Controlling the build-up of internal battery pressure in rechargeable batteries with a crushable insert layer

Abstract

Excessive expansion of rechargeable batteries during charging is a significant problem, as the uncontrolled build-up of high internal battery pressure due to expansion in a confined space can lead to separator membrane failure and / or thermal runaway of a battery cell. A crushable foam or honeycomb insert is placed within a rigid battery holder to automatically limit the progressive build-up of internal battery pressure due to charge-induced expansion of the battery cell during recharging. The crushable insert is part of the rigid battery holder. Aluminum honeycomb cores and porous aluminum metal foam materials are highly crushable over a very wide range of compressive loads. Alternatively, a porous metal foam or metal honeycomb material can be combined with a liquid polymer (e.g., elastomer).silicone, rubber, EPDM or polyurethane) are impregnated to improve the mechanical properties of the polymer-impregnated metal foam or honeycomb metal / polymer composite material.

Description

introduction

[0001] This disclosure relates to rechargeable batteries (e.g., lithium-ion or lithium-metal batteries) for use in electric vehicles or other electrically powered devices. A crushable insert layer is used to limit the build-up of internal pressure in a battery during charging.

[0002] Fig. Figure 1 shows a schematic representation of an example of battery internal pressure (MPa) as a function of the number of battery charge cycles for a lithium-ion battery enclosed in a rigid battery holder. An initial, minimal internal (compressive) battery pressure is advantageous when a lithium-ion battery is being charged or recharged. This initial compressive internal battery pressure can range from 14 to 120 psi (0.1–0.8 MPa). However, each time the battery cell is charged, it expands slightly (i.e., it swells), resulting in a net increase in the average internal battery pressure when the battery cell is enclosed in a rigid battery holder (i.e., in a case, can, enclosure, or between a pair of bolted rigid plates).The net increase in average internal battery pressure is due to irreversible electrochemical processes within the battery cell. For this reason, the average internal battery pressure continues to increase indefinitely with an increasing number of charge cycles. The pressure inside the battery can reach up to 1.6 MPa (240 psi) after several charge cycles, as shown in [reference missing]. Fig. Figure 1 is shown schematically. If the internal battery pressure exceeds a critical value, the battery can be damaged. Such damage can include the rupture of internal components, electrodes, and electrical connections, as well as the growth of internal dendrites on the separator membrane, which can lead to an electrical short circuit and subsequent thermal runaway (TR).

[0003] Therefore, a mechanical design is required that automatically limits and controls the build-up of internal battery pressure to an acceptable level by placing a crushable insert layer inside the outer mounting of the battery cell. Description

[0004] Excessive expansion of rechargeable batteries during charging is a significant problem, as the uncontrolled build-up of high internal battery pressure due to expansion in a confined space (e.g., a rigid battery holder) can lead to separator membrane failure and / or thermal runaway in a battery cell. In some embodiments, a crushable foam or honeycomb insert is placed within a battery holder to automatically limit the progressive build-up of internal battery pressure due to charging-induced cell expansion when the cell is enclosed in a rigid battery holder. The crushable insert is an integral part of the battery holder. A metal material with a honeycomb or porous metal foam structure exhibits high compressibility over a very wide range of compressive loads.

[0005] In some embodiments, a battery module comprises: a rigid battery holder; a battery cell enclosed within the rigid battery holder; and a crushable insert layer, which has a crush resistance and is arranged within the rigid battery holder adjacent to the battery cell. The crushable insert layer and the rigid battery holder are configured to limit the build-up of internal battery pressure within the battery cell during charging cycles to a value less than or equal to the crush resistance of the crushable insert layer.

[0006] In some embodiments, the crushable insert layer consists of a metal honeycomb material.

[0007] In some embodiments, the metal honeycomb material is an aluminum metal honeycomb material.

[0008] In some embodiments, the crushable insert layer consists of a porous metal foam material.

[0009] In some embodiments, the porous metal foam material is a porous metal foam material made of aluminum.

[0010] In some embodiments, the crushable insert layer has a breaking strength of 1 to 1.5 MPa.

[0011] In some embodiments, the crushable insert layer is infused with a polymer material to produce a polymer-infused crushable insert layer.

[0012] In some embodiments, the polymer-infused crushable insert layer has a surface, and the battery module also includes an additional layer with a polymer material arranged on the surface of the polymer-infused crushable insert layer.

[0013] In some embodiments, the polymer for the polymer-infused crushable insert layer is selected from silicone, silicone foam, polyurethane, polyurethane foam, EDPM, EDPM foam, rubber or rubber foam or combinations thereof.

