KR101726855B1 - A lithium secondary battery with high performance and a battery module comprising the same - Google Patents

Abstract

The present invention relates to a secondary battery and a battery module that can be applied to an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like in parallel or in place of the lead acid battery. The lithium secondary battery cell according to the present invention exhibits a high resistance ratio and storage capacity even at a low temperature of -20 캜. Therefore, the battery module using the battery cell as a unit cell can be used as a suitable power source having a good life characteristic, low temperature performance, and safety while providing a nominal voltage suitable for a large electric device. Further, the battery cell according to the present invention is suitable for an environment in which an output of a certain level or more is required at a low temperature.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-performance lithium secondary battery and a battery module including the same as a unit battery.

The present invention relates to a lithium secondary battery having excellent performance and a battery module including the same as a unit battery. More particularly, the present invention relates to a secondary battery and a battery module that can be applied to an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like in parallel with or in place of a lead acid battery.

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, Research is being actively carried out, and some are commercialized.

The 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. The anode active material is mainly composed of a carbon-based material, and the cathode active material mainly consists of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium composite oxide and the like. Among them, LiCoO ₂ exhibits good electric conductivity, high output voltage and excellent electrode characteristics, and is a typical cathode material currently commercialized and commercially available. However, LiCoO ₂ has disadvantages of being economical and environmentally friendly due to the amount of material and material, Lt; / RTI > LiNiO ₂ is relatively inexpensive and exhibits a high discharge capacity of the battery, but it is difficult to synthesize and has a problem of thermal stability in a charged state. In addition, manganese-based electrode materials such as LiMn ₂ O ₄ and LiMnO ₂ are easy to synthesize, have a low cost, have good electrochemical discharge characteristics, and have a low environmental pollution and thus are highly applicable to active materials. However, There is a problem that the electrolyte may be decomposed due to a high operating voltage.

In addition, if a high-voltage anode is used, the electrolyte is oxidized to reach the oxidation potential. As a result, the electrolyte is oxidized, resulting in gas discharge and generation of byproducts, resulting in deterioration of battery performance and increased resistance, resulting in serious safety problems . In addition, there is a high need for a secondary battery capable of operating under high voltage conditions without causing such a problem.

It is an object of the present invention to provide a high-performance lithium secondary battery cell that can replace or be used in parallel with a lead-acid battery for an automobile, and a battery module including the battery cell. Other objects and advantages of the present invention will become apparent from the following description. It is also to be easily understood that the objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

In order to achieve the above object, the present invention provides a novel lithium secondary battery cell and a battery module including the same. The battery cell may include: a) an electrode assembly including an anode, a cathode, and a separation membrane disposed between the anode and the cathode; And a negative electrode active material, and b) an electrolytic solution, wherein the negative electrode comprises lithium titanium oxide (LTO) as a negative electrode active material, and the secondary battery cell has a resistance ratio %) Is not more than 600%.

The secondary battery cell has a capacity retention (%) of 80% or more at -20 캜. The lithium titanium oxide (LTO) is represented by the following formula (1). [Chemical Formula 1]

Li _x Ti _y O ₄

In the above formula, 0.5? X? 3, 1? Y? 2.5.

Here, the lithium titanium oxide may be Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ .

The positive electrode may include a mixture containing at least two selected from the group consisting of lithium manganese oxide, lithium manganese-composite metal oxide, and lithium nickel-manganese-cobalt oxide as the positive electrode active material.

The anode may be at least 80% by weight based on 100% by weight of the cathode active material.

The lithium manganese-complex metal oxide may be represented by the following formula (2).

(2)

Li _a Me _b Mn _2-b O _{4-ca c}

0.5? A? 1.2, 0 < b? 2.0 and 0.0? C? 4.0 in Formula 2,

Me is an element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, A is a monovalent or divalent anion.

In addition, the lithium manganese-composite metal oxide may be LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O _4, or LiNi _0.4 Mn _1.6 O ₄ .

The lithium nickel-manganese-cobalt oxide may be represented by the following formula (3).

(3)

Li _o Ni _1-pq Mn _p Co _q O _r

0.5??? 1.2, 0.15? P? 0.45, 0.15? Q? 0.45, and 1.5? R? 2.5.

Here, the lithium nickel-manganese-cobalt composite oxide may be LiNi _0.6 Mn _0.2 Co _0.2 O ₂ or LiNi _0.4 Mn _0.3 Co _0.3 O ₂ .

