KR20180050165A - Lithium secondary battery having improved safty - Google Patents

Abstract

The present invention relates to a lithium secondary battery which includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The positive electrode comprises a positive electrode active material represented by chemical formula 1, Li_(1+x)(Ni_aCo_bMn_c)O_2. In the lithium secondary battery, a value, obtained by multiplying battery resistance by the area of the positive electrode at SOC of 50, is greater than or equal to 1.965 mΩ·m^2. The lithium secondary battery of the present invention maintains heat emission at a certain temperature or lower even when passing through a nail, and ignition does not occur, thereby exhibiting excellent safety.

Description

TECHNICAL FIELD [0001] The present invention relates to a lithium secondary battery having improved safety,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lithium secondary battery having improved safety, and more particularly, to a lithium secondary battery having improved safety of penetration.

As technology development and demand for mobile devices have increased, there has been a rapid increase in demand for secondary batteries as energy sources. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and operating potential, long cycle life, Batteries have been commercialized and widely used.

The lithium secondary battery generally comprises a positive electrode containing a positive electrode active material, a negative electrode including a negative electrode active material, a separator and an electrolyte, and is charged and discharged by intercalation-decalation of lithium ions. The lithium secondary battery has a high energy density, a large electromotive force, and a high capacity, so it is applied to various fields.

However, lithium secondary batteries have safety problems such as ignition and explosion due to the use of organic electrolytic solution, and they have a disadvantage that they are difficult to manufacture. In particular, when a lithium secondary battery is short-circuited due to the contact between the positive electrode and the negative electrode, the lithium secondary battery explodes with extreme heat generation, thus posing a serious problem in safety. In fact, there are a few cases where a lithium secondary battery mounted in a mobile device is ignited or exploded

In addition, when a material having electrical conductivity such as a nail penetrates the battery, electrochemical energy inside the battery is converted into thermal energy, and rapid heat generation occurs. As a result, the positive or negative electrode material chemically reacts with heat, Causing a safety problem such as ignition or explosion of the battery.

Specifically, when a material having electrical conductivity such as a nail penetrates the battery, the positive and negative electrodes inside the battery are locally short-circuited within the battery, and an excessive current locally flows to the short circuit position, and heat is generated due to the current. Since the magnitude of the short-circuit current due to local short circuit is inversely proportional to the resistance, the short-circuit current flows through the metal foil mainly used as a current collector, and the current flows through the metal foil used as the current collector. A very high heat is locally generated around the portion.

If a heat is generated in the battery, the separator shrinks and short-circuits the positive and negative electrodes again, and repeated heat generation and shrinkage of the separator shrinks the short-circuit section, resulting in thermal runaway, And the electrolytic solution react with each other or burn, which is a very large exothermic reaction, which eventually causes the battery to ignite or explode. This risk is particularly important as the energy density increases as the capacity of the lithium secondary battery increases.

In order to overcome such a problem and to improve the safety during overcharging, a material having high thermal conductivity or a bulletproof material is attached to the pouch so as to pass the other material before the nail penetrates, However, such a method has a problem in that additional process and cost are required in manufacturing the secondary battery, the volume increases, and the capacity per unit volume is reduced.

GB 2012-0048463 A

The inventors of the present invention have repeatedly conducted research to solve the above problems. As a result, they found that when the value obtained by multiplying the internal resistance of the lithium secondary battery by the area of the anode satisfies a specific range, safety of the battery is improved Thereby completing the invention.

Disclosure of Invention Technical Problem [8] The present invention provides a lithium secondary battery having improved safety, and particularly, a lithium secondary battery having enhanced through-hole safety.

In order to solve the above problems,

A lithium secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,

Wherein the positive electrode comprises a positive electrode active material represented by the following Formula 1,

[Chemical Formula 1]

Li _{1 + x} (Ni _a Co _b Mn _c ) O ₂

(0.55? A? 0.8, 0.1? B? 0.22, 0.1? C? 0.22, -0.2? X? 0.2, x + a + b + c = 1)

Wherein the lithium secondary battery has a cell resistance of SOC 50 × total area of the positive electrode of 1.965 mΩ · m ² or more.

The lithium secondary battery of the present invention maintains the heat generation at a predetermined temperature or lower even when passing through a nail, so that ignition does not occur and the battery exhibits excellent safety.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be interpreted in the meaning and concept consistent with the technical idea of the present invention.

