KR101798199B1 - Lithium ion secondary battery system - Google Patents

Abstract

The present invention relates to a battery module system with excellent performance. More particularly, the present invention relates to a battery module system including an ion battery as a unit battery cell, which can be applied to a high output device such as an electric vehicle in parallel with or in place of a conventional lead acid battery. The battery module system according to the present invention has a superior resistance ratio and storage capacity even at a low temperature. Thus, a battery module system can be used as a suitable power source with good life characteristics, low temperature performance and safety while providing a nominal voltage suitable for large electrical devices. Further, the battery module system 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

TECHNICAL FIELD [0001] The present invention relates to a lithium ion secondary battery system,

The present invention relates to a battery module system with excellent performance. More particularly, the present invention relates to a battery module system including a lithium ion secondary battery as a unit battery cell, which can be applied to a high output device such as an electric vehicle in parallel with or in place of a conventional 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.

An object of the present invention is to provide a battery module system having high performance and high output characteristics as well as being excellent in low temperature and long life characteristics which can be used instead of or in combination with existing lead acid batteries for automobiles. 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.

The present invention provides a novel battery module system for solving the above problems. Wherein the battery module system comprises a lithium ion secondary battery cell of the same type or different type and the anode of the lithium ion secondary battery cell comprises lithium manganese oxide (LMO) and lithium nickel-manganese-cobalt oxide (LNMCO).

The battery module system may have a driving voltage of 9V to 16.2V.

The lithium nickel-manganese-cobalt oxide may be represented by the following general formula (1). [Chemical Formula 1]

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

0.5? O? 1.2, 0.15? P? 0.45, 0.15? Q? 1.45, and 1.5? R? 2.5.

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 .

The battery module system may include 5 to 12 unit cell cells.

In addition, the number of unit battery cells may be 5 or 7, and the anode of the lithium secondary battery cell may have lithium manganese oxide of 50 wt% or more with respect to 100 wt% of the cathode active material.

In the battery module system, the number of unit battery cells is 7 to 12, and the positive electrode of the lithium secondary battery cell may have lithium nickel-manganese-cobalt oxide of 50 wt% or more with respect to 100 wt% of the positive electrode active material.

In the battery module system, the number of unit battery cells is 5 or 6, and the unit battery cells are connected in series.

In the battery module system, the number of unit battery cells is 7 to 12, and the battery cells are connected by a combination of serial connection and parallel connection.

The battery cell has a nominal voltage range of 1.5 V to 2.7 V.

Further, the positive electrode may further include a lithium manganese-composite metal oxide as a positive electrode 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}

In Formula 2, 0.5? A? 1.2, 0 <b? 2.0 and 0? C? 4.0, and Me is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, , Nb, Mo, Sr, Sb, W, Ti and Bi, and A is a monovalent or divalent anion.

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 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 b) an electrolytic solution, wherein the cathode may include lithium titanium oxide (LTO).

The lithium titanium oxide may be represented by the following formula (3).

(3)

Li _x Ti _y O ₄

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

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

In addition, the present invention provides a battery pack including the battery module system and a device including the battery pack, which provide an electric vehicle, a hybrid electric vehicle, and a plug-in hybrid electric vehicle.

The battery module system according to the present invention has a superior resistance ratio and storage capacity even at a low temperature. Thus, a battery module system can be used as a suitable power source with good life characteristics, low temperature performance and safety while providing a nominal voltage suitable for large electrical devices. Further, the battery module system 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.

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.
FIG. 1 schematically shows a driving voltage range of a lithium ion secondary battery system and a lead acid battery system.
FIG. 2 is a graph showing the unit capacitance and the voltage range of the lithium manganese oxide.
FIG. 3 is a graph showing the unit capacitance and the voltage range of lithium nickel-manganese-cobalt oxide.
FIG. 4 shows a change in voltage profile according to the mixing ratio of lithium manganese oxide and lithium nickel-manganese-cobalt oxide.
FIG. 5 is a graph plotting the OCV curve according to the mixing ratio of lithium manganese oxide and lithium nickel-manganese-cobalt oxide.
6 and 7 schematically illustrate one specific embodiment of the battery module system according to the present invention.
8 is a graph showing the tendency of charging / discharging efficiency and resistance increase rate of Example 1 and Comparative Example 1 of 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.

