WO2024008669A1

WO2024008669A1 - Potted battery module and a method for assembling the same

Info

Publication number: WO2024008669A1
Application number: PCT/EP2023/068282
Authority: WO
Inventors: Rodyn GILHARRY; Florian HARTMAN
Original assignee: Northvolt Ab
Priority date: 2022-07-08
Filing date: 2023-07-04
Publication date: 2024-01-11
Also published as: EP4552176A1; SE2250873A1; SE546303C2

Abstract

A potted battery module is disclosed. The potted battery module comprising a plurality of secondary cells and a cellular support structure comprising a plurality of compartments, wherein each compartment is configured to receive at least one secondary cell of the plurality of secondary cells, as well as a thermally insulating material configured to form a thermal barrier between neighboring compartments. The module further comprises a thermally conductive potting medium arranged to at least partially surround the plurality of secondary cells to secure the secondary cells to the cellular support structure and to transfer heat from the secondary cells.

Description

Potted battery module and a method for assembling the same

Technical Field

The present disclosure relates to battery modules, and in particular to a potted battery module and method for assembly thereof.

Background

Rechargeable or secondary batteries (cells) find widespread use as electrical power supplies and energy storage systems. For example, in automobiles, battery modules may include a plurality of electrochemical cells, provided as a means of effective storage and utilization of electric power.

Potting is the process of embedding cells with a compound for the purpose of providing resistance to shock and vibration, as well as creating a seal against moisture, solvents, and corrosive agents. Potting compounds may also aid with electrical insulation, flame retardancy, and heat dissipation, as well as providing structural support, bonding the cells into place. Consequently, there are several requirements on the potting material, relating to, for example, mechanical and thermal stability, flame retardancy, heat dissipation, and dielectric strength enhancements.

Polyurethane or Epoxy-based material represent commonly used potting media, known to exhibit a relatively high resistance to thermal degradation. However, polyurethane is also known to be relatively soft compared to many other potting compounds and may therefore be less suitable for applications requiring high structural stability.

Summary

It is an object of the present disclosure to provide an improved potting technology for battery modules. It is also an object to provide potted battery modules enabling improved thermal management of the secondary cells.

Hence, according to a first aspect, a potted battery module is provided, comprising a plurality of secondary cells and a cellular support structure comprising a plurality of compartments, wherein each compartment is configured to receive at least one secondary cell of the plurality of secondary cells, as well as a thermally insulating material configured to form a thermal barrier between neighboring compartments. The module further comprises a thermally conductive potting medium arranged to at least partially surround the plurality of secondary cells to secure the secondary cells to the cellular support structure and to transfer heat from the secondary cells.

According to a second aspect, a method for assembling a potted battery module is provided. The method comprises inserting a plurality of secondary cells into a cellular support structure comprising a plurality of compartments, wherein each compartment is configured to receive at least one secondary cell of the plurality of secondary cells and adding a potting medium to each of the compartments to at least partially surround the plurality of secondary cells, such that the secondary cells are secured to the cellular support structure. It will be appreciated that the potting medium may be added to each compartment, for example, by pouring it into the compartments. It will further be appreciated that the potting medium may also be added to each compartment by pushing, or forcing, the cellular support structure onto the potting medium such that the potting medium enters each compartment. The potting medium is adapted to transfer heat from the secondary cells, and the cellular support structure comprises a thermally insulating material configured to form a thermal barrier between neighboring compartments.

The thermally conductive potting medium allows heat to be efficiently transported away from the secondary cells, whereas the thermally insulating cellular support structure may hinder the heat spreading from one secondary cell to another. Hence, thermally conductive properties may beneficially be combined with thermally insulating properties to improve the thermal management of the secondary cells. By arranging the secondary cells in the compartments formed by the cellular support structure, a major part of the heat generated by a secondary cell may be transported toward the top or bottom of the compartment, rather than laterally to adjacent compartments. The presence of a thermal barrier between the compartments may hence assist in directing the heat flow in a desired direction, i.e. , towards cooling structures arranged above or below the compartments, and thereby reduce the risk of local overheating, for example caused a by a thermal runaway event spreading within the module.