Also, the lithium secondary battery cell has a nominal voltage of 1.5 to 2.7V.

The present invention also provides a method of manufacturing an electrode assembly, comprising: a) an electrode assembly including a cathode, a cathode, and a separator disposed between the anode and the cathode; And b) an electrolytic solution,

The negative electrode includes lithium titanium oxide (LTO) as a negative electrode active material and has a capacity retention (%) of 80% or more at -20 캜.

The present invention also provides a method of manufacturing an electrode assembly, comprising: a) an electrode assembly including a cathode, a cathode, and a separator disposed between the anode and the cathode; And b) an electrolytic solution,

The negative electrode includes lithium-titanium oxide (LTO) as a negative electrode active material, and the positive electrode includes a positive electrode active material selected from the group consisting of lithium manganese oxide, lithium manganese-composite metal oxide, and lithium nickel-manganese- Wherein the battery cell has a nominal voltage of 1.5V to 2.7V.

Also, the present invention is a unit cell comprising 5 to 12 lithium secondary battery cells, wherein the unit battery cells include one or more lithium secondary battery cells according to any one of claims 1 to 12 And a lithium secondary battery module.

Here, the battery module satisfies a driving voltage condition of 9V to 16.2V.

Also, the present invention provides a lithium secondary battery module in which the number of unit battery cells is 5 or 6, and the unit battery cells are connected in series. Here, the number of unit battery cells is 7 to 12, and the unit battery cells are connected in a combination of serial connection and parallel connection.

The present invention also provides a device such as a battery pack including the battery module, an electric vehicle including the battery pack, a hybrid electric vehicle, and a plug-in hybrid electric vehicle.

The lithium secondary battery cell according to the present invention exhibits a high resistance ratio and storage capacity even at a low temperature of -20 캜. Therefore, the battery module using the battery cell as a unit cell can be used as a suitable power source having a good life characteristic, low temperature performance, and safety while providing a nominal voltage suitable for a large electric device. Therefore, the battery cell according to the present invention is suitable for an environment that requires a certain level of output at a low temperature.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. On the other hand, the shape, size, scale or ratio of the elements in the drawings incorporated herein can be exaggerated to emphasize a clearer description.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing a comparison between the capacity retention and the resistance increase tendency of the battery cell of Example 1 and the battery cell of Comparative Example 1 according to the battery use time. FIG.
2 is a graph showing a comparison of the capacity retention tendency of the battery cell of Example 1 and the battery cell of Comparative Example 1 in accordance with the battery operating temperature.
3 is a graph showing a comparison of the resistance ratio tendency of the battery cell of Example 1 and the battery cell of Comparative Example 1 according to the battery operating temperature.
4 and 5 schematically show one specific embodiment of the battery module according to the present invention.

The terms or words used in the present specification and claims should not be construed to be limited to ordinary or dictionary terms and the inventor shall properly define the concept of the term in order to best explain its invention The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

The present invention will now be described in detail with reference to the accompanying drawings.

BACKGROUND ART [0002] Conventional lead-acid batteries for automobiles have drawbacks of short life span and large weight as primary batteries. In order to replace it with a lithium secondary battery, it is necessary to develop a cell having a proper nominal voltage, excellent lifetime characteristics, low temperature performance and safety.

Currently, most of the lithium secondary batteries use carbon-based materials such as natural graphite and artificial graphite as negative electrode active materials. The graphite material has a reaction voltage of about 0.0 to 0.25 relative to the lithium electrode (Li + / Li) and a theoretical capacity of about 327 mAh / g. A high-capacity battery can be manufactured by composing the battery with a high voltage positive electrode having a spinel structure. However, due to the structural change of graphite due to charging and discharging, there is a disadvantage that the battery life and output characteristics are deteriorated due to volume expansion / contraction of about 10%, increase in resistance due to formation of SEI layer on the surface of the negative electrode, increase in SEI layer thickness,

A lithium secondary battery cell according to an embodiment of the present invention includes: an electrode assembly including a cathode, a cathode, and a separation membrane disposed between the anode and the cathode; And b) an electrolytic solution, and includes lithium titanium oxide (LTO) as a negative electrode active material. The lithium secondary battery cell according to the present invention is excellent in low-temperature characteristics. According to a specific embodiment, the secondary battery cell of the present invention has a resistance ratio (%) of less than 600% at -20 ° C.

