How to Assemble an Electric Battery

Abstract

A method of assembling an electric battery (1) includes providing a hollow container (2) having side walls (3) and a bottom wall (4) defining an internal cavity (7), providing a top portion (8) of the hollow container (2) axially opposite the bottom wall (4), providing an insert (15) of conductive material having a connection portion (21), providing a lid (30) having a periphery (31), inserting an electrochemical cell (9) into the internal cavity (7), and mechanically and electrically connecting the insert (15) of conductive material to a positive electrode of the electrochemical cell (9). It is further provided to place a connection portion (21) of the conductive material insert (15) in electrical contact with the top portion (8) of the hollow container (2), to place a peripheral portion (31) of the lid (30) in contact with the connection portion (21), and to mechanically join the connection portion (21) of the conductive material insert (15), the top portion (8) of the hollow container (2) and the peripheral portion (31) of the lid (30) in a stable manner, and to place the peripheral portion (31) of the lid (30) in electrical contact with the top portion (8) of the hollow container (2).

Description

[Technical field]

[0001] The present invention refers to a method for constructing an electric battery of the type that can be used in applications where electrical energy needs to be made available. [Background technology]

[0002] An electric battery, also called a secondary electrochemical cell or secondary cell, is a device that converts chemical energy into electrical energy through a reversible oxidation-reduction reaction, and then converts electrical energy back into chemical energy by reversing this oxidation-reduction process.

[0003] The electric battery has a hollow container having an interior cavity into which is inserted an electrochemical cell formed by a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the negative electrode being electrically connected to the bottom surface of the container and the positive electrode being electrically connected to the top surface of the container.

[0004] In some types of applications, the electrochemical cell inserted into the hollow container is a type of electrochemical cell called a jelly roll or Swiss roll, which includes a sheet of insulating material on which are laid anode material, separator material, and cathode material, in the form of a continuous thin film or sheet. The multilayer thus constructed is rolled on itself and placed in the cavity of the container. The cathode material is placed in electrical contact with an electrode placed at the bottom of the hollow container and is electrically insulated from the container itself. The anode material is placed in electrical contact with a lid, which is placed to close the container and creates a further electrode.

[0005] Examples of such applications include lithium ion secondary batteries, nickel cadmium secondary batteries, and nickel metal hydride secondary batteries.

[0006] In the applicant's experience, to assemble an electric battery of the type briefly described above, first an insert of conductive material, for example made of copper, is welded to the anode material of an electrochemical cell. The electrochemical cell is then inserted into the cavity of a hollow vessel. At this point, the side wall of the hollow vessel must be electrically connected to the anode material, and so the insert of conductive material located inside the hollow vessel is welded to the inner surface of the side wall of the hollow vessel. Once welded, the hollow vessel is closed with a lid that is placed in electrical contact with the side wall of the hollow vessel, so that the lid assumes the same electrical potential as the side wall of the hollow vessel.

[0007] The applicant has realised that in the method of assembling an electric battery briefly described above, welding an insert of conductive material inside the cavity of the hollow vessel and to the inner surface of the side wall of the hollow vessel may be difficult or in any event expensive from a large scale production standpoint.

[0008] Since this welding is performed when the electrochemical cell is already inserted in the hollow vessel, the Applicant has observed in practice that the space available for welding between the insert of conductive material and the inner surface of the side wall of the hollow vessel may be very limited.

[0009] Applicant has realized that in order to produce a sufficient weld in this very limited space, it may be necessary to resort to specific welding machines and specific welding techniques, which may result in relatively long implementation times, i.e., relatively high production costs.

[0010] The applicant has realised that the method of assembling an electric battery briefly described above could be improved.

[0011] The applicant has indeed realised that after positioning of the lid on the hollow container, a mechanical connection between the free rim of the hollow container and the free rim of the lid must necessarily follow in order to ensure stable closure of the hollow container.

[0012] The applicant has realised that it may be possible to mechanically join the free rim of the hollow container to an insert of conductive material as well, the latter being mechanically joined to the lid.

[0013] Thus, the Applicant has found that by molding the conductive material insert such that the free rim of the conductive material insert is interposed between the free rim of the hollow container and the free rim of the lid, the subsequent process of mechanically bonding the conductive material insert to the free rim of the hollow container in the lid ensures electrical continuity between the conductive material insert, the lid and the side wall of the hollow container. Summary of the Invention

[0014] The present invention therefore relates to a method for assembling an electric battery.

[0015] Preferably, it is envisaged to provide a hollow container having side and bottom walls defining an interior cavity.

[0016] Preferably, it is envisaged to provide an upper part of the hollow vessel opposite said bottom wall along the axial direction.

[0017] Preferably, it is envisaged to provide an insert of conductive material having connections.

[0018] Preferably, it is envisaged to provide a lid having a perimeter.

[0019] Preferably, it is envisaged to insert an electrochemical cell into the internal cavity of said hollow vessel.

[0020] It is preferably envisaged that an insert of conductive material is mechanically and electrically connected to the anode of the electrochemical cell.

[0021] It is preferably envisaged to place a connection portion of the insert of conductive material in electrical contact with the upper portion of the hollow vessel.

[0022] It is preferably envisaged that the periphery of the lid will be placed in contact with the connection portion of the conductive material insert.

[0023] It is preferably envisaged that the connection of the insert of conductive material, the top of the hollow container and the periphery of the lid are mechanically joined in a stable manner.

[0024] It is envisaged that the periphery of the lid is preferably placed in electrical contact with the top of the hollow vessel.

[0025] The applicant has determined that it is possible to provide electrical contact between the side wall of the hollow container, the anode of the electrochemical cell, and the lid by placing the connection portion of the conductive material insert in electrical contact with the top of the hollow container, placing the peripheral portion of the lid in contact with the connection portion of the conductive material insert, and then mechanically joining the connection portion of the conductive material insert, the top of the hollow container, and the peripheral portion of the lid in a stable manner, and placing the peripheral portion of the lid in electrical contact with the top of the hollow container.

[0026] Applicant has also determined that this makes it possible to avoid welding an insert of conductive material within the cavity of the hollow vessel to the inner surface of the hollow vessel.

[0027] Applicant believes that in this manner, it will not be necessary to rely on specific welding machines and specific welding techniques that are adapted to operate in very confined spaces.

