ELASTOMERIC SILICONE MATERIALS AND THEIR APPLICATIONS

Abstract

Disclosed is an article adapted to receive multiple battery cells, such as a battery module, which provides thermal insulation between adjacent battery cells using thermally insulating layers comprising a ceramifiable elastomeric silicone material using calcium silicate fillers such as wollastonite. There is also provided, the use of said ceramifiable elastomeric silicone material as a means of delaying and/or preventing thermal runaway in such an article. Typically, the battery cells for which this article is designed are lithium-ion battery cells.

Claims

1. An article adapted to receive multiple battery cells which provides thermal insulation between adjacent battery cells by the provision of a thermally insulating layer of a ceramifiable elastomeric silicone material between adjacent battery cells, which ceramifiable elastomeric silicone material is a cured product of a silicone rubber composition comprising: (i) one or more polydiorganosiloxanes having a weight average molecular weight of from 200,000 to 800.000_g/mol, having between 0.01 to 1_%_of alkenyl and/or alkynyl groups and present in an amount of from 30 to 70 %_wt. of the composition; (ii) a reinforcing silica filler present in an amount of from 5.0 to 22.0 %_wt. of the composition; (iii) calcium silicate filler having a particle size of from 1 to 30 .Math.m and present in an amount of from 20 to 70 %_wt. of the composition; (iv) a curing agent selected from: (a) an organic peroxide; or (b) a hydrosilylation cure package comprising; (b) (i) a hydrosilylation catalyst, and (b) (ii) an organopolysiloxane cross-linker having at least three hydrogen groups per molecule; and component (v) when curing agent (iv) is (a) an organic peroxide or optionally component (vi) when curing agent (iv) is (b) a hydrosilylation cure package; wherein: (v) is a platinum metal, or a compound or complex of a platinum group metal; and (vi) is a hydrosilylation cure inhibitor.

2. The article in accordance with claim 1, wherein the battery cells are lithium-ion battery cells.

3. The article in accordance with claim 1, having a battery module comprising a casing adapted to receive multiple battery cells and a thermally insulating layer of the ceramifiable elastomeric silicone material.

4. The article in accordance with claim 1, having a battery module comprising a casing, a plurality of battery cells and a thermally insulating layer of the ceramifiable elastomeric silicone material sandwiched between adjacent battery cells.

5. The article in accordance with claim 1, comprising a battery pack of at least one battery module.

6. The article in accordance with any preceding claim 1, wherein the calcium silicate filler (iii) is wollastonite.

7. The article in accordance with any preceding claim 1, wherein the thickness of the thermally insulating layer is between 0.2_mm and 4_cm.

8. A method for thermally insulating adjacent battery cells in an article designed to receive multiple battery cells by the provision of a thermally insulating layer of ceramifiable elastomeric silicone material between said adjacent battery cells, which ceramifiable elastomeric silicone material is a cured product of a silicone rubber composition comprising: (i) one or more polydiorganosiloxanes having a weight average molecular weight of from 200,000 to 800,000_g/mol, having between 0.01 to 1_%_of alkenyl and/or alkynyl groups and present in an amount of from 30 to 70%_wt. of the composition; (ii) a reinforcing silica filler present in an amount of from 5.0 to 22.0%_wt. of the composition; (iii) calcium silicate filler having a particle size of from 1 to 30 .Math.m and present in an amount of from 20 to 70%_wt. of the composition; (iv) a curing agent selected from: (a) an organic peroxide; or (b) a hydrosilylation cure package comprising; (b) (i) a hydrosilylation catalyst, and (b) (ii) an organopolysiloxane cross-linker having at least three hydrogen groups per molecule; and component (v) when curing agent (iv) is (a) an organic peroxide or optionally component (vi) when curing agent (iv) is (b) a hydrosilylation cure package; wherein: (v) is a platinum metal, or a compound or complex of a platinum group metal; and (vi) is a hydrosilylation cure inhibitor.

9. The method in accordance with claim 8, wherein the battery cells are lithium-ion battery cells.

10. The A-method in accordance with claim 8, wherein the calcium silicate filler (iii) is wollastonite.

11. (canceled)

12. (canceled)

13. (canceled)

14. The article in accordance with claim 1, wherein the thermally insulating layer prevents or delays the potential for thermal runaway propagation between adjacent battery cells.

15. The article in accordance with claim 1, used in or as an electric-vehicle battery power supply for electric and/or hybrid powered vehicles.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0156] The accompanying figures are included to provide further understanding, and to illustrate exemplary embodiments and, together with the description, serve to enhance the understanding of the disclosure herein. FIG. 1 is a representation of a battery module as described herein using prismatic shaped batteries, for the ease of explanation.

