Battery cap assembly, secondary battery and battery module

The present disclosure provides a battery cap assembly, a secondary battery and a battery module. The battery cap assembly comprises: a cap plate, including a second terminal hole; a first electrode terminal, at least a part of which protruding above the cap plate; a second electrode terminal, including a second protruding portion protruding above the cap plate and a second base portion connected with the second protruding portion. The first electrode terminal is provided with a protrusion used for welding with a first connecting piece; the second protruding portion is used for welding with a second connecting piece to form a welding portion, and a projection of the welding portion in an up-down direction is positioned in a cross-section of the second base portion. The secondary battery comprises a case, an electrode assembly and the battery cap assembly. The battery module comprises the first connecting piece and the secondary batteries.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Chinese patent application No. CN201820044608.8, filed on Jan. 11, 2018, which is incorporated herein by reference in its entirety.

FIELD OF THE PRESENT DISCLOSURE

The present disclosure relates to the field of battery, and particularly relates to a battery cap assembly, a secondary battery and a battery module.

BACKGROUND OF THE PRESENT DISCLOSURE

At present, the secondary batteries of the battery module are generally connected by connecting pieces, and in the prior art, the connecting piece is generally fixed to an electrode terminal of the secondary battery by laser penetration welding; the laser penetration welding needs to have a sufficient welding depth to ensure the welding strength, so a thickness of a part of the electrode terminal protruding above the cap plate is not less than 2 mm, which leads to the electrode terminal and the connecting piece occupying a large space. The connecting piece also can be fixed to the electrode terminal by butt welding in the prior art, however, the butt welding requires that a protrusion should be provided on an upper surface of each of two electrode terminals, the protrusion is used for welding with the connecting piece; because the dimension tolerances of the secondary batteries accumulate, it is difficult to attach the connecting piece to the protrusions of two secondary batteries at the same time, cannot satisfy a requirement of gap between the connecting piece and the protrusion in the process of butt welding, and cannot connect the connecting piece to the protrusion accurately, which will lead to a low welding strength between the connecting piece and the protrusion, and affect the cycle life of the secondary battery.

SUMMARY OF THE PRESENT DISCLOSURE

In view of the problem existing in the background, an object of the present disclosure is to provide a battery cap assembly, a secondary battery and a battery module, which can reduce the height of the battery module and increase the cycle life of the battery module.

In order to achieve the above object, in a first aspect, the present disclosure provides a battery cap assembly, which comprises a cap plate, a first electrode terminal and a second electrode terminal. The cap plate includes a first terminal hole and a second terminal hole. At least a part of the first electrode terminal protrudes above the cap plate. The second electrode terminal includes a second protruding portion protruding above the cap plate and a second base portion connected with the second protruding portion, the second base portion extends into the second terminal hole, a cross-sectional area of the second protruding portion is larger than a cross-sectional area of the second terminal hole. A protrusion is provided on an upper surface of the first electrode terminal and used for welding with a first connecting piece; the second protruding portion is used for welding with a second connecting piece to form a welding portion, and a projection of the welding portion in an up-down direction is positioned in a cross-section of the second base portion. In an embodiment, the second base portion is connected with a bottom surface of the second protruding portion and extends downwardly.

In order to achieve the above object, in a second aspect, the present disclosure provides a secondary battery, which comprises a case, an electrode assembly and the battery cap assembly according to the first aspect of the present disclosure. The case has an opening in a top thereof. The battery cap assembly is fixed to the case and seals the opening of the case. The electrode assembly is received in the case and comprises a first electrode plate and a second electrode plate, the first electrode terminal is electrically connected with the first electrode plate, the second electrode terminal is electrically connected with the second electrode plate.

In order to achieve the above object, in a third aspect, the present disclosure provides a battery module, which comprises a first connecting piece, a second connecting piece and the secondary batteries according to the second aspect of the present disclosure. The first connecting piece includes a first connecting portion and a second connecting portion; the first connecting portion is attached to the upper surface of the first electrode terminal of the battery cap assembly of one secondary battery and welded with the protrusion of the first electrode terminal of the battery cap assembly of the one secondary battery, the second connecting portion is welded with the second protruding portion of the second electrode terminal of the battery cap assembly of another secondary battery to form the welding portion, and the projection of the welding portion in the up-down direction is positioned in the cross-section of the second base portion of the battery cap assembly of the another secondary battery.

