KR101752864B1 - Lithium Secondary Battery and Battery Module Comprising the Same - Google Patents

Abstract

The present invention relates to a lithium secondary battery optimized for configuring a dual system together with a lead acid battery in a 12V dual battery pack, and a battery module including the lithium secondary battery, wherein the battery module has excellent performance and easiness of SOC prediction.

Description

Technical Field [0001] The present invention relates to a lithium secondary battery and a battery module including the lithium secondary battery.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lithium secondary battery and a battery module including the lithium secondary battery. More particularly, the present invention relates to a lithium secondary battery optimized for a dual system together with a lead acid battery in a 12V dual battery pack and a battery module including the same.

2. Description of the Related Art In recent years, lithium secondary batteries have been used in many fields including portable electronic devices such as mobile phones, PDAs, and laptop computers. Especially, as the interest in environmental problems grows, it is one of the main causes of air pollution. As a driving source of electric vehicles that can replace fossil fuel vehicles such as gasoline vehicles and diesel vehicles, lithium secondary batteries having high energy density and discharge voltage Research on batteries has been actively conducted, and some of them are in the commercialization stage.

The lead acid battery used in the vehicle is charged through fuel consumption. In the 12V Dual System, this charging process is replaced by the energy obtained during the regenerative braking process to help improve fuel efficiency. At this time, one of the two 12V battery modules discharges the energy obtained from the charging process to another 12V battery module, and the energy-receiving 12V battery module is used as electric energy in the vehicle interior electric system.

In the case where the lithium secondary battery module constitutes a 12V dual battery pack, depending on the constitution of the active material constituting the lithium secondary battery module, the safety, the charging characteristic, the low temperature performance, the ease of prediction of the state of charge (SOC) Characteristics can be influenced. For example, a lithium secondary battery using an electrode composed of an NMC (Nickel Manganese Cobalt) cathode active material / graphite (Gr) anode active material, an LCO (lithium cobalt oxide) cathode active material / graphite anode active material, ) Is about 3.7 V. Thus, a battery module constituted by arranging four lithium secondary batteries in series (4S) has a nominal voltage of about 14.8 V, which is very disadvantageous for charging the regenerative braking energy. In addition, since the battery module constructed with three lithium secondary batteries in series (3S) has a nominal voltage of about 11.1 V and operates at a potential lower than that of the lead battery, which is another battery module constituting the 12V dual system, There is a problem that the discharge to the battery becomes disadvantageous.

The present invention relates to a lithium secondary battery optimized for constituting a dual system together with a lead acid battery in a 12V dual battery pack and a battery module including the lithium secondary battery and a lithium secondary battery excellent in charging characteristics, .

According to an embodiment of the present invention, there is provided a lithium secondary battery comprising a positive electrode comprising a three-component lithium-containing metal oxide as a positive electrode active material and a lithium electrode including a negative electrode containing a lithium titanium oxide (LTO) A secondary battery is provided.

The cathode active material may be represented by the following Formula 1:

[Chemical Formula 1]

Li _{1 + a} Ni _x Co _y Mn _1-xy O ₂

In the above, 0? A <0.5, 0 <x <1, 0 <y <0.5.

In addition, the cathode active material may be represented by the following formula (1a).

[Formula 1a]

Li _{1 + a} Ni _x Co _y Mn _1-xy M _? O ₂

Wherein M is at least one element selected from the group consisting of B, Li, Mg, Al, Ca, Sr, Cr, V, Ti, Fe, At least one metal selected from the group consisting of Co, Ni, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo and W and combinations thereof.

In addition, the negative electrode active material may be represented by the following formula (2)

(2)

Li _a Ti _b O ₄

In the above, 0.5? A? 3, 1? B? 2.5.

In addition, the negative electrode active material may be represented by the following formula (2a)

(2a)

Li _a Ti _b M _x O ₄

Wherein M is at least one element selected from the group consisting of Mo, W, Zr, Hf, Mn, Fe, Co, Ni, Zn, Al and Mg, 2.5, 0? X? 1.