Conventionally, lead-acid batteries for automobiles have short life span and large weight as primary batteries. The lead-acid battery has a general life span of 5 years or less and has a disadvantage in that the performance is significantly lowered if a complete discharge is performed due to self-discharge. Accordingly, there is a growing interest in a battery module system using a lithium ion secondary battery as a power supply system for replacing a lead-acid battery. In order to replace a lead-acid battery with a lithium secondary battery, it is necessary to develop a cell having a proper nominal voltage, excellent lifespan characteristics, low temperature performance and safety.

Accordingly, the present invention provides a battery module system that can replace or be used in parallel with a lead acid battery, which is a power supply system used in a high output device. The battery module system includes a lithium ion secondary battery cell of the same kind or different type, and the positive electrode of the lithium ion secondary battery includes lithium manganese oxide (LMO) and lithium nickel-manganese-cobalt oxide LNMCO). &Lt; / RTI &gt;

Here, 'homogeneous' means that the materials of the cathode active material and the anode active material used in the lithium secondary battery cell are the same as those of the anode active material, and 'heterogeneous' means that at least one of the cathode active material and the anode active material used in the lithium secondary battery cell is different .

In a specific embodiment of the present invention, the battery module system is preferably a unit cell, in which 5 to 12 lithium secondary battery cells are combined with each other. Herein, the term 'mutual combination' means a serial or a combination of serial and parallel.

Figure 1 is a schematic diagram of a 12V system. The voltage of a conventional lead-acid battery shows about 12.8V when fully charged. To replace or use with a lithium-ion secondary battery, the battery system must be designed to have an appropriate voltage in the range of about 10 V to 15 V. In consideration of this aspect, the module system according to the present invention has a driving voltage of 9.0V to 16.2V.

In order to realize such a driving voltage, the battery cell of the battery module system of the present invention uses a positive electrode comprising a mixture of lithium manganese oxide (LMO) and lithium nickel-manganese-cobalt oxide (LNMCO) as a positive electrode active material. The mixture is 80% or more, or 90% or more, or 95% or more, or 99% or more of 100 weight% of the cathode active material. FIG. 2 is a graph showing the voltage profile of the LMO, and FIG. 3 is a graph showing the voltage profile of the LNMCO. Lithium manganese oxide is excellent in structural stability, thermal stability, and rate-limiting properties, and has a lower resistance SOC and temperature dependency than lithium lithium-manganese-cobalt oxide material. 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.

LMO has a lower electric capacity than LNMCO but has a voltage range of approximately 3.8V to 4.2V. On the other hand, LNMCO exhibits a minimum voltage range of approximately 3.6V. Therefore, the composite anode in which LNMCO and LMO are mixed has various voltage curves as shown in FIG. 4 according to the mixing ratio. Therefore, when a battery is manufactured by selecting an appropriate mixing ratio of the positive electrode active material in the composite positive electrode, a desired driving voltage can be effectively achieved.

In one specific embodiment of the present invention, the lithium manganese oxide is not limited to LiMn ₂ O ₄ , but is not limited thereto.

In one specific embodiment of the present invention, the lithium nickel-manganese-cobalt oxide is represented by the following formula (1).

[Chemical Formula 1]

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

0.5? O? 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.

To replace lead acid batteries, low-temperature performance is required in lithium batteries and it is advantageous to increase the LMO ratio in the mixed anode. The higher the ratio of LMO, the higher the nominal voltage of the cell. When used in combination with a lead-acid battery, lithium batteries generally require more charging performance. Therefore, it is advantageous to increase the ratio of LNMCO in the mixed anode considering the characteristics of the material and the voltage profile.

