Heat-triggered primer and thermoset adhesive multilayer composition for disassembly of EV batteries

Abstract

A method can include detaching a battery attached to a substrate through a multi-layer composition, including: heating the multi-layer composition to a detachment temperature above 60 DEG C, the multi-layer composition including one or more thermoplastic primer layers having a transition temperature in the range of 60 DEG C to 120 DEG C and one or more thermoset adhesive layers; and separating one or more layers of the multilayer composition to detach the battery pack from the substrate, wherein the substrate has a surface energy of 35 dynes / cm or greater.

Description

Technical Field

[0001] Embodiments are directed to methods and systems including removable battery assemblies produced using thermally removable multi-layer adhesive compositions. Background Art

[0002] Thermoplastic adhesives and thermosetting adhesives are used in many industrial applications, including flexible packaging and mounting electric vehicle (EV) batteries. For most applications, thermosetting adhesives are selected based on bond strength, substrate compatibility, and long-term durability under operating conditions. However, for many applications, the attached components must be separated for component maintenance or replacement. In order to disassemble EV batteries bonded to a thermosetting adhesive layer, for example, physical removal methods such as prying, cutting, or laser ablation are typically used. Other methods involve the use of solvents or acids to remove thermosetting adhesives, which can create chemical hazards and can provide limited penetration into the adhesive layer. Another problem with common disassembly methods is the effectiveness of high surface area attachments, including those present in EV battery packs, which can result in damage to the attached components. Summary of the invention

[0003] The method disclosed herein may include detaching a battery cell attached to a substrate via a multilayer composition, comprising: heating the multilayer composition to a detachment temperature above 60°C, the multilayer composition comprising one or more thermoplastic primer layers having a transition temperature in the range of 60°C to 120°C and one or more thermosetting adhesive layers; and separating the one or more layers of the multilayer composition to detach the battery cell from the substrate, wherein the substrate has a surface energy of 35 dynes / cm or greater. DETAILED DESCRIPTION

[0004] Embodiments relate to methods and systems for removable battery assemblies produced with heat-removable multilayer adhesive compositions. Specifically, the methods include disassembling one or more components of a battery assembly comprising a multilayer composition by directional heating from a heat source (such as a thermal management plate). In some cases, a thermal management plate (e.g., a water cooling plate for an EV battery) can be used to heat the multilayer composition to a temperature above the transition temperature of one or more thermoplastic layers (e.g., 50°C to 130°C), which enables the thermoplastic primer layer to be automatically or mechanically assisted peeled from an attachment surface (e.g., a high surface energy substrate, a thermosetting adhesive layer, etc.) with minimal deformation or damage.

[0005] Electric vehicle battery designs typically include one or more battery packs containing multiple battery cells that are individually bonded to various types of substrates. EV batteries may also include a number of external features to protect the battery pack and array of battery cells, including multiple housings and substrates. Due to the large surface contact area of ​​the battery components (e.g., about 0.5 m2 for a battery pack block), the battery pack may be easily attached to the substrate. 2Up to 1.5m for the entire battery pack 2 ) and a wide operating temperature range (e.g., -20°C to 60°C), thermosetting adhesives are typically used to provide bonding strength between the battery and the underlying or overlying substrate and structure. However, the bonding strength of thermosetting adhesives makes it difficult to disassemble the battery pack or battery pack substrate without damaging or deforming the attached component.

[0006] The methods and systems disclosed herein relate to thermally removable multilayer compositions for removably fixing battery components (e.g., battery packs, battery cells) to various types of substrates. The multilayer composition may include one or more thermoplastic primer layers and one or more thermosetting adhesive layers, which are interspersed between two substrates, such as one or more battery cells and a battery substrate (e.g., a battery cover, a battery bottom, or a thermal management plate). The thermoplastic primer layer disclosed herein may melt or soften at elevated temperatures, which reduces the adhesive strength of the multilayer composition and enables the removal of one or more of the component layers.

