Method of sintering electrochemical cell stack and furnace for sintering the electrochemical cell stack

Abstract

To provide a method of sintering an electrochemical cell stack and a furnace for sintering the electrochemical cell stack.SOLUTION: A method of sintering an electrochemical cell stack includes: placing the electrochemical cell stack in a cage 200 which applies a first compressive load to the electrochemical cell stack; moving the cage containing the electrochemical cell stack in a moving direction M through a furnace 100 including a sintering region 120; sintering the electrochemical cell stack in the sintering region of the furnace; and applying a second compressive load greater than the first compressive load to the electrochemical cell stack during the sintering.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] [Related Applications] This application claims the benefit of priority of U.S. Provisional Application No. 63 / 607,915, filed on December 8, 2023, entitled "Method of Sintering an Electrochemical Cell Stack and Furnace for Sintering the Electrochemical Cell Stack", the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present disclosure relates to a method of sintering an electrochemical cell stack and a furnace for sintering an electrochemical cell stack.

Background Art

[0003] An electrochemical cell can be used to generate electrical energy from chemical energy and to generate chemical energy from electrical energy. A fuel cell is an electrochemical device that can convert the chemical energy of a fuel (e.g., hydrogen or hydrocarbon fuel) and an oxidant (e.g., air or oxygen) into electricity. An electrolytic cell is an electrochemical device that can use electricity to drive a chemical reaction (e.g., the decomposition of water into hydrogen and oxygen). Electrochemical cells can be stacked in a columnar shape. The column can include one or more stacks of electrochemical cells.

Summary of the Invention

[0004] One embodiment of the present disclosure is a method of sintering an electrochemical cell stack, the method including placing the electrochemical cell stack in a cage that applies a first compressive load to the electrochemical cell stack, moving the cage containing the electrochemical cell stack in a moving direction through a furnace including a sintering region, sintering the electrochemical cell stack in the sintering region of the furnace, and applying a second compressive load greater than the first compressive load to the electrochemical cell stack while sintering the stack in the sintering region.

[0005] One embodiment of the present disclosure includes a furnace, comprising a furnace body including a sintering region, and a pusher assembly configured to press one or more cages that house one or more electrochemical cell stacks sintered within the furnace body, wherein each cage is configured to apply a first compressive load to the electrochemical cell stack, and a compression assembly located within the sintering region of the furnace body and configured to apply a second compressive load greater than the first compressive load to the one or more electrochemical cell stacks.

[0006] The accompanying drawings, which are incorporated herein and constitute a part of this specification, illustrate examples of the disclosed apparatus and methods and, together with the general description given above and the detailed description given below, serve to explain the features of the present invention.

Brief Description of the Drawings

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[0008] Various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The drawings are not necessarily to scale and are intended to illustrate various features of the invention. As far as possible, the same reference numerals are used throughout the drawings to refer to the same or similar parts. References to specific examples and embodiments are for illustrative purposes and are not intended to limit the scope of the invention or the claims.

[0009] In this specification, a range may be expressed as from one particular value and / or to another particular value, such as from about one particular value and / or to about another particular value. By way of example when such a range is expressed, it may be from one particular value and / or to another particular value. Similarly, when a value is expressed as approximate by use of the word "about" or "substantially" at the beginning, it will be understood that the particular value forms another aspect. In some embodiments, a value of "about X" may include a value of ±1%X. It will be further understood that each endpoint of a range is important, whether in relation to the other endpoint or independent of the other endpoint.

[0010] An electrochemical cell, such as a fuel cell, can include an anode, a cathode, and an electrolyte between the anode and the cathode that allows ions (e.g., hydrogen ions, oxygen ions, etc.) to move between the anode and the cathode. The electrochemical cell may have a substantially planar shape, in which case the anode, cathode, and electrolyte may be formed as layers within the electrochemical cell. This can enable a plurality of electrochemical cells to be stacked together to form an electrochemical cell column including one or more electrochemical cell stacks (e.g., a fuel cell stack, an electrolytic cell stack, etc.).

[0011] The electrochemical cells in an electrochemical cell stack can be separated by interconnects. The interconnect can function as a gas flow separator plate that separates the gas at the first electrode (e.g., the anode) of an electrochemical cell from the gas at the second electrode (e.g., the cathode) of an adjacent electrochemical cell in the stack. The electrochemical cell stack can include a fuel cell stack or an electrolytic cell stack, such as a solid oxide fuel cell (SOFC) stack or a solid oxide electrolyzer cell (SOEC) stack.

[0012] In a SOEC stack, water (e.g., steam) can be provided to the first electrode of the SOEC through an interconnecting water channel, and air can optionally be provided to the second electrode of the SOEC through an interconnecting air channel. Water is separated into hydrogen and oxygen at the first electrode, and when a voltage or current is applied to the electrolyzer stack, oxygen ions are transported from the first electrode through the electrolyte to the second electrode.

[0013] In a SOFC stack, the interconnect can operate as a gas fuel separator that separates a fuel such as a hydrocarbon or hydrogen fuel flowing to the first electrode (e.g., a fuel electrode called an anode) of one SOFC in the stack from an oxidant such as air flowing to the second electrode (e.g., an air electrode called a cathode) of an adjacent SOFC in the stack. At either end of the stack, there may be an air end plate or a fuel end plate that supplies air or fuel to the end electrodes, respectively. The main chemical reaction at the SOFC anode is the electrochemical oxidation of hydrogen (and CO) that occurs at the interface of the electrode material in contact with the electrolyte. Hydrogen oxidation generates water and free electrons, and these electrons are released to the external circuit. The oxidant supplied to the cathode of the SOFC receives electrons from the external circuit and undergoes a reduction reaction. The flow of electrons (from the anode to the cathode through the external circuit) generates direct current (DC) electricity. SOFC fuel cells are often arranged in a stack to increase the amount of DC power generated.

[0014] One or more embodiments of the present disclosure can include a method of sintering an electrochemical cell stack and a furnace for sintering an electrochemical cell stack. One embodiment can include a ceramic cage that applies a first compressive load to the electrochemical cell stack during the sintering process. One embodiment can include a furnace that includes a sintering zone and a compression assembly that applies a second compressive load to the electrochemical cell stack within the sintering zone that is greater than the first compressive load. The second compressive load can be a single uniform load or a series of incremental loads greater than the first compressive load and up to the second compressive load. One embodiment can include a pusher plate that includes a pusher plate manifold that transports the cage and is aligned with the anode inlet of the electrochemical cell stack. One embodiment can include a guide platform that includes a gas trough aligned with the pusher plate manifold. In one embodiment, a gas (e.g., nitrogen gas, compressed dry air (CDA), forming gas, etc.) can flow from the gas trough through the pusher plate manifold to the anode inlet of the electrochemical cell stack. Further embodiments provide a method of sintering and conditioning an electrochemical cell.

[0015] For the purposes of this application, "sintering" includes heating, melting, and / or reflowing a glass or glass-ceramic forming powder and / or a glass or glass-ceramic seal precursor material (s) such as a glass or glass-ceramic layer within the stack to form a glass or glass-ceramic seal between the electrochemical cell and two adjacent interconnects within the stack. Sintering can be performed at a temperature above 600 degrees Celsius, such as 600 degrees Celsius to 1000 degrees Celsius, including 700 degrees Celsius to 800 degrees Celsius, 800 degrees Celsius to 900 degrees Celsius, 700 degrees Celsius to 900 degrees Celsius, 900 degrees Celsius to 950 degrees Celsius, and / or 950 degrees Celsius to 1000 degrees Celsius.

