyphenylene derivatives.

The binder is a component that assists in bonding the positive electrode active material and the conductive material to the current collector. Specific examples of the binder include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, reconstituted cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene monomer (EPDM) rubber, hydrogenated nitrile butadiene rubber (HNBR), sulfonated EPDM, styrene butadiene rubber, fluorine rubber, various copolymers, and the like.

The filler is a component that inhibits expansion of the positive electrode, and is a fibrous material that does not cause chemical change in the lithium secondary battery according to an embodiment of the present invention. Examples of the filler include olefin polymers such as polyethylene and polypropylene; And fibrous materials such as glass fibers and carbon fibers.

The negative electrode current collector has conductivity without causing chemical change in the lithium secondary battery according to the exemplary embodiment of the present invention. Specific examples of the negative electrode current collector include copper, stainless steel, aluminum, aluminum-cadmium alloy, nickel, titanium, calcined carbon and the like. The copper or stainless steel may be surface treated with carbon, nickel, titanium, silver, or the like on the surface. Like the positive electrode current collector, the negative electrode current collector may form fine irregularities on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics. have.

Specific examples of the negative electrode active material include carbon such as hardly graphitized carbon and graphite carbon; Li _x Fe ₂ O ₃ (0 ≦ _x ≦ 1), Li _x WO ₂ (0 ≦ _x ≦ 1), Sn _x Me _{1 - x} Me ' _y O _z (Me = Mn, Fe, Pb, Ge; Me' Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 <x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; Metal oxides such as SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , GeO, GeO ₂ , Bi ₂ O ₃ , and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based material; Titanium oxide; Lithium titanium oxide, etc.,

Description of the conductive material, the binder and the filler is omitted because the same as the conductive material, binder, filler used for the positive electrode.

The separator 160 prevents a short circuit between the cathode and the anode and provides a movement path of lithium ions. As the separator 160, an insulating thin film having high ion permeability and mechanical strength may be used. Specific examples of the separator 160 may include polyolefin-based polymer membranes such as polypropylene and polyethylene or multiple membranes thereof, microporous films, woven fabrics, and nonwoven fabrics. When a solid electrolyte such as a polymer is used as the electrolyte to be described later, the solid electrolyte may serve as a separator.

Meanwhile, an uncoated portion 150b in which the active material layer 150c is not formed may be formed at the edge of the electrode 150. The electrode tab 130 to be described later may be electrically connected to the uncoated portion 150b. More specifically, the first electrode tab 131 and the second electrode tab 132 may be electrically connected to the first electrode 151 and the second electrode 152 through the uncoated portion 150b, respectively. The uncoated portion 150b and the electrode tab 130 may be electrically connected by resistance welding, ultrasonic welding, and laser welding.

The electrode tab 130 is divided into a first electrode tab 131 and a second electrode tab 132. The first electrode tab 131 may be a positive electrode tab, and the second electrode tab 132 may be a negative electrode tab. The electrode tab 130 may be formed of a metal material having excellent conductivity, among which the first electrode tab 131 may be formed of aluminum or nickel, and the second electrode tab 132 may be formed of copper or nickel. have.

The lead terminal 140 included in the lithium secondary battery according to the exemplary embodiment of the present invention extends from the electrode assembly 110 and is drawn out of the battery case 120 across the battery case 120. And a first lead terminal 141 and a second lead terminal 142. The lead terminal 140 may be drawn out through the sealing parts 121a and 122a of the first battery case 121 and the second battery case 122.

The first lead terminal 141 may be a positive lead terminal electrically connected to the first electrode 151 via a first electrode tab 131, and the second lead terminal 142 may be the second electrode. It may be a cathode lead terminal electrically connected to the second electrode 152 via a tab 132. The lead terminal 140 and the electrode tab 130 may be connected by ultrasonic welding.

The insulating member 170 included in the lithium secondary battery according to the exemplary embodiment of the present invention may be disposed at a portion where the lead terminal 140 and the battery case 120 cross each other. Specifically, the insulating member 170 according to an embodiment of the present invention is the first insulating member 171 and the battery case disposed at the intersection of the first lead terminal 141 and the battery case 120. A second insulating member 172 may be disposed at a portion where the 120 and the second lead terminal 142 cross each other and have a thickness different from that of the first insulating member 171.

The insulating member 170 may not only function as a safety mechanism for preventing ignition and explosion of the secondary battery under high temperature and / or high pressure, but also may electrically connect the lead terminal 140 and the battery case 120 under normal conditions. It functions to insulate by

The insulating member 170 may be disposed on both surfaces as well as one surface of the lead terminal 140. Furthermore, the insulating member 170 may be disposed surrounding the lead terminal 140.