[0028] The applicant also believes that by avoiding welding the insert of conductive material to the inner surface of the hollow container within the cavity of the hollow container, the weld between the conductive material and the hollow container can be prevented from reaching the electrochemical cell in the event of accidental delamination and impairing the correct operation of the electric battery.

[0029] The term "conductive material" as used herein and in the claims that follow means a material capable of passing an electric current therethrough and having a resistance of 1×10 4 Greater than 1 x 10 Siemens / meter, preferably at 20°C 5Greater than siemens / meter, preferably 1 x 10 at 20°C 6 It refers to a material that has a conductivity greater than Siemens per meter.

[0030] The terms "mechanically join" or "mechanically couple," as used herein and in the claims that follow, mean joining two or more parts or components together such that the parts or components of the assembly form a mechanically constrained assembly.

[0031] The term "direct physical contact," as used herein and in the claims that follow, means physical contact between two parts or components without an intervening means between the two parts or components.

[0032] The term "direct electrical contact" as used herein and in the claims that follow means electrical continuity between two parts or components without an intervening conductive means between the two parts or components.

[0033] The term "electrical contact" as used herein and in the claims that follow means electrical continuity between two parts or components. The electrical contact between the two parts or components may be direct or may have an intermediate conductive means between the two parts or components.

[0034] The terms "plastic deformation" or "plastic deformation" as used herein and in the claims that follow mean deformation that does not disappear when the force that caused such deformation ceases.

[0035] The term "cold plastic deformation" as used herein and in the following claims refers to the treatment of metals at a treatment temperature below 40%, preferably below 30%, of the melting temperature of the metal being treated. For example, for a metallic material with a melting temperature of 1000°C, cold deformation occurs at a treatment temperature below 400°C, preferably below 300°C.

[0036] The electric battery obtained by the assembly method according to the present disclosure has a main axis of deployment, which is perpendicular to and between the other two axes of deployment, which is the main axis of reference for the elements which are part of the electric battery, and in this respect all directional and similar indications such as "axial", "radial", "circumferential", etc., are to be referred to and the indications "outer" or "inner" referring to the radial direction, "inner" or "outer" must be understood as directions away from or towards the axis.

[0037] The present invention may exhibit at least one of the preferred features described below, which may be present individually or in combination with one another in the method of assembling an electric battery of the present invention, unless expressly stated otherwise.

[0038] Preferably, no weld is provided between the insert of electrically conductive material and the inner wall of the hollow vessel at an axial location between the bottom wall of the hollow vessel and the periphery of the lid.

[0039] Preferably, placing the connection portion of the conductive material insert in electrical contact with the top of the hollow vessel includes placing the connection portion of the conductive material insert in direct physical contact with the top of the hollow vessel.

[0040] Preferably, placing the connection portion of the conductive material insert in electrical contact with the top of the hollow vessel includes at least partially overlapping the connection portion of the conductive material insert with the top of the hollow vessel.

[0041] Preferably, placing the periphery of the lid in contact with the connection portion of the conductive material insert comprises placing the periphery of the lid in physical contact with the connection portion of the conductive material insert.

[0042] Preferably, placing the periphery of the lid in contact with the connection portion of the conductive material insert includes at least partially overlapping the periphery of the lid with the connection portion of the conductive material insert.

[0043] Preferably, placing the connection portion of the conductive material insert in electrical contact with the top of the hollow container precedes placing the peripheral portion of the lid in contact with the connection portion of the conductive material insert.

[0044] Preferably, placing the connection portion of the conductive material insert in electrical contact with the top of the hollow vessel is after inserting the electrochemical cell into the interior cavity of said hollow vessel.

[0045] Preferably, mechanically joining the connection portion of the conductive material insert, the top of the hollow container, and the periphery of the lid is performed after placing the periphery of the lid in contact with the connection portion of the conductive material insert.

[0046] Preferably, the connection of the conductive material insert, the top of the hollow container, and the peripheral portion of the lid are mechanically joined, and the peripheral portion of the lid is placed in electrical contact with the top of the hollow container, simultaneously.

[0047] Preferably, mechanically joining the connection portion of the conductive material insert, the top of the hollow container, and the peripheral portion of the lid includes plastically deforming at least the connection portion of the conductive material insert and the top of the hollow container.

[0048] It is envisaged to provide an electrochemical cell having multiple layers wound on itself, preferably including a first layer made of an anode material constituting the anode, a second layer made of a cathode material constituting the cathode, and a third separator layer separating the anode material from the cathode material.

[0049] It is preferably envisaged that the first layer of electrochemical cells is axially offset relative to the second layer of electrochemical cells such that an axial end of the first layer axially exits the multilayer relative to an axial end of the second layer.

[0050] Preferably, it is envisaged that an axial end of the first layer of the electrochemical cell is plastically deformed to create the anode surface.

[0051] Preferably, the anode surface is not continuous.

[0052] Preferably, the anode surface is not flat.

[0053] Preferably, mechanically and electrically connecting an insert of conductive material to the anode of the electrochemical cell occurs prior to inserting the electrochemical cell into the interior cavity of the hollow vessel.

[0054] Preferably, providing an insert of conductive material includes providing a contact portion.

[0055] Preferably, said contact surface is provided in a central zone of an insert of electrically conductive material.

[0056] Preferably, the connecting portion of the insert of electrically conductive material extends axially away from the contact surface.

[0057] Preferably, the insert of conductive material is cup shaped, with a cup base forming said contact surface and a cup side wall forming the connection.

[0058] Preferably, the contact portion and the connection portion are made as one piece.

[0059] Preferably, the conductive material insert is made of copper.

[0060] Preferably, mechanically and electrically connecting an insert of conductive material to an anode of the electrochemical cell comprises welding the anode to the insert of conductive material.

[0061] Preferably, welding the anode to the conductive material insert comprises welding a contact portion of a conductive material insert to the anode of the electrochemical cell.

[0062] Preferably, it is envisaged that said contact portion of the insert of conductive material is provided with a plurality of fins.

[0063] Preferably, providing the plurality of fins includes creating notches through the conductive material.

[0064] Applicant has found that this allows the contact portion of the insert of conductive material to be axially deformable at the fin.

[0065] Preferably, each through notch is continuous and extends along a curved path.

[0066] Preferably, the curved locus has two lateral portions and a central portion, the central portion being connected to radially outer ends of the lateral portions.