[0016] Manufacturing an electrochemical cell stack can involve heating the stack to a sintering temperature (e.g., within the range of about 600 °C to 1000 °C), flowing a high-purity inert gas (e.g., nitrogen gas) or a reducing gas (e.g., forming gas) through the stack to avoid oxidation of the stack components, and subjecting the stack to a large compressive load. This process is typically performed using a sealed furnace (stationary furnace) in which the electrochemical cell stack is stationary. Keeping the electrochemical cell stack stationary requires additional process cycle time, production time for equipment setup, and may add labor costs to the final product.

[0017] One or more embodiments of the present disclosure can include a sintering furnace through which an electrochemical cell stack moves during a sintering process (e.g., a continuous sintering furnace). The sintering furnace can include a conveying system that moves the stack (or stacks) through the furnace during sintering. The sintering furnace can include an incremental compressive load device and an intermittent direct gas delivery device.

[0018] One or more embodiments of the sintering furnace can reduce process cycle time, production time, and labor costs by placing the electrochemical cell stack on a conveying system that moves the stack through the sintering furnace. The sintering furnace can also reduce process variations (which can improve the overall stack production yield), be more compact, and increase capital efficiency. In a continuous furnace, the temperature can increase from ambient temperature to the sintering temperature over the length of the furnace chamber (e.g., over the length of the conveying system) and then return to ambient temperature again.

[0019] The sintering furnace can include three separate regions (e.g., segments), namely, a warm-up region, a sintering region, and a cooling region. The warm-up region can start at the furnace inlet, where the furnace temperature rises from the ambient temperature to the sintering temperature. The sintering region can start at the end of the warm-up region, where the temperature of the furnace is maintained at the sintering temperature. The cooling region can start at the end of the sintering region and continue to the furnace outlet. The temperature of the cooling region can be decreased from the sintering temperature to the ambient temperature.

[0020] The transport system within the sintering furnace can carry the electrochemical cell stack and move forward by a set length (hereinafter referred to as the pitch length) during a specified time (hereinafter referred to as the index time). The moving time includes the time when the electrochemical cell stack accelerates and decelerates. In one embodiment described below, the electrochemical cell stack can move forward multiple times during the index time. In one embodiment, the sum of the time (hereinafter referred to as the dwell time) during which the transport system can be stationary and the time (hereinafter referred to as the moving time) taken for the transport system to move forward can be the index time (t index = t move + t dwell ). For each period of one index time, a set amount of the electrochemical cell stack can be loaded onto the transport system near the inlet of the sintering furnace (e.g., the warm-up region), and a set amount of the electrochemical cell stack can be unloaded from the end of the sintering furnace (e.g., the cooling region). The number of electrochemical cell stacks that can be loaded and unloaded after each period can depend on the desired production rate, as well as the internal height and internal width of the sintering furnace. Similarly, a specific index time period may be determined by the desired production rate and the number of electrochemical cell stacks loaded and unloaded during each cycle.

[0021] A sintering furnace having a specific indexing time and production rate can maintain a specific temperature gradient along the path through which the electrochemical cell stack moves. In one embodiment, the sintering furnace can keep different atmosphere regions separate. In the transport system of the sintering furnace, the electrochemical cell stack can be disposed on plates that slide along the path of the sintering furnace. Each plate can contact an adjacent plate such that when the plate closest to the furnace inlet is pushed forward, all the plates in the furnace move forward (the plates move through the furnace in synchronization). An external actuator can push the plate closest to the furnace inlet for each cycle time during an operating time defined by a travel time. The actuator can be stationary during a dwell time.

[0022] Operating a sintering furnace in a warm-up region, a sintering region, and a cooling region can include a plurality of processing steps not used in a stationary furnace. First, using compressed dry air (CDA), chemical by-products such as volatile organic compounds (VOCs) generated from heating a seal material in the warm-up and cooling regions of the sintering furnace can be removed. For example, the seal material can include an organic binder and / or a solvent used as a carrier for distributing a glass or glass-ceramic seal inorganic precursor oxide material within the stack. Second, flowing an inert gas such as nitrogen, or a reducing gas such as forming gas, through the electrochemical cell stack, and / or immersing the electrochemical cell stack in ultra-high purity nitrogen after the electrochemical cell stack reaches the sintering temperature can be used to prevent or reduce oxidation of the stack components. Third, a variable intermittent compressive load is applied to the electrochemical cell stack within the furnace in the sintering region. A low compressive load can always be maintained on the stack to prevent movement within the stack. Once the electrochemical cell stack reaches the sintering temperature, a high compressive load can be applied. Further, the high compressive load can be applied intermittently and removed at a controlled rate, and / or continuously as the stack height decreases during sintering. One or more embodiments of the present disclosure can implement these processing steps within a sintering furnace to produce a sintered electrochemical cell stack.

[0023] First, in the warm-up region of the sintering furnace, CDA can be flowed over the electrochemical cell stack to supply oxygen and increase (e.g., maximize) the removal of VOCs in the warm-up region. The VOCs are oxidized by the air to form water and carbon dioxide, which can be pumped out of the furnace. The air atmosphere within the warm-up region can be maintained until the stack reaches a point within the furnace where the local temperature is in the range of 200°C to 600°C. An eductor can be used to circulate the CDA within the furnace to further promote temperature uniformity.

[0024] Second, from the point of view of the warm-up region where the furnace atmosphere can be in the range of 200°C to 600°C, the furnace atmosphere can be replaced with an inert gas such as ultra-high purity nitrogen and / or a noble gas (e.g., argon). In one embodiment, different regions of the furnace can include separate chambers separated from each other by one or more partitions such as an automatic door. The inert gas (e.g., nitrogen) environment can be separated from the air environment using at least one automatic door between the CDA chamber (e.g., warm-up chamber) and the inert gas chamber (e.g., sintering chamber) of the furnace. The door can be opened for each cycle to allow one or more stacks to pass through and can be closed after the stack(s) have passed through. The door(s) can prevent the mixing of gas flows from different furnace atmospheres in different chambers. Further, the furnace can have an area surrounded by a load lock door that can be purged to reduce or prevent the mixing of different atmospheres. Nitrogen gas can also be maintained at a higher pressure than the CDA to prevent the CDA from entering the sintering chamber. The nitrogen environment can be maintained throughout the furnace until the temperature of the cooling region can be in the range of 200°C to 500°C, at which point it is replaced with an air atmosphere. One or more additional automatic doors may be provided between the sintering chamber and the cooling chamber. An eductor can be used to circulate nitrogen within the furnace to further promote temperature uniformity.

[0025] In one embodiment, to ensure that the electrochemical cell stack is saturated with an inert gas such as ultra-high purity nitrogen or a reducing gas such as forming gas, the nitrogen is preheated and distributed from below the pusher plate and can flow through fuel holes (i.e., fuel riser openings) extending through the stack. The pusher plate (e.g., a series of pusher plates) can act as a seal for gas distribution and allow only gas to flow through the fuel holes in the stack. In an alternative embodiment, the inert gas may be provided into the stack through a load applicator device. In another embodiment, in addition to or instead of supplying the inert gas to the fuel riser openings of the stack, the entire sintering chamber can be filled with the inert gas.

[0026] Thirdly, in the sintering region (e.g., sintering chamber), the actuator (e.g., pneumatic actuator) can be spaced every one pitch length. The actuator can be attached to a load applicator device such as a ceramic rod located outside the furnace and capable of sliding into the furnace through an airtight seal. The actuator can be used to apply a variable compressive load to the electrochemical cell stack during the residence time. The compressive load applied during the residence time can be ramped up, held, and ramped down to avoid damage to the cells in the stack. The actuator can be retracted before the transport system moves. In one embodiment, to ensure that the seal material is confined to the desired regions within the stack and that the stack does not lose compression or move during movement through the sintering furnace, a constant load, such as a mass of 1 lbm to 50 lbm, can always be applied (regardless of whether additional compressive load from the load applicator device is received).