The lithium secondary battery cell comprises a negative electrode, a positive electrode, and a separator interposed between the negative electrode and the positive electrode, an electrolyte impregnated in the negative electrode, the positive electrode and the separator, a battery container, and a sealing member for sealing the battery container . Such a lithium secondary battery cell is constituted by sequentially laminating a negative electrode separator film anode, winding it, and storing it in a battery container.

The lithium secondary battery cell may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the separator used and the type of the electrolyte. Depending on the shape of the battery, it can be classified into a cylindrical shape, a square shape, a coin shape, a pouch shape, and the like, and can be divided into a bulk type and a thin film type depending on the size. The structure and manufacturing method of the Y cell are well known in the art, and detailed description is omitted.

In one embodiment of the present invention, the lithium titanium oxide (LTO) is represented by the following formula (1).

[Chemical Formula 1]

Li _x Ti _y O ₄

In the above formula, 0.5? X? 3, 1? Y? 2.5.

Examples of the lithium titanium oxide represented by the formula (1) include Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ . However, the present invention is not limited thereto.

The theoretical capacity of LTO is about 175 mAh / g and the potential is 1.5 V (Li + / Li), which is somewhat higher than that of carbon-based materials such as graphite. However, there is little variation in the crystal lattice before and after charge / discharge, and the volume change due to charge and discharge is less than about 0.1%. Further, the SEI layer which increases the resistance on the surface is not formed because of high dislocation. LTO has lower capacity than graphite, but it has better lifetime characteristics than graphite due to these properties. Referring to FIG. 1, the battery cell of Example 1 using the LTO cathode has a capacity retention and a resistance increase characteristic according to the use time, as compared with the battery cell of Comparative Example 1 using the graphite negative electrode It is very good. 2 and 3 show the capacity retention and the resistance increase depending on the temperature. It can be confirmed that the low temperature characteristic of the battery cell of Example 1, which is the LTO negative electrode, is excellent. According to this aspect, the battery cell of the present invention has a capacity retention (%) of 80% or more at a temperature of -20 ° C.

According to a specific embodiment of the present invention, the LTO is in the form of secondary particles in which primary particles are agglomerated, and the secondary particles preferably have a particle diameter of less than 30 占 퐉. When the size of the particles is nanometer size, the output and lifetime characteristics are improved.

The negative electrode is prepared by coating a negative electrode current collector with a mixture of a negative electrode active material, a conductive material and a binder, followed by drying and pressing. If necessary, a filler may be further added to the mixture.

The binder serves to adhere the anode active material particles to each other and adhere the anode active material to the current collector. Representative examples include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetra But are not limited to, fluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin and nylon.

The conductive material is used for imparting conductivity to the electrode. Any conductive material may be used without causing any chemical change in the battery. Examples thereof include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black and carbon fiber; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

Corresponding to the high potential of the lithium titanium oxide, in one specific example of the present invention, the anode uses a high-voltage anode. The high-voltage anode includes a lithium manganese oxide (LMO) as a cathode active material, a lithium manganese-composite metal oxide in which a lithium manganese oxide is doped with metal, and a lithium nickel manganese cobalt oxide LNMCO), preferably a mixture of two or more thereof. More preferably, the anode is at least 80 wt%, or at least 90 wt%, or at least 95 wt%, or 100 wt%, based on 100 wt% of the cathode active material.

Specifically, the lithium manganese oxide is LiMn ₂ O ₄ . The lithium manganese oxide is excellent in structural stability, thermal stability and rate-controlling properties, and has an advantage of less SOC and temperature dependency of resistance as compared with a lithium lithium-manganese-cobalt oxide material. FIGS. 4 and 5 show patterns of resistance change during charging / discharging of 100% lithium manganese oxide anode, and FIGS. 6 and 7 show patterns of resistance change during charge / discharge of lithium cobalt oxide 100% anode. This shows that the resistance change at the lithium manganese oxide anode is small.

However, in order to compensate for the decrease in capacity due to the elution of manganese under low energy density and high temperature conditions, it is preferable to use it in combination with materials such as lithium manganese-composite metal oxide or lithium lithium-manganese-cobalt oxide.

In one specific embodiment of the present invention, the lithium manganese-complex metal oxide is represented by the following general formula (2).

(2)

Li _a Me _b Mn _2-b O _{4-ca c}

0.5? A? 1.2, 0 < b? 2.0 and 0? C? 4.0 in Formula 2,

Me is an element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, . A is a monovalent or divalent anion.

