Battery pack for electric road vehicle and method of compensating for electrochemical cell thickness variation of battery pack

Abstract

A battery pack (5, 5 ') for an electric road vehicle (1), comprising: a first electrochemical cell (11, 12) comprising in sequence a cathode, an anode and a solid electrolyte electrically connected to the cathode and the anode, the first cell (11, 12) having a first thickness L along a direction X, the first thickness L in use increasing as the first cell (11, 12) is activated; a first compensation element (15, 15 ') cooperating with the first battery (11, 12) along a direction X to withstand, in use, a compressive force F that varies along the direction X between a minimum value Fbol and a maximum value Fol, the compensation element (15, 15') having a second thickness S along the direction X that varies between a maximum value Sbol and a minimum value Seol reached when the minimum value Fbol and the maximum value Fol.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the priority benefit of Italian Patent Application No. 102023000021093 filed on October 11, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to a battery pack for an electric road vehicle.

[0004] The invention also relates to a method for compensating for thickness variations of an electrochemical cell of a battery pack of an electric or hybrid road vehicle. Background Art

[0005] For the purposes of this description and the appended claims, the expression "electric road vehicle" denotes both road vehicles having an electric powertrain only and road vehicles having an electric-combustion hybrid powertrain equipped with at least one battery pack capable of providing electrical power.

[0006] The battery comprises, in a known manner, a plurality of electrochemical cells which are interconnected in series and in parallel in order to achieve the desired overall voltage and energy density.

[0007] At its simplest, each battery includes a positive electrode, usually called the cathode, a negative electrode, usually called the anode, and a chemical substance, usually called the electrolyte, in which the positive and negative electrodes are immersed.

[0008] It is known that in order to obtain the desired high energy density suitable for the implementation of electric powertrains in the automotive industry, batteries with solid-state electrolytes and batteries with metallic lithium anodes can be used.

[0009] The thickness of each cell is smaller than its relative length and width.

[0010] During operation of a battery with a solid electrolyte, the thickness will inevitably increase due to the occurrence of electrochemical reactions.

[0011] It is necessary to ensure that the solid electrolyte always remains in contact with the electrodes by applying pressure to the battery from outside the battery.

[0012] This force must be maintained between a minimum and maximum value throughout the battery's operating life, even as the battery grows in thickness during use.

[0013] In order to meet the above requirements, it is known to use a receiving structure consisting of a rigid compensating element which is in contact with the battery according to the thickness direction of the battery.

[0014] These elements are able to elastically change their thickness and are able to exert increasing forces on the battery as the thickness of the battery increases.

[0015] However, newer generation batteries have larger thickness variations and require particularly high maximum force values ​​to be applied at the end of their operating life.

[0016] This inevitably leads to the use of bulky rubber elements, which compromises the energy density and ultimately the weight of the battery pack.

[0017] Furthermore, the stiffness of the compensating elements necessary to obtain the required pressure cannot compensate for the tolerances of the individual cell components, so that the pressure acting on each cell needs to be adjusted during the assembly stage.

[0018] The known battery pack further includes a plurality of heat sinks disposed between the batteries for cooling the batteries.

[0019] More specifically, the battery pack has a modular configuration along the thickness direction, wherein each module sequentially includes a first battery, a material layer resistant to high temperatures and thermal shocks, a compensation element, a second battery, and a heat sink.

[0020] Motor vehicle manufacturers need to ensure that solid-state electrolyte batteries can operate correctly for a long time while limiting their total weight and volume in order to reduce the overall size and weight of the battery pack.

[0021] Additionally, the automotive industry needs to simplify the design of battery packs as much as possible. Summary of the invention

[0022] It is an object of the present invention to provide a battery pack for an electric road vehicle which allows the manufacturer to meet at least one of the aforementioned needs in a simple and economical manner.

[0023] Since the present invention relates to a battery pack for an electric or hybrid road vehicle as follows: a battery pack for an electric road vehicle, comprising: at least one first electrochemical cell, which comprises in sequence a cathode, an anode and a solid electrolyte electrically connected to the cathode and the anode; the first cell having a first thickness L along a direction X, which increases with activation of the first cell in use; a first compensating element, cooperating with the first cell along the direction X to withstand a compressive force F in use, which varies between a minimum value Fbol and a maximum value Feol along the direction X; the compensating element having a second thickness S along the direction X, which varies between a maximum value Sbol reached at the minimum value Fbol and the maximum value Feol and a minimum value Seol; characterized in that the first compensating element is configured to undergo plastic deformation when subjected to the compressive force F of a predetermined value FS in use, the predetermined value F being greater than or equal to the minimum value Fbol and less than the maximum value Feol, so as to plastically reduce the second thickness S when the value of the force F exceeds the predetermined value FS, the above-mentioned object is achieved by the present invention.