[0027] Fourth, the displacement of the position of the compressive load on the stack due to the thermal expansion of the furnace can be reduced by "central mooring". The expansion of the sintering furnace can be divided into two directions by central mooring, and the expansion in one direction can be avoided. Thereby, the maximum displacement in the region farthest from the mooring point can be reduced (for example, minimized). In one embodiment, the actuator can be "flexibly attached" to passively adjust the displacement. In order to further improve the alignment of the compression rod with the opening of the furnace housing, after the sintering part of the furnace stabilizes at the operating temperature and the expansion of the furnace subsides, the alignment can be calibrated.

[0028] In one embodiment, the electrochemical cell stack may be disposed within a ceramic container, such as a ceramic cage, while the stack is being sintered within the furnace. In one embodiment, the ceramic balls can be located on the upper block of the ceramic cage surrounding one or more stacks within the furnace, ensuring that only the vertical component of the compressive load can be applied despite a slight misalignment of the applied force.

[0029] The application and release rate of the compressive load, the dwell time under load at the sintering temperature, the warm-up rate, the cooling rate, and the ambient gas purity in the sintering region of the furnace help to reduce (for example, minimize) the installation area of the sintering furnace and can be configured to enhance cost-effectiveness while maintaining a high production yield. In one embodiment, the dwell time at the sintering temperature under a high compressive load is optimized to reduce the number of actuators applying a variable compressive load. Thereby, the installation area of the sintering furnace is reduced. In one embodiment, the dwell time duty cycle with respect to the total index may be at least about 85%. In one embodiment, the dwell time can be reduced by about 75% for the sintering of the stack in a stationary furnace.

[0030] FIG. 1 is a cross-sectional view of a furnace 100 according to one or more embodiments. The furnace 100 may be referred to as a sintering furnace. In one embodiment, the sintering furnace 100 can be a so-called pusher furnace or index furnace. As shown in FIG. 1, the furnace 100 can include a furnace body 101. The furnace body 101 can have a hollow tube shape such as a rectangular tube shape. The furnace body 101 can include a heat-resistant and heat-insulating furnace housing 102 having one or more walls, a roof, and / or a floor. The furnace housing 102 of the furnace body 101 can be made of steel, ceramic, or other suitable materials. The furnace body 101 can further include a furnace body inlet door 103 at the inlet end of the housing 102 of the furnace body 101 and a furnace body outlet door 104 at the outlet end of the housing 102 of the furnace body 101. In one embodiment, the furnace body 101 may have a linear horizontal shape (e.g., it may extend linearly as shown in FIG. 10B). However, the furnace body 101 may have other shapes in alternative embodiments.

[0031] The furnace 100 can include three regions (e.g., chambers) including a warm-up region (e.g., chamber) 110, a sintering region (e.g., chamber) 120, and a cooling region (e.g., chamber) 130. The furnace 100 can include a moving direction (M) from the warm-up region 110 through the sintering region to the cooling region 130. The furnace 100 can also include one or more heaters 105 that heat the warm-up region 110, the sintering region 120, and optionally the cooling region 130. The heater 105 can include, for example, one or more induction heaters, resistance heaters, radiant heaters (e.g., lamp heaters), or other suitable heaters. The heater 105 is shown as being near the floor of the furnace housing 102, but the heater 105 can be positioned near the roof and / or walls of the furnace housing 102.

[0032] The heater 105 can be arranged and / or controlled to gradually increase the temperature of the warm-up region 110 in the moving direction M. In one embodiment, the heater 105 can gradually heat the warm-up region 110 from the ambient temperature (e.g., about 25°C) to a sintering temperature in the range of 600°C to 1100°C (e.g., 900°C to 1000°C). The rate of change of temperature (dT / dt) of one or more electrochemical cell stacks 301 in the warm-up region 110 may be in the range of 1°C / min to 5°C / min (e.g., about 2°C / min). For example, each position (e.g., the position of the heater 105) within the furnace 100 can be set to a target temperature. The target temperatures at different positions may be different from each other.

[0033] The heater 105 can be arranged and / or controlled to maintain the sintering temperature within the sintering region 120. In one embodiment, the heater 105 can heat the sintering region 120 to a sintering temperature in the range of 600°C to 1100°C (e.g., 900°C to 1000°C). The temperature within the sintering region 120 may be substantially uniform throughout the sintering region 120 (e.g., dT / dt = 0). The length of the sintering region 120 may be greater than the minimum length required to accommodate the heat transfer between the furnace 100 and the electrochemical cell stack 301.

[0034] The cooling region 130 can optionally include one or more cooling devices 106 such as a cooling ring or a cooling pipe. To cool the cooling region 130, a coolant may be pumped through the cooling device 106. The cooling device 106 can gradually cool the cooling region 130 from the sintering temperature to the ambient temperature (e.g., about 25°C). The rate of change of temperature (dT / dt) in the cooling region 130 may decrease in the moving direction M. In one embodiment, the rate of change of temperature (dT / dt) of one or more electrochemical cell stacks 301 in the cooling region may be in the range of -1°C / min to -5°C / min. The cooling device 106 is shown to be near the floor of the furnace housing 102, but the cooling device 106 can be positioned near the roof and / or wall of the furnace housing 102.

[0035] The furnace 100 can also include sensors (not shown), such as temperature sensors, pressure sensors, and gas sensors, in each of the warm-up region 110, the sintering region 120, and the cooling region 130. The sensors can be used by a furnace control system 2500 that controls the overall operation of the furnace 100. The furnace control system 2500 can be connected to the furnace 100 by a wired connection or a wireless connection 2501. The furnace control system 2500 can include, for example, a dedicated logic integrated circuit or a computer 2511 (such as a server) that includes one or more processors (such as a central processing unit (CPU)) and one or more memory devices. The furnace control system 2500 can also include an input device 2512 (such as a keyboard, mouse, etc.) that enables an operator to input commands, data, etc. to the furnace control system 2500. The furnace control system 2500 can also include a display device 2513 (such as a monitor or display screen) that can display data related to the control of the furnace 100. In an alternative embodiment, the display device 2513 of the furnace control system 2500 can include a touch screen monitor for inputting input commands, data, etc. If the display device 2513 constitutes a touch screen, the input device 2512 may not be necessary for the furnace control system 2500.

[0036] The furnace body 101 can include a gas discharge port 107 within the furnace housing 102. The gas discharge port 107 can be opened so that gases such as volatile organic compounds (VOCs) can be discharged from each of the warm-up region 110, the sintering region 120, and optionally the cooling region 130. The gas discharge port 107 can optionally include one or more electronically controlled (or manually controlled) gas discharge valves (not shown) that open and close the gas discharge port 107. The gas discharge port 107 can be connected to a gas discharge line (not shown). In one embodiment, the gas discharge line can be connected to a vacuum device (not shown) such as a vacuum pump. The vacuum device can be activated to independently discharge gases from each of the warm-up region 110, the sintering region 120, and the cooling region 130.

[0037] The sintering region 120 can include a sintering chamber formed by the housing 102 of the furnace body 101 and the sintering chamber walls 125, 126 located within the furnace body 101. The sintering chamber can separate the warm-up region 110 from the cooling region 130. The sintering chamber walls 125, 126 can include a sintering chamber inlet door 123 at the inlet end of the sintering chamber and a sintering chamber outlet door 124 at the outlet end of the sintering chamber. The sintering chamber inlet door 123 and the sintering chamber outlet door 124 can form a substantially airtight seal when closed.

[0038] The furnace 100 can further include a substantially rigid guide platform 140. The guide platform 140 can extend beyond the inlet end of the furnace body 101 and beyond the outlet end of the furnace body 101. The guide platform 140 can be formed of steel, ceramic, or other suitable heat-resistant material. The guide platform 140 can also extend under the furnace body inlet door 103 and can include a loading portion that extends outward from the inlet end of the furnace body 101. The guide platform 140 can also extend under the furnace body outlet door 104 and can include an offloading portion that extends outward from the outlet end of the furnace body 101.