[0157] FIG. 2a is a photograph of a ceramified side of the thermally insulating layer as described herein after testing

[0158] FIG. 2b is a photograph of a non-ceramified side of the thermally insulating layer as described herein after testing showing it still has its elastomeric character.

[0159] In FIG. 1 there is provided a series of prismatic battery cells (1a - 1h) e.g. lithium-ion battery cells in a battery module with the outer casing not shown. Such modules may be used in power sources for driving electric vehicles and hybrid electric vehicles and the like as discussed above. Adjacent battery cells (1a-h) sandwich a corresponding thermally insulating layer (2a-g). Whilst not shown it will be understood that each battery comprises an anode, a cathode and electrolyte and may be any suitable battery cell. At each end of the row of alternating battery cells (1 a-h) and thermally insulating layers (2a-g) is provided a cell end plate (3). Whilst not shown in FIG. 1 the alternating prismatic battery cell (1a-h) and thermally insulating layers (2a-g) depicted are retained in a battery module casing. Positive electrode terminals are identified as (4) in FIG. 1. The battery cells (1a-h) are each electrically connected in series and/or in parallel as desired for the end purpose with the positive electrode terminal being electrically connected to a positive electrode plate through a positive electrode collector, and the negative electrode terminal is electrically connected to the negative electrode plate through a negative electrode collector. By providing the thermally insulating layers (2a-g) between adjacent battery cells the users of the article being powered or partially powered e.g. a vehicle are provided with a battery module designed for preventing thermal runaway propagation throughout the battery cells in the battery module using thermally insulating layers (2a-g).

[0160] In use, if, for example, battery cell (1d) were to malfunction and enter or approach thermal runaway, thermally insulating layers (2c) and (2d) partially ceramify and insulate battery cells (1c) and (1e) from the dramatic increase in temperature in battery cell (1d) and either delay or prevent the propagation of the thermal runaway phenomenon within the battery module.

[0161] FIG. 2a is a photo of a ceramified side of a thermal insulating layer test piece used in the examples and FIG. 2b shows the elastomeric surface of the depicts.

[0162] The following examples, illustrating the compositions and components of the compositions, elastomers, and methods, are intended to illustrate and not to limit the invention.

EXAMPLES

[0163] A series of examples (Ex. 1- Ex.7) and comparative examples (C.1 - C.4) were prepared by mixing all the components in the compositions detailed below. Silicone bases were initially prepared in accordance with Table 1 and then the bases were utilised as indicated to make the compositions in Tables 2a and 4a.

[0164] Unless otherwise indicated Mw was determined using Gel permeation chromatography (GPC), All viscosities were measured at 25° C. relying on the cup/spindle method of ASTM D 1084 Method B, with the most appropriate spindle from the Brookfield® RV or LV range for the viscosity range, unless otherwise indicated. The alkenyl and/or alkynyl and/or silicon bonded hydrogen (Si-H) content of the components was determined using quantitative infra-red analysis in accordance with ASTM E168.

[0165] The filler(s) and filler treating agent(s) were first mixed with and evenly dispersed into the silicone polymer gum(s) to form a silicone rubber base. When relying on an organo peroxide catalyst, the remaining components were then added and dispersed into the respective base and the final compositions were press cured for 10 minutes at a suitable temperature. In the case of 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane (DHBP) catalyst containing compositions the cure temperature used was 170° C. In the case of bis(2,4-Dichloro Benzoyl) Peroxide catalyst containing compositions the cure temperature used was 120° C. and likewise the platinum cured compositions were cured for 10 minutes at 120° C. Some samples were post cured for 8 hours at 200° C. When reliant on hydrosilylation cure the composition was prepared in two parts which were subsequently mixed together in a predetermined ratio shortly prior to use.

TABLE-US-00001 Silicone rubber bases used in examples Components Base A Base B Base C Dimethylvinyl terminated dimethyl polysiloxane gum having a Mw of about 500,000 g/mol and a vinyl content of 0.014 wt. % 36.91 68.0 29.76 Dimethylvinyl terminated dimethyl methylvinyl polysiloxane gum having a Mw of about 500,000 g/mol and a vinyl content of 0.065 wt. % 36.91 29.76 Dimethylvinyl terminated dimethyl methylvinyl polysiloxane, having a viscosity of 14,000 mPa.s and a vinyl content of 7.7 wt. % 1.8 Dimethylhydroxy terminated polydimethylsiloxane having a viscosity of about 45 mPa.s 7.0 6.0 Dimethylhydroxy terminated polydimethylsiloxane having a viscosity of about 15 mPa.s 4.0 Fumed silica having a BET surface area of approx. 250 m.sup.2/g 19.00 26.0 34.00 Methyl vinyl diol Dimethylhydroxy terminated polydimethylmethylvinylsiloxane viscosity of about 30 mPa.s at 25° C. and vinyl content of about 12.0 wt. % 0.180 0.2 0.480

[0166] The compositions used in the Examples are provided in Table 2a.

