BATTERY CELL FOR ELECTRIC VEHICLE AND METHOD FOR MANUFACTURING THE SAME

A battery cell for an electric vehicle is provided and includes a plurality of positive electrode plates each including a positive current collector coated with a positive active material and having a plurality of positive electrode terminals in one direction, a plurality of negative electrode plates each including a negative current collector coated with a negative active material and having a plurality of negative electrode terminals in an opposite direction. The battery cell also includes a plurality of separators each including a film member coated with an insulating material and interposed between adjacent pair of the positive electrode plate and the negative electrode plate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2019-0120446 filed on Sep. 30, 2019, the entire contents of which are incorporated herein by reference.

BACKGROUND

(a) Field of the Disclosure

The present disclosure relates to a battery cell for an electric vehicle and a method for manufacturing the same, and more particularly, to a battery cell that enables multiplication of current flow through the electrode terminals and minimizes resistance during charging and discharging.

(b) Description of the Related Art

Currently used secondary batteries include a nickel cadmium battery, a nickel hydrogen battery, a nickel zinc battery, and a lithium secondary battery. Among such batteries, a lithium secondary battery is often preferred due to the merit of free charging and discharging, a very low self-discharge rate, and a high energy density, in comparison with nickel-based secondary batteries.

Such lithium secondary batteries typically use lithium-based oxides and carbon materials as positive active materials and negative active materials, respectively. The lithium secondary battery includes an electrode assembly and an exterior member that seals the electrode assembly with the electrolyte solution. In a typical electrode assembly, a positive electrode plate is formed by a positive current collector coated with a positive active material, a negative electrode plate is formed by a negative current collector coated with a negative active material, and a separator is disposed between the positive and negative electrode plates.

The lithium secondary battery may be classified, according to a shape of the battery case, into a can-type secondary battery in which an electrode assembly is installed in a metal can, and a pouch-type secondary battery in which an electrode assembly is installed in a pouch of an aluminum laminate sheet. Recently, secondary batteries have been widely used not only for small devices such as portable electronic devices but also for medium and large devices such as automobiles and energy storage devices (ESS).

When used in such a medium-large device, a substantial number of secondary batteries are electrically interconnected to form a battery module and a battery pack to increase capacity and output. In particular, the pouch-type secondary battery is widely used in such a medium-large device due to its merit of easy stacking and being light weight. The battery cell including the pouch-type secondary battery has a sealed structure in which an electrode assembly having positive and negative electrodes respectively connected to electrode terminals is housed together with an electrolyte solution in a pouch case. Some of the electrode terminals are exposed to the outside of the pouch case, and the exposed electrode terminals are used to electrically connect the device on which the battery cell is mounted, or to electrically connect the positive and negative electrodes to each other.

In conventional battery cells, current flows through the positive and the negative electrode terminals during charging and discharging, and to minimize resistance, it is common to thicken the positive and negative terminals. In such a conventional battery cell having thicker positive and negative electrode terminals, welding characteristic may deteriorate, and may thus crack and disconnection of the positive and negative electrode terminals in the manufacturing process may occur. In addition, according to a conventional battery cell, the thick thickness of the positive and negative electrode terminals may cause quality deterioration of the module welding during a secondary welding of the stacked terminals in a module assembly process.

SUMMARY

The present disclosure provides a battery cell for an electric vehicle and a method for manufacturing the same having advantages of employing a plurality of positive electrode terminals and negative electrode terminals, thereby enabling multiplication of current flow through the electrode terminals, and minimizing resistance during charging and discharging. By employing a plurality of positive electrode terminals and negative electrode terminals, thickness of terminals may be reduced, and therefore, welding quality may be improved, thereby improving product quality.

An exemplary battery cell for an electric vehicle may include a plurality of positive electrode plates each including a positive current collector coated with a positive active material and having a plurality of positive electrode terminals in a first direction, a plurality of negative electrode plates each including a negative current collector coated with a negative active material and having a plurality of negative electrode terminals in a second direction (e.g., opposite to the first direction), and a plurality of separators each including a film member coated with an insulating material and interposed between adjacent pair of the positive electrode plate and the negative electrode plate.

A first positive electrode tab and a second positive electrode tab uncoated with the positive active material may be formed apart by a predetermined spacing in each of the positive electrode plates. A first positive electrode terminal may be electrically connected to the first positive electrode tab. A second positive electrode terminal may be electrically connected to the second positive electrode tab. The first and second positive electrode terminals may be formed in a width in a range of about 40 mm to 50 mm and in a thickness in a range of about 0.1 mm to 0.2 mm. The first and second positive electrode terminals may be symmetrically formed at both sides with respect to a center in a length direction of the positive electrode plate.

