METHOD FOR CLADDING A BATTERY CELL

Abstract

Methods clad battery cells and comprise adhesively bonding at least one crosslinkable adhesive layer of a adhesive film and the at least one bottom side of a battery cell, adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film and at least two first side walls of the battery cell, adhesively bonding the at least one crosslinkable adhesive layer of the adhessive film and at least two second side walls of the battery cell, and adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film and at least one top side of the battery cell, wherein the methods further comprise at least partly crosslinking the crosslinkable adhesive layer.

Claims

1. A method for cladding a battery cell, the method comprising: (i) providing a battery cell comprising at least two opposite side walls S.sub.1 and S.sub.2, at least two opposite side walls S.sub.3 and S.sub.4, at least one bottom side U, and at least one top side O; (ii) providing an adhesive film comprising at least one crosslinkable adhesive layer and at least one carrier; (iii) contacting the adhesive film of (ii) and the at least one bottom side U of the battery cell of (i), comprising adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film and the at least one bottom side U of the battery cell; (iv) contacting the adhesive film and the at least two side walls S.sub.1 and S.sub.2, comprising adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film and the at least two side walls S.sub.1 and S.sub.2; (v) contacting the adhesive film and the at least two side walls S.sub.3 and S.sub.4, comprising adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film and the at least two side walls S.sub.3 and S.sub.4; and (vi) contacting the adhesive film and the at least one top side O, comprising adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film and the at least one top side O of the battery cell; wherein the method further comprises at least partly crosslinking the crosslinkable adhesive layer, where the at least partly crosslinking may be carried out after (ii) to (vi).

2. The method of claim 1, wherein the carrier comprises an insulating carrier having a specific volume resistivity of >10.sup.15 ?cm, determined according to DIN EN 62631-3-1 (VDE 0307-3-1): 2017-01.

3. The method of claim 1, wherein the carrier comprises one or more materials selected from the group consisting of polyimide, polybenzimidazole, polyamideimide, polyetherimide, polyacetal, polyphenylene sulfide, polyetheretherketone, polytetrafluoroethylene, polyamide 6, ultra-high molecular weight polyethylene, polypropylene, vinyl chloride resin, polystyrene, polyethylene terephthalate, acrylonitrile-butadiene-styrene, polycarbonate, polyvinyl chloride, ethylene-vinyl acetate, polyester, and a combination thereof.

4. The method of claim 1, wherein the crosslinkable adhesive layer has a thickness in the range from 10 to 150 ?m.

5. The method of claim 1, wherein the crosslinkable adhesive layer comprises a crosslinkable pressure-sensitive adhesive that comprises at least one polymer, at least one epoxy resin, and at least one photoinitiator.

6. The method of claim 5, wherein the crosslinkable pressure-sensitive adhesive comprises (a) 25% to 75%, by weight of at least one polymer; (b) 20% to 70%, by weight of at least one epoxy resin; (c) 0.01% to 5%, by weight of at least one cationic photoinitiator.

7. The method of claim 5, wherein the at least one epoxy resin comprises at least one epoxy resin E.sub.1 and at least one epoxy resin E.sub.2, and wherein the at least one epoxy resin E.sub.1 has a Tg of ?25? C. and the at least one epoxy resin E.sub.2 has a Tg of <25? C., determined according to Test Method 3.

8. The method of claim 5, wherein the crosslinkable pressure-sensitive adhesive further comprises (d) 3% to 30%, by weight, based on the sum of the % by weight of the at least one polymer and of the at least one epoxy resin, of at least one elastomer-modified epoxide E.sub.3 that comprises one or more materials selected from the group consisting of carboxy-terminated nitrile rubber, carboxy-terminated butadiene rubber, epoxy-terminated butadiene rubber, epoxy-terminated nitrile rubber, epoxy-functionalized polyurethane, polyester, polyether, and a combination thereof.

