Patent Description:
In lithium batteries, an aluminum foil is usually adopted as a positive current collector, and a copper foil is adopted as a negative current collector. With the continuous development of the battery industry, a current collector with better performance can be adopted. <CIT> refers to a rotary ultrasonic welding device for cutting and/or producing weld seams by means of ultrasound, which includes at least one sonotrode and a magnetic roller opposite to the sonotrode. A magnet is arranged on the circumference of the magnetic roller, and a magnetic force of the contour sheet is applied into the contour of a weld seam. <CIT> refers to an arrangement for ultrasonic roller welding. The rotationally symmetrical ultrasonic horn (Sonotrode) is widened out in a trumpet-shaped manner. The ultrasonic oscillation is by this means transmitted to the work surface such that the latter oscillates is perpendicular to the workpiece. <CIT> relates to the methods which make it possible to establish contacts between two conductive layers separated by an insulating layer. It consists in pressing the complex formed by these three layers between a sonotrode excited by ultrasound perpendicular to the plane of the complex and an anvil whose face in contact with the complex has protruding ridges. DATABASE WPI Week <NUM> Thomson Scientific, London, GB; AN <NUM>-75123N & <CIT> (<NUM>-<NUM>-<NUM>) refers to a method involving performing pressure-compressing and hardening of a current collection terminal (<NUM>) from both surface by an unprotruded forging tool. The pressurization and an ultrasonic wave are added and the electrode foil are joined by a protrusion-existing tool such as anvil from the electrode foil side.

With the continuous development of the battery industry, there has been a composite current collector composed of high polymer and metal. The composite current collector can reduce the temperature rise of the battery, reduce the risk of thermal runaway, and improve the safety of the battery. However, since the composite current collector includes an insulating layer formed of high polymer material, the tab of the composite current collector cannot output the current in the battery cell to the electrode terminal, which requires using the foil (an aluminum foil or a copper foil) to transfer-connect with the tab of the composite current collector such that the current in the battery cell is output.

The present disclosure provides a welding device and a processing apparatus for a secondary battery current collector, which can achieve the connection of the foil with the composite current collector so as to output the current in the battery cell.

The present disclosure provides a welding device for a secondary battery current collector, comprising: a welding head; and an anvil block. A welding station is disposed between the welding head and the anvil block. The welding head is configured to weld a foil to a portion of a composite current collector at the welding station.

The welding device is configured to continuously weld the foil to the portion of the composite current collector at the welding station.

The welding head is configured as an ultrasonic welding head, the ultrasonic welding head being in rolling contact with the anvil block. The ultrasonic welding head and the anvil block are respectively configured as cylinders so as to rotate with respect to each other.

A plurality of extrusion welding teeth is arranged on an outer circumferential face of one of the ultrasonic welding head and the anvil block.

The present disclosure also provides a processing apparatus for a secondary battery current collector. The processing apparatus includes: a foil uncoiling roller; a composite current collector uncoiling roller; a conveying roller; a coiling roller; and the welding device according to any one of the above aspects. Both the foil uncoiling roller and the composite current collector uncoiling roller are disposed on a feeding side of the welding device, and the coiling roller is disposed on a discharging side of the welding device. The welding device is configured to weld the foil to a portion of the composite current collector at the welding station.

In an embodiment, the processing apparatus further includes a driving device. One of the welding head and the anvil block is coupled to the driving device in a transmission way to adjust a contact force therebetween when they contact with each other.

In an embodiment, the processing apparatus further includes a first pressure roller and a second pressure roller provided in pairs. The first pressure roller and the second pressure roller have a gap therebetween for passage of the composite current collector and the foil, and the foil and the composite current collector are overlapped in the gap. The first pressure roller is disposed on a discharging side of the foil uncoiling roller and the feeding side of the welding device, and the second pressure roller is disposed on a discharging side of the composite current collector uncoiling roller and the feeding side of the welding device.

In an embodiment, the processing apparatus further includes a pre-pressure roller configured to press one of the foil and the composite current collector to the other of the foil and the composite current collector to make the foil and the composite current collector overlap. The pre-pressure roller is disposed on a feeding side of the first pressure roller and the second pressure roller.

In an embodiment, the processing apparatus further includes a rectifying device configured to rectify a position offset of the foil from the composite current collector. The rectifying device is disposed on a feeding side of the pre-pressure roller.

In an embodiment, the processing apparatus further includes a tension adjusting device. The tension adjusting device is movably disposed to adjust tension of the foil and the composite current collector.

The technical aspect provided by the present disclosure can achieve the following beneficial effects.