TABLE-US-00002 Compositions of Examples Ex.1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Base A 53.06 47.06 65.96 44.34 41.44 37.66 Base B 65.64 25.21 Wollastonite, 5 .Math.m 44 31.10 50.00 55.56 Wollastonite, 15 .Math.m 28.61 50.00 10.96 CaSiO.sub.3 (Chem reac.) 15 .Math.m 11.49 Quartz, 51 .Math.m 3.40 3.16 12.36 Pt solution 0.50 0.50 0.50 0.19 Cerium hydroxide masterbatch 0.35 1.0 1.00 1.00 1.00 1.00 1.13 DHBP masterbatch 1.00 1.00 DCBP masterbatch 1.50 1.50 Inhibitor masterbatch 0.14 0.14 0.14 SiH cross-linker masterbatch 0.9 0.9 0.9 Pt catalyst MB 0.9 0.9 0.9 100.00 100 100.00 100.00 100.00 100.00 100.00

[0167] In the above table: [0168] Pt solution is a Platinum catalyst in a solution of polydimethylsiloxane having about 5000 ppm of platinum metal with respect to the rest of the composition; [0169] Cerium hydroxide masterbatch is a 50 : 50 by weight masterbatch of cerium hydroxide in a polydimethylsiloxane polymer having a Mw of 500,000 g/mol’; [0170] DCBP masterbatch is a 50 : 50 by weight masterbatch of bis(2,4-Dichloro Benzoyl) Peroxide catalyst in polydimethylsiloxane polymer; [0171] DHBP masterbatch is a 50 : 50 by weight masterbatch of 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane catalyst in 40% Polydimethylsiloxane polymer and 10% silica; [0172] the quartz used was Min-u- sil® 5 .Math.m obtained from US Silica; [0173] the Si-H cross-linker is 83% by weight of an Si-H containing silicone resin having 6400 ppm of Si-H bonds and 17% of silica wherein the silica functions as a carrier; and Inhibitor masterbatch consists of 4.8% by weight of ethynyl-1-cyclohexanol (ETCH) in in a silicone rubber masterbatch.

TABLE-US-00003 The amounts of individual ingredients introduced as part of silicone rubber base A or B in Table 2a Key ingredients Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Vinyl-term PDMS polymer having a Mw of 500,000 and vi of 0.010% 44.56 19.63 17.41 24.4 16.41 15.33 31.07 Vinyl-term PDMS polymer having a Mw of 500,000 and vi of 0.065% 19.63 17.41 24.4 16.41 15.33 13.93 High vinyl PDMS polymer having a Mw of ~46,000 and vi of 7.7% 1.21 0.466 Cumulative wt. % of all Silicone polymers or fluids 51 45.43 40 55 38.71 36 52 Silica 17 10.5 9.4 13.04 8.85 8.32 13.86

[0174] Physical property results for the respective compositions/ elastomers are shown, together with the test methods used, in Tables 3a and 3b with respect to the Examples.

TABLE-US-00004 Physical property results of examples Test Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex.6 Ex. 7 Shore A Durometer (ASTM D2240 -15) 68 75 69 64 85 85 79 Specific gravity (ASTM D792 - 00) 1.407 1.498 1.542 1.352 1.618 1.618 1.399

[0175] Thermal insulation test: Procedure and Conditions: [0176] The thermal testing was undertaken on a 0.5 MTon Hydraulic press supplied by Zhejiang Taizhou Mingen Hydraulic Equipment Fabrication Co. It had a heatable base plate, an aluminium sample plate and a hydraulically powered top plate. [0177] Test specimens were prepared having the dimensions 8 cm length, 4 cm width and approximately 2 mm thickness and had a total surface area of 0.1092 m.sup.2. [0178] Each test specimen was mounted on the center of the aluminium sample plate. The surface area of the face of the specimen in direct contact with the heatable base plate was 0.0032 m2. A 10 kg steel loading was used which equated to a pressure of 0.0306 MPa after removing hydraulic pressing.

