VEHICLE BATTERY CELL VENTILATION SYSTEM

Abstract

A vehicle battery cell venting system includes a battery pack that provides electrical power for propelling a vehicle. A battery cell includes a battery casing enclosing components comprising an electrolyte. A battery end cap retains an electrolyte portion. A mandrel has a longitudinal bore, the mandrel extending through the electrolyte and disposed on a battery can centerline. Electrolyte-generated gas can pass through the longitudinal bore. A stem is slidably disposed within the longitudinal bore, with a stem proximally attached to a vent cap portion of the battery end cap.A circular notch in the battery end cap releasably attaches the vent cap portion to the battery end cap and is frangible, allowing the vent cap portion to separate from the battery end cap and the vent cap portion to displace along with the stem when a battery cell over-pressurization condition is created.

Description

INTRODUCTION

[0001] The present disclosure relates to batteries for electric vehicles and battery venting. Reference is made to US 2003 / 0 118 892 A1 and DE 10 2013 016 668 A1 as prior art.

[0002] In automotive batteries, hot gases and particles (emissions) are vented as heat spreads. To aid battery thermal management, vent caps can be used to allow and direct gas and particle exhaust into the battery's vents. Vent diverters have been developed for battery vent passages to direct the hot gas and exhaust, but the vent passage diverters can interfere with the operation of the vent caps.

[0003] Thus, while current systems and methods for diverting battery gas discharges serve their purpose, there is a need for a new and improved system and method for venting gas and exhaust from a battery cell of a vehicle battery pack. SUMMARY

[0004] The present invention is defined by the features of the appended independent claim 1. Advantageous further developments are specified in the following description and in the dependent claims.

[0005] In accordance with several aspects, a vehicle battery cell venting system includes a vehicle including a battery pack that provides electrical power for powering and operating systems of the vehicle.

[0006] A battery cell of the battery pack includes an outer battery can enclosing components of the battery cell, which includes an electrolyte disposed within the battery can. A battery end cap retains a portion of the electrolyte. A tubular mandrel has a longitudinal bore extending through the mandrel, the mandrel extending through the electrolyte and disposed on a longitudinal central axis of the battery can. The mandrel allows a gas generated by the electrolyte to pass through the longitudinal bore. A stem is slidably disposed within the longitudinal bore of the mandrel, with a proximal portion of the stem being attached to a vent cap portion of the battery end cap. A circular notch formed in the battery end cap removably attaches the vent cap portion to the battery end cap.The circular notch is fragile, which allows the vent cap portion to separate from the battery end cap and displace the vent cap portion along with the stem when an overpressure condition is created in the battery cell.

[0007] In another aspect of the present disclosure, the longitudinal bore comprises a first bore having a first bore diameter A that opens into a second bore having a second bore diameter B, wherein the first bore diameter A is smaller than the second bore diameter B.

[0008] In another aspect of the present disclosure, the shank includes a main shank portion having a first shank diameter C; and the first shank diameter C is smaller than the first bore diameter A, thereby providing a sliding fit of the main shank portion within the first bore diameter A.

[0009] In another aspect of the present disclosure, the shaft includes a stop block having a block diameter D that is greater than the first bore diameter A of the longitudinal bore, the stop block being slidably disposed within the second bore.

[0010] In another aspect of the present disclosure, the second bore terminates at a shoulder; and the stop block slidably fits within the bore diameter B of the second bore, the stop block contacting the shoulder to terminate sliding movement of the shaft in a shaft sliding direction.

[0011] In another aspect of the present disclosure, a particulate trap positioned on the vent cap portion provides a surface viscosity or treatment defining a generally circular end wall raised above a surface of the vent cap portion to collect and capture particulates in an exhaust occurring during battery cell venting. The particulate trap defines one of a magnetic material that magnetically attracts and retains the exhaust particles, or a chemical or viscous material that retains the particles that come into direct contact with the particulate trap.