[0014] In some embodiments, the battery module is a lithium-ion or lithium-metal battery module.

[0015] In some embodiments, the battery module further includes a polymeric intermediate layer located adjacent to the crushable insert layer and within the rigid battery holder.

[0016] In some embodiments, an electric motor vehicle comprises: a vehicle body with a passenger compartment; a plurality of wheels attached to the vehicle body; one or more traction motors attached to the vehicle body, which can be operated to drive one or more of the plurality of wheels to propel the electric motor vehicle; and a traction battery pack attached to the vehicle body and electrically connected to the one or more traction motors. The traction battery pack comprises a plurality of prismatic battery modules arranged in parallel rows; and each prismatic battery module comprises: a rigid battery holder; a battery cell enclosed in the rigid battery holder; and a crushable insert layer with a breaking strength arranged within the rigid battery holder adjacent to the battery cell.The crushable insert layer and the rigid battery holder are jointly configured to limit the build-up of internal battery pressure within the battery cell during charging cycles to a value that is less than or equal to the breaking strength of the crushable insert layer.

[0017] In some embodiments, a method for manufacturing a battery module comprises: providing a battery cell; providing a rigid battery holder; enclosing the battery cell in the rigid battery holder; and arranging a crushable insert layer with a tensile strength within the rigid battery holder adjacent to the battery cell. The crushable insert layer and the rigid battery holder are configured to interact such that they limit the build-up of internal battery pressure within the battery cell during charging cycles to a value less than or equal to the tensile strength of the crushable insert layer.

[0018] In some embodiments, the battery cell is a lithium-ion or lithium-metal battery cell, and the crushable insert layer is an aluminum honeycomb material or a porous metal foam made of aluminum. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a schematic representation of an example of the internal battery pressure as a function of the number of battery charge cycles for a lithium-ion battery cell housed in a rigid battery holder without a crushable insert layer, according to the present disclosure. Fig. Figure 2 shows a schematic representation of an example of the internal battery pressure as a function of the number of battery charge cycles for a lithium-ion battery cell housed in a rigid battery holder with a crushable insert layer according to the present disclosure. Fig. Figure 3A shows a schematic cross-sectional view through an example of a rechargeable battery cell with a pressure-limiting, crushable insert layer that is clamped between a pair of rigid plates prior to charging, according to the present disclosure. Fig. Figure 3B shows a schematic cross-sectional view through an example of a rechargeable battery cell with a pressure-limiting, crushable insert layer clamped between a pair of rigid mounting plates after it has undergone several charging cycles according to the present disclosure. Fig. Figure 4 shows perspective views of examples of various crushable aluminium honeycomb and aluminium metal foam materials according to the present disclosure. Fig. Figure 5 shows a schematic diagram of compressive stress and strain of an example of a generic crushable metal honeycomb core material that is subjected to permanent compression (i.e. crushing) and subsequent compaction according to the present disclosure. Fig. Figure 6 shows a schematic diagram of the compressive stress versus the strain of an example of a generic crushable porous metal foam material that is subjected to permanent compression (i.e. crushing) and subsequent compaction according to the present disclosure. Fig. Figure 7A shows a schematic cross-sectional view of an example of a crushable metal foam material infused with a polymer material (MFIP) according to the present disclosure. Fig. Figure 7B shows a schematic cross-sectional view of an example of a crushable metallic honeycomb material infused with a polymer material (MHIP) according to the present disclosure. Fig. Figure 8 shows a schematic, perspective view of an example of an electric vehicle with a rechargeable battery pack and a traction motor according to the present disclosure. Detailed description

[0019] Representative embodiments of the disclosure are illustrated in the drawings and are described in detail herein, whereby it is assumed that these embodiments serve as examples of the disclosed principles and do not represent limitations of the general aspects of the disclosure. Accordingly, elements and limitations described, for example, in the sections "Summary," "Introduction," "Description," and "Detailed Description," but not expressly set forth in the claims, should not be considered to be included in the claims, either individually or collectively, either by implication, by inference, or otherwise.

[0020] For the purposes of this detailed description, unless expressly excluded: the singular includes the plural and vice versa; the words "and" and "or" apply in both the subjunctive and disjunctive moods; the words "every" and "all" mean "every one and all"; and the words "including," "containing," "comprehensive," "exhibiting," and the like each mean "including without limitation." Furthermore, words of approximation such as "approximately," "almost," "essentially," "generally," "about," and the like may be used herein to mean "at, close to, or almost at" or "within 0-5% of" or "within acceptable manufacturing tolerances," or any logical combination thereof, for example.Finally, directional adjectives and adverbs such as "front", "stern", "inside", "outside", "starboard", "port", "vertical", "horizontal", "upwards", "downwards", "in front", "backwards", "left", "right", etc. can refer to a motor vehicle, e.g. to the forward movement of a motor vehicle when the vehicle is operated on a horizontal driving surface.

