Patent Description:
As an important part of a new energy vehicle, a secondary battery is important in its safety performance. With charging and discharging of the secondary battery, gas will be generated inside the secondary battery. If the gas has a high pressure, the secondary battery may explode. Accordingly, a gas pressure-controlled vent may be provided on a cover plate of the secondary battery.

Since one secondary battery has small capacity or small power, a plurality of secondary batteries is usually provided to form a battery module for use. Once one secondary battery of the battery module experiences thermal runaway, heat generated thereby will be quickly transferred to other secondary batteries of the battery module. Accordingly, the other secondary batteries also experience thermal runaway, thereby causing sharp rise in temperature and gas pressure. When the existing gas pressure-controlled vent experiences thermal runaway, there is a risk that the secondary battery will explode if there is no enough time to release the pressure.

Therefore, it is needed to design a new secondary battery to solve the above problems, so as to improve the safety performance of the secondary battery.

<CIT> discloses a battery comprising a safety vent assembly. The safety vent assembly comprises a sealing member and an urging member to urge the sealing member against a venting aperture on a battery reaction chamber to seal the battery reaction chamber when pressure inside the battery reaction chamber is below a venting threshold pressure under normal operation conditions, wherein the sealing member is operable to provide a venting path to vent gas from the battery chamber when pressure inside the battery chamber reaches the venting threshold pressure which is sufficient to overcome the urging force of the sealing member, and wherein the urging member is to permanently deform on reaching a venting threshold temperature such that gas venting from the battery chamber will occur at a pressure below the venting threshold pressure.

The present disclosure provides a cover assembly of a secondary battery and a secondary battery that can solve the problem in the related art and improve a safety performance of the secondary battery.

In a first aspect, the present disclosure provides a cover assembly of a secondary battery, including:.

In a possible design, the gas exhaust valve includes a metal sheet and a fixing part, and the metal sheet seals the gas vent;.

In a possible design, the fixing part has a melting point within a range of <NUM> to <NUM>.

In a possible design, the fixing part includes a main body portion and a connection portion;.

In a possible design, the connection portion has a ring structure and surrounds a side wall of the metal sheet.

In a possible design, one of the connection portion and the metal sheet is provided with a protrusion, and the other one of the connection portion and the metal sheet is provided with a first groove; and
the protrusion matches the first groove.

In a possible design, the main body portion is provided with a first center hole; and
the first center hole is opposite to the gas vent.

In a possible design, along a thickness direction of the cover assembly, a projection of the fixing part at least partially overlaps a projection of the sealing part.

The cover assembly further includes a pressing block, and the pressing block is fixed to the cover plate;.

Along a thickness direction of the cover assembly, a projection of the pressing block does not overlap a projection of the metal sheet.

In a possible design, the cover plate is provided with a second groove, and the sealing part is at least partially received in the second groove.

In a second aspect, the present disclosure provides a secondary battery, including:.

A technical solution provided by the present disclosure can achieve the following beneficial effects.

For the cover assembly of the secondary battery and the secondary battery provided by the present disclosure, the gas exhaust valve seals the gas vent, and the gas exhaust valve deforms in response to an increase in temperature to get out of a state of sealing the gas vent. When temperature inside the case of the secondary battery rises, gas inside the case can be exhausted via the gas vent, thereby reducing a risk of thermal runaway of the secondary battery, and also slowing down the thermal runaway of the secondary battery and thus providing passengers with sufficient escape time. Since the sealing part is arranged between the gas exhaust valve and the cover plate and surrounds the gas vent for sealing a gap between the gas exhaust valve and the cover plate, sealing of the gas exhaust valve is improved. This can prevent electrolyte leakage of the secondary battery under a normal operation condition or prevent external water vapor from entering an interior of the case, which would otherwise reduce the safety performance and service life of the secondary battery.

It should be understood that the foregoing general description and the following detailed description are merely exemplary and are not intended to limit the present disclosure.

