US20090297941A1

US20090297941A1 - Type of secondary battery

Info

Publication number: US20090297941A1
Application number: US11/648,014
Authority: US
Inventors: Xi Shen; Lei Han
Original assignee: Shanghai BYD Co Ltd
Current assignee: Shanghai BYD Co Ltd
Priority date: 2005-12-30
Filing date: 2006-12-30
Publication date: 2009-12-03
Also published as: CN100573978C; EP1973182A4; CN1992392A; EP1973182A1; EP1973182B1; US7923139B2; JP5037527B2; WO2007076693A1; ATE535950T1; US20090148766A1; KR100993645B1; KR20080075229A; JP2009522714A

Abstract

This invention describes a type of secondary batteries. The bottom of the secondary battery is installed with a safety device that includes a conductive current interrupting device (CID) and a support component. In installing the safety device on the bottoms of the batteries, the batteries' manufacturing processes are simplified, their production costs are lowered, and the space utilization inside of the battery is increased. In addition, the battery manufacturing process can use sealed or unsealed methods.

Description

CROSS REFERENCE

This application claims priority from a Chinese patent application entitled “Secondary Battery” filed on Dec. 30, 2005 having a Chinese Application No. 200510121325.6. Said application is incorporated herein by reference.

FIELD OF INVENTION

This invention relates to a type of secondary batteries, and, in particular to a type of secondary batteries that have a safety device installed in the battery.

BACKGROUND

As a type of high capacity power supply, secondary batteries are increasingly and widely used in a variety of fields. When ordinary secondary batteries are used under unusual circumstances such as when machines are being pressed, bounced around, subjected to high temperatures, self short-circuited, or over-charged, the inside of the batteries may accumulate a large amount of heat in a matter of split seconds. Internal pressure may increase sharply. In more serious situations, the battery may emit smoke, catch on fire, or explode. These kinds of safety-related accidents could even endanger personal safety and create huge economic losses. As a result, people have increasingly demanded safer secondary batteries.
In general, traditional secondary batteries do not have special safety features installed. They depend on external protection circuits to achieve the protection function. This limits the batteries from being applied a greater range of use. In order to satisfy users' demands for safer secondary batteries, some designers carved out or applied pressure to definite a concave-shaped groove that forms a weak area. The groove's resistance to pressure is weaker when compared to other areas on the surface of the battery. When the battery's internal pressures increases under unusual circumstances, the groove would be damaged first, preventing the battery from catching on fire, exploding, or incurring other safety issues. However, the manufacturing of the groove becomes increasingly difficult due to limitations in the surface material of the battery and due to increased difficult the manufacturing process of the groove. It is also difficult to ensure that the groove's thickness is even. Furthermore, it is extremely difficult to ensure that the thickness of the battery groove corresponds with the design specification for bearing maximum internal pressure from the battery, such that when the internal pressure of the battery reaches this design specification, the groove would break.
The cylindrical-shaped lithium ion batteries that are currently commercially available commonly have installed between the positive electrode tab and the positive lead to the positive terminal a circuit interrupt device (“CID”) or a PTC (positive temperature sensitive component). When the battery is in an abnormal condition, internal pressure increases inside the battery (rising temperature) and the safety device is activated, thus preventing any dangerous situations from occurring. However, these two designs have the following drawbacks:
1. When the battery is in the process of discharging a large amount of electrical current, its temperature will clearly rise and will activate the positive temperature sensitive component and prevent the battery from functioning properly. Thus, its usage in high-rate batteries is limited.
2. The batteries available now have the CID installed on the positive terminal end (the open end of the battery shell case). This kind of component relies on pressure to activate and therefore it needs to be sealed completely. Thus, the battery can only be manufactured using the sealing method. The end result is that the internal pressure is greater and this can be an unsafe factor.
3. Since the batteries available now have CID installed on the positive terminal end (the open end of the battery shell case), insulation must be used to separate the positive and negative electrodes in order to prevent short-circuiting. Furthermore, these kinds of installation must have supporting components within the battery. Otherwise, the battery cannot be used properly. This leaves only the pressing method for sealing the opening. Batteries sealed using this method can lead to various problems such as liquid leakage, environmental pollution, and decreased battery life.