[0007] The thermoplastic primer resin disclosed herein can be removably bonded to one or more of a thermosetting adhesive layer, a battery pack substrate, and / or a thermal management plate. For most applications, the thermoplastic primer layer can remain solid and maintain adhesive properties throughout the operating temperature (e.g., below or up to 50° C.), but above the glass transition temperature (T g ) or melting point temperature (T m ) softens and / or melts at a temperature of . The thermoplastic primer layer disclosed herein may have a glass transition temperature (T ) in the range of 60°C to 130°C, 60°C to 120°C, 60°C to 110°C, or 60°C to 90°C. g ).

[0008] A method of disassembling a battery pack attached to a substrate by a multilayer composition may include heating the multilayer composition to a "disassembly temperature" above 60°C to induce softening or melting of the thermoplastic primer layer, followed by separation of one or more layers of the multilayer composition to disassemble the battery pack from the substrate. The disassembly method may include mechanically separating the primer layer and / or adhesive layer from the substrate layer by suitable techniques such as prying, wedging and / or impacting. In some cases, gravity or other "passive" techniques can be used to separate one or more layers of the multilayer composition.

[0009] Applying heat to the multilayer composition may include using an external heat source (such as an electric heating platform, an electric heating pad, an electric heating sheet, an electric heating blanket, etc.) or an internal heat source (such as a thermal management plate, a thermal management pad, an embedded heating element, etc.). Thermal management plates are typically used to maintain EV batteries within a stable temperature range (e.g., between -20°C and 60°C). During operation, the thermal management plate operates to dissipate or supply heat to the EV battery through passive heat transfer (e.g., a heat sink) or active heat transfer (e.g., using a flowing fluid or gas). The methods disclosed herein may utilize a thermal management plate or other method to directly heat the primer layer and the adhesive layer to a disassembly temperature (i.e., above the transition temperature of the thermoplastic primer layer) while also minimizing heat transfer from the heat source to the battery pack and subsequent battery damage.

[0010] During heating and removal of the multilayer composition, the methods and systems can utilize direct heating of the multilayer composition to minimize the measured temperature of the battery pack. If the battery cells are directly bonded to the substrate (e.g., a thermal management plate in an EV battery pack), the substrate can serve as an internal heat source. If the battery cells are directly bonded to the battery pack substrate (e.g., the bottom or cover in an EV battery pack), the heat source can also be external, such as a thermal management platform / pad / blanket that contacts the multilayer composition. In either case, the use of an external heat source or an internal heat source produces an initial temperature increase at the contact site (e.g., a thermoplastic primer layer and / or a thermosetting adhesive layer), while the limitation of heat transfer results in delayed heating of more distant components (e.g., battery cells).

[0011] A series of finite element modeling experiments were conducted on a representative battery assembly comprising a battery pack, a multilayer composition, and an external thermal management plate. The experiments showed that heating by the thermal management plate resulted in localized heating within the multilayer composition, while the attached battery pack temperature was lower. Specifically, heating with a thermal management plate at a disassembly temperature of 100°C resulted in the temperature of the thermoplastic primer layer and the thermosetting adhesive layer increasing to as high as 80°C at 2 minutes, while the center of the battery pack reached 60°C at 15 minutes and 80°C at 30 minutes. Differential thermal measurements between the battery pack cells and the multilayer composition indicate that there is a window where the battery pack can be disassembled from the underlying battery assembly components (e.g., substrates such as battery pack bottoms, covers, etc.) during softening or melting of the thermoplastic primer layer and before exceeding the operable temperature limit. For example, battery disassembly may occur when the thermoplastic primer layer is at a disassembly temperature (e.g., 80°C or above) while the EV battery remains within its upper operable temperature limit, such as in the range of 60°C to 80°C.

[0012] The methods disclosed herein may include disassembling the battery when the measured battery temperature is at least 20° C., at least 10° C., or at least 5° C. below the disassembly temperature. In some cases, the method of disassembling a battery attached to a substrate via a multilayer composition may include disassembling the battery within 2 minutes to 45 minutes, 2 minutes to 30 minutes, or 2 minutes to 20 minutes after applying heat to the multilayer composition.

