Method for preconditioning a laminate to be used in electrochemical cell assemblies

Abstract

The invention relates to a method for preconditioning a laminate (10) to be used in electrochemical cell assemblies (30), said method comprising providing a laminate comprising a plurality of sheets (12) that are bonded together by a binder (14), and heating the laminate at a prebaking temperature (Tpb) for a predetermined prebaking time (Δt), said prebaking temperature being equal to or more than 650 °C. The invention also relates to the use of such a laminate in an electrochemical cell assembly as well as to an electrochemical cell assembly comprising at least one component having a laminate that is preconditioning by means of such a method.

Description

[0001] Description

[0002] Title

[0003] Method for preconditioning a laminate to be used in electrochemical cell assemblies

[0004] State of the Art

[0005] The invention relates to the field of electrochemical cell stacks, in particular fuel cell stacks and electrolyser cell stacks. More specifically, the invention relates to methods for preconditioning a laminate to be used in electrochemical cell assemblies, to the use of such a laminate in an electrochemical cell assembly, and to an electrochemical cell assembly comprising at least one component having such a laminate.

[0006] Fuel cells and electrolyser cells are examples of electrochemical cells. Fuel cells are energy conversion devices that allow for conversion of electrochemical fuels (e.g. H2) to electricity. Electrolyser cells may be considered as fuel cells running in reverse mode, i.e. using electricity to decompose a compound (e.g. H2O) into its constituent parts (e.g. H2 and O2). Reversible cells are capable of operating in both modes. Such electrochemical cells typically comprise electrochemically active layers that may be configured to allow for conversion of electrochemical fuel to electricity (fuel cells) or for decomposing a compound into its constituent parts using electricity (electrolyser cells).

[0007] The present invention specifically relates to solid oxide cells (SOCs). Such solid oxide cells (SOCs) typically comprise an electrolyte layer formed from a solid oxide, e.g. from Yttria-stabilised zirconia (YSZ), Gadolinia-doped Ceria, or Cerium Gadolinium Oxide (CGO). SOCs can be run as solid oxide fuel cell (SOFC) or as solid oxide electrolyser cell (SOEC). Typically, multiple of such cell units are stacked upon one another to form a stack of cell units, also referred to as 'cell repeat units'. Said stack of cell units is commonly arranged between two end plates that are located on opposite sides of the stack, thus forming an electrochemical cell assembly. The stack of cell units is usually held in compression between the end plates. That is to say, a compressive force acting along the stacking direction is supplied to the stack of cell units by the end plates. This may secure a direct contact and, thus, an electrical connection between adjacent cell units of the stack.

[0008] In the field of electrochemical cells, components formed from mica group minerals, a group of phyllosilicate minerals, have proven advantageous due to their electrically insulating properties and their stability under elevated temperatures (SOFC's operation temperatures may, for example, reach 650- 1000 °C), for example. Such components from mica group minerals are typically provided as a laminate comprising a plurality of sheets that are stacked upon one another and bonded together by a silicone binder. Typically, components formed from mica group minerals are preconditioned by means of a heat treatment prior to their use in an electrochemical cell assembly. Said heat treatment is usually performed at temperatures below or around 600 °C.

[0009] It is an object of the invention to improve long-term stability of an electrochemical cell assembly.

[0010] Description of the Invention

[0011] According to the invention, there is provided a method for preconditioning a laminate with the features of claim 1.

[0012] The method comprises providing a laminate having a plurality of sheets that are stacked upon one another and bonded together by a binder, said sheets being formed from a sheet material comprising at least one mica group mineral. In the laminate, the binder may be spread on the sheets and fill out voids between adjacent sheets. The binder may be silicone-based (i.e. , comprises a silicone material, preferably a siloxane material). The method further comprises performing a prebaking treatment on said laminate, said prebaking treatment comprising arranging the laminate in a prebaking space, and heating the laminate in the prebaking space at a prebaking temperature provided in the prebaking space for a predetermined prebaking time. The prebaking temperature is equal to or more than 650 °C. In other words, the laminate is preconditioned by heating the laminate at a temperature of 650 °C or above for the predetermined prebaking time. Thus, the temperature value of 650 °C is the lower temperature limit of the prebaking temperature.

