Patent Description:
In the recent years, vehicles for transportation of goods and peoples have been developed using electric power as a source for motion. Such an electric vehicle is an automobile that is propelled by an electric motor, using energy stored in rechargeable batteries. An electric vehicle may be solely powered by batteries or may be a form of hybrid vehicle powered by for example a gasoline generator. Furthermore, the vehicle may include a combination of electric motor and conventional combustion engine. In general, an electric-vehicle battery (EVB) or traction battery is a battery used to power the propulsion of battery electric vehicles (BEVs). Electric-vehicle batteries differ from starting, lighting, and ignition batteries because they are designed to give power over sustained periods of time. A rechargeable or secondary battery differs from a primary battery in that it can be repeatedly charged and discharged, while the latter provides only an irreversible conversion of chemical to electrical energy. Low-capacity rechargeable batteries are used as power supply for small electronic devices, such as cellular phones, notebook computers and camcorders, while high-capacity rechargeable batteries are used as the power supply for hybrid vehicles and the like.

Rechargeable batteries may be used as a battery module formed of a plurality of unit battery cells coupled in series and/or in parallel so as to provide a high energy density, in particular for motor driving of a hybrid vehicle. That is, the battery module is formed by interconnecting the electrode terminals of the plurality of unit battery cells depending on a required amount of power and in order to realize a high-power rechargeable battery. In particular, rectangular battery cells are usually provided as a compact battery stack within a shared battery module housing. Said battery stack may include a pair of rigid end plates and, for example, a number of cooling plates placed between neighbouring battery cells.

Battery cells can swell during regular operation for example as a result of temperature changes. In case of swelling, the swelling-force may be transmitted and cumulated along the battery stack towards the pair of end plates. As a consequence, the end plates are usually reinforced to withstand mechanical stress and reduce the bending of the end plates. However, there may be still a significant mechanical stress on the battery cells being arranged at both ends of the battery stack next to the end plates. Thereby, the cell aging may be increased. In order to reduce the mechanical stress caused by swelling spacers may be arranged between the battery cells so as to at least partially compensate the swelling force.

For example, <CIT> relates to a battery module including a plurality of prismatic battery cells and cell barriers disposed there between. Specifically, cell barrier of different strength are placed between the battery cells so as to avoid distortion of the module due to swelling. The barrier may have a cooling channel passing there through.

<CIT> refers to a secondary battery module including an alternating arrangement of prismatic battery cells and spacers. Each spacer includes a base portion contacting the side surface of a rectangular battery cell, a wing portion projecting from the base portion toward an adjacent battery spacer and enclosing at least a portion of a small side surface of the battery cell, and a fastening portion on the wing portion. The fastening portion is designed for coupling the spacer to an adjacent spacer. The base portion can be designed as a circumferential frame. The battery cell may expand into the free space enclosed by the frame during swelling.

<CIT> discloses another battery module including an alternating arrangement of prismatic battery cells and spacers. The spacers shall be designed to correspond to a region of maximum swelling of the battery cell case. The spacers may be suspended from a peripheral edge of the battery cell case.

<CIT> discloses another battery pack includes a plurality of prismatic secondary batteries with spacers each interposed therebetween, wherein the spacer has an upper recess and a lower recess on each surface.

<CIT> discloses a support assembly for a battery array includes a spacer axially separating a first battery cell from a second battery cell, a frame that holds the spacer, and an insert secured to the frame.

<CIT> discloses another battery assembly including battery cells and spacers that are alternately arranged.

<CIT> discloses a barrier including side panels and supporting protrusions but lacks elements to avoid structural stress.

Embodiments of the present disclosure refer to a spacer for arrangement between two prismatic battery cells of a battery stack. The spacer comprises:.

In other words, an alternative spacer for a battery stack composed of a plurality of prismatic (secondary) battery cells is provided. The spacer will be arranged between neighboring battery cells of the stack. An aim of the spacer is to establish a space between the battery cells which allows compensating swelling, specifically swelling of the central parts of the battery cells. Thereby, the mechanical stress caused by swelling on the outermost battery cells and end plates of the battery stack may be reduced and the lifetime of the battery stack may be increased. The mechanical stress may be distributed more evenly over all battery cells of the battery stack. Furthermore, the pair of positioning elements facilitates the assembling process of the battery stack. The spacer is simply attached to one side of the battery cell with the help of the positioning elements, which facilitates automatization of the manufacturing process. As both positioning elements run over the corner, the position of the spacer in horizontal and vertical direction in the stack is predetermined.