Another embodiment of the present invention provides a lithium secondary battery module in which six lithium secondary batteries are connected in series.

In another embodiment of the present invention, a 12V battery pack including the lithium secondary battery module is provided.

The 12V battery pack may further include a 12V lead acid battery.

The lithium rechargeable battery module according to an embodiment of the present invention maintains a potential higher than the OCV (Open Circuit Voltage) of the lead-acid battery over the entire range of the SOC when used together with the lead-acid battery in the 12V dual battery pack, a discharge at the same time to facilitate dual 12V battery pack of V _max (typically 14V ~ 16V) and has a voltage of 16V ~ 11V range to receive the regenerative braking energy at a voltage less than.

Further, in the lithium secondary battery module according to one embodiment of the present invention, it is easy to predict the SOC.

FIG. 1 is a graph showing voltages according to SOC ranges of the lithium secondary battery module manufactured in Example 1-2, Comparative Example 1-2, and Comparative Example 2-2.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

According to one embodiment of the present invention, a lithium secondary battery module for a 12V dual battery pack comprises a cathode comprising a three-component lithium-containing metal oxide as a cathode active material and a cathode including a lithium-titanium oxide (LTO) And six lithium secondary batteries are connected in series.

First, a lithium secondary battery according to an embodiment of the present invention will be described in more detail.

The three-component lithium-containing metal oxide which can be used as the cathode active material in the present invention can be represented by the following formula (1)

[Chemical Formula 1]

Li _{1 + a} Ni _x Co _y Mn _1-xy O ₂

In the above, 0? A <0.5, 0 <x <1, 0 <y <0.5.

The compound of Formula 1 may contain a trace amount of impurities. In this case, the compound of Formula 1 may be represented as follows.

[Formula 1a]

Li _{1 + a} Ni _x Co _y Mn _1-xy M _? O ₂

Wherein M is at least one element selected from the group consisting of B, Li, Mg, Al, Ca, Sr, Cr, V, Ti, Fe, At least one metal selected from the group consisting of Co, Ni, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo and W and combinations thereof.

Preferably, the three-component lithium-containing metal oxide represented by Formula 1 is Li _{1 + a} Ni _x Co _y Mn _1-xy O ₂ (0? A <0.2, 0 <x <0.8, 0 <y <0.5), and more preferably Li _{1 + a} Ni _1/3 Co _1/3 Mn _1/3 O ₂ (0? A <0.2) where x = y = _1/3 .

In addition to the lithium nickel manganese composite oxide (LMN), the cathode active material may include, but not limited to, a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 -x} O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide expressed by the formula LiNi _1-x M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); Formula _{LiMn 2-x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like may be used together insofar as they meet the object of the present invention.

The lithium titanium oxide used as the negative electrode active material may be represented by the following formula (2).

(2)

Li _a Ti _b O ₄

In the above formula, 0.5? A? 3, 1? B? 2.5.

Alternatively, the lithium titanium oxide may be represented by the following formula (2a).

(2a)

Li _a Ti _b M _x O ₄

Wherein M is at least one element selected from the group consisting of Mo, W, Zr, Hf, Mn, Fe, Co, Ni, Zn, Al and Mg, 2.5, 0? X? 1.

Specific examples thereof include a LTO compound in which Li _0.8 Ti _2.2 O ₄ , Li _2.67 Ti _1.33 O ₄ , LiTi ₂ O ₄ , Li _1.33 Ti _1.67 O ₄ , Li _1.14 Ti _1.71 O ₄ , or Zr is incorporated. It is not. The spinel structure of Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ exhibits less change in crystal structure and excellent reversibility when charged and discharged.

The negative electrode active material may include, in addition to lithium titanium oxide (LTO), carbon such as non-graphitized carbon or graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1-x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 &lt; x &lt; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4 , and Bi ₂ O ₅ and the like; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide, and the like may be used together within the scope of the object of the present invention.