[0039] The furnace 100 can include a plurality of pusher plates 150 configured to slide along the upper surface of the guide platform 140. The pusher plates 150 can be formed of steel, ceramic, or other suitable heat-resistant material. In one embodiment, the pusher plates 150 and the guide platform 140 can have an interlock configuration that allows the guide platform 140 to provide a guide path for the pusher plates 150 in the moving direction M through the furnace body 101. In one embodiment, the surface of the pusher plates 150 and / or the surface of the guide platform 140 can be treated (e.g., coated) with a low-friction coating to help ensure that the pusher plates 150 slide easily along the guide platform 140.

[0040] One or more electrochemical cell stacks 301 may be disposed within a ceramic container such as cage 200, and cage 200 may be disposed on pusher plate 150. Cage 200 can be used to maintain proper alignment of the electrochemical cells and interconnects within electrochemical cell stack 301. Cage 200 can also be designed to apply a first (e.g., constant) compressive load to electrochemical cell stack 301. Pusher plate 150 having cage 200 thereon can be pressed onto guide platform 140 through furnace body 101. The edges of adjacent cages 200 within furnace 100 (i.e., from the leading edge of one cage to the trailing edge of the next cage) may be separated by a distance in the direction of movement M (e.g., the x-direction), and an exemplary distance ranges from about 40 mm to 120 mm (e.g., 60 mm to 90 mm).

[0041] Furnace 100 may further include a pusher assembly 160 that presses pusher plate 150 through furnace body 101. Pusher assembly 160 can be attached on or near guide platform 140. Pusher assembly 160 can be attached inside or outside furnace body 101. In one embodiment, pusher assembly 160 can be located at least partially inside furnace body 101 but outside housing 102. Pusher assembly 160 can include an actuator 161 (external actuator). Actuator 161 can include a pneumatic actuator or other suitable type of actuator. Pusher assembly 160 can further include a pusher rod 162 actuated by actuator 161. Pusher assembly 160 can also include a contact plate 163 fixed to the end of pusher rod 162.

[0042] When activated, the actuator 161 can press the pusher rod 162 away from the actuator 161 to press the contact plate 163 in the moving direction M. The contact plate 163 abuts against the rear end portion of the first pusher plate 150 and presses the first pusher plate 150 (which has the cage 200 thereon) in the moving direction M. The front end portion of the first pusher plate 150 can contact the rear end portion of the second pusher plate 150 such that the second pusher plate 150 is pressed in the moving direction by the first pusher plate 150. Each of the pusher plates 150 is in contact with the pusher plate 150 behind and / or in front in the moving direction M. Thereby, when the actuator 161 is activated and the contact plate 163 presses the pusher plate 150 by a distance X in the moving direction M, the entire pusher plate 150 in the furnace body 101 is pressed by a distance X in the moving direction M. In this embodiment, all the pusher plates 150 move synchronously, but it should be understood that a design involving asynchronous movement of the pusher plates is also contemplated, and an additional pusher assembly 160 would be required to account for such asynchronous movement.

[0043] As further shown in FIG. 1, the guide platform 140 can include gas trays 141 in the warm-up region 110, the sintering region 120, and the cooling region 130. The gas trays 141 may be part of the furnace gas flow system included in the furnace 100. The gas trays 141 can be used to supply gas to the electrochemical cell stack during the sintering process. The gas trays 141 can be connected to a gas supply line (e.g., an air and inert gas line) that conveys gas from a gas storage tank (e.g., an air and inert gas tank) to the furnace 100. The gas in the gas trays 141 can include, for example, compressed dry air (CDA) and / or nitrogen.

[0044] The gas trough 141 within the warm-up region 110 can be connected to a CDA supply unit (not shown). The CDA supply unit can provide CDA from the gas trough 141 through the opening of the pusher plate 150 into the electrochemical cell stack within each cage 200. The CDA can flow through the electrochemical cell stack 301 (e.g., through the fuel riser openings within the stack) and / or around the electrochemical cell stack 301, and then be exhausted from the electrochemical cell stack 301 into the warm-up region 110 of the furnace 100.

[0045] The guide platform 140 can also include a gas trough 141 within the sintering region 120 of the furnace 100. The gas trough 141 within the sintering region can be connected to an inert gas supply unit such as a nitrogen gas supply unit (not shown) or a reducing gas supply unit such as a forming gas supply unit (not shown). The nitrogen gas supply unit can supply nitrogen gas (e.g., pure nitrogen gas) from the gas trough 141 through the opening of the pusher plate 150 to the electrochemical cell stack 301 within each cage 200 of the sintering region (e.g., through the fuel riser opening of the stack). The nitrogen gas can also be flowed over the electrochemical cell stack 301 and then exhausted from the electrochemical cell stack into the sintering region 120 of the furnace 100.

[0046] The guide platform 140 can also include a gas trough 141 within the cooling region 130 of the furnace 100. Similar to the gas trough 141 within the warm-up region, the gas trough 141 within the cooling region 130 can be connected to a CDA gas supply unit or a reducing gas supply unit such as a forming gas supply unit. The gas supply unit can provide CDA or forming gas from the gas trough 141 within the cooling region 130 through the opening within the pusher plate 150, through and / or around the electrochemical cell stack 301 within each cage 200. Then, the CDA can be exhausted from the electrochemical cell stack 301 and enter the cooling region 130 of the furnace 100.

[0047] The furnace 100 can further include one or more compression assemblies 170. The compression assembly 170 can be located near the sintering region 120 of the furnace 100. The compression assembly 170 can be designed to apply a second (e.g., intermittent) compressive force to the electrochemical cell stack 301 within the cage 200 when the cage 200 is within the sintering region 120. The second compressive force can be greater than the first compressive force applied to the electrochemical cell stack 301 by the cage 200. For example, the second compressive load can be 300 lbm to 600 lbm, which is at least 10 times greater than the first compressive load.

[0048] FIG. 2A is a cross-sectional view of the cage 200 according to one or more embodiments. FIG. 2B is a perspective view of the cage 200 according to one or more embodiments. The cage 200 can have a cubic or rectangular parallelepiped shape. Other suitable shapes are also within the scope contemplated by the present disclosure. The cage 200 can include a cage base plate 201. The cage base plate 201 can be seated on the pusher plate 150 during the sintering process in the furnace 100. The cage 200 can also include a pair of cage side plates 202 (e.g., guide plates) attached to the cage base plate 201. The cage side plates 202 can include, for example, a pair of corner guide rails 202b (e.g., angled L-shaped bars or posts) extending upward from the corners of the side surfaces of the cage base plate 201. In particular, the cage side plates 202 can include a pair of corner guide rails 202b connected at the upper ends by horizontal rails 202a. The cage 200 can also include a cage upper plate 203 fixed to the upper surface of the cage side plates 202 and a cage weight 205. The cage upper plate 203 can be formed in a frame shape such that the upper surface of the cage weight 205 can be exposed from the cage upper plate 203. The cage 200 can have a height in the range of about 100 mm to 700 mm (e.g., 300 mm to 400 mm) and a width in the range of about 100 mm to 250 mm (e.g., 125 mm to 175 mm). Other cage heights and widths are contemplated depending on the shapes of the electrochemical cell stacks 301 and 302 housed within the cage 200.

[0049] One or more electrochemical cell stacks can be disposed within the cage 200. As shown in FIGS. 2A and 2B, the bottom electrochemical cell stack 301 can be seated on the cage base plate 201. The upper electrochemical cell stack 302 is positioned on the bottom electrochemical cell stack 301 and can be separated from the bottom electrochemical cell stack 301 by a cage spacer 204 (e.g., a stack separator). The cage weight 205 is positioned on the upper electrochemical cell stack 302. The cage weight 205 can apply a first compressive load (e.g., a constant mass) to the upper electrochemical cell stack 302 and the bottom electrochemical cell stack 301. The cage weight 205 can have a weight in the range of about 3 pounds to about 9 pounds. Although two electrochemical cell stacks 301, 302 are shown, in alternative embodiments, one or three or more stacks may be disposed within each cage 200.