[0024] The present invention relates to a method for compensating for thickness variations of electrochemical cells of a battery pack of an electric or hybrid road vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention may be fully understood by reading the following detailed description of two embodiments in conjunction with the accompanying drawings, wherein these two embodiments are provided only as non-limiting examples:

[0026] Figure 1 is a perspective view of a motor vehicle having a battery pack according to the invention, which is shown only in a schematic manner;

[0027] Figure 2 A front view of a housing of a battery pack according to a first embodiment of the present invention;

[0028] Figure 3 for Figure 1 and Figure 2 A front view of a battery pack;

[0029] Figure 4 For along Figure 3 A cross-sectional view of line IV-IV;

[0030] Figure 5 for Figures 1 to 4 A top view of a battery pack;

[0031] Figure 6 and Figure 7 Shown on a larger scale Figure 4 Every detail;

[0032] Figure 8 A front view of a housing of a battery pack according to a second embodiment of the present invention;

[0033] Fig. 9 for Figure 8 A front view of a battery pack;

[0034] Fig.10 For along Fig. 9 A cross-sectional view of line XX;

[0035] Fig.11 for Figures 8 to 10 A bottom view of a battery pack;

[0036] Fig.12 Shown on a larger scale Fig.10 Details;

[0037] Fig.13 and Fig.14 The trend of the force exerted by a battery on a receiving element of a battery pack is shown when the thickness of the battery varies, according to a known solution and according to the invention, respectively. DETAILED DESCRIPTION

[0038] like Figure 1 As shown, numeral 1 denotes as a whole a road vehicle provided with two front wheels 2 and two rear wheels 3. The road vehicle 1 is an at least partially electric vehicle and is provided with a frame 4. The road vehicle 1 comprises a battery pack 5 which, in this embodiment, is supported by the frame 4 within an engine compartment 6.

[0039] In the embodiment shown here, the battery pack 5 is arranged in the rear part of the passenger compartment 7 , for example in the region of the vehicle floor, behind the seats contained in the passenger compartment 7 .

[0040] like Figures 2 to 7 As shown, the battery pack 5 basically includes:

[0041] - housing 10; and

[0042] - A plurality of batteries 11 , 12 , housed in the housing 10 and connected to each other in series and in parallel to obtain the desired total voltage and energy density.

[0043] In particular, the batteries 11 , 12 are arranged parallel to the X direction.

[0044] Very simply and in a known manner, each cell 11 , 12 comprises a positive electrode, usually called cathode, a negative electrode, usually called anode, and a chemical substance, usually called electrolyte, in which the positive and negative electrodes are immersed.

[0045] In more detail, the housing 10 has a parallelepiped shape.

[0046] The housing 10 has a length along the direction Y, a width along the direction X perpendicular to the direction Y, and a height along the direction Z perpendicular to the direction X and the direction Y.

[0047] In particular, the height of the housing 10 is smaller than the length and width of the housing 10 .

[0048] Similarly, each battery 11 , 12 has a length along the Y direction, a thickness along the X direction, and a height along the Z direction.

[0049] In particular, the thickness L of each cell 11 , 12 along direction X is smaller than the length and height of the same cell 11 along the corresponding directions Y, Z.

[0050] The housing 10 is defined by:

[0051] A pair of walls 30, 31 facing each other along the direction Z are located on corresponding planes orthogonal to the direction Z ( Figure 4 );

[0052] A pair of walls 32, 33 facing each other along direction X are located on corresponding planes orthogonal to direction X and are interposed between walls 30, 31 along direction Z ( Figure 3 );as well as

[0053] A pair of walls 34, 35 facing each other along direction Y are located on corresponding planes orthogonal to direction Y and are located between walls 30, 31 along direction Z and between walls 32, 33 along direction X ( Figure 3 ).

[0054] The walls 32, 33 may be made of an electrically insulating material.

[0055] After the electrochemical reaction, the thickness L of the battery 11, 12 parallel to the axis X increases during operation from a value Lbol assumed when the battery 11, 12 starts to operate to a value Leol assumed at the end of the operating life of the battery 11, 12.

