KR20150028739A - Secondary Battery Cell - Google Patents

Abstract

The present invention provides a battery cell wherein an electrode assembly including a cathode, an anode and a separation membrane for storing and discharging lithium ions is contained in a cell case together with electrolyte, and charge for activating an electrode is conducted in the range of state of charge (SOC) within the potential plateau of an anode in the process of manufacturing the battery cell.

Description

[0001] The present invention relates to a secondary battery cell,

An electrode assembly including a positive electrode, a negative electrode, and a separator capable of intercalating and deintercalating lithium ions is embedded in a cell case together with an electrolyte. Charging for activating the battery in a battery cell manufacturing process is performed by changing the filling depth in the flat potential of the negative electrode SOC: State of Charge).

In recent years, the demand for environmentally friendly alternative energy sources has become an indispensable factor for the future, as the increase in the price of energy sources due to depletion of fossil fuels and the interest in environmental pollution are amplified. Various researches on power generation technologies such as nuclear power, solar power, wind power, and tidal power have been continuing, and electric power storage devices for more efficient use of such generated energy have also been attracting much attention.

Particularly, as technology development and demand for mobile devices increase, the demand for batteries as energy sources is rapidly increasing. Recently, the use of secondary batteries as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV) In addition, the use area has been expanded for use as a power auxiliary power source through a grid, and accordingly, a lot of researches on a battery that can meet various demands have been conducted.

Lithium ion batteries having a high demand for a pouch-type secondary battery that can be applied to products such as mobile phones and the like in terms of the shape of the battery, and high energy density, discharge voltage, and output stability, There is a high demand for a lithium secondary battery such as a lithium ion polymer battery.

The lithium secondary battery has a structure in which a non-aqueous electrolyte containing a lithium salt is impregnated in an electrode assembly in which a porous polymer film is interposed between a positive electrode and a negative electrode each coated with a coating layer on a current collector. The cathode active material is mainly composed of a lithium cobalt oxide, a lithium manganese oxide, a lithium nickel oxide, a lithium composite oxide and the like, and the anode active material is mainly composed of a carbon-based material.

Generally, an electrode assembly including a positive electrode, a negative electrode, and a separator capable of intercalating and deintercalating lithium ions is embedded in a cell case together with an electrolyte solution, A battery cell having an electrode assembly and an electrolyte solution is activated.

The method of activating the battery cell varies greatly depending on the type of the battery cell. However, in the case of the pouch type battery cell, after charging / discharging is performed in a specific state of charge (SOC) range, aging period to remove the gas.

In this case, when a negative electrode made of a conventional carbon-based material is used, the range of charge depth for activating the battery in the manufacturing process of the battery cell is determined by adjusting the voltage band according to the anode of the battery cell, Performance can be improved.

However, in the lithium secondary battery using the carbon-based material as the negative electrode active material, an irreversible capacity is generated from a part of the lithium ions inserted into the layered structure of the carbon-based material at the time of the first charge / discharge and the discharge capacity is lowered. There is a problem that the reversible capacity of lithium gradually decreases due to the repetition of charging and discharging due to the generation of the compound, the discharge capacity is decreased and cycle deterioration occurs, and recently, there has been a problem that a negative electrode active material structurally stable and having good cycle characteristics , And lithium titanium oxide (LTO). The lithium secondary battery including such a lithium titanium oxide as a negative electrode active material has a relatively high oxidation / reduction potential of about 1.5 V with respect to the potential of Li / Li +, so that the decomposition of the electrolyte hardly occurs, Is excellent.

Therefore, in the case of using the lithium-titanium oxide as the negative electrode in the pouch-shaped battery cell, unlike the case of using the negative electrode made of the carbon-based material, the range of the charge depth Should be set.

However, in the pouch-shaped battery cell, when the lithium-titanium oxide is used as the negative electrode, it can be confirmed that gas is generated at a specific voltage level during charging and discharging for battery activation in the battery cell manufacturing process.

As a result of the decomposition reaction of the electrolyte solution, the gas generation generates decomposition by-products in addition to the gas, and the decomposition by-products greatly affect the surface chemical reaction during the aging process after the charging / discharging process of the battery cell It must be adjusted to form a stable active material surface through appropriate control, which directly affects the performance improvement of the battery cell.

Therefore, in the manufacturing process of the pouch-type battery cell using lithium-titanium oxide as the cathode, the setting of the charging depth range for performing the charging and discharging for activating the battery and the method thereof This is a necessity.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

The inventors of the present application conducted in-depth research and various experiments to find that charging for battery activation during battery cell fabrication was performed in the range of charge state (SOC) within the flat potential of the negative electrode, aging of the positive electrode and the negative electrode of the battery cell, the performance of the battery cell can be improved by forming a stable surface of the active material by affecting the surface chemical reaction according to the decomposition reaction of the electrolyte. In addition, It was confirmed that the performance of the battery cell can be improved by controlling the charging depth according to the capacity ratio (N / P ratio).