[0067] Preferably, welding a contact portion of an electrically conductive material insert to an anode of the electrochemical cell comprises welding the anode to the electrically conductive material insert at at least one of the plurality of fins.

[0068] The applicant has found that by welding the anode to the at least one fin, axial displacements (within the hollow vessel) of the conductive material insert can be compensated for, avoiding that axial deformations of said at least one fin would mechanically stress the weld between the anode and the conductive material insert.

[0069] The applicant has also found that the deformability of the fins can compensate for the lack of uniformity of the anode surface and therefore ensure that the connection of the conductive material insert can slightly change its spatial orientation (e.g. during plastic deformation to define a stable mechanical bond between the side wall of the hollow container, the lid and the conductive material insert).

[0070] Preferably, it is envisaged that the anode is welded to the insert of conductive material at all fins of the plurality of fins.

[0071] It is envisaged to provide a hollow vessel, preferably made of steel.

[0072] It is preferably envisaged that the side and bottom walls of the hollow container are made as one piece.

[0073] Preferably, the hollow vessel is substantially cylindrical.

[0074] It is preferably envisaged to provide a steel lid.

[0075] Preferably, the lid and the hollow container are made of the same material.

[0076] Preferably, the lid is disc-shaped.

[0077] Preferably, it is envisaged that a lid is provided having a central portion from which a peripheral portion extends radially outwardly.

[0078] Preferably, the central and peripheral portions of the lid are made as one piece.

[0079] In a first embodiment, it is preferably envisaged to place the connection portion of the conductive material insert in direct electrical contact with the periphery of the lid.

[0080] In this embodiment, it is preferably provided that the periphery of the lid is placed in electrical contact with the top of the hollow vessel, followed by welding between the lid and said top of the hollow vessel.

[0081] Preferably, said weld is provided on an outer surface of the electric battery.

[0082] Preferably, said weld does not directly face the interior cavity of the hollow vessel.

[0083] Preferably, said weld does not face towards the anode of the electrochemical cell.

[0084] Preferably, provision is made for at least said peripheral portion of a lid to be interposed between said weld and said electrochemical cell.

[0085] Preferably, a lid is provided that seals the top of the hollow container together to isolate the internal cavity of the hollow container from the external environment.

[0086] Preferably, the sealing together of the lid and the top of the hollow container is obtained by said welding.

[0087] Preferably, performing a weld between the lid and the top of the hollow vessel includes welding connections of an insert of conductive material onto the lid and onto the top of the hollow vessel.

[0088] Preferably, said welding is obtained by melting the free ends of the connections of the inserts of conductive material.

[0089] Preferably, welding the connection portion of the conductive material insert onto the lid and onto the top of the hollow container comprises welding a free end of the connection portion of the conductive material insert onto an outer surface of the lid and onto a free end of the top of the hollow container.

[0090] Applicant has found that such welding can be advantageous in preventing direct electrical contact between the connection of the conductive material insert and the periphery of the top or lid of the hollow container from being adversely affected by differential thermal expansion between the conductive material insert and the lid or between the conductive material insert and the hollow container during charge and discharge cycles of the electrochemical cell.

[0091] Applicant has determined that this welding location does not require specific welding machines and techniques adapted to operate in very confined spaces.

[0092] Applicant has also determined that even if remnants of the weld were to peel away from the weld, such remnants of the weld would not be able to reach the cavity of the hollow vessel and the electrochemical cell.

[0093] In this embodiment, mechanically joining the connection portion of the conductive material insert, the top of the hollow container, and the periphery of the lid includes plastically deforming only the connection portion of the conductive material insert and the top of the hollow container.

[0094] Preferably, mechanically joining the connection portion of the conductive material insert, the top of the hollow container, and the peripheral portion of the lid includes plastically deforming said connection portion of the conductive material insert to form a curvature.

[0095] Preferably, such curvature has a radially inwardly facing concavity.

[0096] It is envisaged that such a curvature is preferably formed in the circumferential direction along the entire circumferential development of the upper part of the hollow vessel to form the groove.

[0097] Preferably, mechanically joining the connection portion of the conductive material insert, the top of the hollow container, and the periphery of the lid includes plastically deforming said top of the hollow container to form a curvature.

[0098] Preferably, said curvature comprises a radially inwardly directed concavity.

[0099] It is envisaged that such a curvature is preferably formed in the circumferential direction along the entire circumferential development of the upper part of the hollow vessel to form the groove.

[0100] Preferably, mechanically joining the connection portion of the conductive material insert, the top of the hollow container, and the periphery of the lid includes forming a curvature in the top of the hollow container to encompass the curvature of the conductive material insert.

[0101] Preferably, mechanically joining the connection portion of the conductive material insert, the top of the hollow container, and the periphery of the lid includes forming a curvature of the conductive material insert to encompass said periphery of the lid.

[0102] Preferably, forming the curvature in the conductive material insert and forming the curvature in the upper part of the hollow container are carried out simultaneously by plastically deforming the connection part of the conductive material insert superimposed on the upper part of the hollow container.

[0103] Preferably, forming the curvature of the conductive material insert to encompass said peripheral portion of the lid includes plastically deforming a connection portion of the conductive material insert to at least partially overlap the peripheral portion of the lid.

[0104] Preferably, plastically deforming the connection portion of the conductive material insert to at least partially overlap the periphery of the lid places the connection portion of the conductive material insert in direct electrical contact with the periphery of the lid.

[0105] In the second embodiment, mechanically joining the connection portion of the conductive material insert, the top of the hollow container, and the periphery of the lid preferably includes crimping the connection portion of the conductive material insert, the top of the hollow container, and the periphery of the lid together to create an edge that is folded back on itself.

[0106] Preferably, crimping together the connection portion of the conductive material insert, the top of the hollow container, and the peripheral portion of the lid includes plastically deforming the top of the hollow container to form a curvature.

[0107] Preferably, said curvature is formed on the outside of the side wall of the hollow vessel.

[0108] Preferably, this curvature comprises an axially oriented concavity towards the bottom wall of the hollow vessel.

[0109] It is preferably envisaged that the aforementioned curvature is formed in the circumferential direction along the entire circumferential development of the upper part of the hollow vessel to form the groove.

[0110] Preferably, crimping together the connection portion of the conductive material insert, the top of the hollow container, and the peripheral portion of the lid includes plastically deforming the connection portion of the conductive material insert to form a curvature.

