Patent Description:
A secondary battery is high applicable to various product groups and has an electric characteristic of high energy density. The secondary battery is applied to not only portable electronic devices but also electric vehicles, hybrid electric vehicles, energy storage devices, and the like, driven by electric driving sources.

A battery pack applied to an electric vehicle or the like has a structure in which a plurality of battery modules, each including a plurality of battery cells, are connected in order to obtain a high output. Each battery cell includes positive and negative electrode current collectors, a separator, an active material, an electrolyte, and the like as an electrode assembly, and the battery cell may be repeatedly charged and discharged by an electrochemical reaction between the components.

Meanwhile, when the battery cell of the battery module is repeatedly charged and discharged, a swelling phenomenon occurs at the battery cell. In consideration of the swelling phenomenon, when the battery cells are stacked in a conventional battery module, the battery cells are disposed with regular intervals, or a compression pad is disposed between the battery cells to support the battery cells during swelling.

However, if the compression pad is used in the battery module or intervals are provided between the battery cells, the energy density per unit volume decreases. In addition, if the compression pad is used between the battery cells, the manufacturing process of the battery module becomes complicated, and the manufacturing cost of the battery module is increased. Thus, there is a need for improvement.

Also, since the swelling of the battery cells is related to the safety of the battery module, it may be very important to figure out whether swelling occurs or how much the battery cell deforms if swelling has occurred.

However, in the conventional art, generally, whether the battery cells in the battery module swell is guessed just by watching the external appearance of the battery module, or a swelling amount of battery cells is indirectly inferred through structural analysis and dimension measurement of an experimental module. For this reason it is more difficult for a general user as well as a person skilled in the art to determine exactly how the battery cells inside the battery module swell. Thus, there is needed a way for anyone such as a general person as well as a person skilled in the art to easily check whether the battery cells swell and how much the battery cells swell.

Further prior art is disclosed in <CIT>, <CIT>, <CIT> and <CIT>.

The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to providing a way of reducing swelling of battery cells without lowering an energy density of a battery module and a way of intuitionally figuring out a swelling amount of the battery cells easily at a place out of the battery module.

In one aspect of the present disclosure, there is provided a battery module, which allows a swelling amount of battery cells accommodated in a module housing to be intuitionally checked, the battery module comprising: a cell pressing plate accommodated in the module housing and disposed on at least one of both longitudinal side surfaces of a cell stack that is formed by stacking the battery cells; a swelling gauge provided to protrude from a surface of the cell pressing plate; and a gauge hole formed in the module housing, wherein a front end of the swelling gauge is pushed out of the module housing through the gauge hole by the swelling pressure of the battery cells, wherein the swelling gauge is provided with a scale arranged on a surface thereof and extending in the pushing direction of the swelling gauge.

The battery module may further comprise a buffering member interposed between the cell pressing plate and the module housing.

The buffering member may be a leaf spring.

The leaf spring may have at least one curve, and the leaf spring may have one surface in contact with the surface of the cell pressing plate and the other surface in contact with a surface of the module housing.

The leaf spring may have a leaf hole through which the swelling gauge passes, and the leaf spring may be disposed to contact the cell pressing plate in a state of being suspended from the swelling gauge.

The swelling gauge may be located at a center of the cell pressing plate.

The swelling gauge may include a first swelling gauge located at the center of the cell pressing plate; and a second swelling gauge and a third swelling gauge provided at both longitudinal edge regions of the cell pressing plate, respectively.

The module housing may be configured by assembling a top plate disposed at an upper portion of the cell stack, a bottom plate disposed at a lower portion of the cell stack and a pair of side plates having the gauge hole and respectively disposed at both side surfaces of the cell stack.

The top plate and the bottom plate may have bent portions prepared by bending both longitudinal corner regions thereof, the pair of side plates may have a stepped portion at which both longitudinal corner regions are stepped, and the stepped portion may be shape-matched with an inner side of the bent portion.

In another aspect of the present disclosure, there is also provided a battery pack, comprising the battery module described above.

According to an embodiment of the present disclosure, it is possible to provide a battery module, which may reduce swelling of battery cells without lowering an energy density of a battery module and intuitionally figure out a swelling amount of the battery cells easily at a place out of the battery module.

The effect of the present disclosure is not limited to the above effect, and other effects not mentioned herein will be clearly understood by those skilled in the art from the specification and the accompanying drawings.

<FIG> is a schematic perspective view showing a battery module according to an embodiment of the present disclosure, <FIG> is a partial exploded perspective view showing the battery module of <FIG>, and <FIG> is an exploded perspective view showing a cell pressing plate, a buffering member and a side plate according to an embodiment of the present disclosure.

