KR101882286B1 - Battery Pack Having Voltage Valancing Syetem - Google Patents

Abstract

The present invention relates to a battery pack including a voltage balancing system, comprising: unit modules each having one or two or more battery cells as unit cells; A battery management system (BMS) for monitoring and controlling the operation of the battery pack; A voltage balancing device included in the BMS and performing charge or discharge of each unit module by a control signal from the BMS; And a DC / DC converter (direct current converter) for applying the power of the unit modules to the BMS; And a battery pack.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery pack having a voltage balancing system,

The present invention relates to a battery pack including a voltage balancing system.

BACKGROUND ART [0002] In recent years, rechargeable secondary batteries have been extensively used as an energy source or an auxiliary power device for wireless mobile devices. In addition, the secondary battery is an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (HEV), and the like, which are proposed as solutions for air pollution of existing gasoline vehicles and diesel vehicles using fossil fuels (Plug-In HEV) and the like.

Such a secondary battery is used in various mobile devices requiring a high output. For this purpose, a battery used in an electric vehicle or a hybrid electric vehicle as described above includes a battery pack in which a plurality of battery cells are connected in series, I am using

In addition, a plurality of battery packs including a plurality of battery cells are mounted in an electric vehicle according to vehicle specifications, and a separate device and a battery management system (battery management system) are provided. When external power is applied, So that the voltage of each battery cell is maintained at an appropriate level.

However, in the case of such a battery pack, when an external power source is applied and the battery management system is operated as described above, an environment in which the battery cell balancing operation can not be performed, that is, The balancing operation of the battery cell can not be performed, so that the charging voltage of the battery cell may become unbalanced.

Therefore, there is a high need for a battery pack having a battery cell balancing system to fundamentally solve such a problem.

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

More specifically, the object of the present invention is to provide a voltage balancing system for balancing battery cells using the battery pack's own power source, so that even when a battery pack is stored or transported for a long time after manufacture, And to provide a battery pack capable of solving the problem that the charge voltage of a cell becomes unbalanced.

According to an aspect of the present invention, there is provided a battery pack including a voltage balancing system,

Unit modules having a structure including one or more battery cells as unit cells;

A battery management system (BMS) for monitoring and controlling the operation of the battery pack;

A voltage balancing device included in the BMS and performing charge or discharge of each unit module by a control signal from the BMS; And

A DC / DC converter (direct current converter) for applying the power of the unit modules to the BMS;

As shown in Fig.

The unit module may include one battery cell or two or more series-connected battery cells. In some cases, the unit module includes two or more parallel-connected battery cells. It is possible.

In one specific example, the DC / DC converter may be configured to be activated when the external power source is not connected to the battery pack, and configured to apply power to the unit modules to the BMS.

Specifically, when the external power source is not connected, the BMS receives the power of the unit modules through the DC / DC converter and performs voltage balancing of the unit modules through the voltage balancing device using the power of the unit modules Lt; / RTI >

In this case, the voltage balancing may be performed by discharging the remaining unit modules according to the minimum voltage unit module among the unit modules, but the present invention is not limited thereto.

Therefore, the voltage balancing system of the battery pack according to the present invention has a structure in which the DC / DC converter is activated in an environment where external power is not connected, and performs voltage balancing by using its own power source inside the battery pack. It is possible to solve the problem that the charge voltage of the battery cell becomes unbalanced even when the battery is stored or transported for a long period of time after the manufacture.

On the other hand, when a battery pack constructed by connecting a plurality of battery cells in series or in parallel is used for a long period of time, characteristic factors of each battery cell are not equal to each other if the charge / discharge cycle is increased, The voltage becomes unbalanced and a dangerous situation such as an explosion may occur when the mutual voltage deviation between the battery cells is intensified.

Therefore, voltage balancing is required not only in an environment where external power is not applied but also in an environment where a battery pack is used. Specifically, when the external power source is connected to the battery pack according to the present invention, the DC / And in this case, the BMS can be configured to perform voltage balancing of the unit modules via the voltage balancing device using the connected external power source.