[0111] Preferably, this curvature comprises an axially oriented concavity towards the bottom wall of the hollow vessel.

[0112] It is preferably envisaged to form the aforementioned curvature in the circumferential direction along the entire circumferential development of the connecting portion of the insert of conductive material to form the groove.

[0113] Preferably, crimping together the connection portion of the electrically conductive material insert, the top of the hollow container, and the periphery of the lid comprises plastically deforming the periphery of the lid to form a curvature.

[0114] Preferably, this curvature comprises an axially oriented concavity towards the bottom wall of the hollow vessel.

[0115] It is envisaged that the groove is preferably formed by forming said curvature in the circumferential direction along the entire circumferential development of the periphery of the lid.

[0116] Preferably, crimping the connection portion of the conductive material insert, the top of the hollow container, and the periphery of the lid together includes forming a curvature of the conductive material insert to encompass the curvature of the top of the hollow container.

[0117] Preferably, crimping the connection portion of the conductive material insert, the top of the hollow container, and the periphery of the lid together includes forming a curvature in the periphery of the lid to encompass the curvature of the conductive material insert.

[0118] Preferably, forming the curvature of the conductive material insert, forming the curvature of the top of the hollow container, and forming the curvature of the peripheral portion of the lid are carried out simultaneously by plastically deforming the peripheral portion of the lid that is overlaid on the connection portion of the conductive material insert that is overlaid on the top of the hollow container.

[0119] In this embodiment, placing the periphery of the lid in electrical contact with the top of the hollow container includes plastically deforming the periphery of the lid to define a free end that is inserted into the curvature of the top of the hollow container.

[0120] Preferably, said free end is ring-shaped and is inserted into the curvature of the upper part of the hollow vessel.

[0121] Preferably, plastically deforming the periphery of the lid to define a free end that is inserted into the curvature of the upper part of the hollow container is performed simultaneously with plastically deforming the periphery of the lid to form a curvature that encompasses the curvature of the insert of conductive material.

[0122] Preferably, providing a lid having a periphery includes disposing an insulating layer made of an electrically insulating and weather resistant material on a surface of the lid configured to face the interior cavity of the hollow container.

[0123] The applicant has found that it is possible to insulate the interior of the hollow container, i.e. the electrochemical cell, from environmental substances by providing an insulating layer on the inner surface of the lid. [Brief description of the drawings]

[0124] Further characteristics and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof, given as illustrative and non-limiting examples, with reference to the accompanying drawings, in which:

[0125] [Figure 1] 1 is a schematic cross-sectional view of an electric battery obtained according to the assembly method of the invention and a first embodiment thereof; [Diagram 2] 2 is a schematic cross-sectional view of an electric battery obtained according to the assembly method of the invention and a second embodiment. [Diagram 3] FIG. 2 is an enlarged view of a detail of the electric battery of FIG. 1. [Figure 4] FIG. 3 is an enlarged view of a detail of the electric battery of FIG. 2. [Diagram 5] FIG. 2 is a schematic side view of the components of the electric battery of FIG. 1. [Figure 5A] FIG. 3 is a schematic side view of the components of the electric battery of FIG. 2. [Figure 6] FIG. 3 is a schematic top view of the components of the electric battery of FIGS. 1 and 2; [Figure 7] FIG. 3 is a schematic perspective view of further components of the electric battery of FIGS. 1 and 2; [Figure 8]2 is a schematic diagram of an assembly sequence for the battery of FIG. 1 according to the assembly method of the present invention. FIG. [Figure 9] 2 is a schematic diagram of an assembly sequence for the battery of FIG. 1 according to the assembly method of the present invention. FIG. [Figure 10] 2 is a schematic diagram of an assembly sequence for the battery of FIG. 1 according to the assembly method of the present invention. FIG. [Figure 11] 3 is a schematic diagram of an assembly sequence for the battery of FIG. 2 according to the assembly method of the present invention. [Figure 12] 3 is a schematic diagram of an assembly sequence for the battery of FIG. 2 according to the assembly method of the present invention. [Figure 13] 3 is a schematic diagram of an assembly sequence for the battery of FIG. 2 according to the assembly method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0126] The representations in the accompanying figures are not necessarily to be understood to scale nor necessarily to respect the proportions of the various parts, in which identical or similar elements of different embodiments are indicated with the same reference signs.

[0127] The electric battery obtained according to the assembly method of the present invention is generally designated by the reference number 1.

[0128] The battery 1 has a main development axis X defined therein. Also defined are an axial direction parallel to the main development axis X, a radial direction included in a plane perpendicular to the main development axis X and passing through the main development axis X, and a circumferential direction disposed around the main development axis X and included in a plane perpendicular to the main development axis X.

[0129] For ease of exposure, reference is explicitly made to a generally cylindrical electric battery 1 whose main deployment axis X substantially coincides with the axis of symmetry of the electric battery 1 .

[0130] However, the electric battery 1 may also have a shape different from a cylindrical shape, for example the shape of a right prism having a rectangular base.

[0131] The electric battery 1 comprises a hollow container 2, a lid 30, an electrochemical cell 9 and an insert 15 of conductive material.

[0132] The hollow vessel 2 has a side wall 3 and a bottom wall 4. The side wall 3 and the bottom wall 4 are made as one piece of steel. The bottom wall 4 and the side wall 3 define an internal cavity 7 of the hollow vessel 2. The bottom wall 4 and the side wall 3 are preferably of the same thickness. The thickness of the side wall 3 and the bottom wall 4 is preferably between 0.1 mm and 1 mm, more preferably between 0.2 mm and 0.5 mm, for example 0.3 mm.

[0133] The electrode 5 is disposed on the bottom wall 4 of the hollow vessel 2 and is electrically insulated from the bottom wall 4. The electrode 5 is disposed at a central position of the bottom wall 4.

[0134] In the unassembled state of the electric battery 1, the hollow container 2 has an opening 6 opposite to the bottom wall 4. The hollow container 2 has a top part 8 opposite to the bottom wall 4 along the axial direction. The top part 8 extends all around the opening 6.

[0135] In the electric battery 1 shown in Fig. 1 obtained according to a first embodiment of the assembly method, the top part 8 has an (axial) straight section 10 which, in the unassembled state of the electric battery 1, makes an annular extension of the side wall 3 of the hollow vessel 2 (Fig. 8). This straight section 10 is made in one piece together with the side wall 3 of the hollow vessel 2. A curved section 11 which projects radially outwards and forms a radially enlarged section of the top part 8 and which extends in the circumferential direction is connected to the straight section 10. A further (axial) straight section 12 extends from the curved section 11 and which extends in the circumferential direction to form a further annular section. The top part 8 ends in a free end 13 which is also the free end of the further straight section 12.