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a battery cell including an electrode assembly including a positive electrode, a negative electrode, and a separator capable of intercalating and deintercalating lithium ions, Charging is carried out in the charging depth range within the flat potential of the cathode.

The battery cell in which the charging is performed may be subjected to an aging process.

Therefore, the battery cell according to the present invention performs charging and discharging for battery activation in the range of depth of charge within the flat potential of the negative electrode as described above according to the capacity ratio of the positive electrode and the negative electrode, The performance of the battery cell can be improved through the formation of a stable active material surface.

In one specific example, the positive electrode of the battery cell may include a layered lithium metal oxide represented by the following formula (1) as a positive electrode active material.

Li _x (Ni _v Mn _w Co _y M _z ) O _{2 -te t} (1)

0? V? 0.9, 0? W? 0.9, 0? Y? 0.9, 0? Z? 0.9, x + v + w + y + z = 2, 0? T <0.2 ;

M is at least one metal or transition metal cation of +2 to +4 oxidation numbers;

A is an anion of -1 or -2 valence.

The positive electrode active material represented by the general formula (1) includes a mixed transition metal of Ni and Mn, and has an average oxidation number of total transition metals other than lithium of greater than +3, and a nickel content equal to or greater than a manganese content And may be a lithium metal oxide having a layered crystal structure satisfying a large requirement.

In the above formula (1), transition metals such as Ni, Mn and Co may be substituted with metals having a +2 to +4 oxidation number and / or other transition metal (M) , And in this case, the detailed substitution amount may be 0.3? Z? 0.6.

In the formula (1), the oxygen ion may be substituted by an anion (A) of oxidation-1 or -2 in a predetermined range, and the A in detail may be independently selected from the group consisting of F, Cl, Br and I Halogen, S, and N, which may be the same or different.

By substituting these anions, the binding force with the transition metal is improved and the structural transition of the compound is prevented, so that the lifetime of the battery can be improved.

More specifically, the oxide of Formula 1 may be a lithium metal oxide represented by Formula 2, and preferably Li (Ni _0.4 Mn _0.3 Co _0.3 ) O ₂ or Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ .

Li _x (Ni _v Mn _w Co _y ) O ₂ (2)

In the above formula, 0.8 <x? 1.3, 0? V? 0.9, 0? W? 0.9, 0? Y? 0.9, x + v + w + y + z = 2.

In another specific example, the negative electrode of the battery cell according to the present invention may include a lithium metal oxide represented by the following formula (3) as an anode active material.

Li _a M ' _b O _4c-d A _d (3)

In the above formula, M 'is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al and Zr;

a and b satisfy the relations 0.1 a 12; Is determined according to the oxidation number of M 'in the range of 0.2? B? 12;

c and d are determined according to the oxidation number in the range of 1? c? 3, 0? d <0.6;

A is one or more of an anion of -1 or -2.

Specifically, the lithium metal oxide may be Lithium Titanium Oxide (LTO) represented by the following Chemical Formula 4, preferably LiTi ₂ O ₄ or Li ₄ Ti ₅ O ₁₂ .

Li _a Ti _b O _4c (4)

In the above formula, 0.5? A? 8, 1? B? 8.5, 1? C? 3, and a + b = 3c.

Other components of the battery cell according to the present invention will be described below.

The positive electrode of the battery cell according to the present invention is prepared by applying a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, followed by drying and pressing. If necessary, a filler may be further added to the mixture.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with carbon, nickel, titanium, silver or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The conductive material is usually added in an amount of 1 to 50% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, 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 whiskey 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 binder is a component that assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 50 wt% based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

On the other hand, the negative electrode is manufactured by applying, drying and pressing an anode active material on an anode current collector, and may optionally further include a conductive material, a binder, a filler, and the like as described above.

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, a surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, 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 films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The electrolyte solution containing the lithium salt is composed of an electrolyte solution and a lithium salt. The electrolyte solution may be a non-aqueous organic solvent, an organic solid electrolyte, or an inorganic solid electrolyte, but is not limited thereto.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, 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, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution is preferably mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, . In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene sultone), and the like.

In one specific _{example, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) 2 , such as a lithium salt, a highly dielectric solvent of DEC, DMC or EMC Fig solvent cyclic carbonate and a low viscosity of the EC or PC of And then adding it to a mixed solvent of linear carbonate to prepare a lithium salt-containing non-aqueous electrolyte.

In the battery cell according to the present invention, charging and discharging for activating the battery are performed in the manufacturing process in the range of the filling depth in the flat potential of the cathode, and the filling depth range in the flat potential of the cathode is set to the potential of the cathode used in the battery cell Can be determined from the profile.