According to one embodiment, a thickness of the frame body is in the range of <NUM> to <NUM>. If the thickness of the frame body is less than <NUM>, the spacer may not have improper mechanical stability and the space provided within the frame body may be too small for compensating swelling of the battery cells. If the thickness of the frame body is more than <NUM>, the weight and dimension of the battery stack is enlarged without need since currently conventional secondary battery cells do not extend over <NUM> under normal operating conditions.

The frame body and the positioning elements may be integrally formed. Thereby, the manufacturing process of the spacer may be simplified and the mechanical stability of the spacer may be increased.

Further, the spacer comprises a distance element being arranged on the first longitudinal side and rising perpendicularly from the plane of the frame body in a direction opposite to the positioning elements. The distance element has a length in the range of <NUM> to <NUM>. In other words, the distance element is positioned on a surface side of the first longitudinal side of the frame body, which is opposite to the side surface from which the positioning elements protrude. This creates a thin gap between the adjacent batteries cells which allows air circulation for cooling of the battery stack.

The distance element may be arranged at an outer edge of the first longitudinal side. For example, the spacer element can be a <NUM>° folded fold which continuously extends between the two positioning elements. Further, the frame body and the distance element may be integrally formed, in particular together with the above mentioned positioning element. This may simplify the manufacturing process of the spacer and enhance mechanical stability thereof.

According to a further embodiment, the frame body, the positioning elements and/or the distance element are made of plastics. Preferably all the mentioned elements of the spacer are made of the same plastics. The plastics may have rigid or elastomeric characteristics.

Furthermore, an adhesive layer may be provided on a side surface of the frame body facing in the same direction as the positioning elements, in particular on a side surface of a second longitudinal side of the frame body. During the the assembling process of the battery stack, the adhesive layer will contact the side surface of the battery cell, where the spacer is placed on with its positioning elements. The adhesive layer thus allows to permanently fixing the desired position of the spacer within the battery stack.

According to another aspect of the present disclosure, a battery module for a vehicle is provided. The battery module comprises a battery stack including an alternating arrangement of battery cells and the spacers as described above.

Features of the inventive concept and methods of accomplishing the same may be understood more readily by reference to the following detailed description of an embodiment and the accompanying drawings. The present invention, however, may be embodied in various different forms, and should not be construed as being limited to only the illustrated embodiment herein. Rather, this embodiment is provided as example so that this disclosure will be thorough and complete, and will fully convey the aspects and features of the present invention to those skilled in the art.

<FIG> illustrates an exploded view on a part of a battery module <NUM> including a battery stack <NUM> according to an exemplary embodiment. The battery stack <NUM> will be accompanied in a housing of the battery module <NUM>. For simplification, the drawing shows only a base plate <NUM> and a side pad <NUM> of said housing. The battery stack <NUM> will be placed on the base plate <NUM>.

The battery stack <NUM> includes a plurality of battery cells <NUM> aligned in one direction. A pair of end plates <NUM> locks the battery stack <NUM>. Here, each battery cell <NUM> is a prismatic (or rectangular) cell, the wide flat surfaces of the cells being stacked together to form the battery stack <NUM>. Each battery cell <NUM> includes a battery case <NUM> configured for accommodation of an electrode assembly and an electrolyte. The battery case <NUM> is hermetically sealed by a cap assembly <NUM>. The cap assembly <NUM> is provided with positive and negative electrode terminals <NUM> and <NUM> having different polarities, and a vent <NUM>. The vent <NUM> is a safety means of the battery cell <NUM>, which acts as a passage through which gas generated in the battery cell <NUM> is exhausted to the outside of the battery cell <NUM>. A side surface of the battery case <NUM> may be covered with an insulation foil <NUM>. The positive and negative electrode terminals <NUM> and <NUM> of neighboring battery cells <NUM> are electrically connected through a bus bar (not shown). Hence, the battery module <NUM> may be used as power source unit by electrically connecting the plurality of battery cells <NUM> as one bundle.

The battery stack <NUM> further includes a plurality of spacers <NUM>. The spacers <NUM> and battery cells <NUM> are arranged alternately in the battery stack <NUM>. <FIG> is an enlarged illustration of one of the spacers <NUM> used in assembling the battery stack <NUM> of <FIG>.

The exemplary spacer <NUM> has a rectangular shape and includes a frame body <NUM>. The frame body <NUM> encloses an opening <NUM>, the purpose of which will be explained in more detail below. The frame body <NUM> contains a first longitudinal side <NUM>, which is located in the battery stack <NUM> at the height of the cap assembly <NUM>. A second longitudinal side <NUM> of the frame body <NUM> faces the base plate <NUM> of the housing. The second longitudinal side <NUM> of the exemplary spacer <NUM> is slightly offset inwards such that a small gap <NUM> is provided at the bottom of the spacer <NUM>. Two transverse sides <NUM> and <NUM> connect the two longitudinal sides <NUM> and <NUM> of the frame body <NUM>. A thickness of the frame body <NUM> - i.e. each of the longitudinal <NUM> and <NUM> and transverse sides <NUM> and <NUM> - may be about <NUM>.

