Patent Description:
The present application relates to the technical field of energy storage devices, and in particular, to a secondary battery, a battery pack and an electric device.

A secondary battery includes a case and an electrode assembly, and an electrolyte is accommodated in the case, and the electrolyte can infiltrate the electrode assembly, thereby prolonging a service life of the secondary battery. The electrode assembly includes a body and a tab. For a structure where the tab extends from a side portion of the body, it is difficult for the electrolyte to infiltrate the electrode assembly from bottom. After the secondary battery works for a long time, an interior of the electrode assembly lacks the electrolyte, and electrolyte wettability of the secondary battery is poor, and a lithium precipitation phenomenon is prone to occur, which affects the service life of the secondary battery.

In view of the above, embodiments of the present application provide a secondary battery, a battery pack, and an electric device. The secondary battery is used to solve a problem in the prior art that poor electrolyte wettability of the secondary battery leads to a low service life of the secondary battery.

The embodiments of the present application provide a secondary battery, and the secondary battery includes:.

Optionally, each of the tabs includes a body portion and an extension portion, the body portion extends from the corresponding side portion, and the extension portion is bent relative to the body portion.

At least part of the body portion is located in the avoiding portion.

Optionally, the flow guiding component is a plate-shaped structure.

Along a width direction, one end of the flow guiding component is fixedly connected to the connecting component, and the other end is attached to the side portion.

Optionally, along the width direction, a width of the flow guiding component is smaller than a width of the connecting components.

Optionally, along a height direction, a height of the flow guiding component is greater than or equal to a height of the electrode assembly.

Each of the connecting components includes a first connecting portion and a second connecting portion, the first connecting portion is configured to connect to the cap assembly, and the second connecting portion is configured to connect to a tab, and the first connecting portion is bent relative to the second connecting portion.

Along the height direction, one end of the flow guiding component extends to a position where the first connecting portion and the second connecting portion are bent relative to each other, and the other end of the flow guiding component abuts against a bottom of the case; or the secondary battery further includes an insulating membrane located between the case and the electrode assembly, and along the height direction, one end of the flow guiding component extends to the position where the first connecting portion and the second connecting portion are bent relative to each other, and the other end of the flow guiding component abuts against a bottom of the insulating membrane.

Optionally, the electrode assembly includes a plurality of anodic plates, a plurality of cathodic plates and a plurality of separators, and the separators are located between the anodic plates and the cathodic plates that are adjacent.

Along the width direction, each of the separators includes first end portions that extend beyond the anodic plates and the cathodic plates.

A thickness of the flow guiding component is greater than or equal to a distance between the first end portion and the connecting component.

Optionally, the flow guiding component includes an anode flow guiding component and a cathode flow guiding component, where the anode flow guiding component and the cathode flow guiding component are respectively located on two sides of the electrode assembly along the width direction.

At a cathode of the electrode assembly, each of the cathodic plates includes a third end portion that extends beyond the anodic plates, and along the width direction, the third end portion is located between a first end portion and the anodic plates.

A first thickness D<NUM> of the cathode flow guiding component satisfies D<NUM> ≤ d<NUM> + d<NUM>; where d<NUM> is a distance between the first end portion and the connecting component, and d<NUM> is a distance between the first end portion and the third end portion.

At an anode of the electrode assembly, each of the anode plates includes a second end portion that extends beyond the cathodic plates, and along the width direction, the second end portion is located between the cathodic plates and the first end portion.

A second thickness D<NUM> of the anode flow guiding component satisfies D<NUM> ≤ d<NUM> + d<NUM>,
where d<NUM> is a distance between the first end portion and the connecting component, and d<NUM> is a distance between the first end portion and the second end portion.

Optionally, a thickness d of the flow guiding component satisfies a following formula: <MAT> where L<NUM> is a total length of the anodic plates or a total length of the cathodic plates; W<NUM> is a width of an active material layer of the anodic plates or a width of an active material layer of the cathodic plates;.

Optionally, the avoiding portion is a recess.