When a carbonaceous material is used as a negative electrode active material, the capacity of the negative electrode has to be larger than the capacity of the positive electrode due to the problem of reduction of the reversible capacity due to the generation of the lithium compound on the surface of the negative electrode. However, It is possible to prevent the lithium plating, thereby making it possible to design a cell having a negative capacity.

Therefore, when the high voltage anode is used, the gas discharge and byproduct generation caused by the operation of the cell at the potential at which the electrolytic solution in question is oxidized cause the total capacity of the cathode to be smaller than or equal to the total capacity of the anode (N / P ratio ≤ 1) , It is possible to prevent the potential of the anode from rising to prevent it from being caught by the cut-off voltage of the cathode first.

In one specific example, in the manufacturing process of the battery cell according to the present invention, the flat potential of the cathode can be determined from the profile of the potential of the cathode used in the battery cell.

More specifically, since the battery cell according to the present invention performs charging up to the flat potential range of the negative electrode in the initial charging / discharging process, the flat potential range of the negative electrode is determined from the profile of the potential of the negative electrode, The charging voltage and the capacity of the battery cell are determined in consideration of the charging depth according to the charging voltage.

In another specific example, the battery cell according to the present invention can perform charge / discharge in the range of SOC 20 to SOC 60 when the NP ratio is 0.9.

The method of setting the SOC according to the NP ratio can be deduced from a portfolio of experimental data on the lithium-to-lithium voltage of the active material components.

Therefore, the battery cell according to the present invention can improve the performance of the battery cell by forming a stable surface of the active material by allowing the surface chemical reaction according to the decomposition reaction of the electrolyte to be affected during the aging process of the battery cell.

The battery cell according to the present invention may be further subjected to a process of charging and discharging for activating the battery, followed by an aging process and then removing the gas.

The present invention provides a battery pack in which the battery cell is mounted on a pack case and further includes a battery pack. The device includes a notebook computer, a mobile phone, a PDP, a PMP, an MP3 player, a DSC Still Camera, a DVR, a smart phone, a GPS system, and a camcorder, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage device.

The structure of these devices and their fabrication methods are well known in the art, and a detailed description thereof will be omitted herein.

As described above, the battery cell according to the present invention performs charging and discharging for battery activation in the battery cell manufacturing process in the range of charge state (SOC) within the flat potential of the negative electrode, aging of the electrolyte membrane, it is possible to improve the performance of the battery cell by forming a stable surface of the active material by affecting the surface chemical reaction according to the decomposition reaction of the electrolyte. In addition, (N / P ratio) to improve the performance of the battery cell.

1 is a graph showing a profile of a potential of a battery cell according to an embodiment of the present invention.

Hereinafter, the present invention will be described in further detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

&Lt; Example 1 >

88 wt% of Li (Ni _0.4 Mn _0.3 Co _0.3 ) O ₂ , 8.5 wt% of Super-P (conductive agent) and 3.5 wt% of PVdF (binder) as a cathode active material were added to NMP to prepare a positive electrode mixture, Was applied to an aluminum foil having a thickness of 20 占 퐉 to prepare a positive electrode. Further, a negative electrode mixture was prepared by adding 83 wt% of Li ₄ Ti ₅ O _12, 7 wt% of Super-P (conductive agent) and 10 wt% of PVdF (binder) to the NMP as the negative electrode active material, , And an electrode assembly including the positive electrode and the negative electrode was prepared using Celgard TM as a separator, and a mixed solution of 30 vol% of EC, 40 vol% of DMC, and 30 vol% of EMC Aqueous electrolyte solution containing 1M LiPF ₆ was added to the cell assembly together with the electrode assembly to prepare a battery cell having an SOC100 potential of 2.75 V and an NP ratio of 0.9. And charging for activation of the battery cell was performed.

<Experimental Example 1>

The voltage according to the charging potential of the battery cell manufactured in Example 1 was measured, and the result is shown in FIG.

Referring to FIG. 1, it was found that the negative electrode of the battery cell manufactured in Example 1 had a flat potential in the range of SOC20 to SOC90, and when SOC60 or higher, the voltage curve starts to be inclined due to overcharge even though the potential is flat. have. It can be confirmed that the activation charge voltage of the battery cell is preferably 2.1 V to 2.25 V.

&Lt; Example 2 >

A battery cell was prepared in the same manner as in Example 1, except that charging for activating the battery cell was performed in the range of SOC20.

&Lt; Example 3 >

A battery cell was prepared in the same manner as in Example 1, except that charging for activation of the battery cell was performed in the range of SOC40.

<Example 4>

A battery cell was prepared in the same manner as in Example 1, except that charging for activating the battery cell was performed in the range of SOC60.

&Lt; Comparative Example 1 &

A battery cell was prepared in the same manner as in Example 1, except that charging for activating the battery cell was performed in the range of SOC10.

