KR20150027572A - Secondary Battery with High Output and Low Resistance - Google Patents

Abstract

The present invention relates to a secondary battery with a high output and a low resistance and, more specifically, to a secondary battery, in which the external resistance is 0.4-0.8 ohm in a graph of voltage drop upon time, wherein the external resistance is calculated from the average line slope in the zone where the external resistance is operated as a decisive element of the total resistance, and the average line slope in the zone where the internal resistance is operated as a decisive element of the total resistance.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a secondary battery,

More particularly, the present invention relates to a secondary battery having a high output and low resistance, and more particularly, to a secondary battery having a high output, low resistance, wherein an external resistance value obtained from an average linear slope of an interval in which the internal resistance serves as a determining element of the total resistance is 0.4 to 0.8 ohm.

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 operational potential, long cycle life, Batteries have been commercialized and widely used.

In recent years, there has been a growing interest in environmental issues, and as a result, electric vehicles (EVs) and hybrid electric vehicles (HEVs), which can replace fossil-fueled vehicles such as gasoline vehicles and diesel vehicles, And the like. Although a nickel metal hydride (Ni-MH) secondary battery is mainly used as a power source for such an electric vehicle (EV) and a hybrid electric vehicle (HEV), a lithium secondary battery having a high energy density, a high discharge voltage, Researches are actively proceeding, and therefore, the demand for a secondary battery that simultaneously satisfies the conditions of high output, high capacity, and low resistance has been continuously increased.

Generally, a lithium secondary battery has a structure in which a non-aqueous electrolyte containing a lithium salt is impregnated in an electrode assembly having a porous separator interposed between a positive electrode and a negative electrode coated with an active material on a current collector.

Lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium composite oxide and the like are used as the positive electrode active material of such a lithium secondary battery. Carbon materials are mainly used as the negative electrode active material, and silicon compounds, Use is also being considered.

However, such a lithium secondary battery has various problems such as a lack of electronic conductivity of the positive electrode active material, a decrease in adhesion of the electrode mixture to the current collector of the electrode, and the like. It is difficult to actually apply it as a power source for a vehicle (HEV) or the like.

In this connection, Korean Patent Laid-Open No. 10-2005-0113895 attempts to solve the problem of the electronic conductivity of the cathode active material by coating a conductive material having a particle diameter of 2/1000 or more of the active material on the surface of the lithium-containing compound. However, such a structure is designed by considering only the electronic conductivity of the positive electrode active material, and does not exhibit the effect of simultaneous satisfaction of high power, high capacity, and low resistance desired.

In order to improve the output characteristics of the secondary battery, various attempts have been made to add an additive to the electrolyte or to use a high-voltage positive electrode active material in order to thin the separator or improve the ion conductivity. However, It is merely designed considering only one characteristic of performance, and therefore, it is not able to exhibit characteristics that can be applied to the commercialization of actual electric vehicles and hybrid electric vehicles.

Accordingly, there is a great need for a secondary battery technology that can solve these problems fundamentally and can be used in practical electric vehicles, hybrid electric vehicles, and the like.

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 have conducted intensive research and various experiments. As described later, in the voltage drop graph over time, the average straight line of the section in which the external resistance acts as a determinant of the total resistance The present inventors have developed a secondary battery in which an external resistance value obtained from an average linear slope of a slope and an internal resistance serving as a determining element of the total resistance satisfies a range of 0.4 to 0.8 ohms, It has been confirmed that secondary batteries are provided with consistency with output and resistance to satisfy optimum conditions for medium to large-sized devices, and have completed the present invention.

Therefore, in the voltage drop graph of the secondary battery according to the present invention, the average linear slope and the internal resistance of the section in which the external resistance acts as a determining element of the total resistance are determined as the total resistance And an external resistance value obtained from an average linear slope of a section acting as an element is 0.4 to 0.8 ohm.

In order to test the performance of the secondary battery, the voltage drop rate over time is divided into two sections depending on the type of the voltage drop. One shows a steep slope from 0 to about 0.1 second, and the other shows a somewhat gentle slope after about 0.1 second.

The reason why the shape of the voltage drop is divided into two sections as described above is that the elements largely acting as the battery resistance change over time. Specifically, from 0 second to about 0.1 second, the resistance of the circuit inside the battery has a great influence on the total resistance due to self-resistance and resistance due to charge, that is, ohmic resistance and charge transfer resistance. On the other hand, after about 0.1 second, the resistance appearing outside the internal circuit of the battery, that is, the resistance due to diffusion of ions, that is, the diffusion resistance, greatly affects the overall resistance.