The lithium secondary battery of the present invention is a lithium secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode includes a positive electrode active material represented by the following Formula 1, And the total area of the battery resistance x anode at 50 days is 1.965 m? M ² or more.

[Chemical Formula 1]

Li _{1 + x} (Ni _a Co _b Mn _c ) O ₂

(0.55? A? 0.8, 0.1? B? 0.22, 0.1? C? 0.22, -0.2? X? 0.2, x + a + b + c = 1)

According to research conducted by the present inventors, when the value obtained by multiplying the area ratio resistance of the anode of a lithium secondary battery, that is, the battery resistance at SOC 50 times the total area of the positive electrode, was 1.965 mΩ · m ^{2 or} more, the lithium secondary battery passed through the nail The battery temperature was raised to below the temperature at which the ignition occurred, and it was found that the battery had an excellent effect in terms of safety. Multiplied by the total area of the positive electrode in the battery resistance when the SOC 50 days, specifically 1.965 mΩ · m ² to 3 mΩ · m may be ^2, more specifically, 1.965 mΩ · m ² to 2.59 mΩ · m ² il have. The total area of the positive electrodes represents an area obtained by summing the areas of the individual positive electrodes included in the lithium secondary battery.

The total area of the positive electrode included in the lithium secondary battery when the lithium secondary battery according to an example of the present invention satisfies the area ratio resistance of the positive electrode is 1 m ² To 10 m ^2, it can be a particularly 1.2 m ² to 5 m ^2, more specifically 1.52 m ² to 2.8 m ^2.

When the total area of the positive electrodes satisfies 1 m ² to 10 m ² , the resistance value of the lithium secondary battery at SOC 50 corresponds to the resistance value of a typical lithium secondary battery, Can be satisfied.

On the other hand, the area of one positive electrode included in the lithium secondary battery may be 0.02 m ² to 1 m ² , specifically 0.02 m ² to 0.6 m ² , more specifically 0.02 m ² to 0.5 m ² .

When the area of the individual positive electrodes constituting the lithium secondary battery is enlarged, the internal resistance of the battery is decreased. When the area of the individual positive electrode is 0.02 m ² to 1 m ² , the SOC of the lithium secondary battery The resistance value at that time becomes an appropriate range.

The lithium secondary battery has a battery resistance (DC-IR) at SOC 50 of 0.1 mΩ To 2.5 m [Omega], and specifically 0.5 m [Omega] To 1.9 m [Omega], more specifically 0.7 m [ To 1.7 m [Omega].

When the battery resistance (DC-IR) at the SOC 50 of the lithium secondary battery is 0.1 mΩ To 2.5 m OMEGA, it is possible to satisfy the range of the area ratio resistance value of the anode, but the resistance of the battery is within the appropriate range, and excellent electrochemical performance can be exhibited.

The total area of the cathodes or the area of the individual cathodes is not particularly limited and may be determined in accordance with a conventional method of manufacturing a lithium secondary battery in proportion to the total area of the positive electrodes or the area of the individual positive electrodes.

The negative electrode may include a silicon-based negative electrode active material.

The silicon-based negative electrode active material is Si, silicon oxide particles (SiO _y, 0 <y≤2), Si- from the metal alloy, and the group consisting of an alloy of the Si particles and silicon oxide (SiO _y, 0 <y≤2) And the silicon-based anode active material may include at least one selected from the group consisting of Si, silicon oxide particles (SiOy, 0 < _y ? 2) and alloys thereof. . At this time, the silicon oxide particles _{(SiO y, 0 <y <} 2) may be a composite consisting of a crystalline SiO ₂ and amorphous Si.

The lithium secondary battery according to an embodiment of the present invention may be a high capacity lithium secondary battery comprising a high nickel content transition metal oxide as the positive electrode active material and a silicon based negative electrode active material as the negative electrode active material. The lithium secondary battery according to the present invention may have a capacity of 10 Ah to 300 Ah, more specifically, a capacity of 35 Ah to 200 Ah.

When the lithium secondary battery has a capacity of 10 Ah to 300 Ah and a value obtained by multiplying the battery resistance at SOC 50 by the area of the positive electrode is 1.965 m? M ^{2 or} more, when the lithium secondary battery is passed through the nail The battery temperature of the battery is raised to a temperature lower than the temperature at which ignition occurs, thereby exhibiting an excellent effect in terms of safety of the battery.