[0056] In addition, the battery pack 5 also includes ( Figure 3 and Figure 4 ):

[0057] a plurality of compensating elements 15 cooperating with the cells 11 , 12 along the direction X so as to exert pressure on the cells 11 , 12 and thereby exert a force F along the direction X on the cells 11 , 12 to ensure that the solid electrolyte remains in contact with the anode and the cathode;

[0058] a plurality of layers 16 made of a material resistant to high temperatures and thermal shocks, such as mica, located on a plane substantially orthogonal to the direction X and spaced apart from one another along the direction X; and

[0059] A plurality of heat dissipation elements 17 are made of a heat conductive material, such as heat dissipation fins, which are mainly located on a plane orthogonal to the direction X and are spaced apart from each other along the direction X.

[0060] The batteries 11 , 12 , the compensating element 15 , the layer 16 and the element 17 define a modular structure 18 accommodated in the housing 10 .

[0061] More specifically, the modular structure 18 includes a plurality of modules M which are repeated in sequence along the direction X.

[0062] Along direction X, each module M comprises:

[0063] Battery 11;

[0064] Layer 16;

[0065] Compensation element 15;

[0066] a battery 12; and

[0067] Element 17.

[0068] like Figure 7 As shown, each layer 16 comprises a respective end edge 22 which is opposite one another along the direction Y and is fixed to the casing 10 .

[0069] As the thickness L of the batteries 11 and 12 increases during the relevant working process, the thickness S of each compensation element 15 along the X direction also varies between the maximum value Sbol and the minimum value Seol, which are assumed to be the maximum value Sbol and the minimum value Seol when the force F is the minimum value Fbol and the maximum value Feol respectively.

[0070] In particular, the minimum value Fbol of force F corresponds to the maximum value Sbol of thickness S of compensation element 15 and the minimum value Lbol of thickness L of batteries 11 and 12, and the maximum value Feol of force F corresponds to the minimum value Seol of thickness S of compensation element 15 and the maximum value Leol of thickness L of batteries 11 and 12.

[0071] Advantageously, each compensating element 15 is configured to deform itself plastically when it is subjected to a compressive force F of a predetermined value FS, which is greater than or equal to a minimum value Fbol and less than a maximum value Feol, so that the thickness S plastically decreases when the value of the force F exceeds the predetermined value FS.

[0072] In the particular case shown here, the value FS of the force F is greater than the minimum value Fbol.

[0073] In this way, each compensating element 15 reduces its thickness S elastically when subjected to a compressive force F comprised between a minimum value Fbol and a value FS, and reduces its thickness S plastically when subjected to a compressive force F comprised between a value FS and a maximum value Feol.

[0074] In the particular case presented here, the ratio between the maximum value Feol and the minimum value Fbol is less than 2, in particular less than or equal to 1.5.

[0075] Each compensation element 15 specifically includes:

[0076] a pair of walls 20 parallel to each other, respectively perpendicular to the direction X and spaced apart from each other along the direction X; and

[0077] The main body 21 is located between the walls 20 along the direction X.

[0078] like Figure 7 As shown, the wall 20 is spaced apart along the direction Z from the walls 30 , 31 .

[0079] The body 21 also comprises respective rounded ends 50 which project beyond the walls 31 , 32 along the direction Z and are in contact with the walls 30 , 31 .

[0080] In the particular case shown here, each compensating element 15 is made of a porous material. Alternatively, each compensating element 15 is made of a metallic material.

[0081] In particular, each element 17 comprises in sequence ( Figure 6 ):

[0082] a main portion 40 lying in a plane orthogonal to the direction X; and

[0083] A pair of end portions 41 are opposed to each other along the direction Z and are bent from the main body portion 40 toward the wall 33 in a direction perpendicular to the direction Z.

[0084] The battery pack 5 preferably includes ( Figure 4 ):

[0085] a pump 60 (shown schematically only);

[0086] a supply circuit 61 (also only shown schematically) for cooling the heat transfer fluid, configured to supply the fluid at a lower temperature into the body 21 of the compensating element 15; and

[0087] The heat exchanger 62 , also shown only schematically, is designed to cool the heat transfer fluid heated by the body 21 .

[0088] In the particular case shown herein, the heat transfer fluid is a pressurized liquid.

[0089] In use, the electrically connected batteries 11 , 12 generate the voltage and energy density required by the battery pack 5 through electrochemical reactions occurring in the respective anodes and cathodes.

[0090] During operation of the cells 11, 12, the compensating element 15 ensures that the force F is level in the X direction and thus ensures a uniform pressure on the cells 11, 12. This ensures a constant contact between the electrolyte and its respective anode and cathode.

[0091] After operation, the thickness L of the batteries 11 and 12 increases from a minimum value Lbol to a maximum value Leol, and the compressive force F applied to the compensation element 15 increases from a minimum value Fbol to a maximum value Feol, as shown in FIG. Fig.14 shown.