[0136] In the electric battery 1 shown in Fig. 2 obtained according to a second embodiment of the assembly method, the top part 8 has an (axial) straight section 10 which, in the unassembled state of the electric battery 1, makes an annular extension of the side wall 3 of the hollow vessel 2 (Fig. 11). This straight section 10 is made in one piece together with the side wall 3 of the hollow vessel 2. Connected to the straight section 10 is a curved section 11 which projects radially outwards and develops in the circumferential direction forming a radially enlarged section of the top part 8. The top part 8 ends in a free end 13 which is also the free end of the curved section 11.

[0137] An electrochemical cell 9, better shown in FIG. 7, includes an anode and a cathode.

[0138] The electrochemical cell 9 is of the jelly roll or Swiss roll type and has a multilayer 14 wound on itself. The multilayer 14 has a first layer 16 made of an anode material that creates the anode of the electrochemical cell 9, and a second layer 17 made of a cathode material that creates the cathode of the electrochemical cell 9. The multilayer 10 further has a third separator layer (i.e., a further third layer) 18 that separates the first layer 16 from the second layer 17. One skilled in the art can select the materials for the first layer 16, second layer 17, and third layer 18 to provide the desired electrical performance for the electrochemical cell 9.

[0139] In a preferred embodiment, the first layer 16 is axially offset from the second layer 17 such that it emerges axially from the multilayer 14 wound on itself relative to the second layer 17. The portion of the first layer 16 emerging axially from the multilayer 14 is plastically deformed such that the free rim of the first layer 16 is bent to form an anode surface 19. This anode surface 19 is irregular and not continuous and has the function of increasing the contact surface of the first layer 16 at the axial end of the electrochemical cell 9.

[0140] The conductive material insert 15 is preferably made of copper. As best shown in Figures 5, 5A and 6 (wherein the conductive material insert 15 is shown not yet assembled in the electric battery 1), the conductive material insert 15 has a shape along a cross section perpendicular to the axial direction that substantially corresponds to the shape of the bottom wall 4 of the hollow vessel 2. In the illustrated embodiment, the shape of the conductive material insert 15 along a cross section perpendicular to the axial direction is substantially circular.

[0141] The insert of conductive material 15 has a substantially planar contact portion 20. The insert of conductive material 15 further has a connection portion 21. The connection portion 21 axially emerges from a radial end of the contact portion 20 and extends axially away from the contact portion 20.

[0142] The contact portion 20 is provided with a number of fins 22. Each fin 22 is defined by a respective through notch 23 axially crossing the contact portion 20. Each through notch 23 follows a curved path including two lateral portions 24 and a central portion 25 (FIG. 6). The lateral portions 24 develop along respective radial directions starting from the central zone of the contact portion 20 until they reach the peripheral zone of the contact portion 20. The central portion 25 connects the two lateral portions 24 and develops substantially in the circumferential direction. As shown diagrammatically in FIG. 6, each fin 22 is substantially petal-shaped and can be raised in the axial direction by rotating about a virtual hinge axis joining the free ends of the two lateral portions 24 of the notch 23. The fins 22 are preferably between 2 and 8 in number, for example the fin 18 is 4 in number.

[0143] Figure 5 shows a side view of the insert 15 of electrically conductive material (unassembled state) of the first embodiment of the electric battery shown in figure 1. In this embodiment, the connection part 17 has a (axial) straight section 26 which develops in the circumferential direction to form an annular section. The straight section 26 is directly connected to the contact part 20. A curved section 27 which projects radially outwards and forms a radially enlarged section of the upper part 17 and develops in the circumferential direction is connected to the straight section 26. A further (axial) straight section 28 develops from the curved section 27, which develops in the circumferential direction to form a further annular section. The connection part 17 ends in a free end 29, which is also the free end of the further straight section 28.

[0144] Figure 5A shows a side view of the insert 15 of conductive material (unassembled state) of the second embodiment of the electric battery shown in Figure 2. In this embodiment, the connection part 17 has a (axial) straight section 26 which develops in the circumferential direction to form an annular section. The straight section 26 is directly connected to the contact part 20. A curved section 27 which develops in the circumferential direction and projects radially outwards forming a radially enlarged section of the upper part 17 is connected to the straight section 26. The connection part 17 ends in a free end 29 which is also the free end of the curved section 27.

[0145] The lid 30 is made of steel. The lid 30 has a shape along a cross section perpendicular to the axial direction, which shape substantially corresponds to the shape of the bottom wall 4 of the hollow vessel 2. In the illustrated embodiment, the shape of the lid 30 along a cross section perpendicular to the axial direction is substantially circular.

[0146] The lid may have one or more reinforcing ribs. The lid 30 has a peripheral portion 31 circumferentially surrounding a central portion 30a.

[0147] In the first embodiment of the electric battery 1 shown in Figure 1, the peripheral portion 31 has a straight portion 32 extending radially in the unassembled state of the electric battery 1 (Figure 9). The peripheral portion 31 terminates in a free end 33, which is also a free end of the straight portion 32.

[0148] In a second embodiment of the electric battery 1 shown in Fig. 2, the peripheral part 31 has an (axial) straight axial part 34 which, in the unassembled state of the electric battery 1, creates an annular shoulder (Fig. 12). A (radial) straight radial part 35 which projects radially outwards and extends circumferentially along the entire peripheral part 31 is connected to the straight part 34. A further (axial) straight axial part 36 extends from the straight radial part 35, which extends circumferentially to form an annular part. The peripheral part 31 ends in a free end 37 which is also the free end of the further straight axial part 36.

[0149] In this embodiment, the lid 30 has an insulating layer 38 (shown diagrammatically in FIG. 4) of a material that has electrical insulating properties and provides protection from atmospheric agents.

[0150] An insulating layer 38 is arranged on the inner surface of the lid 30 intended to face the internal cavity 7 of the hollow vessel 2 .

[0151] Insulating layer 38 may be, for example, a moisture and salt vapor resistant polyurethane lacquer with a dielectric constant less than 4.0.