A first negative electrode tab and a second negative electrode tab uncoated with the negative active material may be formed spaced apart from each other by a predetermined spacing in each of the negative electrode plate. A first negative electrode terminal may be electrically connected to the first negative electrode tab. A second negative electrode terminal may be electrically connected to the second negative electrode tab. The first and second negative electrode terminals may be formed in a width in a range of about 40 mm to 50 mm and in a thickness in a range of about 0.05 mm to 0.1 mm. The first and second negative electrode terminals may be symmetrically formed at both sides with respect to a center in a length direction of the negative electrode plate.

The plurality of positive electrode plates and the plurality of negative electrode plates may be stacked alternately to dispose the positive electrode terminals and the negative electrode terminals in opposite directions. Each adjacent pair of the positive and negative plates may be insulated from each other by interposing the separator.

An exemplary battery cell for an electric vehicle may further include a pouch for sealing the positive electrode plates, the negative electrode plates, and the separators, while exteriorly exposing the positive electrode terminal and the negative electrode terminal. The positive electrode plate may include a positive current collector formed of an aluminum (Al) thin film material, and the negative electrode plate may include a negative current collector formed of a copper (Cu) thin film material.

An exemplary method for manufacturing a battery cell for an electric vehicle may include forming a plurality of positive electrode plates each having a first positive electrode tab and a second positive electrode tab, forming a plurality of negative electrode plates each having a first negative electrode tab and a second negative electrode tab, forming a plurality of separators each having a film member coated with an insulating material at both sides, forming an electrode assembly by stacking the plurality of positive electrode plates, the plurality of negative electrode plates, and the plurality of separators to alternately stack the positive electrode plates and the negative electrode plates and each adjacent pair of the positive and negative electrode plates may be insulated by interposing the separator, and connecting a plurality of positive electrode terminals to the positive electrode plates and a plurality of negative electrode terminals to the negative electrode plates.

The forming of the plurality of positive electrode plates may include forming a positive electrode coated portion by coating a positive active material to both sides of a positive current collector except for a margin including a positive electrode tab portion, loading the positive current collector to a notching die, and forming the positive electrode plate by cutting the positive electrode tab portion to form the first positive electrode tab and the second positive electrode tab, and by cutting the positive current collector by a predetermined interval. The notching die may include an upper die having a plurality of tab protrusions to form the first and second positive electrode tabs and a cutter blade for cutting the positive current collector by a predetermined interval, and a lower die having a plurality of tab grooves that correspond to the plurality of tab protrusions and a cutter groove that corresponds to the cutter blade.

The forming of the plurality of negative electrode plates may include forming a negative electrode coated portion by coating a negative active material to both sides of a negative current collector except for a margin including a negative electrode tab portion, loading the negative current collector to a notching die, and forming the negative electrode plate by cutting the negative electrode tab portion to form the first negative electrode tab and the second negative electrode tab, and by cutting the negative current collector by a predetermined interval.

The notching die may include an upper die having a plurality of tab protrusions to form the first and second negative electrode tabs and a cutter blade for cutting the negative current collector by a predetermined interval, and a lower die having a plurality of tab grooves that correspond to the plurality of tab protrusions and a cutter groove that corresponds to the cutter blade. The forming of the electrode assembly may include welding the first positive electrode tabs of the plurality of positive electrode plates, welding the second positive electrode tabs of the plurality of positive electrode plates, welding the first negative electrode tabs of the plurality of negative electrode plates, and welding the second negative electrode tabs of the plurality of negative electrode plates.

The connecting of the plurality of positive electrode terminals to the positive electrode plates and the plurality of negative electrode terminals to the negative electrode plates may include loading the electrode assembly into a welding jig, loading a first positive electrode terminal and a first negative electrode terminal to the first positive electrode tab and the first negative electrode tab, respectively, welding the first positive electrode terminal and the first negative electrode terminal to the first positive electrode tab and the first negative electrode tab, respectively, by a welding horn, loading a second positive electrode terminal and a second negative electrode terminal to the second positive electrode tab and the second negative electrode tab, respectively, and welding the second positive electrode terminal and the second negative electrode terminal to the second positive electrode tab and the second negative electrode tab, respectively, by moving the welding horn. The welding may include ultrasonic welding.