9. The method of claim 1, wherein the at least partial crosslinking of the crosslinkable adhesive layer is carried out after (ii) or wherein the at least partial crosslinking of the crosslinkable adhesive layer is carried out after (vi).

10. The method of claim 1, wherein the adhesive film has a width b and a length l, wherein, in (iii), the width b of the adhesive film protrudes by area ?b.sub.1 beyond the bottom side U of the battery cell, wherein, in (iv), the width b of the adhesive film protrudes by area ?b.sub.2 beyond the at least two opposite side walls S.sub.1 and S.sub.2 of the battery cell and by area ?b.sub.3 beyond the bottom side U of the battery cell, wherein ?b.sub.3<?b.sub.2<?b.sub.1 and ?b.sub.2<?b.sub.1 and where (v) comprises: (v.1) applying ?b.sub.2 to the at least two side walls S.sub.3 and S.sub.4, comprising adhesively bonding the adhesive layer of the adhesive film and the at least two side walls S.sub.3 and S.sub.4; and (v.2) applying ?b.sub.2 to the at least two side walls S.sub.3 and S.sub.4, comprising adhesively bonding the adhesive layer of the adhesive film and the at least two side walls S.sub.3 and S.sub.4, to form area ?l.sub.2.

11. The method of claim 10, wherein (vi) comprises: (vi.1) applying ?l.sub.2 to the top side O of the battery cells, comprising adhesively bonding the adhesive layer of the adhesive film and the at least one top side O, to form area ?l.sub.3, where ?l.sub.3<?l.sub.2; and (vi.2) applying ?l.sub.3 to the top side O of the battery cell, comprising adhesively bonding the adhesive layer of the adhesive film and the at least one top side O.

12. A clad battery cell, obtainable or obtained by the method claim 1.

13. The method of claim 2, wherein the insulating carrier is an electrically insulating carrier having a specific volume resistivity of >10.sup.16 ?cm, determined according to DIN EN 62631-3-1 (VDE 0307-3-1): 2017-01.

14. The method of claim 2, wherein the insulating carrier is an electrically insulating carrier having a specific volume resistivity of >10.sup.17 ?cm, determined according to DIN EN 62631-3-1 (VDE 0307-3-1): 2017-01.

15. The method of claim 3, wherein the one or more materials are selected from the consisting of polypropylene, polyethylene terephthalate, polycarbonate and polyvinyl chloride.

16. The method of claim 4, wherein the thickness of the crosslinkable adhesive layer has the range from 10 to 100 ?m.

17. The method of claim 4, wherein the thickness of the crosslinkable adhesive layer has the range from 20 to 60 ?m.

18. The method of claim 1, wherein the crosslinkable pressure-sensitive adhesive comprises (a) 30% to 70%, by weight of at least one polymer; (b) 30% to 65%, by weight of at least one epoxy resin; (c) 1% to 4%, by weight of at least one cationic photoinitiator.

19. The method of claim 1, wherein the crosslinkable pressure-sensitive adhesive further comprises (d) 5% to 20%, by weight, based on the sum of the % by weight of the at least one polymer and of the at least one epoxy resin, of at least one elastomer-modified epoxide E.sub.3 and wherein the at least one elastomer-modified epoxide E.sub.3 comprises one or more materials selected from the group consisting of carboxy-terminated nitrile rubber, carboxy-terminated butadiene rubber, epoxy-terminated butadiene rubber, epoxy-terminated nitrile rubber, epoxy-functionalized polyurethane, polyester, polyether, and a combination thereof.

20. The method of claim 1, wherein the crosslinkable pressure-sensitive adhesive further comprises (d) 7% to 15%, by weight, based on the sum of the % by weight of the at least one polymer and of the at least one epoxy resin, of at least one elastomer-modified epoxide E.sub.3 and wherein the at least one elastomer-modified epoxide E.sub.3 comprises one or more materials selected from the group consisting of carboxy-terminated nitrile rubber, carboxy-terminated butadiene rubber, epoxy-terminated butadiene rubber, epoxy-terminated nitrile rubber, epoxy-functionalized polyurethane, polyester, polyether, and a combination thereof.

