CN110797478B

CN110797478B - Secondary battery

Info

Publication number: CN110797478B
Application number: CN201810862709.0A
Authority: CN
Inventors: 许虎; 任苗苗; 来佑磊; 金海族; 朱凌波
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2018-08-01
Filing date: 2018-08-01
Publication date: 2021-08-24
Anticipated expiration: 2038-08-01
Also published as: CN110797478A

Abstract

A secondary battery includes an electrode assembly, a case, and a cap assembly. The shell is provided with an opening and accommodates the electrode assembly; the top cover assembly includes a top cover plate, a first electrode terminal and a second electrode terminal, the top cover plate is fixed to the housing and covers the opening of the housing. The electrode assembly comprises a main body part, a first tab and a second tab, wherein the first tab and the second tab are respectively positioned on two sides of the main body part along the transverse direction, the first tab is electrically connected to the first electrode terminal, and the second tab is electrically connected to the second electrode terminal. The top cap plate has a protrusion protruding toward a side away from the electrode assembly, and the protrusion forms a recess at a side close to the electrode assembly. The main body part is equipped with first recess and second recess in the one end that is close to the lamina tecti, and first recess and second recess are along horizontal arrangement, and the part of main body part between first recess and the second recess stretches into the concave part.

Description

Secondary battery

Technical Field

The invention relates to the field of batteries, in particular to a secondary battery.

Background

The secondary battery generally includes an electrode assembly formed by winding a positive electrode sheet, a negative electrode sheet, and a separator, a case housing the electrode assembly, and a top cover plate fixed to the case. In order to improve the energy density of the secondary battery, the prior art generally chooses to increase the width of the electrode assembly; however, after the width of the electrode assembly is increased, gas generated by the reaction of the electrode assembly is difficult to discharge in time, so that the gas is accumulated between the positive and negative pole pieces, and the risk of lithium precipitation is caused. Further, the top lid plate of the related art is substantially flat, has low deformation resistance, and is easily deformed when the internal pressure of the secondary battery is increased to a certain extent.

Disclosure of Invention

In view of the problems of the background art, an object of the present invention is to provide a secondary battery that can shorten an exhaust path, prevent lithium deposition, reduce the amount of deformation of a top lid plate, and improve energy density.

In order to achieve the above object, the present invention provides a secondary battery including an electrode assembly, a case, and a cap assembly. The shell is provided with an opening and accommodates the electrode assembly; the top cover assembly includes a top cover plate, a first electrode terminal and a second electrode terminal, the top cover plate is fixed to the housing and covers the opening of the housing. The electrode assembly comprises a main body part, a first tab and a second tab, wherein the first tab and the second tab are respectively positioned on two sides of the main body part along the transverse direction, the first tab is electrically connected to the first electrode terminal, and the second tab is electrically connected to the second electrode terminal. The top cap plate has a protrusion protruding toward a side away from the electrode assembly, and the protrusion forms a recess at a side close to the electrode assembly. The main body part is equipped with first recess and second recess in the one end that is close to the lamina tecti, and first recess and second recess are along horizontal arrangement, and the part of main body part between first recess and the second recess stretches into the concave part.

The main body part is flat and comprises a flat area, a first bending area and a second bending area, the first bending area is positioned on one side of the flat area, which is close to the top cover plate, and the second bending area is positioned on one side of the flat area, which is far away from the top cover plate; the first groove and the second groove are respectively positioned on two sides of the first bending area along the transverse direction, and a part of the first bending area is accommodated in the concave part. Preferably, the first groove and the second groove penetrate the first bending region in the thickness direction.

The first groove and the second groove are symmetrical about a plane perpendicular to the transverse direction.

The ratio of the length of the first bending area to the length of the flat area along the transverse direction is 1/3-3/4.

The lamina tecti still is equipped with annotates the liquid hole, and annotates the liquid hole and be located the levelling zone upside.

The first electrode terminal protrudes above the cap plate, and a height of the protrusion is not greater than a height of the first electrode terminal protruding above the cap plate.