[0012] In another aspect of the present disclosure, a wedge-shaped element is created on the shaft; and a tapered outer surface of the wedge-shaped element contacts a correspondingly shaped, tapered inner surface created in the mandrel to stop movement of the shaft.

[0013] In another aspect of the present disclosure, a plurality of wedge-shaped elements extend inwardly from a mandrel inner wall, each individually comprising a tapered surface having a continuous, downwardly directed, diameter-reducing shape. The stem has an upwardly directed, tapered body that passes through the wedge-shaped elements when a pressure differential from the overpressure condition occurs to stop the movement of the stem against one of the wedge-shaped elements.

[0014] In another aspect of the present disclosure, the vent cap portion includes a plurality of concentric brushes or porous materials attached to a top surface of the vent cap portion. The gaps or pores are designed to receive and retain at least one particle entrained in a discharge occurring during battery cell venting.

[0015] In another aspect of the present disclosure, the vent cap portion is thinner at the vent cap center than at a vent cap perimeter, allowing the vent cap center to be more easily flexed upon contact with a gas discharged from the battery cell, the vent cap center forming a curved cup shape during flexion to enhance capture of ejection particles emitted by the battery cell. A surface treatment is provided for the vent cap portion to attract the ejection particles, the surface treatment defining at least one of a brush material and a porous material operable to attract and capture the ejection particles, the brush material and the porous material defining a high-temperature resistant polymer.

[0016] According to several aspects, a method for forming a venting system for vehicle battery cells comprises: rolling a positive electrode and a negative electrode on a separator to create a coil; inserting a hollow mandrel through a longitudinal central axis of the coil; connecting a lower insulator at a first end of the coil proximate the negative electrode; connecting an upper insulator at a second end of the coil opposite the negative electrode and proximate the positive electrode; slidably disposing the lower insulator with the coil in a can; mounting a cell top assembly defining a head over a positive terminal of the positive electrode and on the upper insulator; slidably inserting a stem into a longitudinal bore of a mandrel centrally positioned in the can, a portion of the stem extending beyond a lower end of the mandrel;End-welding the stem to a surface of a vent cap portion of a battery end cap; and sliding the battery end cap, with the stem welded to the vent cap portion, onto a first end of the can and securing the battery end cap to a perimeter of the first end of the can.

[0017] In another aspect of the present disclosure, the method further comprises adding an electrolyte to the head of the cell top assembly and compressing the cell top assembly containing the electrolyte at a second end of the can.

[0018] In another aspect of the present disclosure, the method further comprises: extending a support ring of the battery end cap circumferentially outward from the vent cap portion to provide a support surface for receiving a portion of the electrolyte; and encapsulating the portion of the electrolyte using a raised shoulder surrounding the support ring when the battery end cap is attached to the can.

[0019] In another aspect of the present disclosure, the method further comprises extending a positive terminal outwardly from the positive electrode and extending a negative terminal outwardly from the negative electrode.

[0020] In another aspect of the present disclosure, the method further comprises: creating a first bore diameter A in the longitudinal bore that opens into a second bore having a second bore diameter B, the first bore diameter A being less than the second bore diameter B; terminating the second bore at a shoulder; providing the shank with a main shank portion having a first shank diameter C and a stop block having a stop block diameter D; forming a first shank diameter C that is smaller than the first bore diameter A of the longitudinal bore to provide for a sliding fit of the main shank portion within the first bore diameter A;and positioning a stop block on the shaft having a stop block diameter D greater than the first bore diameter A such that the stop block slidably fits within the second bore diameter B of the longitudinal bore, the stop block contacting the shoulder to terminate the sliding movement of the shaft;

[0021] In another aspect of the present disclosure, the method further comprises: circumferentially welding the lower insulator to the first end of the winding; welding the lower insulator to the can after placing the lower insulator with the winding into the can; and welding the cell top assembly to the positive terminal of the positive electrode.