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 positive electrode current collector is generally made to have a thickness of 3 to 500 μm. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the positive electrode current collector may be made of 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 current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The conductive material is usually added in an amount of 1 to 50 wt% based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 50 wt% based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is 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 a chemical change in the battery, and examples thereof include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

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

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

The separator is interposed between the positive electrode and the negative electrode, 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. As such a separator, for example, an olefin-based polymer such as polypropylene having chemical resistance and hydrophobicity; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like can be used. In addition, a separator (for example, SRS ^R separator) in which a porous coating layer made of inorganic particles is formed on at least one surface of the porous polymer, and an engineering plastic separator , But is not limited thereto. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

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 organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, Ethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, Methylenebisphenylacetate, methylenebisphenylacetate, methylenebisphenylacetate, methylenebisphenylacetate, tricresyldicarboxylate, tricresylphosphate, tricresylphosphate, tricresyl phosphate, tricresyl phosphate, tricresyl phosphate, Ethylenic organic solvents such as ethyl acetate may be used.

The organic solid electrolyte includes, for example, 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 acid 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 , Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS _2, and the like can be used.

The lithium salt is a substance which is easily dissolved 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 carboxylate lithium, lithium tetraphenylborate, 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) A lithium salt of _2, and so on, highly dielectric solvent of ethylene carbonate (EC) or a cyclic carbonate and a low viscosity of propylene carbonate (PC) Fig. To a mixed solvent of a linear carbonate of diethyl carbonate (DEC), dimethyl carbonate (DMC) or ethyl methyl carbonate (EMC) as a solvent, to prepare a lithium salt-containing nonaqueous electrolyte.

The present invention also provides a lithium secondary battery module for a 12V dual battery pack in which six of the lithium secondary batteries are connected in series, wherein the lithium secondary battery module according to the present invention is characterized in that the charging of the regenerative braking energy and the operation at a higher potential than the lead accumulator battery .

Particularly, when graphite is used as a negative electrode active material in a conventional lithium secondary battery module, a voltage is formed near 0 V when graphite is charged to a certain extent, and a positive active material of lithium iron phosphate (LFP) It is very difficult to measure the SOC in the BMS (Battery Management System). For example, OCV is 3.29 V at SOC60 and 3.29 V at SOC50, so it is difficult to predict SOC because there is almost no change in OCV. This difficulty is further exacerbated by the voltage sensor error within the battery pack.

On the contrary, the lithium secondary battery module for a 12V dual battery pack according to an embodiment of the present invention is a three-component lithium-containing metal oxide (NMC) used as a cathode active material even though lithium titanium oxide used as a negative electrode active material has a flat potential. The voltage curve of the full cell is not smooth. Therefore, it is much more advantageous to predict the SOC from the OCV than the case of using the lithium phosphate-based (LFP) cathode active material / graphite anode active material .

In addition, when the NMC positive electrode active material / graphite negative electrode active material is used for the 12V dual battery pack, the voltage curve is not suitable and must be connected to the lead wire by a separate DC-DC converter. LTO 6S configuration, battery packs can be configured without a DC-DC converter, which is advantageous in terms of price competitiveness.

In another embodiment of the present invention, a 12V dual battery pack including the lithium secondary battery module is provided, and the battery pack can be used as a power source for a device such as a vehicle.

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.

Hereinafter, examples of the present invention will be described. The following examples are merely examples of the present invention, and thus the present invention is not limited thereto.

Example 1-1: Preparation of lithium secondary battery

An NMC compound (LiNi _0.4 Mn _0.3 Co _0.3 O ₂ ) as a cathode active material, polyvinylidene fluoride (PVDF) as a binder, acetylene black as an electroconductive material and activated carbon were mixed and dispersed in N-methyl-2-pyrrolidone To prepare a positive electrode slurry composition. The positive electrode slurry composition was applied to an aluminum foil, followed by drying and rolling to prepare a positive electrode.

Lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) as an anode active material, acetylene black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were dispersed in an N-methylpyrrolidone solvent to prepare an anode slurry composition. Subsequently, the negative electrode slurry composition was coated on the 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 ratio of 3: 3: 4 was used and a solution of LiPF ₆ of 1.15 M was dissolved.