The present disclosure provides a processing apparatus for a secondary battery current collector. The welding device can weld a foil input to the welding station to a portion of a composite current collector, so that the foil can be used as a tab of the composite current collector and the current in the battery cell can be output with the transfer of the foil.

It should be understood that the above general description is merely illustrative, but not intended to limit the present disclosure.

Accompanying drawings illustrating embodiments according to the present disclosure are incorporated in the description as a part, and used to elaborate the principle of the present disclosure.

The present disclosure will be further described below by specific embodiments of the present disclosure in combination with the drawings.

It should be understood that terms indicating orientations or positions, such as "up", "down", "left", "right", etc., generally are used to describe the orientations or positions with reference to the drawings, and thus should not be construed as a limitation to the embodiments of the present disclosure. It also should be understood that when an element is referred as being "on" or "under" another element, the element can be directly located "on" or "under" another element or connected to another element with an intermediate element.

The present disclosure provides a processing method for a secondary battery current collector, and this processing method can weld a composite current collector and a foil together to output electrical energy stored in the battery cell to an electrode terminal of the secondary battery through the foil.

The foil may be an aluminum foil or a copper foil, in which an aluminum foil is applied to the positive electrode and a copper foil is applied to the negative electrode. Correspondingly, a composite current collector containing metal aluminum is applied to the positive electrode, and a composite current collector containing metal copper is applied to the negative electrode.

As shown in <FIG>, the processing method may include the following steps.

At Step S20, a foil material coil and a composite current collector material coil are provided. The foil and the composite current collector are strip materials and are wound around a discharging roller to form a material coil.

At Step S40, the foil material coil and the composite current collector material coil are driven to discharge. For example, each discharging roller can be mounted on a shaft through a bearing, and under driving of an external force, each discharging roller rotates to achieve the discharge of the foil material coil and the composite current collector material coil. The external force can be a conveying force provided by a conveying roller.

After discharging, the single layer foil and the single layer composite current collector, as an upper layer and a lower layer, respectively, are jointly conveyed to the welding device, which in turn fixes the foil to a portion of the composite current collector by welding.

At Step S60, the composite current collector and the foil material fixed together after welding are coiled on the coiling roller. The coiling roller can be driven to rotate by an electric device such as a motor, and a coiling force applied by the coiling roller to the foil and the composite current collector can also be used as an external force to drive the discharging roller to rotate and discharge.

According to the above description, this processing method can weld the foil to the composite current collector. In this way, the foil can be used as a tab of the composite current collector, such that the current in the battery cell can be output through the transfer of the foil.

In the present disclosure, in step S40, the method for welding the foil and the composite current collector is not specifically limited. In one embodiment, the foil and the composite current collector can be laser-welded.

In other embodiments, as shown in <FIG>, the foil and the composite current collector may also be ultrasonic-welded. Ultrasonic welding is to transmit high-frequency vibration waves to surfaces of two objects to be welded, such that the surfaces of the two objects rub against each other to form a fusion between molecular layers in the case of increasing pressure. As regarding to a composite current collector, the middle layer thereof is a plastic layer and the plastic layer is provided with a metal layer on both sides. Ultrasonic welding can effectively penetrate the plastic layer in the middle and fuse the foil with the metal layers on both sides to increase the thickness of the metal, such that the current in the battery cell can be reliably output from the fused portion.

Further, as shown in <FIG>, in step S40, the foil may be continuously welded to a portion of the composite current collector. That is, the foil and the composite current collector are welded during the conveying process such that continuous welding marks are formed on them. This solution can eliminate the need to stop the foil and the composite current collector during the conveying process, which reduces processing time and increases processing efficiency.

In addition, in ultrasonic welding, conductivity of the fused portion of the welded foil and the composite current collector should also be taken into account. In one embodiment, in step S40, the foil may be input to a side of the welding device close to the welding tooth portion, and correspondingly, the composite current collector is fed into a side of the welding station close to the non-welding tooth portion. The foil is usually rolled from a metal into a thin material, for example, a copper foil is rolled from a copper material and an aluminum foil is rolled from an aluminum material. After arranging in the above manner, during the ultrasonic welding process, the welding tooth portion contacts and presses the foil. Since the plasticity of the copper foil and the aluminum foil is good, the foil is stretched under the action of the pressing force and is firstly fused with the metal layer on the upper side of the plastic layer in the composite current collector. When the extrusion welding teeth continue to penetrate the plastic layer, the stretched foil can pass through the penetration hole to be fused with the metal layer on the lower side of the plastic layer. Thus, the foil is fused with the metal layers on the upper and lower sides of the plastic layer, which results in a higher degree of fusion of the foil and the composite current collector and thus increases conductivity, such that the current in the battery cell can be reliably output.

