Patent Description:
The present disclosure relates to an electrode assembly for secondary battery including a separator with a notch groove formed therein and a secondary battery including the same.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing, and as part thereof, the fields that are being studied most actively are the fields of power generation and power storage using electrochemistry.

At present, a secondary battery is a representative example of an electrochemical device that utilizes such electrochemical energy, and the range of use thereof tends to be gradually expanding.

In recent years, as mobile devices, such as portable computers, portable phones, and cameras, have been increasingly developed, the demand for secondary batteries has also sharply increased as an energy source for the mobile devices. Among such secondary batteries is a lithium secondary battery exhibiting high charge/discharge characteristics and lifetime characteristics and being environmentally friendly, in which much research has been carried out and which is now commercialized and widely used.

<CIT> relates to a stack type battery and battery module, <CIT> relates to a battery in which a positive electrode plate and a negative electrode plate are laminated via a separator and <CIT> relates to a battery cell that is used in a secondary battery such as a lithium-ion battery.

Generally, the secondary battery has a structure in which a non-aqueous electrolyte is impregnated into electrode assembly comprising a positive electrode, a negative electrode, and a porous separator.

At this time, the electrodes such as the positive electrode and the negative electrode must be completely separated, but there is a problem that they contact each other and a short circuit occurs due to contraction of the separator, protrusion of the electrode active material, and the like.

Generally, when a positive electrode active material and a negative electrode active material are short-circuited, the cell voltage drops along with small heat and the reaction is terminated. In case of a hard short circuit in which the positive electrode foil and the negative electrode active material are directly short-circuited, heat generation in mechanical, electrical or thermal abuse conditions leads to a thermal runaway, which greatly threatens safety.

In particular, such a hard short circuit occurs in the order of short circuit between electrodes, ignition and the like while deformation of the separator and the electrode occurs mainly due to the contraction of the separator occurring at a high temperature.

<FIG> schematically shows a conventional electrode assembly, and <FIG> schematically shows a phenomenon in which the electrode assembly is deformed at a high temperature to occur a hard short circuit.

Referring to <FIG> and <FIG>, a stacked body <NUM> includes a positive electrode <NUM>, a negative electrode <NUM>, and a separator <NUM> interposed between the positive electrode <NUM> and the negative electrode <NUM>, with the separator <NUM> being also located at the outermost surface on both sides, and the stacked body is fixed by at least three pairs of fixing members <NUM> attached in the stacking direction for fixing between the separators <NUM> located at the outermost surface on both sides of the stacked body <NUM>.

When such a stacked body <NUM> is subsequently used after being manufactured as a secondary battery, contraction of the separator <NUM> occurs at a high temperature. Specifically, as the temperature increases, the contraction of the separator <NUM> is accelerated, and there is a predetermined difference depending on the material. However, the contraction in the MD/TD direction at <NUM> is about <NUM>% to <NUM>%, and the contraction in the MD/TD direction at <NUM> exceeds <NUM>%, respectively. At this time, the contraction of the separator <NUM> occurs in a narrow space between the fixing members <NUM>, whereby the positive electrode <NUM> is deformed together in the stacking direction as in A, and a hard short circuit between the positive electrode <NUM> and the negative electrode <NUM> occurs, which leads to ignition.

Therefore, there is an urgent need to develop a technology that can solve such problems and delay or prevent hard short circuits between electrodes due to contraction of the separator at high temperatures and thus enhance safety at high temperature.

The present disclosure has been made to solve the above-mentioned problems and other technical problems that have yet to be resolved.

Specifically, an object of the present disclosure is to provide an electrode assembly for secondary battery that can prevent hard short circuits between electrodes and improve high temperature safety by forming a notch groove in the separator of the stacked body and thus inducing a high-temperature contraction direction and path, and a secondary battery including the same.

According to one aspect of the present disclosure, there is provided an electrode assembly for secondary battery comprising:.

At this time, the notch groove is formed in at least two pairs, and the notch grooves may be formed in a diagonal direction and a linear direction of each surface perpendicular to the protruding direction of the electrode tab.

Further, the notch groove may be formed at a position that does not interfere with the electrode tab.

A planar shape of the notch groove may be a slit-like shape, a polygonal shape, a circular shape, or an elliptical shape.

Meanwhile, the planar shape of the notch groove may be a slit-like shape or a triangular shape.

The fixing member may include polyimide.

The fixing member may be configured such that a pair of fixing members are attached at positions facing each other on both sides parallel to the protruding direction of the electrode tab, and the other at least one pair of fixing members are attached at a position facing each other on both sides parallel to the protruding direction of the electrode tab at a position spaced apart from the pair of fixing members.