Accordingly, in the present invention, the interval from 0 second to 0.1 second is defined as a period in which the internal resistance acts as a determinant of the total resistance, and a period after 0.1 second is defined as a period in which the external resistance is the total resistance It is defined as a section acting as a decision element.

Using the graph of the voltage drop over time, it is possible to determine the magnitude of the internal resistance and the external resistance from the average linear slope of each section without using a separate electrochemical impedance spectroscopy (EIS).

FIG. 1 is a graph illustrating voltage drop along time according to one embodiment of the present invention in which the average linear slope of each section is shown in FIG. 1 for explaining a method of obtaining the external resistance value and the internal resistance value.

Referring to FIG. 1, the voltage drop is very sharp at about 0 second to about 0.1 second, and a steep slope is shown. This interval is an interval in which the internal resistance is applied. In the interval of about 0.1 second or less, One slope is shown, which is the section where the external resistance acts. In this case, the average linear slope of each section can be obtained. In FIG. 1, the average linear slope is represented by a red line. When the average straight slope of each section is extended, it is referred to as an intersection at one point, and the internal resistance value and the external resistance value can be obtained from these intersections.

Specifically, the internal resistance value is the y coordinate of the intersection (that is, the voltage value at that point) in the internal intercept which is encountered at 0 second when the average linear slope of the section in which the internal resistance is extended is ) Is deducted as a voltage drop value, which can be obtained by dividing the voltage drop value by the current value. Likewise, the external resistance value can be obtained by dividing the y-coordinate of the intersection by subtracting the voltage value at 10 seconds from the voltage drop value and dividing it by the current value.

On the other hand, the external resistance value and the internal resistance value measured by such a method generally show different values due to minute differences between cells having a similar configuration.

However, when the external resistance value and / or the internal resistance value is larger than a predetermined value, or when the deviation is large for each battery, it is difficult to apply to a medium and large-sized device such as a hybrid electric vehicle requiring a constant output.

The inventors of the present application have recognized such problems and have made intensive research and have found that the optimum external resistance value and internal resistance value suitable for use in a medium to large-sized device such as an electric vehicle or a hybrid electric vehicle, The combination of the battery materials was found out, and it was confirmed that the external resistance and the internal resistance appeared consistently within the optimum range.

In one specific example, the external resistance value of the secondary battery may be 0.4 to 0.8 ohm, more specifically 0.5 to 0.7 ohm, as mentioned above, and the internal resistance value may be 0.7 to 1.3 ohm , More specifically 0.8 to 1.1 < RTI ID = 0.0 > ohms. ≪ / RTI >

On the other hand, the secondary battery having the above-described average external resistance value includes a positive electrode having a positive electrode active material coated with a lithium nickel-based oxide, a positive electrode active material containing a nickel material, a conductive material and a binder coated on the positive electrode current collector; An anode in which a negative electrode mixture containing graphite or a blend of graphite and soft carbon is applied as an anode active material on an anode current collector; A separator interposed between the anode and the cathode; And an electrolytic solution.

The lithium nickel oxide may be a compound represented by the following general formula (1), wherein the nickel content is an excess of 55% or more based on the total transition metal (molar basis), so that a high capacity can be exhibited.

Li _x Ni _1-y M _y O ₂ (1)

0.9? X? 1.1, 0? Y? 0.45,

M is at least one element selected from the group consisting of Co, Mn, Zr, Si, Sn and Fe.

More specifically, the content of nickel may be 55% to 90%. When the content of nickel is less than 55%, it is difficult to expect a high capacity. On the other hand, when the content exceeds 90%, the reactivity increases and the high- It is not preferable.

In one specific example, M may be at least one transition metal selected from the group consisting of Mn and Co, and more specifically Mn _a Co _b (0.2? A? 0.3, 0.2? B Lt; = 0.3).

In one specific example, the lithium nickel based oxide may be coated with a metal or a fluorine-containing compound. At this time, the metal may be selected from the group consisting of Al, Zr, Ti and B, for example.

The average particle diameter (D50) of the lithium nickel oxide according to the present invention may be from 4 micrometers to 30 micrometers, and more specifically from 4 micrometers to 20 micrometers.

When the average particle diameter is less than 4 micrometers, the manufacturing processability is poor and the ionic conductivity is lowered. When the average particle diameter is more than 30 micrometers, the energy density and the electron conductivity of the electrode are lowered.