Preferably, the lithium manganese-composite metal oxide represented by the above formula (2) is one in which Me is Al, Ni or Co. Specific examples thereof include LiNi _0.5 Mn _1.5 O ₄ or LiNi _0.4 Mn _1.6 O ₄ . However, the present invention is not limited thereto.

In one specific embodiment of the present invention, the lithium nickel-manganese-cobalt oxide is represented by the following formula (3).

(3)

Li _o Ni _1-pq Mn _p Co _q O _r

0.5??? 1.2, 0.15? P? 0.45, 0.15? Q? 0.45, and 1.5? R? 2.5.

The lithium nickel-manganese-cobalt composite oxide is specifically LiNi _0.6 Mn _0.2 Co _0.2 O ₂ or LiNi _0.4 Mn _0.3 Co _0.3 O ₂ , but is not limited thereto.

The anode is prepared by applying a mixture of a cathode active material, a conductive material and a binder on a cathode 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 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.

In the anode, 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.

In the positive electrode, the binder is a component which 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 positive electrode 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.

In the anode, the filler is not particularly limited as long as it is a fibrous material that is used selectively as a component for suppressing the expansion of the anode and does not cause 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.

In one embodiment of the present invention, 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.

In the present invention, the electrolytic solution contains a lithium salt, and non-aqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes, and the like are used, but the present invention 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.

The battery cell of the present invention manufactured as described above preferably has a nominal voltage of 1.5 to 2.7V. Alternatively, the nominal voltage can be adjusted within the range of 1.5 V to 2.6 V, or 2.0 V to 2.6 V, or 2.15 V to 2.6 V.

According to another aspect of the present invention, there is provided a battery cell comprising: a) an electrode assembly including a cathode, a cathode, and a separator disposed between the anode and the cathode; And a negative electrode active material, wherein the negative electrode includes lithium titanium oxide (LTO), and the secondary battery cell has a capacity retention (%) at -20 ° C. ) Is more than 80%.

According to another aspect of the present invention, there is provided a battery cell comprising: a) an electrode assembly including a cathode, a cathode, and a separator disposed between the anode and the cathode; And b) an electrolyte solution, wherein the cathode includes lithium titanium oxide (LTO) as a negative electrode active material. According to a specific embodiment of the present invention, the positive electrode is a mixture of one or more, preferably two or more, selected from the group consisting of lithium manganese oxide, lithium manganese-composite metal oxide and lithium nickel-manganese- And the nominal voltage is 1.5V to 2.7V.

The present invention also provides a battery module including the lithium secondary battery cell as a unit cell.

The battery module of the present invention includes at least one battery cell according to the present invention and has a driving voltage of 9.0V to 16.2V. In the present invention, the one battery module is preferably a unit cell, in which five to twelve lithium secondary battery cells are mutually combined.

According to a specific embodiment of the present invention, the unit cells are of the same type or different types of lithium secondary battery cells. Herein, the term 'mutual combination' means a serial or a combination of serial and parallel. The 'homogeneous' means that the material of the cathode active material used in the lithium secondary battery cell is the same as that of the material of the anode active material, and 'heterogeneous' means that at least one material of the cathode active material and the anode active material used in the lithium secondary battery cell is different .

In an embodiment of the present invention, when the number of the unit cells is less than 7, the unit cells are all connected in series. On the other hand, when the number of unit cells in the battery module is seven or more, the unit cells are connected in a combination of serial connection and parallel connection.

Thus, a secondary battery module satisfying a driving voltage in the range of 9.0V to 16.2V can be easily constructed by combining various types of battery cells of the same or different types.

8 is a schematic view of a battery module according to a specific embodiment of the present invention.

Referring to FIG. 8, the secondary battery module 100 includes six battery cells 110 connected in series and a diode 120 provided in a forward direction of a discharging current from the terminal-side lead of the outermost battery cell. The diode 120 smoothes the flow of the current at a predetermined voltage or higher and cuts off the flow of the current at or below the voltage. Therefore, the secondary battery module including the diode can protect the battery cells from overdischarge and adjust the voltage balance between the battery cells.