[0022] In another aspect of the present disclosure, the method further comprises creating a circular notch in the battery end cap, wherein the circular notch is frangible and allows the vent cap portion to separate from the battery end cap and displace the vent cap portion along with the stem when an overpressure condition is created in the battery cell.

[0023] According to several aspects, a method for venting a vehicle battery cell comprises: inserting a hollow mandrel through a longitudinal central axis of a winding; installing the winding in a can; slidingly inserting a stem into a longitudinal bore of a mandrel centrally positioned in the can, with a portion of the stem extending beyond a lower end of the mandrel; creating a circular frangible notch in a battery end cap to distinguish a vent cap portion of the battery end cap; end-welding the portion of the stem extending beyond the lower end of the mandrel to a surface of the vent cap portion of the battery end cap; creating a battery cell by attaching the battery end cap to one end of the can and introducing an electrolyte into the can;and breaking the circular frangible notch separating the vent cap portion from the battery end cap when an overpressure condition is created in the battery cell to allow the vent cap portion, together with the stem, to move away from the can to vent gas from the battery cell;

[0024] In another aspect of the present disclosure, the method further comprises: connecting a lower insulator at a first end of the winding proximate a negative electrode; and connecting an upper insulator at a second end of the winding opposite the negative electrode and proximate a positive electrode.

[0025] In another aspect of the present disclosure, the method further comprises: attaching a cell top assembly defining a head over a positive terminal of the positive electrode and on the top insulator; and sliding the battery end cap with the stem welded thereto onto a first end of the can and securing the battery end cap to a periphery of the first end of the can.

[0026] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. Fig. 1 is a schematic view of a front left of a vehicle having a vehicle battery cell venting system according to an exemplary embodiment; Fig. 2 is a partial cross-sectional elevation view of a battery cell of the battery cell venting system of Fig. 1; Fig. 3 is a schematic representation of steps for manufacturing the vehicle battery cell venting system of Fig. 1; Fig. 4 is a top perspective view of a vent cap portion of a battery end cap of the present disclosure in an initially assembled state, including a circular notch connecting the vent cap portion to a body of the battery end cap; Fig. 5 is a perspective top view of the battery end cap of Fig. 4 after the circular notch fracture and the vent cap section displacement; Fig. 6 is a cross-sectional view of a modified battery cell of the present disclosure having a particulate trap; Fig. 7 is a cross-sectional view of a modified battery cell of the present disclosure having a tapered vent cap stop member; Fig. 8 is a cross-sectional elevation view of a modified battery cell of the present disclosure having a raised edge vent cap portion and a particulate trap; Fig. 9 is a cross-sectional view of a modified battery cell of the present disclosure having a plurality of tapered vent cap stop members; Fig. 10 is a cross-sectional elevation view of a modified battery cell of the present disclosure having a vent cap stop system made of a melting phase change material; Fig. 11 is a cross-sectional elevation view of a modified battery cell of the present disclosure having a vent cap portion with a plurality of upwardly directed concentric rings for trapping particles; and Fig. 12 is a cross-sectional elevation view of a modified battery cell of the present disclosure having a deformable vent cap portion. DETAILED DESCRIPTION

[0028] The following description is merely exemplary and is not intended to limit the present disclosure, application, or uses.

[0029] With reference to Fig. 1, a vehicle battery cell venting system 10 is provided for a vehicle 12 having a battery pack 14 that provides electrical power for powering and operating a plurality of systems of the vehicle 12. The vehicle 12 may include a sedan, SUV, van, truck, or autonomous vehicle, collectively defining a battery electric vehicle, having a plurality of battery cells 16 of the battery pack 14. The vehicle 12 may also include an auxiliary power source 17, including a gasoline engine or a hydrogen fuel cell, to provide a portion of battery charging current or a portion of motive power to assist the battery pack 14 in propelling the vehicle 12.In several aspects, the battery cells 16 may include any configuration of battery cell geometry, including cylindrical cells and / or rectangular cells, with a cylindrical cell geometry shown for illustrative purposes only.