The conductive material is a component for further improving the conductivity of the active material, and may be contained in an amount of 2 to 15% by weight based on the total weight of the positive electrode material mixture.

If the content of the conductive material is less than 2% by weight, it is difficult to keep the conductive path and the resistance may increase. If it exceeds 15% by weight, the energy density of the electrode is lowered, Is increased and this also increases the resistance, which is not preferable.

Such a conductive material is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and includes, for example, 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. Concrete examples of commercially available conductive materials include acetylene black series such as Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, etc.), Ketjenblack, EC (Armak Company), Vulcan XC-72 (Cabot Company), and Super P (Timcal).

The binder is a component for improving the adhesion of the active material and the conductive material, and may be contained in an amount of 2 to 8% by weight based on the total weight of the positive electrode material mixture.

If the content of the binder is less than 2 wt%, the adhesive strength is very low and the mass productivity is deteriorated. If the content of the binder is more than 8 wt%, the resistance is increased.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), cellulose, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, a variety of copolymers, polymers such as polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer And high-polyvinyl alcohol.

In addition to the conductive material and the binder, other components such as a filler, a viscosity adjusting agent, and an adhesion promoter may be optionally included in the positive electrode material mixture, if necessary, or a combination of two or more thereof.

The filler is an auxiliary component for suppressing the expansion of the electrode. The filler is not particularly limited as long as it is a fibrous material without causing any 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.

The viscosity modifier may be added up to 30% by weight based on the total weight of the negative electrode mixture as a component for adjusting the viscosity of the electrode mixture so that the mixing process of the electrode mixture and the coating process on the current collector may be easy. Examples of such viscosity modifiers include carboxymethylcellulose, polyvinylidene fluoride and the like, but are not limited thereto. In some cases, the above-described solvent may play a role as a viscosity adjusting agent.

The adhesion promoter may be added in an amount of 10% by weight or less based on the binder, for example, oxalic acid, adipic acid, Formic acid, acrylic acid derivatives, itaconic acid derivatives, and the like.

The cathode current collector to which the cathode mixture is applied generally has a thickness of 3 to 500 탆. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and may be formed of a material such as stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface of aluminum or stainless steel Treated with carbon, nickel, titanium, silver or the like may be used. The positive electrode current collector may have fine unevenness formed on the surface thereof to increase the adhesive force of the positive electrode active material as in the case of the negative electrode current collector. Alternatively, the positive electrode current collector may have various properties such as a film, sheet, foil, net, porous body, Form is possible.

In one specific example, the loading amount of the positive electrode mixture applied to the positive electrode collector is 0.5 mAh / cm² To 1 mAh / cm²More specifically 0.7 mAh / cm < RTI ID = 0.0 >² To 1 mAh / cm² Lt; / RTI >

0.5 mAh / cm² , The capacity is remarkably decreased, which is undesirable, and when it is 1 mAh / cm²The resistance is increased as the electrode is thickened, which is not preferable.

On the other hand, the negative electrode active material may include graphite, such as natural graphite, having a completely layered crystal structure, or graphite having a low crystalline layered crystal structure (a structure in which hexagonal honeycomb planes of carbon are arranged in layers) May be used, wherein the soft carbon may be included in an amount of 0.001 to 50% by weight based on the total weight of the blend.

When the soft carbon is contained in an amount of more than 50% by weight, the battery capacity and the charging / discharging efficiency may be largely lowered, and the voltage flatness is not preferable.

In addition to the negative electrode active material, other components such as a conductive material and a binder may be optionally included in the negative electrode material mixture as described above in connection with the structure of the positive electrode material mixture. The binder, the conductive material, and the components added as needed are the same as those in the anode.

The negative electrode collector to which the negative electrode mixture is applied 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 conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, 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. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the negative electrode 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.

As the separator interposed between the positive electrode and the negative electrode, 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. As such a separation membrane, for example, a sheet or a nonwoven fabric made of an olefin-based polymer such as polypropylene which is chemically resistant and hydrophobic, glass fiber, polyethylene or the like is used.

In some cases, a gel polymer electrolyte may be coated on the separation membrane to increase the stability of the cell. Representative examples of such gel polymers include polyethylene oxide, polyvinylidene fluoride, and polyacrylonitrile. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The secondary battery according to the present invention can be a lithium secondary battery in detail,

The electrolytic solution may be a non-aqueous electrolyte containing a lithium salt. As the non-aqueous electrolytic solution, a non-aqueous organic solvent, an organic solid electrolyte, or an inorganic solid electrolyte may be used.