Thermal conductivity’ is understood as an intrinsic property of a material, relating to the material’s ability to conduct heat. Hence, as used herein, a ‘thermally conductive’ material may be understood as a material capable of transferring heat to or from the secondary cells embedded in the material. More specifically, a thermally conductive material may have a thermal conductivity preferably in the range of 0,1 to 2,5 W/mK, more preferably in the range of 0,3 to 2,2 W/mK and most preferably in the range of 0,5 to 2,0 W/mK.

Accordingly, a ‘thermally insulating’ material is understood as a material capable of reducing the heat transfer between two objects when arranged therebetween. Hence, as used herein, the thermally insulating material may be arranged to reduce the heat transfer between two compartments, and more particularly between the potting medium in such compartments. In some examples, a thermally insulating material may have a thermal conductivity below 0,2 W/mK.

The term ‘potting medium’ refers to a compound or medium at least partly wrapping a secondary cell and preferably filling a space between the secondary cell and the cellular support structure.

Thus, in some embodiments the potting medium may be provided in a layer extending from a top portion to a bottom portion of the secondary cell, thereby allowing the entire spacing between the secondary cell and the support structure to be filled with the potting medium. With this configuration, the thermal interface between the potting medium and the secondary cell may be increased or even maximized, allowing for an improved heat transfer from the secondary cell into the potting medium.

In some embodiments, the potting medium may be provided in a first layer arranged at a top portion of the secondary cells and, preferably, a second layer arranged at a bottom portion of the secondary cells. The two layers may be vertically separated from each other to specify a gap or spacing therebetween. As a result, there is at least a portion of the outer surface of the secondary cell which is not in physical contact with any of the potting medium layers. The first and second potting medium layers allow heat to be transferred from the secondary cells, while the separation of spacing between the layers makes it possible to reduce the amount of potting medium. Reducing the amount of potting medium may be beneficial in terms of cost and weight savings.

It will be appreciated that the potting layer in some examples may be arranged at the top portion only or at the bottom portion only.

As already mentioned, a cooling plate may be arranged at the top or bottom of the secondary cells. The cooling plate may be arranged in thermal contact with the potting medium to allow heat from the secondary cells to be transferred into the cooling plate. In different words, the cooling plate may provide a heatsink functionality reducing the risk of overheating of the secondary cells. It will further be appreciated that the cooling plate may be configured to increase the temperature of the secondary cells to reach an optimum operating temperature, for example when the battery module is subjected to cold conditions. In some examples, cooling plates may be arranged both at the top and the bottom of the secondary cells when potting medium is provided both at the top portion of secondary cells and at the bottom portion of the secondary cells. In other examples, the cooling plate may be arranged only at the top of the secondary cells when potting medium is provided only at the top portion of the secondary cells or arranged only at the bottom of the secondary cells when potting medium is provided only t the bottom portion of the secondary cells. The cooling plate may be a passive element, in which the material forming the element may be adapted to absorb and spread the heat, or an active cooling element comprising, for example, channels for guiding a flow of cooling medium.

In some embodiments, the compartments of the support structure may have a polygonal cross section. An example of such a cross section is the so- called honeycomb structure, comprising a plurality of polygonal compartments which, for instance, may be hexagonal. Beneficially, the cross section of a compartment may differ from a cross section of the secondary cell fitted in the compartment to allow spacings and gaps that can accommodate the potting medium. By for example arranging a cylindrical secondary cell in a polygonal compartment, such as a honeycomb structure, the non-overlapping areas of the respective cross sections define regions which can be filled with the potting medium. Further, in some examples a minimum cross-sectional width of a compartment may correspond to a maximum width of a secondary cell to allow the secondary cell to be supported between the walls of the compartment. Hence, by, for example, arranging a cylindrical secondary cell in a square compartment with side lengths corresponding to the diameter of the cylindrical secondary cell, the cylindrical secondary cell can be securely fitted between the compartment walls. It will be appreciated that a cellular support structure comprising compartments encompassing hexagonal cross sections may provide space efficiency in terms of the number of cylindrical secondary cells being received by the compartments of the cellular support structure. Further, hexagonal cross sections may minimize the potting medium needed to secure cylindrical secondary cells to the cellular support structure and to transfer heat from the secondary cells.

A further advantage of the honeycomb structure may be that it provides mechanical stability, provides mechanical support and rigidity to the battery module and increases its ability to withstand mechanical shock and high loads.