In one specific example, the voltage balancing method may be a method of charging the battery pack up to a critical charging voltage, and more specifically, the charging may be performed in a CC (Constant Current) charging manner.

In another specific example, the voltage balancing method may be a method of charging each unit module from a critical charging voltage to a full charge voltage. More specifically, the charging may be performed by a CV (constant voltage) charging method.

On the other hand, the external power source may be a power generating element capable of supplying power from the outside to the battery pack for charging the battery pack, for example, a charger of a battery pack or an external generator, The present invention may be an automotive generator that converts kinetic energy resulting from driving or braking of the vehicle into electricity, but is not limited thereto.

The present invention is also a voltage balancing method of the battery pack,

(a) determining whether an external power source is applied to the battery pack;

(b) When the external power source is not connected in the step (a), the DC / DC converter is activated to apply the power of the unit module to the BMS. When the external power source is connected, the DC / DC converter is deactivated, The process applied to this BMS;

(c) measuring a voltage of each unit module through the BMS; And

(d) performing voltage balancing of all the unit modules according to the voltage of each unit module measured in the step (c);

And a voltage balancing method.

For reference, the battery cell may be a lithium secondary battery, and the lithium secondary battery includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte solution containing a lithium salt.

The positive electrode is prepared, for example, by coating a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, and then drying the mixture. Optionally, a filler may be further added to the mixture.

The cathode active material may be 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. However, the present invention is not limited to these.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component 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 30% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

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

The negative electrode is manufactured by applying and drying a negative electrode active material on a negative electrode collector, and if necessary, the above-described components may be selectively included.

Examples of the negative electrode active material include carbon such as non-graphitized carbon and 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 < x < 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 ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

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

The non-aqueous electrolyte solution containing a lithium salt is composed of a polar organic electrolyte and a lithium salt. As the electrolytic solution, a non-aqueous liquid electrolytic solution, an organic solid electrolyte, an inorganic solid electrolyte and the like are used.

Examples of the nonaqueous liquid electrolytic solution 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, Polymers containing ionic dissociation groups, and the like can 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 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

For the purpose of improving the charge-discharge characteristics and the flame retardancy, the non-aqueous liquid electrolyte may contain, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride and the like are added It is possible. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

The present invention also provides a device using the battery pack as a power source, wherein the device is specifically a smart phone, a mobile phone, a laptop, a tablet PC, a wearable electronic device, an electric vehicle, a hybrid electric vehicle, A hybrid electric vehicle, a power storage system, or the like.

The structure of the battery pack and the diabis and the manufacturing method thereof are well known in the art, so a detailed description thereof will be omitted herein.

As described above, the battery pack according to the present invention includes the voltage balancing system for balancing the battery cells using the power source of the battery pack, so that even after the battery pack is stored or transported for a long time after the battery pack is manufactured There is an effect that the charging voltage of the battery cell becomes unbalanced without a separate external power supply.

1 is a schematic circuit diagram of a battery pack including a voltage balancing system according to one embodiment of the present invention;
2 is a schematic circuit diagram of a battery pack including a voltage balancing system according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

1 schematically shows a schematic circuit diagram of a battery pack including a voltage balancing system according to one embodiment of the present invention.

1, a battery pack 100 includes unit cells 111, 112, 113, 114, 115, and 116 including two or more battery cells connected in series or in parallel on a circuit, 100 and the BMS 120 and the DC / DC converter 130 that monitor and control the operation of the DC / DC converter.

The BMS 120 includes a voltage balancing device (not shown) that performs charging or discharging of the unit modules according to a control signal from the BMS 120. As shown in FIG. 1, The DC / DC converter 130 is activated and the power of the unit modules 111, 112, 113, 114, 115, and 116 is applied to the BMS 120 through the DC / DC converter 130 The voltage balancing of the unit modules 111, 112, 113, 114, 115, and 116 is performed through the voltage balancing device using the power of the unit modules 111, 112, 113, 114, 115, .