[0021] The terms "crustable" and "crustable" refer to the permanent deformation of a porous or honeycomb-shaped crushable material during compressive loading, resulting in permanent net deformation (i.e., "permanent hardening") after the compressive loading is removed. The terms "expansion" and "swelling" are used interchangeably, referring to what occurs during battery charging. The terms "layer" and "insert" are interchangeable, as they refer to a crushable insert layer. The terms "buildup" and "rise" are used interchangeably, as they refer to an increase in internal battery pressure when the battery is charged. The terms "honeycomb core" and "honeycomb matrix" are used interchangeably.

[0022] In some embodiments, the battery casing or battery box containing the rechargeable battery cell(s) may have a cylindrical or prismatic (e.g. rectangular) shape.

[0023] Fig. Figure 1 shows a schematic representation of an example of internal battery pressure (MPa) on the vertical axis 3 versus the number of battery charge cycles on the horizontal axis 2 for a rechargeable battery cell housed in a rigid battery holder (not shown). When charging or recharging a rechargeable battery, a low internal (compressive) pressure 4 is advantageous. This initial compressive internal battery pressure 4 might be, for example, between 14 and 120 psi (0.1–0.8 MPa). However, each time the rechargeable battery cell is charged, the cell expands slightly (i.e., it swells), causing the internal battery pressure to progressively increase during charging if the battery cell is enclosed in a rigid battery holder (e.g., a pair of rigid plates held by bolts).Due to irreversible electrochemical processes within the battery cell, there is a net increase in the average internal battery pressure 6. For this reason, the average internal battery pressure 6 continues to increase indefinitely with an increasing number of charge cycles. For example, after several charge cycles, the internal cell pressures can reach up to 1.6 MPa (240 psi). If the internal battery pressure 4 exceeds a critical value, the battery can be damaged. Such damage includes the rupture of internal components, electrodes, and electrical connections, as well as the growth of internal metal dendrites on the separator membrane, which can lead to a short circuit on the separator membrane and thermal runaway (TR).

[0024] Fig. Figure 2 shows a schematic representation of an example of the internal battery pressure on the vertical axis 3 with a crushable insert layer versus the number of battery charge cycles on the horizontal axis 2 for a rechargeable battery cell housed in a rigid battery holder with a crushable insert layer located inside the battery holder, according to the present disclosure. In this example, the limit for the crushing strength 11 is, for example, 1.2 MPa, which automatically limits the build-up of the internal battery pressure 4 during battery charging to less than or equal to the crushing strength limit of 1.2 MPa. The average internal battery pressure 6 is also limited by the use of a crushable insert layer.The expansion of the battery cell due to charging-induced swelling is balanced (i.e., buffered) by the simultaneous compression of the crushable insert layer. Note: This compression is a progressive process, as the deformation is permanent and therefore irreversible.

[0025] Fig. Figure 3A shows a schematic cross-sectional view through an example of a rechargeable battery cell 10 with a pressure-limiting crushable insert layer 14, which is clamped between a rigid battery holder with two rigid plates 16 and 18 before charging, according to the present disclosure. In this embodiment, the rechargeable battery cell 10 has a prismatic shape (e.g., rectangular) and is enclosed in a rigid battery holder 17 by a pair of parallel, rigid plates 16 and 18, which are rigidly held by a pair of screws 20 and nuts 22. Optionally, the rigid battery holder 17 can be replaced by a welded and / or extruded rigid battery case or battery can (not shown). Optionally, a polymeric intermediate layer 12 can be arranged within the rigid battery holder 17, adjacent to the battery cell 10 or adjacent to the crushable insert layer 14.The polymeric interlayer 12 can consist of silicone, silicone foam, polyurethane, polyurethane foam, EDPM, EDPM foam, rubber, or rubber foam, or combinations thereof, which helps to generate a uniform compressive pressure across the surface of the battery cell 10. Permanent deformation of the polymeric interlayer 12 can occur at a relatively low compressive stress of, for example, 0.3 MPa (40 psi) for silicone foam. Both the crushable insert layer 14 and the optional polymeric interlayer 12 can be arranged on the top of the battery cell 10, on the bottom of the battery cell 10, and / or on both sides of the battery cell 10.The crushable insert layer 14, the optional polymeric interlayer 12, and the rigid battery holder 17 are configured to limit the build-up of internal battery pressure within the battery cell during charging cycles to less than or equal to the breaking strength of the crushable insert layer 14. The thickness of the crushable insert layer 14 can range from 0.5 mm to 30 mm; it can be up to several centimeters thick (e.g., in a large battery pack). The crushable insert layer 14 can also act as a thermal conductor to dissipate heat from the battery cell 10.

