WO2022009225A1

WO2022009225A1 - A battery pack

Info

Publication number: WO2022009225A1
Application number: PCT/IN2021/050659
Authority: WO
Inventors: Subbiah Senthilnathan; Dhinagar Samraj Jabez; Vinay Chandrakanth HARNE; Thangarajan SIVANESASELVAM
Original assignee: Tvs Motor Company Limited
Priority date: 2020-07-08
Filing date: 2021-07-07
Publication date: 2022-01-13
Also published as: CN115989611A

Abstract

The present subject matter relates generally to provide a closely packed battery having a plurality of partition structure arranged to separate a plurality of cell units 208. The plurality of partition structure includes a first partition structure 201 and a second partition structure 211 being adapted to prevent flame propagation to the other cell unit of the battery pack 100. The first partition structure 201 is placed between a cell module 202 and the second partition structure 211 is placed on a top and a bottom portion of the closely packed cell module 202 in the battery pack. This configuration prevents the propagation of flame from one cell unit 208 to another cell unit 208 and restricts the flames within the battery pack 100 keeping the vehicle and the rider of the vehicle safe.

Description

A BATTERY PACK

TECHNICAL FIELD

[0001] The present subject matter relates generally to a battery pack structure and more particularly but not exclusively to a fire proof battery pack structure. BACKGROUND

[0002] Rechargeable Batteries for example lithium ion batteries and lead acid batteries are commonly used in portable electronics and in many automobile applications. Due to better power efficiency and life expectancy, lithium ion batteries are preferred for said portable electronics and in many automobile applications. In automobile industry, the lithium ion batteries are used for fulfilling power requirements for electrical components and for assisting in engine cranking operation. In addition, lithium ion batteries are widely used in automobile sector to provide traction power to an electric or hybrid electric vehicles.

[0003] The lithium ion battery includes a number of lithium ion cells. Each lithium ion cell includes an anode, a cathode and a separator submerged in a solvent that acts as an electrolyte. The separator separates the anode and the cathode but permits the lithium ions to pass through it. Multiple lithium ion cells are placed in a cell holder which is further enclosed in a housing. The housing as well as the cell holder of the battery pack is generally made of a thermoplastic material. [0004] With better efficiency of the li-ion cells, design challenges related to high temperature arise and sometimes excess temperature rise may ignite flame in the lithium ion cell with extreme high temperature. The thermoplastic cell holder used in lithium ion batteries are not capable of retarding the flame propagation sufficiently from one cell module to another cell module. Expansion of flames within the battery pack results in excess pressure generation in the battery pack. The excess pressure built up inside the battery pack results in deformation of the battery pack and malfunction. Many lithium ion batteries are provided with a sacrificial member, which melts down and creates a space between the two cell modules but this does not ensure the arrest of propagation of flames to other modules effectively. In some events, pressure created inside the battery pack may lead to explosion, which may be life threatening for the user of the automobile.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The details are described with reference to an embodiment of a battery pack along with the accompanying figures. The same numbers are used throughout the drawings to reference similar features and components. Figure 1 exemplarily illustrates a battery pack. [0006] Figure 2 exemplarily illustrates an exploded view of the battery pack and its components.

[0007] Figure 3 exemplarily illustrates an exploded view of the essential parts of the battery pack.

[0008] Figure 4 exemplarily illustrates a corrugated first partition structure. [0009] Figure 5 exemplarily illustrates an exploded view of packaging of cell modules within the battery pack.

[00010] Figure 6 exemplarily illustrates a horizontally exploded view of the battery pack.

[00011] Figure 7 exemplarily illustrates an exploded view of a second partition structure along with the battery pack.

[00012] Figure 8 exemplarily illustrates an exploded view of the second partition structure having an insert structure and a plurality of supporting structure.

[00013] Figure 9 exemplarily illustrates another possible embodiment having an insert structure.