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 substance which is soluble in the non-aqueous electrolytic solution and includes, 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 non-aqueous electrolytic solution is preferably a solution containing at least one selected from the group consisting of pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride and the like are added It is possible. 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 To a mixed solvent of linear carbonate to prepare a non-aqueous electrolytic solution containing a lithium salt.

The present invention also provides a battery module including the secondary battery as a unit battery and a battery pack including the same, wherein the battery pack has a high capacity and an excellent output characteristic, a high temperature stability, a long cycle characteristic, The device can be used as a power source of the device. The device may include, for example, a power tool powered by an electric motor; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; A power storage system, and the like, but is not limited thereto, and more specifically, it may be a hybrid electric vehicle.

The battery module and the battery pack manufacturing method are well known in the art, and a detailed description thereof will be omitted.

As described above, in the secondary battery according to the present invention, in the voltage drop graph over time, the average linear slope and the internal resistance of the section in which the external resistance acts as a determining element of the total resistance By satisfying the range of the external resistance value obtained from the average straight line slope of the section acting as a determinant of total resistance from 0.4 to 0.8 ohm, it is possible to provide consistency to output and resistance, The secondary battery for a device can be effectively manufactured.

1 is a graph showing a voltage drop rate with time of a lithium secondary battery sample 1 according to Example 1 of the present invention showing an average linear slope of each section to explain a method of obtaining an external resistance value and an internal resistance value to be;
FIG. 2 is a graph showing a voltage drop of a lithium secondary battery according to Example 1 of the present invention over time; FIG.
FIG. 3 is a graph showing the voltage drop of the lithium secondary battery samples according to the second embodiment of the present invention over time; FIG.
FIG. 4 is a graph showing the voltage drop of the lithium secondary battery samples according to the third embodiment of the present invention over time; FIG.
FIG. 5 is a graph showing the voltage drop of the lithium secondary battery samples according to the fourth embodiment of the present invention over time; FIG.
FIG. 6 is a graph showing the voltage drop of the lithium secondary battery samples according to Example 5 of the present invention over time; FIG.
FIG. 7 is a graph showing the voltage drop of the lithium secondary battery samples according to Example 6 of the present invention over time; FIG.
FIG. 8 is a graph showing the voltage drop of the lithium secondary battery samples according to the seventh embodiment of the present invention over time; FIG.
FIG. 9 is a graph illustrating voltage drop of lithium secondary battery samples according to Example 8 of the present invention over time; FIG.
10 is a graph showing the voltage drop of the lithium secondary battery samples according to the ninth embodiment of the present invention with time;
FIG. 11 is a graph showing a voltage drop rate of lithium secondary battery samples according to Example 10 of the present invention over time; FIG.
12 is a graph showing the voltage drop of the lithium secondary battery samples according to Example 11 of the present invention over time;
FIG. 13 is a graph illustrating voltage drop of lithium secondary battery samples according to Example 12 of the present invention over time; FIG.
FIG. 14 is a graph showing the voltage drop of the lithium secondary battery samples according to Example 13 of the present invention over time; FIG.
15 is a graph showing a voltage drop of the lithium secondary battery samples according to Example 14 of the present invention over time;
16 is a graph showing the voltage drop of the lithium secondary battery samples according to Comparative Example 1 of the present invention over time;
17 is a graph showing the voltage drop of the lithium secondary battery samples according to Comparative Example 2 of the present invention over time;
18 is a graph showing the voltage drop of the lithium secondary battery samples according to Comparative Example 3 of the present invention over time.

Hereinafter, the present invention will be described in detail with reference to Examples and the like, but the scope of the present invention is not limited thereto.

≪ Example 1 >

The conductive material (SuperC-65) and the binder (VW753, PVdF) were coated at a thickness of 88.5 占 퐉 and a thickness of 50 占 퐉, respectively, using Li _1.04 Ni _0.55 Mn _0.2 Co _0.2 Zr _0.05 O ₂ having an average particle diameter (D50) : 8.5: 3.0, and the mixture was coated on the aluminum foil having a thickness of 20 탆 and then rolled and dried to prepare a positive electrode.

The anode mix was prepared by mixing the mixture in NMP so that the weight ratio of the anode active material (Graphite 100%): SBR: CMC = 97.0: 1.5: 1.5 was prepared. The negative electrode mixture was coated on the copper foil having a thickness of 20 탆 and rolled and dried To prepare a negative electrode.