An exemplary method for manufacturing a battery cell may further include sealing the electrode assembly by a pouch while exteriorly exposing at least a part of the electrode terminals. According to a battery cell for an electric vehicle and a method for manufacturing the same according to an exemplary embodiment, a plurality of positive electrode terminals and negative electrode terminals may be employed, e.g., a pair. Therefore, thickness of respective terminals may be reduced, thereby improving welding quality and improving output performance. Further, effects that may be obtained or expected from exemplary embodiments of the present disclosure are directly or suggestively described in the following detailed description. In other words, various effects expected from exemplary embodiments of the present disclosure will be described in the following detailed description.

DETAILED DESCRIPTION

The present disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present disclosure. The drawings and description are to be regarded as illustrative in nature and not restrictive, and like reference numerals designate like elements throughout the specification. In the following description, dividing names of components into first, second and the like is to divide the names because the names of the components are the same as each other and an order thereof is not particularly limited.

FIG. 1is a detailed view of a battery cell for an electric vehicle according to an exemplary embodiment.FIG. 2is a perspective view illustrating a positive electrode plate, a separator, and a negative electrode plate applied to a battery cell for an electric vehicle according to an exemplary embodiment.FIG. 3toFIG. 5are process diagrams sequentially illustrating a method for manufacturing a battery cell for an electric vehicle according to an exemplary embodiment.

A battery cell1for an electric vehicle and a method for manufacturing the same according to an exemplary embodiment may be applicable to a pouch-type lithium secondary battery applicable to an electric vehicle. The battery cell applied to the pouch-type lithium secondary battery may use a lithium metal battery having lithium metal as a negative active material, and may be applied to an electric vehicle due to capability of charging and discharging and due to high energy density.

Referring toFIG. 1andFIG. 2, such a battery cell1for an electric vehicle may include a positive electrode plate10, a negative electrode plate30, a separator50, and a pouch60. The battery cell1may be electrically connected by stacking the positive electrode plate10, the negative electrode plates30, and the separators50, in a range of about 20-30 sheets. A plurality of battery cells1may be stacked to form a battery module, and a plurality of battery modules may form a battery pack. The battery pack may be installed within an electric vehicle, e.g., at a bottom of the electric vehicle, and may operate as an electric power source to drive the electric vehicle.

The positive electrode plate10of a battery cell1for an electric vehicle according to an exemplary embodiment may include a positive current collector11applied with positive active material13at both sides thereof. The positive current collector11may be formed of an aluminum (Al) thin film material. Both surfaces of the positive current collector11may be coated with a positive active material13including a metal oxide containing lithium, for example, lithium cobalt oxide (LiCoO2).

It may be understood that the positive active material13may be applied to only one surface of the positive current collector11, not necessarily to both surfaces of the positive current collector11. In addition, the positive active material13may be applied to the positive current collector11with a margin to an edge of the positive current collector11.

The positive electrode plate10may be divided into a positive electrode coated portion17that is coated with the positive active material13and a positive electrode tab portion19that is not coated with the positive active material13. Through the positive electrode tab portion19, the positive electrode plate10may form a first positive electrode tab15aand a second positive electrode tab15bspaced apart from each other. The first positive electrode tab15aand the second positive electrode tab15bmay be formed symmetrically at both sides with respect to the center, e.g., in a length direction of the positive electrode plate10.

In addition, the positive electrode plate10may include a plurality of positive electrode terminals20that protrude outwardly. The plurality of positive electrode terminals20may include a first positive electrode terminal20aelectrically connected to the first positive electrode tabs15aand a second positive electrode terminal20belectrically connected to the second positive electrode tabs15b. The first positive electrode terminal20aand the second positive electrode terminal20bmay be electrically connected to the first positive electrode tab15aand the second positive electrode tab15b, respectively. The same as the first and second positive electrode tabs15aand15b, the first and second positive electrode terminals20aand20bmay be formed symmetrically at both sides with respect to the center of the positive electrode plate10.

The width of the first and second positive electrode terminals20aand20bmay be set in a range of about 40 mm to 50 mm. In addition, the thickness of the first and second positive electrode terminals20aand20bmay be set in a range of about 0.1 mm to 0.2 mm. It may be understood that the thickness of the positive electrode terminals set in the range of about 0.1 mm to 0.2 mm according to an exemplary embodiment is significantly thinner than a conventional thickness that is typically set in a range of 0.4 mm to 0.6 mm.