Along the height direction, the recess includes a first side wall and a second side wall disposed oppositely, and the first side wall and the second side wall abut against the body portion, respectively.

Along the width direction, the recess includes a third side wall, and the third side wall abuts against the body portion.

Embodiments of the present application also provide a battery pack including a secondary battery as described above.

Embodiments of the present application also provide an electric device, including a secondary battery as described above.

In the present application, after the flow guiding component is provided, part of the electrolyte injected into the accommodating cavity of the case could be absorbed by the flow guiding component, and the electrolyte could diffuse in the flow guiding component. Since the flow guiding component is in contact with the electrode unit of the electrode assembly, the electrolyte in the flow guiding component which is in contact with the electrode unit enters the electrode unit as the electrolyte inside the electrode unit is consumed, and thus the electrolyte in the accommodating cavity is continuously passed into the electrode unit, the electrolyte wettability in the electrode assembly is improved, the risk of lithium precipitation for the electrode assembly is reduced, and the service life of the secondary battery is improved. Meanwhile, when the secondary battery swells during operation, the electrode assembly and the case could compress the flow guiding component, so that the flow guiding component could release the electrolyte stored therein, the liquid retention capacity of the secondary battery is improved and the service life of the secondary battery is further improved.

At the same time, after the flow guiding component is provided with the avoiding portion, the tab could be avoided, that is, the tab could extend through the avoiding portion, so as to realize fixed connection between the tab and the connecting component.

For a better understanding on the technical solutions of the present application, embodiments of the present application are described in detail below with reference to the accompanying drawings.

It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort shall fall within the protection scope of the present application.

The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, but are not intended to limit the present application. The singular forms of "a", "description" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

It should be understood that the term "and/or" used herein is only an association relationship describing associated objects, which means that there may be three types of relationships; for example, A and/or B can mean that there are three cases: A exists alone, both A and B exist, and B exists alone. In addition, the character "/" in this text generally indicates that the associated objects before and after are in an "or" relationship.

It should be noted that the "upper", "lower", "left", "right" and other directional words described in the embodiments of the present application are described from an angle shown in the drawings, and should not be construed as any limitation to the embodiments of the present application. In addition, in the context, it also needs to be understood that when it is mentioned that an element is connected "above" or "under" another element, it can not only be directly connected "above" or "under" the other element, but also be indirectly connected "above" or "under" another element through an intermediate element.

Please refer to <FIG>, where <FIG> is a top view of a secondary battery provided by the present application in a specific embodiment; <FIG> is an exploded diagram of <FIG>; <FIG> is a schematic structural diagram of an electrode assembly in <FIG>; <FIG> is a schematic structural diagram showing a connection between a connecting component and a flow guiding component in <FIG>; <FIG> is a schematic structural diagram of the flow guiding component in <FIG>; <FIG> is a sectional view taken along a line A-A of <FIG>; <FIG> is a partial enlarged diagram of part I in <FIG>; <FIG> is a schematic diagram of a cathodic plate, an anodic plate and a separator in <FIG>; <FIG> is a sectional view taken along a line B-B of <FIG>.

An embodiment of the present application provides a secondary battery. As shown in <FIG>, the secondary battery includes an electrode assembly <NUM>, a cap assembly <NUM>, and a case <NUM>. The case <NUM> may be a hexahedral shape or other shapes, and the case <NUM> forms an accommodating cavity configured to accommodate the electrode assembly <NUM> and an electrolyte. One end of the case <NUM> is provided with an opening so that the electrode assembly <NUM> could be placed into the accommodating cavity of the case <NUM> through the opening. The case <NUM> may include a metal material, such as aluminum or aluminum alloy, and may also include an insulating material, such as plastic.

As shown in <FIG>, the electrode assembly <NUM> includes an electrode unit <NUM> and tabs <NUM>. The electrode unit <NUM> includes two side portions <NUM> disposed oppositely along a length direction X. In the secondary battery, the two tabs <NUM> extend from the two side portions <NUM> of the electrode unit <NUM>, respectively. As shown in <FIG>, the electrode unit <NUM> includes an anodic plate <NUM>, a cathodic plate <NUM>, and a separator <NUM>, where the separator <NUM> is located between the adjacent anodic plate <NUM> and the cathodic plate <NUM> to space the anodic plate <NUM> from the cathodic plate <NUM>.