An electrode assembly was prepared between the anode and the cathode thus prepared, and the electrode assembly was housed in a pouch-type battery case, and then LiPF ₆ 1M, ethyl carbonate (EC): dimethyl carbonate ( A non-aqueous electrolyte solution containing 1.2% by weight of vinylene carbonate (VC) and 1.0% by weight of ethylene sulfate (ESa) , And sealed to assemble the lithium secondary batteries.

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 1 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.834 0.959 115.0 Sample 2 0.829 0.954 115.1 Sample 3 0.825 0.954 115.7 Sample 4 0.820 0.952 115.5

≪ Example 2 >

The average particle diameter (D50) of a 5.8 micrometer, Al-coated Li _1.04 Ni _0.55 Mn _0.2 Co _0.2 using Zr _0.05 O ₂ as the positive electrode active material, a conductive material (SuperC-65), binder (VW753, PVdF), respectively 88.5 : 8.5: 3.0 by weight, mixed, and then coated with the positive electrode mixture on an aluminum foil having a thickness of 20 탆, followed by rolling and drying to prepare a positive electrode. In the same manner as in Example 1, lithium secondary batteries Assembled.

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 2 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.827 0.952 115.1 Sample 2 0.825 0.949 115.1 Sample 3 0.823 0.947 115.0 Sample 4 0.822 0.947 115.2

≪ Example 3 >

The conductive material (SuperC-65) and the binder (solef6020, PVdF) were doped in a thickness of 88.5 占 퐉 and a thickness of 50 占 퐉, respectively, using Li _1.04 Ni _0.55 Mn _0.2 Co _0.2 Zr _0.05 O ₂ having an average particle diameter (D50) : 8.5: 3.0 by weight, mixed, and then coated with the positive electrode mixture on an aluminum foil having a thickness of 20 탆, followed by rolling and drying to prepare a positive electrode. In the same manner as in Example 1, lithium secondary batteries Assembled.

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 3 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.828 0.959 115.8 Sample 2 0.833 0.959 115.2 Sample 3 0.835 0.959 114.8 Sample 4 0.835 0.959 114.8

<Example 4>

The conductive material (SuperC-65) and the binder (solef6020, PVdF) were doped in a thickness of 88.5 占 퐉 and a thickness of 50 占 퐉, respectively, using Li _1.04 Ni _0.55 Mn _0.2 Co _0.2 Zr _0.05 O ₂ having an average particle diameter (D50) : 8.5: 3.0, and the mixture was mixed. The positive electrode mixture was coated on an aluminum foil having a thickness of 20 탆, rolled and dried to prepare a positive electrode. LiPF ₆ 1M, propyl carbonate (PC): dimethyl carbonate , 1.2% by weight of vinylene carbonate (VC), 1.0% by weight of ethylene sulfate (ESa) and 0.5% by weight of propane sulfate (PS) in a ratio of DMC: ethyl propionate (EP) = 2: 4: A lithium secondary battery was assembled in the same manner as in Example 1, except that the lithium nonaqueous electrolyte solution was used.

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 4 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.835 0.962 115.1 Sample 2 0.835 0.965 115.5 Sample 3 0.835 0.965 115.5 Sample 4 0.820 0.947 115.5

&Lt; Example 5 >

A conductive material (SuperC-65) and a binder (solef6020, PVdF) were respectively used as a positive electrode active material, Li _1.04 Ni _0.56 Mn _0.22 Co _0.22 O ₂ coated with a fluorine-containing compound and having an average particle diameter (D50) of 10.6 micrometers The positive electrode mixture was coated on an aluminum foil having a thickness of 20 탆 and then rolled and dried to prepare a positive electrode. LiPF ₆ 1M, propyl carbonate (PC): dimethyl 1.2% by weight of vinylene carbonate (VC), 1.0% by weight of ethylene sulfate (ESa), 0.5% by weight of propane sulfate (PS) Except that the lithium nonaqueous electrolyte solution containing the nonaqueous electrolyte solution was used.