DETAILED DESCRIPTION

[0001] To prevent expansion of flame in the lithium ion batteries, few lithium ion batteries use a high temperature insulating material which adds extra cost to the battery. In addition, packaging of large number of the lithium ion cells in the battery pack in a limited space is a challenging task as it requires the cell holders, the separators, and the cell modules to be dimensionally stable, mechanically robust and impact resistance over a wide temperature range so that it is able to retard the flame propagation in the battery pack. Also, a closely packed cell in the battery pack requires a reduction of space and cost for fulfilling the packaging requirement. The above-mentioned problems are very critical and therefore, should be mitigated for the safety and health of the battery pack. Therefore, there is a need of an improved design of a compact battery pack for a device which is safe, secure and stable from thermal runaway effects and overcomes all of the problems cited above as well as other problems of known art.

[0002] As per an aspect of the present subject matter, in order to provide a secure and closely packed battery, the battery pack is configured with at least a plurality of partition structure configured to separate a plurality of cell units, the plurality of partition structure includes at least a first partition structure and at least a substantially orthogonally disposed second partition structure being adapted to prevent flame propagation to the other cell unit of the battery pack.

[0003] Additionally, embodiment of the present subject matter is to provide at least a first partition structure which is adapted to vertically separate the plurality of cell units, and at least a second partition structure adapted to horizontally separate the cell module from a battery housing cover. The cell module is disposed in the cell module holder forming a plurality of rows, at least a first partition structure is disposed vertically between the plurality of rows. The at least first partitions structure is disposed between the plurality of rows where the shape of the cell unit conforms to the longitudinal surface profile or shape of each cell in the plurality of cell units in the cell module.

[0004] Another embodiment of the present subject matter has a corrugated first partition structure which acts as a partition structure having compact packaging of the cell module as it occupies less space compared to other partition structures. Unlike other partition structures, the corrugation provided on the first partition structure adds rigidity and strength to the first partition structure, and enables the structure to occupy an interstitial space between the cell units. The flexible nature of the first partition structure helps it in easily adjusting between the cell units. The partition structure disposed between the two cell unit in the battery pack is made up of a metal such as stainless steel. The first partition structure acts as a wall and thus restricts the flame propagation to the other cell units within the battery pack. In comparison to the thermoplastics used in conventional battery packs to arrest the flame propagation, stainless steel is very stable in nature and has very good flexibility. Stainless steel has a very high melting point which helps in withstanding a higher flame temperature and also restricts the propagation of flame within the cell module.

[0005] According to another embodiment of the present subject matter, the thickness of the first partition structure made up of stainless-steel lies in the range of 0.2 mm - 2 mm. This thickness provides a compact packaging of the first structure without compromising the properties of the first partition structure, its rigidity and strength for the purpose of retarding the flame within in the battery pack.

[0006] According to another embodiment of the present subject matter, a plurality of the second partition structure is disposed on atop portion and on a bottom portion of said cell module. The second partition structure is adapted to locally restrict the flames inside the battery pack and thus acts as a wall placed on the top and the bottom portion of the battery pack. In the present embodiment, the second partition structure includes plurality of stainless-steel insert moulded with a plurality of supporting structure on both sides of the insert structure. The insert structure is made up of stainless-steel having poor thermal conductivity, high melting point and high tensile strength. Said insert structure is provided with metal profiles so as to maintain the stiffness and strength of the insert structure and restricts it from bending. However, the insert structure can be made up of any material exhibiting poor thermal conductivity, high melting point and high tensile strength. For the purposes of maintaining strength, rigidity and life of the insert structure, a plurality of elevated surface is formed on the surface of the insert structure on both the sides. The elevated surface so formed around a centrally disposed cavity is designed with a rectangular shape with rounded ends placed in the center of the insert structure. However, the centrally disposed cavity can be of different shapes depending on the structure of the cell module.