The present disclosure has the following beneficial effects: in the battery cap assembly, the secondary battery and the battery module according to the present disclosure, the protrusion and the first connecting portion of the first connecting piece are arranged side by side, so the protrusion will not increase the height of the battery module; at the same time, the first connecting portion of the first connecting piece is fixed to the protrusion by butt welding, and there is no need to fix the first connecting portion of the first connecting piece to the upper surface of the first electrode terminal by laser penetration welding, which can lower the requirement of a thickness of the first electrode terminal, decrease the thickness of the first electrode terminal and save material, reduce the total height of the first electrode terminal and the first connecting piece assembled together, improve the energy density of the battery module. In addition, the second protruding portion of the second electrode terminal is directly connected with the second connecting portion by laser penetration welding, therefore, it only needs to ensure that the first connecting portion of the first connecting piece is fitted with the protrusion in the process of assembling the first connecting piece; even if the dimension tolerances of the secondary batteries accumulate, the second protruding portion of the second electrode terminal will not limit the positioning and assembling of the first connecting piece, which can ensure the connecting strength between the first connecting piece and two secondary batteries, and increase cycle life of the secondary battery and the battery module.

REFERENCE NUMERALS IN FIGURES ARE REPRESENTED AS FOLLOWS

DETAILED DESCRIPTION

Hereinafter a battery cap assembly, a secondary battery and a battery module according to the present disclosure will be described in detail in combination with the figures.

Firstly, a battery cap assembly according to a first aspect of the present disclosure will be described.

Referring toFIGS. 1-10, a battery cap assembly11according to the present disclosure comprises a cap plate111, a first electrode terminal112and a second electrode terminal113. The cap plate111includes a first terminal hole1111and a second terminal hole1112. At least a part of the first electrode terminal112protrudes above the cap plate111. The second electrode terminal113includes a second protruding portion1131protruding above the cap plate111and a second base portion1132connected with a bottom surface of the second protruding portion1131, the second base portion1132extends downwardly and extends into the second terminal hole1112, a cross-sectional area of the second protruding portion1131is larger than a cross-sectional area of the second terminal hole1112. A protrusion P is provided on an upper surface S1of the first electrode terminal112and used for welding with a first connecting piece2; the second protruding portion1131is used for welding with a second connecting piece3to form a welding portion M, and a projection of the welding portion M in an up-down direction Z is positioned in a cross-section of the second base portion1132. Preferably, the second connecting piece3is welded with a top surface of the second protruding portion1131, the top surface of the second protruding portion1131is a plane.

Because the cross-sectional area of the second protruding portion1131is larger than the cross-sectional area of the second terminal hole1112, the second protruding portion1131can be clamped above the second terminal hole1112, thereby avoiding the second protruding portion1131of the second electrode terminal113passing through the second terminal hole1112. A sealing member is provided between the second electrode terminal113and the second terminal hole1112.

Because the protrusion P is provided on the upper surface S1of first electrode terminal112, when the first electrode terminal112of the battery cap assembly11needs to be connected with the first connecting piece2, the protrusion P can be directly fixed to the first connecting piece2by butt welding; compared to the traditional laser penetration welding, the butt welding can effectively decrease the heat generated in the process of welding, avoid the sealing member between the first electrode terminal112and the cap plate111being damaged by high temperature.

When the second electrode terminal113of the battery cap assembly11needs to be connected with the second connecting piece3, the second protruding portion1131of the second electrode terminal113can be directly fixed to the second connecting piece3by laser penetration welding. Because the projection of the welding portion M formed by welding the second protruding portion1131and the second connecting piece3in the up-down direction Z is positioned in the cross-section of the second base portion1132, and the second base portion1132has a large thickness (the second base portion1132needs to pass through the second terminal hole1112, so it has a large thickness), the welding portion M may extend to the second base portion1132in the process of laser penetration welding, thereby ensuring welding depth of the laser penetration welding and connecting strength between the second electrode terminal113and the second connecting piece3. The second base portion1132can be applied to the laser penetration welding, so a thickness of the second protruding portion1131protruding above the cap plate111can be decreased, thereby reducing an entire height of the battery cap assembly11.

The first connecting piece2can be used for connecting the first electrode terminal112of a first one of the battery cap assemblies11and a second electrode terminal113of a second one of the battery cap assemblies11, so as to electrically connect the two battery cap assemblies11. Similarly, the second connecting piece3can be used for connecting the second electrode terminal113of the first one of the battery cap assemblies11and the first electrode terminal112of a third one of the battery cap assemblies11, so as to electrically connect the two battery cap assemblies11. The first connecting piece2and the second connecting piece3are the same.