In a specific embodiment, the anodic plate <NUM>, the separator <NUM>, and the cathodic plate <NUM> are sequentially stacked and wound to form the electrode unit <NUM> of the electrode assembly <NUM>. That is, the electrode unit <NUM> has a winding structure. In a second specific embodiment, the anodic plate <NUM>, the separator <NUM>, and the cathodic plate <NUM> are sequentially stacked to form the electrode unit <NUM> of the electrode assembly <NUM>, and the electrode unit <NUM> has a laminated structure. At the same time, there are gaps after the electrode unit <NUM> is formed, and the electrolyte could enter the electrode unit <NUM> through the gaps to infiltrate the anodic plate <NUM> and the cathodic plate <NUM>.

The anodic plate <NUM> includes an anode current collector (e.g., copper foil) and an anode active material layer (e.g., graphite, carbon or silicon) coated on a surface of the anode current collector. The cathodic plate <NUM> includes a cathode current collector (e.g., aluminum foil) and a cathode active material layer (e.g., a ternary material, lithium iron phosphate, or lithium cobaltate) coated on a surface of the cathode current collector. At an anode of the electrode assembly <NUM>, the tab <NUM> is connected to the anodic plate <NUM> and extends from the electrode unit <NUM>, and the tab <NUM> may be directly formed from the anode current collector by cutting. At a cathode of the electrode assembly <NUM>, the tab <NUM> is connected to the cathodic plate <NUM> and extends from the electrode unit <NUM>, and the tab <NUM> may be directly formed from the cathode current collector by cutting.

As shown in <FIG>, the cap assembly <NUM> includes a cap plate <NUM> and electrode terminals <NUM>, the cap plate <NUM> is fixed to the opening of the case <NUM>, thereby sealing the electrode assembly <NUM> and the electrolyte in the accommodating cavity of the case <NUM>. The electrode terminals are arranged on the cap plate <NUM> and include an anode electrode terminal and a cathode electrode terminal. The anode electrode terminal and the cathode electrode terminal are respectively electrically connected to a corresponding tab <NUM> through a connecting component <NUM>, and the cap plate <NUM> is provided with an explosion-proof opening <NUM>.

Further, as shown in <FIG> and <FIG>, the secondary battery further includes a flow guiding component <NUM> located in the accommodating cavity of the case <NUM>. The flow guiding component <NUM> can absorb the electrolyte and includes an anode flow guiding component <NUM> and a cathode flow guiding component <NUM>. At least part of the flow guiding component <NUM> is in contact with a corresponding side portion <NUM>, and the two flow guiding components <NUM> are in contact with the electrolyte. In the embodiment, as shown in <FIG>, the two flow guiding components <NUM> of the secondary battery have a split structure, and there is no connecting part between the two.

As shown in <FIG>, the flow guiding component <NUM> is provided with an avoiding portion <NUM>, and the avoiding portion <NUM> is configured to avoid the tab <NUM>.

In the present application, after the flow guiding component <NUM> is provided, part of the electrolyte injected into the accommodating cavity of the case <NUM> could be absorbed by the flow guiding component <NUM>, and the electrolyte could diffuse in the flow guiding component <NUM>. Since the flow guiding component <NUM> is in contact with the electrode unit <NUM> of the electrode assembly <NUM>, the electrolyte in the flow guiding component <NUM> which is in contact with the electrode unit <NUM> enters the electrode unit <NUM> as the electrolyte in the electrode unit <NUM> is consumed, and thus the electrolyte in the accommodating cavity is continuously passed into the electrode unit <NUM>, the electrolyte wettability in the electrode assembly <NUM> is improved, the risk of lithium precipitation for the electrode assembly <NUM> is reduced, and the service life of the secondary battery is increased. Meanwhile, when the secondary battery swells during operation, the electrode assembly <NUM> and the case <NUM> could compress the flow guiding component <NUM>, so that the flow guiding component <NUM> could release the electrolyte stored therein, the liquid retention capacity of the secondary battery is improved, and the service life of secondary battery is further improved.