In order to more clearly illustrate technical solutions in embodiments of the present disclosure or in the related art, the accompanying drawings used in the embodiments and in the related art are briefly introduced as follows. It should be noted that the drawings described as follows are merely part of the embodiments of the present disclosure, other drawings can also be acquired by those skilled in the art without paying creative efforts.

The drawings herein are incorporated into and constitute a part of the present specification, illustrate embodiments of the present disclosure and explain principles of the present disclosure together with the specification.

The technical solutions in the embodiments of the present disclosure are described in the following with reference to the accompanying drawings. It should be noted that, the described embodiments are merely exemplary embodiments of the present disclosure, which shall not be interpreted as providing limitations to the present disclosure. All other embodiments obtained by those skilled in the art without creative efforts according to the embodiments of the present disclosure are within the scope of the present disclosure.

The terms used in the embodiments of the present disclosure are merely for the purpose of describing particular embodiments but not intended to limit the present disclosure. Unless otherwise noted in the context, the singular form expressions "a", "an", "the" and "said" used in the embodiments and appended claims of the present disclosure are also intended to represent plural form expressions thereof.

It should be understood that the term "and/or" used herein is merely an association relationship describing associated objects, indicating that there may be three relationships, for example, A and/or B may indicate that three cases, i.e., A existing individually, A and B existing simultaneously, B existing individually. In addition, the character "/" herein generally indicates that the related objects before and after the character form an "or" relationship.

It should be understood that, the terms such as "upper", "lower", "left", "right" and the like are used to indicate positions shown in the drawing, instead of being construed as limitations of the embodiment of the present disclosure. In addition, when an element is described as being "on" or "under" another element in the context, it should be understood that the element can be directly or via an intermediate element located "on" or "under" another element.

<FIG> is a schematic diagram of a structure of a secondary battery according to an embodiment of the present disclosure. <FIG> is a front cross-sectional view illustrating a structure of a secondary battery according to an embodiment of the present disclosure. As shown in <FIG>, an embodiment of the present disclosure provides a secondary battery <NUM>. The secondary battery <NUM> includes a case <NUM>, an electrode assembly <NUM> and a cover assembly <NUM>.

The case <NUM> may be in a hexahedron shape or other shape. A receiving cavity is formed inside the case <NUM> for receiving the electrode assembly <NUM> and an electrolyte. The case <NUM> is open at its one end, so that the electrode assembly <NUM> can be placed in the receiving cavity of the case <NUM> through this opening. A plurality of electrode assemblies <NUM> may be arranged in the receiving cavity, and the plurality of electrode assemblies <NUM> is stacked with respect to each other. The case <NUM> may include a metal material such as aluminum or aluminum alloy, and may further include an insulation material such as plastic.

The electrode assembly <NUM> includes an electrode unit and tab. The electrode unit includes a negative electrode, a positive electrode, and a separator. The separator is located between a negative electrode and a positive electrode that are adjacent, so as to separate the negative electrode from the positive electrode.

In one embodiment, the negative electrode, the separator, and the positive electrode are sequentially stacked and wound to form the electrode unit of the electrode assembly <NUM>. That is, the electrode unit has a wound structure. In another embodiment, the negative electrode, the separator, and the positive electrode are sequentially stacked to form the electrode unit of the electrode assembly <NUM>, and this electrode unit has a stacked structure. At the same time, the electrode unit includes a slit after being formed, and the electrolyte can enter the electrode unit via the slit to infiltrate the negative electrode and the positive electrode.

The negative electrode includes a negative current collector (for example, a copper foil) and a negative active material layer (for example, carbon or silicon) coated on a surface of the negative current collector. The positive electrode includes a positive current collector (for example, an aluminum foil) and a positive active material layer (for example, a ternary material, lithium iron phosphate or lithium cobaltate) coated on a surface of the positive current collector. A negative electrode tab is connected to the negative electrode and protrudes from the electrode unit. The negative electrode tab may be formed by directly cutting the negative current collector. A positive electrode tab is connected to the positive electrode and protrudes from the electrode unit. The positive electrode tab may be formed by directly cutting the positive current collector.