[0152] In the assembled state of the electric battery 1, the electrochemical cell 9 is inserted into the inner cavity 7 of the hollow vessel 2 with the negative electrode facing towards the bottom wall 4. The negative electrode is in electrical connection with the electrode 5. In particular, the second layer 17 of the multilayer 14 is arranged in electrical connection with the electrode 5 arranged on the bottom wall 4 of the hollow vessel 2.

[0153] The anode is electrically connected to the conductive material insert 15. This electrical connection is made by welding the contact 20 to the anode. In particular, the anode face 19 is welded to the fins 22 of the contact 20 of the conductive material insert 15.

[0154] In both embodiments, in the assembled state of the electric battery 1, a connection 21 of the insert 15 of conductive material is interposed between the top 8 of the hollow container 2 and the peripheral part 31 of the lid 30, as shown diagrammatically in Figures 3 and 4, which represent the assembled electric battery 1 in the two embodiments.

[0155] The connection portion 21 of the insert 15 of conductive material is in electrical contact with the top portion 8 of the hollow vessel 2 and the peripheral portion 31 of the lid 30 is in direct electrical contact with the top portion 8 of the hollow vessel 2 .

[0156] The connection portion 21 of the insert 15 of conductive material is in direct physical contact with the top portion 8 of the hollow vessel 2 .

[0157] The connection portion 21 of the conductive material insert 15 is also in direct physical contact with the periphery 31 of the lid 30 .

[0158] The connection portion 21 of the conductive material insert 15 and the top portion 8 of the hollow vessel 2 are plastically deformed to create a stable mechanical bond between the side wall 3 of the hollow vessel 2, the lid 30 and the conductive material insert 15.

[0159] In the first embodiment of the electric battery 1 shown in FIGS. 1 and in the enlarged view of FIG. 3, the connection portion 31 of the insert 15 of conductive material is also in direct electrical and direct physical contact with the peripheral portion 31 of the lid 30.

[0160] In this embodiment, the upper portion 8 of the hollow vessel 2 is plastically deformed to form a curve 40 defined between a curved portion 11 and a further straight portion 12 .

[0161] The connection portion 21 of the insert 15 of conductive material is arranged radially inside the upper portion 8 of the hollow vessel 2. The connection portion 21 of the insert 15 of conductive material is partially encompassed by a curvature 40, as shown in FIG.

[0162] At this point, the connection portion 21 of the insert 15 of conductive material is plastically deformed to form a curve 41 defined between the curved portion 27 and the further straight portion 28 .

[0163] The bend 41 of the connection portion 21 of the insert 15 of conductive material is inserted into the bend 40 of the top portion 8 of the hollow container 2, where it receives the peripheral portion 31 of the lid 30. Said peripheral portion 31 of the lid 30 is not bent, i.e. is not plastically deformed.

[0164] As shown in Fig. 3, the free end 13 of the upper part 8 of the hollow vessel 2 substantially faces the lid 30 in the radial direction. A weld 42 is provided between the free end 13 of the upper part 8 of the hollow vessel 2 and the lid 30. Such a weld 42 also affects the free end 29 of the connection 21 of the insert 15 of electrically conductive material.

[0165] In a second embodiment of the electric battery 1, shown in the enlarged view of FIG. 2 and in FIG. 4, the peripheral portion 31 of the lid 30 is not in direct electrical contact with the connection portion 21 of the insert 15 of conductive material.

[0166] Also, in this embodiment, the periphery 31 of the lid 30 is in direct physical contact with the connection portion 21 of the conductive material insert 15. In particular, the periphery 31 of the lid 30 is in direct contact with the connection portion 21 of the conductive material insert 15 via the insulating layer 38.

[0167] In this embodiment, the top portion 8 of the hollow vessel 2 has been plastically deformed to form a curve 43 defined by the curved portion 11 .

[0168] The connection portion 21 of the insert 15 of conductive material overlaps with the top portion 8 of the hollow container 2. As shown in FIG. 4, the connection portion 21 of the insert 15 of conductive material overlaps with the outside of the curve 43.

[0169] At this point, the connection portion 21 of the conductive material insert 15 is plastically deformed to form a curve 44 defined by the curved portion 27 .

[0170] The curvature 44 of the connection 21 of the insert 15 of conductive material embraces the curvature 43 of the top 8 of the hollow vessel 2 .

[0171] The periphery 31 of the lid 30 at least partially overlaps the connection portion 21 of the conductive material insert 15. The periphery 31 of the lid 30 overlaps the outside of the curvature 44 of the connection portion 21 of the conductive material insert 15.

[0172] At this point, the peripheral portion 31 of the lid 30 has been plastically deformed to form a curvature 45 defined by the radial straight portion 35. The curvature 45 of the peripheral portion 31 of the lid 30 encompasses the curvature 44 of the connection portion 21 of the conductive material insert 15.

[0173] 3, the free end 37 of the peripheral portion 31 of the lid 30 is inserted into the curvature 43 of the top portion 8 of the hollow container 2. The free end 37 of the peripheral portion 31 of the lid 30 is in direct physical and direct electrical contact with the top portion 8 of the hollow container 2.

[0174] At this point, the peripheral portion 31 of the lid 30 is plastically deformed to form an additional curvature 46 in the further axially straight portion 36. This additional curvature 46 encompasses the free end 13 of the top portion 8 of the hollow container 2.

[0175] For assembling the electric battery 1 according to the assembly method of the invention, in both embodiments it is provided that the hollow container 2, the lid 30, the insert 15 of conductive material and the electrochemical cell 9 are provided as elements separate from one another.

[0176] It is then envisaged that the conductive material insert 15 is mechanically and electrically connected to the anode of the electrochemical cell 9 .

[0177] This operation is carried out by welding the anode to the contact portion 14 of the conductive material insert 15. In particular, it is envisaged to weld the anode surface 19 to all the fins 22 of the contact portion 20 of the conductive material insert 15.

[0178] The assembly consisting of the electrochemical cell 9 and the insert 15 of conductive material is then inserted into the internal cavity 7 of the hollow vessel 2 with the anode facing towards the top 8 of the hollow vessel 2 .

[0179] The connection portion 21 of the insert 15 of electrically conductive material is placed in direct electrical and direct physical contact with the upper portion 8 of the hollow vessel 2 .

[0180] This is carried out by at least partially overlapping the connection portion 21 of the insert 15 of conductive material with the upper portion 8 of the hollow vessel 2 .