[0007] According to another embodiment of the present subject matter, the insert structure is moulded with the plurality of supporting structures on both sides of the insert structure to prevent it from making any electrical contacts with the terminals of the plurality of cell modules, thus safeguarding the battery pack from short circuit. Said plurality of supporting structure is made up of plastic material. The supporting structure can be made up of any insulating material having high dielectric strength instead of plastic. The plurality of supporting structure includes a plurality of projections similar to that of a comb to support the insert structure. In the present embodiment, four supporting structure are placed at the comers of the insert structure, said plurality of projections are facing to the center of the insert structure.

[0008] According to yet another embodiment of the present subject matter, the battery pack may have a cell to cell partition structure with a plurality of stainless- steel cell profde conforming sheet to prevent the propagation of flame between the cell module.

[0009] According to yet another embodiment of the present subject matter, the plastic structure is assembled on the cell module for insulation and then the metal sheet is assembled on the top of the plastic structure by means of a glue or hot sealing. In another embodiment, instead of adding a second partition structure, the thickness of the housing is increased or the material of the housing is changed so that the flame is restricted inside the housing. The embodiments of the present invention will now be described in detail with reference to an embodiment in the battery pack in an electric vehicle along with the accompanying drawings. However, the present invention is not limited to the present embodiment. The present subject matter is further described with reference to accompanying figures. It should be noted that the description and figures merely illustrate principles of the present subject matter. Various arrangements may be devised that, although not explicitly described or shown herein, encompass the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.

[00010] Fig. 1 exemplarily illustrates perspective view of a battery pack 100 having a lithium ion cell module (not shown) used in an electric vehicle. The present configuration is applicable to any battery pack 100 having a cell module (not shown). The battery pack 100 is enclosed in a battery housing cover 101, which is a box like structure, preferably having at least six sides of a housing. The battery housing cover 101 can be a rectangle or a square in shape. Fig. 2 exemplarily illustrates an exploded perspective view of the lithium ion battery 200. The Lithium ion battery 200 (hereinafter battery) includes a cell module holder 203, a cell module 202, a plurality of partition structures (201,211) disposed inside the battery housing cover 101, a rear housing cover 206, and a front housing cover 205. [00011] The cell module holder 203 accommodates the cell module 202. The cell module holder 203 includes an upper part and a lower part such that the cell module 202 is disposed sandwiched between the two part. The upper part and the lower part are provided with a plurality of slots (not shown) to accommodate each cell from the cell module 202 to form a closely packed cell cluster arranged either in series, or in parallel to each other or in zig zag manner. However, configurations of the cell module 202 are not limited to above-mentioned structure and can have many other configurations.

[00012] The plurality of partition structures is configured in the battery 200 in such a manner so as to separate said cell units 208 from each other in a secure way for preventing propagation of potential fire inside the battery. The plurality of partition structure includes at least a first partition structure 201 and at least a second partition structure 211. The at least a first partition structure 201 is adapted to vertically separate or isolate the cell module 202, and the at least a second partition structure 211 is adapted to horizontally separate or isolate the cell module 202 from the battery housing cover 101. The plurality of cell module 202 is disposed in the cell module holder 203 forming a plurality of rows, the at least a first partition structure 201 is disposed vertically interspaced between the plurality of rows in the interstitial space. The at least first partitions structure 201 is disposed between the plurality of rows conforming to the shape of each cell in the cell module 202. The cell module holder 203, the cell module 202, the second partition structure 211 and the first partition structure 201 are closely packed in a layout and is disposed inside the battery housing cover 101. A rear part of the battery housing cover 101 is closed by the battery rear housing cover 206. The rear housing cover 206 is a mesh like structure (not shown) provided for allowing cooling air from the atmosphere inside the battery pack 200. This is done to keep the temperature of the battery pack 200 from rising by providing cooling by natural means. A front part of the battery pack 200 is provided with a board having other electrical connections (not shown) necessary for the operation of the battery pack 200. These components are essential for connecting the battery pack 100 to an external terminal (not shown) for delivering electricity from the battery pack 100. The front part of the battery pack 200 along with the board having electrical connections is further covered by the front housing cover 205 in order to secure and package the whole battery pack 200 in one part.