The thickness ratio of the lead terminal 140 and the insulating member 170 may be 10: 2 to 10: 7. If the above range is satisfied, the lead terminal 140 and the battery case 120 may be electrically insulated without significantly affecting the total thickness of the lithium secondary battery according to the exemplary embodiment of the present invention.

The thickness of the first insulating member 171 may be thicker than the thickness of the second insulating member 172, and specifically, the thickness of the first insulating member 171 may be the thickness of the second insulating member 172. It can be 1.1 to 2 times thicker. The reason for this is that the sealing state of the battery case 120 is released as the insulating member 170 is separated from the lead terminal 140 in a high temperature and / or high pressure condition, and the thickness of the first insulating member 171 is increased. When the thickness of the second insulating member 172 is greater than the thickness of the second insulating member 172, the second insulating member 171 may not be peeled between the first insulating member 171 and the first lead terminal 141 even under the same temperature and / or pressure conditions. This is because only peeling between the member 172 and the second lead terminal 142 occurs. Accordingly, when the thickness of the insulating member positioned in the direction in which the gas is desired to be thinned is formed, the gas generated inside the battery may be induced and discharged in the desired direction under high temperature and / or high pressure conditions. Here, the gas may be a gas generated while the electrolyte is vaporized.

When the first insulating member 171 and the second insulating member 172 satisfy the above-described thickness ratio, the thickness of the first insulating member 171 may be 120 to 180 μm, and the second insulating member The thickness of the 172 may be 80 ~ 120㎛.

The insulating member 170 may have a multilayer structure, and specifically, may have a three-layer structure. When the insulating member 170 has a three-layer structure, the insulating member 170 may include a lower layer facing the lead terminal 140, a middle layer positioned on the lower layer, and an upper layer disposed on the middle layer and facing the battery case 120. Can be. The thickness of the middle layer may be thicker than the lower layer and the upper layer, the thickness of the lower layer and the upper layer may be equal to each other or the thickness of the upper layer may be thicker than the lower layer.

Melting points of the lower layer, the middle layer and the upper layer may be different from each other. Specifically, the melting point of the middle layer may be 150 to 170 ° C. in both the first insulating member 171 and the second insulating member 172. The melting point of the lower layer may be 20 ° C to 40 ° C lower than the melting point of the middle layer, the melting point of the upper layer may be 5 ° C to 10 ° C lower than the melting point of the middle layer. When the melting point difference described above is satisfied, peeling does not occur between the lead terminal 140 and the lower layer 170a under high temperature and / or high pressure, and between the lower layer 170a and the middle layer 170b and / or the middle layer. Peeling may occur between the 170b and the upper layer 170c. And, by adjusting the melting point difference of each layer, it can be adjusted so that peeling occurs between the lower layer and the middle layer and / or between the middle layer and the upper layer.

Specific examples of the insulating member 170 may include polypropylene. When the insulating member 170 has a multilayer structure, the lower layer 170a may use a mixture of an acid-treated polypropylene and a normal polypropylene to improve adhesion to the lead terminal 140. The said middle layer can use a normal polypropylene independently. The upper layer 170c may use a mixture of acid-treated polypropylene, polyethylene, and normal polypropylene to improve adhesion with the battery case 120, wherein the acid-treated polypropylene is maleic anhydride. Ride polypropylene (MAH PP).

The battery case 120 included in the lithium secondary battery according to an embodiment of the present invention accommodates the electrode assembly 110 and functions to insulate and protect the electrode assembly 110 from an external environment. The battery case 110 may be formed of a laminate sheet including a metal layer and a resin layer. Specifically, the battery case 110 may be formed of an inner layer of a resin layer, an intermediate layer of a metal layer, and an outer layer of a resin layer. Specific examples of the inner layer include an unstretched polypropylene resin. Specific examples of the intermediate layer may include aluminum that can prevent leakage of external moisture and electrolyte. The outer layer may be a single layer or multiple layers, and specific examples thereof include biaxially stretched nylon, polyethylene terephthalate, and polyethylene naphthalate, which are resins having excellent weather resistance.

The battery case 120 may include a first battery case 111 and a second battery case 112 forming a receiving space. The electrode assembly 120 may be sealed by arranging the electrode assembly 110 in a receiving space and bonding the first battery case 111 and the second battery case 112 to face each other. In more detail, the sealing parts 111a and 112a facing each other of the first battery case 111 and the second battery case 112 are thermally fused to form an electrode assembly 110 and an electrolyte (not shown). May be sealed.