Description

DESCRIPTION OF THE FIGURES

[0170] Further details and features of the present invention are apparent from the description of figures and exemplary embodiments. In this context, the respective features may be actualized on their own or multiply in combination with one another. The invention is not confined to the exemplary embodiments. The exemplary embodiments are represented schematically in the figures. Identical reference numbers in the individual figures here designate identical or functionally identical elements or elements that correspond to one another in terms of their functions. The figures are described jointly.

[0171] FIG. 1a shows a battery cell in an embodiment of the present disclosure and FIG. 1b shows a method for cladding a battery cell in an embodiment of the present disclosure.

[0172] FIGS. 2-7 show methods for cladding a battery cell in embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0173] FIG. 1a shows a battery cell 110 comprising a bottom side U 111, two opposite side walls S.sub.1 and S.sub.2 112, two opposite side walls S.sub.3 and S.sub.4 113, the top side O 114 and two battery contacts 115 on the top side 114. FIG. 1b shows a different variant of a battery cell 110 comprising a bottom side U 111, two opposite side walls S.sub.1 and S.sub.2 112, two opposite side walls S.sub.3 and S.sub.4 113, each bearing a battery contact 115, and a top side O 114. FIGS. 2-7 show various exemplary embodiments of a method for cladding a battery cell 110 according to FIG. 1a. In particular, FIG. 2 shows an exemplary embodiment of a method for cladding a battery cell 110. Step (i) 130 shows the provision of a battery cell 110, the battery cell comprising at least two opposite side walls S.sub.1 and S.sub.2, at least two opposite side walls S.sub.3 and S.sub.4, at least one bottom side U and at least one top side O. Step (ii) 132 shows the provision of an adhesive film 116 having a width b 118 and a length l 117. Step (iii) 134 shows the contacting of the adhesive film 116 and the at least one bottom side U of the battery cell 110, comprising adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film 116 and the at least one bottom side U 111 of the battery cell, where the width b 118 of the adhesive film 116 protrudes by area ?b.sub.1 119 beyond the bottom side U 111 of the battery cell 110. Step (iv) 136 shows the contacting of the adhesive film 116 and the at least two side walls S.sub.1 and S.sub.2 112, comprising adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film 116 and the at least two side walls S.sub.1 and S.sub.2 112, where the width b 118 of the adhesive film protrudes by area ?b.sub.2 121 beyond the at least two opposite side walls S.sub.1 and S.sub.2 112 of the battery cell 110 and where the length l 117 protrudes by area ?l.sub.1 120 beyond the top side O 114 of the battery cell 110. Steps (v) 138 and (vi) 140 show the contacting of the adhesive film 116 and the at least two side walls S.sub.3 and S.sub.4 113, comprising adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film 116 and the at least two side walls S.sub.3 and S.sub.4 113, where the width b 118 of the adhesive film 116 protrudes by area ?b.sub.3 122 beyond the bottom side of the battery cell 110, where ?b.sub.3 122 is adhered to the at least two side walls S.sub.3 and S.sub.4 113 and where ?b.sub.2 121 is adhered to the at least two side walls S.sub.3 and S.sub.4 113, comprising adhesively bonding the adhesive layer of the adhesive film 116 and the at least two side walls S.sub.3 and S.sub.4 113, to form area ?l.sub.2 124. Step (vi) 140 shows the contacting of the adhesive film 116 and the at least one top side O 114, comprising adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film 116 and the at least one top side O 114 of the battery cell 110, where ?l.sub.2 124 is adhered to the top side O 114 of the battery cell 110 to form area ?l.sub.3 125 and where ?l.sub.3 125 is adhered to the top side O 114 of the battery cell 110, comprising adhesively bonding the adhesive layer of the adhesive film 116 and the at least one top side O 114. Moreover FIG. 2 shows an exemplary embodiment of a clad battery cell 150 and an exemplary embodiment of a method for cladding a battery cell 110, which further comprises at least one step of at least partly crosslinking the crosslinkable adhesive layer with a crosslinking unit 100. FIG. 3 shows an exemplary embodiment of a method for cladding a battery cell 110, where the at least partial crosslinking of the crosslinkable adhesive layer is carried out after the step of (ii) with a crosslinking unit 100 in step 133. FIG. 4 shows an exemplary embodiment of a method for cladding a battery cell 110, where the at least partial crosslinking of the crosslinkable adhesive layer is carried out after the step of (vi) with a crosslinking unit 100 in step 141. FIG. 5 shows an enlarged detail from step (iv) 136. FIG. 6 shows a preferred exemplary embodiment of steps (v) 138 and (vi) 140, where in step 142 first ?b.sub.3 122 is adhered to the at least two side walls S.sub.3 and S.sub.4 113. Thereafter, in step 143, ?b.sub.2 121 is adhered to the at least two side walls S.sub.3 and S.sub.4 113, to form area ?l.sub.2 124. FIG. 7 shows a preferred exemplary embodiment of step 140, wherein the contacting of the adhesive film 116 and the at least one top side O 114, comprising adhesively bonding the at least one crosslinkable adhesive layer of the adhesive film 116 and the at least one top side O 114 of the battery cell 110. In this case, in step 145, first ?l.sub.2 124 is adhered to the top side O 114 of the battery cell 110 to form area ?l.sub.3 125. Thereafter, ?l.sub.3 125 is adhered to the top side O 114 of the battery cell 110.