[0013] As used herein, the term "prebaking treatment" refers to a process that is performed prior to assembling the electrochemical cell assembly. Preferably, the laminate is present as a stand-alone piece during the prebaking treatment. The term "prebaking treatment" is particularly used to distinguish this process from processes that occur in the assembled electrochemical cell assembly, e.g. a heat treatment of the assembled electrochemical cell assembly to condition the assembled electrochemical cell assembly or a heat exposure resulting from elevated temperatures during the intended operation of the electrochemical cell assembly.

[0014] The inventors have found that a prebaking treatment at a prebaking temperature of equal to or more than 650 °C significantly improves the mechanical characteristics and geometrical stability of the laminate compared to the known prebaking treatments performed at lower temperatures. This is believed to be caused by the release of binder from the laminate during the proposed prebaking treatment. Reducing the binder in the laminate prior to its final use, e.g. in an electrochemical cell assembly, aids mechanical long-term stability and, in particular, avoids shrinkage, i.e. a material and volume loss, of the laminate during operation. Thus, for example when used as an insulation component, e.g. insulation plate, arranged between the stack of cell units and one of the end plates of the electrochemical cell assembly, a shrinkage-induced reduction of a compressive force exerted on the cell units can be avoided. In addition, the proposed prebaking treatment aids to reduce or avoid potential deposition of decomposition products of the (e.g., silicone) binder on other components of the electrochemical cell assembly, e.g. on the cell units, which is beneficial for a long-term performance of those components. Preferably, providing the laminate comprises forming a plurality of sheets from the sheet material and bonding the sheets together by means of the binder. The sheets may be prepared by grinding a mica material into fine particles, preparing an aqueous suspension or slurry of the resulting mica material particles, and then forming the mica material particles into sheets by means of conventional papermaking techniques. The resulting sheets may then be wetted with the binder, stacked upon one another and bonded together by the binder to form the laminate.

[0015] The sheet material comprises at least one mica group mineral. Hence, the sheet material may comprise only one mica group mineral or a mixture of at least two different mica group minerals. Furthermore, the sheet material may comprise one or more additional substances in addition to the mica group mineral or mica group minerals, i.e. substances that are not mica group minerals. Preferably, the mass concentration of mica group mineral or mica group minerals in the sheet material is at least 90%, preferably at least 95%. Preferably, the sheets are mica sheets.

[0016] Preferably, the prebaking environment is provided in a heating chamber of an oven. The oven may be arranged in a manufacturing hall or the like.

[0017] In some preferred embodiments, the prebaking temperature is equal to or more than 700 °C. A lower temperature limit of 700 °C has proven especially advantageous since the prebaking time required for the release of a desired amount of the binder can be reduced. This may help to optimise the overall production process. Further to this, a reduction of the prebaking time may also go along with a reduced power consumption. Preferably, the prebaking temperature is equal to or more than 750 °C, most preferably equal to or more than 780 °C.

[0018] In some preferred embodiments, the prebaking temperature is equal to or less than 900 °C. That is to say, there is provided an upper temperature limit for the prebaking temperature in addition to the lower temperature limit. Temperatures higher than 900 °C might result in unwanted changes of the laminate, e.g. a delamination of the sheets. Preferably, the prebaking temperature is equal to or less than 850 °C, most preferably equal to or less than 820 °C. In some preferred embodiments, the predetermined prebaking time is at least 1 h, preferably at least 2 h, more preferably at least 3 h. Longer prebaking times result in a release of the binder from the laminate to a greater extent. The prebaking time may be adjusted to the prebaking temperature. Specifically, the prebaking time may be reduced with an increase in the prebaking temperature and increased with a reduction of the prebaking temperature. The predetermined prebaking time may be at most 10 h, preferably at most 8 h, more preferably at most 7 h.