[00013] Fig. 3 exemplarily illustrates an exploded perspective view of few essential parts of the battery pack 100. The cell module holder 203 holds the cells of the cell module 202 and ensures that the cell module 202 are closely packed. This compact packaging reduces the size of the battery pack (not shown) which is utmost important in the electric vehicles and addresses the problem of a space constraint. The cell module 202 are configured within the cell module holder 203 to effectively be disposed in the interstitial space present in the cell module holder 203. These cell module 202 are connected electrically to produce the power required for the traction of the electric vehicle (not shown). The first partition structure 201 is disposed between the two adjacent cell unit 208 for arresting the propagation of flames from one cell unit to another cell unit. This first partition structure 201 acts as a wall between said cell units 208. The first partition structure 201 is disposed between the available interstitial spaces between the two cell units 208 ensuring the compactness of the battery pack 100. In case of an accident or an undesirable impact on the battery 100, if one cell unit 208 gets affected due to thermal runaway, fire or a short circuit, these impacts are not transmitted to another cell unit 208 due to the placement of the first partition structure 201. The first partition structures 201 hold the impact in that cell unit 208 where the impact had started and does not allow an excess of pressure to be build up in the battery pack 100. This excess pressure if gets build up inside the battery pack 100, may damage the entire battery 100 or even result in a blast or fire. So, the first partition structure 201 is a very crucial element in the battery pack 100 from safety point of view. As per another aspect, the guiding of the cell module 202 also provides stability for each of the cell unit 208 to withstand undesirable vibrations or shock loads.

[00014] Fig. 4 exemplarily illustrates perspective view of one corrugated sheet of the first partition structure 201. The first partition structure 201 is made up of stainless-steel. Stainless-steel provides rigidity and strength to the first partition structure 201 required to act as safe and secure wall between the two cell units (not shown) within the battery pack (not shown). Stainless steel is very stable in nature and has very good flexibility which facilitates placement of the first partition structure 201 in between the cell units (not shown). As stainless steel has a very high melting point, it can withstand very high flame temperature and thus does not melts in case of thermal runaway or fire, thereby restricting the propagation of flame effectively to other cell unit (not shown). In addition, stainless steel has very low thermal conductivity which ensures that no heat or flame is conducted in the neighboring cell unit (not shown). The thickness of each sheet of the first partition structure 201 made up of stainless-steel lies in the range of 0.2 mm to 2 mm used in the electric vehicle. This thickness may vary according to the application of the battery pack (not shown). This thickness provides the compact packaging of the battery pack (not shown) along with the first partition structure 201 without compromising the properties of first partition structure 201 made up of stainless- steel having rigidity and strength. However, the first partition structure 201 can be made up of any metal having high melting point, high tensile strength, and poor thermal conductivity.

[00015] The first partition structure 201 as shown in fig. 4 has corrugated surface on both the edges of the structure, when viewed from the side of the first partition structure 201. These corrugations are provided to ensure the separation of one cell unit (not shown) with another cell unit (not shown) and allowing no contact between the two cell units (not shown) and still maintain the compactness of the battery pack (not shown). Instead of having individual partition to each cell of the battery 100, one single sheet of corrugated first partition structure 201 serves the purpose of restricting the flame propagation disposed between each cell unit. This also reduces the overall cost of the battery pack (not shown). The corrugated part of the first partition structure 201 provides flexibility while placing the structure 201 within the interstitial spaces easily.

[00016] Fig. 5 exemplarily illustrates an exploded perspective view of packaging of cell module 202 within the battery pack. The present configuration of the individual cell unit 208 in the battery (not shown) is shown in the figure 5. The individual cells 209 are placed in a line to form the cell unit 208. Similar cell units 208 are formed and placed parallelly to each other in order to make the cell module 202 of the battery pack (not shown). The corrugated first partition structure 201 is placed adjacent after every cell unit 208 in order to separate each unit 208 from one another. The width of the first partition structure 201 is same as that the height of individual cell 209 of the battery pack (not shown) and the length of the first partition structure 201 is same as that of the length of the cell unit 208. This is to ensure a proper shielding of one cell unit 208 from the other cell unit 208 thus ensuring the complete safety of the battery pack (not shown).

