CN1252843C - Safety protection structure of prismatic battery - Google Patents

Abstract

The invention relates to a safety protection structure of a square battery, which is characterized in that: the bottom edge of the sealed insulation sheet is arranged below the end cover plate, and a metal conductive sheet is connected to the electrode terminal, so that the metal conductive sheet transversely extends to be close to the lateral vertical surface of the tank body and is not contacted with the lateral vertical surface, and the metal conductive sheet has a distance of about 0.25 mm-0.5 mm from the tank wall of the vertical surface; by controlling the length of the conducting strip, the possibility of short circuit of the battery under the condition of no deformation can be avoided, and when the battery is pressed and deformed, the short circuit is formed between the conducting strip and the side edge of the tank body; therefore, the short-circuit current is evenly distributed on the whole pole piece, the possibility of local high heat is reduced, and the effect of improving safety is achieved.

Description

Safety protection structure of prismatic battery

technical field

The invention relates to a safety protection structure of a square secondary lithium ion battery, in particular to such a square secondary lithium ion battery, wherein a metal conductive sheet is installed under the end cover plate so that it extends close to the battery tank When the battery is impacted or crushed and deformed, a positive and negative short circuit is formed, which reduces the short circuit resistance, and the short circuit current is evenly distributed on the entire pole piece, greatly reducing the local High heat possibility for safe effect.

Background technique

Secondary lithium-ion batteries have high energy density, high output power, fast charging, and non-polluting characteristics. They have become indispensable equipment for thin, light, portable electronic or communication products; , due to dendrites of lithium metal, it will pierce the positive and negative separators in the polar roll and cause internal short circuit, which will cause safety problems in use; while the safety design of traditional lithium batteries is nothing more than current limiting, power failure and gas release, etc. Among them, the current limiting design is to use PTC (Note: PTC is the abbreviation of Positive Temperature Coefficient of Resistivity) to prevent the flow of high current, which is a non-destructive safety design; and the power-off method is when When the internal pressure of the battery increases, the conductive and fragile items in the internal circuit of the battery can be broken to achieve the effect of cutting off the flow; the way of releasing gas is that when the internal pressure of the battery increases, the safety film is pierced by the thimble, and the The air hole releases the gas or releases the pressure by opening the valve to avoid battery explosion.

However, the above is mainly aimed at the safety protection measures adopted when the internal pressure of the battery is abnormally increased. This type of patent has been found in Taiwan Publication No. 377045, No. 364666, and US Patent Nos. 4,238,812 and 4,255,688. , but there is no mention of the safety protection when the battery is deformed by external pressure; because the outside of the battery tank will be deformed after being impacted by the impact pressure, as a result, local overheating is prone to occur, and sparks and burns are generated due to short circuits inside the pole roll , smoke and other situations, and there are safety issues.

Therefore, it is the problem to be solved by the present invention to design a necessary safety protection structure when the battery is deformed under pressure.

Contents of the invention

The main purpose of the present invention is to provide a safety protection structure for a prismatic battery, which can avoid internal short circuit, scorching, and smoke spraying of the pole roll when the tank body is impacted (Impact) or crushed (Crash) sideways. In order to achieve the effect of enhancing safety.

In order to achieve the above purpose, the present invention installs a metal conductive sheet under the battery end cover, so that it extends close to the side vertical surface of the battery tank without contacting it, and the possibility of short circuit without deformation of the battery can be avoided through length control When the battery is compressed and deformed, a short circuit is formed between the conductive sheet and the side of the tank.

Description of drawings

Fig. 1 is the perspective view of the present invention;

Fig. 2 is a structural sectional view of the present invention;

Fig. 3 is an enlarged schematic view of part A in Fig. 2;

Fig. 4 is the schematic diagram when the present invention is subjected to impact deformation;

Figure 5 is a schematic diagram of the present invention when it is crushed and deformed;

Figures 6 and 7 are photos showing the amount of deformation when the safety valve is facing upwards or downwards for the impact test;

Figures 8-10 are photos of the finished products of the prismatic batteries 633048, 863448 and 1003450 used in the safety experiment;

Figures 11-16 are photos after impact or crushing, respectively.