Referring to <FIG>, a battery module <NUM> according to an embodiment of the present disclosure includes a cell stack <NUM>, a module housing <NUM>, a cell pressing plate <NUM>, a buffering member <NUM> and a swelling gauge <NUM>.

The cell stack <NUM> may be an aggregate of battery cells <NUM>, which are pouch-type battery cells <NUM> having broad surfaces facing each other. In other words, in this embodiment, the cell stack <NUM> is configured such that the pouch-type battery cells <NUM> are provided to stand up side by side and stacked in a horizontal direction so as to be disposed as densely as possible in the module housing <NUM>.

The pouch-type battery cells <NUM> means a secondary battery including a pouch exterior and an electrode assembly provided to be accommodated in the pouch exterior. For example, the pouch exterior may include two pouches, and a concave inner space may be formed in at least one of the two pouches. In addition, the electrode assembly may be accommodated in the inner space of the pouch. Peripheries of the two pouches are welded to each other so that the inner space accommodating the electrode assembly may be sealed. An electrode lead <NUM> may be attached to the electrode assembly, and the electrode lead <NUM> may be interposed between the welded portions of the pouch exterior and exposed out of the pouch exterior to function as an electrode terminal of the battery cell.

Although not shown in detail for convenience of illustration, electrode leads <NUM> of the battery cells <NUM> may be welded to bus bars (not shown) provided on an ICB board (not shown) so that the battery cells <NUM> are connected in series and/or in parallel. The ICB board and the bus bars may be shielded with module covers <NUM>, <NUM>.

The module housing <NUM> has an inner space for accommodating the cell stack <NUM> and serves to provide a mechanical support to the stored battery cells <NUM> and protect the battery cells <NUM> from external shocks. Thus, the module housing <NUM> may be preferably made of a metal material to ensure rigidity. Here, the scope of the present disclosure is not limited to the module housing <NUM> made of metal.

As shown in <FIG>, the module housing <NUM> according to an embodiment of the present disclosure includes four plates, including a top plate <NUM>, a bottom plate <NUM>, a left side plate <NUM>, <NUM> and a right side plate <NUM>, <NUM>.

The top plate <NUM> is disposed at an upper portion of the cell stack <NUM>, and the bottom plate <NUM> is disposed at a lower portion of the cell stack <NUM>. In addition, the pair of side plates <NUM>, <NUM> are disposed at left and right sides of the cell stack <NUM> in the longitudinal direction, respectively. The four plates are assembled together to form the module housing <NUM> of a rectangular tubular shape. For example, the four plates may be assembled together by snap-fitting or welding.

In particular, the module housing <NUM> of this embodiment has an assembled structure capable of withstanding the force applied outward from the inside of the module housing <NUM>, in consideration of swelling of the battery cells <NUM>.

For this purpose, the top plate <NUM> and the bottom plate <NUM> have bent portions 21a, 22a respectively provided by bending both longitudinal corner regions thereof, and the pair of side plates <NUM>, <NUM> have a stepped portion 23a at which both longitudinal corner regions are stepped (see <FIG>).

The stepped portion 23a of the side plates <NUM>, <NUM> is shape-matched with an inner side of the bent portions 21a, 22a of the top plate <NUM> and the bottom plate <NUM>. In this case, when a force is applied outward from the inside of the module housing <NUM>, the top plate <NUM> and the bottom plate <NUM> may hold the side plates <NUM>, <NUM> to reduce the deformation of the side plates <NUM>, <NUM>.

In order to reduce the swelling of the battery cells <NUM> in the module housing <NUM>, as shown in <FIG>, the cell pressing plate <NUM> and the buffering member <NUM> are further disposed between the side plates <NUM>, <NUM> and the outermost battery cell <NUM>.

In other words, the cell pressing plate <NUM> is disposed to face the entire area of both longitudinal side surfaces of the cell stack <NUM>, and the buffering member <NUM> is interposed between the cell pressing plate <NUM> and the side plates <NUM>, <NUM>.

The cell pressing plate <NUM> may be bonded to the outermost battery cell <NUM> in order to secure a force for close adhesion to the cell stack <NUM>. In addition, a leaf spring <NUM> is employed as the buffering member <NUM>. The leaf spring <NUM> has at least one curve repeatedly formed in the vertical direction and is disposed such that one surface thereof is in contact with the cell pressing plate <NUM> and the other surface thereof is in contact with the side plates <NUM>, <NUM>. As an alternative to the leaf spring <NUM>, a compression foam or a rubber pad may also be employed.