[0050] The cage 200 can further include compression protrusions such as compression balls 206 on the cage weight 205. The compression balls 206 can help ensure that a second compressive load applied by the compression assembly 170 (see FIG. 1) is applied through the centers of the upper electrochemical cell stack 302 and the bottom electrochemical cell stack 301. Each of the bottom electrochemical cell stack 301, the cage spacer 204, the upper electrochemical cell stack 302, and the cage weight 205 can have a shape that substantially conforms to the inner surface of the corner guide rail 202b of the cage side plate 202. In one embodiment, the corner guide rail 202b can limit the movement (e.g., lateral movement) of the bottom electrochemical cell stack 301, the cage spacer 204, the upper electrochemical cell stack 302, and the cage weight 205.

[0051] The cage side plate 202 including the corner guide rail 202b can be composed of any suitable ceramic material such as aluminum oxide Al2O3 (i.e., alumina). The cage side plate 202 can be substantially composed of alumina such as 97% alumina. Alternatively, the cage side plate 202 may be composed of alumina with a purity of less than 97% or more than 97% purity, for example, 97% - 98%, 98% - 99%, 99% - 99.5%, 99.5% - 100%, for example, about 97%, about 98%, about 99%, or about 100%. The cage side plate 202 composed of alumina may not yield at high temperatures such as 800°C - 950°C. The cage side plate 202 composed of alumina does not electrically short-circuit the electrochemical cell stack because alumina is not conductive. Further, alumina can be suitable for strict machining tolerances that may enable control over the maximum stack tilt.

[0052] The cage base plate 201 can also be composed of any suitable ceramic material, such as alumina, for example, alumina with a purity of 97%. Alternatively, the cage base plate 201 can be composed of alumina with a purity of less than 97% or more than 97%, for example, 97% - 98%, 98% - 99%, 99% - 99.5%, 99.5% - 100%, for example, about 97%, about 98%, about 99%, or about 100%. In one embodiment, the cage base plate 201 can include one or more gas interface openings (not shown) that can be aligned with a gas manifold (not shown) within the pusher plate 150. The openings can allow gas (e.g., CDA, nitrogen gas) to pass through the pusher plate 150 and the cage base plate 201. The openings can also be aligned with the fuel riser channels of the internal electrochemical cell stack 301 to allow gas (e.g., CDA, nitrogen gas) to pass through the cage base plate 201 and enter the fuel riser channels of the electrochemical cell stack 301. In one embodiment, the cage base plate 201 can include channels or grooves (not shown) on the upper surface of the cage base plate 201. The cage base plate 201 can include a flat landing surface 201b that includes one or more recesses 201a. The cage base plate 201 is configured to support both of the cage side plates 202, while the landing surface 201b is configured to support the electrochemical cell stack 301 disposed on the cage base plate 201, as described below.

[0053] The cage spacer 204 can also be made of any suitable ceramic, such as alumina, for example, alumina with a purity of 97%. Alternatively, the cage spacer 204 can be made of alumina with a purity less than 97% or greater than 97%, for example, 97% - 98%, 98% - 99%, 99% - 99.5%, 99.5% - 100%, for example, approximately 97%, approximately 98%, approximately 99%, or approximately 100%. In one embodiment, the cage spacer 204 can include channels or grooves (not shown) on the upper and lower surfaces of the cage spacer 204. In one embodiment, the cage spacer 204 can include one or more gas interface openings (not shown) that pass through the cage spacer 204 and can be aligned with the fuel riser channels of the internal electrochemical cell stacks 301, 302. In an optional embodiment, the cage spacer 204 may be configured to function as a separator between the plurality of stacks 301, 302 of the electrochemical cells within the cage side plate 202. If only one stack (or column) 301 is provided for each cage 200, the cage spacer 204 may be omitted.

[0054] Figures 3A - 3D are perspective views of the cage 200 in a stacked configuration according to one or more embodiments. In particular, Figure 3A is a perspective view of the cage 200 at the start of stack construction according to one or more embodiments. Figure 3B is a perspective view of the cage 200 near the end of stack construction according to one or more embodiments. Figure 3C is a broken-away perspective view of Figure 3B. Figure 3D is a perspective view of the cage 200 after the completion of stack construction according to one or more embodiments.

[0055] As shown in FIG. 3A, the cage 200 can be designed such that an electrochemical cell stack (e.g., bottom electrochemical cell stack 301 and top electrochemical cell stack 302) can be directly constructed within the cage 200. At the start of stack construction, a construction platform 230 can be inserted between the cage side plates 202. The construction platform 230 can have a tuning fork shape including prongs 230a and 230b. The construction platform 230 can be attached to a vertical stage within the cage 200. A construction robot 220 (e.g., an electromechanical pick-and-place machine) can pick up individual electrochemical cells and interconnects and alternately place them on the construction platform 230 through the top of the cage 200. In one embodiment, the construction robot 220 can include a gripper that enables the construction robot 220 to grip the electrochemical cell 310 and the interconnect 311. A glass or glass-ceramic seal precursor material is also dispensed onto each cell and / or interconnect disposed within the cage 200.

[0056] As shown in FIG. 3A, the construction platform 230 can index down (as indicated by the direction arrow) as each of the electrochemical cell 310 and the interconnect 311 is placed within the cage 200 until the electrochemical cell stack is fully constructed within the cage 200 (as shown in FIGS. 3B and 3C). After the electrochemical cell stack 301 and / or 302 is constructed within the cage 200, a cage weight 205 can be inserted into the cage 200 by the construction robot 220. At this point in the assembly, the prongs 230a and 230b of the construction platform 230 can be positioned within the recess 201a of the landing surface 201b of the base plate 201. In one embodiment, the middle portion of the landing surface 201b can include the upper surface of the support rail 207. Thereafter, the prongs 230a and 230b of the construction platform 230 can be pulled laterally out of the recess 201a as shown in FIG. 3D.

[0057] Figures 4A - 4C are perspective views of cage 200 including bottom electrochemical cell stack 301 and top electrochemical cell stack 302 in different states according to one or more embodiments. In one embodiment, bottom electrochemical cell stack 301 and top electrochemical cell stack 302 may be constructed within cage 200 in one location. The cage 200 may then be transported to different locations in furnace 100 for sintering. In particular, FIG. 4A is a perspective view of cage 200 including bottom electrochemical cell stack 301 and top electrochemical cell stack 302 in a stack construction state according to one or more embodiments. Cage weight 205 may also be inserted into cage 200 to apply a first compressive load to bottom electrochemical cell stack 301 and top electrochemical cell stack 302. As shown in FIG. 4A, the upper surface 205a of cage weight 205 may include a recess 205b that can be used to support compression ball 206. At this point, after bottom electrochemical cell stack 301 and top electrochemical cell stack 302 are constructed, construction platform 230 may be removed from cage 200.

[0058] FIG. 4B is a perspective view of cage 200 including bottom electrochemical cell stack 301 and top electrochemical cell stack 302 in a transport state according to one or more embodiments. As shown in FIG. 4B, after construction platform 230 is removed, bottom electrochemical cell stack 301 either forms part of cage base plate 201 or is supported by support rails 207 positioned on cage base plate 201. Support rails 207 fit between two elongated prongs 230a, 230b of tuning fork-shaped construction platform 230. Construction platform 230 can be pulled out laterally from cage 200 without interfering with bottom electrochemical cell stack 301 positioned on support rails 207.