For example, when one first connecting piece2needs to connect the first electrode terminal112of the first one of the battery cap assemblies11and the second electrode terminal113of the second one of the battery cap assemblies11, the first connecting piece2can be connected with the second protruding portion1131of the second electrode terminal113of the second one of the battery cap assemblies11by laser penetration welding, and the welding position is flexible, so it only needs to ensure that the first connecting piece2is fitted with the protrusion P of the first one of the battery cap assemblies11in the process of assembling the first connecting piece2, even if there is a dimension tolerance between the two battery cap assemblies11, the second electrode terminal113of the second one of the battery cap assemblies11will not limit the positioning and assembling of the first connecting piece2, which can ensure the connecting strength between the first connecting piece2and the two battery cap assemblies11.

Referring toFIG. 3, the first electrode terminal112includes a first protruding portion1121protruding above the cap plate111and a first base portion1122connected with a bottom surface of the first protruding portion1121, the first base portion1122extends downwardly and extends into the first terminal hole1111. A top surface of the first protruding portion1121is acted as the upper surface S1of the first electrode terminal112, a cross-sectional area of the first protruding portion1121is larger than a cross-sectional area of the first terminal hole1111. Because the cross-sectional area of the first protruding portion1121is larger than the cross-sectional area of the first terminal hole1111, the first protruding portion1121can be clamped above the first terminal hole1111, thereby avoiding the first protruding portion1121of the first electrode terminal112passing through the first terminal hole1111. Another sealing member can be provided between the first electrode terminal112and the first terminal hole1111.

A cross-section of the first protruding portion1121, a cross-section of the first base portion1122, a cross-section of the second protruding portion1131, the cross-section of the second base portion1132, a cross-section of the first terminal hole1111and a cross-section of the second terminal hole1112are cross-sections perpendicular to the up-down direction Z, and the cross-sectional area is area of the section perpendicular to the up-down direction Z.

The cap plate111can be made of insulating material.

The first electrode terminal112is a negative electrode terminal and made of copper, the second electrode terminal113is a positive electrode terminal and made of aluminum, and a cross-sectional area of the first base portion1122is smaller than the cross-sectional area of the second base portion1132.

The battery cap assembly11according to the present disclosure is generally applied to a later mentioned secondary battery1, the second electrode terminal113(positive electrode terminal) and the first electrode terminal112(negative electrode terminal) can transfer the electric energy of the secondary battery1to outside via a positive electrode plate (a later mentioned second electrode plate) and a negative electrode plate (a later mentioned first electrode plate) respectively. Considering electrochemistry, a current collector of the positive electrode plate is formed by aluminum foil, and a current collector of negative electrode plate is formed by copper foil. It is difficult to connect aluminum and copper by laser welding, so in order to ensure the connecting strength between the first electrode terminal112and the negative electrode plate and the connecting strength between second electrode terminal113and the positive electrode plate, the first electrode terminal112is preferably made of copper, the second electrode terminal113is preferably made of aluminum.

Because the protrusion P is provided on the upper surface S1of the first electrode terminal112, when the first electrode terminal112of the battery cap assembly11needs to be connected with the first connecting piece2, the protrusion P can be directly fixed to the first connecting piece2by butt welding; compared to the traditional laser penetration welding, the butt welding can effectively decrease the heat generated in the process of welding and avoid the sealing member between the first electrode terminal112and the cap plate111being damaged by high temperature. In addition, compared to aluminum, copper needs more energy and generates more heat in the process of welding, so the first electrode terminal112made of copper needs to choose the butt welding generating few heat. In addition, because electrical resistance of copper is lower than electrical resistance of aluminum, based on the premise that the overcurrent ability of the first electrode terminal112and the overcurrent ability of the second electrode terminal113are consistent, the cross-sectional area of the first base portion1122of the first electrode terminal112can be decreased, which can reduce weight of the secondary battery1and improve energy density. At the same time, the price of copper is higher than the price of aluminum, so it can save amount of copper and reduce cost.

In the up-down direction Z, both of a thickness of the first protruding portion1121and the thickness of the second protruding portion1131range from 0.01 mm to 2 mm, preferably, the thickness of the first protruding portion1121is equal to the thickness of the second protruding portion1131. The protrusion P is provided on the first protruding portion1121, and there is no need to weld the first protruding portion1121and the first connecting piece2, so the first protruding portion1121can have a small thickness. Because the projection of the welding portion M formed by welding the second protruding portion1131and the second connecting piece3in the up-down direction Z is positioned in the cross-section of the second base portion1132, the second protruding portion1131can have a small thickness.