9 is a schematic view showing another combination example of the secondary battery module. Referring to FIG. 9, the secondary battery module 200 has two sub-modules 230 connected in parallel, and each sub-module has five unit battery cells 210 connected in series, They are connected in a combination. Meanwhile, the sub-module 230 may include a fixed resistor or a variable resistor for controlling the amount of discharge of the secondary battery. In Fig. 9, the variable resistor R is shown as an example. The secondary battery module can secure lifetime characteristics and safety by a fixed resistor or a variable resistor.

The combination configuration of the secondary battery modules 100 and 200 shown in FIGS. 8 to 9 is only one example, and the configuration of the secondary battery module according to this combination example is not limited to the above-described example, and can be variously modified.

The present invention also provides a battery pack including the battery module according to the present invention described above.

The battery pack may be used as a power source for devices requiring high temperature stability, long cycle characteristics, and high rate characteristics. Specific examples of the device include a power tool which is powered by an electric motor and moves; 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 (Escooter); An electric golf cart; And a power storage system, but the present invention is not limited thereto.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may 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.

Example

Manufacture of lithium secondary battery cell

For each of the examples, a cathode active material, a binder, and a conductive material were prepared as shown in Table 1 below and dispersed in N-methyl-2-pyrrolidone to prepare a cathode composition. The positive electrode composition was coated on an aluminum foil, followed by drying and rolling to prepare a positive electrode. A negative electrode active material, a conductive material, and a binder were prepared as shown in Table 1 below and dispersed in N-methylpyrrolidone solvent to prepare an anode composition. Next, the negative electrode composition was coated on a copper foil, followed by drying and rolling to prepare a negative electrode. As the electrolytic solution, a mixed solution of propylene carbonate (PC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) in a mixing volume ratio of 2: 4: 4 was used in which 1.0 M LiPF ₆ was dissolved. The electrolyte was injected through the prepared positive electrode and negative electrode and a separator made of polypropylene, and then wound and compressed to prepare a lithium secondary battery.

Active material
(Component / content wt%) Conductive material
(Ingredient / content) Binder / Content
(Ingredient / content) Example 1 cathode _{Li 1.33 Ti 1.67 O 4 / 92wt} % Carbon black / 4 wt% PVDF / 4 wt% anode LiMn ₂ O _{4 /} 75.65 wt%
LiNi _0.4 Mn _0.3 Co _0.3 O ₂ /13.35 wt% Carbon black / 7 wt% PVDF / 3.5 wt% Example 2 cathode _{Li 1.33 Ti 1.67 O 4 / 92wt} % Carbon black / 4 wt% PVDF / 4 wt.% &Lt; anode LiMn ₂ O _{4 /} 44.25 wt%
LiNi _0.4 Mn _0.3 Co _0.3 O _{2 /} 44.25 wt% Carbon black / 8.0 wt% PVDF / 3.5 wt.% &Lt;

Manufacture of lithium secondary battery module

Example 1 Six lithium secondary battery unit cells (each nominal voltage 2.4V to 2.5V) prepared above were connected in series to prepare a lithium secondary battery module. In this case, the driving voltage is 10.8 to 15.6 V.

Example 2: Five lithium secondary battery unit cells (each having a nominal voltage of 2.3 to 2.25) manufactured in the above manner were connected in series to produce a submodule, and the submodules were connected in parallel to each other to manufacture a lithium secondary battery module. In this case, the driving voltage is 10.8 to 15.6 V.

Comparative Example 1

A cathode active material, a binder and a conductive material were prepared as shown in Table 2 below and dispersed in N-methyl-2-pyrrolidone to prepare a cathode composition. The positive electrode composition was coated on an aluminum foil, followed by drying and rolling to prepare a positive electrode. A negative electrode active material, a conductive material, and a binder were prepared as shown in Table 2 below and dispersed in deionized water as a solvent to prepare an anode composition. Next, the negative electrode composition was coated on a copper foil, followed by drying and rolling to prepare a negative electrode. As the electrolytic solution, a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a mixing volume of 2: 4: 4 was used and a 1.0 M LiPF ₆ solution was dissolved. The electrolyte was injected through the prepared positive electrode and negative electrode and a separator made of polypropylene, and then wound and compressed to prepare a unit cell. Four unit cells prepared above were connected in series to produce a lithium secondary battery module. In this case, the driving voltage is 11.5 to 16.8V.