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 5 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.832 0.965 115.9 Sample 2 0.833 0.967 116.0 Sample 3 0.833 0.970 116.3 Sample 4 0.832 0.965 115.9

&Lt; Example 6 >

The average particle diameter (D50) of 10.6 micrometer, and a fluorine-containing compound coated _{Li 1.04 Ni 0.56 Mn 0.22 Co 0.22} O 2 using a positive electrode active material, and a conductive material (Denka black), binder (solef6020, PVdF), respectively 88.5 (The amount of the primary binder being 66.6% by weight and the amount of the secondary binder being 33.3% by weight), and then the anode mixture was coated on the aluminum foil having a thickness of 20 탆 and rolled and dried to prepare a positive electrode A lithium secondary battery was assembled in the same manner as in Example 1. [

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 6 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.804 0.985 122.5 Sample 2 0.805 0.985 122.3 Sample 3 0.806 0.985 122.1 Sample 4 0.812 0.992 122.2

&Lt; Example 7 >

The average particle diameter (D50) of 10.6 micrometer, and a fluorine-containing compound coated _{Li 1.04 Ni 0.56 Mn 0.22 Co 0.22} O 2 using a positive electrode active material, and a conductive material (Denka black), binder (solef6020, PVdF), respectively 88.5 (Weight ratio of primary binder: 50% and secondary binder: 50% by weight), and then the anode mixture was coated on an aluminum foil having a thickness of 20 탆, rolled and dried to obtain a positive electrode A lithium secondary battery was assembled in the same manner as in Example 1. [

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 7 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.782 0.937 119.8 Sample 2 0.779 0.937 120.2 Sample 3 0.779 0.937 120.2 Sample 4 0.774 0.934 120.7

&Lt; Example 8 >

A conductive material (SuperC-65) and a binder (solef6020, PVdF) were respectively used as a positive electrode active material, Li _1.04 Ni _0.56 Mn _0.22 Co _0.22 O ₂ coated with a fluorine-containing compound and having an average particle diameter (D50) of 10.6 micrometers The positive electrode mixture was coated on an aluminum foil having a thickness of 20 탆 and then rolled and dried to prepare a positive electrode. LiPF ₆ 1M, propyl carbonate (PC): dimethyl 1.2% by weight of vinylene carbonate (VC), 1.0% by weight of ethylene sulfate (ESa), 0.5% by weight of propane sulfate (PS) Except that the lithium nonaqueous electrolyte solution containing the nonaqueous electrolyte solution was used.

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 8 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.773 0.929 120.3 Sample 2 0.773 0.924 119.6

&Lt; Example 9 >

A conductive material (SuperC-65) and a binder (solef6020, PVdF) were respectively used as a positive electrode active material, Li _1.04 Ni _0.56 Mn _0.22 Co _0.22 O ₂ coated with a fluorine-containing compound and having an average particle diameter (D50) of 10.6 micrometers Except that the positive electrode mixture was coated on the aluminum foil having a thickness of 15 탆 and then rolled and dried to prepare a positive electrode. The lithium secondary battery according to Example 1 was produced in the same manner as in Example 1, .

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 9 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.831 0.962 115.7 Sample 2 0.831 0.962 115.7 Sample 3 0.832 0.965 115.9

&Lt; Example 10 >

A conductive material (SuperC-65) and a binder (solef6020, PVdF) were each used as a positive electrode active material, and Li _1.04 Ni _0.56 Mn _0.22 Co _0.22 O ₂ coated with a fluorine-containing compound having an average particle diameter (D50) Except that the positive electrode mixture was coated on the aluminum foil having a thickness of 15 탆 and then rolled and dried to prepare a positive electrode. The lithium secondary battery according to Example 1 was produced in the same manner as in Example 1, .

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 10 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.847 0.974 114.9 Sample 2 0.848 0.974 114.8 Sample 3 0.848 0.976 115.1 Sample 4 0.848 0.976 115.1

&Lt; Example 11 >

A conductive material (SuperC-65) and a binder (solef6020, PVdF) were each used as a positive electrode active material, and Li _1.04 Ni _0.56 Mn _0.22 Co _0.22 O ₂ coated with a fluorine-containing compound having an average particle diameter (D50) Except that the positive electrode mixture was coated on the aluminum foil having a thickness of 20 탆 and then rolled and dried to prepare a positive electrode. .

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 11 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.849 0.975 114.9 Sample 2 0.850 0.975 114.7 Sample 3 0.852 0.977 114.7 Sample 4 0.853 0.977 114.5 Sample 5 0.831 0.957 115.2 Sample 6 0.831 0.954 114.9 Sample 7 0.827 0.952 115.1 Sample 8 0.823 0.947 115.1

&Lt; Example 12 >

A conductive material (SuperC-65) and a binder (solef 6020, PVdF) were mixed at a weight ratio of 88.5: 8.5: 3.0, respectively, using Li _1.04 Ni _0.56 Mn _0.22 Co _0.22 O ₂ having an average particle diameter (D50) of 4.3 micrometers as a cathode active material. , The lithium secondary battery was assembled in the same manner as in Example 1 except that the positive electrode mixture was coated on the aluminum foil having a thickness of 20 탆 and rolled and dried to prepare a positive electrode.