The lithium secondary battery according to an exemplary embodiment of the present invention has excellent safety. Specifically, when the lithium secondary battery is subjected to a nail penetration test in a fully charged state, the internal temperature of the battery is 100 ° C or less, specifically 80 ° C Or less, more specifically 30 DEG C or less, and no ignition occurs.

The nail penetration test is a nail test as a typical test for testing the safety of a lithium secondary battery. The nail penetration test is a method of penetrating the nail from the outside of the lithium secondary battery. When a serious internal short circuit occurs due to an external force, It is done to prepare.

When the internal short circuit occurs, all the energy instantaneously rushes to a specific point where the short circuit occurs. As a result, the battery may be ignited, ruptured and exploded due to thermal runaway due to instant thermal and side reactions. The lithium secondary battery according to the embodiment can maintain excellent internal safety because the internal temperature of the battery is kept at 100 占 폚 or less even when the nail penetration test is performed in the fully charged state.

In the nail penetration test, for example, the lithium secondary battery was fully charged and nail (nail) having a diameter of about 2.5 mm was used to pass through the center of the battery, and it was observed whether or not the battery was ignited. And a method of measuring the temperature of the penetration point.

The lithium secondary battery according to an exemplary embodiment of the present invention may be a stack type or a stack and folding type lithium secondary battery.

The stacked lithium secondary battery may be a lithium secondary battery including an electrode assembly manufactured by vertically stacking a cathode, a separator, and an anode. The stacked and folded lithium secondary battery may include a positive electrode / separator / A bicell of a full-cell structure or a positive electrode (cathode) / separator / cathode (anode) / separator / anode (cathode) structure is manufactured by using a long- And a lithium secondary battery including an electrode assembly.

The anode may be prepared by a conventional method known in the art. For example, a slurry is prepared by mixing and stirring a solvent, a binder, a conductive material, and a dispersant as necessary in the cathode active material, and then applying (coating) the cathode active material to a current collector of a metal material, .

The current collector of the metal material is a metal having high conductivity and is a metal which can easily adhere to the slurry of the cathode active material and is not particularly limited as long as it has high conductivity without causing chemical change in the battery in the voltage range of the battery But not limited to, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, or the like. In addition, fine unevenness may be formed on the surface of the current collector to increase the adhesive force of the positive electrode active material. The current collector can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric, and may have a thickness of 3 to 500 탆.

Examples of the solvent for forming the positive electrode include organic solvents such as NMP (N-methylpyrrolidone), DMF (dimethylformamide), acetone, and dimethylacetamide, and water. These solvents may be used alone or in combination of two or more Can be mixed and used. The amount of the solvent used is sufficient to dissolve and disperse the cathode active material, the binder and the conductive material in consideration of the coating thickness of the slurry and the production yield.

Examples of the binder include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, Polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM) Sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, poly acrylic acid, and polymers in which hydrogen is substituted with Li, Na, or Ca, or Various kinds of binder polymers such as various copolymers can be used.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon black such as acetylene black, Ketjen black, channel black, panes black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Conductive tubes such as carbon nanotubes; Metal powders such as fluorocarbon, aluminum and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. The conductive material may be used in an amount of 1 wt% to 20 wt% based on the total weight of the positive electrode slurry.

The dispersing agent may be an aqueous dispersing agent or an organic dispersing agent such as N-methyl-2-pyrrolidone.

The negative electrode may be prepared by a conventional method known in the art. For example, the negative electrode active material, additives such as a binder and a conductive material are mixed and stirred to prepare an anode active material slurry, which is then applied to an anode current collector, Followed by compression.

The binder may be used to bind the negative electrode active material particles to maintain the formed body. Any conventional binder used in preparing the slurry for the negative electrode active material is not particularly limited, and examples thereof include polyvinyl alcohol, carboxymethyl cellulose, Polyvinylidene fluoride (PTFE), polyvinylidene fluoride (PVdF), polyethylene or polypropylene, and the like can be used. In addition, an acrylic resin such as acrylic resin (polyvinyl chloride), polyvinyl pyrrolidone, polytetrafluoroethylene Acrylonitrile-butadiene rubber, styrene-butadiene rubber, styrene-butadiene rubber, and acrylic rubber, or a mixture of two or more thereof. The aqueous binders are economical, environmentally friendly, harmless to the health of workers, and are superior to non-aqueous binders, and have a better binding effect than non-aqueous binders. Thus, the ratio of the active materials of the same volume can be increased and the capacity of the aqueous binders can be increased. Preferably styrene-butadiene rubber can be used.

