Battery pack for electric road vehicle and electric road vehicle provided with same

Abstract

The invention relates to a battery pack of an electric road vehicle and an electric road vehicle with the battery pack. The battery pack comprises: a plurality of planar electrochemical cells arranged in groups along an axis; and a support structure comprising two plates opposite along the axis and parallel to the battery cell, wherein the two plates define a housing volume of the battery cell; wherein the battery cells are housed in the support structure at the beginning of the service life, with an initial preload along the axis that produces a corresponding initial axial stress acting on the plate; wherein each battery cell comprises two flat faces orthogonal to the axis and a thickness along the axis that gradually increases during the useful life of the battery pack; wherein the plates are configured to move away from each other along the axis such that an increase in battery cell thickness does not result in a corresponding gradual increase in axial stress acting on the plates.

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to Italian Patent Application No. 102024000017437, filed on July 26, 2024, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The technical field of this invention relates to the field of road vehicles with electric propulsion. This indication includes road vehicles with only electric propulsion and road vehicles with both electric and heat-absorbing propulsion. More specifically, the invention relates to a battery pack, namely a battery pack formed by multiple planar battery cells grouped together along axis A and housed in a specific housing structure. As is known, there are two mechanical characteristics that designers must consider when creating this type of battery pack. The first mechanical characteristic consists of the fact that axial preload is necessary for the proper operation of the battery cells. The second mechanical characteristic is that at the end of their service life, the battery cells comprising the battery pack have a greater thickness along axis A than at the beginning of their service life, and this gradual increase in thickness causes a corresponding increase in the mechanical stress transmitted from the battery cells to the frame housing them. In this context, the invention addresses how to ensure optimal preload throughout the service life and how to limit (i.e., reduce relative to the prior art) the stress transmitted from the battery cells to the frame housing them during the service life of the battery pack. In fact, lower stress acting on the structure allows the housing frame of the battery cells to not be too large, thereby reducing the weight of the battery pack, which is a factor that brings significant benefits in terms of overall vehicle performance. Finally, the invention also relates to a road vehicle comprising the aforementioned battery pack. Background Technology

[0004] In the automotive field, particularly regarding electric road vehicles, lithium-ion batteries are known to be used to store the electrical energy to be delivered during electric propulsion. Indeed, these lithium-ion batteries offer the high energy density ideal for implementing electric power in the automotive sector. Currently, lithium polymers are, in fact, the latest technology for manufacturing high-capacity batteries from a chemical perspective. In these batteries, various series and parallel interconnections of battery cells are envisioned to achieve the desired total voltage and total energy density of the battery pack. Commercially available battery modules (not only in the automotive market but also in consumer electronics) typically include planar pouch cells, which have a more limited thickness compared to other sizes. Two very wide, opposing faces orthogonal to the direction or axis of the battery pack are identified, along with four thin edges, where the positive and negative terminals of the battery cells are arranged on one side or opposite sides. The battery pack includes a support structure that houses a group of multiple electrochemical battery cells with an initial preload. Electrical connectors are also provided in a known manner to connect the battery pack to the vehicle's propulsion system and control unit (often referred to as the BMS – "Battery Management System").

[0005] Therefore, in summary, the battery pack comprises a plurality of planar electrochemical cell units arranged in a group along axis A and a rigid structure housing the cell units. Specifically, the rigid support structure comprises two plates parallel to the cell units and on opposite sides of the battery pack. The distance between these plates thus defines the housing volume of the cell units along axis A. As described above, the cell units are housed in the support structure along axis A in a preload configuration. Therefore, the plates are sized to support the initial stress. Furthermore, as described above, each cell unit comprises two flat surfaces orthogonal to axis A and a thickness along axis A that gradually increases from a minimum initial lifespan value to a maximum or end-lifespan thickness. To allow and compensate for the increase in thickness, the cell units are separated from each other along axis A, and between each pair of adjacent cell units, an intermediate or planar separator (referred to as a “foam”) is known to be provided in contact with the flat surfaces of the cell units. The intermediate planar separator is configured (i.e., it is made of a suitable material) to be compressed during the gradual increase in cell thickness. Therefore, as the thickness of the battery cell increases, the stress along axis A is partially absorbed by the foam separator and partially discharged onto the support plate. Thus, the support plate must be configured to support not only the initial stress state but also the gradual increase of this stress.