[0030] With reference to Fig. 2 and again on Fig. 1 comprises a single battery cell 16 forming a cylindrical battery cell, an outer battery casing 18 enclosing the components of the battery cell 16. An electrolyte 20 is disposed within the battery casing 18, with a portion of the electrolyte 20 being retained using a battery end cap 22. The battery end cap 22 can be coupled to the battery casing 18 using a weld 24 to seal the battery cell 16 from the atmosphere. A mandrel 26 has a longitudinal bore 56 extending in Fig. 3, which extends the entire length of the mandrel 26. The mandrel 26 extends through the electrolyte 20 and is arranged on a longitudinal central axis 28 of the battery can 18. The mandrel 26 allows gas causing an overpressure in the battery cell 16, generated by the electrolyte 20 during a thermal expansion event of the battery cell 16, to pass through the longitudinal bore 27.

[0031] A shaft 30 is slidably disposed within the longitudinal bore 27 of the mandrel 26. The shaft 30 includes a stop block 32 having a block diameter that is larger than a shaft diameter of the shaft 30. The block diameter of the stop block 32 and the shaft diameter of the shaft 30 are smaller than a longitudinal bore diameter of the mandrel 26 to allow sliding movement of the shaft 30 in the longitudinal bore 27 of the mandrel 26, as shown in Fig. 3. A proximal part of the shaft 30 is attached to a vent cap portion 34 of the battery end cap 22, as described with reference to Fig. 3. The vent cap portion 34 of the battery end cap 22 is releasably attached to the battery end cap 22 via a circular notch 36 in the battery end cap 22. The circular notch 36 is frangible, allowing the vent cap portion 34 to separate from the battery end cap 22 to displace the vent cap portion 34 along with the stem 30 in an exemplary downward direction 38 when an overpressure condition is created in the battery cell 16.

[0032] With reference to Fig. 3 and again on Fig. 1 and Fig. 2, a sequence of exemplary manufacturing steps for forming the battery cell 16 is illustrated. Initially, a positive electrode 40 is positioned proximal to a negative electrode 42. A separator 44 is provided, and the positive electrode 40 and the negative electrode 42 are rolled or folded and thereby wound with the separator 44 to create a winding 46. The winding 46 may include a positive terminal 47 extending outwardly from the positive electrode 40 and a negative terminal 48 extending outwardly from the negative electrode 42. The hollow mandrel 26 is then, as in Fig. 2, is inserted through the longitudinal central axis 28 of the winding 46. A lower insulator 50 is then connected to a first end of the winding 46 proximal to the negative electrode 42. Similarly, an upper insulator 52 is then connected to a second end of the winding 46 opposite the negative electrode 42 and proximal to the positive electrode 40.

[0033] The lower insulator 50 is then circumferentially welded to the first end of the winding 46, and the lower insulator 50 is slidably disposed together with the winding 46 in the can 18. The lower insulator 50 is also further welded to the can 18. A cell top assembly 54 forming a head is mounted over the positive terminal 47 of the positive electrode 40 and onto the upper insulator 52. The cell top assembly 54 is then welded to the positive terminal 47 of the positive electrode 40 extending out of the second end of the can 18. The cell top assembly described with reference to Fig. 2 is added to the head of the cell top assembly 54, and the cell top assembly 54 containing the electrolyte 20 is circumferentially crimped to the second end of the can 18.

[0034] The shaft 30 is slidably inserted into the longitudinal bore 56 of the mandrel 26 positioned centrally in the can 18. The longitudinal bore 56 has a first bore diameter A and opens into a second bore 58 having a second bore diameter B. In several aspects, the first bore diameter A is less than the second bore diameter B. The second bore 58 terminates in a shoulder 60. The shaft 30 includes a main shaft portion 62 having a first shaft diameter C, and the stop block 32 has a stop block diameter D. In several aspects, the first shaft diameter C is less than the first bore diameter A of the longitudinal bore 56 such that the main shaft portion 62 slidably fits within the first bore diameter A.In several aspects, the stop block diameter D is larger than the first bore diameter A, such that the stop block 32 only fits slidably within the second bore diameter B of the longitudinal bore 56. The stop block 32 contacts the shoulder 60 to terminate the sliding movement of the shaft 30 in a shaft sliding direction 64.