The spacer <NUM> further includes a pair of positioning elements <NUM> which rise perpendicularly from a plane of the frame body <NUM> to one side of the frame body <NUM> and extend over the two corners of the common first longitudinal side <NUM>. Here, the positioning elements <NUM> have an L-shape and extend about <NUM> from the plane of the frame body <NUM>. As shown in <FIG>, the positioning elements <NUM> are positioned horizontally on the cap assembly <NUM> and vertically on the two transverse sides of the battery case <NUM> within the finalized battery stack <NUM>. Thus, the spacer <NUM> can be easily stacked onto a battery cell <NUM> during the assembling process of the battery stack <NUM>, which allows rapid automatization of the process step.

Further, an adhesive layer <NUM> is provided on the same side surface of the frame body <NUM> from which the positioning elements <NUM> extend. Here, the adhesive layer <NUM> is provided on a side surface of a second longitudinal side <NUM>. After the spacer <NUM> has been placed on the side of the battery cell <NUM>, the adhesive layer <NUM> adheres to the side surface of the battery case <NUM>.

The spacer <NUM> further comprises a distance element <NUM> being arranged on the first longitudinal side <NUM> and rising perpendicularly from the plane of the frame body <NUM> in a direction opposite to the positioning elements <NUM>. For example, the distance element <NUM> may have a length of about <NUM>. According to the exemplary embodiment, the distance element <NUM> is arranged at an outer edge of the first longitudinal side <NUM>. The exemplary distance element <NUM> has the shape of a bended fold. The distance element <NUM> is used to define a gap on the side of the spacer <NUM> opposite to the side of the spacer <NUM> where the adhesive layer <NUM> and the positioning elements <NUM> are provided. In other words, the distance element <NUM> provides a small creepage distance between neighbouring battery cells <NUM>. Generally, the battery cells <NUM> generate a large amount of heat while being charged/discharged. The generated heat is accumulated in the battery cells <NUM>, thereby accelerating the deterioration of the battery cells <NUM>. Therefore, the battery module <NUM> needs to be cooled. The gap defined on one side of the spacer <NUM> will thus allow to, for example, circulating air to cool the battery cells <NUM>.

In alternative or addition to the above mentioned embodiment, a thermal conducting material may be provided at a bottom side of the battery cells <NUM>, respectively on the base plate <NUM> of the housing. The thermal conducting material is to enhance a thermal contact between a cooling system provided in a lower part of the battery module <NUM> and the single battery cells <NUM>. According to one embodiment, the main components of the battery stack <NUM> - in particular the batteries cells <NUM>, spacers <NUM>, and end plates <NUM> - will be assembled along with applying a compression force. Therefore, the longitudinal side <NUM> of the exemplary spacer <NUM> may be slightly offset inwards such that a small gap <NUM> is provided at the bottom of the spacer <NUM>. The free ends <NUM> and <NUM> at the lower transverse sides <NUM> and <NUM> will transmit the force applied to the edges of the stiff battery cells <NUM> into the thermal conducting material so as to avoid damage of the battery case <NUM> due to mechanical stress. Furthermore, the thermal conducting material may spread into the gap <NUM> at the bottom side of the spacer <NUM> and may thereby increase a contact surface to the battery case <NUM> of the battery cells <NUM>. The thermal conductive material may be provided as a foil, layer or mat composed, for example, of a plastic material including metallic particles.

During regular operation the battery cells <NUM> may expand slightly. The amount of swelling will be at largest in a central area of the side surfaces of the battery cells <NUM>. Therefore, the opening <NUM> of the spacer <NUM> will allow expansion of the battery cells <NUM>. This avoids accumulation of mechanical stresses at the two ends of the battery stack <NUM>.

Claim 1:
A spacer (<NUM>) for arrangement between two prismatic battery cells (<NUM>) of a battery stack (<NUM>), the spacer (<NUM>) comprising:
a rectangular frame body (<NUM>) enclosing an opening (<NUM>) and
a pair of positioning elements (<NUM>) which rise perpendicularly from a plane of the frame body (<NUM>) to one side of the frame body (<NUM>) and extend over the two corners of a common first longitudinal side (<NUM>) and wherein the spacer (<NUM>) further comprises a distance element (<NUM>) being arranged on the first longitudinal side (<NUM>) and rising perpendicularly from the plane of the frame body (<NUM>) in a direction opposite to the positioning elements (<NUM>), the distance element (<NUM>) having a length in the range of <NUM> to <NUM>.