[0006] Next-generation lithium-ion batteries are currently available, but they still require constant and very high compression across the entire surface of the battery cell. Because the axial stress released onto the plate is therefore very high initially, a solution is needed that can reduce (or keep constant) the increase in stress transmitted from the battery cells to the frame housing them throughout the battery pack's lifespan. Limiting stress allows the dimensions of the battery cell housing frame to be designed to be "lighter," thus reducing the weight of the battery pack. This weight reduction leads to significant benefits in overall vehicle performance. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide a battery pack for an electric road vehicle that overcomes the aforementioned disadvantages. In addition to the battery pack itself as described in claim 1, the present invention also extends to electric road vehicles equipped with such a battery pack.

[0008] If the invention is to be defined more generally, it begins with a battery pack comprising a plurality of electrochemical battery cells (preferably utilizing lithium-ion technology), wherein the battery cells are planar and arranged side-by-side with each other along a direction or axis A. The battery pack includes (as is known) a housing structure that acts as a rigid support accommodating the battery cells grouped together along axis A. At opposite ends along axis A, the support structure includes two retaining plates. Each battery cell includes (as is known) two flat surfaces orthogonal to axis A and a thickness along axis A that gradually increases from a minimum initial lifespan value during the lifespan of the battery pack until a maximum or end-of-life thickness. As is known, the battery cells are housed between plates that are already in a pre-compressed state at the beginning of their lifespan, transferring corresponding stresses to the (rigid) plates. Starting with this known structure, according to the invention, throughout the lifespan of the battery pack, the plates are not always fixed at the same distance from each other, but are instead configured to move away from each other along axis A to "support" the increase in the thickness of the battery cells, thereby preventing such an increase in thickness from causing a corresponding increase in axial stress on the plates. In this way, the initial compression of the battery cells according to the design is guaranteed, and excessive load on the plate due to the increase in battery cell thickness is avoided.

[0009] This distance between the plates can be implemented in many different ways, all of which fall within the overall idea of ​​the invention as described above.

[0010] According to a first example, a manually operable device is provided to move the plates gradually away from each other along axis A. Thus, according to this example, adjustment of the battery pack (distance between the plates) is performed during technical assistance service or during planned maintenance procedures. An embodiment of this manual adjustment device is shown in the accompanying drawings, and provides multiple rope elements wound around the battery pack and configured to hold the plates in a fixed position. In such an example, the manually operable device for moving the plates away from each other along axis A includes an irreversible screw-nut coupling configured to unwind the rope elements sufficiently to allow the plates to move away correspondingly under the thrust of the expanding battery cells. The watertightness of the batteries is always ensured by specific washers sealing the adjusting pins of the screw-nut coupling. The battery pack is further designed to ensure adjustment repositioning, thus allowing space for the restoration of adjustment movement.

[0011] According to another example, a self-actuating device (i.e., automatic, without human intervention) is provided to move the plates away from each other along axis A. This automatic adjustment device can be configured to gradually move the plates away from each other along axis A as the thickness of the battery cell gradually increases. In this case, the adjustment is essentially continuous.