[0035] A portion 66 of the stem 30 extending beyond a lower end 68 of the mandrel 26 is welded to a surface 70 of the vent cap portion 34 of the battery end cap 22. A support ring 72 of the battery end cap 22 extends circumferentially outward from the vent cap portion 34 and forms a support surface for receiving a portion of the electrolyte 20. A raised shoulder 74 surrounding the support ring 72 encapsulates a portion of the electrolyte 20 when the battery end cap 22 is secured to the can 18. The battery end cap 22, having the stem 30 welded thereto, is then slid onto a bottom or first end 76 of the can 18 and, using the method described with reference to Fig. 2 is welded circumferentially to a periphery of the first end 76 of the can 18 to complete the manufacture of the battery cell 16.

[0036] With reference to Fig. 4 and again on Fig. 1 to 3, in an assembly 78 comprising the battery end cap 22, the mandrel 26, and the stem 30, the vent cap portion 34 is releasably secured to the support ring 72 using the notch 36. The notch 36 provides a pressure-tight 360-degree seal of the vent cap portion 34 to the support ring 72 to seal the electrolyte 20 and the internal features of the battery cell 16 from the atmosphere under normal operating conditions of the battery cell 16. A weld 80 secures the stem 30 to the surface 70 of the vent cap portion 34, as described above with reference to Fig. 3. The stop block 32 is positioned above and does not contact the shoulder 60 in this initial design state of the assembly 78, so that the vent cap portion 34 can be displaced away from the support ring 72 if a subsequent high-pressure condition, such as a battery thermal expansion event, occurs during later operation of the battery cell 16.

[0037] With reference to Fig. 5 and again on Fig. 4, under predetermined operating conditions of the battery cell 16, including an internal overpressure within the battery cell caused, for example, by thermal expansion of the battery, the gas pressure within the battery cell 16 acting in the downward direction 64 causes the rupture of a frangible 360-degree seal provided by the intact notch 36. This allows the vent cap portion 34 to move away from the support ring 72 in the downward direction 64 as a convex-shaped peripheral edge 82 of the vent cap portion 34 separates from a concave-shaped peripheral wall 84 of the support ring 72. As the vent cap portion 34 separates from the support ring 72, a vent pathway 86 is opened to allow battery gases and exhaust to escape from the battery cell 16.The displacement of the vent cap portion 34 in the downward direction 64 is stopped when the stop block 32 comes into direct contact with the shoulder 60, thereby holding the vent path 86 open without allowing the vent cap portion 34 to become dislodged and contact and potentially damage any portion of the battery pack 14. The length of the portion 66 of the shaft 30 that extends beyond the lower end 68 of the mandrel 26, as shown in FIG. Fig. 3, is therefore selected so that the vent path 86 is maximally open and the vent cap section 34 is held by the stop block 32.

[0038] With reference to Fig. 6 and again on Fig. 3-5, in further aspects, a battery cell 87 is modified from the battery cell 16 to further maximize the capture of discharge exiting the battery cell 87. A particulate trap 88 provides a surface viscosity or treatment defining a generally circular end wall raised above a surface 90 of a modified vent cap portion 34' to collect and capture particulates 92 in the discharge encountered during battery cell venting. The particulate trap 88 may be made of a magnetic material to magnetically attract and retain the discharge particles 92, or a chemical or viscous material to capture the particles 92 that come into direct contact with the particulate trap 88.The particulate trap 88 can be positioned and retained on the surface 90 of the modified vent cap portion 34' using a raised end wall 94 of the modified vent cap portion 34'. The raised end wall 94 allows an outer surface 96 of the modified vent cap portion 34' to be machined or modified to perform the function of the notch 36 when the modified vent cap portion 34' separates from the concave-shaped peripheral wall 84 of the support ring 72. The battery cell gases can then fully exit the battery cell 16 via the flow paths 98, 98'. Similar to the above discussion of . Fig. 5, a length of the portion 66' of the shaft 30 extending beyond the lower end 68 of the mandrel 26 is defined as described with reference to Fig. 3, is selected to provide maximum opening for the flow paths 98, 98' while allowing the modified vent cap portion 34' to be retained by the stop block 32.