At the same time, after the flow guiding component <NUM> is provided with the avoiding portion <NUM>, the tab <NUM> could be avoided, that is, the tab <NUM> could extend through the avoiding portion <NUM>, so as to realize fixed connection between the tab <NUM> and the connecting component <NUM>. In addition, when the connection between the tab <NUM> and the connecting component <NUM> is a welded connection, the arrangement of the avoiding portion <NUM> could also reduce a risk of damaging the flow guiding component <NUM> by heat during a welding process, and improve the service life of the flow guiding component <NUM> and the secondary battery.

As shown in <FIG>, the connecting component <NUM> includes a first connecting portion <NUM> and a second connecting portion <NUM>, where the first connecting portion <NUM> extends to a top of the electrode assembly <NUM> for connecting to the cap assembly <NUM>. The second connecting portion <NUM> extends to a side portion of the electrode assembly <NUM> for connecting to the tab <NUM>.

Further, as shown in <FIG>, the tab <NUM> includes a body portion <NUM> and an extension portion <NUM>, where the body portion <NUM> extends from the side portion <NUM> of the electrode unit <NUM>, and the extension portion <NUM> extends from the electrode unit <NUM> and then bends, that is, the extension portion <NUM> is bent relative to the body portion <NUM>, where the body portion <NUM> and the cap assembly <NUM> are connected by the connecting component <NUM>. At the same time, at least part of the body portion <NUM> is located in the avoiding portion <NUM>.

In this embodiment, as shown in <FIG>, in the tab <NUM>, the body portion <NUM> is attached to the side portion <NUM>, and there is a gap between the extension portion <NUM> and the body portion <NUM> along the length direction X. Therefore, when the flow guiding component <NUM> abuts against the side portion <NUM>, there is a risk of interference between the flow guiding component <NUM> and the body portion <NUM> of the tab <NUM>. In this embodiment, by providing the flow guiding component <NUM> with an avoiding portion <NUM>, the body portion <NUM> could be avoided, so that the flow guiding component <NUM> could be attached to the side portion <NUM> without being affected by the body portion <NUM>, and thus the wettability of the flow guiding component <NUM> is improved by the electrode assembly <NUM>, and at the same time, the flow guiding component <NUM> does not interfere with the body portion <NUM>, a size of the secondary battery in a length direction could be reduced, and energy density of the secondary battery could be increased. After the secondary battery is formed, at least part of the body portion <NUM> is located in the avoiding portion <NUM>.

Specifically, as shown in <FIG> and <FIG>, the avoiding portion <NUM> includes a recess provided on the flow guiding component <NUM>. Along a height direction Z, the recess includes a first side wall <NUM> and a second side wall <NUM> disposed oppositely, and at least part of the body portion <NUM> is located in the recess. And along the height direction Z, the first side wall <NUM> and the second side wall <NUM> abut against the body portion <NUM>, respectively.

Therefore, in this embodiment, the position of the flow guiding component <NUM> could be restricted along the height direction Z by the body portion <NUM> of the tab <NUM>, thereby preventing the flow guiding component <NUM> from moving along the height direction Z relative to the tab <NUM>, and improving stability of the flow guiding component <NUM> in the secondary battery.

At the same time, as shown in <FIG> and <FIG>, the recess includes a third side wall <NUM> along a width direction Y, and the third side wall <NUM> abuts against the body portion <NUM>.

Therefore, in this embodiment, the position of the flow guiding component <NUM> could be restricted along the width direction Y by the body portion <NUM> of the tab <NUM>, thereby preventing the flow guiding component <NUM> from moving along the width direction Y relative to the tab <NUM>, and further improving the stability of flow guiding component <NUM> in the secondary battery.