Lithium secondary battery according to an embodiment of the present invention may include an electrolyte (not shown). The electrolyte may be a lithium salt-containing nonaqueous electrolyte. Examples of the lithium salt include LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, lower aliphatic lithium carbonate, lithium tetraphenylborate, imide and the like.

The nonaqueous electrolyte is not particularly limited as long as it is used in the battery. Specific examples thereof include a nonaqueous organic solvent, an organic solid electrolyte, and an inorganic solid electrolyte. In the lithium secondary battery according to an embodiment of the present invention, it is preferable to use an organic solid electrolyte which is a polymer electrolyte. Specific examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, aggitation lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and ionic dissociation. The polymer containing group etc. are mentioned.

The lithium secondary battery of the present invention may reduce the risk of ignition and explosion by inducing and discharging the gas generated while the electrolyte is vaporized under high temperature and / or high pressure conditions, that is, internal gas in a specific direction.

The lithium secondary battery of the present invention may induce and discharge the gas generated while the electrolyte is vaporized only by controlling the thickness of the insulating member located on the lead terminal without adding a separate component and adding a process.

Hereinafter, preferred embodiments are provided to help the understanding of the present invention, but the above embodiments are merely illustrative of the present disclosure, and various changes and modifications within the scope and spirit of the present disclosure are apparent to those skilled in the art. It is natural that such variations and modifications fall within the scope of the appended claims.

<Example>

Manufacture of anode

92 g of a lithium cobalt composite oxide as a positive electrode active material, 4 wt% of carbon black as a conductive material, and 4 wt% of polyvinylidene fluoride (PVdF) as a binder polymer were used to prepare a mixture of 200 g of N-methyl-2- as a solvent. A positive electrode mixture slurry was prepared by adding to 220 ml pyrrolidone (NMP). The positive electrode mixture slurry was applied to an aluminum (Al) thin film of a positive electrode current collector having a thickness of 20 μm and dried to prepare a positive electrode, and then roll press was performed.

Preparation of Cathode

A negative electrode mixture slurry was prepared by preparing 200 g of a mixture of 96 wt% carbon powder as a negative electrode active material, 1 wt% carbon black as a conductive material, and 3 wt% PVdF as a binder polymer, and then adding it to 220 ml of NMP as a solvent. The negative electrode mixture slurry was applied to a thin copper (Cu) thin film, which is a negative electrode current collector having a thickness of 10 μm, and dried to prepare a negative electrode, followed by roll press.

Manufacture of batteries

The electrode assembly was manufactured by stacking the positive electrode, the negative electrode, and the polyethylene separator prepared above. The positive electrode and the aluminum positive electrode tab were connected by ultrasonic welding, and the negative electrode and the copper negative electrode tab were connected by ultrasonic welding. The aluminum positive electrode tab and the positive electrode lead terminal (aluminum (Al050) -nickel-copper (C1100 plated with 1 μm of nickel on the surface)) were connected by ultrasonic welding.

The copper negative electrode tab and the negative electrode lead terminal (aluminum (Al050) -nickel-copper (C1100 plated with 1 μm of nickel on the surface)) were connected by ultrasonic welding. A mixture (lower layer) / normal polypropylene (middle layer) / MAH PP (3 weight) of maleic acid anhydride polypropylene (MAH PP) (3% by weight) and normal polypropylene (97% by weight) above and below the positive electrode lead terminal. %), A mixture of polyethylene (17 wt%) and normal polypropylene (80 wt%) (upper layer) (thickness: 40 μm / 60 μm / 50 μm, melting point: 140 ° C./160° C./150° C.) An insulating member was formed. A mixture of MAH PP (3% by weight) and normal polypropylene (97% by weight) / normal polypropylene (middle layer) / MAH PP (3% by weight) and polyethylene (17% by weight) above and below the negative lead terminal And a second insulating member composed of a mixture (upper layer) (thickness: 30 m / 40 m / 30 m, melting point: 140 ° C./160° C./150° C.) of normal polypropylene (80% by weight).

Subsequently, in the pouch type battery case having a PP / Al / ONY / PET structure, an electrode assembly in which an electrode tab and a lead terminal are connected is disposed, the lead terminal is drawn out of the battery case, and the insulating member is disposed in the battery case. After arranging to face the pouch type battery case, heat sealing was performed. After heat fusion, the pouch type battery case was double side folded.