In some embodiments, the support structure comprises a flame- resistant material. A flame-resistant, or fireproof material may be understood as a material capable of preventing spreading of fire in the event of an accident or failure, such as a thermal runaway event of a secondary cell. By using a flame-resistant material, an even more efficient barrier between neighboring compartments may be achieved.

In some examples, the cellular support structure may be formed of an aramid material, such as meta-aramid, which is flame resistant. Further examples include insulated and/or coated aluminum, plastic, polypropylene, etc.

It will be appreciated that the presently described cellular support structure and potting medium may be applied to any shape of secondary cell, such as cylindrical or prismatic, and the module comprising such secondary cells may be a battery pack, a battery module with or without a frame. That is, the present approach may be readily applied to modular battery packs as well as so-called ‘structural batteries’, which may not only provide energy storage but also mechanical structure.

In any event, numerous advantages, some of which are described above, may be realized through the arrangement in which secondary cells are potted with a thermally conductive potting medium in a thermally insulating cellular support structure. These advantages, as well as others, may be further appreciated through a description of specific illustrated embodiments.

Brief Description of the Drawings

One or more embodiments will be described, by way of example only, and with reference to the following figures, in which:

Figure 1 schematically shows an isometric view of a cellular support structure, secondary cells and a cooling plate of a battery module according to embodiments of the present disclosure;

Figure 2 schematically shows a top view of a potted battery module according to embodiments of the present disclosure; and

Figure 3 schematically shows a cross-sectional view of a compartment of a cellular support structure according to embodiments of the present disclosure.

Detailed Description

The present disclosure is described in the following by way of a number of illustrative examples. It will be appreciated that these examples are provided for illustration and explanation only and are not intended to be limiting on the scope of the disclosure. Furthermore, although the examples may be presented in the form of individual embodiments, it will be recognized that the present disclosure also covers combinations of the embodiments described herein.

Figure 1 schematically shows an isometric view of a cellular support structure 110, secondary cells 10 and a cooling plate 132 of a battery module 100 according to embodiments of the present disclosure. The cellular support structure 110 is shown comprising a plurality of compartments 112 each configured to receive at least one secondary cell 10. The cellular support structure 110 is further illustrated having a polygonal cross section. In the illustrated embodiment, each compartment 112 of the cellular support structure 110 exhibits a hexagonal cross section, therefore forming a honeycomb structure. It will be appreciated that each compartment 112 may have alternative cross sections, conforming with different polygons.

Upon insertion of potting medium in the compartments 112, heat generated by the secondary cells 10 may be evacuated into the cooling plate 132 positioned at the bottom of the secondary cells 10 by means of the potting medium. It will be appreciated that the thermal insulating properties of the material of the cellular support structure 110 may prevent or limit the heat generated by the secondary cells 10 travelling to a neighboring compartment 112.

Figure 2 schematically shows a top view of a potted battery module 100 according to embodiments of the present disclosure. The battery module 100 is shown having a cellular support structure 110 comprising a plurality of compartments 112 each having a secondary cell 10 fitted therein. The compartments 112 are further shown comprising a polygonal cross section differing from the circular cross section of the secondary cells 10 fitted therein such that non-overlapping areas of the aforementioned cross sections define regions in which the potting medium 120 is inserted into each compartment 112. In the illustrated embodiment, the minimum cross sectional width of each compartment 112 corresponds to the maximum width of each secondary cell 10 fitted therein, thereby allowing each secondary cell 10 to be supported by the walls of their respective compartment 112. Furthermore, the potting medium 120 may enable thermal conductivity between the secondary cells 10 and one or more cooling plates (not shown), and the cellular support structure 110 may form a thermal barrier between the compartments 112. It will be appreciated that the potting material 120 may be configured to further immobilizing each secondary cell 10 within their respective compartments 112 and the cellular support structure 110 may be configured to provide structural stability to the plurality of compartments 112 and to the battery module 100 as a whole.