The negative electrode plate30of a battery cell1for an electric vehicle according to an exemplary embodiment may include a negative current collector31applied with negative active material33at both sides thereof. The negative current collector31may be formed as a copper (Cu) thin film material. Both surfaces of the negative current collector31may be coated with the negative active material33containing carbon. It may be understood that the negative active material33may be applied to only one surface of the negative current collector31, not necessarily to both surfaces of the negative current collector31. In addition, the negative active material33may be applied to the negative current collector31with a margin to an edge of the negative current collector31.

The negative electrode plate30may be divided into a negative electrode coated portion37that is coated with the negative active material33and a negative electrode tab portion39that is not coated with the negative active material33. Through the negative electrode tab portion39, the negative electrode plate30may form a first negative electrode tab35aand a second negative electrode tab35bspaced apart from each other. The first negative electrode tab35aand the second negative electrode tab35bmay be formed symmetrically at both sides with respect to the center, e.g., in a length direction of the negative electrode plate30.

In addition, the negative electrode plate30may include a plurality of negative electrode terminals40that protrude outwardly. The plurality of negative electrode terminal40may include a first negative electrode terminal40aelectrically connected to the first negative electrode tabs35aand a second negative electrode terminal40belectrically connected to the second negative electrode tabs35b. The first negative electrode terminal40aand the second negative electrode terminal40bmay be electrically connected to the first negative electrode tab35aand the second negative electrode tab35b, respectively. The same as the first and second negative electrode tabs35aand35b, the first and second negative electrode terminals40aand40bmay be formed symmetrically at both sides with respect to the center of the negative electrode plate30.

The width of the first and second negative electrode terminals40aand40bmay be set in a range of about 40 mm to 50 mm. In addition, the thickness of the first and second negative electrode terminal40aand40bmay be set in a range of about 0.05 mm to 0.1 mm. It may be understood that the thickness of the negative electrode terminals set in the range of about 0.1 mm to 0.2 mm according to an exemplary embodiment is significantly thinner than a conventional thickness that is typically set in a range of 0.4 mm to 0.6 mm.

The separator50of a battery cell1for an electric vehicle according to an exemplary embodiment may include a film member51applied with an insulating material53at both sides thereof. The film member51may include a polyethylene, polypropylene, etc. In addition, the insulating material53may be formed of a ceramic material.

The positive electrode plate10, the negative electrode plate30, and the separator50may be alternately stacked to dispose the positive electrode terminal20and the negative electrode terminal40in opposite directions, and the separator50may be interposed therebetween. In other words, a plurality of layers of the positive electrode plate10, the separator50, the negative electrode plate30, and the separator50may be stacked, and may be arranged to align the positive electrode tabs15of the positive electrode plate10with each other, and to the negative electrode of the negative electrode plate30with each other.

The separator50may be interposed between the positive electrode plate10and the negative electrode plate30to prevent the contact between the positive electrode plate10and the negative electrode plate30, thereby increasing stability. In addition, the pouch60of a battery cell1for an electric vehicle according to an exemplary embodiment may seal the stack of the plurality of the positive electrode plates10, the negative electrode plates30, and the separators50, while exposing the two positive electrode terminals20and the two negative electrode terminal40. The pouch60may be filled with an electrolyte solution. The pouch60may include a metal thin film.

A method for manufacturing a battery cell for an electric vehicle according to an exemplary embodiment is as follows. Referring toFIG. 3, firstly, a positive electrode plate10may be formed. For the positive electrode plate10, the positive active material13may be coated on both sides of the positive current collector11, except for a margin including the positive electrode tab portion19.

Particularly, the portion of the positive electrode plate10coated with the positive active material13may be referred to as the positive electrode coated portion17.

Subsequently, the positive current collector11may be loaded at a notching die70, and the positive electrode tab portion19may be cut. By the notching die70, the positive electrode tab portion19may be cut to form the first positive electrode tab15aand the second positive electrode tab15bthat are spaced apart from each other. At the same time, by the notching die70, the positive current collector11may be cut by a predetermined interval to form the positive electrode plate10.

The notching die70may include an upper die70aand a lower die70b. The upper die70amay include tab protrusions71ato form the first and second positive electrode tabs35aand35b, and the lower die70bmay include tab grooves71bcorresponding to the tab protrusions71a. In addition, the upper die70amay include a cutter blade73afor cutting the positive current collector11by the predetermined interval. The lower die70bmay include a cutter groove73bthat corresponds to the cutter blade73a. In other words, the notching die70may cut the positive current collector11by the predetermined interval by the cutter blade73aof the upper die70aand the cutter groove73bof the lower die70bto form the positive electrode plate10.