The top cover assembly further comprises an explosion-proof valve arranged on the protrusion of the top cover plate. A gap is reserved between the explosion-proof valve and the main body part.

The main body part is provided with third grooves at two sides of the second bending area along the transverse direction.

The invention has the following beneficial effects: the inner space of the secondary battery can be enlarged by arranging the bulge on the top cover plate; through set up first recess and second recess on the main part, can guarantee that a part of main part can stretch into the concave part to increase space utilization, improve energy density. Meanwhile, the first and second grooves expose the first and second pole pieces of the main body part, so that the gas generated by the electrode assembly can be discharged from the first and second grooves, thereby shortening the exhaust path, avoiding the gas accumulation between the first and second pole pieces and preventing the lithium precipitation. Compare with flat lamina tecti, this application is through setting up the intensity that the abrupt improvement lamina tecti that rises to reduce the deflection of lamina tecti under the effect of producing gas.

Drawings

Fig. 1 is a schematic view of an embodiment of a secondary battery according to the present invention.

Fig. 2 is a sectional view of the secondary battery of fig. 1.

Fig. 3 is a front view of an electrode assembly according to the present invention.

Fig. 4 is a cross-sectional view taken along line a-a of fig. 3.

Fig. 5 is a cross-sectional view taken along line B-B of fig. 3.

Fig. 6 is a schematic view of a positive electrode tab of the electrode assembly of fig. 3.

Fig. 7 is a schematic view of a negative electrode tab of the electrode assembly of fig. 3.

Fig. 8 is a schematic view of a separator of the electrode assembly of fig. 3.

Fig. 9 is a schematic view of another embodiment of a secondary battery according to the present invention.

Fig. 10 is a front view of the electrode assembly of fig. 9.

Wherein the reference numerals are as follows:

1 electrode assembly 312 recess

11 main body 313 pour hole

111 planarized region 32 first electrode terminal

112 first bending region 33 second electrode terminal

113 second bending zone 34 explosion-proof valve

12 first tab 35 seal

13 second pole ear 4 current collecting component

14 first pole piece 5 wicking element

141 first coating zone 51 base

142 first uncoated 52 land

15 second pole piece G notch

151 second coating region R1 first groove

152 second uncoated region R2 second groove

16 diaphragm R3 third groove

2 shell X transverse

3 Top cover Assembly Y longitudinal

31 ceiling plate Z thickness direction

311 projection

Detailed Description

Referring to fig. 1 and 2, the secondary battery includes an electrode assembly 1, a case 2, and a cap assembly 3.

The housing 2 may have a hexahedral shape or other shapes. The case 2 forms a receiving chamber therein to receive the electrode assembly 1 and the electrolyte. The case 2 is formed with an opening at one end, and the electrode assembly 1 may be placed into the receiving cavity of the case 2 through the opening. The housing 2 may be made of a conductive metal material such as aluminum or aluminum alloy, or may be made of an insulating material such as plastic.

The top cap assembly 3 includes a top cap plate 31, a first electrode terminal 32, and a second electrode terminal 33, and the top cap plate 31 is fixed to the case 2 and covers the opening of the case 2.

The electrode assembly 1 includes a first pole piece 14, a second pole piece 15, and a separator 16 disposed between the first pole piece 14 and the second pole piece 15, and the first pole piece 14, the second pole piece 15, and the separator 16 are wound as one body.

Referring to fig. 6, the first electrode sheet 14 may include a first current collector and a first active material layer coated on a surface of the first current collector, wherein the first active material layer and a portion of the first current collector covered by the first active material layer constitute a first coated region 141, and a portion of the first current collector not covered by the first active material layer is a first uncoated region 142. The first current collector is made of metal foil. The first uncoated region 142 may be plural.

Referring to fig. 7, the second electrode sheet 15 may include a second current collector and a second active material layer coated on a surface of the second current collector, wherein the second active material layer and a portion of the second current collector covered by the second active material layer constitute a second coated region 151, and a portion of the second current collector not covered by the second active material layer is a second uncoated region 152. The second current collector is made of metal foil. The second uncoated region 152 may be plural.