[0019] In some preferred embodiments, the temperature in the prebaking space is kept constant for the prebaking time. That is to say, the temperature in the prebaking space is set to a predetermined or desired temperature value and kept at this temperature value for the prebaking time. Alternatively, the temperature may be varied during the prebaking treatment. In any case, the laminate is heated at a prebaking temperature being equal to or more than 650 °C for the predetermined prebaking time. Further restrictions regarding the prebaking temperature may be provided as discussed above.

[0020] In some preferred embodiments, the laminate is arranged in the prebaking space at an insertion temperature that is lower than the prebaking temperature. The temperature is successively (gradually) increased in the prebaking space with the laminate arranged therein until the prebaking temperature is provided. As a consequence, the laminate will heat up slowly and in a uniform manner along with the prebaking space, thus leading to reduced thermal stresses in the laminate. A laminate preconditioned in this way is less prone to delamination of the sheets (during preconditioning and during use).

[0021] In some preferred embodiments, the insertion temperature is equal to or less than 450 °C, preferably equal to or less than 300 °C, most preferably equal to or less than 150 °C. Particularly, the insertion temperature is the ambient temperature.

[0022] In some preferred embodiments, providing the prebaking temperature in the prebaking space comprises increasing the temperature in the prebaking space with a first temperature rise rate of equal to or less than 2.5 °C / min. Particularly, the temperature is increased with the first temperature rise rate for a time interval of at least 10 minutes, more preferably at least 20 minutes. As discussed above, increasing the temperature in the prebaking space with the comparatively low first temperature rise rate protects the laminate from delamination. Preferably, the first temperature rise rate is equal to or less than 2.0 °C / min, more preferably equal to or less than 1.5 °C / min, more preferably equal to or more than 0.5 °C / min and equal to or less than 1.5 °C / min, most preferably around 1.0 °C / min. Preferably, the temperature in the prebaking space is increased only temporarily with the first temperature rise rate, i.e. only during part of the time that it takes to increase the temperature to the prebaking temperature. That is to say, the temperature in the prebaking space may be increased with a temperature rise rate that differs from the first temperature rise rate during part of the time that it takes to increase the temperature to the prebaking temperature, e.g. with a temperature rise rate that is higher than the first temperature rise rate. Alternatively, the temperature in the prebaking space is increased with the first temperature rise rate during the entire time that it takes to increase the temperature to the prebaking temperature.

[0023] In some preferred embodiments, providing the prebaking temperature in the prebaking space comprises temporarily increasing the temperature in the prebaking space with the first temperature rise rate and temporarily increasing the temperature in the prebaking space with a second temperature rise rate that is higher than the first temperature rise rate. Increasing the temperature in the prebaking space with a higher temperature rise rate has the advantage that the duration for heating up the prebaking space may be reduced. Specifically, the temperature may be increased with the second temperature rise rate in temperature ranges that are less important regarding delamination of the laminate.

[0024] In some preferred embodiments, the second temperature rise rate is higher than the first temperature rise rate by at least 0.5 °C / min, more preferably at least 1.0 °C / min, most preferably at least 1.5 °C / min. Preferably, the second temperature rise rate is equal to or more than 2.5 °C / min, more preferably equal to or more than 2.5 °C / min and equal to or less than 4.0 °C / min, more preferably equal to or more than 2.5 °C / min and equal to or less than 3.5 °C / min, most preferably around 3.0 °C / min. In some preferred embodiments, the temperature in the prebaking space is increased between the ambient temperature and an intermediate temperature of equal to or more than 450 °C and equal to or less than 600 °C with the second temperature rise rate, wherein the temperature in the prebaking space is increased between the intermediate temperature and the prebaking temperature with the first temperature rise rate. Temperatures above the intermediate temperature are particularly important with respect to delamination of the laminate. Applying the first temperature rise rate at temperatures above the intermediate temperature therefore results in an effective protection of the laminate from delamination. Preferably, the temperature is increased from the intermediate temperature to the prebaking temperature with the first temperature rise rate. Thus, when reaching said intermediate temperature, the first temperature rise rate may be applied and the temperature in the prebaking space may be increased from the intermediate temperature to the prebaking temperature with the first temperature rise rate.