[0179] The Heat insulation tests were carried out at 595° C. and at 500° C. For the 595° C. test, samples were heated at 595° C. during the test period of 20 minutes with the first 7 minutes under a pressure of approximately 0.9 MPa and the remaining 13 minutes at a pressure of approximately 0.03 MPa as described above. The heated base plate of the press was first heated to about 595° C. (or 500° C. depending on the test selected) and once this temperature was reached the temperature of the heated plate was stabilized at 595° C. The test piece was then placed on the hot plate and the aluminum plate was placed on top of the sample sandwiching the sample between the heated base plate and the aluminium plate. The 10 kg steel loading plate was immediately put on the aluminum plate, and an additional 0.87 MPa pressure was applied using the hydraulic press to start the test. After 420 sec, the hydraulic pressure was removed, but the 10 kg steel loading was maintained on top of the Aluminium plate so as to maintain a pressure of 0.03 MPa on the sample for the remaining 780 seconds of the test period. Both heat stage temperature and test specimen back temperature were recorded during the test. After total time of 1200 sec, the test was stopped, steel loading and Aluminium plate was removed from the heat stage.

[0180] The temperatures of the directly heated face and the back face of the sample of thermally insulating layer under test were measured and compared using a WRNK-191 0.5*350 mm thermocouple from Taizhou Cesmooy.

TABLE-US-00005 Thermal insulation Testing Results of Examples Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex.6 Ex. 7 Heat face temp (°C) after heating at 595° C. 595 595 595 595 595 595 595 Back face temp (°-C) after heating at 595° C. 184.6 199.7 238 226.9 180.1 178.3 180 Heat face temp (°C) after heating at 500° C. 500 500 Back face temp (°-C) after heating at 500° C. 139.6 131.2

[0181] It will be seen that the temperature of the back face was mostly under 200° C. which is significantly lower than the comparatives including the current commercial offering of the coated aerogel.

TABLE-US-00006 Compositions of comparative examples Ingredients Comp. 1 Comp. 2 Comp. 3 Base A 48.00 98.00 19.50 Base C 58.50 Wollastonite, 15 .Math.m 50.00 Exp graphite(X-200) 20.00 Cerium hydroxide masterbatch 1.00 1.00 1.00 DHBP masterbatch 1.00 1.00 1.00 Coated Aerogel 100.00 100.00 100.00

[0182] The cerium hydroxide masterbatch and the DHBP masterbatch are the same as described above. The expanded graphite (X-200) was supplied by Qingdao Yanhai Carbon Materials Co. Ltd.

TABLE-US-00007 Amounts of the ingredients contained in the bases Key ingredients Comp. 1 Comp. 2 Comp. 3 Vinyl-term PDMS polymer having a Mw of 500,000 and vi of 0.010% 17.76 36.26 24.76 Vinyl-term PDMS polymer having a Mw of 500,000 and vi of 0.065% 17.76 36.26 24.76 Silicone polymer or fluid 40 82 56.52 Silica 9.4 18.8 24.48

[0183] Physical property results for the respective comparative compositions/ elastomers are shown, in Tables 5a and 5b with respect to the comparatives. The test methods used were as indicated or as described above.

TABLE-US-00008 Physical Test of Comparative examples Test Comp. 1 Comp. 2 Comp. 3 Shore A Durometer (ASTM D2240-15) 62 41 66 Specific gravity (ASTM D792 -00) 1.509 1.096 1.27

TABLE-US-00009 Thermal insulation Testing Results of Comparative examples Comp. 1 Comp. 2 Comp. 3 Heat face temp (°C) after heating at 595° C. 595 595 595 Back face temp (°C) after heating at 595° C. 426 454.8 294.4 Heat face temp (°C) after heating at 500° C. 500 Back face temp (°C) after heating at 500° C. 321.8

[0184] The examples provide a much improved rear plate temperature when compared with the comparative Examples. It was also noted that the side of samples facing the heated plate during the heat testing underwent at least partial ceramification where the side remote from the heating plate gave much lower temperature values and visually appeared to be elastomeric. Furthermore, the temperatures of the equivalent remote faces from the heating plate were much lower than those of the comparative examples. It is believed that these results are also improved compared to the commercially available coated aerogel products.

[0185] It was also found that when peroxide cure catalysts were used to cure the compositions, the inclusion of a small amount of a platinum material (similar to that used to cure the hydrosilylation catalysts above) gave improved results.

[0186] Hence thermally insulating layers as hereinbefore described are able to quickly generate a ceramic-like layer on the heat face for thermal insulation at high temperature (595° C.) & high pressure (0.9 MPa) testing conditions whilst the remote face temperature can keep lower than that of comparative examples and we believe aerogel felt materials currently used (180~240° C. vs 260~ 450° C.) and are able to maintain an elastomeric appearance. It was also noted that thermally insulating layers as described herein are substantially dust free unlike commercially available coated aerogel materials and as such would not require the same level of protective equipment as needed when using said commercially available coated aerogel materials.