SUMMARY

The technical problem to be solved by the current invention is: to provide a type of secondary battery having a safety device installed on the bottom of the battery.
In order to resolve this technical problem, the present invention provides a type of secondary battery, including a cylindrical-shaped shell with a battery core and electrolyte sealed in the shell; at one end of the battery shell is a sealed end and at the other end, after filling the battery core and electrolyte, it is sealed by an end cover. The battery core includes a positive electrode plate, a negative electrode plate, a positive tab, and a negative tab. Between the surface of the bottom inside of the shell and the battery core, there is a safety device. Between the safety device and the battery core, there is installed a CID; the safety device includes a conductive circuit interrupt component (“CID”) and a non-conductive support component having an appropriate height. The CID includes a support piece and a solder attachment position. The support piece supports the CID on the support component, and the solder attachment position of the CID of the safety device is soldered on the surface of the inner bottom of the battery shell. One of the positive electrode tab or the negative electrode tab of the battery core is electrically connected to the support piece of the CID of the safety device. There is insulation material between the described positive and negative electrode plates, and between the tabs having the same polarity as the described battery shell.
In the second battery of the present invention, the conductive CID of the safety device is supported on the support component, and the solder attachment position of the CID is soldered to the surface of the inner bottom of the shell. When the internal pressure of the battery rises, the CID body is stretched. When the stretching exceeds certain limit, the CID body would break, or the solder attachment position of the CID would break with the solder structure at the bottom of the shell, causing the CID to separate from the bottom of the battery shell, achieving the current interrupt function, avoiding the internal pressure from rising further and causing a safety problem.

DESCRIPTION OF THE FIGURES

The following figures illustrate the embodiments of the invention.

FIG. 1 illustrates a cross sectional view of a type of embodiment of the secondary battery of this invention.

FIG. 2 is a 3-D illustration of the safety device 16 of FIG. 1.

FIG. 3 is a top-view illustration of the safety device 16 of FIG. 1.

FIG. 4 is a cross sectional view A-A of FIG. 2.

FIG. 5 illustrates a cross sectional view of the safety device of another type of embodiment of the secondary battery of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The secondary battery of this invention, the safety device is fixed between the bottom of the cylindrical battery shell and the battery core. The support piece of the CID of the safety device supports the CID on the support component of the safety device. The solder attachment position of the CID of the safety device is soldered to the surface of the inner bottom of the cylindrical battery shell. Installing of the safety device on the bottom of the battery does not limit the manufacturing process of the battery, where the manufacturing process may adopt either a sealing process for the opening or an open-ended process for the opening. Not limited by the sealing method of choice, the compress seal method or other sealing method, e.g. weld-seal, may be used to avoid leaking electrolyte.
The support method for the supporting piece to support the CID of the safety device on the support component can be by securing the support piece onto the support component and thereby supporting the CID on the support component. It can also be by securing the support piece between the support component and the non-conducting piece, thereby supporting the CID onto the support component. The preferred support method is to secure the support piece between the support component and the non-conducting piece.
The CID device can employ an upside-down L-shaped hook piece (the cross-section of the longitudinal portion is the upside-down L-shape). In this situation, the horizontal portion of the upside-down L-shaped CID can be the support piece and can be squeezed tight between the support component and the non-conductive piece. The free end of the vertical portion of the upside-down L-shaped CID can be the soldering position soldering on to the surface of the inner bottom of the battery shell. Or, the CID device can employ an L-shaped hook piece (the cross-section of the longitudinal portion is the L-shape). In this situation, the free end of the lengthwise portion of the L-shaped CID can be the support piece, where the solder attachment position is placed on the horizontal portion of the L shaped CID. With respect to upside-down L shaped or L shaped CID, the solder attachment position is on the surface of the inner bottom of the battery shell, preferably near the middle of the surface of the inner bottom of the battery shell.
The safety device can place many L-shaped or upside down L-shaped CIDs or a mix combination of L-shaped or upside-down L-shaped CIDs.
The CID can employ a groove (or slot) structure, where the exterior of the bottom of the groove structure of the CID is used as solder attachment position being soldered on the surface of the inner bottom of the battery shell. The support piece can be the groove wall of the groove structure of the CID or an extension arm extended from the groove wall. The preferred extension arm of the groove-shaped CID is the top portion of the groove wall turned directed to outside of the groove to a horizontal position.
The CID can also use a funnel-shaped structure where the support piece is a cantilever extending out from the funnel body of the CID, and the solder attachment position is at the exterior surface of the bottom of the funnel-shaped CID. The preferred embodiment for the cantilevel of the funnel-shaped CID is the top portion of the funnel wall extending toward exterior of the funnel to a horizontal position.
For a CID using the funnel-shaped structure, through-holes can be made on the funnel wall of the body of the funnel-shaped CID, the purpose being so that when the internal pressure raises in the battery, the pressure is also applied to the inner bottom surface of the battery shell which is soldered to the solder attachment position of the CID. The inner bottom surface of the battery shell can have a stretching effect on the CID. In this manner, the funnel wall of the CID is stretched due to increase in the internal pressure of the battery. At the same time, the inner bottom surface of the battery shell which is soldered to the solder attachment position of the CID can have an even greater stretching effect on the CID; the CID would have an increased sensitivity to increases in the internal pressure of the battery, thereby achieving a good circuit-cutoff and safety protection effect.
The thickness of the support piece is not less than 0.2 mm, and the range of the thickness of the solder attachment position of the CID is 0.05-0.3 mm.
The platform structure of the support component being able to achieve support function can employ many support components. The preferred support component has a ring-shaped structure. There is appropriate height between the two faces of the ring-shaped support component; the solder attachment position of the CID threads through the cavity of the ring-shaped structure of the support component and solders on the surface of the inner bottom of the battery shell.
The method for circuit cut-off for the safety device can be designed according to need. When the strength of the solder holding the solder attachment position of the CID and the surface of the inner bottom of the battery shell is greater than the stretching resistance of the CID, when the internal pressure of the battery raises to the preset limit, the CID body would break first causing the internal battery current path to break; and there would be no damage to the solder structure holding the solder attachment position of the CID and the surface of the inner bottom of the battery shell. When the strength of the solder holding the solder attachment position of the CID and the surface of the inner bottom of the battery shell is smaller than the stretching resistance of the CID, and when the internal pressure of the battery rises to the preset limit, there would be damage to the solder structure holding the solder attachment position of the CID and the surface of the inner bottom of the battery shell, and there would be separation between the CID and the inner bottom of the battery shell causing the internal battery current path to break, but the CID is not damaged.
The secondary battery of the present invention places a safety device at the bottom of the battery, where such structure is simple and would not hinder the manufacturing process of the battery or its sealing method.

