Patent Application
20220320566
The invention relates to an electrochemical cell and to a method for the manufacture thereof, and to a battery comprising one or more electrochemical cells. It finds particular application in the field of electrochemical cells or Li-ion batteries, and in particular aims to optimize the volume and electrical capacity of such cells, more generally optimization of their volumetric and gravimetric energy density.
As can be seen in a simplified and cross-sectional view in
The casing 1 comprises a bottom wall 4 which has an inner bottom face 4a, facing towards the internal volume, one or more side walls 5, 6 having an inner side face 5a, 6a facing the internal volume.
As can be seen clearly in
The punch and the outer die have a bottom that joins the at least one side wall with a rounding, so as not to damage the metal foil during the deep drawing operation. It is not possible to use an angular punch or an angled outer die, without risking the casing at the corners, which would lead to an unacceptable risk of tearing, or even without tearing the casing during the deep drawing operation in particular due to the fact that the casing tends to adhere to the punch and/or the outer die. Even using oil during the deep drawing operation, it is impossible to peel off the formed casing with a punch and/or an angled outer die without damaging it.
Further, a punch and an angled outer die are subject to substantial wear, which is not compatible with industrial mass manufacture.
However, one of the problems posed by the presence of the rounded edges at the bottom of the volume defined by the casing is that it can cause local curvature on the electrodes in the vicinity of the side walls, by packing them down towards the bottom. This can cause electrical short circuits. Additional elements to be inserted into the bottom of the casing can be provided to avoid this packing. But this makes the manufacturing process longer and more expensive and leads to an electrical capacity loss for the electrochemical cell. More generally, this phenomenon results in a decrease in volumetric and gravimetric energy density of the electrochemical cell.
In addition, the presence of these rounded edges reduces the heat exchange surface at the bottom wall. Now, dissipation of heat inside the electrochemical cell is a significant factor, and this is mainly by heat exchange at this bottom wall, in particular when several electrochemical cells are laterally juxtaposed to form a battery.
As shown in
One of the aims of the invention is therefore to resolve in particular the abovementioned problems. Thus, the aim of the invention is to provide an electrochemical cell with optimized volumetric and gravimetric energy density, and better capacity to dissipate the internal heat generated by the operation of the electrochemical cell.
The invention thus provides an electrochemical cell comprising a closed casing defining an internal volume inside which an electrode plate group having an alternation of positive and negative electrodes is arranged. These electrodes are respectively connected to two positive and negative electrical output terminals and surrounding separators. The electrode plate group is impregnated with electrolyte.
The casing further includes a bottom wall having an inner bottom face facing the internal volume, and at least one side wall having an inner side face facing the internal volume. The inner side face joins the inner bottom face with substantially the formation of an internal angle.
In the present application, by the expression “substantially forming an angle”, or “angular” should be taken to mean the joining of surfaces with the formation of a rounding of radius that is so small that it is considered that there is formation of an angle. The applicant/assignee considers that the presence of a rounding of radius substantially less than or equal to 0.5 mm corresponds to the formation of an angle. The concepts of angle, angular are therefore used in the present application to designate a junction between two walls forming a rounding of radius substantially less than or equal to 0.5 mm.
Also, as opposed to what has just been said, when the expression “rounding” is used without further precision, it designates the rounding at the junction between two walls as found in the prior art, and which is generally obtained by a deep drawing operation. Such a rounding is substantially greater than 0.5 mm.
In some embodiments, the electrochemical cell further comprises one or more of the following features, taken alone or following all technically possible combinations:
The invention also provides, in a second aspect, a battery comprising one or more electrochemical cells electrically connected in parallel and/or in series, wherein at least one of the electrochemical cells is an electrochemical cell as described above.
The invention further provides a method for producing an electrochemical cell according to a third aspect of the invention.
The electrochemical cell includes a closed casing defining an internal volume within which is disposed an electrode plate group having an alternation of positive and negative electrodes respectively connected to two positive and negative electrical output terminals and surrounding separators. The electrode plate group is impregnated with electrolyte.
The casing includes a bottom wall having an inner bottom face oriented towards the internal volume, and at least one side wall having an inner side face oriented towards the internal volume.
The method comprises, prior to placing the electrode plate group and closing the casing, a step of volume-forming of the casing so as to obtain the internal volume with a junction between the internal side face and the internal bottom face which is substantially angular with a given internal angle.
In some embodiments, the method further comprises one or more of the following features, taken alone or following all technically possible combinations:
Thus, the electrochemical cell and the battery according to the invention make it possible to reduce or even eliminate the unused bottom area in the cells of the prior art, make it possible to avoid the phenomenon of local packing of the electrodes in the vicinity of the side walls and the bottom, and enable better heat dissipation due to a larger surface area for heat exchange at the bottom wall.
The features and advantages of the invention will become apparent upon reading the following description, given by way of example, and non-limiting, with reference to the following drawings.