Detailed ways

First, referring to Fig. 1 and Fig. 2, the safety protection structure of the square secondary lithium ion battery disclosed by the present invention includes:

A tank body 1, which is a flat square box body with wide front and rear surfaces 11 and narrow vertical surfaces 12 on both sides. The formed battery pole volume 13;

One end cover plate 2 is fixed on the open end of the tank body 1, and an electrode terminal 3 and an insulating sheet 4 for isolating the electrode terminal 3 and the end cover plate 2 are installed on it, and a through hole 21 is provided on one side to install a safety valve 5 ;

It is characterized by:

Below the end cover plate 2 is the bottom edge of the sealing insulation sheet 4, and a metal conductive sheet 6 is connected on the electrode terminal 3, so that it extends laterally close to the side vertical surface 12 of the tank body without contacting it, and makes it separate from it. The tank wall of the vertical surface 12 has a distance D of about 0.25 mm to 0.5 mm; by controlling the length of the conductive sheet 6, the possibility of short circuit without deformation of the battery can be avoided, and when the battery is deformed under pressure, the conductive sheet 6 Form a short circuit with the tank body 1 side.

The above-mentioned installation and fixing method of the conductive sheet 6 can be riveted together when the end cover plate 2 is riveted to the electrode terminal 3 , or it can be welded on the electrode terminal 3 by welding. In order to prevent the conductive sheet 6 from bending upwards and causing the battery tank 11 to be short-circuited without external deformation, a high-strength, non-deformable metal can be used as the conductive sheet.

Moreover, in general, the electrode terminal 3 is set as the positive pole, and the tank body 1 and the end cover plate 2 are set as the negative pole; of course, the electrode terminal 3 can also be set as the negative pole, and the tank body 1 and the end cover plate 2 are set as the positive pole. .

Through the above technical features, when the battery can body 1 of the present invention is impacted or flattened laterally as shown in Figure 4 or Figure 5, when the deformation of the can mouth is >0.25mm, the conductive sheet will contact the can wall Causes the formation of positive and negative short circuits externally, reduces the short circuit resistance, and distributes the short circuit current evenly to all pole pieces, greatly reducing the possibility of local high heat. This can avoid the internal short circuit of the pole coil 13 to produce sparks, burnt, smoke, etc. To achieve the effect of enhancing safety.

In order to verify the effect of the present invention, the following safety experiments were done by taking square batteries 633048, 863448 and 1003450 as examples.

background description

Before the improvement, the X direction can pass the test, and the Y direction safety test impact (Impact), crushing (Crush) items have a few unqualified in each test, the unqualified data are as follows, so we start to improve the Y direction .

633048: 2/20 pieces failed the Impact test, and the failure rate of the Crush test was less than 10%.

863448: 2/10 pieces failed the Crush test.

1003450: 3/5 of the 2lot Crush test failed.

Origin of design

According to the previous experimental experience, regardless of whether the safety valve (S/V) is facing upward or downward in the Y direction, the deformation of the safety valve end is always the largest during impact (as shown in Figures 6 and 7), because the end cover plate is dug out  2.8mm is used as the hole of the safety valve, so the longitudinal direction of the diameter of the safety valve is the weakest and the most easily deformed; when it is flattened, the deformation on both sides is almost equal, so it is best to make the conductive sheet in the direction of the safety valve, which is most likely to cause a short circuit way without affecting the injection.

Experimental procedure

1. A conductive piece of aluminum-nickel sheet is laser-welded on the big head of the rivet of the end cover group. The extension direction of the aluminum-nickel sheet faces the safety valve, and the end edge is about 0.5mm away from the edge of the end cover plate. The external short-circuit point after deformation is manufactured. The finished products are shown in the figure 8, 9, and 10.

2. Cut off the wall on the short side of the insulating sheet so that the aluminum-nickel sheet can protrude to create a short circuit. Then assemble the welded end cover group into a battery according to the normal procedure and complete the formation. Do impact and flattening experiments.

Experimental results

The experimental data are shown in the table below.

serial number strike strike flatten flatten 633048A-680mAh 633048B-680mAh 863348C-1300mAh 1003450A-1550mAh Maximum temperature °C SV Maximum temperature °C SV Maximum temperature °C SV Maximum temperature °C SV 1 111 ↑ 104 ↑ 104 ↑ 100 ↑ 2 111 ↑ 118 ↑ 95 ↑ 101 ↑ 3 94 ↑ 107 ↑ 101 ↑ 93 ↑ 4 99 ↑ 104 ↑ 108 ↑ 28 ↑ 5 116 ↓ 100 ↑ 103 ↑ 102 ↑ 6 123 ↓ 104 ↑ 99 ↓ 450 ↓ 7 108 ↓ 130 ↑ 103 ↓ 102 ↓ 8 102 ↓ 28 ↑ 103 ↓ 28 ↓ 9 109 ↓ 112 ↓ 103 ↓ 10 103 ↓ 101 ↓ 100 ↓ 11 110 ↓ 111 ↓ 105 ↓ 12 107 ↓ 114 ↓ 13 103 ↓ 109 ↓ 14 107 ↓ 103 ↓ 15 106 ↓ 16 103 ↓

Under normal circumstances, the external short-circuit temperature is about 100°C, 28°C is the normal value at room temperature and should not be short-circuited, and 450°C is an unsafe state of internal short-circuit.