<FIG> is an exploded view of a structure of a cover assembly of a secondary battery according to an embodiment of the present disclosure. As shown in <FIG>, the cover assembly <NUM> includes a cover plate <NUM> and electrode terminals <NUM>. The cover plate <NUM> is fixed to the opening of the case <NUM>, thereby making the electrode assembly <NUM> and the electrolyte be enclosed in the receiving cavity of the case <NUM>. The electrode terminals <NUM> are arranged at the cover plate <NUM> and include a negative electrode terminal and a positive electrode terminal. The two electrode terminals <NUM> are electrically connected to respective tabs via connection plates <NUM>. The cover plate <NUM> is provided with an anti-explosion vent <NUM>, and the anti-explosion plate <NUM> covers the anti-explosion vent <NUM>.

Specifically, for the secondary battery <NUM> in which the tabs protrude from a top of the electrode unit, the above-mentioned connection plates <NUM> are located between the electrode unit of the electrode assembly <NUM> and the cover plate <NUM>. The connection plates <NUM> include a negative connection plate and a positive connection plate. The negative connection plate is configured to connect the negative electrode tab with the negative electrode terminal, and the positive connection plate is configured to connect the positive electrode with the positive electrode terminal. The cover assembly <NUM> further includes an insulation plate <NUM> that insulates the cover plate <NUM> from the electrode assembly <NUM>.

The plurality of secondary batteries <NUM> described above can form a battery module. In the battery module, if one secondary battery experiences thermal runaway, the generated heat will be transferred to an adjacent secondary battery, thereby accelerating thermal runaway of the nearby secondary battery.

In order to solve this problem, an embodiment of the present disclosure provides a cover assembly <NUM> of a secondary battery. <FIG> is a front view of a cover assembly of a secondary battery according to an embodiment of the present disclosure. <FIG> is a cross-sectional view taken along line AA of <FIG>. <FIG> is an enlarged view of an area B of <FIG>. As shown in <FIG>, the cover assembly <NUM> includes a cover plate <NUM>, a gas exhaust valve <NUM>, and a sealing part <NUM>.

The cover plate <NUM> includes a gas vent <NUM>. The gas exhaust valve <NUM> seals the gas vent <NUM>, and the gas exhaust valve <NUM> deforms in response to an increase in temperature in such a manner that the gas exhaust valve <NUM> no longer seals the gas vent <NUM>. A sealing part <NUM> is arranged between the gas exhaust valve <NUM> and the cover plate <NUM> and surrounds the gas vent <NUM>, so as to seal a gap between the gas exhaust valve <NUM> and the cover plate <NUM>.

In this embodiment, the cover assembly <NUM> seals the gas vent <NUM> by the gas exhaust valve <NUM>, and the gas exhaust valve <NUM> deforms in response to an increase in temperature in such a manner that the gas exhaust valve <NUM> no longer seals the gas vent <NUM>. When temperature inside the case <NUM> of the secondary battery <NUM> rises, the gas exhaust valve13 no longer seals the gas vent <NUM>, so that the gas inside the case <NUM> can be exhausted via the gas vent <NUM>. In this way, on the one hand, the pressure inside the case <NUM> can be reduced so as to prevent explosion of the secondary battery <NUM>, and on the other hand, partial heat can be taken away by exhausting gas so as to slow down the thermal runaway of the secondary battery <NUM> and provide sufficient escape time for passengers.

Since the sealing part <NUM> is arranged between the gas exhaust valve <NUM> and the cover plate <NUM> and surrounds the gas vent <NUM> so that the sealing part <NUM> seals the gap between the gas exhaust valve <NUM> and the cover plate <NUM>, sealing of the gas exhaust valve <NUM> is improved. This can prevent electrolyte leakage of the secondary battery <NUM> under or prevent external water vapor from entering an interior of the case <NUM> a normal operation condition, which would otherwise reduce the safety performance and service life of the secondary battery <NUM>.