[0039] With reference to Fig. 7 and again on Fig. 3 through 6, a battery cell 99 is modified from battery cell 16 to improve the positioning of the vent cap during gas venting from battery cell 99. As an alternative to using stop block 32, the stem tip shape is designed to pass through a wedge channel when a pressure differential occurs due to thermal expansion ejection. One means of retaining a modified vent cap portion 34" is provided by a wedge-shaped member 100 formed on a modified stem 102. A tapered outer surface 104 of wedge-shaped member 100 contacts a similarly shaped tapered inner surface 106 of a modified mandrel 108 to stop movement of the modified stem 102 in the downward direction 64 after the circular notch 36 is broken.The further attachment and functions of a modified vent cap portion 34" are similar to the previously described designs of the vent cap portions 34, 34'. The tapered geometry of the wedge-shaped member 100 provides an additional advantage over the stop block 32. In the event that the battery pack 14 is inverted and upside down, the wedge geometry ensures frictional contact of the wedge-shaped member 100 with the tapered surface 106, maintaining the modified vent cap portion 34" in the open position for gas venting even in the inverted state.

[0040] With reference to Fig. 8 and again on Fig. 6, a battery cell 109 is modified from battery cell 16 according to further aspects to further maximize the containment of exhaust escaping from battery cell 109. To further maximize the containment of exhaust escaping from battery cell 16 from the vent gas and exhaust expelled from battery cell 16 when thermal expansion of battery cell 16 occurs, a vent cap portion 110 of vent cap portions 34, 34', 34" is modified to provide a particulate trap 112 having a surface viscosity or treatment defining a generally circular area 114 elevated above an area 116 of vent cap portion 110 to collect and capture particulates 118 escaping from battery cell 16 in the exhaust during battery cell venting.An additional end wall 120 on an outer periphery of the vent cap portion 110 includes a surface 122 raised above the particle trap 112 to further capture the particles 118.

[0041] With reference to Fig. 9 and again on Fig. 6 and Fig. 8, in further aspects, a battery cell 123 is modified from battery cell 16 to improve vent cap positioning upon gas escaping from battery cell 123. As an alternative to using stop block 32, a mandrel 124 includes a plurality of wedge-shaped elements 126a, 126b, 126c, 126d, 126e, 126f extending inwardly from a mandrel inner wall 128. Each of the wedge-shaped elements 126a, 126b, 126c, 126d, 126e, 126f has a tapered surface 130 with a continuous, downwardly tapered shape. A shaft 132 is modified from shaft 30 to include an upwardly directed tapered body 134 that passes through the wedge-shaped elements 126a, 126b, 126c, 126d, 126e, 126f when a pressure differential from the thermal expansion ejection occurs and the shaft 132 pushes in the downward direction 64.Multiple positions of the tapered body 134, and thus the stem 132, are permitted for different retention positions of a modified vent cap portion 34''', since a tapered surface 136 of the tapered body 134 contacts successive wedge-shaped elements 126a, 126b, 126c, 126d, 126e, 126f. The mandrel 124 and the stem 132 are both coaxially aligned with a longitudinal central axis 138 of the battery cell 123.

[0042] With continued reference to Fig. 9 are further features of a modified vent cap section 34''' similar to the previous vent cap sections 34, 34', 34'' designs described above. The tapered geometries of the wedge-shaped elements 126a, 126b, 126c, 126d, 126e, 126f and the tapered body 134 provide an additional advantage over the stop block 32. In the event that the battery cell 123 is inverted and upside down, the wedge geometry provides frictional contact of one of the wedge-shaped elements 126a, 126b, 126c, 126d, 126e, 126f with the tapered surface 136 of the tapered body 134 to maintain the modified vent cap portion 34''' in the open position for gas venting even in the inverted state.