Embodiment One

FIGS. 1-4 illustrates one embodiment of the secondary battery of the invention.
Such secondary battery includes safety device 16, battery shell 11, battery core 12, top seal ring 13, bottom seal ring 14, cover plate structure 15, and electrolyte (not show in figures). The battery shell 11, being made from a metal material and having a hallow cylindrical shape, forms a single body with the shell bottom and the top is sealed by the cover plate structure 15. The cross section of the cavity of the shell body 11 and the cross section of the safety device 16 are circular with equivalent radiuses. The top seal ring 13 and bottom seal ring 14 are made from insulation material.
The safety device 16 is installed between the bottom of the battery shell body 11 and the bottom seal ring 14, and the safety device includes the conductive funnel-shaped CID 161 and the circular-shaped non-conductive support component 162 supporting the CID 161. The cross section of the cavity of the shell body 11 and the cross section of the support component 162 are circular with equivalent radiuses.
CID 161 includes the funnel-shaped body 163 and the circular support piece 164 formed and extended horizontally from the funnel-shaped body 163. The solder attachment position is on the surface of the bottom of the funnel-shaped body 163. The surface of the bottom of the funnel-shaped CID body 163 of the CID 161 is solder on the surface of the inner bottom of the battery shell. To improve the sensitivity of the safety device 16 to the raising internal battery pressure, there are holes 165 provided on the funnel wall of the funnel-shaped body 163 of the CID 161.
The support component 162 is in a ring shaped structure and has on its top surface installed a groove having similar shape and measurement as that of the support piece 164. The depth of the groove is equal to the thickness H1 of the support piece 164. The height H3 of the support component 162 equals to the perpendicular distance from the top of the support piece 164 to the surface of the bottom of the funnel shaped body 163. The support piece 164 of the safety device 16 is squeezed tight between the shell bottom and the bottom seal ring.
The thickness H1 of the support piece 164 is not less than 0.2 mm. The thickness H2 of the solder attachment position of the CID 161 is 0.05-0.3 mm.
The battery core 12 includes positive electrode plate 17, negative electrode plate 18, and membrane 19.
The positive electrode plate 17 is a positive collector manufactured from belt-shaped metal foil such as aluminum foil, where at least on one side of the positive collector is smeared and covered with positive active material layer. The positive active material layer includes cobalt oxide lithium-ion (as main ingredient), positive adhesive paste, and positive conductive electrical material. The positive tab 171 through soldering is fixed on one side of the positive electrode plate 17.
The negative electrode plate 18 is a negative collector manufactured from belt-shaped metal foil such as copper foil, where at least on one side of the negative collector is smeared and covered with negative active material layer. As negative active material layer, it may include carbon material that may be used as negative active material, negative adhesive paste, and negative conductive electrical material. The negative tab 181 electrically connected to one side of the negative electrode plate 17. There is insulation material between the negative electrode plate 18 and the inside wall of the shell body 11 in order to insulate the two.
The separator membrane 19 is made of insulation material that is porous, preferably from a combination of chemical compounds such as concentrated polyethylene and polypropylene.
Electrolyte includes lithium compounds (for example, LiPF6) and mixed liquid solutions (dissolvent that is mixed with the appropriate ratio such as EC, DMC, EMC and PC).
The top portion of positive tab 171 is in proportion with the upward protruding battery core 12. The bottom portion of negative tab 181 is in proportion with the downward protruding battery core 12.
The battery core 12 is contained in the shell body 11.
On the upper portion of the battery core 12, the cover plate component 15 is installed on the open end of the shell body 11 such that it tightly seals the battery.
The cover plate component 15 includes the cover plate 151, an insulation component 152, and a rivet 153. The sealed structure of the cover plate 151 and the shell case 11 are formed by laser welding. The rivet 153 through the insulation component 152 is insulated from the cover plate 151, and is electrically connected to the positive tab 171 of the battery core 12 to become the positive terminal.