[0174] The method for cladding a battery cell 110, as shown in FIG. 1b, proceeds analogously. The method begins with the provision of a battery cell 110, where the battery cell comprises at least two opposite side walls S.sub.1 and S.sub.2, at least two opposite side walls S.sub.3 and S.sub.4, at least one bottom side U and at least one top side O. A battery contact is present on each of the two opposite side walls S.sub.3 and S.sub.4.

[0175] The adhesive film comprising at least one crosslinkable adhesive layer and at least one carrier dads the two opposite side walls S.sub.1 and S.sub.2, the bottom side U and the top side O in one piece, with the ends of the adhesive film being adhered overlappingly to one another. The adhesive film has a larger width than the opposite side walls S.sub.1 and S.sub.2, the bottom side U and the top side O, and so the adhesive film exhibits a protrusion at the two opposite side walls S.sub.3 and S.sub.4, which each have a battery contact. The individual portions forming the protrusion at the side walls S.sub.1 and S.sub.2, at the bottom side U and at the top side O are folded over in any order and stuck on the respective side wall S.sub.3 and S.sub.4.

[0176] The method for cladding a battery cell 110 that is shown in FIGS. 2-7 and described in the disclosure associated with the figures, where there are two battery contacts on the top side O, can be transposed analogously to a battery cell 110 in which the side walls S.sub.3 and S.sub.4 each have a battery contact. In this variant of the method of the invention, the order of the component steps (v) and (vi) is switched.

LIST OF REFERENCE SYMBOLS

[0177] 100 crosslinking unit [0178] 110 battery cell [0179] 111 bottom side [0180] 112 side walls S.sub.1 and S.sub.2 [0181] 113 side walls S.sub.3 and S.sub.4 [0182] 114 top side O [0183] 115 battery contacts [0184] 116 adhesive film [0185] 117 length l [0186] 118 width b [0187] 119 area ?b.sub.1 [0188] 120 area ?l.sub.1 [0189] 121 area ?b.sub.2 [0190] 122 area ?b.sub.3 [0191] 124 area ?l.sub.2 [0192] 125 area ?l.sub.3 [0193] 130 step (i) [0194] 132 step (ii) [0195] 133 crosslinking of the crosslinkable adhesive layer after the step of (ii) [0196] 134 step (iii) [0197] 136 step (iv) [0198] 138 step (v) [0199] 140 step (vi) [0200] 141 crosslinking of the crosslinkable adhesive layer after the step of (vi) [0201] 142 step (v.1) [0202] 143 step (v.2) [0203] 144 partially clad battery cell [0204] 145 step (vi.1) [0205] 146 step (vi.2) [0206] 150 clad battery cell