[0012] Alternatively, the automatic adjustment device for adjusting the distance between the plates can be configured to move the plates away from each other along axis A only when a predetermined additional stress value (relative to the initial stress) is exceeded during the gradual increase in the thickness of the battery cells. In this case, a gradual automatic adjustment is achieved. An example of such a device can be obtained in the form of a torque limiter, i.e., a device formed by a clutch / brake acting on a shaft, with a rope partially wound around the shaft. The torque limiter has a preload that is capable of keeping the shaft locked until a preset torque is exceeded to release the unwinding rope. The unwinding of the rope and the subsequent loosening of the battery cells gradually reduce the axial stress until the torque limiter locks the battery cells in a new position to await the next time the preset torque is exceeded.

[0013] Regarding the sealing of the upper and lower surfaces of the battery pack, the battery cells may include upper and lower lip elements that project along axis A, stagger between adjacent battery cells, and at least partially overlap. In this way, the battery pack is sealed both top and bottom as the distance between the battery cells increases. Even more preferably, the aforementioned lip elements have shaped hook-shaped edges that penetrate each other to define the end travel of the maximum distance between adjacent battery cells.

[0014] Finally, the invention is also extended to electric road vehicles on which a battery pack according to the purposes of the appended claims is mounted. Preferably, the battery pack is arranged transversely to the longitudinal direction of the vehicle and mounted on a frame behind the passenger compartment. Attached Figure Description

[0015] The invention will now be described with reference to the accompanying drawings, which illustrate several non-limiting embodiments of the invention, wherein:

[0016] · Figure 1 This is a schematic perspective view of an electric vehicle equipped with the battery pack according to the present invention;

[0017] · Figure 2 It is a schematic three-dimensional diagram of a battery pack for an electric vehicle based on existing technology;

[0018] · Figure 3 This is a schematic perspective view of the battery pack of an electric vehicle according to the present invention;

[0019] · Figure 4 yes Figure 3 A magnified view of the battery pack modules;

[0020] · Figure 5 and Figure 6 It shows two different working positions. Figure 3 Details of the battery pack module. Detailed Implementation

[0021] refer to Figure 1 The number 1 generally represents a road vehicle with two front wheels and two rear wheels. Road vehicle 1 is a vehicle with at least partial electric propulsion and includes a frame 2. Road vehicle 1 includes a battery pack 3, which in this example is supported by the frame 2 within an engine compartment 4. As can be seen, preferably, the battery pack is located behind the passenger compartment 5, for example on the vehicle platform, behind the seats housed within the passenger compartment 5.

[0022] An example of the improved battery pack 3 according to the present invention is shown in Figure 2 As can be seen in the image. In this example, and according to the invention, the battery pack 3 has an elongated shape along axis A and a substantially parallelepiped shape. (As shown in...) Figure 1 As can be seen, battery pack 3 can be arranged transversely to the longitudinal axis of the vehicle. Specifically, battery pack 3 is suitable for connection to the electric propulsion system (not shown) of vehicle 1, and is suitable for storing electrical energy generated by an electric motor (not shown) or released from other sources. (As shown in...) Figure 2As can be seen, the battery pack 3 includes a plurality of planar electrochemical battery cells 6 arranged in a group along axis A and a support structure 7, which includes two retaining plates 8 and 9 opposite to and parallel to the battery cells 6 along axis A. The two plates 8 and 9 define a distance d along axis A and a housing volume of the battery cells 6. As is known, the battery cells 6 are housed in the support structure 7 at the beginning of their service life, having an initial preload along axis A, which generates corresponding initial axial stresses acting on the plates 8 and 9. As is also known, each battery cell 6 includes two flat surfaces orthogonal to axis A and a thickness along axis A, which gradually increases during the service life of the battery pack 3. According to the prior art, Figure 2 The distance d shown is fixed.