[0043] With reference to Fig. 10, in further aspects, a battery cell 140 is modified from the battery cell 16 to modify the vent cap positioning during gas venting from the battery cell 140. A mandrel 142 is hollow and is positioned in the center of the battery cell 140, which has an inner wall 144. As an alternative to using the shoulder 60, the mandrel 142 includes a single wedge-shaped member 145 extending inwardly from a mandrel inner wall 144 and having an upwardly directed contact surface 146. The wedge-shaped member 145 also includes a tapered surface 148 constructed with a continuous, upwardly directed, diameter-reducing shape oriented opposite the geometry of the wedge-shaped members 126a, 126b, 126c, 126d, 126e, 126f described with reference to Fig. 9. A molten phase change material 150 is initially positioned within a bore of the mandrel 142 and beneath a stop surface 152 of the stop block 32. A single direction of movement of the stem 30 in the downward direction 64 is initiated when the molten phase change material 150 contacts the battery cell gas expelled during a thermal expansion event, melting the molten phase change material 150. The stem 30 and the vent cap portion 34 translate in the downward direction 64 until the stop surface 152 of the stop block 32 contacts the contact surface 146.

[0044] With reference to Fig. 11, in further aspects, a battery cell 154 is modified from the battery cell 16 to modify vent cap positioning during gas venting from the battery cell 154. The vent cap portion 34''' is modified to include a plurality of upwardly directed porous materials or wires 156 attached to a top surface 158 of the vent cap portion 34'''. A gap 160 is provided between successive concentric wires 156 that opens in an upward direction 162. The gap 160 is sized to receive and retain at least one, and in several aspects, a plurality of, particles 164 entrained in the exhaust resulting from venting the battery cell 154. The gap 160 may be less than or equal to approximately 100 µm.

[0045] With reference to Fig.12, in further aspects, a battery cell 166 is modified from the battery cell 16 to provide a modified vent cap portion 168 such that the vent cap portion 168 is thinner at a vent cap center 170 than at a vent cap perimeter 172, thereby allowing the vent cap center 170 to be more easily flexed upon contact by a gas discharged from the battery cell 166. During flexion, the vent cap center 170 forms a curved cup shape to enhance the collection of the ejected particles 174. A surface treatment 176 may be provided for the vent cap portion 168 to attract ejected particles 174. The surface treatment 176 may, for example, define a brush material or a porous material that attracts and traps the particles 174. The brush material or porous material is made of soft but high temperature resistant polymers.A surface treatment 178 may also be provided to enhance roughness to further enhance particle retention. The curved shell shape and surface treatment 176 help contain the particles 174 and prevent them from being ejected into a head 180 that receives the gas discharged from the battery cell 166.

[0046] A vehicle battery cell venting system 10 of the present disclosure offers several advantages. These include integrating a diverter into a battery cell. A vent is connected to a stop block through the mandrel. When the vent opens, the vent cap rises to a predefined height. The vent cap serves as a deflector and a particulate trap. The vehicle battery cell venting system 10 thereby prevents thermal and mechanical damage to the battery module and / or battery pack structure.