[0013] The multilayer composition may include a high surface energy substrate on which one or more thermoplastic primer layers and / or thermosetting adhesive layers are formed, applied or deposited. Examples of high surface energy substrates also include surfaces of battery components (e.g., battery packs or cell frames), substrate packages, thermal management plates, and other surfaces. The battery components disclosed herein may include EV battery packs and substrates, including prismatic or pouch-shaped cell-based batteries, cylindrical cell batteries, battery packs, and the like.

[0014] As used herein, "high surface energy substrate" refers to a substrate having a surface energy of 35 dynes / cm or greater. High surface energy substrates disclosed herein include metals (such as aluminum, steel or alloys, zinc, etc.), non-metals (including glass), polar polymers (such as epoxy, polyurethane or polyester), coated materials (such as epoxy-coated aluminum, polyacrylate-coated aluminum, polyester-lined aluminum, etc.). Table 1 includes other examples of suitable high energy substrates.

[0015]

[0016] In some cases, the high surface energy substrate may also be placed in contact with a multilayer composition comprising one or more thermoplastic primer layers and / or thermosetting adhesive layers assembled on a second substrate or surface. In some cases, the multilayer composition may comprise a thermoplastic primer layer contacting the high surface energy substrate and a thermosetting adhesive contacting the thermoplastic primer layer. The thermosetting adhesive may also mediate attachment to a second substrate such as a thermal management plate.

[0017] As another example, a multilayer composition can include a first thermoplastic primer layer contacting a high surface energy substrate and a thermosetting adhesive contacting the first thermoplastic primer layer. A second thermoplastic primer layer can contact the thermosetting material and mediate attachment to a second substrate.

[0018] The multilayer composition may include one or more thermosetting adhesive layers, which may include one or more polyurethanes, epoxies, polyacrylates, polyesters, cross-linked derivatives thereof, etc. The thermosetting adhesive may include a structural adhesive and / or a thermally conductive adhesive having a thermal conductivity of 0.2 W / mK or more, such as in the range of 0.2 W / mK to 3 W / mK. The thermosetting adhesives disclosed herein may be water-based, solvent-based, or solvent-free.

[0019] The multi-layer composition disclosed herein may include one or more thermoplastic primer layers including one or more thermoplastic polymers. The thermoplastic primer layer may include a maleic anhydride grafted chlorinated polyolefin (MAH-g-CPO) alone or a combination of a maleic anhydride grafted chlorinated polyolefin and one or more additional thermoplastic polymers. The maleic anhydride grafted chlorinated polyolefin disclosed herein may have a degree of chlorination of 10% to 30%, and / or at least one maleic anhydride modified polyolefin has a degree of chlorination of more than 1%. The maleic anhydride grafted chlorinated polyolefin disclosed herein may have a weight average molecular weight of more than 50,000Da, more than 60,000Da, or more than 70,000Da. The maleic anhydride grafted chlorinated polyolefin may have a weight average molecular weight in the range of 40,000Da to 100,000Da, 50,000Da to 90,000Da, or 50,000Da to 80,000Da.

[0020] The thermoplastic primer layer may comprise MAH-g-CPO in combination with one or more additional thermoplastic polymers including polyurethanes, polyesters, polyethers, polyacrylates, polycarbonates, maleic anhydride grafted polymers such as maleic anhydride grafted polyolefins (MAH-g-POE), maleic anhydride grafted ethylene-vinyl acetate (MAH-g-EVA), maleic anhydride grafted styrene-ethylene-butylene-styrene (MAH-g-SEBS), and the like. The thermoplastic primer layer may include one or more of polyolefins, ethylene vinyl acetate, acrylonitrile-butadiene rubber, butadiene-styrene rubber; tackifying resins (such as rosin, terpene and modified terpene), aliphatic, alicyclic and aromatic resins (e.g., C5 aliphatic resin, C9 aromatic resin and C5 / C9 aliphatic / aromatic resin), hydrogenated hydrocarbon resins, terpene-phenol resins, novolac resins, etc.; organic phase change materials (PCMs), such as hydrocarbons, paraffins (e.g., C5 aliphatic resins, C9 aromatic resins and C5 / C9 aliphatic / aromatic resins) with a phase transition temperature of 60° C. to 120° C.; n H 2n+2 ) and lipids; and a liquid crystal material having a phase change property in the temperature range of 60°C to 120°C; and the like.