Therefore, when the external power source is not applied, the battery pack 100 having such a structure can perform the balancing operation of the unit modules 111, 112, 113, 114, 115, and 116 using the power source of the battery pack 100 itself And it is possible to solve the problem that the charge voltage of the battery cell becomes unbalanced without a separate external power source even in the process of storing or transporting the battery pack 100 for a long time after the battery pack 100 is manufactured.

2 schematically shows a schematic circuit diagram of a battery pack including a voltage balancing system according to another embodiment of the present invention.

2, the battery pack 200 includes unit modules 211, 212, 213, 214, 215, and 216 including two or more battery cells connected in series or in parallel on a circuit, 200 and the BMS 220 and the DC / DC converter 230 that monitor and control the operation of the DC / DC converter 200.

The BMS 220 includes a voltage balancing device (not shown) that performs charging or discharging of the unit modules according to a control signal from the BMS 220. As shown in FIG. 2, the external power source 300 The DC / DC converter 130 is inactivated and the external power source 300 is applied to the BMS 220. When the external power source 300 is connected to the unit modules (not shown) through the voltage balancing device, 211, 212, 213, 214, 215, 216).

That is, as shown in FIGS. 1 and 2, the battery pack having such a structure is configured to perform voltage balancing operation using the power of the unit modules included in the battery pack depending on whether an external power source is connected or not, It is possible to determine whether balancing is performed or not. In addition to an environment in which the battery pack is used in a state where external power such as a generic charger or a vehicle generator is connected, it is not connected to an external device, It is possible to solve the problem that the charging voltage of the battery cell becomes unbalanced.

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

Claims (16)

A battery pack comprising a voltage balancing system,
Unit modules having a structure including one or more battery cells as unit cells;
A battery management system (BMS) for monitoring and controlling the operation of the battery pack;
A voltage balancing device included in the BMS and performing charge or discharge of each unit module by a control signal from the BMS; And
A DC / DC converter (direct current converter) for applying the power of the unit modules to the BMS;
Wherein the DC / DC converter is configured to be inactivated when an external power source is connected to the battery pack. The battery pack according to claim 1, wherein the unit module comprises one battery cell or two or more series-connected battery cells. The battery pack according to claim 1, wherein the unit module comprises two or more parallel-connected battery cells. The battery pack according to claim 1, wherein the DC / DC converter is configured to be activated when an external power source is not connected to the battery pack, to apply power to the unit modules to the BMS. 5. The BMS of claim 4, wherein the BMS is configured to receive power from the unit modules through a DC / DC converter and perform voltage balancing of the unit modules through the voltage balancing device using the power of the unit modules Battery pack. The battery pack according to claim 5, wherein the voltage balancing is performed in such a manner that the remaining unit modules are discharged in accordance with the unit module of the minimum voltage among the unit modules. delete The battery pack according to claim 1, wherein the BMS is configured to perform voltage balancing of the unit modules through a voltage balancing device using an external power source when an external power source is connected to the battery pack. The battery pack according to claim 8, wherein the voltage balancing is performed by charging each unit module up to a critical charge voltage. The battery pack according to claim 9, wherein the charging is performed by a CC (Constant Current) charging method. The battery pack according to claim 9, wherein the voltage balancing further charges each unit module from a critical charging voltage to a full charge voltage. The battery pack according to claim 11, wherein the charging is performed by a CV (constant voltage) charging method. The battery pack according to claim 4 or 8, wherein the external power source is a charger, an external generator, or a generator for a vehicle. A method of balancing a voltage of a battery pack according to claim 1,
(a) determining whether an external power source is applied to the battery pack;
(b) When the external power source is not connected in the step (a), the DC / DC converter is activated to apply the power of the unit module to the BMS. When the external power source is connected, the DC / DC converter is deactivated, The process applied to this BMS;
(c) measuring a voltage of each unit module through the BMS; And
(d) performing voltage balancing of all the unit modules according to the voltage of each unit module measured in the step (c);
≪ / RTI > A device comprising a battery pack according to claim 1. 16. The device of claim 15, wherein the device is selected from a smart phone, a mobile phone, a laptop, a tablet PC, a wearable electronic device, an electric vehicle, a hybrid electric vehicle, a plug- .

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