Comparative Example

The same electrode assembly as in Example was prepared. The positive electrode and the aluminum positive electrode tab were connected by ultrasonic welding, and the negative electrode and the copper negative electrode tab were connected by ultrasonic welding. The aluminum positive electrode tab and the positive electrode lead terminal (aluminum (Al050) -nickel-copper (C1100 plated with 1 μm of nickel on the surface)) were connected by ultrasonic welding. The copper negative electrode tab and the negative electrode lead terminal (aluminum (Al050) -nickel-copper (C1100 plated with 1 μm of nickel on the surface)) were connected by ultrasonic welding.

A mixture of MAH PP (3% by weight) and normal polypropylene (97% by weight) / normal polypropylene (middle layer) / MAH PP (3% by weight) and polyethylene (17% by weight) above and below the positive and negative lead terminals %) And an insulating member having a mixture (upper layer) (thickness: 40 µm / 60 µm / 50 µm, melting point: 140 ° C / 160 ° C / 150 ° C) of normal polypropylene (80% by weight) were formed.

Subsequently, in the pouch type battery case having a PP / Al / ONY / PET structure, an electrode assembly in which an electrode tab and a lead terminal are connected is disposed, the lead terminal is drawn out of the battery case, and an insulating member contacts the battery case. The pouch type battery case was heat sealed and sealed. After heat fusion, the pouch type battery case was double side folded.

<Test Example>

The lithium secondary batteries prepared in Examples and Comparative Examples were placed in a high temperature box at 100 ° C. and collected after 100 minutes.

FIG. 2 is a photograph taken with a general camera of the entire lithium secondary battery of the collected embodiment, and FIG. 3 is a photograph taken with an optical microscope showing a section taken along the A↔B portion of the lithium secondary battery of the embodiment.

Referring to FIG. 2, traces of gas leakage from the lithium secondary battery of the collected embodiment were found. Referring to FIG. 3, a gap is formed between the lower layer 172a and the middle layer 172b of the second insulating member 172 of the multilayer structure disposed on the cathode lead terminal 142 while the internal gas flows to the outside. It was found that formed. Through this, it was confirmed that the secondary battery according to the present invention does not ignite and explode because the internal gas flows to the outside at a high temperature.

110: electrode assembly 120: battery case
121: first battery case 121a: sealing portion of the first battery case
122: second battery case 122a: sealing portion of second battery case
130: electrode tab 131: first electrode tab
132: second electrode tab 140: lead terminal
141: first lead terminal 142: second lead terminal
150: electrode 150a: electrode current collector
150b: uncoated portion 150c: active material layer
151: first electrode 152: second electrode
160: separator 170: insulating member
171: first insulating member 172: second insulating member
172a: lower layer of second insulating member
172b: middle layer of second insulating member
172c: upper layer of second insulating member

Claims (11)

An electrode assembly;
A battery case accommodating the electrode assembly;
A lead terminal extending from the electrode assembly and including a first lead terminal and a second lead terminal drawn out of the battery case; And
A second insulating member disposed at a portion where the battery case and the first lead terminal cross each other, and a second insulating member disposed at a portion where the battery case and the second lead terminal cross each other and having a different thickness from the first insulating member; Including an insulation member including an insulation member,
The insulating member,
Multi-layered structure,
A lower layer facing the lead terminal, a middle layer positioned on the lower layer, and an upper layer positioned on the middle layer and facing the battery case;
Melting point of the middle layer,
150 ~ 170 ℃,
Melting point of the lower layer,
20 to 40 degreeC lower than the melting point of the middle layer,
Melting point of the upper layer,
Lithium secondary battery, characterized in that 5 ℃ to 10 ℃ lower than the melting point of the middle layer. The method according to claim 1,
The electrode assembly may include a first electrode, a second electrode, and a separator, wherein the first electrode is electrically connected to the first lead terminal, and the second electrode is electrically connected to the second lead terminal. Lithium secondary battery. The method according to claim 1,
The thickness ratio of the lead terminal and the insulating member is 10: 2 to 10: 7 lithium secondary battery. The method according to claim 1,
The thickness of the first insulating member is a lithium secondary battery, characterized in that thicker than the thickness of the second insulating member. The method according to claim 4,
The thickness of the first insulating member is a lithium secondary battery, characterized in that 1.1 to 2 times thicker than the thickness of the second insulating member. delete delete delete delete The method according to claim 1,
And an electrode tab connected to the electrode assembly and the lead terminal. The method according to claim 1,
The lithium secondary battery is a lithium secondary battery comprising a polymer electrolyte.

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