Figure 3 schematically shows a cross sectional view of a compartment 112 of a cellular support structure according to embodiments of the present disclosure. The illustrated embodiment depicts a secondary cell 10 fitted inside the compartment 12 and wherein the potted medium is provided in a first layer 121 arranged at a top portion of the secondary cell 10 and in a second layer 122 arranged at a bottom portion of the secondary cell 10. Figure 3 further illustrates the first layer 121 and the second layer 122 being vertically separated from one another by a space. In the illustrated embodiment, the first layer 121 may enable thermal conductivity between the secondary cell 10 and a cooling plate 131 positioned on the top of secondary cell 10 such that heat may be evacuated from the secondary cell 10 to the top cooling plate 131 via the first layer 121. Similarly, the second layer 122 may enable thermal conductivity between the secondary cell 10 and a cooling plate 132 positioned on the bottom of the secondary cell 10.

It will further be appreciated that the assembly of the potted compartment 112 illustrated in figure 3 may be obtained by first inserting the secondary cell 10 into the compartment 112, then adding potting material 120 so as to form the first layer 121 at the top portion of the secondary cell 10. After at least partial solidification of the first layer 121 , the second layer 122 of potting medium 120 is added at the bottom portion of the secondary cell 10. The cooling plates 131 , 132 may then be arranged on top and at the bottom of the secondary cell 10 respectively such that the potting medium 120 is in thermal contact with the cooling plates 131 , 132. It will be appreciated that, although the above aspects are presented separately, they may be combined in any suitable manner such that a battery pack may benefit from all of the advantages provided by respective aspects of the present disclosure. Furthermore, whilst the forgoing description and the appended drawings are provided as exemplary or preferred realizations of the disclosed aspects, it will be appreciated that the disclosed aspects need not be limited to the exact form shown and/or described.

Claims

1 . A potted battery module (100), comprising: a plurality of secondary cells; a cellular support structure (110) comprising a plurality of compartments (112), wherein each compartment is configured to receive at least one secondary cell of the plurality of secondary cells (10); and a thermally conductive potting medium (120) arranged to at least partially embed the plurality of secondary cells to secure the secondary cells to the cellular support structure and to transfer heat from the secondary cells; wherein the cellular support structure comprises a thermally insulating material configured to form a thermal barrier between neighboring compartments.

2. The battery module according to claim 1 , wherein the potting medium is provided in a layer extending from a top portion to a bottom portion of the secondary cell.

3. The battery module according to claim 1 , wherein the potting medium is provided in a first layer (121) arranged at a top portion of the secondary cells and a second layer (122) arranged at a bottom portion of the secondary cells, and wherein the first and second layers are vertically separated from each other.

4. The battery module according to claim 1 , wherein the potting medium is provided in a first layer (121) arranged at a top portion of the secondary cells or in a second layer (122) arranged at a bottom portion of the secondary cells.

5. The battery module according to any of the preceding claims, further comprising a cooling plate (131 , 132) arranged at the top or bottom of the secondary cells, wherein the potting medium is arranged in thermal contact with the cooling plate.

6. The battery module according to any of the preceding claims, wherein a cross section of each compartment conforms to a polygon.

7. The battery module according to any of the preceding claims, wherein the cellular support structure forms a honeycomb structure.

8. The battery module according to any of the preceding claims, wherein the cellular support structure comprises a flame resistant material.

9. The battery module according to any of the preceding claims, wherein the cellular support structure is formed of a material selected from the list consisting of: aramid material, insulated and/or coated aluminum, plastic, polypropylene.

10. A method for assembling a potted battery module (100), comprising: inserting a plurality of secondary cells (10) into a cellular support structure (110) comprising a plurality of compartments (112), wherein each compartment is configured to receive at least one secondary cell of the plurality of secondary cells; and adding a potting medium (120) to each of the compartments to at least partially surround the plurality of secondary cells, such that the secondary cells are secured to the cellular support structure; wherein the potting medium is adapted to transfer heat from the secondary cells; and wherein the cellular support structure comprises a thermally insulating material configured to form a thermal barrier between neighboring compartments.

11 . The method according to claim 10, wherein adding the potting medium comprises: forming a first layer (121 ) of the potting medium at a top portion of the secondary cells; and forming a second layer (122) of the potting medium at a bottom portion of the secondary cells.

12. The method according to claim 10 or 11 , further comprising: arranging a cooling plate (131 , 132) at a top or bottom of the secondary cells, such that the potting medium is in thermal contact with the cooling plate.