[00017] Fig.6 exemplarily illustrates a horizontally exploded perspective view of the battery pack (not shown). The battery pack (not shown) having a battery set 210 which includes the cell module (not shown) having the plurality of cells (not shown) forming the plurality of cell units (not shown), the cell module holder (not shown), first partition structure (not shown), and the second partition structure (not shown). Said battery pack (not shown) further includes the battery set 210, the battery housing casing 101 to cover a top portion, a bottom portion, and the sides of the battery set 210. The rear part of the battery set 210 is closed by the battery rear housing cover 206. The front part of the battery set 210 is covered by the front housing cover 205 in order to secure and package the whole battery pack (not shown) in one part. [00018] Fig. 7 exemplarily illustrates an exploded perspective view of a plurality of second partition structure 211 along with the battery set 210 wherein the second partition structure 211 consists of a top portion and a bottom portion. The cell module 202 (not shown in this fig.) in the battery pack (not shown) are connected in either series or parallel and the electrical connection are taken out from a pair of terminals (not shown).The second partition structure 211 is placed on the top portion and the bottom portion of the cell module (not shown) in the battery set

210 to ensure that the flame propagation within the battery set 210 do not escape the battery pack (not shown). This is done to contain the flame within the battery pack (not shown) in case of any accident, fire or thermal runaway. This is to also ensure that no excess pressure is built up, resulting in explosion, which can damage the battery (not shown) and may even injure the person from the explosion or fire while riding the vehicle. The second partition structure 211 is placed on the top and the bottom portion of the battery set 210 by means of a plurality of snap fits 217 This provides ease of assembly and secures the second partition structure 211 on the battery set 210. However, other means of mounting i.e. fastening, bonding, gluing, welding etc. can also be employed to mount the second partition structure

211 on said battery set 210.

[00019] Fig. 8 exemplarily illustrates an exploded perspective view of the second partition structure 211 having an insert structure 212, a plurality of supporting structure 213, a plurality of elevated surfaces 215, a cavity 218, and a plurality of projections 216. The insert structure 212 acts as a wall and thus restricts the flame from the top and the bottom portion of the battery set (not shown) from coming out of the battery pack (not shown). The insert structure 212 is made up of stainless- steel material having high tensile strength, high melting point, and poor thermal conductivity which helps the insert structure 212 to stop the flame or thermal runaway from propagating out of the battery pack (not shown). However, any metal having above-mentioned properties can be used as a metal part in the second partition structure 211. In addition to this, the insert structure 212 has the plurality of elevated surface 215 formed around the cavity 218 having a rectangular shape with rounded ends placed in the center of the insert structure 212 on both sides of its surface which prevents the bending of the insert structure 212 and maintains the stiffness of the insert structure 212. Since the insert structure 212 is a metal, it conducts electricity. The insert structure 212 when comes in contact with the terminals of the cell module (not shown) may result in a short circuit. In order to prevent the short circuit in the battery pack (not shown), the plurality of supporting structure 213 made up of plastic is provided on both the sides of the insert structure 212. The supporting structure 213 being an insulator acts as a wall between the insert structure 212 and the terminals. The supporting structure 213 as per an embodiment is moulded on the insert structure 212 to form a second partition structure 211. As per another embodiment, the supporting structure 213 is enmoulded on the insert structure 212.The supporting structure 213 is enmoulded on both the sides of the insert structure 212. Instead of placing a single integrated supporting structure, the plurality of supporting structure 213 is placed in proximity to the comers of the insert structure 212, in the present embodiment four plastic structure 213 are placed at the comers of the insert structure 212 facing the center of the insert structure 212. The plurality of supporting structure 213 includes the plurality of projections 216 similar to that of a comb to support the insert structure 212. Also, any insulating material having high dielectric strength can be used in place of plastic material to provide insulation, strength, and stiffness to the second partition structure 211.