[0025] In some preferred embodiments, the sheet material comprises muscovite and / or phlogopite as the at least one mica group mineral.

[0026] In some preferred embodiments, prior to the prebaking treatment, the mass concentration of binder in the laminate is at least 5% and at most 15%, preferably at least 8% and at most 12%. This mass concentration of binder enables a mechanically robust bonding of the stacked sheets to each other. The prebaking treatment may result in a weight loss of the laminate of at least 2%, preferably of around 5%. In some cases the mass concentration of binder subsequent to the prebaking treatment is at most 5%.

[0027] In some preferred embodiments, the laminate is shaped to a component to be used in an electrochemical cell assembly. Depending on the intended use of the component, different shapes of the component are possible. For example, the laminate may be shaped to a plate-shaped component or to a sleeve-shaped component.

[0028] In some preferred embodiments, the laminate is shaped to said component prior to the prebaking treatment. That is to say, the laminate is brought to its intended shape prior to the prebaking treatment. This has several advantages. Firstly, the laminate is easier to process prior to the prebaking treatment. Specifically, the laminate is less brittle. Hence, the risk of an unwanted breaking of the laminate during shaping the laminate is smaller prior to the prebaking treatment.

[0029] Furthermore, shaping the laminate to the component typically results in an increase of the surface of the laminate relative to its volume. This in turn may accelerate the removal of the binder from the laminate which may ultimately enable a reduction of the prebaking time.

[0030] In some preferred embodiments, the binder is a silicone-based binder.

[0031] The invention also relates to the use of a laminate that is preconditioned according to the above-described method in an electrochemical cell assembly.

[0032] The invention also relates to an electrochemical cell assembly with the features of claim 18. The electrochemical cell assembly comprises a stack of cell units, comprising a plurality of cell units that are stacked upon one another along a stacking direction. The electrochemical cell assembly further comprises at least one component, i.e. only one component or several components, having a laminate or being formed from a laminate that has been preconditioned by means of the above-described method.

[0033] In some preferred embodiments, the at least one component is stacked upon the stack of cell units, or the stack of cell units is stacked upon the at least one component or the at least one component is stacked within the stack of cell units, or any combination thereof. The stack and at least one component are typically held in compression. In this context, the above-described method of preconditioning the laminate has the advantage that a shrinkage of the plateshaped component during operation of the electrochemical cell assembly is prevented or reduced.

[0034] In some preferred embodiments, the electrochemical cell assembly comprises a first end plate assembly having a first end plate and a second end plate assembly having a second end plate, wherein the at least one component comprises an insulating plate that is arranged between the first end plate and the stack of cell units or between the second end plate and the stack of cell units. Said plateshaped component may act as an insulating plate electrically insulating the stack of cell units from the respective end plate. Preferably, the stack of cell units is held in compression between the first end plate and the second end plate. In this context, the above-described method of preconditioning the laminate has the advantage that a shrinkage of the plate-shaped component during operation of the electrochemical cell assembly is prevented or reduced. In consequence, a compressive force acting on the stack of cell units can be maintained at a desired level. In addition, preconditioning aids to reduce or avoid potential deposition of decomposition products of the binder.

[0035] In some preferred embodiments, the electrochemical cell assembly comprises at least one electrical conductor, particularly a bus bar, and the at least one component comprises an insulating sleeve surrounding said electrical conductor.

[0036] In some preferred embodiments, the electrochemical cell assembly comprises a housing surrounding the stack of cell units and the at least one component comprises an insulating plate that is located in a gap between the housing and the external perimeters of the cell units.

[0037] Further embodiments are derivable from the following description and the drawings:

[0038] Figure 1 shows a method for preconditioning a laminate to be used in electrochemical cell assemblies;

[0039] Figure 2 shows an exemplary temperature profile during a prebaking treatment of the method for preconditioning;

[0040] Figure 3 shows a cross-sectional view of an embodiment of an electrochemical cell assembly; and

[0041] Figure 4 shows a top view of the cell assembly shown in Figure 3.