In this embodiment, the cell pressing plate <NUM> and the buffering member <NUM> are provided in a pair, and two pairs of cell pressing plates <NUM> and buffering members <NUM> are respectively disposed at both side surfaces of the cell stack <NUM> to enhance a buffering capacity when the battery cells <NUM> swell. However, it is also possible that the cell pressing plate <NUM> and the buffering member <NUM> are disposed only at one side surface of the cell stack <NUM> to secure a space for additional battery cells <NUM> in the module housing <NUM> in order to increase the energy density.

According to this configuration, the cell stack <NUM> in the module housing <NUM> may be restrained in an elastically compressed state by the leaf spring <NUM> and the cell pressing plate <NUM>. In this case, the compressing force of the cell pressing plate <NUM> and the expanding force of the battery cells <NUM> may be offset, thereby reducing the swelling of the battery cells <NUM> during charging and discharging.

If the expanding force of the battery cells <NUM> is stronger than the compressing force of the cell pressing plate <NUM>, the leaf spring <NUM> of <FIG> deforms like the leaf spring <NUM> of <FIG>. That is, the leaf spring <NUM> is elongated in the vertical direction as its curve or wrinkle pattern spreads. Since the leaf spring <NUM> is deformed as above to absorb a part of the expanding force of the battery cells <NUM>, the external appearance of the module housing <NUM> may be less deformed. For reference, if even the module housing <NUM> is expanded, a pressure is applied not only to the corresponding battery module <NUM> but also to other battery module <NUM> or an electronic device adjacent to the corresponding battery module <NUM>, which is not good for safety.

Meanwhile, the battery module <NUM> of the present disclosure further includes a swelling gauge <NUM> so that the degree of swelling of the battery cell <NUM> may be easily understood. As will be explained in detail later, the swelling gauge <NUM> is provided to be checked from the outside of the battery module <NUM> so that anyone may intuitively figure out a swelling amount of the battery cells <NUM>. Thus, a user looking at the swelling gauge <NUM> may stop using the battery module <NUM> or replace the battery module <NUM> in advance by measuring the life of the battery module <NUM>.

Hereinafter, the structure and application of the swelling gauge <NUM> will be described in detail with reference to <FIG>.

The swelling gauge <NUM> may be integrally formed with the cell pressing plate <NUM> to protrude from the surface of the cell pressing plate <NUM>. For example, the swelling gauge <NUM> may have any shape whose length is measurable, such as a circular column shape, a polygonal column shape, or a steel ruler shape. In addition, the swelling gauge <NUM> and the cell pressing plate <NUM> may be manufactured separately, and then the swelling gauge <NUM> may be coupled to the cell pressing plate <NUM> by screwing or the like.

The side plates <NUM>, <NUM> further have a gauge hole H1 through which the swelling gauge <NUM> passes. Thus, as shown in <FIG>, when the battery cells <NUM> swell, the swelling gauge <NUM> may be pushed out of the module housing <NUM> through the gauge holes H1 formed in the side plates <NUM>, <NUM>.

At this time, the swelling amount of the battery cells <NUM> may be figured out by measuring the length of a front end of the swelling gauge <NUM> protruding out of the module housing <NUM> based on the gauge hole H1. A scale <NUM> is displayed on the swelling gauge <NUM> so that the information about the swelling amount may be figured out more easily.

In particular, the swelling gauge <NUM> of this embodiment is located at the center of the cell pressing plate <NUM>. This location is selected in consideration of the fact that the center of the battery cell <NUM> becomes most convex when being inflated. In other words, the center of the cell pressing plate <NUM> is most affected by the expansion of the battery cells <NUM>, so that the swelling amount of the battery cells <NUM> may be measured most accurately by disposing the swelling gauge <NUM> at the center of the cell pressing plate <NUM>.

Meanwhile, the leaf spring <NUM> also has a leaf hole H2 at the center thereof such that the swelling gauge <NUM> passes therethrough. By doing so, when the battery cells <NUM> swell, it is possible to avoid the collision of the swelling gauge <NUM> and the leaf spring <NUM>. Moreover, the leaf spring <NUM> may be suspended from the swelling gauge <NUM> so that the centers of the cell pressing plate <NUM> and the leaf spring <NUM> may be conveniently disposed to contact each other.

More specifically, in order to avoid the collision between the swelling gauge <NUM> and the leaf spring <NUM>, for example, it is also possible that two or more leaf springs <NUM> are disposed to be separated from each other at left and right sides of the swelling gauge <NUM>. However, it is most effective to use one leaf spring <NUM> and one leaf hole H2 for the following reasons.