[0021] In some cases, the polarity of the thermoplastic primer layer comprising MAH-g-CPO and one or more polar thermoplastic polymers can be adjusted to minimize changes in lap shear strength and cross tensile strength caused by incompatibility with the thermosetting adhesive layer. For example, the thermoplastic primer composition can be modified to include a polar resin (e.g., up to 45 wt%) to increase adhesion to polar thermosetting resins such as polyurethanes and epoxy resins.

[0022] Thermoplastic primer layers incorporating multiple polymers may include 55 wt% or more, 70 wt% or more, or 80 wt% or more of the MAH-g-CPO component by weight percentage (wt%). The thermoplastic primer layer may include MAH-g-CPO in the range of 55 wt% to 100 wt%, 60 wt% to 100 wt%, or 70 wt% to 100 wt% by weight percentage (wt%). Thermoplastic primer layers comprising a resin mixture may include MAH-g-CPO and one or more thermoplastic polymer components in the range of 0 wt% to 45 wt%, 0 wt% to 40 wt%, or 0 wt% to 30 wt% by weight percentage (wt%), with the balance being MAH-g-CPO and / or additives.

[0023] The thermoplastic primer layer can be applied to the adhesive layer and / or substrate layer as a solid, film, hot melt or powder (e.g., 100wt% solids). The thermoplastic primer layer can be generated by solvating the MAH-g-CPO resin (optionally utilizing one or more additional thermoplastic polymers) in a suitable solvent and depositing the resulting solvated resin composition on a substrate or surface. The solvent is then evaporated when the thermoplastic primer layer is formed. Suitable solvents can vary according to the solubility of the selected primer resin or resin mixture, and can include aqueous solvents or organic solvents. A mixture of non-polar organic solvents and polar organic solvents can be used. Non-polar solvents can include cycloalkyl or aromatic substances, such as methylcyclohexane, toluene, etc. Polar organic solvents can include methyl ethyl ketone, ethyl acetate, butyl acetate, etc.

[0024] The organic solvated resin composition may include one or more primer resins (e.g., solids) in a weight percentage (wt%) range of 1 wt% to 35 wt%, 1 wt% to 20 wt%, or 3 wt% to 20 wt%. The organic solvated resin composition may include a non-polar organic solvent in a weight percentage (wt%) range of 60 wt% to 99 wt%, 65 wt% to 99 wt%, or 70 wt% to 99 wt%. The organic solvated resin composition may include a polar organic solvent in a weight percentage (wt%) range of 1 wt% to 40 wt%, 1 wt% to 45 wt%, or 1 wt% to 30 wt%.

[0025] The water-based resin composition may include one or more primer resins in the range of 15 wt % to 65 wt %, 20 wt % to 60 wt %, or 30 wt % to 55 wt % by weight percentage (wt %). The water-based solvated resin composition may include an aqueous fluid in the range of 35 wt % to 85 wt %, 40 wt % to 80 wt %, or 45 wt % to 70 wt % by weight percentage (wt %).

[0026] The thermoplastic primer layer disclosed herein can maintain good bond strength relative to the bond between the adhesive layer and the substrate. The multi-layer composition disclosed herein can have a lap shear strength at room temperature that is less than 30% lower than a comparative multi-layer composition without a thermoplastic primer layer. The multi-layer composition disclosed herein can have a cross-tense strength at room temperature that is less than 30% lower than a comparative multi-layer composition without a thermoplastic primer layer.