After the first pole piece 14, the second pole piece 15, and the separator 16 are wound together, the first coated region 141 of the first pole piece 14, the separator 16, and the second coated region 151 of the second pole piece 15 form the main body portion 11, the plurality of first uncoated regions 142 are laminated together and form the first tab 12, and the plurality of second uncoated regions 152 are laminated together and form the second tab 13. The first tab 12 and the second tab 13 are respectively located on both sides of the main body portion 11 in the transverse direction X.

Referring to fig. 2, the secondary battery further includes two current collecting members 4, one current collecting member 4 connecting the first tab 12 and the first electrode terminal 32, and the other current collecting member 4 connecting the second tab 13 and the second electrode terminal 33.

The top cap plate 31 has a protrusion 311, the protrusion 311 protrudes toward a side away from the electrode assembly 1, and the protrusion 311 forms a recess 312 at a side close to the electrode assembly 1. Referring to fig. 2 and 3, the main body portion 11 is provided with a first groove R1 and a second groove R2 at an end near the top cover plate 31, the first groove R1 and the second groove R2 are arranged in the lateral direction X, and a portion of the main body portion 11 between the first groove R1 and the second groove R2 protrudes into the recess 312.

Referring to fig. 6, when the first pole piece 14 is prepared, a plurality of gaps G may be cut on the first coating region 141 of the first pole piece 14; correspondingly, referring to fig. 7 and 8, a plurality of gaps G are cut in the second coated region 151 of the second pole piece 15 and the separator 16; when the first pole piece 14, the second pole piece 15, and the diaphragm 16 are wound together, the notches G of the first pole piece 14, the second pole piece 15, and the diaphragm 16 overlap and form a first groove R1 and a second groove R2. The gap G may be rectangular or trapezoidal.

The present invention can increase the internal space of the secondary battery by providing the protrusion 311 on the top cover plate 31; by forming the first groove R1 and the second groove R2 in the main body 11, a part of the main body 11 can be ensured to extend into the concave portion 312, thereby increasing space utilization and improving energy density. Meanwhile, the first and second grooves R1 and R2 expose the first and

second pole pieces

14 and 15 of the main body 11, so that the generated gas of the electrode assembly 1 can be discharged from the first and second grooves R1 and R2, thereby shortening the exhaust path, preventing the gas from accumulating between the first and

second pole pieces

14 and 15, and preventing lithium deposition. Compared with a flat top cover plate, the strength of the top cover plate 31 is improved by the arrangement of the protrusions 311, and therefore the deformation of the top cover plate 31 under the action of gas generation is reduced.

Referring to fig. 3 to 5, the first pole piece 14, the second pole piece 15 and the diaphragm 16 are wound together and flattened, and the flattened main body portion 11 is flat and includes a flat region 111, a first bending region 112 and a second bending region 113, the first bending region 112 is located on a side of the flat region 111 close to the top cover plate 31, and the second bending region 113 is located on a side of the flat region 111 away from the top cover plate 31. The first groove R1 and the second groove R2 are respectively located on two sides of the first bending region 112 along the transverse direction X, and a portion of the first bending region 112 is accommodated in the recess 312. Preferably, the first and second grooves R1 and R2 penetrate the first bending region 112 in the thickness direction Z.

In the first bending region 112 and the second bending region 113, the first pole piece 14 and the second pole piece 15 are both bent; after the main body 11 is flattened, the interfaces of the first and

second pole pieces

14 and 15 and the separator 16 are likely to be in poor contact in the first bending region 112, thereby causing polarization of the electrode assembly 1 and affecting the performance of the electrode assembly 1. The present application reduces the risk of polarization of the electrode assembly 1 by reducing the length of the first bending region 112 by providing the first groove R1 and the second groove R2. In addition, the first groove R1 and the second groove R2 expose one end of the leveling area 111 close to the top cover plate 31, so that the generated gas in the leveling area 111 can be directly discharged from the first groove R1 and the second groove R2, thereby improving the gas discharge efficiency and preventing lithium precipitation.