In an implementation, the gas exhaust valve <NUM> has a lower melting point than the cover plate <NUM>. For example, the gas exhaust valve <NUM> may be formed by a material of PP (polypropylene), PE (polyethylene) or the like. When the temperature inside the case <NUM> exceeds the melting point of the gas exhaust valve <NUM>, the gas exhaust valve <NUM> will deform, that is, melting or softening occurs. At this time, the gas exhaust valve <NUM> will get out of a state of sealing the gas vent <NUM>, so that the gas vent <NUM> is open and thus the gas inside the case <NUM> of the secondary battery <NUM> can be exhausted to an exterior of the case <NUM> via the gas vent <NUM>.

The cover assembly <NUM> may further include a pressing block <NUM>. Along a thickness direction Z of the cover assembly, the pressing block <NUM> presses against the gas exhaust valve <NUM>. The pressing block <NUM> may be welded to the cover plate <NUM>, so that the gas exhaust valve <NUM> is fixed to the cover plate <NUM>.

<FIG> is a partial view of a structure of a cover plate shown in <FIG>. In an implementation, the cover plate <NUM> includes a first recess <NUM> and a second recess <NUM>. With reference to <FIG>, along the thickness direction Z of the cover assembly <NUM>, the first recess <NUM> is located above the gas vent <NUM> and the second recess <NUM> is located above the first recess <NUM>. An inner diameter of the first recess <NUM> is larger than a diameter of the gas vent <NUM>, and an inner diameter of the second recess <NUM> is larger than the inner diameter of the first recess <NUM>. The gas exhaust valve <NUM> is received in the first recess <NUM>, and the pressing block <NUM> is received in the second recess <NUM>.

With the first recess <NUM> and the second recess <NUM>, a top surface of the pressing block <NUM> is substantially aligned with a top surface of the cover plate <NUM>, so that the pressing block <NUM> and the gas exhaust valve <NUM> do not occupy too much space, thereby increasing an energy density of the secondary battery.

In an implementation, the cover plate <NUM> is provided with a second groove <NUM>, and the sealing part <NUM> is received in the second groove <NUM>. When the cover plate <NUM> is provided with the second groove <NUM> and the sealing part <NUM> is at least partially received in the second groove <NUM>, the sealing part <NUM> is in contact with a bottom of the second groove <NUM> and the gas exhaust valve <NUM>. In this way, the sealing of the gas exhaust valve <NUM> is improved. Moreover, with the second groove <NUM>, a space occupied by the cover assembly <NUM> in the thickness direction Z can be reduced, thereby increasing the energy density of the secondary battery <NUM>.

In an implementation, the second groove <NUM> is located at an upper surface of the cover plate <NUM> at a circumference of the gas vent <NUM>, and a lower surface of the gas exhaust valve <NUM> matches the sealing part <NUM> in the second groove <NUM>. Specifically, the second groove <NUM> may be formed at a bottom surface of the first recess <NUM>, and the second groove <NUM> may also be formed at other position of the cover plate <NUM>.

In an implementation, the second groove <NUM> is located at a lower surface of the cover plate <NUM> at the circumference of the gas vent <NUM>, and an upper surface of the gas exhaust valve <NUM> matches the sealing part <NUM> in the second groove <NUM>.

In an implementation, the second groove <NUM> is located at a pore wall at the circumference of the gas vent <NUM>, and a circumferential outer surface of the gas exhaust valve <NUM> matches the sealing part <NUM> in the second groove <NUM>.

Another exemplary embodiment will be described in the following, in which the elements that are the same as those in the above exemplary embodiments will not be further described herein, and only dissimilar elements will be described in detail.

<FIG> is an exploded view of a structure of a cover assembly of a secondary battery according to another embodiment of the present disclosure. <FIG> is a front view of a cover assembly of a secondary battery according to another embodiment of the present disclosure. <FIG> is a cross-sectional view taken along line C-C of <FIG>. <FIG> is an enlarged view of an area D of <FIG>. <FIG> is a schematic view of a structure of a gas exhaust valve shown in <FIG>.