In addition, when the avoiding portion <NUM> is a recess, the body portion <NUM> may extend beyond the recess along a side far away from the third side wall <NUM>, or the body portion may also be all located in the recess. Therefore, at least part of the body portion <NUM> is located in the recess.

In above embodiments, as shown in <FIG> and <FIG>, the flow guiding component <NUM> has a plate-shaped structure, and along the width direction Y, one end surface of the flow guiding component <NUM> is attached to the side portion <NUM> of the electrode unit <NUM>, and the other end surface is fixedly connected to the connecting component <NUM>.

In this embodiment, contact area between the flow guiding component <NUM> of the plate-shaped structure and the side portion <NUM> is relatively large, so that a capability of the flow guiding component <NUM> to transport the electrolyte into the electrode assembly <NUM> could be improved, thereby further improving the service life of the secondary battery. At the same time, by fixedly connecting the flow guiding component <NUM> and the connecting component <NUM>, the flow guiding component <NUM> could be fixed in the case <NUM>, where the flow guiding component <NUM> and the connecting component <NUM> may be connected by gluing.

As shown in <FIG>, along the width direction Y, a width of the flow guiding component <NUM> is smaller than a width of the connecting component <NUM>, and at the same time, the width of the flow guiding component <NUM> is also smaller than a width of the corresponding side portion <NUM>.

It can be understood that the larger the area of the flow guiding component <NUM>, the greater the amount of the electrolyte it can absorb, and the larger the contact area between the flow guiding component <NUM> and the side portion <NUM>, and the more the electrolyte it can transport into the electrode unit <NUM>. Therefore, increasing the contact area between the flow guiding component <NUM> and the electrode unit <NUM> helps to improve the wettability of the electrode assembly <NUM>. However, in order to ensure that the tab <NUM> and the connecting component <NUM> could be connected, the width of the flow guiding component <NUM> could not exceed the width of the connecting component <NUM>. In this embodiment, the width of the flow guiding component <NUM> needs be as large as possible to increase the contact area between the flow guiding component <NUM> and the side portion <NUM> but avoid occupying too much space.

On the other hand, as shown in <FIG>, along the height direction Z, a height of the flow guiding component <NUM> is greater than or equal to a height of the electrode assembly <NUM>, so as to ensure that the electrolyte at the bottom of the case <NUM> could be transported to the electrode assembly <NUM> through the flow guiding component <NUM>, and when the height of the flow guiding component <NUM> is equal to the height of the electrode assembly <NUM>, the volume of the flow guiding component <NUM> could be reduced and the energy density of the secondary battery could be increased while the flow guiding component <NUM> is ensured to have a high capability to transport the electrolyte.

In the secondary battery, the first connecting portion <NUM> and the second connecting portion <NUM> of the connecting component <NUM> are bent relative to each other. The first connecting portion <NUM> is configured to connect to the cap assembly <NUM>, and the second connecting portion <NUM> is configured to connect to the tab <NUM> Therefore, the first connecting portion <NUM> and the second connecting portion <NUM> are bent at the top of the electrode assembly <NUM>. Therefore, along the height direction Z, one end (upper end) of the flow guiding component <NUM> extends to a position where the first connecting portion <NUM> and the second connecting portion <NUM> are bent relative to each other, and the other end (lower end) abuts against the bottom of the case <NUM>.

Or, when the secondary battery includes an insulating membrane <NUM>, the insulating membrane <NUM> is located in the inner cavity of the case <NUM>; and, along the height direction Z, the upper end of the flow guiding component <NUM> extends to the position where the first connecting portion <NUM> and the second connecting portion <NUM> are bent relative to each other, and the lower end abuts against the bottom of the insulating membrane <NUM>.

Specifically, as shown in <FIG>, the electrode unit <NUM> includes a plurality of anodic plates <NUM>, a plurality of cathodic plates <NUM>, and a plurality of separators <NUM>. The separator <NUM> is located between adjacent anodic plate <NUM> and cathodic plate <NUM>. The separator <NUM> is used to isolate the anodic plate <NUM> from the cathodic plate <NUM>. In order to ensure complete isolation between the two plates, a size of the separator <NUM> is larger than a size of the anodic plate <NUM> and a size of the cathodic plate <NUM>. As shown in <FIG>, along the length direction X, the separator <NUM> has first end portions 113a extending beyond the anodic plate <NUM> and the cathodic plate <NUM>, and a thickness of the flow guiding component <NUM> is greater than or equal to a distance between the first end portion 113a and the connecting component <NUM>.