[0059] The stabilization device 410 can be attached to the cage upper plate 203. The stabilization device 410 can include a pressing member 411 (e.g., a screwing mechanism) that enables the stabilization device 410 to apply a pressing force onto the cage weight 205 to substantially fix the cage weight 205, the bottom electrochemical cell stack 301, and the top electrochemical cell stack 302 in a fixed position. The cage 200 that houses at least one of the electrochemical cell stack 301 and the stabilization device 410 is transported from the construction area to the furnace 100. The stabilization device 410 is removed from the cage 200 after the transportation is completed, and the cage and its contents are prepared for processing in the furnace 100.

[0060] FIG. 4C is a perspective view of a cage 200 including a bottom electrochemical cell stack 301 and a top electrochemical cell stack 302 in a sintered state according to one or more embodiments. As shown in FIG. 4C, after the cage 200 is transported to the furnace 100, the stabilization device 410 can be removed. Then, the compression ball 206 can be placed within the recess 205b. At this point, the cage 200 is placed within the furnace 100 and moved into the sintering region 120 of the furnace 100. The contact pad 176 of the compression assembly 170 pushes down on the compression ball 206 to apply a second compression load during the sintering step.

[0061] Figures 5A - 5D are various views of a stabilization device 510 having an alternative design according to one or more embodiments. The stabilization device 510 may be used during the conveyance of the cage 200 that houses one or more electrochemical cell stacks 301 from a construction area to the furnace 100. In particular, FIG. 5A is a perspective view of the cage 200 including the stabilization device 510 having an alternative design according to one or more embodiments. As shown in FIG. 5A, the stabilization device 510 having an alternative design may include a base plate 511 that is fixed to the cage upper plate 203 by one or more fastening members 512 (e.g., pins). The stabilization device 510 of FIG. 5A is shown in an engaged state that provides a downward pressure to the electrochemical cell stacks 301, 302 located within the cage 200 below the stabilization device 510.

[0062] FIG. 5B is a perspective view of the stabilization device 510 of FIG. 5A in a disengaged state. As shown in FIG. 5B, the stabilization device 510 may further include an outer cylinder (e.g., device housing) 513 fixed to the base plate 511. The stabilization device 510 may further include an inner cylinder (e.g., spring housing) 514 that is axially movable inside the outer cylinder 513. The stabilization device 510 may also include one or more spring rods 515 that are connected to the outer cylinder 513 and extend through an opening within the inner cylinder 514. A lift spring 518 may be provided around the spring rod 515. The stabilization device 510 may also include a locking pin 516 that is inserted through holes within the inner cylinder 514 and the outer cylinder 513 and can lock the inner cylinder 514 in an engaged position relative to the outer cylinder 513.

[0063] Figure 5C is a cross-sectional view of the stabilization device 510 of FIGS. 5A and 5B in the disengaged state. As shown in FIG. 5C, the stabilization device 510 can further include an alignment plate 517 connected to the end of the inner cylinder 514 and a compression spring 519 located on the alignment plate 517 within the inner cylinder 514. The bushing 520 can be located between the inner cylinder 514 and the outer cylinder 513 in the lower portion of the stabilization device 510. To place the stabilization device in the disengaged (“compression off”) state shown in FIGS. 5B and 5C, the locking pin 516 is retracted from the inner and outer cylinders. Thereby, the compression spring 519 lifts the inner cylinder 514 relative to the outer cylinder 513 and the base plate 511. Thereby, the stabilizer plate 517 (connected to the inner cylinder 514) is lifted, releasing the electrochemical cell stack(s) 301, 302 located within the lower cage 200.

[0064] Figure 5D is a cross-sectional view of the stabilization device 510 of FIG. 5A in the engaged state. As shown in FIG. 5D, an external force is applied to the inner cylinder 514 to push the inner cylinder 514 downward relative to the outer cylinder 513 and the base plate 511. Next, the locking pin 516 is inserted into the openings of the inner and outer cylinders to lock the inner cylinder 514 in the engaged (“compression on”) state relative to the outer cylinder 513 and the base plate 511. This engages the alignment plate 517 with the electrochemical cell stack(s) 301, 302 within the lower cage 200, as shown in FIGS. 5A and 5D. The compression spring 519 applies a downward pressure to the alignment plate 517 and then applies a downward pressure (i.e., compression) to the electrochemical cell stack(s) 301, 302 within the lower cage 200. The gap 521 can be located above the alignment plate 517.

[0065] Figure 5E is a perspective view of a cage 200 including a bottom electrochemical cell stack 301 and an upper electrochemical cell stack 302 in a sintered state according to one or more embodiments. As shown in Figure 5E, after the cage 200 is transported to the furnace 100, the stabilization device 510 can be removed. At this point, the cage 200 is placed within the furnace 100 and moved into the sintering region 120 of the furnace 100. The contact pads 176 of the compression assembly 170 push down on the compression balls 206 to apply a second compressive load during the sintering step.

[0066] Figures 6A and 6B are perspective views of a cage 200 having an alternative design according to one or more embodiments. Specifically, Figure 6A is a perspective view of a cage 200 having a first alternative design according to one or more embodiments. As shown in Figure 6A, the first alternative design of the cage 200 can have a 1×3 configuration. The cage 200 can include an elongated cage base plate 201 and three cage portions 200a, 200b, and 200c supported by the elongated cage base plate 201. Each cage portion 200a, 200b, and 200c is configured to support a respective electrochemical cell stack 301a, 301b, and 301c.

[0067] Figure 6B is an exploded perspective view of a cage 200 having a second alternative design according to one or more embodiments. In the second alternative design, the cage 200 can have a 1×1 design configured to support a single electrochemical cell stack 301. The cage weight 205 can seat on top of the electrochemical cell stack 301. The cage upper plate 203 can include one or more peg portions 203a extending from the bottom of the cage upper plate 203. The cage 200 can also include corner guide rails 202b that can each include one or more openings 202x (e.g., holes, recesses, etc.) that are substantially aligned with the respective peg portions 203a. The peg portions 203a can each be inserted into the openings 202x to assist in securing the cage upper plate 203 to the corner guide rails 202b.

[0068] Figures 7A and 7B are cross-sectional views of a compression assembly 170 according to one embodiment. In particular, FIG. 7A is a cross-sectional view of the compression assembly 170 in a disengaged state according to one or more embodiments. FIG. 7B is a cross-sectional view of the compression assembly 170 in an engaged state according to one or more embodiments.

[0069] As shown in FIG. 7A, the compression assembly 170 can include an actuator 171 (e.g., a pneumatic actuator) and a compression rod 174 separated from the actuator 171. The actuator 171 can be located outside the furnace body 101 (e.g., outside the housing 102) and can also be referred to as an "external actuator". The actuator 171 can be fixed in a fixed position relative to the furnace body 101. The compression assembly 170 can also include an actuator rod 173 actuated by the actuator 171. The actuator rod 173 can include an upper rod portion 173a, a lower rod portion 173b, and a connecting member 173c that joins / couples the upper rod portion 173a to the lower rod portion 173b. As shown in FIG. 7A, in the disengaged state, the upper rod portion 173a can be retracted into the actuator 171. The compression assembly 170 can be in a disengaged state (e.g., the actuator rod 173 is rising), for example, during a movement time (e.g., when the pusher plate 150 supporting the cage 200 is being pressed by the pusher assembly 160).

[0070] The compression rod 174 can extend through a sealing member 175 (e.g., a sealing gasket) within the opening of the housing 102 of the furnace body 101. The sealing member 175 can form an airtight seal within the opening. The sealing member 175 can be formed of, for example, ceramic fibers (e.g., ceramic wool) or flexible graphite. Other suitable materials are also within the scope contemplated by the present disclosure. The compression rod 174 can be formed of ceramic or other heat-resistant materials. The contact pad 176 can be attached to the lower end of the compression rod 174. The contact pad 176 can have a semi-circular groove on its bottom surface such that the compression ball 206 can fit into the groove. The contact plate 177 can be attached to the upper end of the compression rod 174.