It should be noted here that the welding device comprises two portions, one of which is a welding tooth portion which comprises extrusion welding teeth and while the other of which is a non-welding tooth portion which can be surface smoothed by grinding or the like to reduce the roughness. The welding tooth portion and the non-welding tooth portion have a welding station located therebetween. The foil and the composite current collector can pass through the welding station and then be welded together.

It should be understand that the foil and the composite current collector are both made of thin materials, which may have low strength and may not withstand large tearing force. Therefore, it is required that the relative position of the foil and the composite current collector is maintained to be fixed during welding, otherwise, cracks may occur after welding, and in severe cases, strip breakage may occur such that the production cannot be performed continuously. To this end, as shown in <FIG>, in step S40, it is also possible to overlap the foil and the composite current collector before welding. In this way, before being input to the welding station, the foil and the composite current collector can be conveyed in the same direction within a certain length and jointly conveyed to the welding station in an overlapped state so as to reduce the speed difference therebetween, such that the conveying speeds of them tend to be consistent to maintain their relative positions to be fixed, thereby improving the welding quality of the foil and the composite current collector.

As shown in <FIG>, further, when the foil and the composite current collector are welded, there is a high requirement for overlapping dimension of the foil and the composite current collector. In order to ensure the accuracy of the position when the foil and the composite current collector overlap, it is also possible to rectify a deviation of the foil and the composite current collector before overlapping in step S40 to correct positions of the foil and the composite current collector in a convenient and quick manner, such that the overlapped foil and composite current collector can overlap at a predetermined position to meet requirements for the overlapping dimension.

On the other hand, the welding quality can be further ensured if the thin material enters the welding station in the horizontal direction. To this end, in step S40, the overlapped foil and the composite current collector can be further configured to be input to the welding station in the horizontal direction. Such arrangement can reduce defects such as bending and wrinkles occurring in the foil and the composite current collector during the conveying process, thereby ensuring the flatness during welding and improving the welding quality.

Further, the foil material coil can also be symmetrically disposed with the composite current collector material coil. For example, if the overlapped composite current collector and foil are input to the welding station in the horizontal direction, it is assumed that there is an imaginary plane which is parallel to the composite current collector and the foil and located between the composite current collector and the foil, such that the foil material coil and the composite current collector material coil may be symmetrically disposed on two sides of the imaginary plane. Thus, when the foil material coil and the composite current collector material coil discharge, both of them can enter the welding station via paths of a same length, which can reduce the difference in tension between the foil and the composite current collector and ensure the flatness of the foil and the composite current collector when they are overlapped.

It should be noted that various parameters of the ultrasonic welding may be selected by those skilled in the art according to the specific application environment, which is not limited in the present disclosure.

According to one embodiment, a <NUM> ultrasonic welding head can be adopted. The diameter of the ultrasonic welding head is about <NUM>. The ultrasonic welding head is provided with welding teeth (the welding tooth portion) and the anvil block (the non-welding tooth portion) is surface treated.

Welding objects include a composite current collector having a thickness of <NUM> and an aluminum foil having a thickness of <NUM>. Preset parameters include a pressure of <NUM>. 3MPa, an amplitude of <NUM> and a speed of <NUM>/min. After testing, the welding sample has a resistance value of about <NUM> mQ, and a pulling force of about 15N.

The overall width of the welding teeth of the ultrasonic welding head can be selected in a range of <NUM> to <NUM>, preferably <NUM> to <NUM>. The vibration frequency of the ultrasonic welding head is preferably <NUM> or <NUM>. The diameter of the ultrasonic welding head is selected in a range of <NUM> to <NUM>. The thickness of the aluminum foil can be selected in a range of <NUM> to <NUM>, preferably <NUM> to <NUM>. The thickness of the copper foil can be selected in a range of <NUM> to <NUM>, preferably <NUM> to <NUM>. The line speed of the ultrasonic welding head is preferably in a range of <NUM>/min to <NUM>/min. The cylinder pressure is preferably in a range of <NUM> MPa to <NUM> MPa.

Based on the above processing method for the secondary battery current collector, the present disclosure further provides a processing apparatus for a secondary battery current collector. The processing apparatus processes the secondary battery current collector by the processing method described above.