The leaf spring <NUM> is provided to be smaller than the width (in the Z-axis direction) of the cell pressing plate <NUM> and the side plates <NUM>, <NUM> in consideration of deformation when the battery cell <NUM> swell. For this reason, in order to match the centers of the leaf spring <NUM> and the cell pressing plate <NUM>, the leaf spring <NUM> should be spaced apart from the bottom plate <NUM> by a predetermined height. However, this problem may solved simply by perforating the leaf hole in the leaf spring <NUM> and then disposing the leaf spring <NUM> to be suspended from the swelling gauge <NUM> as in this embodiment. In addition, using one large leaf spring <NUM> is more effective since the expanding force of battery cells <NUM> may be absorbed evenly and the leaf spring <NUM> may be installed more easily.

Next, it will be briefly described how to use the swelling gauge <NUM>.

First, whether the battery cells <NUM> inside the battery module <NUM> are in a swelling state may be simply figured out by seeing whether the front end of the swelling gauge <NUM> protrudes from the side plates <NUM>, <NUM> of the module housing <NUM>.

Further, if it is required to know the swelling amount of the battery cells <NUM> more accurately, the accurate swelling amount may be checked from the scale of the swelling gauge <NUM>. That is, the length of the front end of the swelling gauge <NUM> protruding out of the gauge hole H1 of the side plates <NUM>, <NUM> means the swelling amount of the battery cells <NUM>. For example, if a specific point on the scale of the swelling gauge <NUM> is marked in red, when the specific point is outside the gauge hole H1, it may be determined as a dangerous situation and the user may take necessary measures in advance.

<FIG> is an exploded perspective view showing the cell pressing plate <NUM>, the buffering member <NUM> and the side plate <NUM> according to another embodiment of the present disclosure.

Next, the installation structure of swelling gauges 50a, 50b and 50c of the battery module <NUM> according to another embodiment of the present disclosure will be described with reference to <FIG>. The same reference sign as in the former embodiment represents the same component, and the same component will be described in detail again. The following description will be focused on features different from the former embodiment.

Although one swelling gauge <NUM> is provided at the center of the cell pressing plate <NUM> in the former embodiment, in this embodiment, a plurality of swelling gauges 50a to 50c are provided. Namely, as shown in <FIG>, the swelling gauges 50a to 50c include a first swelling gauge 50a located at the center of the cell pressing plate <NUM>, and a second swelling gauge 50b and a third swelling gauge 50c provided at both longitudinal edge regions of the cell pressing plate <NUM>.

In addition, the side plate <NUM> has three gauge holes H1a to H1c and the leaf spring <NUM> has three leaf holes H2a to H2c, corresponding to the three swelling gauges 50a to 50c.

In the former embodiment, the swelling amount may be measured only at the center of the cell pressing plate <NUM> where the battery cells <NUM> swell most severely. However, in this embodiment, the swelling amount may be further measured at both edge regions of the battery cells <NUM>. In addition, it may be possible to determine how much the battery cells <NUM> swell in each region.

Also, the leaf spring <NUM> may be held to the cell pressing plate <NUM> more securely. Since the leaf spring <NUM> may be suspended from three swelling gauges 50a to 50c, it is possible to prevent the leaf spring <NUM> from rotating left or right relative to the first swelling gauge 50a at the center.

As described above, since the battery module <NUM> according to an embodiment of the present disclosure includes the swelling gauge <NUM>, anyone may easily check the swelling state of the battery cells <NUM> and take necessary measures. This may be a great help for the safe use of the battery module <NUM>.

Meanwhile, a battery pack (not shown) according to an embodiment of the present disclosure includes at least one battery module <NUM> as described above. In addition to the battery module <NUM>, the battery pack may further include a case (not shown) for accommodating the battery module <NUM> and various devices (not shown) for controlling the charging and discharging of the battery module <NUM> such as a battery management system (BMS), a current sensor and a fuse.

The battery module <NUM> or the battery pack may also be applied to a vehicle such as an electric vehicle and a hybrid electric vehicle, an energy storage system (ESS), or other electric devices using a secondary battery as an energy source.

Claim 1:
A battery module (<NUM>), which allows a swelling amount of battery cells (<NUM>) accommodated in a module housing (<NUM>) to be intuitionally checked, the battery module (<NUM>) comprising:
a cell pressing plate (<NUM>) accommodated in the module housing (<NUM>) and disposed on at least one of both longitudinal side surfaces of a cell stack (<NUM>) that is formed by stacking the battery cells (<NUM>);
characterized by
a swelling gauge (<NUM>) provided to protrude from a surface of the cell pressing plate (<NUM>), and
a gauge hole (H1) formed in the module housing (<NUM>),
wherein a front end of the swelling gauge (<NUM>) is pushed out of the module housing (<NUM>) through the gauge hole (H1) by the swelling pressure of the battery cells (<NUM>),
wherein the swelling gauge (<NUM>) is provided with a scale (<NUM>) arranged on a surface thereof and extending in the pushing direction of the swelling gauge (<NUM>).