[0071] The biasing member 178 (e.g., a spring) can be formed around the compression rod 174 between the housing 102 of the furnace body 101 and the contact plate 177. As shown in FIG. 7A, in the disengaged state, the biasing member 178 can retract the upper portion of the compression rod 174 from the housing 102 of the furnace body 101. The lower portion of the compression rod 174 including the contact pad 176 can remain inside the housing 102 of the furnace body 101 (e.g., inside the sintering region 120) in the disengaged state.

[0072] As shown in FIG. 7B, in the engaged state of the compression assembly 170, the actuator 171 pushes the actuator rod 173 out from the actuator 171 toward the contact plate 177. The lower rod portion 173b contacts the contact plate 177 and can push the lower portion of the compression rod 174 into the furnace body 101 (e.g., into the sintering region 120) against the biasing force of the biasing member 178. The length of the compression rod 174 can be accurately set such that the contact pad 176 contacts the compression ball 206 with sufficient force to apply a second compression load to the bottom electrochemical cell stack 301 and the upper electrochemical cell stack 302 located within the cage 200. The compression assembly 170 can be in an engaged state (e.g., the actuator rod 173 is lowered) during, for example, the lamp time and the dwell time (e.g., when the pusher plate 150 supporting the cage 200 is not being pressed by the pusher assembly 160). In one embodiment, the temperature of the electrochemical cell stack (e.g., the bottom electrochemical cell stack 301 and the upper electrochemical cell stack 302) can be at least the sintering temperature (e.g., at least 600° C.) before the compression assembly 170 is activated.

[0073] In at least one embodiment, the furnace 100 and / or the compression assembly 170 can be designed to reduce the risk of misalignment between the actuator rod 173 and the compression rod 174. Generally, misalignment can occur, for example, due to the thermal expansion of the furnace 100 and also, to a relatively lesser extent, due to manufacturing stack tolerances. In particular, the furnace 100 can expand from heating up to the sintering temperature. In the case of a long furnace 100 (e.g., having a length exceeding 100 feet), the amount of expansion can be very large.

[0074] Misalignment can occur in the form of a lateral misalignment where the axial direction of the compression rod 174 is parallel to but not aligned with the axial direction of the actuator rod 173. Misalignment can also occur in the form of an angular misalignment where the axial direction of the compression rod 174 is formed at an angle with respect to the axial direction of the actuator rod 173.

[0075] In at least one embodiment, to reduce the risk of misalignment (e.g., reduce the risk of failure of the compression assembly 170 due to misalignment), the actuator 171 can be structurally mounted directly to the floor (e.g., separate from the furnace 100 which can also be directly moored to the floor). The contact plate 177 can also help reduce the risk of misalignment. The contact plate 177 within the compression assembly 170 can include an area significantly larger than the cross-section of the compression rod 174. In one embodiment, the area of the contact plate 177 can be at least twice the cross-sectional area of the compression rod 174. The relatively large area of the contact plate 177 can help ensure that the actuator rod 173 actuates the compression rod 174 despite misalignment (e.g., lateral misalignment or angular deviation) between the actuator rod 173 and the contact plate 177 (e.g., can help avoid failure of the compression assembly 170).

[0076] The misalignment can increase with the distance from the mooring point of the furnace body 101. Thus, to further reduce the risk of misalignment, the furnace body 101 can be moored to the floor at the longitudinal center point of the furnace body 101. This can be referred to as central mooring of the furnace body 101. By centrally mooring the furnace body 101, the misalignment between the actuator rod 173 and the contact plate 177 can be made approximately half of the misalignment realized when the furnace body 101 is moored to the floor at the end (e.g., edge) of the furnace body 101 in the longitudinal direction.

[0077] The connecting member 173c within the actuator rod 173 can help reduce both lateral misalignment and angular misalignment. The connecting member 173c can include, for example, a floating joint or an axial shaft coupler. Other suitable types of connecting members are also within the scope contemplated by the present disclosure. The connecting member 173c (e.g., floating joint, axial shaft coupler, etc.) can help ensure that the actuator rod 173 applies a second compressive load to the bottom electrochemical cell stack 301 and the upper electrochemical cell stack 302 even when lateral misalignment or angular misalignment occurs.

[0078] FIG. 8 is a cross-sectional view of a compression assembly 170 mounted on a linear stage (e.g., actuator positioner) 800 according to one or more embodiments. To further reduce misalignment (e.g., lateral misalignment and angular misalignment), the actuator 171 (e.g., pneumatic actuator) of the compression assembly 170 can be mounted on the linear stage 800. The linear stage 800 can move back and forth in the x-direction (e.g., the moving direction M) to account for movement of the compression rod 174 in the x-direction due to thermal expansion. The linear stage 800 can have an operating range sufficient to accommodate thermal expansion of the furnace 100. The linear stage 800 can be rated for an axial load of at least 2000 N.

[0079] In one embodiment, a sensor can be used to detect the movement of the compression rod 174 and the amount of movement in the x-direction. The linear stage 800 can then be moved in the x-direction by the same amount. This can help ensure that the actuator rod 173 is substantially aligned with the compression rod 174. Alternatively, the actuator 171 mounted on the stage 800 can be moved passively along with the opening in the furnace 100 rather than simply being disengaged from the compression rod 174. In one embodiment, one or more guide pins can be provided within the furnace 100 to engage with the guide holes of the pusher plate 150 to align the pusher plate 150 under the compression rod 174. In one embodiment, the guide pins can include two conical head pins located on the side and / or below the pusher plate 150 within the furnace 100. The guide pins can be moved by a guide pin actuator when the pusher plate 150 stops moving, and the guide pins can be moved into guide holes (e.g., circular and slotted guide holes) on the side and / or bottom of the pusher plate 150. The guide pins can be retracted from the guide holes by a guide pin actuator before the pusher plate 150 moves in the moving direction within the furnace 100.

[0080] Figures 9A and 9B are cross-sectional views of alternative designs of the sealing member 175 according to one or more embodiments. In particular, FIG. 9A is a cross-sectional view of the sealing member 175 having a first alternative design according to one or more embodiments. FIG. 9B is a cross-sectional view of the sealing member 175 having a second alternative design according to one or more embodiments. The sealing member 175 can be designed such that the compression rod 174 can shift in place (e.g., shift laterally in the x-direction). By allowing movement of the sealing member 175, the sealing member 175 may be able to accommodate a certain degree of thermal expansion.

[0081] The sealing member 175 having the first alternative design of FIG. 9A can include a bushing 902 on the upper surface of the furnace housing 102. The bushing 902 can be configured to seal an opening within the furnace housing 102. The sealing member 175 can also include a tube 904 connected to the bushing 902. A layer (not shown) of ceramic fibers (e.g., ceramic wool) can be formed around the bushing 902 outside the furnace 100 and can be used to seal the opening of the furnace housing 102. In this case, the second compressive load can be applied by the compression rod 174 by advancing the compression rod 174 through the bushing 902 and the tube 904 of the sealing member 175 into the sintering region 120 of the furnace 100.

[0082] The sealing member 175 having the second alternative design of FIG. 9B can include a compression coil 912 configured to seal an opening of the furnace housing 102. The compression coil 912 can be formed, for example, from ceramic fibers (e.g., ceramic wool or ceramic rope) wound around the compression rod 174. The upper and lower portions of the compression coil 912 can be attached to a pair of plates 913 (e.g., ceramic plates). The plates 913 can be pressed against the upper and lower portions of the furnace housing 102, respectively, to compress the compression coil 912. The plates 913 can be fixed in place by one or more fastening members 914 (e.g., bolts) that can function as compression joints. In this case, the second compressive load can be applied by the compression rod 174 by advancing the compression rod 174 through the compression coil 912 and the plates 913 of the sealing member 175 into the sintering region 120 of the furnace 100.