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Test Methods

Test Method 1: Specific Volume Resistivity

[0207] The specific volume resistivity was determined according to DIN EN 62631-3-1 (VDE 0307-3-1): 2017-01.

Test Method 2: Peel Adhesion

[0208] The peel adhesions were determined in analogy to ISO 29862 (Method 3) at 23? C. and 50% relative humidity with a removal velocity of 300 mm/min and a removal angle of 180?. The substrates used were steel plates in accordance with the standard. The measurement strip was bonded using a roller application machine at 4 kg at a temperature of 23? C. The adhesive films were removed immediately after application or after a storage time of 24 h. The measurement value (in N/cm) was obtained as the mean value from three individual measurements.

Test Method 3: Tg

[0209] The glass transition temperature of polymers is determined by means of dynamic scanning calorimetry (DSC). For this determination, around 5 mg of the untreated polymer samples are weighed into a small aluminium crucible (volume 25 ?l) and closed with a perforated lid. Measurement takes place using a DSC 204 F1 from Netzsch, operating under nitrogen for inertness. The sample is first cooled to ?150? C., heated to +150? C. at a heating rate of 10 K/min, and cooled again to ?150? C. The subsequent, second heating curve is run again at 10 K/min and the change in the heat capacity is recorded. Glass transitions are recognized as steps in the thermogram. The glass transition temperature is evaluated as follows: a tangent is applied in each case to the baseline of the thermogram before 1 and after 2 of the step. In the region of the step, a line of best fit 3 is placed parallel to the ordinate in such a way as to intersect the two tangents, specifically so as to form two areas 4 and 5 (between the respective tangent, the line of best fit, and the measurement plot), of equal area. The point of intersection of the line of best fit positioned accordingly and the measurement plot gives the glass transition temperature.

Test Method 4: Dynamic Viscosity

[0210] For the purposes of the present invention, the dynamic viscosity is measured according to DIN 53019-1: from 2008-09; at 25? C., with a shear rate of 1 s.sup.?1.

Test Method 5: Softening Temperature

[0211] For the purposes of the present invention, the softening temperature is carried out in accordance with the relevant methodology, which is known as ring & ball and is standardized according to ASTM E28 (1.7.2018).

[0212] The determination of the softening temperature of the resin uses an HRB 754 automated ring & ball tester from Herzog. Resin specimens are first finely mortared. The resulting powder is introduced into a brass cylinder with a base aperture (internal diameter at the top part of the cylinder 20 mm, diameter of the base aperture in the cylinder 16 mm, cylinder height 6 mm) and melted on a hotplate. The amount introduced is chosen such that the resin, after melting, fully fills the cylinder without protruding.

[0213] The resulting sample body, complete with cylinder, is inserted into the sample mount of the HRB 754. Glycerol is used to fill the heating bath if the softening temperature lies between 50? C. and 150? C. If softening temperatures are lower a water bath may also be employed. The test balls have a diameter of 9.5 mm and weigh 3.5 g. In line with the HRB 754 procedure, the ball is arranged above the sample body in the heating bath and is placed down on the sample body. Located 25 mm below the base of the cylinder is a catch plate, with a light barrier 2 mm above it. During the measuring procedure, the temperature is raised at 5? C./min. Within the temperature range of the softening temperature, the ball begins to move through the base aperture in the cylinder until eventually it comes to rest on the catch plate. In this position, it is detected by the light barrier, and the temperature of the heating bath at this point in time is registered. A duplicate determination takes place. The softening temperature is the average value from the two individual measurements.