Active material
(Component / content wt%) Conductive material
(Ingredient / content) Binder / Content
(Ingredient / content) Comparative Example 1 cathode Graphite / 95.8wt% Carbon black / 1 wt% SBR / 2.2 wt% anode LiNi _0.6 Mn _0.2 Co _0.2 O ₂ /88.5 wt% Carbon black / 8.5 wt% PVDF / 3.0 wt%

Comparison of charge / discharge efficiency and resistance increase rate characteristics of battery module

The battery module of Example 1 and the battery module of the comparative example were charged at a current density of 25 mA at a current density of 25 mA and a current density of 400 mAh at 25 DEG C using a charge-discharge cycle device (TOYO, model TOYO- After initial charging with -CV (Constant current-Constant voltage), the battery was discharged to 1.8V at a discharging capacity of 1000 mAh with a downtime of 10 minutes. In the comparative example, CC The charging and discharging efficiency and the resistance increase rate characteristics were compared by discharging to 2.8 V with a discharging capacity of 1000 mAh with a downtime of 10 minutes after the first charging with -CV (Constant current-Constant voltage). The results are shown in FIG. . As shown in FIG. 1, the LTO cathode according to the present invention and the lithium secondary battery manufactured using the LTO cathode exhibit excellent effects in terms of charging / discharging efficiency and resistance increase rate as compared with a battery employing a graphite cathode.

Comparison of Low Temperature Characteristics of Battery Module

The battery module of the second embodiment and the battery module of the comparative example were compared with each other in charging / discharging efficiency and resistance increase rate characteristics with temperature change using a charge / discharge cycle device (manufacturer: TOYO, model: TOYO-5200). The charge / discharge cycle of Example 1 was initially 1.8 hours at a current density of 2.6 at a charge voltage of 400 mAh at 25 DEG C, and then a rest period of 10 minutes after initial charging with a constant current-constant voltage (CC-CV) V. In the comparative example, discharging was performed to 2.8V at a discharging capacity of 1000 mAh with a dwell period of 10 minutes after the initial charging by CC-CV at a charging voltage of 4.2 V and a current density of 400 mAh at 25 캜.

2, it was confirmed that the capacity characteristics of the battery module of Example 2 were superior to those of Comparative Example even at a temperature of less than -20 ° C and an image temperature of less than 20 ° C. Especially, it was confirmed that the resistance ratio was less than 600% under the condition of -20 ° C. As can be seen from FIG. 3, the battery module according to Example 2 exhibited an excellent effect as compared with the comparative example. Especially, at a temperature of -20 ° C, the capacity retention (capacity retention (% )) Was found to be 80% or more.

10 devices
100, 200 battery module
110, 210 unit cell
120, 220 diodes
230 Sub Battery Module

Claims (20)

a) an electrode assembly including an anode, a cathode, and a separator disposed between the anode and the cathode; And b) an electrolytic solution,
The negative electrode includes lithium titanium oxide (LTO) as a negative electrode active material,
The secondary battery cell has a resistance ratio (%) of 600% or less and a capacity retention (%) of 80% or more at -20 ° C,
The positive electrode is composed of lithium manganese oxide and lithium nickel-manganese-cobalt oxide as the positive electrode active material, wherein the lithium nickel-manganese-cobalt oxide is LiNi _0.6 Mn _0.2 Co _0.2 O ₂ or LiNi _0.4 Mn _0.3 Co _0.3 O ₂ Which is a lithium secondary battery cell. delete The method according to claim 1,
The lithium secondary battery cell according to claim 1, wherein the lithium titanium oxide (LTO)
[Chemical Formula 1]
Li _x Ti _y O ₄
In the above formula, 0.5? X? 3, 1? Y? 2.5.
The method of claim 3,
Wherein the lithium titanium oxide is Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ .
delete delete delete delete delete delete The method according to claim 1,
Wherein the battery cell has a nominal voltage of 1.5V to 2.7V.
delete delete The unit cell includes five to twelve lithium secondary battery cells, and the unit battery cells include at least one lithium secondary battery cell according to any one of claims 1, 3, 4, and 11 Lithium secondary battery module.
15. The method of claim 14,
Wherein the battery module satisfies a driving voltage condition of 9V to 16.2V.
15. The method of claim 14,
Wherein the number of unit battery cells is five or six, and the unit battery cells are connected in series.
15. The method of claim 14,
Wherein the number of unit battery cells is 7 to 12, and the unit battery cells are connected by a combination of series connection and parallel connection.
A battery pack comprising the battery module according to claim 14.
A device comprising a battery pack according to claim 18.
20. The device of claim 19, wherein the device is an electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

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