The electrochemical cell therefore comprises a casing 1, closed for example by a cover (not shown), and defining an internal volume. This internal volume is substantially parallelepipedal in this example.
The casing 1 is preferably formed in part or in whole in a metallic material, such as aluminum.
Within the internal volume defined by the casing 1, an electrode plate group 2 is arranged. Conventionally, this electrode plate group 2 comprises an alternation of positive and negative electrodes 3 connected respectively to two positive and negative electrical output terminals (not shown). Depending on the type of electrochemical cell, the two output terminals can, for example, be arranged at the top, at the cover. Alternatively, and also by way of example, one of the terminals may be disposed at the top, at the cover, the other being disposed at the bottom region, at the bottom wall 4.
The electrodes 3 surround separators (not shown), and the electrode plate group 2 is impregnated with electrolyte. It can be, for example, a Lithium-ion electrode plate group 2.
The casing 1 comprises in particular a bottom wall 4 and at least one side wall 5, 6. In the example shown in
Also,
In the remainder of the description, reference will be made to the side wall 5, 6, just as well to designate any of the two 5 or 6, or both 5 and 6, or the whole of the side walls of the casing 1 of an electrochemical cell, the casing 1 of which effectively comprises several side walls, as to designate the single side wall of the casing 1 of an electrochemical cell of the overall shape of an assembly corresponding to a solid of revolution.
The bottom wall has an inner bottom face 4a, facing the internal volume defined by the casing 1, and an outer bottom face 4b opposite the inner bottom face 4a, therefore facing the outside of the internal volume defined by the casing 1.
Each side wall 5, 6 also has an internal side face 5a, 6a facing the internal volume to defined by the casing 1, and an external side face 5b, 6b opposite the corresponding internal side face 5a, 6a, therefore oriented towards the outside of the internal volume defined by the casing 1.
The inner side face 5a, 6a of at least one of the side walls 5, 6, preferably of all the side walls 5, 6, joins the inner bottom face 4a with substantially the formation of an internal angle (a).
Thus, as can be seen in comparison with
In the example shown in
Preferably, the outer side face 5b, 6b of at least one of the side walls 5, 6 also joins the outer bottom face 4b of the bottom wall 4 with substantially the formation of an external angle (b). This external angle (b) may be different from the internal angle or angles (a), but is preferably substantially equal to that of the at least one internal angle (a), for example substantially equal to 90°.
As already mentioned above, all or part of the casing 1 is preferably made of a metallic material, such as aluminum. In particular, the bottom wall 4 and the at least one of the side walls 5, 6 are formed in this material.
A plurality of electrochemical cells may be electrically connected, including one or more electrochemical cells as described above, in parallel and/or in series, to form a battery.
In order to obtain the electrochemical cell of the invention, the volume of the casing 1 is created, prior to the placement of the electrode plate group 2 and the closure of the casing 1.
The starting material is a sheet formed from the desired material, preferably metallic (such as aluminum), and preferably of circular shape.
The volume-forming step is designed to allow the desired internal volume to be obtained, with a junction between the internal side face 5a, 6a of at least one of the side walls 5, 6 and the internal bottom face 4a of the bottom wall, substantially angular with internal angle (a).
Preferably, the material of the sheet intended to form the casing 1 after shaping is therefore metallic. In the following, reference to casing 1 can just as well designate the casing 1 which has been given its volume as this same casing 1 during the volume-forming operation, and thus including the planar sheet at the base of the casing before any volume formation.
In order to obtain the desired volume, a magneto-forming volume shaping step is carried out, as shown in two examples in
In the example of
In the example of
The shape of the template 10 is thus configured so as to allow the internal volume of the casing 1 to be formed by pressing the casing 1 against the template 10 under the effect of an electromagnetic field generated by the source 9.
Preferably, as shown in
The applicant/assignee has thus been able to ascertain a significant increase in volumetric and gravimetric energy density, by completely or partly removing the unused area 11 materialized in
In the example of an electrochemical cell with a rectangular bottom wall 4 of outer dimensions 26.5 mm×148 mm, an increase in 5% of the useful volume has been measured, which avoids the packing of electrodes mentioned above and leads to the increase in volumetric and gravimetric energy density, thanks to the obtaining of internal junctions between the side walls 5, 6 and the bottom wall 4 with an angle substantially equal to 90°. Furthermore, an increase in 20% of the heat exchange surface at the bottom wall 4 has been measured by virtue of these internal junctions at substantially right angles, in particular compared to an electrochemical cell of the prior art as shown in
It should be borne in mind that the present description is given by way of example and is not limiting of the invention. In particular, in this description, an example of an electrochemical cell of the Li-ion type and of substantially parallelepipedal assembly form is presented in the drawings. Nevertheless, all the considerations presented in this description, except where explicitly mentioned, apply to an electrochemical cell of a type other than Li-ion and another assembly shape other than a strictly parallelepipedal shape, for example a cylindrical shape.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR1908216 | Jul 2019 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/069476 | 7/10/2020 | WO |
