LEAKTIGHT FEEDTHROUGH OF GLASS-METAL TYPE, ITS USE FOR AN ELECTROCHEMICAL LITHIUM BATTERY, AND ASSOCIATED METHOD OF PRODUCTION

Abstract

A method for making a feedthrough comprises a/positioning of a body comprising a metallic wall with an orifice passing straight through it on a tool base, preferably one made of graphite; b/placing of the outer portion of the tool around the body; c/insertion of one or more metallic pins in the orifice emerging from the wall and then filling the rest of the orifice with a frit of electrically insulating material; d/placing the upper portion of the tool forming a piston against a zone including the orifice filled with the frit of electrically insulating material, preferably a glass frit, and in which the one or more pins is (are) inserted ; e/application of a temperature and pressure cycle, and a displacement of the piston, to carry out a flash sintering process.

Claims

1. A method for making a feedthrough comprising the following steps: a/positioning of a body comprising a metallic wall with an orifice passing straight through it on a tool base; b/placing of the outer portion of the tool around the body; c/inserting one or more metallic pins in the orifice emerging from the wall and then filling the rest of the orifice with a frit of electrically insulating material; d/placing the upper portion of the tool forming a piston against a zone including the orifice filled with the frit of electrically insulating material and in which the or each pin is inserted; e/application of a temperature and pressure cycle, and a displacement of the piston, to carry out a flash sintering process.

2. The method according to claim 1, whereby prior to step a/ and/or step d/ a sheet of carbon paper is placed respectively between the tool base and the body and/or between the body and the tooling piston.

3. The method according to claim 1, whereby prior to step a/ and/or step d/ a metallic sheet is placed respectively in contact with the lower end of the pin or pins and/or with the upper end of the pin or pins.

4. The method according to claim 1, wherein a metallic sheet is welded to at least one end of a pin, the welded sheet forming part of a current collector.

5. The method according to claim 1, wherein the sintered electrically insulating material of the seal is a sintered glass.

6. The method according to claim 5, wherein the sintered glass is based on alkaline oxides.

7. The method according to claim 1, wherein the pin or each pins is made of aluminium.

8. The method according to claim 1, wherein the tool base is made of graphite.

9. The method according to claim 1, wherein the frit is a glass frit

10. A lithium-ion (Li-ion) battery comprising a housing with a lid through which is realized a feedthrough obtained according to the method of claim 1.

11. The lithium-ion battery according to claim 10, wherein the lid is made of aluminium and wherein the or each pin or pins is made of aluminium or nickel or copper.

12. The lithium-ion battery according to claim 11, wherein the lid is made of aluminium 1050 or 3003.

13. The lithium-ion battery according to one of claims 10, wherein: the material of one or more negative electrodes of the battery is chosen from the group including graphite, lithium, titanate oxide Li.sub.4TiO.sub.5O.sub.12; and the material of one or more positive electrodes of the battery is chosen from the group including LiFePO.sub.4, LiCoO.sub.2, LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0079] Other advantages and characteristics of the invention will emerge more clearly upon perusal of the detailed description of exemplary embodiments of the invention given as an illustration and not a limitation, making reference to the following figures, in which:

[0080] FIG. 1 is a schematic perspective exploded view showing the different elements of a lithium-ion battery,

[0081] FIG. 2 is a front view showing a lithium-ion battery with its flexible package according to the prior art,

[0082] FIG. 3 is a perspective view of a lithium-ion battery according to the prior art with its rigid package comprised of a housing;

[0083] FIG. 4 is an axial section view of a feedthrough forming a terminal of an Li-ion battery according to one example of the prior art;

[0084] FIG. 5 is an axial section view of a feedthrough forming a terminal of an Li-ion battery according to another example of the prior art;

[0085] FIG. 6 is a perspective view of a feedthrough of glass-metal type forming a terminal of a Li-ion battery according to another example of the prior art;

[0086] FIG. 7 is an axial section view of a feedthrough, designed to form a terminal of a Li-ion battery according to one example of the invention;

[0087] FIG. 8 is an axial section view of a tooling in which the different components of a feedthrough according to the invention are housed, the tooling being adapted to carry out a flash sintering process;

[0088] FIG. 9 illustrates, in the form of temperature and pressure curves varying as a function of time, an example of a flash sintering cycle applied to the tooling shown in FIG. 8 in order to obtain the feedthrough according to the invention;

[0089] FIG. 10 illustrates schematically a representative stacking of elements of a feedthrough according to the invention on which tests were performed;

[0090] FIGS. 11A to 13B are reproductions of sectional views obtained by scanning electron microscope (SEM) at various magnifications of a stack illustrated schematically in FIG. 10 having undergone the application of a flash sintering cycle, at different temperatures.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0091] FIGS. 1 to 6 pertain to different examples of Li-ion battery, housings and feedthroughs forming terminals of the Li-ion battery according to the prior art. These FIGS. 1 to 6 have already been commented upon at the outset and thus will not be further discussed here.

[0092] For reasons of clarity, these same references designating the same elements of feedthroughs according to the prior art and according to the invention are used for all FIGS. 1 to 6.