[0023] Figure 3 A battery pack according to the invention is shown, in which it can be noted how plates 8 and 9 are configured to move away from each other along axis A such that an increase in the thickness of battery cell 6 does not result in a corresponding increase in the axial stress acting on plates 8 and 9. In other words, Figure 1 The distance d increases until it reaches the distance indicated by D, so that the increase in the thickness of the battery cell does not generate additional stress to be released onto the plate. In the example shown, a manually operable device is provided to move plates 8 and 9 gradually away from each other along axis (A). Figure 4 As can be seen, a plurality of rope elements 10 are arranged around the battery pack 3 and configured to hold the plates 8 and 9 in a fixed position; wherein the manually operable device for moving the plates 8 and 9 away from each other along axis A includes an irreversible screw-nut connector 11 configured to untie the rope elements 10. Figure 3 Reference numeral 13 in the figure identifies the guide used to guide the expansion of the battery pack 3 along axis A.

[0024] Finally, as in Figure 5 and Figure 6 As can be seen, battery cell 6 includes an upper lip element and a lower lip element 12 that protrude along axis A, stagger between adjacent battery cells 6, and at least partially overlap. In this way, as the distance between battery cells increases (from... Figure 5 s to Figure 6 In the example, battery pack 3 is always sealed at both the top and bottom (S). It can also be noted that, in this example, the lip element has a shaped hook-like edge to define the end travel of the maximum distance S between two adjacent battery cells.

Claims

1. A battery pack (3) for an electrically propelled road vehicle (1); The battery pack (3) includes: - Multiple planar electrochemical cell units (6) are arranged in groups along axis (A); - Support structure (7) including two retaining plates (8, 9) opposite to and parallel to the battery cell (C) along the axis (A), wherein the two plates (8, 9) define a receiving volume of the battery cell (6); At the start of its service life, the battery cell (6) is housed in the support structure (7) and has an initial preload along the axis (A), which generates a corresponding initial axial stress acting on the plates (8, 9). Each battery cell (6) includes two flat surfaces orthogonal to the axis (A) and a thickness along the axis (A) that gradually increases during the lifespan of the battery pack (3); Its features are: The plates (8, 9) are configured to move away from each other along the axis (A) such that an increase in the thickness (6) of the battery cell does not result in a corresponding increase in the axial stress on the plates (8, 9).

2. The battery pack (3) according to claim 1, characterized in that, A manually operable device is provided to move the plates (8, 9) away from each other along the axis (A).

3. The battery pack (3) according to claim 2, characterized in that, A plurality of rope elements (10) are provided around the battery pack (3) and configured to hold the plates (8, 9) in place; wherein the manually operable means for moving the plates (8, 9) away from each other along the axis (A) includes an irreversible screw-nut connector (11) configured to untie the rope elements (10).

4. The battery pack (3) according to claim 2, characterized in that, An automatic actuation device is provided to move the plates (8, 9) away from each other along the axis (A).

5. The battery pack (3) according to claim 4, characterized in that, The automatic actuation device for moving the plates (8, 9) away from each other along the axis (A) is configured to move the plates (8, 9) away from each other along the axis (A) as the thickness (6) of the battery cell gradually increases.

6. The battery pack (3) according to claim 4, characterized in that, The automatic actuation device for moving the plates (8, 9) away from each other along the axis (A) is configured to move the plates (8, 9) away from each other gradually along the axis (A) when a predetermined strain value is exceeded during the gradual increase of the battery cell thickness (6).

7. The battery pack (3) according to any one of the preceding claims, characterized in that, The battery cell (6) includes an upper lip element and a lower lip element (12) that protrude along the axis (A), stagger between adjacent battery cells (6), and at least partially overlap, so that the battery pack (3) is sealed from top to bottom even as the distance (S) between the battery cells increases.

8. The battery pack (3) according to claim 7, characterized in that, The lip element has shaped hook-shaped edges that penetrate each other to define the endpoints of the maximum distance (S) between two adjacent battery cells.

9. An electrically propelled road vehicle (1); characterized in that, The vehicle (1) includes a battery pack (3) according to any one of the preceding claims.

10. The vehicle according to claim 9, characterized in that, The battery pack (3) is arranged transversely to the longitudinal direction of the vehicle (1) and is mounted on the frame (2) behind the passenger compartment (5).

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