[00020] Fig. 9 shows other possible embodiment having a stainless-steel sheet to retard the propagation of flames. In the embodiment, as shown in fig.9, a plastic structure 219 is assembled on the cell module (not shown) for insulation and then the insert stmcture 212 made of stainless steel is assembled on the top of the plastic structure 219 by means of a glue or hot sealing to hold the plastic stmcture 219 with the insert stmcture 212 together. In another embodiment, instead of adding a second partition stmcture (not shown), the thickness of the housing (not shown) is increased or the material of the housing (not shown) is changed so that the flame is restricted inside the housing (not shown). Many other improvements and modifications may be incorporated herein without deviating from the scope of the invention. List of Reference numerals:

100: Battery pack 101: Battery housing cover 200: Exploded view of lithium ion battery 201: First partition structure 202: Cell module 203: Cell module holder 205 : Battery front housing cover 206: Battery rear housing cover 208: Single cell unit 209: Single cell

210: Battery set 211: Second partition structure 212: insert structure 213: plurality of supporting structure 215: plurality of metal profdes

216: plurality of projections 217: snap fit 218: Cavity 219: Plastic structure

Claims

We claim:

1. A battery pack (100) for a powered device, comprising: a plurality of cells (209) forming a cell module (202); a cell module holder (203) for holding said cell module (202); and at least a plurality of partition structure (201, 211) configured to separate said cells (209) of cell module (202), the plurality of partition structure (201, 211) includes at least a first partition structure (201) and at least a substantially orthogonally disposed second partition structure (211) being adapted to prevent flame propagation to the other cell module of the battery pack (100).

2. The battery pack (100) as claimed in claim 1, wherein the at least a first partition structure (201) is adapted to vertically isolate the plurality of cell units (208), and the at least a second partition structure (211) is adapted to horizontally isolate the cell module (202) from a battery housing cover

(101).

3. The battery pack (100) as claimed in claim 1, wherein the plurality of cell units (208) are disposed in the cell module holder (203) forming a plurality of rows, the at least a first partition structure (201) is disposed vertically between the plurality of rows.

4. The battery pack (100) as claimed in claim 1, wherein the at least first partition structure (201) is disposed between the plurality of rows wherein the shape of the cell unit (208) conforms to the longitudinal surface profile or shape of each cell (209) in the plurality of cell units (208) of the cell module (202).

5. The battery pack (100) as claimed in claim 1, wherein said first partition structure (201) has a thickness in a range of 0.2 mm to 2 mm.

6. The battery pack (100) as claimed in claim 1, wherein said second partition structure (211) comprises of a top portion and a bottom portion to guide said cell module (202), the second partition structure (211) being adapted to locally restrict flames inside said battery pack (100).

7. The battery pack (100) as claimed in claim 6, wherein said second partition structure (211) includes a plurality of insert structure (212) which is moulded with a plurality of supporting structure (213) on both sides of the plurality of insert structure (212). 8. The battery pack (100) as claimed in claim 7, wherein the insert structure

(212) is made of stainless steel.

9. The battery pack (100) as claimed in claim 7, wherein said plurality of insert structure (212) is provided with a plurality of elevated surfaces (215) formed around a centrally disposed cavity (218) having a rectangular shape with rounded ends placed in the centre of the insert structure (212) to maintain stiffness of the insert structure (212).

10. The battery pack (100) as claimed in claim 7, wherein the plurality of supporting structure (213) having a plurality of projections (216) to support the insert structure (212). 11. The battery pack (100) as claimed in claim 1, wherein said battery pack

(100) includes a cell to cell partition with the first partition structure (201) having a plurality of cell profile conforming sheet (201) to prevent propagation of flame between said plurality of cells (209) of cell module (202).