The first groove R1 and the second groove R2 are symmetrical about a plane perpendicular to the transverse direction X.

The ratio of the length of the first bending area 112 to the length of the flat area 111 along the transverse direction X is 1/3-3/4. If the ratio is less than 1/3, the first and

second pole pieces

14 and 15 of the first bending region 112 are easily broken during winding; if the ratio is greater than 3/4, the length of the first bending region 112 in the transverse direction X is too large, the increase in the exhaust rate is limited, and the problem of lithium deposition still remains, and the first bending region 112 is too long to be inserted into the recess 312.

Referring to FIG. 2, the top cover plate 31 is further provided with a liquid injection hole 313, and the liquid injection hole 313 is located on the upper side of the flat region 111. In the electrolyte injection step of the secondary battery, the electrolyte enters the inside of the case 2 through the electrolyte injection hole 313; since the liquid injection hole 313 is located above the planarization region 111, the electrolyte can directly flow into the planarization region 111 in the liquid injection process, thereby improving the uniformity of wetting. After the liquid injection is completed, a sealing member 35 is placed in the hole 313 of the liquid injection hole.

The first electrode terminal 32 protrudes above the cap plate 31, and the height of the protrusion 311 is not greater than the height of the first electrode terminal 32 protruding above the cap plate 31. This prevents the protrusions 311 from increasing the overall height of the secondary battery, thereby improving the energy density of the secondary battery.

The top cover assembly 3 further includes an explosion-proof valve 34 provided to a protrusion 311 of the top cover plate 31. When the secondary battery is short-circuited, the gas is severely generated inside the secondary battery and the internal pressure is sharply increased, and the explosion-proof valve 34 is ruptured under the action of the internal pressure, so that the gas inside the secondary battery is discharged and explosion is prevented.

A gap is left between the explosion-proof valve 34 and the first bending section 112 of the main body portion 11. The electrode assembly 1 is expanded during operation, and if the explosion-proof valve 34 is in contact with the first bending region 112, the explosion-proof valve 34 is easily broken by the compression of the first bending region 112, resulting in the failure of the explosion-proof valve 34.

Referring to fig. 9 and 10, the main body portion 11 is provided with third grooves R3 on both sides of the second bending region 113 in the transverse direction X. The third groove R3 exposes an end of the leveling area 111 far from the top cover plate 31, and the electrolyte stored at the bottom of the housing 2 can directly enter the leveling area 111 from the third groove R3, so that wettability is improved.

The secondary battery further includes a liquid absorbing member 5 capable of absorbing the electrolytic solution, liquid absorbing member 5 including a base portion 51 and two convex portions 52 on a side of base portion 51 close to top lid plate 31; the second bending region 113 is interposed between the two projections 52, and each projection 52 is inserted into the corresponding third groove R3 and is in contact with the flat region 111 and the second bending region 113.

In the liquid injection step of the secondary battery, a part of the electrolytic solution injected into case 2 is quickly absorbed in liquid absorbing member 5. By providing the third groove R3, the planarized region 111 can be exposed; in the working process of the secondary battery, the electrolyte in the liquid absorbing member 5 can directly enter the leveling area 111, so that the electrolyte stored at the bottom of the housing 2 is continuously transferred to the leveling area 111, and the wettability is improved. Electrode assembly 1 expands during operation, and when expanding, liquid-absorbing member 5 is compressed, and liquid-absorbing member 5 is pressed and releases the internally stored electrolyte, thereby supplying electrolyte to electrode assembly 1 and improving the liquid retention capacity of the secondary battery. In a word, the secondary battery can shorten the infiltration path of the electrolyte, improve the infiltration of the electrolyte, avoid lithium precipitation and prolong the service life of the secondary battery.