Subsequently, the negative electrode plate30may be formed. For the negative electrode plate30, the same as for the positive electrode plate10, the negative active material33may be coated on both sides of the negative current collector31, except for a margin including the negative electrode tab portion39. Particularly, the portion of the negative electrode plate30coated with the negative active material33may be referred to as the negative electrode coated portion37.

Subsequently, the negative current collector31may be loaded at the notching die70, and the negative electrode tab portion39may be cut. By the notching die70, the negative electrode tab portion39may be cut to form the first negative electrode tabs35aand the second negative electrode tab35bthat are spaced apart. At the same time, by the notching die70, the negative current collector31may be cut by a predetermined interval to form the negative electrode plate30. It may be understood that the die notching die70used for forming the positive electrode plate10may be used for forming the negative electrode plate30. Subsequently, the separator50may be formed. In particular, the separator50may be formed by coating an insulating material53on both sides of film member51, as illustrated inFIG. 1.

Referring toFIG. 4, the positive electrode plate10, the separator50, the negative electrode plate30, and the separator50may be stacked continuously (e.g., multiple alterations of the components may be stacked) to form an electrode assembly. The positive electrode plates10and the negative electrode plates30may be stacked interposing the separators50, e.g., in a range of about 20 to 30 sheets respectively, to form the electrode assembly.

The positive electrode tabs15of the positive electrode plates10and the negative electrode tabs35of the negative electrode plates30may be disposed in opposite directions, while maintaining the positive electrode tabs15in the same direction and position and the negative electrode tabs35in the same direction and position. To form the electrode assembly, the positive electrode tabs15may be welded together and the negative electrode tabs35may be welded together. In other words, the first positive electrode tabs15aof the plurality of positive electrode plates10may be welded together, the second positive electrode tabs15bof the plurality of positive electrode plates10may be welded together, the first negative electrode tabs35aof the plurality of negative electrode plates10may be welded together, and the second negative electrode tabs35bof the plurality of negative electrode plates10may be welded together.

Subsequently, the electrode assembly may be loaded into the welding jig80, and then the first positive electrode terminal20aand the first negative electrode terminal40amay be respectively loaded on the first positive electrode tab15aand the first negative electrode tab35a, respectively. By welding horns81, the first positive electrode tab15aand the first positive electrode terminal20amay be electrically connected to each other by welding, and the first negative electrode tab35aand the first negative electrode terminal40amay be electrically connected to each other by welding.

Referring toFIG. 5, the second positive electrode terminal20band the second negative electrode terminal40bmay be respectively loaded on the second positive electrode tab15band the second negative electrode tab35b, respectively. The welding horns81may be moved, and by the welding horns81, the second positive electrode tab15band the second positive electrode terminal20bmay be electrically connected to each other by welding, and the second negative electrode tab35band the second negative electrode terminal40bmay be electrically connected to each other by welding.

The positive electrode terminals20and the negative electrode terminals40may be welded to the positive electrode tabs15and the negative electrode tabs35, e.g., by ultrasonic welding or laser welding, but the present disclosure is not limited thereto. Finally, the stack of the positive electrode plates10, the negative electrode plates30, and the separators50therebetween may be sealed by the pouch60, while exteriorly exposing the first and second positive electrode terminals20aand20band the first and second negative electrode terminals40aand40b. At this time, the electrolyte solution may be filled in the pouch60.

Therefore, according to a battery cell for an electric vehicle and a method for manufacturing the same according to an exemplary embodiment, a plurality of positive electrode terminals20and negative electrode terminals40are employed, e.g., by a pair, and therefore, thickness of respective terminals may be reduced. Accordingly, welding quality may be improved. In addition, according to a battery cell for an electric vehicle and a method for manufacturing the same according to an exemplary embodiment, a current flow through the electrode terminal may be multiplied, and thereby resistance during charging and discharging may be minimized. According to a battery cell for an electric vehicle and a method for manufacturing the same according to an exemplary embodiment, conventional welding equipment may be used, and therefore, the product quality may be improved without causing extra investment cost.

In addition, according to a battery cell for an electric vehicle and a method for manufacturing the same according to an exemplary embodiment, two positive electrode tabs15and two negative electrode tabs35may be simultaneously formed at the positive electrode plate10and the negative electrode plate30, respectively, by altering the form of a notching die70. Therefore, an overall productivity may be improved and an overall production cycle time may be reduced.

DESCRIPTION OF SYMBOLS