[0214] The raw materials used in the inventive and comparative examples are summarized in Table 1.

TABLE-US-00001 TABLE 1 Raw materials used Polyacrylate BA-GMA copolymer with a reactive fraction of 10 wt % GMA Levamelt Ethylene-vinyl acetate copolymer from Arlanxeo with 700 70% vinyl acetate fraction Breon Hot-polymerized nitrile rubber with 42% acrylonitrile N45H80 fraction Araldite Liquid bisphenol A epoxy resin from Huntsman with an GY-250 epoxide equivalent of 183-189 g/eq Araldite Solid bisphenol A epoxy resin from Huntsman with an GT-6071 epoxide equivalent of 450-465 g/eq Voranol Polyether polyol with a molecular weight of M = 700 2070 g/mol KH-560 3-Glycidyloxypropyltrimethoxysilane Dyhard Dicyandiamide from Alzchem with a particle size of less 100S than 10 ?m Curezol 2,4-Diamino-6-[2-methylimidazol-1-yl]-ethyl-s-triazine 2MZ-A from Evonik Photoinitiator Triarylsulfonium hexafluoroantimonate salts PET-Tr?ger 50 ?m transparent PET film from Fatra

Inventive Examples K1-K3 and Comparative Examples V1-V3

[0215] The adhesive layer of Inventive Examples K1-K3 and of Comparative Examples V2-V3 were produced according to the weight ratios in % by weight in Table 2. Comparative Example V1 is a commercially available, electrically insulating adhesive tape, tesa?58353, consisting of 50 ?m polyethylene terephthalate carrier with 35 ?m acrylate adhesive layer.

TABLE-US-00002 TABLE 2 Inventive Examples K1-K3 and Comparative Examples V1-V3 K1 K2 K3 V1 V2 V3 Polyacrylate 50 Breon 40 N45H80 Levamelt 700 40 40 20 Araldite 40 30 30 60 40 GY250 Araldite 10 20 30 40 GT6071 Voranol 2070 1 10 KH-560 1 Photoinitiator 1 1 1 1 Dyhard 100S 2.96 Curezol 2MZ- 1.2 A Bond >4 MPa >4 MPa >4 MPa <1 MPa >4 MPa >4 MPa strength (steel-steel) Peel >1 N/cm >1 N/cm >1 N/cm >1 N/cm cohesive cohesive adhesion adhesive adhesive adhesive adhesive failure, failure, failure failure failure failure no PSA* no PSA* * PSA = pressure-sensitive adhesive The adhesives in solution in butanone were coated out in a layer thickness of 35 ?m onto a 50 ?m polyethylene terephthalate carrier, freed from the solvent in a drying oven at 105? C. and enveloped with a siliconized PET liner.

Bond Strength

[0216] The bond strength of the adhesive layer obtained was measured in 100 ?m layer thickness and reported in MPa.

[0217] Curing conditions: Inventive Examples K1 and K2 and Comparative Examples V2 and V3 were irradiated using 365 nm UV-LED irradiation at 4 J/cm.sup.2 and bonded within less than a minute after activation. Measurement took place after an after-cure time of 7 days at 23? C. Comparative Example V1 is a non-reactive pressure-sensitive adhesive, thus requiring no activation. Inventive Example K3 is a thermally curable reactive pressure-sensitive adhesive which following application is cured at 145? C. for 25 minutes.

[0218] Determination of bond strength via tensile lap-shear test:

[0219] As a parameter of the quality of the bonding achieved, the bond strength of an assembly produced by the method of the invention was ascertained for the various adhesive tapes. This was done by quantitative determination of the bond strength in each case in a dynamic tensile lap-shear test in accordance with DIN EN 1465: 2009-07 at 23? C. and 50% rh with a testing velocity of 10 mm/min (results in N/mm.sup.2=MPa). Test bars employed were steel bars cleaned with acetone prior to bonding. The figure reported is the mean from three measurements.