Shape of the protrusion P depends on actual demand, for example, the protrusion P is in the shape of stripe. Specifically, in an embodiment, referring toFIG. 8, a cross-section of the protrusion P is a rectangle and the protrusion P extends along a transverse direction X of the cap plate111, a width of the protrusion P in a longitudinal direction Y ranges from 0.5 mm to 3 mm. In another embodiment, referring toFIG. 10, the cross-section of the protrusion P is a rectangle and the protrusion P extends along the longitudinal direction Y, a width of the protrusion P in the transverse direction X ranges from 0.5 mm to 3 mm.

The protrusion P also can be provided on different positions of the upper surface S1, for example, the protrusion P can be positioned in a middle part of the upper surface S1or at an edge of the upper surface S1.

Secondly, a secondary battery according to a second aspect of the present disclosure will be described.

Referring toFIGS. 1-10, a secondary battery1according to the present disclosure comprises a case12, an electrode assembly13and the battery cap assembly11according to the first aspect of the present disclosure. The case12has an opening in a top thereof. The battery cap assembly11is fixed to the case12and seals the opening of the case12, the first electrode terminal112and the second electrode terminal113are fixed to the cap plate111. The electrode assembly13is received in the case12and comprises the first electrode plate and the second electrode plate, the first electrode terminal112is electrically connected with the first electrode plate, the second electrode terminal113is electrically connected with the second electrode plate.

Referring toFIG. 2, the secondary battery1can be a prismatic rechargeable battery; certainly, the secondary battery1also can have other shapes. Correspondingly, the case12can have a hexahedral shape, a cavity is formed in the case12, and the electrode assembly13can be assembled into the case12via the opening of the case12.

The electrode assembly13further comprises a separator separating the first electrode plate and the second electrode plate. The first electrode plate and the second electrode plate are opposite in polarity. Each of the first electrode plate and the second electrode plate comprises the current collector and an active material coated on the surface of the current collector, the current collector can be metal foil.

The first electrode terminal112extends into the case12via the first terminal hole1111, and is electrically connected with the electrode assembly13in the case12; the second electrode terminal113extends into the case12via the second terminal hole1112, and is electrically connected with the electrode assembly13in the case12.

Preferably, the first electrode plate is the negative electrode plate, and the current collector of the first electrode plate is made of copper in general; correspondingly, the second electrode plate is the positive electrode plate, and the current collector of the second electrode plate is made of aluminum in general. Because it is difficult to welding different metals, especially copper and aluminum, the first electrode terminal112is preferably made of copper and the second electrode terminal113is preferably made of aluminum.

The first electrode plate can be electrically connected with the first electrode terminal112via an adapter piece, the second electrode plate can be electrically connected with the second electrode terminal113via another adapter piece. The cap plate111is preferably made of the insulating material, so the two adapter pieces can be directly attached to the cap plate111, and there is no need to provide an insulating member between the cap plate111and the adapter piece, which can save space.

Finally, a battery module according to a third aspect of the present disclosure will be described.

Referring toFIGS. 1-10, a battery module according to the present disclosure comprises a first connecting piece2, a second connecting piece3and the secondary batteries1according to the second aspect of the present disclosure. The first connecting piece2includes a first connecting portion21and a second connecting portion22; the first connecting portion21is attached to the upper surface S1of the first electrode terminal112of the battery cap assembly11of one secondary battery1and welded with the protrusion P of the first electrode terminal112of the battery cap assembly11of the one secondary battery1, the second connecting portion22is welded with the second protruding portion1131of the second electrode terminal113of the battery cap assembly11of another secondary battery1to form the welding portion M, and the projection of the welding portion M in the up-down direction Z is positioned in the cross-section of the second base portion1132of the second electrode terminal113of the battery cap assembly11of the another secondary battery1.

The secondary batteries1are arranged in a row, two adjacent secondary batteries1can be electrically connected by one connecting piece (such as the first connecting piece2).

The process of assembling the battery module is as follows: firstly, arranging the secondary batteries1in a row; secondly, attaching the first connecting portion21of the first connecting piece2to the upper surface S1and the protrusion P of the first electrode terminal112of the battery cap assembly11of one secondary battery1, and attaching the second connecting portion22to the top surface of the second protruding portion1131of the second electrode terminal113of the battery cap assembly11of another secondary battery1; thirdly, referring toFIG. 4, welding along a contacting boundary between the first connecting portion21and the protrusion P, thereby fixing the first connecting piece2to the one secondary battery1; referring toFIG. 5, connecting the second connecting portion22with the second protruding portion1131of the second electrode terminal113of the battery cap assembly11of the another secondary battery1directly by laser penetration welding; finally, repeating aforementioned steps, and circularly welding a plurality of connecting pieces (such as the second connecting piece3, a third connecting piece and the like) to connect all the secondary batteries1.