The binder may be contained in an amount of 10 wt% or less, specifically 0.1 wt% to 10 wt%, based on the total weight of the slurry for the negative electrode active material. If the content of the binder is less than 0.1 wt%, the effect of the binder is insufficient, which is undesirable. If the content of the binder is more than 10 wt%, the relative content of the active material may decrease to increase the binder content. not.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; And conductive materials such as polyphenylene derivatives. The conductive material may be used in an amount of 1 wt% to 9 wt% with respect to the total weight of the slurry for the negative electrode active material.

The negative electrode collector used in the negative electrode according to an embodiment of the present invention may have a thickness of 3 to 500 mu m. The negative electrode current collector is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery. The negative electrode current collector may be formed on the surface of copper, gold, stainless steel, aluminum, nickel, titanium, sintered carbon, Carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

As the separator, a conventional porous polymer film conventionally used as a separator, such as a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene-butene copolymer, an ethylene-hexene copolymer and an ethylene-methacrylate copolymer Porous nonwoven fabric such as high melting point glass fiber, polyethylene terephthalate fiber or the like may be used as the nonwoven fabric, but the present invention is not limited thereto.

Examples of the anion of the lithium salt include F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , and N (CN) as the anion of the lithium salt. _{^{2 -, BF 4 -, ClO}} 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, ^{_{(CF 3) 6 P -,}} CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO _{^{-, (CF 3 SO 2)}} 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

Examples of the electrolyte used in the present invention include an organic-based liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used in the production of a lithium secondary battery. no.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be square or pouch type.

The lithium secondary battery according to the present invention can be used as a unit battery in a middle- or large-sized battery module including a plurality of battery cells.

Specific examples of the medium and large-sized devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and electric power storage systems.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples, but the present invention is not limited by these Examples and Experimental Examples. The embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Examples 1 to 3

92% by weight of Li (Ni _0.8 Co _0.1 Mn _0.1 ) O ₂ as a cathode active material, 4% by weight of carbon black as a conductive material and 4% by weight of polyvinylidene fluoride (PVdF) -2-pyrrolidone (NMP) to prepare a positive electrode mixture slurry. The above-described anode mixture slurry was continuously applied to an aluminum (Al) thin film roll of 35 cm in width and 15 m in thickness on the positive electrode current collector, dried, and then rolled. The positive electrode was prepared in the same manner as described in Table 1 below.

Further, 95.8 wt% of silicone particles having an average particle diameter of 4.9 mu m (Shinetsu Co., Ltd.), 0.5 wt% of super-p as a conductive material, 2.5 wt% of styrene butadiene rubber (SBR) and carboxymethyl cellulose % And 1.2 wt% were mixed and added to NMP as a solvent to prepare a negative electrode active material slurry. The negative electrode mixture slurry was applied to a copper (Cu) thin film as an anode current collector having a width of 35 cm and a thickness of 8 占 퐉, dried, and then roll-pressed. The negative electrode was prepared as shown in Table 1 below.

A unit cell was fabricated through a separator composed of three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP) between the thus prepared positive electrode and negative electrode, 32 units of the unit cells were laminated, To prepare a lithium secondary battery.

Comparative Examples 1 and 2

A lithium secondary battery was prepared in the same manner as described in Examples 1 to 3, except that the positive electrode and the negative electrode were produced in the same manner as in Examples 1 to 3, except that the positive electrode and the negative electrode were prepared, respectively,

Experimental Example 1: Measurement of Resistance of Battery

The batteries manufactured in Examples 1 to 4 and Comparative Examples 1 to 5 were subjected to a hybrid pulse power characterization (HPPC) test to measure the resistance.

Specifically, the batteries prepared in each of Examples 1 to 4 and Comparative Examples 1 to 5 were charged from SOC 10 up to 2.8 V at 1 C to full charge (SOC = 100), and the batteries were stabilized for 1 hour , And the resistance of the pouch type secondary battery was measured by the HPPC test method for each SOC step while discharging the battery from SOC 100 to 10 at 10 ° C. The resistances at SOC 50 are shown in Table 1 below.