Claims

[1] Vehicle battery cell venting system (10), comprising: a vehicle (12) including a battery pack (14) that provides electrical power for powering and operating systems of the vehicle (12); a battery cell (16) of the battery pack (14) comprising an outer battery can (18) enclosing components of the battery cell (16) comprising an electrolyte (20) disposed within the battery can (18); a battery end cap (22) holding a portion of the electrolyte (20); a mandrel (26) having a longitudinal bore (56) extending through the mandrel (26), the mandrel (26) extending through the electrolyte (20) and being disposed on a longitudinal central axis of the battery can (18), the mandrel (26) allowing a gas generated by the electrolyte (20) to pass through the longitudinal bore (56); and a shaft (30) slidably disposed within the longitudinal bore (56) of the mandrel (26), a proximal end of the shaft (30) being secured to a vent cap portion (34) of the battery end cap (22); and a circular notch (36) formed in the battery end cap (22) and releasably securing the vent cap portion (34) to the battery end cap (22), the circular notch (36) being frangible and allowing the vent cap portion (34) to separate from the battery end cap (22) and displace the vent cap portion (34) together with the stem (30) when an overpressure condition is created in the battery cell (16). [2] The vehicle battery cell venting system (10) of claim 1, wherein the longitudinal bore (56) comprises a first bore having a first bore diameter A opening into a second bore (58) having a second bore diameter B, the first bore diameter A being smaller than the second bore diameter B. [3] Vehicle battery cell venting system (10) according to claim 2, wherein: the shaft (30) comprises a main shaft portion (62) having a first shaft diameter C; and the first shaft diameter C is smaller than the first bore diameter A, thereby providing a sliding fit of the main shaft portion (62) within the first bore diameter A. [4] The vehicle battery cell venting system (10) of claim 3, wherein the shaft (30) includes a stop block (32) having a block diameter D greater than the first bore diameter A of the longitudinal bore (56), the stop block (32) being slidably disposed within the second bore (58). [5] Vehicle battery cell venting system (10) according to claim 4, wherein: the second bore (58) ends at a shoulder (60); and the stop block (32) slidably fits within the second bore diameter B of the second bore (58), the stop block (32) contacting the shoulder (60) to terminate the sliding movement of the shaft (30) in a shaft sliding direction. [6] The vehicle battery cell venting system (10) of claim 1, further comprising a particulate trap (88) positioned on the vent cap portion (34) and providing a surface viscosity or treatment defining a generally circular end wall (94) raised above a surface of the vent cap portion (34) to collect and retain particulates of ejecta encountered during battery cell venting, the particulate trap (88) defining either a magnetic material to magnetically attract and retain the particulates of ejecta or a chemical or viscous material to retain the particulates of ejecta that come into direct contact with the particulate trap (88). [7] The vehicle battery cell venting system (10) of claim 1, further comprising: a wedge-shaped element formed on the shaft; and a tapered outer surface of the wedge-shaped member contacting a correspondingly shaped tapered inner surface formed in the mandrel to stop the movement of the shaft. [8] The vehicle battery cell venting system of claim 1, further comprising: a plurality of wedge-shaped elements (100) extending inwardly from a mandrel inner wall (106), each individually comprising a tapered surface (104) having a continuous, downwardly directed diameter-reducing shape; and wherein the shaft (132) has an upwardly directed, tapered body (134) which passes through the wedge-shaped elements (100) when a pressure differential from the overpressure condition occurs to stop the movement of the shaft (132) against one of the wedge-shaped elements (100). [9] Vehicle battery cell venting system (10) according to claim 1, wherein: the vent cap portion (34''') comprises a plurality of wires (156) attached to a top surface (158) of the vent cap portion (34'''); and a gap (160) provided between successive ones of the wires (156) in an upwardly directed opening, the gap receiving and retaining at least one particle entrained in an exhaust occurring during venting of the battery cell (154). [10] Vehicle battery cell venting system (10) according to claim 1, wherein: the vent cap portion (168) is thinner in the vent cap center (170) than at a vent cap periphery (172), whereby the vent cap center (170) can be more easily bent upon contact with a gas emitted by the battery cell (166), wherein the vent cap center (170) forms a curved bowl shape during the bending to improve the capture of the ejected particles (174) emitted by the battery cell (166); and a surface treatment (176) provided for the vent cap portion (168) to attract the ejection particles (174), the surface treatment defining at least one of a brush material and a porous material operable to attract and capture the ejection particles (174), the brush material and the porous material defining a high temperature resistant polymer.

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