[0042] Referring to Figures 1 and 2, there is illustrated a method for preconditioning a laminate 10 to be used in electrochemical cell assemblies 30. In a first step 100, the laminate 10 is provided. The box corresponding to the first step 100 shows an enlarged cutout of the laminate 10 in a schematic manner. The laminate 10 comprises a plurality of sheets 12 that are stacked upon one another and bonded together by a binder 14, in this case a silicone binder 14. The silicone binder 14 is spread on the sheets 12 and arranged in voids between adjacent sheets 12. The mass concentration of silicone binder 14 in the laminate 10 may be between 5% and 15% at this point. The sheets 12 may be arranged in parallel to each other. However, as shown in Figure 1, the sheets 12 may also be at a slight angle relative to each other.

[0043] The sheets 12 are formed from a sheet material comprising at least one mica group mineral, i.e. the sheets 12 are mica sheets 12. Said at least one mica group mineral may be muscovite or phlogopite, for example. Laminates formed from mica sheets have proven advantageous in electrochemical cell assemblies due to their electrically insulating properties and their stability at high temperatures, for example.

[0044] In a second step 102, the laminate 10 is shaped to a component 16 to be used in an electrochemical cell assembly. In this example, the laminate 10 is shaped to a plate-shaped component 16. The plate-shaped component 16 can be used in an electrochemical cell assembly as an insulating plate, for example. The component 16 may comprise structures like through-holes (e.g., for fluid ports) or depressions formed therein. The laminate 10 may be shaped to the component 16 by means of a milling process, for example.

[0045] In a third step 104, a prebaking treatment is performed on the laminate 10, i.e. the component 16. For this, the laminate 10 is arranged in a prebaking space 18. The prebaking space 18 may be provided in the heating chamber of an oven, for example. The laminate 10 is then heated in the prebaking space 18 at a prebaking temperature Tpb provided in the prebaking space 18 for a predetermined prebaking time At. In this example, the prebaking temperature Tpb is 800 °C. In other examples, the prebaking temperature Tpb may differ from 800 °C. Satisfactory results were achieved with prebaking temperatures Tpb of equal to or more than 650 °C. In this example, the laminate 10 is arranged in the prebaking space 18 at an insertion temperature that is lower than the prebaking temperature Tpb. Subsequently, the prebaking temperature Tpb is provided in the prebaking space 18 with the laminate 10 arranged in the prebaking space 18. Preferably, the laminate 10 is arranged in the prebaking space 18 at ambient temperature, i.e. the insertion temperature is the ambient temperature.

[0046] Figure 2 shows an exemplary temperature profile according to which the temperature in the prebaking space 18 may be increased to the prebaking temperature Tpb. In the specific example, the temperature is temporarily increased with a low first temperature rise rate and temporarily with a higher second temperature rise rate.

[0047] Preferably, the first temperature rise rate is equal to or more than 0.5 °C / min and equal to or less than 1.5 °C / min. In this example, the first temperature rise rate is 1.0 °C / min.

[0048] The second temperature rise rate is higher than the first temperature rise rate. Preferably, the second temperature rise rate is equal to or more than 2.0 °C / min and equal to or less than 4.0 °C / min. In this example, the second temperature rise rate is 3.0 °C / min.

[0049] In other words, the temperature in the prebaking space 18 is temporarily increased with a temperature rise rate of 3.0 °C / min and temporarily with a temperature rise rate of 1.0 °C / min.

[0050] The first temperature rise rate and the second temperature rise rate may be applied in different temperatures ranges during heat up in order to protect the laminate from delamination.

[0051] In the specific example illustrated in Figure 2, starting from ambient temperature, the temperature in the prebaking space 18 is increased with the second temperature rise rate. Once the temperature in the prebaking space 18 reaches a temperature of 300 °C, the temperature is increased further with the first temperature rise rate. Once the temperature in the prebaking space 18 reaches a temperature of 450 °C, the temperature is increased further with the second temperature rise rate.