Since the first end portions 113a of the separator <NUM> extend beyond the anodic plate <NUM> and the cathodic plate <NUM>, for the electrode unit <NUM>, the first end portions 113a of the separator <NUM> are the most outer end along the width direction Y, and therefore, when the flow guiding component <NUM> is connected to the connecting component <NUM> and abuts against the electrode assembly <NUM>, the flow guiding component <NUM> first contacts the first end portion 113a. When the thickness of the flow guiding component <NUM> is too small (less than the distance between the connecting component <NUM> and the first end portion 113a), the flow guiding component <NUM> cannot abut against the electrode assembly <NUM>, or cannot be fixedly connected to the connecting component portion <NUM>. Therefore, in order to achieve fixing the flow guiding component <NUM> in the secondary battery and transporting the electrolyte to the electrode unit <NUM>, the thickness of the flow guiding component <NUM> is greater than or equal to the distance between the first end portion <NUM> a and the connecting component <NUM>.

Further, as shown in <FIG>, the electrode unit <NUM> includes a cathode and an anode, the flow guiding component <NUM> includes an anode flow guiding component <NUM> and a cathode flow guiding component <NUM>, and the anode flow guiding component <NUM> is located on the anode side of the electrode unit <NUM>, while the cathode flow guiding component <NUM> is located on the cathode side of the electrode unit <NUM>. On the cathode side of the electrode unit <NUM>, the cathodic plate <NUM> includes a third end portion 112a extending beyond the anodic plate <NUM>, and along the width direction Y, the third end portion 112a portion is located between the first end portion 113a and the anodic plate <NUM>, that is, the third end portion 112a extends beyond the anodic plate <NUM>, but does not extend beyond the first end portion 113a of the separator <NUM>.

A first thickness D<NUM> of the cathode flow guiding component <NUM> satisfies D<NUM> ≤ d<NUM> + d<NUM> , where d<NUM> is the distance between the first end portion 113a and the connecting component <NUM>, and d<NUM> is a distance between the first end portion 113a and the third end portion 112a. That is, the first thickness of the cathode flow guiding component <NUM> satisfies: d<NUM> ≤ D<NUM> ≤ d<NUM> + d<NUM>.

As described above, when the first thickness D<NUM> of the cathode flow guiding component <NUM> is smaller than d<NUM>, the cathode flow guiding component <NUM> cannot contact with the electrode unit <NUM>, and when the first thickness D<NUM> of the cathode flow guiding component <NUM> is greater than d<NUM>, the cathode flow guiding component <NUM> contacts with the electrode unit <NUM> and then squeezes the separator <NUM>, and when the first thickness D<NUM> of the cathode flow guiding component is too large (D<NUM> > d<NUM> + d<NUM>), the cathode flow guiding component <NUM> not only squeezes the separator <NUM>, but also squeezes the third end portion 112a of the cathodic plate <NUM>, causing that the cathodic plate <NUM> is bent inward (toward a center of the electrode assembly <NUM> ), which leads to that the cathodic plate <NUM> contacts with the anodic plate <NUM>, thereby causing the cathode and anode of the electrode unit <NUM> to be short-circuited.

Therefore, in this embodiment, when the first thickness D<NUM> of the cathode flow guiding component <NUM> satisfies d<NUM> ≤ D<NUM> ≤ d<NUM> + d<NUM>, it could be ensured that the cathode flow guiding component <NUM> contacts with the cathode side of the electrode unit <NUM>, while the cathodic plate <NUM> and the anodic plate <NUM> are prevented from being short-circuited.