[0026] Fig. Figure 3B shows a schematic cross-sectional view through an example of a rechargeable battery cell 10 with a pressure-limiting, crushable insert layer 14 clamped between two rigid plates 16 and 18 after it has undergone several charging cycles according to the present disclosure. In this embodiment, the rechargeable battery cell 10 has a prismatic shape (e.g., rectangular) and is enclosed in a rigid battery holder 17 by a pair of parallel, rigid plates 16 and 18, which are rigidly held by a pair of bolts 20 and nuts 22. The battery cell 10 has swollen due to charging and has expanded upwards (see upward-pointing arrows 8 and 8'). This electrochemical expansion of the battery cell 10 is automatically compensated by simultaneous compression of the crushable insert layer 14. Note: In Fig. In 3B, the operational shift 14 was compressed (compared to the one in Fig. 3A (thicker starting layer shown). The optional polymeric intermediate layer 12 is in Fig. 3B is also partially compressed due to the expansion of battery cell 10 during charging cycles.

[0027] Fig. Figure 4 shows various examples of different crushable aluminum honeycomb and aluminum foam materials according to the present disclosure. The pressure-limiting, crushable insert layer 14 can consist of a metal foam material 32 and 34 or a metal honeycomb material 30. In some embodiments, the materials used for the crushable insert layer 14 can be selected, for example, from aluminum, aluminum alloys, steel, nickel, copper, copper alloys, or polymers, or combinations thereof. Fig. Figure 4 shows examples of various porous aluminum structures, including: (a) an aluminum honeycomb core material 30; (b) a “CrushLite™” aluminum foil-based honeycomb material 32; and a porous aluminum foam material 34 (comprising a variety of aluminum web strips 36 and hollow pores 38). The CrushLite™ foil-based aluminum honeycomb material 32 has a breaking strength in the range of 8 to 750 psi (0.05 to 5 MPa), depending on the specific design (e.g., alloy composition, yield strength, pore size, cell geometry, and / or wall thickness, etc.).

[0028] Fig. Figure 5 shows a schematic stress-strain curve of an example of a generic crushable metal honeycomb core material that is subjected to permanent compression (i.e., crushing) and subsequent compaction according to the present disclosure. This stress-strain curve 28 shows the compressive strain on the x-axis 24 and the compressive stress on the y-axis 26. This representation shows a number of different regions for the overall stress-strain curve 28, including (a) an elastic region 40 at low strains (e.g., less than about 0.05 strain); (b) a crushing region 42 in which the honeycomb material is crushed (i.e., it buckles), thereby limiting the stress to no more than the breaking strength (e.g., 4 MPa).This is followed by (c) a compacted region 44 in which the honeycombs are finally completely crushed and compacted, resulting in a rapid increase in stress with a small additional strain in the compacted region 44.

[0029] Fig. Figure 6 shows a schematic stress-strain curve 28 of an example of a generic, crushable, porous metal foam material that is subjected to permanent compression and subsequent densification according to the present disclosure. This stress-strain curve 28 shows the compressive strain on the x-axis 24 and the compressive stress on the y-axis 26. The diagram shows a series of regions for the stress-strain curve 28, including (a) an elastic zone 40 at low strains (e.g., less than about 0.05 strain); (b) a crushing region 42 in which the porous foam material is crushed (thereby limiting the stress to no more than the limit of the breaking strength (e.g., 2-3 MPa); followed by (c) a compacted region 44 in which the porous metal foam material is finally completely crushed and compacted, showing a rapid increase in stress with a small additional strain in the compacted region 44.

[0030] Fig. Figure 7A shows a schematic cross-sectional view of an example of a crushable, porous metal foam material infused with a polymeric material, according to the present disclosure. In this embodiment, the crushable, polymer-infused foam material 66 comprises a crushable, porous metal foam matrix 60 (e.g., a porous scaffold) with a plurality of pores 62 distributed throughout the porous metal foam matrix 60. The porous metal foam matrix 60 is infused with a liquid polymer resin 64 to produce an MFIP composite material 66 comprising a crushable metal foam matrix 60 with polymer-filled pores 64.