[0181] According to a first embodiment, as shown in Fig. 8, the connection part 21 of the insert 15 of conductive material is arranged in the upper part 8 of the hollow vessel 2 with the curved part 27 of the connection part 21 overlapping the curved part 11 of the upper part 8 of the hollow vessel 2. The further straight part 28 of the connection part 21 is arranged relative to the further straight part 12 of the upper part 8 of the hollow vessel 2. The straight part 28 of the connection part 21 is arranged in the straight part 10 of the upper part 8 of the hollow vessel 2.

[0182] The connection portion 21 of the insert 15 of electrically conductive material is completely contained in the upper portion 8 of the hollow vessel 2 in the radial direction.

[0183] 11 , the connection portion 21 of the insert 15 of conductive material is arranged in the upper portion 8 of the hollow vessel 2 with the curved portion 27 of the connection portion 21 overlapping the curved portion 11 of the upper portion 8 of the hollow vessel 2. The straight portion 28 of the connection portion 21 is arranged in the straight portion 10 of the upper portion 8 of the hollow vessel 2.

[0184] The connection portion 21 of the insert 15 of electrically conductive material is arranged radially inside the upper portion 8 of the hollow vessel 2 .

[0185] Thereafter, in both embodiments, it is envisioned that the peripheral portion 31 of the lid 30 is placed in direct physical contact with the connection portion 21 of the conductive material insert 15 .

[0186] This operation envisages at least partially overlapping the peripheral portion 31 of the lid 30 with the connection portion 21 of the insert 15 of conductive material.

[0187] According to the first embodiment, as shown in FIG. 9, the peripheral portion 31 of the lid 30 is placed on the connecting portion 21 of the conductive material insert 15 with the straight portion 32 of the peripheral portion overlapping the curved portion 27 of the connecting portion 21.

[0188] According to the second embodiment, as shown in Fig. 12, the peripheral portion 31 of the lid 30 is placed on the connection portion 21 of the conductive material insert 15, with a radially straight portion 35 of the peripheral portion 31 overlapping the curved portion 27 of the connection portion 21. A further axially straight portion 36 of the peripheral portion 31 is located radially outside the connection portion 21 of the conductive material insert 15. An axially straight portion 34 of the peripheral portion 31 is placed on the straight portion 26 of the connection portion 21 of the conductive material insert 15.

[0189] Thereafter, in both embodiments, it is envisaged that the connection portion 21 of the conductive material insert 15, the top portion 8 of the hollow vessel 2 and the peripheral portion 31 of the lid 30 are mechanically joined together, placing the peripheral portion 31 of the lid 30 in electrical contact with the top portion 8 of the hollow vessel 2.

[0190] This operation is carried out by cold plastic deformation of at least the connection 21 of the insert 15 of electrically conductive material and the top 8 of the hollow vessel 2 .

[0191] According to the first embodiment, only the connection portion 21 of the insert 15 of conductive material and the top portion 8 of the hollow vessel 2 undergo plastic deformation, as shown in FIG.

[0192] Such deformation envisages plastically deforming the connection portion 21 of the insert 15 of conductive material to form the bend 41. In the same plastic deformation operation, the top portion 8 of the hollow vessel 2 is also plastically deformed to form the bend 40. In this way, the bend 41 of the connection portion 21 and the bend 40 of the top portion 8 are formed simultaneously.

[0193] The plastic deformation of the connection portion 21 of the conductive material insert 15 and the upper portion 8 of the hollow vessel 2 permanently restrains the peripheral portion 31 of the lid 30 to the containment body 2 and places the peripheral portion 31 of the lid 30 in direct and permanent electrical contact with the upper portion 8 of the hollow vessel 2 (as well as with the connection portion 21 of the conductive material insert 15).

[0194] The plastic deformation of the connection part 21 of the insert 15 of conductive material and the top part 8 of the hollow vessel 2 is carried out by simultaneously cold bending the further straight part 12 of the top part 8 and the further straight part 28 of the connection part 21 of the peripheral part 31 of the lid 30. The plastic deformation of the connection part 21 of the insert 15 of conductive material and the top part 8 of the hollow vessel 2 places the free end 29 of the connection part 21 radially between the lid 30 and the free end 13 of the top part 8.

[0195] Although the mechanical bond between the connection 21 of the conductive material insert 15, the upper part 8 of the hollow container 2 and the peripheral part 31 of the lid 30 places the peripheral part 31 of the lid 30 in electrical contact with the upper part 8 of the hollow container 2 (thus enabling correct operation of the electric battery 1), it is envisaged that the connection 21 of the conductive material insert 15 is welded to the lid 30 and to the upper part 8 of the hollow container 2.

[0196] This operation envisages welding the free end 29 of the connection 15 of the insert 15 of conductive material to the outer surface of the lid 30 and to the free end 13 of the top 8 of the hollow vessel 2. The welding is performed by melting the free end 29 of the connection 15 of the insert 15 of conductive material. This welding also seals the internal cavity 7 of the hollow vessel 2 in a liquid-tight manner.

[0197] In this way, the electric battery 1 according to the first embodiment of the assembly method is completely assembled.

[0198] According to the second embodiment, as shown in FIG. 13 (and as seen in FIG. 4), the connection portion 21 of the conductive material insert 15, the top portion 8 of the hollow container 2 and the peripheral portion 31 of the lid 30 are all plastically deformed.

[0199] Such deformation envisages plastically deforming the connection portion 21 of the insert 15 of conductive material to form a curvature 44. In the same plastic deformation operation, the top portion 8 of the hollow container 2 is also plastically deformed to form a curvature 43. In the same plastic deformation operation, the peripheral portion 31 of the lid 30 is also plastically deformed to form a curvature 45. In this way, the curvature 44 of the connection portion 21, the curvature 43 of the top portion 8 and the curvature 45 of the peripheral portion 31 are formed simultaneously.

[0200] It should be noted that the same plastic deformation operation forms a further curvature 46 in the peripheral portion 31 of the lid 30. Therefore, the further curvature 46 in the peripheral portion 31 is also formed at the same time as the curvature 45 in the peripheral portion 31.