Meanwhile, the electrode assembly may be a lamination and stack type electrode assembly or a stack and folding type electrode assembly.

According to another aspect of the present disclosure, there is provided a secondary battery in which the electrode assembly according to the present disclosure is built in a secondary battery case together with an electrolyte.

Hereinafter, the present disclosure will be described in more detail for a better understanding of the present disclosure.

The technical terms provided herein is merely used for the purpose of describing particular embodiments only, and is not intended to be limiting of the present disclosure.

It should be understood that the terms "comprise", "include", "have", etc. are used herein to specify the presence of stated features, integers, steps, components or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

According to one embodiment of the present disclosure, there is provided an electrode assembly for secondary battery comprising:.

<FIG> schematically shows an electrode assembly <NUM> for secondary battery according to an embodiment of the present disclosure.

Referring to <FIG>, the electrode assembly <NUM> according to the present disclosure includes a stacked body <NUM> that includes a positive electrode <NUM>, a negative electrode <NUM>, and a separator <NUM> interposed between the positive electrode <NUM> and the negative electrode <NUM>, and present at the outermost surface on both sides; and at least three pairs of fixing members <NUM> attached in the stacking direction for fixing between the separators <NUM> located at the outermost surface on both sides of the stacked body <NUM>.

The fixing member <NUM> is provided for fixing the stacked body <NUM>, and may include at least two pairs of fixing members for firmly fixing the stacked body <NUM>.

At this time, the fixing member <NUM> is configured such that a pair of fixing members 114a are attached at positions facing each other on both sides parallel to the protruding direction of the electrode tabs 111a and 112a, and the other at least one pair of fixing members 114b and 114c are attached at a position facing each other on both sides parallel to the protruding direction of the electrode tabs 111a and 112a at a position spaced apart from the pair of fixing members 114a.

As the material constituting such a fixing member <NUM>, various materials used for the battery can be selected, but specifically, a material that has both heat resistance and insulating property and thus does not have a short circuit problem is preferable, and for example, it may include polyimide.

Further, according to the present disclosure, the separator <NUM> includes a pair of notch grooves <NUM> that are formed one by one on one surface perpendicular to the protruding direction of the electrode tabs 111a and 112a and the other surface located in a diagonal direction thereof, and the notch groove <NUM> may be formed at a position that does not interfere with the electrode tabs 111a and 112a, so as to prevent the electrode tab having a first polarity and the electrode active material layer having a second polarity from contacting with each other and causing a short circuit.

That is, for example, when the notch groove <NUM> is formed at a position where it overlaps with the electrode tabs 111a and 112b, there is a possibility that the positive electrode tab 111a and the negative electrode active material layer of the negative electrode <NUM> comes into contact with each other at the notch groove <NUM> portion to cause a short circuit. Therefore, in order to prevent these problems, the tabs 111a and 112a are formed at positions that do not interfere with each other.

Additionally, a pair of notch grooves <NUM> are specifically formed at horizontally and vertically symmetrical positions with respect to each other.

<FIG> schematically shows a phenomenon in which the separator contracts and deforms when the electrode assembly <NUM> is exposed to a high temperature.

Referring to <FIG>, if a pair of notch grooves <NUM> are formed in the separator <NUM> as in the present disclosure, the separator contracts as well when the electrode assembly <NUM> is exposed to a high temperature. However, the pair of previously formed notch grooves <NUM> causes tearing of the separator in the form of connecting a pair of notch grooves <NUM>, whereby contraction does not occur between the fixing members <NUM>, and the positive electrode <NUM> and the separator <NUM> are not deformed in the stacking direction, thereby capable of preventing a hard short circuit, reducing the possibility of ignition and thus improving battery safety.

That is, the pair of notch grooves <NUM> causes tearing of the separator <NUM> while inducing a path in which the separator <NUM> is contracted, thereby preventing deformation of the positive electrode <NUM> or the negative electrode <NUM> in the stacking direction.

Meanwhile, a pair of notch grooves may be formed as shown in <FIG>, but at least two pairs may be formed.

<FIG> schematically shows an electrode assembly <NUM> in which two pairs of notch grooves are formed according to another embodiment of the present disclosure, and <FIG> schematically shows a phenomenon in which the separator contracts and deforms when the electrode assembly is exposed to a high temperature.