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 12 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.920 1.055 114.7 Sample 2 0.920 1.058 114.9 Sample 3 0.928 1.071 115.4

&Lt; Example 13 >

A conductive material (SuperC-65) and a binder (solef 6020, PVdF) were mixed at a weight ratio of 88.5: 8.5: 3.0, respectively, using Li _1.04 Ni _0.56 Mn _0.22 Co _0.22 O ₂ having an average particle diameter (D50) of 5.8 micrometers as a cathode active material. , The lithium secondary battery was assembled in the same manner as in Example 1 except that the positive electrode mixture was coated on the aluminum foil having a thickness of 20 탆 and rolled and dried to prepare a positive electrode.

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 13 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.901 1.055 117.1 Sample 2 0.906 1.058 116.8 Sample 3 0.912 1.058 115.9 Sample 4 0.914 1.058 115.8

&Lt; Example 14 >

A conductive material (SuperC-65) and a binder (solef 6020, PVdF) were mixed at a weight ratio of 88.5: 8.5: 3.0, respectively, using Li _1.04 Ni _0.56 Mn _0.22 Co _0.22 O ₂ having an average particle diameter (D50) of 5.8 micrometers as a cathode active material. , The lithium secondary battery was assembled in the same manner as in Example 1 except that the positive electrode mixture was coated on the aluminum foil having a thickness of 20 탆 and rolled and dried to prepare a positive electrode.

At this time, the loading amounts of the positive electrode mixture and the negative electrode mixture were prepared as shown in Table 14 below.

The positive electrode mixture (mAh / cm ² ) Anode mixture (mAh / cm ² ) NP ratio Sample 1 0.920 1.055 114.8 Sample 2 0.929 1.068 115.0 Sample 3 0.936 1.081 115.5

&Lt; Comparative Example 1 &

A conductive material (Denka black) and a binder (KF1100, PVdF) were mixed at a weight ratio of 88.5: 8.5: 3.0, respectively, using Li _1.04 Ni _0.45 Mn _0.35 Co _0.2 O ₂ having an average particle diameter (D50) of 10.6 micrometers as a cathode active material. NMP and mixed. Then, the positive electrode mixture was coated on an aluminum foil having a thickness of 20 탆, rolled and dried to prepare a positive electrode.

The negative electrode material mixture was prepared by adding NMP to a weight ratio of graphite (soft carbon = 5 wt%: 95 wt%): SBR: CMC = 97.0: 1.5: 1.5, The negative electrode mixture was coated, rolled and dried to prepare a negative electrode.

At this time, the loading amount of the positive electrode mixture was 1.082 mAh / cm ² , the loading amount of the negative electrode mixture was 1.122 mAh / cm ² , and the NP ratio was 103.7.

So between the prepared cathode and the anode separator (Celgard Inc., thickness: 20 ㎛) After preparing the electrode assembly interposed therebetween and accommodating it in the pouch-shaped battery case, 0.5M LiPF _6, ethyl carbonate (EC): dimethyl carbonate A lithium nonaqueous electrolyte solution containing 2% by weight of vinylene carbonate (VC) and 2% by weight of vinylene carbonate (DMC): ethyl methyl carbonate (EMC) = 2: 4: 4 Respectively. Eight samples were prepared as described above for the accuracy of the experiment.

&Lt; Comparative Example 2 &

Li _1.04 Ni _0.56 Mn _0.22 Co _0.22 O ₂ having an average particle diameter (D50) of 10.6 micrometers and Li _1.04 Ni _0.6 Mn _0.2 Co _0.2 O ₂ having an average particle size (D50) of 10.5 micrometers as a cathode active material were _{mixed at} a weight ratio of 7: 3 Except that the loading amount of the positive electrode material mixture was 1.08 mAh / cm ² , the loading amount of the negative electrode material mixture was 1.134 mAh / cm ² , and the NP ratio was 105. In the same manner as in Comparative Example 1, The battery was assembled. Eight samples were prepared as described above for the accuracy of the experiment.