The top separator ring 13 is fitted on top between the battery core 12 and the cover plate component 15. The purpose of installing the bottom separator ring 14 in between the battery core 12 and the safety device 16 is to prevent short-circuiting resulting from simultaneous contact between the positive and negative electrodes and the cover plate component 15 and between the CID 161 of the safety device 16 and the positive and negative electrodes of the battery core 12.
The negative electrode plate 18 through the negative tab 181 protruding from the lower portion of the battery core 12 is electrically connected with the supporting piece 164 of the safety device 16. The bottom portion of the shell 11 is welded on the bottom surface of the funnel-shaped body 163. As such, the negative tab 181 is electrically connected with the shell 11 and the in-between bottom area. The case bottom acts as the battery's negative terminal.
The positive tab 171 which extends from the battery cell 12 is welded onto the supporting piece 164 of the safety device 16.
When the internal pressure of the battery 10 rises, due to the increased pressure from the electrolyte and the gas inside the battery, the CID 161 would be impacted by the stretching effect. When the internal pressure rises to a certain level, the soldering structure that holds the welding between the bottom surface of funnel-shaped CID 161 and the bottom of shell case 11 is damaged. The bottom part of funnel-shaped body 163 will separate from the bottom of shell case 11. It will then cause a cut off of the current, preventing accidents from happening.

Embodiment Two

The difference between embodiment two and embodiment one is that embodiment two uses another type of safety device.
FIG. 5 illustrates a portion of the safety device of embodiment two. The difference between this safety device and the safety device 16 in embodiment one is that it uses an inversed (or reversed or upside-downed) L-shaped CID 166 in the place of the CID 161 in embodiment one. FIG. 5 only shows a part of the vertical cross section of the supporting component 167.
Using the horizontal portion of the inversed L-shaped CID 166 as the supporting piece, the free-end of the vertical portion of the inversed L-shaped CID 166 is used as the solder attachment position for installation. The surface of the horizontal portion of the supporting component 167 is fitted with a groove that has appropriate measurements and shapes that are compatible with the inversed L-shaped CID 166. The depth of the groove is equal to the thickness of the horizontal portion of the inversed L-shaped CID 166. The height H5 of supporting component 167 is equal to the height H4 of the CID 166.
The negative electrode tab 181 is welded to the horizontal portion of the inversed L-shaped CID. The free-end of the vertical portion of the reversed L-shaped CID 166 is welded at the center of the bottom inner surface of the battery shell case.
When the internal pressure inside the battery goes up and due to the increased pressure from the electrolyte and gas inside the battery, the CID 166 would be impacted with this stretching effect. When the internal pressure rises to a certain degree, the welded structure holding the free-end of the vertical portion of the inversed L-shaped CID 166 and the area in between the bottom inner surface of the battery shell case would be damaged. CID 166 will separate from the bottom of the battery shell case, thus causing current interruption and preventing safety accidents.
In accordance with the breakage strength of the CID 166, two or more CIDs 166 can be evenly placed on the circumference of the ring-shape structure of the supporting piece 167 in accordance with the practical situation such as the internal battery pressure, etc.
While the present invention has been described with reference to certain preferred embodiments, it is to be understood that the present invention is not limited to such specific embodiments. Rather, it is the inventor's contention that the invention be understood and construed in its broadest meaning as reflected by the following claims. Thus, these claims are to be understood as incorporating not only the preferred embodiments described herein but all those other and further alterations and modifications as would be apparent to those of ordinary skilled in the art.