&Lt; Comparative Example 2 &

A battery cell was prepared in the same manner as in Example 1, except that charging for activating the battery cell was performed in the range of SOC100.

<Experimental Example 2>

1C capacities of the battery cells of Examples 1 to 3 and Comparative Examples 1 and 2 were measured, and the results are shown in Table 1 below.

<Experimental Example 3>

The battery cells of Examples 1 to 3 and Comparative Examples 1 and 2 were subjected to a current of 10 C for 10 seconds in the range of SOC50 to measure the resistance. The results are shown in Table 1 below.

division 1C Capacity (mAh) Resistance (Ohm) Example 2 10.28 1.12 Example 3 10.27 1.14 Example 4 10.16 1.16 Comparative Example 1 9.64 1.19 Comparative Example 2 9.59 1.29

As shown in Table 1, in Comparative Examples 1 and 2 in which charge and discharge for the activation of the battery cell were performed in the range of SOC20 to SOC60, and the battery cells of Examples 1 to 3 were charged / As compared with the battery cells, a large 1C capacity and a small resistance are exhibited, and it can be confirmed that more excellent electric characteristics are exhibited. In particular, in the case of Example 2 showing the most excellent characteristics, it can be seen that the potential of the negative electrode enters a flat potential of 1.5 V as shown in FIG.

This is because in the case of Comparative Examples 1 and 2 in which charging and discharging for activating the battery in the manufacturing process of the battery cell were performed in charge and discharge in the range exceeding SOC20 to SOC60 in the range of filling depth in the flat potential of the cathode, electrolytic solution decomposition reaction occurred, The decomposition reaction generates a decomposition byproduct along with the generation of the gas, and the decomposition byproduct affects the surface chemical reaction during the aging process after the charging and discharging process of the battery cell to form an unstable active material surface.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (13)

An electrode assembly including a positive electrode, a negative electrode, and a separator capable of intercalating and deintercalating lithium ions is embedded in a cell case together with an electrolyte. Charging for activating the battery in a battery cell manufacturing process is performed in a SOC (State of State) of Charge). The battery cell according to claim 1, wherein the positive electrode comprises a lithium metal oxide having a layered structure represented by the following formula (1) as a positive electrode active material:
Li _x (Ni _v Mn _w Co _y M _z ) O _{2 -te t} (1)
In this formula,
0 < = x < = 0.9, 0 &
M is at least one metal or transition metal cation of +2 to +4 oxidation numbers;
A is an anion of -1 or -2 valence. The battery cell according to claim 2, wherein the oxide of Formula 1 is a lithium metal oxide represented by Formula 2 below.
Li _x (Ni _v Mn _w Co _y ) O ₂ (2)
In the above formula, 0.8 <x? 1.3, 0? V? 0.9, 0? W? 0.9, 0? Y? 0.9, x + v + w + y + z = 2. 4. The lithium secondary battery according to claim 3, wherein the lithium metal oxide represented by Formula 2 is Li (Ni _0.4 Mn _0.3 Co _0.3 ) O ₂ or Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ Battery cell. The battery cell according to claim 1, wherein the negative electrode comprises a lithium metal oxide represented by the following formula (3) as a negative electrode active material:
Li _a M ' _b O _4c-d A _d (3)
In the above formula, M 'is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al and Zr;
a and b satisfy the relations 0.1 a 12; Is determined according to the oxidation number of M 'in the range of 0.2? B? 12;
c and d satisfy 1? c? 3; 0 &lt; = d &lt;0.6;
A is one or more of an anion of -1 or -2. The battery cell according to claim 1, wherein the lithium metal oxide represented by Formula 3 is lithium titanium oxide represented by Formula 4 below.
Li _a Ti _b O _4c (4)
In the above formula, 0.5? A? 8, 1? B? 8.5, 1? C? 3, and a + b = 3c. The battery cell according to claim 6, wherein the lithium titanium oxide is LiTi ₂ O ₄ or Li ₄ Ti ₅ O ₁₂ . The battery cell according to claim 1, wherein the filling depth range in the flat potential of the negative electrode is determined in a profile with respect to potential of the negative electrode. The battery cell according to claim 8, wherein charging and discharging are performed in the range of SOC 20 to SOC 60 when the NP ratio of the battery cell is 0.9. The battery cell according to claim 1, wherein the battery cell performing the charge / discharge for activating the cell is subjected to an aging process and then the gas is removed. A battery pack according to any one of claims 1 to 10, wherein the battery cell is mounted on the pack case. A device comprising a battery pack according to claim 11. 13. The device of claim 12, wherein the device is at least one of a notebook computer, a mobile phone, a PDP, a PMP, an MP3 player, a digital still camera (DSC), a DVR, a smart phone, a GPS system, and a camcorder, an electric vehicle, a hybrid electric vehicle, Or a power storage device.

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