In the battery module according to the present disclosure, the protrusion P and the first connecting portion21of the first connecting piece2are arranged side by side, so the protrusion P will not increase the height of the battery module; at the same time, the first connecting portion21of the first connecting piece2is fixed to the protrusion P by butt welding, and there is no need to fix the first connecting portion21of the first connecting piece2to the upper surface S1of the first electrode terminal112by laser penetration welding, which can lower the requirement of a thickness of the first electrode terminal112, decrease the thickness of the first electrode terminal112and save material, reduce the total height of the first electrode terminal112and the first connecting piece2assembled together, improve the energy density of the battery module. In addition, the second protruding portion1131of the second electrode terminal113is directly connected with the second connecting portion22by laser penetration welding, therefore, it only needs to ensure that the first connecting portion21of the first connecting piece2is fitted with the protrusion P in the process of assembling the first connecting piece2; even if the dimension tolerances of the secondary batteries1accumulate, the second protruding portion1131of the second electrode terminal113will not limit the positioning and assembling of the first connecting piece2, which can ensure the connecting strength between the first connecting piece2and two secondary batteries1, and increase cycle life of the secondary battery1and the battery module.

Preferably, the first electrode terminal112is made of copper, the second electrode terminal113is made of aluminum, and the cross-sectional area of the first base portion1122is smaller than the cross-sectional area of the second base portion1132.

The protrusion P is provided on the upper surface S1of the first electrode terminal112and fixed to the first connecting portion21of the first connecting piece2by butt welding; compared to the traditional laser penetration welding, the butt welding can effectively decrease the heat generated in the process of welding and avoid the sealing member between the first electrode terminal112and the cap plate111being damaged by high temperature. In addition, compared to aluminum, copper needs more energy and generates more heat in the process of welding, so the first electrode terminal112made of copper needs to choose the butt welding generating few heat.

Because the electrical resistance of copper is lower than the electrical resistance of aluminum, based on the premise that the overcurrent ability of the first electrode terminal112and the overcurrent ability of the second electrode terminal113are consistent, the cross-sectional area of the first base portion1122of the first electrode terminal112can be decreased, which can reduce weight of the secondary battery1and improve energy density. At the same time, the price of copper is higher than the price of aluminum, so it can save amount of copper and reduce cost.

Referring toFIG. 7andFIG. 9, a side surface of the first connecting portion21of the first connecting piece2can be directly attached to the protrusion P, and the welding is along the contacting boundary between the first connecting portion21and the protrusion P

Certainly, referring toFIG. 1andFIG. 6, the first connecting portion21preferably includes a through-hole211fitted with the protrusion P of the one secondary battery1, the protrusion P of the one secondary battery1can be fixed to the through-hole211by laser welding. By providing the through-hole211, it can increase a length of welding seam between the first connecting portion21and the protrusion P, and improve welding strength.

Referring toFIG. 5, the second connecting portion22is fixed to the second protruding portion1131of the second electrode terminal113of the battery cap assembly11of the another secondary battery1by laser penetration welding and forms the welding portion M, the projection of the welding portion M in the up-down direction Z is positioned in the cross-section of the second base portion1132of the second electrode terminal113of the battery cap assembly11of the another secondary battery1, in other words, in the process of laser penetration welding, a position emitting the laser faces the second base portion1132in the up-down direction Z. Because the second base portion1132needs to pass through the second terminal hole1112, it has a large thickness; in order to reduce the height of the secondary battery1, the thickness of the second protruding portion1131protruding above the cap plate11needs to be decreased maximally. In order to ensure the connecting strength between the second connecting portion22and the second electrode terminal113, the welding depth of the laser penetration welding needs to be sufficient; if the welding portion M is formed at an edge of the second protruding portion1131beyond the second base portion1132, the second protruding portion1131may be melted through in the process of welding, which will damage the sealing member and the cap plate111, lead to low welding strength. Therefore, in the process of laser penetration welding, the position emitting the laser needs to face the second base portion1132in the up-down direction Z, so that the projection of the welding portion M in the up-down direction Z is positioned in the cross-section of the second base portion1132, and ensures welding strength.

A thickness of the first connecting piece2is equal to a height of the protrusion P of the one secondary battery1in the up-down direction Z, so the protrusion P will not increase the height of the battery module.

Referring toFIG. 1andFIG. 6, the first connecting piece2further includes a third connecting portion23in the shape of arch, the third connecting portion23connects the first connecting portion21and the second connecting portion22. The third connecting portion23in the shape of arch can adjust a height difference between the first connecting portion21and the second connecting portion22in the up-down direction Z.