Claims

1. (canceled)

2. A secondary battery, comprising:

a battery shell having a first end and a second end, wherein said first end is sealed and said second end is sealed by a cover structure;

a battery core encased in said battery shell, wherein said battery core having a positive electrode, a negative electrode, a positive tab, and a negative tab;

electrolyte provided inside said battery shell; and

a safety device disposed within said battery shell, where said safety device has a conductive CID, and a non-conductive support component, wherein said support component comprises a support piece, and a solder attachment position;

wherein said support piece supports the CID on said support component, and wherein said solder attachment position being soldered in said battery shell.

3. A secondary battery of claim 2 wherein said battery shell have a top end and a bottom end and said first end is said bottom end, and said bottom end having an inner surface; wherein said solder attachment position is soldered on to the inner surface of the bottom end of the battery shell.

4. A secondary battery of claim 2 wherein there is an insulation component between said battery core and said CID; wherein said support piece is squeezed tight between said support component and said insulation component to support said CID on said support component.

5. A secondary battery of claim 2 wherein the cross-section of the CID is an inversed L-shape having a horizontal portion and a vertical portion, wherein the horizontal portion is the support piece and the vertical portion is the solder attachment position.

6. A secondary battery of claim 2 wherein said CID has a groove shaped structure having a bottom and a groove wall, wherein said solder attachment position is at the bottom of the groove shaped structure, and wherein the groove wall is the support piece.

7. A secondary battery of claim 7 wherein said support piece is an arm extending from the groove shaped structure.

8. A secondary battery of claim 2 wherein the CID has a funnel-shaped body.

9. A secondary battery of claim 8 wherein the support piece is a cantilever extending from the funnel-shaped body.

10. A secondary battery of claim 8 wherein the solder attachment position is at the funnel-shaped body.

11. A secondary battery of claim 8 wherein there are through-holes on the funnel-shaped body.

12. A secondary battery of claim 8 wherein the thickness of the support piece is greater than or equal to 0.2 mm and the thickness of the bottom portion of the funnel-shaped body is 0.01 mm to 1 mm.

13. A secondary battery of claim 8 wherein the thickness of the bottom portion of the funnel-shaped body is 0.05 mm to 0.3 mm.

14. A secondary battery of claim 2 wherein the support component is a ring shaped structure.

15. A secondary battery of claim 14 wherein the solder attachment position attaches through the ring shaped structure of the support component to the battery shell.

16. A secondary battery of claim 2 wherein the strength of the solder structure between the solder attachment position and the shell is greater than the stretching strength of the CID.

17. A secondary battery of claim 2 wherein the strength of the solder structure between the solder attachment position and the shell is less than the stretching strength of the CID.

18. A secondary battery, comprising:

a battery shell having a top end and a bottom end, wherein said bottom end has an inner surface;

electrolyte provided inside said battery shell;

a safety device disposed within said battery shell, wherein said safety device has a conductive CID, and a non-conductive support component, wherein said support component comprises a support piece, and a solder attachment position, wherein the support component is a ring shaped structure, wherein said support piece is fixed on said support component to support said CID on said support component, and wherein the solder attachment position is soldered on to the inner surface of the bottom end of the battery shell; and

an insulation component disposed between said battery core and said CID, wherein said support piece is squeezed tight between said support component and said insulation component to support said CID on said support component.

19. A secondary battery of claim 18 wherein the cross-section of the CID is an inversed L-shape having a horizontal portion and a vertical portion, wherein the horizontal portion is the support piece and the vertical portion is the solder attachment position.

20. A secondary battery of claim 18 wherein said CID has a groove shaped structure having a bottom and a groove wall, wherein said solder attachment position is at the bottom of the groove shaped structure, wherein the groove wall is the support piece, and wherein said support piece is an arm extending from the groove shaped structure.

21. A secondary battery of claim 18 wherein the CID has a funnel-shaped body, wherein the support piece is a cantilever extending from the funnel-shaped body, wherein the solder attachment position is at the funnel-shaped body, wherein there are through-holes on the funnel-shaped body, and wherein the solder attachment position attaches through the ring shaped structure of the support component to the battery shell.