In this respect, in the battery module system according to the present invention, the number of unit battery cells may be 5 or 6, and when the number of unit battery cells is less than 7, all the unit cell cells are connected in series desirable.

In one specific embodiment of the present invention, the number of unit cells in the battery module system may be 7 to 12. When the number of unit battery cells is 7 or more, the unit battery cells may be connected in series and in parallel Connections are made by combining.

6 is a schematic diagram of a battery module system according to one specific embodiment of the present invention. Referring to FIG. 6, the secondary battery module system 100 includes six battery cells 110 connected in series, and a diode 120 provided in a forward direction of a discharging current at 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. Thus, the module system with the diode can protect the battery cells from overdischarge and balance the voltage between the battery cells.

7 is a schematic view showing another combination example of the secondary battery module system. 7, in the battery module system 200, two sub modules 230 are 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. 7, the variable resistor R is shown as an example. The battery module system can secure lifetime characteristics and safety by a fixed resistance or a variable resistance.

6 to 7 are merely examples, and the configuration of the battery module system according to this combination example is not limited to the above-described example, and the configuration of the battery module system according to this combination example is not limited to the configuration suitable for implementing a desired driving voltage .

In one specific embodiment of the present invention, the positive electrode of the battery cell of the present invention may further include a lithium manganese-composite metal oxide as a positive electrode active material. 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}

Wherein Me is at least one 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, Ti and Bi. A is a monovalent or divalent anion.

Preferably, the lithium manganese-composite metal oxide represented by Formula 2 is Me in which Ni is Ni. Specific examples thereof include LiNi _0.5 Mn _1.5 O ₄ or LiNi _0.4 Mn _1.6 O ₄ , but the present invention 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 above-mentioned cathode active material in the anode includes not less than 85% by weight, preferably not less than 90% by weight based on the total weight of the mixture including the cathode active material. 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.

In the anode, the conductive material is usually added in an amount of 0.1 to 50% by weight, preferably 10% by weight or less, 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 that assists in binding of the active material to the conductive material and bonding to the current collector, and is usually 0.1 to 20% by weight, preferably 7 to less than 7% by weight based on the total weight of the mixture including the positive electrode active material Lt; / RTI &gt; 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 specific embodiment of the present invention, the negative electrode of the battery cell includes lithium titanium oxide (LTO) as a negative electrode active material. The lithium titanium oxide is 80% or more, or 90% or more, or 95% or more, or 99% or more of 100 wt% of the negative electrode active material. Typically, a carbon-based material such as graphite is used as a negative electrode active material in a lithium ion secondary battery. In such a carbon-based negative electrode, a performance degradation similar to that of a lead-acid battery may be caused. On the other hand, LTO is excellent in lifetime characteristics due to structural stability and charging performance at low temperature. Accordingly, when the above-described cathode material and the battery are constituted, the nominal voltage of the unit cell can be adjusted within the range of 1.5V to 2.7V, 1.5V to 2.6V, 2.0V to 2.6V, or 2.15V to 2.6V (See FIG. 4). In addition, when five to six unit cells are connected in series to each other, the nominal voltage of the battery module system can be appropriately set between about 10 V and 15 V as shown in FIG. As described above, the battery module system according to the present invention can constitute a system by connecting the battery cells in series and parallel in various combinations according to the capacity and product requirements of the unit cells.

The negative electrode includes lithium-titanium oxide (LTO) as a negative electrode active material. The lithium titanium oxide (LTO) is represented by the following formula (3).

(3)

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 Formula 3 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.

According to a specific embodiment of the present invention, 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.

Next, a method of manufacturing the lithium ion secondary battery cell will be described.

The lithium secondary battery cell includes a cathode, an anode, a separator interposed between the cathode and the anode, an electrolyte impregnated in the anode, the anode and the separator, a battery container, and a sealing member sealing the battery container have. 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 these batteries are well known in the art, and detailed description thereof will be omitted.