[0092] This increase in thickness L causes the thickness S of the compensating element 15 to decrease from a maximum value Sbol to a minimum value Seol, wherein the maximum value Sbol and the minimum value Seol are respectively reached at the minimum value Fbol and the maximum value Feol ( Fig.14 ).

[0093] The variation in thickness S of the compensating element 15 is caused by elastic deformation between the minimum force value Fbol and the value FS and by plastic deformation between the value FS and the maximum force value Feol ( Fig.14 ).

[0094] At the same time, the element 17 dissipates the heat generated by the operation of the batteries 11 , 12 , while the layer 16 ensures protection against uncontrolled temperature increases and resulting thermal shocks.

[0095] The circuit 61 supplies a heat transfer fluid into the body 21 of the compensating element 15 in order to cool the corresponding element 17 .

[0096] like Figures 8 to 12 As shown, numeral 5' denotes a battery pack according to another embodiment of the present invention.

[0097] Battery pack 5' is similar to battery pack 5 and only the differences therefrom will be described below; where possible, identical or equivalent components in battery packs 5 and 5' will be denoted by the same reference numerals.

[0098] More specifically, the battery 5 ′ differs from the battery 5 in that it does not comprise the element 17 and the wall 20 ′ is made of a thermally conductive material.

[0099] The wall 20 ′ is designed to dissipate heat generated by the batteries 11 , 12 during operation.

[0100] The wall 20 ′ has respective ends 50 ′ shaped like bellows, which are connected to respective walls 30 , 31 of the housing 10 .

[0101] The module M' of the battery pack 5' is different from the module M of the battery pack 5 in that it includes ( Fig.10 ):

[0102] corresponding layer 16;

[0103] corresponding battery 11;

[0104] a corresponding compensation element 15; and

[0105] The corresponding battery 12.

[0106] The operation of the battery pack 5 ′ is similar to that of the battery pack 5 , and therefore, only the parts different therefrom will be described in detail.

[0107] In particular, the wall 20 ′ of the compensating element 15 ′ dissipates the heat generated by the operation of the batteries 11 , 12 , ie in practice performs the function performed by the element 17 of the battery 5 .

[0108] The features of the battery 5, 5' and the method according to the invention reveal the significant advantages that can be obtained using them.

[0109] In particular, each compensation element 15 , 15 ′ collapses plastically when the force F exerted by the battery 11 , 12 reaches a value FS greater than a value Fbol corresponding to the respective minimum value Sbol and less than a value Feol corresponding to the respective maximum value Seol.

[0110] Accordingly, the thickness S of each compensation element 15 , 15 ′ is plastically reduced when the value of the force F is greater than the predetermined value FS.

[0111] Thus, the value of the force F exchanged between the compensation element 15, 15' and the battery 11, 12 is significantly reduced compared to those characteristics of the known solutions described in the background of this specification, which can be seen from Fig.13 and 14 This can be seen in the comparison.

[0112] For example, for the battery pack 5, 5', the ratio between the maximum force Feol and the minimum force Fbol is equal to 1.5, while in the known solution described in the background of this specification, this ratio is equal to 10 ( Fig.13 ).

[0113] Therefore, the size, weight and cost of the compensation element 15, 15' and the entire battery pack 5, 5' can be reduced.

[0114] Furthermore, the porous or metallic material of the compensating element 15, 15' compensates for the inevitable tolerances between the different components during the assembly phase. In this way, the compressive force exerted by the compensating element 15, 15' on the individual cells 11, 12 does not need to be adjusted.

[0115] The wall 20 ′ of the compensating element 15 ′ is designed to dissipate the heat generated by the operation of the batteries 11 , 12 .

[0116] In this way, the compensation element 15 ′ helps to limit any uncontrolled temperature rise and thermal shock caused by the operation of the batteries 11 , 12 , without the need to provide other additional elements 17 than the compensation element 15 ′.

[0117] The circuit 61 supplies a heat transfer fluid into the body 21 in order to cool the respective compensating element 15 , 15 ′ and further reduce the risk of uncontrolled temperature increases and thermal shocks caused by the operation of the batteries 11 , 12 .

[0118] Finally, the battery 5 , 5 ′ and the method disclosed and illustrated herein may be subjected to changes and modifications without departing from the scope of protection defined in the appended claims.

[0119] In particular, the value FS of the compression force F may be equal to the minimum value Fbol and less than the maximum value Feol.

[0120] Thus, each compensating element 15 , 15 ′ plastically reduces its thickness S when it is subjected to a compressive force F between a minimum value Fbol and a maximum value Feol.