As shown in <FIG>, in a possible implementation manner, the gas exhaust valve <NUM> includes a metal sheet <NUM> and a fixing part <NUM>, and the metal sheet <NUM> seals the gas vent <NUM>. The sealing part <NUM> is arranged between the metal sheet <NUM> and the cover plate <NUM> for sealing a gap between the metal sheet <NUM> and the cover plate <NUM>. The fixing part <NUM> is connected to the metal sheet <NUM>, and the metal sheet <NUM> is fixed to the cover plate <NUM> by the fixing part <NUM>. The fixing part <NUM> deforms in response to an increase in temperature, so as to make the metal sheet <NUM> get out of a state of sealing the gas vent <NUM>.

In an implementation, the metal sheet may be an aluminum sheet, a stainless steel sheet or a nickel sheet, preferably an aluminum sheet, which has advantages of light weight and good penetration resistance.

The fixing part <NUM> has a lower melting point than the cover plate <NUM>. For example, the fixing part <NUM> may be made of PP (polypropylene), PE (polyethylene) or the like. When the temperature inside the case <NUM> exceeds the melting point of the fixing part <NUM>, the fixing part <NUM> will deform, that is, melting or softening occurs. At this time, the metal sheet <NUM> moves with the deformation of the fixing part <NUM>, thereby getting out of a state of sealing the gas vent <NUM>. In this case, the gas vent <NUM> is open, and the gas inside the case <NUM> of the secondary battery <NUM> can be exhausted to an exterior via the gas vent <NUM>. Illustratively, the melting point of the fixing part <NUM> may be within a range of <NUM> to <NUM>.

The sealing part <NUM> may be an annular sealing ring, and the annular sealing ring is arranged between the metal sheet <NUM> and the cover plate <NUM> and is in contact with the metal sheet <NUM> and the cover plate <NUM>, thereby ensuring the sealing between the metal sheet <NUM> and the gas vent <NUM>.

The above-described gas exhaust valve <NUM> includes a metal sheet <NUM>. Since the metal sheet <NUM> has a better penetration resistance, it can prevent the electrolyte in the case <NUM> of the secondary battery <NUM> from penetrating to the exterior of the case <NUM>, and also prevent moisture or other gas outside the case <NUM> from penetrating into the case <NUM>, which would otherwise reduce the service life of the secondary battery <NUM>. With the fixing part <NUM>, rigidity of the entire gas exhaust valve <NUM> can be increased, so that the gas exhaust valve <NUM> does not undergo a big deformation when pressure is applied to the sealing part <NUM>.

In an implementation, as shown in <FIG>, the fixing part <NUM> includes a main body portion 132a and a connection portion 132b. The main body portion 132a is connected to a surface of the metal sheet <NUM> facing away from the sealing part <NUM>. Along a length direction X of the cover assembly <NUM>, the connection portion 132b is connected to two sides of the main body portion 132a, and the connection portion 132b is connected to the metal sheet <NUM>.

The metal sheet <NUM> is connected to the cover plate <NUM> via the above-described connection portion 132b. Specifically, the main body portion 132a, the connection portion 132b, and the metal sheet <NUM> may be formed by injection molding. With the connection portion 132b, reliability of a connection between the metal sheet <NUM> and the cover plate <NUM> is improved, and the above-described pressing block <NUM> can press against the main body portion 132a.

In an implementation, the connection portion 132b has a ring structure and surrounds a side wall of the metal sheet <NUM>. With the connection portion 132b having a ring structure and surrounding the side wall of the metal sheet <NUM>, strength of a connection between the fixing part <NUM> and the metal sheet <NUM> can be further increased, and the fixing part <NUM> can more uniformly and comprehensively sense a temperature change inside the case <NUM>. Once the temperature inside the case <NUM> is extremely high, the connection portion 132b will melt and deform, thereby causing the metal sheet <NUM> to get out of a state of sealing the gas vent <NUM>.