One of the 633048B-780mAh has no short circuit, and the aluminum nickel sheet is inserted into the insulating sheet to form an insulating state.

1003450A-1550mAh, two of them did not have a short circuit, and the temperature of one was too high after a short circuit. It was found that the cover plate at the end of the welding bead of the tank cover popped out, so that the conductive sheet did not contact the tank wall and failed.

Retry 1003450A-1550mAh, and retest after increasing the R-angle laser power, hoping to make the short side of the end cover plate short-circuited, and the welding depth will be deepened due to the increase of power, so that the end cover plate will not be ejected.

The results are all qualified, the data are as follows: squash No. 1 2 3 4 5 6 7 8 9 10 Maximum temperature °C 97 110 110 110 101 107 113 113 113 112

New Design of End Cap Group Mechanism

According to the design of the experiment, the edge of the aluminum-nickel sheet is about 0.5mm away from the edge of the end cover, and there are still a few pieces that are not short-circuited. After inspection, it is found that the conductive sheet is inserted into the insulating sheet, so that there is no short-circuit, so the distance is reduced to 0.25mm. When the Y direction of the tank body is impacted or flattened, the conductive sheet will touch the tank wall and cause an external short circuit when the deformation of the tank mouth is greater than 0.25 mm. Smoke and other situations, in order to achieve the purpose of safety.

in conclusion

The results of the experimental test with a pitch of about 0.5mm are almost all qualified, so it should be no problem to reduce the pitch to 0.25mm according to this design and convert it into an official product, and the success rate will be higher. The conductive sheet cannot grow without reason and can only be shortened, and through the rotation simulation of Auto CAD, even if the conductive sheet has the maximum skew after riveting, there is still a distance of 0.2mm from the edge of the end cover, which is enough to cover the end cover and the conductive sheet Tolerance, also will not directly contact the tank wall. It is suggested that the laser power on the short side should be increased to deepen the welding depth during production line manufacturing, so as to avoid failure of the end cover group ejected from the tank body. When it is produced as a formal product, the conductive sheet will be installed between the rivet and the end cover sealing insulating sheet for riveting.

According to the experimental conclusion, the results of the experimental test with a distance of 0.5mm between the conductive sheet 6 and the tank wall are almost all qualified, so the design reduces the distance D to 0.25mm, and the success rate will be higher, and the conductive sheet 6 cannot increase without reason. , only possible to be shortened, and the rotation simulation is done by computer graphics, even if the conductive sheet 6 is riveted to produce the maximum skew, there is still a distance of 0.2mm from the edge of the end cover plate, which is enough to cover the tolerance of the end cover plate 2 and the conductive sheet 6 , also unlikely to directly contact the tank wall; therefore, the present invention has reached the stage of implementation and has value for industrial utilization.

The drawings and descriptions disclosed above are only preferred embodiments of the present invention, and modifications or equivalent changes made according to the spirit of the present case should still be included in the patent application scope of the present case.

Claims (4)

1. the safety protection structure of a rectangular cell comprises:

One tank body, it is the narrower flat square box of front-back broad two side direction risers, its inside is provided with by the battery pole coil that barrier film constituted of positive and negative electrode element and between between positive and negative electrode;

One end casing, it is fixed on the tank body openend, is equiped with the insulating trip of electrode terminal and isolated electrode terminal and end casing on it, and the one side is provided with a through hole with the installing safety valve;

It is characterized in that:

On electrode terminal, connect a conducting strip that is made of metal, described conducting strip is positioned at the below of end casing and insulating trip, described conducting strip horizontal expansion is not contact with it near the side direction risers of tank body, and makes its tank skin from risers that the spacing of 0.25mm～0.5mm is arranged; By the length of control conducting strip, can avoid battery not have the possibility of short circuit under the distortion situation, and when making the battery compressive deformation, promptly in conducting strip and tank body side formation short circuit.

2. the safety protection structure of rectangular cell as claimed in claim 1, wherein, this conducting strip with the electrode terminal riveted at end casing.

3. the safety protection structure of rectangular cell as claimed in claim 1, wherein, this conducting strip utilizes welding manner to be fixed on the electrode terminal.

4. the safety protection structure of rectangular cell as claimed in claim 1, wherein, this conducting strip is made of the on-deformable metal of high strength.

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