Experimental Example 2: Safety evaluation

In order to understand the safety of each of the batteries prepared in Examples 1 to 4 and Comparative Examples 1 and 2, the batteries prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were subjected to constant current / constant voltage CC / CV) condition to 4.4 V / 38 mA until 1 C, then the nail penetration test was carried out under full charge condition, and the temperature of the battery center was measured and the ignition was observed. The results are shown together in Table 1 below.

Anode size
(Width x
Length, cm) Cathode size
(Width x
Length, cm) Unit cell
Count Total area of anode
(m ² ) anode
Active material At SOC 50
resistance
(DC-IR, mΩ) Battery resistance at SOC 50
× total area of the anode battery
center
Temperature
(° C) Whether ignited Example 1 18 x 22 21 × 25 32 1.27 Li (Ni _0.8 Co _0.1 Mn _0.1 ) O ₂ 1.64 2.08 31 × Example 2 23 x 25 24 × 26 32 1.84 Li (Ni _0.8 Co _0.1 Mn _0.1 ) O ₂ 1.42 3.02 28 × Example 3 26 x 31 27 x 32 32 2.58 Li (Ni _0.8 Co _0.1 Mn _0.1 ) O ₂ 1.09 2.81 30 × Comparative Example 1 13 × 20 14 × 21 32 0.83 Li (Ni _0.8 Co _0.1 Mn _0.1 ) O ₂ 2.28 1.89 1096 ○ Comparative Example 2 15 x 19 16 × 20 32 0.91 Li (Ni _0.8 Co _0.1 Mn _0.1 ) O ₂ 2.11 1.92 1032 ○

Referring to Table 1, in the lithium secondary batteries of Examples 1 to 3, in which the battery resistance x the total area of the positive electrode at SOC 50 was 1.965 m? M ² or more, the battery core temperature was maintained at 31 占 폚 or less in the nail penetration test And thus ignition did not occur.

On the other hand, in the lithium secondary batteries of Comparative Examples 1 and 2, the total area of the battery resistance x anode was less than 1.965 m? · M ² at SOC 50, and that of the lithium secondary battery was increased to 1,000 ° C or more in the nail penetration test But ignited.

Claims (10)

A lithium secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
Wherein the positive electrode comprises a positive electrode active material represented by the following Formula 1,
[Chemical Formula 1]
Li _{1 + x} (Ni _a Co _b Mn _c ) O ₂
(0.55? A? 0.8, 0.1? B? 0.22, 0.1? C? 0.22, -0.2? X? 0.2, x + a + b + c = 1)
Wherein the lithium secondary battery has a total area of battery resistance x anode of 1.965 m? M ² or more at SOC 50.
The method according to claim 1,
The total area of the positive electrode included in the lithium secondary battery is 1 m ² To 10 m &lt; ^{2 &} gt ;.
The method according to claim 1,
Wherein an area of one positive electrode included in the lithium secondary battery is 0.02 m ² to 0.3 m ² .
The method according to claim 1,
The lithium secondary battery has a total area of the cell resistance when the SOC anode × 50 mΩ and il 1.965 m ² to 2.59 m ² mΩ and a lithium secondary battery.
The method according to claim 1,
The lithium secondary battery has a battery resistance (DC-IR) at SOC 50 of 0.1 mΩ &Lt; / RTI &gt; to 2 m OMEGA.
The method according to claim 1,
Wherein the negative electrode comprises a silicon-based negative active material.
The method according to claim 6,
The silicon-based negative electrode active material is Si, silicon oxide particles (SiO _y, 0 <y≤2), Si- from the metal alloy, and the group consisting of an alloy of the Si particles and silicon oxide (SiO _y, 0 <y≤2) may be to include a selected one or more, specifically, the silicon-based negative active material comprises Si, silicon oxide particles (SiO _y, 0 <y≤2) and at least one member selected from the group consisting of alloy In lithium secondary battery.
The method according to claim 1,
Wherein the lithium secondary battery has a capacity of 10 Ah to 300 Ah.
The method according to claim 1,
Wherein the lithium secondary battery is maintained at an internal temperature of 100 占 폚 or lower when a nail penetration test is performed in a fully charged state.
The method according to claim 1,
Wherein the lithium secondary battery is a stacked type or a stacked and folded type lithium secondary battery.