Specifically, as shown in <FIG>, the processing apparatus includes a foil uncoiling roller <NUM>, a composite current collector uncoiling roller <NUM>, a welding device <NUM>, a coiling roller <NUM>, a conveying roller <NUM>, and the like. The foil uncoiling roller <NUM> is used for uncoiling the foil, and the composite current collector uncoiling roller <NUM> is used for uncoiling the composite current collector. The welding device <NUM> is used to weld and fix the foil to the composite current collector.

There are usually a plurality of conveying rollers <NUM> provided, which is respectively disposed on the discharging side of the foil uncoiling roller <NUM> and the composite current collector uncoiling roller <NUM> and the feeding side of the welding device <NUM>, so as to convey the foil and the composite current collector to the welding device <NUM>.

The welding device <NUM> includes a welding head <NUM> and an anvil block <NUM>. A welding station is provided between the welding head <NUM> and the anvil block <NUM>. The foil and the composite current collector pass through between the welding head <NUM> and the anvil block <NUM> and are welded and fixed together. When welding, the foil is welded to a portion of the composite current collector. After welding, the foil acts as a tab of the composite current collector, and the welding device outputs the current to the outside.

The coiling roller <NUM> is disposed on the discharging side of the welding device <NUM> for coiling the welded foil and composite current collector. The welded foil and composite current collector can be used as a substrate for an electrode plate and applied to the secondary battery.

According to the above description, the foil can be welded to the composite current collector by the processing apparatus, and the foil can act as a tab of the composite current collector such that the current in the battery cell is output through the connection of the foil and the composite current collector,.

The foil and the composite current collector may be laser-welded, but the present disclosure is not limited thereto. In the present embodiment, the foil and the composite current collector are ultrasonic-welded. At this time, the welding head <NUM> is configured as an ultrasonic welding head <NUM>. When the foil and the composite current collector arrive at the welding station, force is applied to the foil and the composite current collector by the vibration of the ultrasonic welding head <NUM>, and the foil and the composite current collector rub against each other and are fused together.

Ultrasonic welding can effectively penetrate the plastic layer in the middle of the composite current collector, and respectively fuse the foil with metal layers on both sides of the plastic layer so as to increase the thickness of the metal, such that the current in the battery cell can be reliably output from the fused portion.

During the ultrasonic welding process, the welding device <NUM> can also be configured to continuously weld the foil to a portion of the composite current collector at the welding station. That is, welding of the foil and the composite current collector can be completed during the conveying process, and the conveying process can be performed without a pause.

According to the invention, the ultrasonic welding head <NUM> and the anvil block <NUM> are respectively configured as cylinders so as to rotate with respect to each other, thereby achieving rolling contact. Thus, the foil and the composite current collector can be continuously conveyed to the welding station, and the foil and the composite current collector can be continuously welded. This aspect saves welding time and improves welding efficiency, and continuous welding marks can be formed on the foil and the composite current collector to ensure the reliability of the welding.

Further, the ultrasonic welding head <NUM> is provided with a plurality of extrusion welding teeth (not shown in the drawings) on its circumferential face. The extrusion welding teeth can be configured as a tapered tooth structure which is similar to a gear structure. The anvil block <NUM> can be surface smoothed to reduce damage to the foil and the composite current collector during welding. At this time, the ultrasonic welding head <NUM> serves as a welding tooth portion, and the anvil block <NUM> serves as a non-welding tooth portion.

During the welding process, the extrusion welding teeth extrude the foil and the composite current collector and penetrate the plastic layer of the composite current collector. The foil is stretched under the action of the pressing force of the extrusion welding teeth, and is respectively fused with the metal layers on the upper and lower sides of the plastic layer, and thus the foil can be welded more sufficiently with the composite current collector.

Of course, the extrusion welding teeth are not limited to being disposed on the circumferential face of the ultrasonic welding head <NUM>. Alternatively, the extrusion welding teeth may be disposed on the circumferential face of the anvil block <NUM>. Accordingly, the ultrasonic welding head <NUM> can be surface smoothed. In this case, the anvil block <NUM> serves as a welding tooth portion and the ultrasonic welding head <NUM> serves as a non-welding tooth portion.

As shown in <FIG>, the processing apparatus may further include a driving device <NUM>. One of the ultrasonic welding head <NUM> and the anvil block <NUM> may be coupled to the driving device <NUM> in a transmission way, such that the contact force generated when the ultrasonic welding head <NUM> is in contact with the anvil block <NUM> can be adjusted to ensure the welding quality. In the present embodiment, the driving device <NUM> can be a cylinder.

As mentioned above, both the foil and the composite current collector are made of thin materials, which may have low strength and may not withstand large tearing force. Therefore, it is required that the relative position of the foil and the composite current collector is maintained to be fixed during welding. Otherwise, cracks may occur after welding, and in severe cases, strip breakage may occur such that the production cannot be performed continuously.