[0093] Throughout the present application, the terms lower, upper, bottom, top, below and above are to be understood with regard to a housing of a Li-ion battery positioned vertically with its lid on top and the feedthrough exiting to the outside of the housing on top.

[0094] There is shown in FIG. 7 an example of a feedthrough forming the terminal 1 of a Li-ion battery according to the invention.

[0095] The feedthrough 1 according to the invention is realized through an orifice not emerging from both sides of a lid 3 of a Li-ion battery housing.

[0096] The feedthrough 1 represented comprises two pins 2, preferably of aluminium, passing through the orifice 32 and fixed to its inside by means of a seal of insulating glass frit 5, obtained by application of a flash sintering process.

[0097] Moreover, at each end of a pin there is secured a metal sheet 7 making it possible to close the battery housing by an adapted welding means, such as TIG, laser, electron beam welding. More precisely, the lower metal sheet 7, that is, the one designed to appear on the inside of the battery housing and designed to be welded to the current collector of one or the other of the electrodes of the electrochemical cell making up the battery.

[0098] To realize the feedthrough 1 according to the invention, one can use a graphite tooling 9 such as is shown schematically in FIG. 8. This tooling 9 is adapted to implement a flash sintering process.

[0099] The tooling 9 comprises an upper part forming a press piston 90, a lower part forming a base 91, the piston 90 being able to move relatively between outer peripheral walls 92, 93. The peripheral walls 92 make it possible to bound off a space inside which the glass frit is confined, while the outermost peripheral walls 93 determine the space for positioning of the lid 3.

[0100] The method according to the invention comprises the following steps:

[0101] Step a/: the lid 3 is positioned on the base 91 of the tooling. Prior to this, a carbon sheet 8 is inserted between the base 91 and the lid 3, in order to prevent any detrimental welding in the course of the process. Also prior to this, a metallic sheet of aluminium 7 is inserted, being in contact with each lower end of the pin 2.

[0102] Step b/: the outer portion 92, 93 of the tooling is put in place around the lid 3.

[0103] Step c/: the metal pins 2 are inserted, while holding them, into the orifice 32 emerging from the wall of the lid. The rest of the orifice is then filled with glass frit 5.

[0104] As an example, the glass frit 5 used can be that sold under the brand GL57 by the Ferro company. The chemical elements making up this glass frit with their percentage by weight are as follows: [0105] oxygen: 43.30% [0106] carbon: 7.51% [0107] silicon: 16.01% [0108] aluminium: 0.27% [0109] sodium: 12.09% [0110] titanium: 12.11% [0111] phosphorus: 1.06% [0112] potassium: 7.64%.

[0113] Step d/: the piston 90 of the tooling is then put in place against a zone comprising the orifice 32 filled with glass frit 5 and in which the pins 2 have been inserted and supported. Prior to this, as for step a/, a carbon sheet 8 is inserted between the lid 3 and the piston 90 and a metallic sheet made of aluminium 7 is inserted, being in contact with each upper end of the pin 2.

[0114] Step e/: a temperature and pressure cycle and a displacement of the piston 90 is done to carry out a flash sintering process.

[0115] One advantageous example of a cycle as a function of time is illustrated by the curves in FIG. 9.

[0116] The inventors have performed various tests of an alternating stack of glass frit 5 and aluminium pins 2 as shown in FIG. 10, with the aid of the tooling 9 and according to different flash sintering cycles.

[0117] FIGS. 11A and 11B show in cross section the densification of the substrate obtained at a temperature of 450 C., respectively, under the same magnification of 350, but with different contrast adjustment.

[0118] FIGS. 12A and 12B show in cross section the densification of the substrate obtained at a temperature of 480 C., respectively, under a magnification of 350 and 2000.

[0119] FIGS. 13A and 13B show in cross section the densification of the substrate obtained at a temperature of 500 C., respectively, under a magnification of 350 and 2000.

[0120] It emerges from these SEM views that there is a better densification of the glass and a better cohesion/contact between the aluminium and the glass frit at 500 C. as compared to 480 C. and 450 C.

[0121] The feedthrough 1 according to the invention can be realized on a lid 3 of a Li-ion battery housing both in a cylindrical geometry and in a prismatic geometry. In these different configurations, the terminal 1 according to the invention is negative, for example, while the positive terminal can be realized directly by welding, for example, also on the lid 3.

[0122] The invention is not limited to the examples just described; in particular, characteristics of the examples illustrated can be combined in the context of variants not illustrated.

[0123] Other variants and improvements can be contemplated without thereby leaving the scope of the invention.

[0124] While in the embodiments illustrated the material of the seal is a glass frit, any electrical insulating material will be suitable, as long as it is relatively close to the melting point, and the temperature of the flash sintering process is compatible with the various other materials, particularly the aluminium of the pins and of the lid.

[0125] Thus, for any suitable electrically insulating material, one must make sure that the temperature of the flash sintering process is slightly less than the melting temperature.

[0126] In the embodiment illustrated in FIGS. 7 and 8, the feedthrough comprises two pins 2 each constituting a terminal of the battery. It is quite possible to realize a leaktight passage with only a single terminal and to use the housing of the battery as a second terminal. More generally, one can contemplate leaktight feedthroughs according to the invention integrating a number of conductor pins equal to one, two, three, four, and so on.