[0201] The plastic deformation of the connection portion 21 of the conductive material insert 15, the upper portion 8 of the hollow vessel 2 and the peripheral portion 31 of the lid 30 permanently restrains the peripheral portion 31 of the lid 30 to the containment body 2 and places the peripheral portion 31 of the lid 30 in direct and permanent electrical contact with the upper portion 8 of the hollow vessel 2 (similarly, places the connection portion 21 of the conductive material insert 15 in direct and permanent electrical contact with the upper portion 8 of the hollow vessel 2).

[0202] The plastic deformation of the connection 21 of the insert 15 of conductive material, the top 8 of the hollow container 2 and the peripheral portion 31 of the lid 30 is carried out by crimping, which creates an edge 47 that is folded back on itself.

[0203] Crimping is a cold plastic deformation process used to join the edges of thin metal sheets. The resulting bond is liquid-tight for containers closed by such a process. The crimp used is the so-called "double seam" crimp, formed by at least six layers of material with mechanical interlocking between them. In the case of the second embodiment, these layers are seven, given by two layers made at the connection 21 of the insert 15 of conductive material, two layers made at the top 8 of the hollow container 2 and three layers made at the periphery 31 of the lid 30, as shown in FIG. 4.

[0204] A smaller or larger size of portion 21 may result in 6 or 8 layers, respectively (the latter if portion 21 is additionally folded together with lid 30).

[0205] The plastic deformation of the connection portion 21 of the conductive material insert 15, the upper portion 8 of the hollow container 2 and the peripheral portion 31 of the lid 30 is carried out by cold bending the free end 37 of the peripheral portion 31 of the lid 30 and the free end 13 of the upper portion 8 of the hollow container 2, and by cold bending the assembly formed by the free end 37 of the peripheral portion 31, the free end 13 of the upper portion 8, the radial straight portion 35 of the peripheral portion 31 and the free end 29 of the connection portion 21 into contact with the side wall 3 of the hollow container 2.

[0206] In this way, the electric battery 1 according to the second embodiment of the assembly method is completely assembled.

Claims

1. A method for assembling an electric battery (1), comprising the steps of: Providing a hollow container (2) having a side wall (3) and a bottom wall (4) defining an interior cavity (7); providing an upper portion (8) of the hollow vessel (2) facing the bottom wall (4) along an axial direction; Providing an insert (15) of conductive material having a connection portion (21); providing a lid (30) having a periphery (31); Inserting an electrochemical cell (9) into the internal cavity (7) of the hollow vessel (2); mechanically and electrically connecting said conductive material insert (15) to the anode of said electrochemical cell (9); placing the connection portion (21) of the insert (15) of conductive material in electrical contact with the top portion (8) of the hollow vessel (2); placing the peripheral portion (31) of the lid (30) in contact with the connecting portion (21) of the conductive material insert (15); mechanically joining the connection portion (21) of the insert (15) of conductive material, the top portion (8) of the hollow container (2) and the peripheral portion (31) of the lid (30) in a stable manner, and placing the peripheral portion (31) of the lid (30) in electrical contact with the top portion (8) of the hollow container (2); A method comprising:

2. the mechanical joining of the connection portion (21) of the insert (15) of conductive material, the top portion (8) of the hollow container (2) and the peripheral portion (31) of the lid (30) and the placing of the peripheral portion (31) of the lid (30) in electrical contact with the top portion (8) of the hollow container (2) are carried out simultaneously; The method of claim 1.

3. Mechanically joining the connection portion (21) of the conductive material insert (15), the upper portion (8) of the hollow container (2), and the peripheral portion (31) of the lid (30) includes plastically deforming at least the connection portion (21) of the conductive material insert (15) and the upper portion (8) of the hollow container (2). The method of claim 1.

4. Providing an insert (15) of conductive material includes providing a contact portion (20) and providing the connection portion (21) spaced from the contact portion (20), the contact portion (20) having a plurality of fins (22) defined by notches (23) extending through the insert (15) of conductive material. The method of claim 1.

5. After placing the peripheral portion (31) of the lid (30) in electrical contact with the top portion (8) of the hollow container (2), a weld (42) is made between the lid (30) and the top portion (8) of the hollow container (2) on the outer surface of the electric battery (1). The method of claim 1.

6. performing the welding (42) between the lid (30) and the top (8) of the hollow container (2) includes welding the connection portion (21) of the conductive material insert (15) onto the lid (30) and onto the top (8) of the hollow container (2); The method of claim 5.

7. mechanically joining the connection portion (21) of the conductive material insert (15), the upper portion (8) of the hollow container (2), and the peripheral portion (31) of the lid (30) together includes plastically deforming only the connection portion (21) of the conductive material insert (15) and the upper portion (8) of the hollow container (2); The method of claim 1.

8. Mechanically joining the connection portion (21) of the conductive material insert (15), the upper portion (8) of the hollow container (2), and the peripheral portion (31) of the lid (30) includes plastically deforming the connection portion (21) of the conductive material insert (15) to form a curvature (41) that encompasses the peripheral portion (31) of the lid (30), and plastically deforming the upper portion (8) of the hollow container (2) to form a curvature (40) that encompasses the curvature (41) of the conductive material insert (15). The method of claim 1.

9. Mechanically joining the connection portion (21) of the conductive material insert (15), the top portion (8) of the hollow container (2), and the peripheral portion (31) of the lid (30) includes crimping the connection portion (21) of the conductive material insert (15), the top portion (8) of the hollow container (2), and the peripheral portion (31) of the lid (30) together to create an edge (47) folded back on itself. The method of claim 1.

10. The step of crimping the connection portion (21) of the conductive material insert (15), the top portion (8) of the hollow container (2), and the peripheral portion (31) of the lid (30) together includes plastically deforming the top portion (8) of the hollow container (2) to form a curve (43), plastically deforming the connection portion (21) of the conductive material insert (15) to form a curve (44) that encompasses the curve (43) of the top portion (8) of the hollow container (2), and plastically deforming the peripheral portion (31) of the lid (30) to form a curve (45) that encompasses the curve (44) of the conductive material insert (15).

10. The method of claim 9.

11. Placing the peripheral portion (31) of the lid (30) in electrical contact with the top portion (8) of the hollow container (2) comprises plastically deforming the peripheral portion (31) of the lid to form the curvature (45) that encompasses the curvature (44) of the conductive material insert (15), while simultaneously plastically deforming the peripheral portion (31) of the lid to define a free end (37) that is inserted into the curvature (43) of the top portion (8) of the hollow container (2). The method of claim 10.

Images