First, referring to <FIG>, the electrode assembly <NUM> includes a stacked body <NUM>, and three pairs of fixing members <NUM> attached in the stacking direction for fixing between the separators <NUM> located at the outermost surface on both sides of the stacked body <NUM>, similarly to those shown in <FIG>. However, the separator <NUM> includes two pairs of notch grooves <NUM> formed in a diagonal direction and a linear direction on each surface perpendicular to the protruding direction of the electrode tabs 211a and 212a, and the two pairs of notch grooves <NUM> are formed at positions that do not interfere with the electrode tabs 211a and 212a. Further, the two pairs of notch grooves <NUM> are specifically formed in horizontally and vertically symmetrical shapes with respect to each other.

Referring to <FIG>, when the electrode assembly <NUM> in which the two pairs of notch grooves <NUM> are formed in this way is also exposed to a high temperature, the separator <NUM> is contracted, and the separator <NUM> is torn and contracted in a vertical direction or a diagonal direction by the two pairs of notch grooves <NUM>. Therefore, similarly to the electrode assembly <NUM> in which a pair of notch grooves are formed, no contraction occurs between the fixing members <NUM>, and thus, the positive electrode or the negative electrode and the separator <NUM> are not deformed in the stacking direction, thereby capable of preventing a hard short circuit, reducing the possibility of ignition and thus improving battery safety.

If at least two pairs of notch grooves are formed in this way, it is possible to more reliably induce the path of contraction and tearing of the separator.

Meanwhile, the planar shape of the notch grooves is not limited, and can be formed in various ways. For example, it may be a slit-like shape, a polygonal shape, a circular shape, or an elliptical shape.

<FIG> schematically shows the planar shape of the notch groove <NUM>.

Referring to <FIG>, the notch groove <NUM> forms the planar shape into a triangular shape, so that the contraction and tearing directions of the separator <NUM> can be induced in a diagonal direction (<FIG>), or it forms the planar shape into a slit-like shape, so that the contraction and tearing direction of the separator <NUM> can be induced in a direction in which a slit is formed, that is, in a linear direction (<FIG>), or it forms the planar shape into a square shape, so that the contraction and tearing direction of the separator <NUM> can be induced in a direction extending from the lower corners on both sides (<FIG>), or it forms the planar shape into a circular or elliptical shape, so that the contraction and tearing direction of the separator <NUM> can be induced in various directions.

However, specifically, the planar shape of the notch groove <NUM> may be a slit-like shape or a triangular shape so that the direction of contraction and tearing of the separator is constant and thus can minimize influence on the fixing member.

Further, the size of the notch groove is preferably formed into a size in which a short circuit between the positive electrode and the negative electrode does not occur due to the formation of the notch groove, that is, a size in which the positive electrode active material layer and the negative electrode active material layer are not exposed. Within this range, the size is not limited.

Meanwhile, the electrode assembly is not limited as long as it has a shape including a stacked body, and may be a stack type electrode assembly, a lamination and stack type electrode assembly, or a stack and folding type electrode assembly. Specifically, it may be a lamination and stack type electrode assembly or a stack and folding type electrode assembly.

Since the detailed manufacturing method and configuration of such an electrode assembly are known in the art, a detailed description thereof will be omitted herein.

Meanwhile, according to another embodiment of the present disclosure, there is provided a secondary battery in which the electrode assembly is built in a secondary battery case together with an electrolyte.

At this time, the electrolyte may be a lithium salt non-aqueous electrolyte, and the secondary battery may be a lithium secondary battery.

Since the above configuration is well known in the art, a detailed description thereof will be omitted herein.

Claim 1:
An electrode assembly (<NUM>, <NUM>, <NUM>) for secondary battery comprising:
a stacked body (<NUM>, <NUM>) that includes a positive electrode (<NUM>, <NUM>, <NUM>), a negative electrode(<NUM>, <NUM>, <NUM>), and a separator (<NUM>, <NUM>, <NUM>, <NUM>) interposed between the positive electrode (<NUM>, <NUM>, <NUM>) and the negative electrode (<NUM>, <NUM>, <NUM>), with the separator (<NUM>, <NUM>, <NUM>, <NUM>) being located at the outermost surface on both sides; and
at least two pairs of fixing members (<NUM>, <NUM>, <NUM>) attached in the stacking direction for fixing between the separators (<NUM>, <NUM>, <NUM>, <NUM>) located at the outermost surface on both sides of the stacked body (<NUM>, <NUM>),
the separator (<NUM>, <NUM>, <NUM>, <NUM>) including at least one pair of notch grooves (<NUM>, <NUM>, <NUM>),
characterized in that the pair of notch grooves (<NUM>, <NUM>, <NUM>) are formed one by one on one surface perpendicular to a protruding direction of an electrode tab (111a, 112a, 211a, 212a) and the other surface located in a diagonal direction thereof.