Claims

1. A battery pack (5, 5') for an electric road vehicle (1), comprising: at least one first electrochemical cell (11, 12) comprising, in order, a cathode, an anode and a solid electrolyte electrically connected to the cathode and the anode; The first battery (11, 12) has a first thickness L along a direction X, and the first thickness L increases with activation of the first battery (11, 12) during use; a first compensating element (15, 15') cooperating with the first battery (11, 12) along the direction X to withstand a compressive force F in use, the compressive force F varying between a minimum value (Fbol) and a maximum value Feol along the direction X; the compensating element (15, 15') having a second thickness S along the direction X, the second thickness S varying between a maximum value Sbol reached at the minimum value Fbol and the maximum value Feol and a minimum value Seol; It is characterized in that the first compensation element (15, 15') is configured to undergo plastic deformation when subjected to the compression force F of a predetermined value FS during use, and the predetermined value FS is greater than or equal to the minimum value Fbol and less than the maximum value Feol, so as to plastically reduce the second thickness S when the value of the compression force F exceeds the predetermined value FS.

2. The battery pack (5, 5') according to claim 1, characterized in that: The compensating element (15, 15') is made of a porous material.

3. The battery pack (5, 5') according to claim 1, characterized in that: The compensation element (15, 15') is made of metal material.

4. The battery pack (5, 5') according to claim 1, characterized in that: The battery pack (5, 5') comprises a housing (10), wherein the housing (10) accommodates the first battery (11, 12) and the first compensation element (15, 15'), and the first compensation element (15, 15') comprises in sequence: a pair of walls (20) spaced apart from each other and orthogonal to the direction X; The main body (21) is located between the walls (20) along the direction X.

5. The battery pack (5, 5') according to claim 1, characterized in that: The battery pack (5, 5') comprises a second electrochemical cell (12, 11), wherein the second electrochemical cell (12, 11) is closely connected to the first electrochemical cell (11, 12) along the first direction X; The first compensation element (15) is located between the first battery and the second battery (11, 12) along the direction X; The battery pack (5, 5') further comprises: a third battery (11, 12), closely connected to the second battery (12, 11) along the first direction X; as well as An element (17), made of a heat-conducting material, different from the first compensation element (15), is interposed between the second and third batteries (12, 11; 11, 12) and is designed to dissipate heat generated by the battery pack (5) in use.

6. A battery pack (5, 5') according to claim 5, when it is dependent on claim 4, characterized in that The wall (20) has respective end edges (19) which are opposite to each other along a direction Y perpendicular to the first direction X and are separated by the housing (10); The body (21) protrudes along the second direction Y relative to the wall (20).

7. The battery pack (5, 5') according to claim 4, characterized in that: The wall (20') of the compensating element (15') is made of a thermally conductive material and is designed to dissipate heat generated by the battery pack (5') during use.

8. The battery pack according to claim 7, characterized in that: The wall (20') is fixed to the housing (10) by a pair of bellows-shaped ends (50').

9. The battery pack (5, 5') according to claim 1, characterized in that: The battery pack (5, 5') comprises a supply circuit (61) designed to supply a fluid under pressure into the compensating element (15, 15') in order to dissipate the heat generated in use by the activation of the first battery (11, 12).

10. An electric or hybrid road vehicle (1) comprising a battery pack (5, 5') according to claim 1.

11. A method for compensating for variations in a first thickness L of an electrochemical cell (11, 12) of a battery pack (5, 5') of an electric or hybrid road vehicle (1) along a direction X; The battery (11, 12) comprises, in sequence, a cathode, an anode and a solid electrolyte electrically connected to the cathode and the anode; The method comprises the following steps: i) activating the battery (11, 12) to determine the increase of the first thickness L of the battery (11, 12) in the direction X as the battery (11, 12) is activated during use; and ii) causing the second thickness S of the compensating element (15, 15') cooperating with the battery (11, 12) along the direction X to vary between a maximum value Sbol and a minimum value Seol, the maximum value Sbol and the minimum value Seol being reached when the variable compressive force F exerted by the battery (11, 12) on the compensating element (15, 15') has a minimum value Fbol and a maximum value Feol; Characterized in that the method comprises step iii): when the value of the compression force F exceeds a predetermined value FS of the compression force F, reducing the second thickness S by plastic deformation; the predetermined value FS is greater than or equal to the minimum value Fbol and less than the maximum value Feol.

12. The method according to claim 11, characterized in that The method comprises a step iv) of supplying a fluid under pressure into the compensating element (15, 15') in order to cool the battery (11, 12).

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