&Lt; Comparative Example 3 &

Li _1.04 Ni _1/3 Mn _1/3 Co _1/3 O ₂ having an average particle diameter (D50) of 6.9 micrometers was used as the positive electrode active material, the loading amount of the positive electrode mixture was 1.081 mAh / cm ² , the loading amount of the negative electrode mixture Of 1.124 mAh / cm &lt; ² &gt; and an NP ratio of 104, so that the lithium secondary battery was assembled. Seven samples were prepared as described above for the accuracy of the experiment.

<Experimental Example 1>

The voltage drop of the lithium secondary batteries manufactured in Examples 1 to 15 and Comparative Examples 1 to 3 over time was measured at SOC 50 and is shown in FIGS. 2 to 18.

Based on the above graphs, the internal resistance value and the external resistance value of each sample are calculated by the method disclosed in the present invention, and the results are averaged.

Internal Resistance (ohm) External Resistance (ohm) Example 1 1.052 0.650 Example 2 1.009 0.646 Example 3 0.930 0.617 Example 4 1.059 0.628 Example 5 1.038 0.625 Example 6 1.055 0.655 Example 7 1.132 0.670 Example 8 1.075 0.661 Example 9 0.942 0.581 Example 10 1.032 0.602 Example 11 1.078 0.631 Example 12 0.902 0.564 Example 13 0.839 0.539 Example 14 0.833 0.543 Comparative Example 1 1.685 0.938 Comparative Example 2 3.240 1.602 Comparative Example 3 1.710 1.020

As shown in FIGS. 2 to 18, it can be seen that the secondary batteries of Examples 1 to 14 have a small variation in each sample, while the secondary batteries of Comparative Examples 1 to 3 have large variations.

As shown in Table 1, the secondary batteries of Comparative Examples 1 to 3 had an external resistance value of 0.9 ohm or more and an internal resistance value of 1.6 ohm or more, while the secondary batteries of Examples 1 to 14 according to the present invention had external It can be seen that the resistance and the resistance are consistent between 0.4 and 0.8 ohm and the internal resistance is within 0.7 to 1.3 ohm.

From the above results, it can be seen that the secondary battery according to the present invention can be utilized as an optimum middle- or large-sized device secondary battery with high reliability in performance.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (17)

In the graph of the voltage drop over time, the average linear slope and the average linear slope of the section in which the internal resistance acts as a determinant of the total resistance in the section in which the external resistance acts as a determining element of the total resistance Wherein the external resistance value obtained from the secondary battery is 0.4 to 0.8 ohm. The secondary battery according to claim 1, wherein an internal resistance value obtained from the voltage drop graph over time is 0.7 to 1.3 ohms. The secondary battery according to claim 1,
A positive electrode having a positive electrode current collector coated with a positive electrode active material including a lithium nickel-based oxide, a conductive material, and a binder;
An anode in which a negative electrode mixture containing graphite or a blend of graphite and soft carbon is applied as an anode active material on an anode current collector;
A separator interposed between the anode and the cathode; And
Electrolytic solution;
And a secondary battery. 4. The secondary battery according to claim 3, wherein the lithium nickel oxide is represented by the following formula (1)
Li _x Ni _1-y M _y O ₂ (1)
0.9? X? 1.1, 0? Y? 0.45,
M is at least one element selected from the group consisting of Co, Mn, Zr, Si, Sn and Fe. The secondary battery according to claim 3, wherein M is Mn _a Co _b (0.2? A? 0.3, 0.2? _B ? 0.3). The secondary battery according to claim 3, wherein the lithium nickel oxide is coated with a metal or a fluorine-containing compound. 4. The secondary battery according to claim 3, wherein the conductive material is contained in an amount of 2 to 15% by weight based on the total weight of the positive electrode material mixture. The secondary battery according to claim 3, wherein the binder is contained in an amount of 2 to 8% by weight based on the total weight of the positive electrode material mixture. The secondary battery according to claim 3, wherein the lithium nickel oxide has an average particle diameter (D50) of 4 micrometers to 30 micrometers. 4. The method of claim 3, wherein the loading amount of the positive electrode mixture is 0.5 mAh / cm² To 1 mAh / cm² . &Lt; / RTI &gt; The secondary battery according to claim 3, wherein the soft carbon is contained in an amount of 0.001 to 50 wt% based on the total weight of the blend. The secondary battery according to claim 1, wherein the secondary battery is a lithium secondary battery. A battery module comprising the secondary battery according to claim 1 as a unit cell. A battery pack comprising the battery module according to claim 13. A device comprising a battery pack according to claim 14. 16. The device of claim 15, wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a system for power storage. 17. The device of claim 16, wherein the device is a hybrid electric vehicle.

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