In an implementation, the main body portion 132a is provided with a first center hole 132d, and the first center hole 132d is opposite to the gas vent <NUM>. When the temperature inside the case <NUM> of the secondary battery <NUM> rises to a preset value (a threshold value set based on a temperature at which thermal runaway occurs), the connection portion 132b melts or deforms, and the metal sheet <NUM> accordingly moves or deforms. The first center hole 132d is opposite to the gas vent <NUM>, that is, a center of the first center hole 132d substantially corresponds to a center of the metal sheet <NUM>. In this way, the binding of the fixing part <NUM> to the metal sheet <NUM> is reduced, thereby reducing hindrance to movement or deformation of the metal sheet <NUM>.

<FIG> is an exploded view of a structure of a cover assembly of a secondary battery according to still another embodiment of the present disclosure. <FIG> is a front view of a cover assembly of a secondary battery according to still another embodiment of the present disclosure. <FIG> is a cross-sectional view taken along line E-E of <FIG>. <FIG> is an enlarged view of an area F of <FIG>. <FIG> is a schematic view of a structure of a gas exhaust valve shown in <FIG>,.

As shown in <FIG>, in an implementation, the main body portion 132a may not be provided with the first center hole 132d, but may be integrally connected to a side of the metal sheet <NUM> facing away from the sealing part <NUM>.

In an implementation, along the thickness direction Z of the cover assembly <NUM>, a projection of the fixing part <NUM> at least partially overlaps a projection of the sealing part <NUM>. As described above, with the fixing part <NUM>, an overall rigidity of the gas exhaust valve <NUM> is increased. When the metal sheet <NUM> presses against the sealing part <NUM>, if the fixing part <NUM> cannot at least partially cover the sealing part <NUM>, the metal sheet <NUM> will deform, thereby affecting a sealing effect thereof. Thus, the projection of the setting fixing part <NUM> at least partially overlaps the projection of the sealing part <NUM>, so that the overall rigidity of the gas exhaust valve <NUM> is increased and the pressure on the sealing part <NUM> is increased, thereby ensuring the sealing of the secondary battery <NUM>.

In an implementation, along the thickness direction Z of the cover assembly <NUM>, the projection of the sealing part <NUM> is totally within the projection of the fixing part <NUM>.

The cover assembly <NUM> further includes a pressing block <NUM>, and the pressing block <NUM> is fixed to the cover plate <NUM>. The pressing block <NUM> includes a second center hole <NUM>, and the second center hole <NUM> is opposite to the gas vent <NUM>. The pressing block <NUM> presses against a surface of the fixing part <NUM> facing away from the sealing part <NUM>, and the fixing part <NUM> is fixed to the cover plate <NUM> by the pressing block <NUM>.

The pressing block <NUM> presses against the fixing part <NUM> of the gas exhaust valve <NUM>, and the pressing block <NUM> may be welded to the cover plate <NUM>, so that the gas exhaust valve <NUM> is fixed to the gas vent <NUM>.

When the secondary battery <NUM> is about to experience thermal runaway, if the pressing block <NUM> applies an excessive pressure onto the metal sheet <NUM>, deformation of the metal sheet <NUM> will be affected, thereby resulting in untimely gas exhaust. With the second center hole <NUM>, the pressing block <NUM> does not apply an excessive pressure onto the metal sheet <NUM>.

Along the thickness direction Z of the cover assembly <NUM>, a projection of the pressing block <NUM> does not overlap a the projection of the metal sheet <NUM>. In other words, along the thickness direction Z of the cover assembly <NUM>, the projection of the metal sheet <NUM> does not totally fall within the second center hole <NUM> described above. When the secondary battery is about to experience thermal runaway, a temperature of the gas inside the case <NUM> will cause the fixing part <NUM> to melt or deform, and the metal sheet <NUM> is separated from the gas vent <NUM>. Under an impact of the gas, the metal sheet <NUM> leaves the cover assembly <NUM> of the secondary battery <NUM> via the second center hole <NUM>. With the projection of the pressing block <NUM> not overlapping the projection of the metal sheet <NUM>, after the fixing part <NUM> melts or deforms, the pressing block <NUM> does not block the metal sheet <NUM>, so that the metal sheet <NUM> falls to the exterior of the case <NUM> of the secondary battery instead of falling to the interior of the case <NUM> of the secondary battery <NUM>. This ensures the safety performance of the secondary battery <NUM>.