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 present invention also provides a battery pack including the battery module system according to the present invention. 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 can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

Example: Preparation 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, followed by winding and pressing to prepare a lithium secondary battery cell.

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;

Example: Preparation of lithium secondary battery module

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

Example 2: Five lithium secondary battery cells (each nominal voltage of 2.25 V to 2.3 V) manufactured in the above-described 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 11.5V 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 V and a charging voltage of 2.6 V at a current density of 400 mAh using a charge-discharge cycle device (manufacturer: TOYO, model: TOYO-5200) (Constant current-constant voltage), discharging to 1.8V at a discharging capacity of 1000 mAh with a downtime of 10 minutes after the initial charging. The comparative example was repeated at 25 ° C, 4.2 V charging voltage, 400 mAh The capacity reduction and the resistance increase rate characteristics of the battery were compared by repeating experiments in which the battery was discharged at a current density of 2.8 V at a discharging capacity of 1000 mAh after the initial charging with the CC-CV for the initial charging period of 10 minutes. The results are shown. As shown in FIG. 8, the LTO cathode according to the present invention and the lithium secondary battery produced using the LTO cathode according to the present invention are superior to the battery using the graphite anode in terms of life span and resistance increase rate.

10 devices
100, 200 Battery module system
110, 210 unit cell
120, 220 diodes
230 submodules

Claims (19)

Wherein the positive electrode of the lithium ion secondary battery cell comprises lithium manganese oxide (LMO) and lithium nickel-manganese-cobalt oxide (LNMCO) as a positive electrode active material, the lithium ion secondary battery cell comprising a lithium ion secondary battery cell of the same type or different type, ), And the negative electrode is a battery module system comprising lithium titanium oxide (LTO) represented by the following formula (3)
Here, the battery module system has a driving voltage of 9V to 16.2V, and includes 5 to 12 unit cell cells,
In the battery module system, when the number of unit battery cells is 5 or 7, the positive electrode of the lithium secondary battery cell has lithium manganese oxide of 50 wt% or more and the number of unit battery cells is 7 The lithium-nickel-manganese-cobalt oxide is at least 50% by weight based on 100% by weight of the cathode active material,
Wherein the battery cell has a nominal voltage ranging from 1.5V to 2.7V.
(3)
Li _x Ti _y O ₄
In the above formula, 0.5? X? 3, 1? Y? 2.5.
delete The method according to claim 1,
Wherein the lithium nickel-manganese-cobalt oxide is represented by the following Formula 1:
[Chemical Formula 1]
Li _o Ni _1-pq Mn _p Co _q O _r
0.5? O? 1.2, 0.15? P? 0.45, 0.15? Q? 1.45, and 1.5? R? 2.5.
The method according to claim 1,
Wherein the lithium nickel-manganese-cobalt composite 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 .
delete delete delete The method according to claim 1,
Wherein the battery module system has five or six unit battery cells, and the unit battery cells are connected in series.
The method according to claim 1,
Wherein the number of unit battery cells is seven to twelve, and the battery cells are connected by a combination of serial connection and parallel connection.
delete The method according to claim 1,
Wherein the positive electrode further comprises a lithium manganese-composite metal oxide as a positive electrode active material.
12. The method of claim 11,
Wherein the lithium manganese-metal composite oxide is represented by the following formula (2):
(2)
Li _a Me _b Mn _2-b O _{4-ca c}
In Formula 2, 0.5? A? 1.2, 0 <b? 2.0 and 0? C? 4.0, and Me is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, , Nb, Mo, Sr, Sb, W, Ti and Bi, and A is a monovalent or divalent anion.
12. The method of claim 11,
Wherein the lithium manganese-composite metal oxide is LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O _4, or LiNi _0.4 Mn _1.6 O ₄ .
delete delete The method according to claim 1,
Wherein the lithium titanium oxide is Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ .
A battery pack comprising a battery module system according to any one of claims 1, 3, 4, 8, 9, 11, 12, 13,
A device comprising a battery pack according to claim 17.
19. The method of claim 18,
Wherein the device is an electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

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