At the same time, at the anode of the electrode unit <NUM>, the anode plate <NUM> includes a second end portion 111a extending beyond the cathodic plate <NUM>, and along the width direction Y, the second end portion 111a is located between the cathodic plate <NUM> and the first end portion 113a, that is, the first end 113a extends beyond the cathodic plate <NUM>, but does not extend beyond the first end portion 113a of the separator <NUM>.

A second thickness D<NUM> of the anode flow guiding component <NUM> satisfies D<NUM> ≤ d<NUM> + d<NUM>, where d<NUM> is the distance between the first end portion 113a and the connecting component <NUM>, and d<NUM> is a distance between the first end portion 113a and the second end portion 111a.

Similar to the cathode flow guiding component <NUM>, when the second thickness of the anode flow guiding component <NUM> satisfies d<NUM> ≤ D<NUM> ≤ d<NUM> + d<NUM>, the anodic plate <NUM> on the anode side and the cathodic plate <NUM> could be prevented from being short-circuited, and it could be ensured that the anode flow guiding component <NUM> abuts against the anode side of the electrode unit <NUM>.

It should be noted that the second thickness D<NUM> of the anode flow guiding component <NUM> and the first thickness D<NUM> of the cathode flow guiding component <NUM> may be the same or different, and specific values of D<NUM> and D<NUM> can be determined according to parameters of the anode side and the cathode side of the electrode unit.

In addition, a thickness d of the flow guiding component <NUM> satisfies the following formula: <MAT> where L<NUM> is a total length of the anodic plates <NUM>, or a total length of the cathodic plates <NUM>, and the total length of the anodic plates <NUM> refers to the total length of the anodic plates <NUM> after the electrode assembly <NUM> is spread, that is, a sum of the lengths of the anodic plates <NUM>; W<NUM> is a width of an active material layer on the anodic plates <NUM> or a width of an active material layer on the cathodic plates <NUM>, as shown in <FIG>; as shown in <FIG>, G is a distance between adjacent anodic plates <NUM>, or a distance between adjacent cathodic plates <NUM>; L<NUM> is a total length of the separators <NUM>, which represent, the total length of the separators <NUM> after the electrode assembly <NUM> is spread, that is a sum of the lengths of the separators <NUM>; W<NUM> is a width of the separators <NUM>, as shown in <FIG>; H<NUM> is a height of the electrode assembly <NUM>, as shown in <FIG>; W<NUM> is a width of the connecting component <NUM>, as shown in <FIG>; ρ<NUM> is a liquid retention coefficient of the separators <NUM>; ρ<NUM> is a liquid retention coefficient of the flow guiding component <NUM>.

As described above, each parameter in formula (<NUM>) is a measurable parameter or a known parameter, and the thickness d of the flow guiding component <NUM> can be calculated by this formula.

Embodiments of the present application also provide a battery pack, including a secondary battery described in a foregoing embodiment.

Claim 1:
A secondary battery, wherein the secondary battery comprises:
a case (<NUM>), comprising an opening and an inner cavity, an electrolyte being comprised in the inner cavity;
a cap assembly (<NUM>), covering the opening;
an electrode assembly (<NUM>), located in the inner cavity and comprising an electrode unit (<NUM>) and tabs (<NUM>); along a length direction, the electrode unit (<NUM>) comprising two side portions (<NUM>) disposed oppositely, and the tabs (<NUM>) extending from the side portions (<NUM>), the length direction being perpendicular to a covering direction in which the cap assembly (<NUM>) covers the opening of the case (<NUM>);
connecting components (<NUM>), configured to connect the tabs (<NUM>) and the cap assembly (<NUM>); and
a flow guiding component, located between a corresponding connecting component and a corresponding side portion and connected to the connecting component (<NUM>), at least part of the flow guiding component (<NUM>) being in contact with the corresponding side portion (<NUM>), and the flow guiding component (<NUM>) being in contact with the electrolyte, and the flow guiding component (<NUM>) absorbing the electrolyte;
wherein, the flow guiding component (<NUM>) is provided with an avoiding portion (<NUM>) configured to avoid the tabs (<NUM>).