<FIG> is an exploded view of a structure of a cover assembly of a secondary battery according to yet another embodiment of the present disclosure. <FIG> is a front view of a cover assembly of a secondary battery according to yet another embodiment of the present disclosure. <FIG> is a cross-sectional view taken along line G-G of <FIG> is an enlarged view of an area H of <FIG> is a schematic view of a structure of a gas exhaust valve shown in <FIG>. <FIG> is a schematic view of a structure of a fixing part shown in <FIG>. <FIG> is a schematic view of a structure of a metal sheet shown in <FIG>.

As shown in <FIG>, in an implementation, one of the connection portion 132b and the metal sheet <NUM> is provided with a protrusion 131a, and the other one of the connection portion 132b and the metal sheet <NUM> is provided with a first groove 132c. The protrusion 131a matches the first groove 132c. In this embodiment, the metal sheet <NUM> is provided with the protrusion 131a, and the connection portion 132b is provided with the first groove 132c. With the first groove 132c matching the protrusion 131a, strength of a connection between the metal sheet <NUM> and the connection portion 132b can be further improved. Moreover, with the first groove 132c, both a top surface and a bottom surface of the protrusion 131a of the metal sheet <NUM> are covered by the connection portion 132b. In this case, when the secondary battery <NUM> is not in thermal runaway, the metal sheet <NUM> does not deform easily.

As shown in <FIG>, along the thickness direction Z of the cover assembly <NUM>, the projection of the pressing block <NUM> does not overlap the projection of the metal sheet <NUM>. After the fixing part <NUM> melts or deforms, the pressing block <NUM> does not block the metal sheet <NUM>, so that the metal sheet <NUM> drops to the exterior of the case <NUM> of the secondary battery instead of falling to the interior of the case <NUM> of the secondary battery <NUM>. This can ensure the safety performance of the secondary battery <NUM>.

Claim 1:
A cover assembly (<NUM>) of a secondary battery (<NUM>), comprising:
a cover plate (<NUM>) comprising a gas vent (<NUM>);
a gas exhaust valve (<NUM>) configured to seal the gas vent (<NUM>) and deform in response to an increase in temperature to get out of a state of sealing the gas vent (<NUM>); and
a sealing part (<NUM>) arranged between the gas exhaust valve (<NUM>) and the cover plate (<NUM>) and surrounding the gas vent (<NUM>) for sealing a gap between the gas exhaust valve (<NUM>) and the cover plate (<NUM>);
wherein the gas exhaust valve (<NUM>) comprises a metal sheet (<NUM>) and a fixing part (<NUM>), and the metal sheet (<NUM>) seals the gas vent (<NUM>);
the sealing part (<NUM>) is arranged between the metal sheet (<NUM>) and the cover plate (<NUM>) for sealing a gap between the metal sheet (<NUM>) and the cover plate (<NUM>);
the fixing part (<NUM>) is connected to the metal sheet (<NUM>), and the metal sheet (<NUM>) is fixed to the cover plate (<NUM>) by the fixing part (<NUM>); and
the fixing part (<NUM>) is configured to deform in response to an increase in temperature in such a manner that the metal sheet (<NUM>) gets out of the state of sealing the gas vent (<NUM>);
wherein the cover assembly (<NUM>) further comprises a pressing block (<NUM>), and the pressing block (<NUM>) is fixed to the cover plate (<NUM>);
the pressing block (<NUM>) comprises a second center hole (<NUM>), and the second center hole (<NUM>) is opposite to the gas vent (<NUM>); and
the pressing block (<NUM>) presses against a surface of the fixing part (<NUM>) facing away from the sealing part (<NUM>), and the fixing part (<NUM>) is fixed to the cover plate (<NUM>) by the pressing block (<NUM>);
wherein along a thickness direction (Z) of the cover assembly (<NUM>), a projection of the pressing block (<NUM>) does not overlap a projection of the metal sheet (<NUM>).