[0031] Still with reference to Fig. As shown in Figure 7A, an optional top layer 68 made of the same or a similar polymer material can be applied to or arranged on one (or more) surface(s) of the MFIP material 66. The polymeric top layer 68 can help to ensure that a homogeneous pressure is applied evenly over the entire surface of the battery cell 10. The polymeric top layer 68 can be the same polymeric material used to infuse the porous metal foam matrix 60 to produce an MFIP material 66.

[0032] Fig. Figure 7B shows a schematic cross-sectional view of an example of a crushable metallic honeycomb material 90 infused with a polymer material 92 (MHIP 94) according to the present disclosure. The metallic honeycomb core material 90 is infused with liquid polymer resins 92 to produce a metallic honeycomb polymer-infused (MHIP) composite material 94. An optional top layer 96 of the same or a similar polymer material may be applied or arranged on one (or more) surface(s) of the MHIP material 94. The polymer top layer 96 may help to ensure that a homogeneous pressure is exerted uniformly over the entire surface of the battery cell 10. The optional polymer top layer 96 may be the same polymer material used to infuse the metal honeycomb matrix 90 to produce an MHIP material 94.

[0033] With reference to the Fig. 7A and Fig. 7B The mechanical properties (e.g., stress / strain curve, fracture toughness, etc.) of an MFIP material 66 or MHIP material 94 can be improved depending on the amount and type of polymer material incorporated into the porous foam or honeycomb matrix. Silicone, polyurethane, EPDM, rubber, or combinations thereof can be used as the polymer material incorporated into the MFIP material 66 or MHIP material 94.

[0034] Fig. Figure 8 shows a schematic perspective view of an example of an electric vehicle 72 with a rechargeable battery pack 80 according to the present disclosure. The electric vehicle 72 comprises a vehicle body 74, a passenger compartment 71 arranged within the vehicle body 74, a plurality of wheels 76, 76', etc., attached to the vehicle body 74, and a rechargeable battery pack 80 located inside the electric vehicle 72. The electric vehicle 72 further comprises one or more electric traction motors 82 attached to the vehicle body 74, which drive one or more of the wheels 76, 76', etc., which propel the electric vehicle 72. A rechargeable battery pack 80 is attached to the vehicle body 74. The battery pack 80 is electrically connected to the electric traction motor(s) 82 via a power cable 84.The battery pack 80 consists of a multitude of prismatic battery modules 86 arranged in parallel rows to each other.

[0035] In some embodiments, the Fig. 3A and Fig. The crushable insert layer 14 shown in 3B can also be used at the level of a battery module / battery pack.

[0036] While the best modes for carrying out the disclosure have been described in detail, those who are familiar with the prior art to which this disclosure relates will recognize various alternative designs and embodiments for carrying out the disclosure within the scope of the attached claims.

Claims

[1] Battery module, comprising: a rigid battery holder; a battery cell enclosed in the rigid battery holder; and a crushable insert layer having a crush resistance disposed inside the rigid battery holder adjacent the battery cell; wherein the crushable insert layer and the rigid battery support are cooperatively configured to limit the buildup of internal battery pressure within the battery cell during charging cycles to a value less than or equal to the crush strength of the crushable insert layer. [2] The battery module of claim 1, wherein the crushable insert layer comprises a metal honeycomb material. [3] The battery module of claim 2, wherein the metal honeycomb material comprises an aluminum metal honeycomb material. [4] The battery module of claim 1, wherein the crushable insert layer comprises a porous metal foam material. [5] The battery module according to claim 4, wherein the porous metal foam material comprises a porous metal foam material made of aluminum. [6] The battery module of claim 1, wherein the crushable insert layer has a crushing strength in the range of 1 to 1.5 MPa. [7] The battery module of claim 1, wherein the crushable insert layer is infused with a polymeric material to produce a polymer-infused crushable insert layer. [8] The battery module of claim 7, wherein the polymer-infused crushable insert layer has a surface; and wherein the battery module further comprises an additional layer comprising a polymeric material disposed on the surface of the polymer-infused crushable insert layer. [9] Battery module according to claim 7, wherein the polymeric material is selected from silicone, silicone foam, polyurethane, polyurethane foam, EDPM, EDPM foam, rubber, rubber foam or combinations thereof. [10] The battery module of claim 1, wherein the battery module comprises a lithium-ion or lithium metal battery module.

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