METHOD EXAMPLES

[0220] Suitability for bubble-free bonding of the adhesive film to the battery cell walls is possessed for example by rollers which press the adhesive tape onto the battery cell wall with a rolling action beginning from one side.

Method Example M1

[0221] A rectangular piece of a PET adhesive film with a crosslinkable adhesive layer was cut to shape and freed from the liner. The adhesive film was then irradiated with a dose of 4 J/cm.sup.2 using a Hoenle UV-LED 365 nm (UV-LED, 365 nm, 4 s at 1000 mJ/cm.sup.2 s). The adhesive layer used was K2. The cladding of the battery cell was carried out in the following order: [0222] 1) bonding of the adhesive layer of the adhesive film with the bottom side U of the battery cell; [0223] 2) bonding of the adhesive layer of the adhesive film with the two large side walls S.sub.1 and S.sub.2; [0224] 3) bonding of the protrusion ?b.sub.3 on the bottom side U to the small side walls S.sub.3 and S.sub.4; [0225] 4) bonding of the lateral protrusion ?b.sub.2 to the small side walls S.sub.3 and S.sub.4; [0226] 5) bonding of the protrusion Al.sub.2 of the small side walls S.sub.3 and S.sub.4 to the top side O of the battery cell; [0227] 6) bonding of the protrusion ?l.sub.3 of the large side walls S.sub.1 and S.sub.2 to the top side O of the battery cell.

Method Example M2

[0228] Method Example M2 was carried out like Method Example M1, with the irradiation being carried out with the liner. Irradiation took place with a dose of 4 J/cm.sup.2 (UV-LED 365 nm, 4 s at 1000 mJ/cm.sup.2 s) and thereafter the liner was removed and the battery cell was clad as described in Method Example M1.

Method Example M3

[0229] Method Example M3 was carried out like Method Example M1, with the difference that the adhesive film was irradiated only after the complete cladding of the battery cell. In this case, a dose of greater than 5 J/cm.sup.2 (UV-LED 365 nm, 10 s at 1000 mJ/cm.sup.2 s on each side) was used in order to reach the regions in which the adhesive film has multiple plies, owing to folding operations and oversticking.

Method Example M4

[0230] A rectangular piece of a PET adhesive film with a crosslinkable adhesive layer was cut to shape and freed from the liner. The adhesive layer used was K3. The cladding of the battery cell was carried out in the following order: [0231] 1) bonding of the adhesive layer of the adhesive film with the bottom side U of the battery cell; [0232] 2) bonding of the adhesive layer of the adhesive film with the two large side walls S.sub.1 and S.sub.2; [0233] 3) bonding of the protrusion ?b.sub.3 on the bottom side U to the small side walls S.sub.3 and S.sub.4; [0234] 4) bonding of the lateral protrusion ?b.sub.2 to the small side walls S.sub.3 and S.sub.4; [0235] 5) bonding of the protrusion ?l.sub.2 of the small side walls S.sub.3 and S.sub.4 to the top side O of the battery cell; [0236] 6) bonding of the protrusion ?l.sub.3 of the large side walls S.sub.1 and S.sub.2 to the top side O of the battery cell.

[0237] Following the cladding of the battery cell, the adhesive film was exposed to thermal energy (20 minutes at 140? C.).

Method Example M5

[0238] Method Example M5 was carried out like Method Example M1, using adhesive layer K1.