[0027] The method of preparing the detachable multilayer composition disclosed herein may include providing a substrate surface, one or more thermoplastic primer layers and one or more thermosetting adhesive layers. The thermoplastic primer layer and the thermosetting adhesive layer may be prepared by solid deposition or by coating from a solvent composition using known methods such as roller coating, flow coating, dip coating, spin coating, spray coating, blade coating and extrusion coating. The multilayer composition disclosed herein may include a thermoplastic primer layer having a thickness in the range of 0.5 μm to 150 μm, 1 μm to 100 μm, or 5 μm to 90 μm.

[0028] Removing the substrate from the thermoplastic primer layer and / or the thermosetting adhesive layer may include heating the multilayer composition to a temperature equal to or greater than 60° C.; and removing at least one of the layers of the multilayer composition. The method of delivering heat may include internal heating or external heating. The internal heating source may include a heat management plate, resistive heating or induction heating, or other contact heating elements. The external heating source may include a heating platform, a heating plate or a heating table, a heating blanket or a heating sheet, a heat gun, steam, and the like.

[0029] The removal method may include heating the multilayer composition to a temperature above 60° C. and mechanically separating the primer layer and / or adhesive layer from the substrate layer by suitable techniques such as prying, wedging, and / or impacting.

[0030] The system may include a removable electric vehicle battery system comprising an electric vehicle battery; a multilayer composition that attaches the battery to a battery pack substrate, the multilayer composition comprising one or more thermoplastic primer layers having a transition temperature in the range of 60°C to 120°C and one or more thermosetting adhesive layers; a heat source in contact with the multilayer composition or as a layer thereof (e.g., the thermoplastic primer layer or the thermosetting adhesive layer is directly bonded to a thermal management plate or other heat source); and wherein the battery pack substrate is one or more of a battery pack bottom, a battery pack cover, or a heat source; wherein the heat source is configured to heat the multilayer composition to a removal temperature in the range of 60°C to 120°C to enable removal of the electric vehicle battery.

[0031] Example

[0032] The following examples are provided to illustrate embodiments of the present invention and are not intended to limit the scope of the present invention. Unless otherwise specified, all parts and percentages are by weight. The data and descriptive information provided herein are based on approximate values. Table 2 lists the materials used in the following examples:

[0033]

[0034] Embodiment 1: Disassembly method using a thermal management plate

[0035] In this example, a battery assembly was constructed using a sample multilayer composition to mediate attachment between a commercial battery and a thermal management plate. The bonded battery assembly was then tested for disassembly properties using the methods disclosed herein, wherein the multilayer composition is heated using a thermal management plate to soften or melt the adhesive layer and / or primer layer to facilitate disassembly.

[0036] The multilayer composition comprises the following layers as described in Table 3, wherein the structural elements are as follows: The "battery cell" comprises a commercial LiFePO4 having an epoxy-coated 3-type Al surface. 4 EV battery pack (dimensions: length / width / height = 172mm / 166mm / 52.1mm); "primer layer" includes MAH-g-CPO based primer with a thickness of about 13μm; "adhesive layer" includes a thermosetting polyurethane adhesive (thermal conductivity 0.3w / mK) and a thickness of about 1mm; "battery pack substrate" includes epoxy resin coated 5-type Al (5754) with a thickness of 2mm; "thermal management plate" includes a forced circulation thermal management plate capable of heating to 100°C.

[0037] The comparative examples (CE) and the inventive examples (IE) were bonded via a polyurethane thermosetting adhesive between the battery pack and the battery pack substrate. The thermoplastic primer layer used in the examples was produced by solubilizing primer resin particles of 7 parts MAH-g-CPO and 3 parts hydrogenated rosin in an 85:5 mixture of methylcyclohexane and methyl ethyl ketone. The resin particles were added to a flask with a solid content of 10 wt% and heated to 80°C with stirring until dissolved. The primer resin mixture was then applied to the battery pack or battery pack substrate before applying the thermosetting adhesive.