Here, in order to ensure the welding quality, the processing apparatus further includes a first pressure roller <NUM> and a second pressure roller <NUM> disposed in pairs. The first pressure roller <NUM> is disposed on the discharging side of the foil uncoiling roller <NUM> and the feeding side of the welding device <NUM>, and the second pressure roller <NUM> is disposed on the discharging side of the composite current collector uncoiling roller <NUM> and on the feeding side of the welding device <NUM>.

The first pressure roller <NUM> and the second pressure roller <NUM> have a gap therebetween for the passage of the composite current collector and the foil, and the foil and the composite current collector may be overlapped in the gap.

In this way, before being welded, the foil and the composite current collector can be conveyed in the same direction within a certain length and jointly conveyed to the welding station in an overlapped state, so as to reduce the speed difference between them. In this way, the conveying speeds of them tend to be consistent to maintain their relative position to be fixed, thereby improving the welding quality of the foil and the composite current collector.

At least one of the first pressure roller <NUM> and the second pressure roller <NUM> may be configured to be rotatable, which can reduce the resistance of the foil and the composite current collector during the conveying process so as to ensure the smoothness of the conveying. In the present embodiment, the first pressure roller <NUM> and the second pressure roller <NUM> are both configured to be rotatable, and the rotation direction should match the conveying direction of the foil and the composite current collector. That is, the line speed directions of the first pressure roller <NUM> and the second pressure roller <NUM> should coincide with the conveying direction of the foil and the composite current collector.

In addition, at least one of the first pressure roller <NUM> and the second pressure roller <NUM> may also be coupled to a cylinder in a transmission way, so that the first pressure roller <NUM> and the second pressure roller <NUM> can approach or move far away from each other to adjust a gap therebetween.

Further, a pre-pressure roller <NUM> may be disposed on the feeding side of the first pressure roller <NUM> and the second pressure roller <NUM>. The pre-pressure roller <NUM> can press one of the foil and the composite current collector towards the other, such that the foil and the composite current collector are overlapped together before entering the gap between the first pressure roller <NUM> and the second pressure roller <NUM>, so as to reduce the tension difference and the speed difference therebetween, thereby leading to the higher flatness and the more accurate relative position when both of them enter the first pressure roller <NUM> and the second pressure roller <NUM>.

In an embodiment, the processing apparatus may further comprise a rectifying device <NUM>, and the rectifying device <NUM> is disposed on the feeding side of the pre-pressure roller <NUM>. The rectifying device <NUM> is configured to rectify the overlapping position of the foil and the composite current collector, so as to avoid a large position offset when they overlap.

According to an exemplary embodiment, the rectifying device <NUM> may be configured as a rectifying roller. The foil and the composite current collector are wrapped around the rectifying roller during the conveying process. The rectifying roller can control and drive the foil and the composite current collector to make a slight movement in a direction different from the conveying direction by a program in order to rectify the offset of the foil and the composite current collector during the conveying process, such that the overlapped foil and composite current collector can overlap at a predetermined position to meet dimensional requirements at the time of overlapping.

Further, a rectifying device <NUM> may also be provided on the feeding side of the coiling roller <NUM> to rectify the offset amount of a substrate for an electrode plate wound around the coiling roller <NUM>.

During the discharging process, it is also required to control the tension of the foil and the composite current collector. Therefore, the processing apparatus may further include a tension adjusting device, and the tension adjusting device may be configured as a tension adjusting roller. The tension adjusting roller is movably disposed in the conveying path of the foil and the composite current collector, and the tension adjusting roller can control actions by a program so as to achieve an object of adjusting the tension.

Claim 1:
A welding device (<NUM>) for a secondary battery current collector, comprising:
a welding head (<NUM>); and
an anvil block (<NUM>),
wherein a welding station is disposed between the welding head (<NUM>) and the anvil block (<NUM>), and
the welding head (<NUM>) is configured to weld a foil to a portion of a composite current collector at the welding station;
wherein the welding device (<NUM>) is configured to continuously weld the foil to the portion of the composite current collector at the welding station;
wherein the welding head (<NUM>) is configured as an ultrasonic welding head, the ultrasonic welding head being in rolling contact with the anvil block (<NUM>);
wherein the ultrasonic welding head and the anvil block (<NUM>) are respectively configured as cylinders so as to rotate with respect to each other; and
wherein a plurality of extrusion welding teeth is arranged on an outer circumferential face of one of the ultrasonic welding head (<NUM>) and the anvil block (<NUM>).