COMPARATIVE METHOD EXAMPLES

Comparative Method Example CM1

[0239] A rectangular piece of a PET adhesive film with a crosslinkable adhesive layer was cut to shape and freed from the liner. The adhesive film was then irradiated with a dose of 4 J/cm.sup.2 using a Hoenle UV-LED 365 nm. The adhesive layer used was K2. The cladding of the battery cell was carried out in the following order: [0240] 1) bonding of the adhesive layer of the adhesive film with the bottom side U of the battery 25 cell; [0241] 2) bonding of the adhesive layer of the adhesive film with the two large side walls S.sub.1 and S.sub.2; [0242] 3) bonding of the lateral protrusion ?b.sub.2 to the small side walls S.sub.3 and S.sub.4; [0243] 4) bonding of the protrusion ?b.sub.3 on the bottom side U to the small side walls S.sub.3 and S.sub.4; [0244] 5) bonding of the protrusion ?l.sub.2 of the small side walls to the top side O of the battery cell; [0245] 6) bonding of the protrusion ?l.sub.3 of the large side walls to the top side O of the battery cell.

[0246] In CM1, in comparison to M1 -M5, the order of steps 3) and 4) is reversed.

Comparative Method Example CM2

[0247] A rectangular piece of a PET adhesive film with a crosslinkable adhesive layer was cut to shape and freed from the liner. The adhesive film was then irradiated with a dose of 4 J/cm.sup.2 using a Hoenle UV-LED 365 nm. The adhesive layer used was K2. The cladding of the battery cell was carried out in the following order: [0248] 1) bonding of the adhesive layer of the adhesive film with the bottom side U of the battery cell; [0249] 2) bonding of the adhesive layer of the adhesive film with the two large side walls S.sub.1 and S.sub.2; [0250] 3) bonding of the lateral protrusion ?b.sub.2 to the small side walls S.sub.3 and S.sub.4; [0251] 4) bonding of the protrusion ?b.sub.3 on the bottom side U to the small side walls S.sub.3 and S.sub.4; [0252] 5) bonding of the protrusion ?l.sub.3 of the large side walls to the top side O of the battery cell; [0253] 6) bonding of the protrusion ?l.sub.2 of the small side walls to the top side O of the battery cell.

[0254] In CM2, in comparison to M1-M5, the order of steps 3) and 4) and of steps 5) and 6) is reversed.

[0255] The results of the cladding of the battery cell according to Method Examples M1 -M5 and Comparative Method Examples CM1-CM2 are summarized in Table 3.

TABLE-US-00003 TABLE 3 Method Examples M1-M5 and Comparative Method Examples CM1-CM2 M1 M2 M3 M4 M5 CM1 CM2 Adhesive layer K2 K2 K2 K3 K1 K2 K2 Infiltration test at 85? C./85% rh + + + + + ? ? Pass: + Fail: ?

Infiltration Test

[0256] In order to evaluate the bonding quality, a battery cell wrapped with insulating adhesive tape was stored for 1000 h in a conditioned chamber at 85? C. and 85% relative humidity (rh). The test was passed if after this time there was no edge lifting of any bond. Failure is if the insulating adhesive tape at at least one point (frequently in the region of the folds) detached and so stood at a distance from the cell.

[0257] Using bonding method M1, the adhesive films were also bonded with the adhesive layers K1 and V1 and evaluated. With K1, a sufficient bond strength of more than 4 MPa was achieved and the infiltration test was passed. Comparative Example V1 is a commercial pressure-sensitive adhesive, tesa? 58353, which lacks sufficient bond strength to serve as a bonding basis for further liquid adhesives. While Examples V2 and V3 are distinguished by high bond strengths after curing, they are too soft, owing to absence of solid epoxy resins and too low a polymer fraction, respectively, giving the adhesive layer too low a cohesion, this being manifested in the uncured state by cohesive failure in the peel adhesion test. Such soft adhesives are less suitable for the method claimed, since on the one hand, owing to their low cohesion, they tend to emerge from the side of the wound adhesive tape rolls, causing the rolls to stick, and on the other hand, on bonding around edges, the restoring force of the carrier film may lead to edge lifting or detachment of the film. In Comparative Method CM1, the folded connection at the small side walls S.sub.3 and S.sub.4, which was bonded in step 4), parted. In Comparative Method CM2, the edges of the small side walls of the top side, which was bonded in step 6), parted.