The prepared positive electrode and negative electrode were designed to have an NP ratio of 80, and a polyethylene separator was interposed between the positive electrode and the negative electrode, and the electrolyte was injected thereinto, followed by winding and pressing to produce a middle- or large-sized lithium secondary battery.

Example 1-2: Preparation of lithium secondary battery module

Six large-sized lithium secondary batteries manufactured in Example 1-1 were connected in series to produce a lithium secondary battery module for a 12V dual battery pack.

Comparative Example 1-1: Preparation of lithium secondary battery

A lithium _secondary battery was produced in the same manner as in Example 1-1, except that LiMn ₂ O ₄ was used as the cathode active material.

Comparative Example 1-2: Preparation of lithium secondary battery module

Five large-sized lithium secondary batteries manufactured in Comparative Example 1-1 were connected in series to produce a lithium secondary battery module for a 12V dual battery pack.

Comparative Example 2-1: Preparation of lithium secondary battery

A lithium secondary battery was produced in the same manner as in Example 1-1, except that LiFePO ₄ was used as the cathode active material and graphite was used as the anode active material.

Comparative Example 2-2: Preparation of lithium secondary battery module

Four middle- and large-sized lithium secondary batteries manufactured in Comparative Example 2-1 were connected in series to manufacture a lithium secondary battery module for a 12V dual battery pack.

Evaluation example: Voltage measurement

The voltage of the lithium secondary battery module manufactured in Example 1-2, Comparative Example 1-2, and Comparative Example 2-2 was measured according to SOC change, and the result is shown in FIG.

Referring to FIG. 1, the lithium secondary battery module of Example 1-2 exhibited a voltage ranging from 12 to 16 V with a constant slope over the entire SOC range.

On the contrary, the lithium secondary battery module of Comparative Example 1-2 has a lower voltage than the lithium secondary battery module of Embodiment 1-2, so that the lithium battery voltage is driven above the lead battery SOC100 voltage (approximately 12.8 V) It does not meet the conditions that must be met. Diarrhea, Comparative Example 1-2 Even though six lithium secondary batteries are used in the lithium secondary battery module, in this case, the voltage becomes too high, so that it is not suitable as a battery module for a 12V dual battery pack.

In addition, the lithium secondary battery module of Comparative Example 2-2 exhibited a flat voltage over the SOC range, and unlike the lithium secondary battery module of Example 1-2, the SOC prediction in the BMS (Battery Management System) Respectively.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

Claims (6)

12V lead acid battery and a lithium secondary battery module,
In the lithium secondary battery module, six lithium secondary batteries are connected in series,
The lithium secondary battery includes a positive electrode active material represented by the following formula (1a) and a negative active material represented by the following formula (2a)
Wherein the lithium secondary battery module has a voltage of 11 to 16 V,
[Formula 1a]
Li _{1 + a} Ni _x Co _y Mn _1-xy M _? O ₂
Wherein M is at least one element selected from the group consisting of B, Li, Mg, Al, Ca, Sr, Cr, V, Ti, Fe, At least one metal selected from the group consisting of Co, Ni, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W and combinations thereof;
(2a)
Li _a Ti _b M _x O ₄
M is at least one element selected from the group consisting of B, Li, Mg, Al, Ca, Sr, Cr, V, Ti, Fe, Co, Ni, Zr, Zn, Si, Y, Nb, Ga, , 0.5? A? 3, 1? B? 2.5, and 0? X? 1.
The method according to claim 1,
And the voltage of the lithium secondary battery is driven above the voltage of the lead-acid battery SOC100.
The method according to claim 1,
Wherein the positive electrode and the negative electrode constituting the lithium secondary battery have an NP ratio of 80.
The method according to claim 1,
SOC in the whole range, a lithium secondary battery module is 12V battery pack, characterized in that with the regenerative braking energy at a voltage lower than the V _max of the 12V battery pack while maintaining a high potential state than the lead-acid battery OCV (Open Circuit Volatage).
5. The method of claim 4,
And the V _max is 14 to 16V.
The method according to claim 1,
12V battery pack without DC-DC converter.

Images