[0052] Once the temperature in the prebaking space 18 reaches a predetermined intermediate temperature Tim, e.g. a temperature of 550 °C, the first temperature rise rate is applied. The temperature in the prebaking space 18 is then increased from the intermediate temperature Tim to the prebaking temperature Tpb with the first temperature rise rate. It was discovered that temperatures that are higher than the intermediate temperature Tim are especially important regarding delamination of the laminate 10. In other examples, the predetermined intermediate temperature Tim may differ from 550 °C. Preferably, the predetermined intermediate temperature Tim is equal to or more than 450 °C and equal to or less than 650 °C. The choice of the intermediate temperature Tim may depend on the composition of the laminate 10, e.g. the ratio of sheet material to silicone binder. The greater rise rate of the second temperature rise rate (in comparison to the first temperature rise rate) allows the prebaking space 18 to be warmed more quickly, decreasing the amount of time spent in the prebaking space by the laminate 10.

[0053] Once the temperature in the prebaking space 18 reaches the prebaking temperature Tpb, the temperature in the prebaking space 18 is held constant for the predetermined prebaking time At. That is to say, the laminate 10 is heated in the prebaking space 18 at the prebaking temperature Tpb for the predetermined prebaking time At. This results in the silicone binder 14 being removed from the laminate 10 in large quantities. Accordingly, a laminate 10 having low silicone content is obtained (see third step 104 in Figure 1). Some decomposition products of the silicone binder, e.g. silicon oxides, may remain in the laminate 10.

[0054] In this example, the predetermined prebaking time At is 3 hours, i.e. the temperature in the prebaking space 18 is held at the prebaking temperature Tpb for 3 hours. One should note that the prebaking time At is illustrated shorter in Figure 2 for convenience. Upon expiration of the prebaking time At, the temperature in the prebaking space 18 is decreased. For this, the prebaking space 18 may be allowed to cool down or may be actively cooled down.lt will be understood that the prebaking space may be, for example, a space which is warmed and cooled or a conveyor oven through which the laminate passes, experiencing the temperature profile outlined in Figure 2 as it does so.

[0055] Referring now to Figures 3 and 4, there is illustrated an exemplary configuration of an electrochemical cell assembly 30. It should be noted that several components of the electrochemical cell assembly 30 have been removed in Figure 4. In consequence, a cell unit 34 is visible as the uppermost component of the electrochemical cell assembly 30 in Figure 4.

[0056] The electrochemical cell assembly 30 comprises a stack 32 having a plurality of cell units 34 that are stacked upon one another along a stacking direction 36. The cell units 34 may be fuel cell units, electrolyser cell units or reversible cell units. The cell units 34 extend in a respective cell plane that is perpendicular to the stacking direction 36. The cell units 34 are electrically connected in series. In this example, the cell units 34 are configured flat. An electrical connection between adjacent cell units 34 is established by a direct contact between those cell units 34.

[0057] The electrochemical cell assembly 30 further comprises a first end plate assembly 38 having a first end plate 40 and a second and plate assembly 42 having a second end plate 44. The stack 32 of cell units 34 is arranged between the first end plate 40 and the second end plate 44. That is to say, the end plates 40 and 44 are arranged on opposite sides of the stack 32 and the stack 32 is arranged in a receiving volume defined between the end plates 40 and 44. Preferably, the stack 32 is held in compression between the end plates 40 and 44. This secures the direct contact between adjacent cell units 34 and, thus, the electrical connection between the cell units 34.

[0058] The electrochemical cell assembly 30 further comprises a housing 46 that surrounds the stack 32. Preferably, the housing 46 is fixedly attached to the end plates 40 and 44, e.g. by welding.

[0059] In this example, the electrochemical cell assembly 30 further comprises a first insulating plate 48 that is interposed between the first end plate 40 and the stack 32 of cell units 34. In this example, an electrically conductive first power transmission plate 50 is interposed between the stack 32 of cell units 34 and the first insulating plate 48. The first power transmission plate 50 is in direct contact with the first insulating plate 48 and the stack 32 of cell units 34, i.e. the lowermost cell unit 34.