[0038] The disassembly test was carried out as follows. Step 1: Prepare the samples according to Table 3 and age for 1 week. Step 2: Place CE1 in a heating oven at 80°C for 30 minutes. Place the remaining samples on a preheated thermal management plate at 100°C for 5 minutes, which ensures that the temperature of the primer layer and the adhesive layer exceeds 80°C after 5 minutes of thermal transition. Step 3: With the help of a 21 cm long screwdriver, a disassembly test was performed manually between the high-temperature battery cell and the battery substrate. The tip of the screwdriver was placed between the battery pack and the battery pack substrate to pry open the layers. If the sample can be manually disassembled within 5 minutes, it is defined as "removable". If the sample cannot be manually disassembled within 5 minutes, it is defined as "non-removable". Similar tests can also be performed on the above samples at room temperature to check the performance at room temperature.

[0039]

[0040] Sample CE 1 is a multilayer composition with a thermosetting 2K PU adhesive without a primer, wherein the battery cell and the multilayer composition were heated in an oven under the same conditions at a removal temperature of 80°C for 30 minutes. Subsequent attempts to remove the battery cell from the battery pack substrate failed, indicating that the thermosetting 2k PU adhesive has good adhesion to the battery cell and the battery pack substrate even at high temperatures (80°C). CE2 is similar to CE1, but it is heated using a thermal management plate, however, the bonding strength of the thermosetting adhesive to the battery cell and the battery pack substrate remains strong after heating and attempts at removal fail. For the IE1 to IE3 embodiments with a thermoplastic primer layer, removal is facilitated by softening or melting the thermoplastic primer layer heated to 80°C (above the glass transition temperature of 70°C), thereby allowing removal by manual prying.

[0041] While the foregoing is directed to illustrative embodiments, other and further embodiments may be devised without departing from the basic scope of the present invention, which is defined by the claims that follow.

Claims

1. A method for disassembling a battery cell attached to a substrate by a multilayer composition, the method comprising: heating the multi-layer composition to a disassembly temperature above 60°C, the multi-layer composition comprising one or more thermoplastic primer layers having a transition temperature in the range of 60°C to 120°C and one or more thermosetting adhesive layers; and separating one or more layers of the multilayer composition to remove the battery cell from the substrate, wherein the substrate has a surface energy of 35 dynes / cm or greater.

2. The method of claim 1, wherein heating comprises heating the multilayer composition using a thermal management plate, pad, or blanket.

3. The method of claim 1, wherein heating comprises heating the multilayer composition using an internal thermal management system such as a water cooling plate.

4. The method of claim 1, wherein the one or more thermoplastic primer layers comprise 55 wt% to 100 wt% of the maleic anhydride grafted chlorinated polyolefin. The method of claim 1 , wherein disassembling comprises prying apart the multi-layer composition.

6. The method of claim 1 wherein the multi-layer composition comprises a thermoplastic primer layer in contact with the substrate. 7 . The method of claim 1 , wherein the multi-layer composition comprises a thermoplastic primer layer in contact with the battery cell.

8. The method of claim 1, wherein a battery cell temperature is at least 5°C lower than the disassembly temperature of the multi-layer composition.

9. A detachable electric vehicle battery system, the electric vehicle battery system comprising: Electric vehicle batteries; a multi-layer composition that attaches the battery to a battery substrate, the multi-layer composition comprising one or more thermoplastic primer layers having a transition temperature in the range of 60° C. to 120° C. and one or more thermosetting adhesive layers; a heat source in contact with the multi-layer composition or a layer of the multi-layer composition; and wherein the battery substrate is one or more of a battery bottom, a battery cover, or the heat source; wherein the heat source is configured to heat the multilayer composition to a disassembly temperature in a range of 60° C. to 120° C. to enable disassembly of the electric vehicle battery.

10. The system of claim 8, wherein the one or more thermoplastic primer layers comprise 55 wt% to 100 wt% of maleic anhydride grafted chlorinated polyolefin 11. The system of claim 8, wherein the heat source is a thermal management plate.

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