Generally, the case 2 is made of a metal material, so a certain distance needs to be kept between the electrode assembly 1 and the case 2 to prevent the electrode assembly 1 from contacting the case 2 when expanding, and to prevent short circuit. That is, the electrode assembly 1 is in a suspended state, and the case 2 cannot effectively support the electrode assembly 1 and the current collecting member 4. When the secondary battery vibrates, shaking of the electrode assembly 1 may cause the junction of the current collecting member 4 and the first tab 12 (or the second tab 13) to be torn, resulting in failure of the secondary battery. In the present application, however, the two protrusions 52 of the liquid absorbing member 5 can support the electrode assembly 1 from the lower side, reducing the vibration of the electrode assembly 1 and reducing the risk of tearing at the junction of the current collecting member 4 and the first tab 12.

Liquid absorbing member 5 is an insulating porous material, and liquid absorbing member 5 has elasticity. Insulating wicking member 5 can separate housing 2 from electrode assembly 1 to avoid shorting. The porous structure of liquid absorbing member 5 can efficiently absorb the electrolytic solution. Since liquid absorbent member 5 has elasticity, liquid absorbent member 5 can be compressed when electrode assembly 1 is expanded. Preferably, liquid absorbent member 5 is made of glass fibers, which have a high porosity, high liquid absorption capacity, compressibility, corrosion resistance, and good insulation properties.

Claims

1. A secondary battery includes an electrode assembly (1), a case (2), and a cap assembly (3);

the case (2) has an opening and houses the electrode assembly (1);

the top cover assembly (3) comprises a top cover plate (31), a first electrode terminal (32) and a second electrode terminal (33), wherein the top cover plate (31) is fixed on the shell (2) and covers the opening of the shell (2);

the electrode assembly (1) comprises a first pole piece (14), a second pole piece (15) and a diaphragm (16) arranged between the first pole piece (14) and the second pole piece (15), wherein the first pole piece (14), the second pole piece (15) and the diaphragm (16) are wound into a whole;

the electrode assembly (1) comprises a main body part (11), a first tab (12) and a second tab (13), wherein the first tab (12) and the second tab (13) are respectively positioned on two sides of the main body part (11) along the transverse direction (X), the first tab (12) is electrically connected to a first electrode terminal (32), and the second tab (13) is electrically connected to a second electrode terminal (33);

it is characterized in that the preparation method is characterized in that,

the top lid plate (31) has a protrusion (311), the protrusion (311) protrudes toward a side away from the electrode assembly (1), and the protrusion (311) forms a recess (312) at a side close to the electrode assembly (1);

the main body part (11) is provided with a first groove (R1) and a second groove (R2) at one end close to the top cover plate (31);

the first groove (R1) and the second groove (R2) are formed by overlapping the notches (G) of the first pole piece 14, the second pole piece (15) and the diaphragm (16);

the main body part (11) is flat and comprises a flat area (111), a first bending area (112) and a second bending area (113), the first bending area (112) is located on one side, close to the top cover plate (31), of the flat area (111), and the second bending area (113) is located on one side, far away from the top cover plate (31), of the flat area (111);

the first groove (R1) and the second groove (R2) are respectively positioned on two sides of the first bending area (112) along the transverse direction (X), and a part of the first bending area (112) is accommodated in the concave part (312).

2. The secondary battery according to claim 1, wherein the first groove (R1) and the second groove (R2) are symmetrical with respect to a plane perpendicular to the transverse direction (X).

3. The secondary battery according to claim 1, wherein a ratio of a length of the first bending region (112) to a length of the flat region (111) in the transverse direction (X) is 1/3-3/4.

4. The secondary battery according to claim 1, wherein the top lid plate (31) is further provided with a liquid injection hole (313), and the liquid injection hole (313) is located on the upper side of the leveling region (111).

5. The secondary battery according to claim 1, wherein the first electrode terminal (32) protrudes above the cap plate (31), and a height of the protrusion (311) is not greater than a height at which the first electrode terminal (32) protrudes above the cap plate (31).

6. The secondary battery according to claim 5, wherein the cap assembly (3) further comprises an explosion-proof valve (34) provided to the protrusion (311) of the cap plate (31).

7. The secondary battery according to claim 6, wherein a gap is left between the explosion-proof valve (34) and the main body portion (11).

8. The secondary battery according to claim 1, wherein the main body portion (11) is provided with third grooves (R3) at both sides of the second bending region (113) in the transverse direction (X).