[0060] In this example, an electrically conductive second power transmission plate 52 is interposed between the stack 32 of cell units 34 and the second end plate 44. The second power transmission plate 52 is in direct contact with the stack 32 of cell units 34, i.e. the uppermost cell unit 34.

[0061] In this example, a second insulating plate 54 is interposed between the second power transmission plate 52 and the second end plate 44. The second insulating plate 54 is in direct contact with the second power transmission plate 52.

[0062] In this example, an electrically conductive third power transmission plate 56 is interposed between the second insulating plate 54 and the second end plate 44. The third power transmission plate 56 is in direct contact with the second insulating plate 54.

[0063] In this example, a third insulating plate 58 is interposed between the third power transmission plate 56 and the second end plate 44. The third insulating plate 58 is in direct contact with the third power transmission plate 56 and the second end plate 44.

[0064] The third power transmission plate 56 is electrically connected to the first power transmission plate 50 by means of one or more bus bars 60 that span the stack 32 of cell units 34 along the stacking direction 36. In consequence, the third power transmission plate 56, the bus bars 60, the first power transmission plate 50, the stack 32 of cell units 34 and the second power transmission plate 52 are electrically connected in series in this order. The bus bars 60 are surrounded by a respective insulating sleeve 62.

[0065] The electrochemical cell assembly 30 further comprises two insulating plates 64 that are located in a respective gap 66 that is formed between the housing 46 and the external perimeters 68 of the cell units 34. The insulating plates 64 electrically insulate the cell units 34 from the housing 46. Several of the components of the electrochemical cell assembly 30 are formed by a laminate that was preconditioned according to the method described above in the context of Figures 1 and 2. In this example, the insulating plates 48, 54, 58 and 64 as well as the insulating sleeves 62 are formed by such laminate. Due to their electrically insulating properties and their stability under elevated temperatures mica sheets are generally well suitable for these components of the electrochemical cell assembly 30. The preconditioning process has the advantage that the silicone binder 14 is removed from the laminates 10 in large quantities prior to assembling the electrochemical cell assembly 30. Thus, potential release of the silicone binder 14 from the laminates 10, i.e. the components 48, 54, 58, 64 and 62, during operation of the electrochemical cell assembly 30 is avoided.

Claims

Claims1. A method for preconditioning a laminate (10) to be used in electrochemical cell assemblies (30), said method comprising: a. providing a laminate (10) comprising a plurality of sheets (12) that are stacked upon one another and bonded together by a binder (14), said sheets (12) being formed from a sheet material comprising at least one mica group mineral, and b. performing a prebaking treatment on said laminate (10), said prebaking treatment comprising: i. arranging the laminate (10) in a prebaking space (18), and ii. heating the laminate (10) in the prebaking space (18) at a prebaking temperature (Tpb) provided in the prebaking space (18) for a predetermined prebaking time (At), said prebaking temperature (Tpb) being equal to or more than 650 °C.

2. The method according to claim 1 , wherein the prebaking temperature (Tpb) is equal to or more than 700 °C, more preferably equal to or more than 750 °C, most preferably equal to or more than 780 °C.

3. The method according to any one of the preceding claims, wherein the prebaking temperature (Tpb) is equal to or less than 900 °C, preferably equal to or less than 850 °C, most preferably equal to or less than 820 °C.

4. The method according to any one of the preceding claims, wherein the predetermined prebaking time (At) is at least 1 h, preferably at least 2 h, more preferably at least 3 h.

5. The method according to any one of the preceding claims, wherein the temperature in the prebaking space (18) is kept constant for the predetermined prebaking time (At).

6. The method according to any one of the preceding claims, wherein the laminate (10) is arranged in the prebaking space (18) at an insertion temperature that is lower than the prebaking temperature (Tpb), and wherein the prebaking temperature (Tpb) is provided in the prebaking space (18) with the laminate (10) arranged in the prebaking space (18).

7. The method according to the preceding claim, wherein the insertion temperature is equal to or less than 500 °C, preferably equal to or less than 300 °C, most preferably equal to or less than 150 °C.

8. The method according to any one of the preceding claims, wherein providing the prebaking temperature (Tpb) in the prebaking space (18) comprises increasing the temperature in the prebaking space (18) with a first temperature rise rate of equal to or less than 2.5 °C / min, preferably equal to or less than 2.0 °C / min, more preferably equal to or less than 1.5 °C / min, most preferably equal to or more than 0.5 °C / min and equal to or less than 1.5 °C / min.

9. The method according to the preceding claim, wherein providing the prebaking temperature (Tpb) in the prebaking space (18) comprises temporarily increasing the temperature in the prebaking space (18) with the first temperature rise rate and temporarily increasing the temperature in the prebaking space (18) with a second temperature rise rate that is higher than the first temperature rise rate.

10. The method according to the preceding claim, wherein the second temperature rise rate is higher than the first temperature rise rate by at least 0.5 °C / min, more preferably at least 1.0 °C / min, most preferably at least 1.5 °C / min.

11. The method according to any one of claims 9 and 10, wherein the temperature in the prebaking space (18) is increased between ambient temperature and an intermediate temperature (Tim) of equal to or more than 450 °C and equal to or less than 600 °C with the second temperature rise rate, and wherein the temperature in the prebaking space (18) is increased between the intermediate temperature (Tim) and the prebaking temperature (Tpb) with the first temperature rise rate.

12. The method according to any one of the preceding claims, wherein the sheet material comprises muscovite and / or phlogopite as the at least one mica group mineral.

13. The method according to any one of the preceding claims, wherein, prior to the prebaking treatment, the mass concentration of binder (14) in the laminate (10) is at least 5% and at most 15%, preferably at least 8% and at most 12%.

14. The method according to any one of the preceding claims, wherein the laminate (10) is shaped to a component (16) to be used in an electrochemical cell assembly (30).

15. The method according to the preceding claim, wherein the laminate (10) is shaped to said component (16) prior to the prebaking treatment.

16. The method according to any one of the preceding claims, wherein the binder (14) is a silicone-based binder.

17. Use of a laminate (10) preconditioned according to any one of the preceding claims in an electrochemical cell assembly (30).

18. An electrochemical cell assembly (30) comprising: a stack (32) of cell units (34), comprising a plurality of cell units (34) that are stacked upon one another along a stacking direction (36), and at least one component (16) comprising a laminate (10) that is preconditioned by means of a method according to any one of claims 1 to 16.

19. The electrochemical cell assembly (30) according to the preceding claim, wherein the at least one component (16) is stacked upon the stack (32) of cell units (34), or the stack (32) of cell units (34) is stacked upon the at least one component (16) or the at least one component (16) is stacked within the stack (32) of cell units (34).

20. The electrochemical cell assembly (30) according to any one of claims 18 and 19, wherein wherein the electrochemical cell assembly (30) comprises a first end plate assembly (38) having a first end plate (40) and a second endplate assembly (42) having a second end plate (44), and wherein the at least one component (16) comprises an insulating plate (48, 54, 58) that is arranged between the first end plate (40) and the stack (32) of cell units (34) or between the second end plate (44) and the stack (32) of cell units (34).

21. The electrochemical cell assembly (30) according to any one of claims 18 to20, wherein the electrochemical cell assembly (30) comprises at least one electrical conductor (60), particularly a bus bar (60), and wherein the at least one component (16) comprises an insulating sleeve (62) surrounding said electrical conductor (60).

22. The electrochemical cell assembly (30) according to any one of claims 18 to21, wherein the electrochemical cell assembly (30) comprises a housing (46) surrounding the stack (32) of cell units (34), and wherein the at least one component (16) comprises an insulating plate (64) that is located in a gap (66) between the housing (46) and the external perimeters (68) of the cell units (34).

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