[0083] Figures 10A and 10B are diagrams of furnace 100 according to another embodiment. The furnace 100 can include a first load lock region 1001 within a warm-up region 110. In the first load lock region 1001, the temperature within the furnace 100 can be in the range of 250°C to 350°C (e.g., about 300°C). Further, in the first load lock region 1001, the gas within the gas tray 141 of the guide platform 140 can transition from CDA to nitrogen. The first load lock region 1001 can include two doors 923a, 923b located on two respective walls 925a, 925b to help separate the CDA atmosphere and the nitrogen atmosphere from each other.

[0084] The furnace 100 can include a first sintering temperature location 1002 near the sintering chamber inlet door 123. At the first sintering temperature location 1002, the temperature within the furnace 100 can be in the range of 600°C to 1000°C. The furnace 100 can also include a second sintering temperature location 1003 near the sintering chamber outlet door 124. At the second sintering temperature location 1003, the temperature within the furnace 100 can also be in the range of 600°C to 1000°C. The furnace 100 can also include a cooling temperature location 1004 within a cooling region 130. At the cooling temperature location 1004, the temperature within the furnace 100 can be in the range of 400°C to 600°C.

[0085] The furnace 100 can also include a second load lock area 1005 within the cooling area 130. In the second load lock area 1005, the temperature inside the furnace 100 can be in the range of 400°C to 600°C. Additionally, in the second load lock area 1005, the gas in the gas trap 141 within the guide platform 140 can transition back from nitrogen to CDA. The second load lock area 1005 can include two doors 924a, 924b located on two respective walls 926a, 926b to help separate the CDA atmosphere and the nitrogen atmosphere from each other. The load lock areas 1001 and 1005 can reduce the oxygen concentration in the sintering area 120 to less than 0.005%, for example, about 0.001%. The gas pressure in the sintering area 120 can be maintained at a higher level than the gas pressure in the load lock areas 1001 and 1005 to prevent the flow of CDA from the warm-up area 110 and the cooling area 130 into the sintering area 120. In one embodiment, only one of the load lock areas 1001, 1005 can be provided within the furnace 100.

[0086] Figure 10B is a plan view of furnace 100. In Figure 10B, only the outline of furnace body 101 is shown for ease of understanding. Additionally, pusher assembly 160, compression assembly 170, and gas discharge port 107 are omitted for ease of understanding. In one embodiment, a plurality of rows of pusher plates 150 that support respective cages 200 can be positioned on guide platform 140. For example, three rows of pusher plates 150 are shown in Figure 10B. However, one row, two rows, or four or more rows of pusher plates can be positioned on guide platform 140. All rows of pusher plates 150 can move simultaneously in the moving direction M through the furnace. Alternatively, in some embodiments, the pusher plates can be moved asynchronously (as previously disclosed) to facilitate the function of the load lock area. However, even if some air leaks from heating area 110 to sintering area 120 through first load lock area 1001, the oxidation rate of the components of stack 301 is slow enough that the slightly higher air concentration at the outlet of first load lock area 1001 should not reduce the yield of stack 301. Further, in some embodiments described herein, nitrogen is directly supplied to stack 301 within sintering area 120 to offset possible air leakage from heating area 110 to sintering area 120.

[0087] As shown in Figure 10B, guide platform 140 can include a furnace feed area 140a. Furnace body feed area 140a can extend from the first end of guide platform 140 to furnace body inlet door 103 (see Figure 10A). Furnace body feed area 140a can have an ambient temperature (e.g., about 25°C). Guide platform 140 can also include a furnace discharge area 140b. Furnace discharge area 140b can extend from furnace body outlet door 104 (see Figure 10A) to the second end of guide platform 140. Furnace body discharge area 140b can have an ambient temperature (e.g., about 25°C).

[0088] The cooling region 130 of the furnace 100 can include a first cooling sub-region 130a. The first cooling sub-region 130a can extend from the second sintering temperature position 1003 to the cooling temperature position 1004. In the first cooling sub-region 130a, the temperature can decrease from a sintering temperature in the range of 600°C to 1000°C to a temperature in the range of 400°C to 600°C. The temperature change rate (dT / dt) of at least one electrochemical cell stack 301 in the first cooling sub-region 130a can be in the range of -1°C / min to -5°C / min (for example, about -2°C / min).

[0089] The cooling region 130 of the furnace 100 can also include a second cooling sub-region 130b. The second cooling sub-region 130b can extend from the cooling temperature position 1004 to the outlet door 104 of the furnace body 101 (see FIG. 10A). The second cooling sub-region 130b can include the second load lock region 1005. In the second cooling sub-region 130b, the temperature can decrease from a temperature in the range of 400°C to 600°C to the ambient temperature (for example, about 25°C). The temperature change rate (dT / dt) in the second cooling sub-region 130b may be smaller than the temperature change rate (dT / dt) in the first cooling sub-region 130a. In one embodiment, the temperature change rate (dT / dt) in the second cooling sub-region 130b can also be in the range of -1°C / min to -5°C / min (for example, about -1°C / min).

[0090] As further shown in FIG. 10B, the furnace 100 can include a plurality of atmosphere sections 1010. The plurality of atmosphere sections 1010 can include a first warm-up region atmosphere section 1011 starting from the furnace body inlet door 103 (see FIG. 10A). The first warm-up region atmosphere section 1011 can include an air atmosphere (for example, a CDA atmosphere). The plurality of atmosphere sections 1010 can also include a second warm-up region atmosphere section 1012 spanning the first load lock region 1001. The second warm-up region atmosphere section 1012 can include an atmosphere that transitions from air to nitrogen.

[0091] The plurality of atmosphere sections 1010 can also include a warm-up / sintering atmosphere section 1013 that spans the warm-up region 110 and the sintering region 120. The warm-up / sintering atmosphere section 1013 can include a transitional nitrogen atmosphere in which the concentration of nitrogen increases in the moving direction M. The plurality of atmosphere sections 1010 can also include a sintering / cooling atmosphere section 1014 that spans the sintering region 120 and the first cooling sub-region 130a. The sintering / cooling atmosphere section 1014 can include a transitional nitrogen atmosphere in which the concentration of nitrogen decreases in the moving direction M.

[0092] The plurality of atmosphere sections 1010 can also include a first cooling atmosphere section 1015 that spans the first cooling sub-region 130a and the second cooling sub-region 130b. The first cooling atmosphere section 1015 can include a cooling temperature position 1004. The first cooling atmosphere section 1015 can also include a transitional nitrogen atmosphere in which the concentration of nitrogen decreases in the moving direction M.

[0093] The plurality of atmosphere sections 1010 can also include a second cooling atmosphere section 1016 that spans the second load lock region 1005. The second cooling atmosphere section 1016 can include an atmosphere that transitions from nitrogen to air. The plurality of atmosphere sections 1010 can also include a third cooling atmosphere section 1017 that extends from the second cooling atmosphere section 1016 to the furnace body outlet door 104 (see FIG. 10A). The third cooling atmosphere section 1017 can include an air atmosphere.

[0094] Figures 11A - 11C are various views of furnace 100 including gas flow system 1100 according to one or more embodiments. In particular, FIG. 11A is a perspective view of guide platform 140 including at least a portion of gas flow system 1100 according to one or more embodiments. Guide platform 140 can include one or more inlet gas ports (not shown) connected to inner gas line 1101. Inner gas line 1101 can include one or more air inner gas lines 1101A that supply CDA to gas trough 141 and one or more nitrogen inner gas lines 1101N that supply nitrogen to gas trough 141.

[0095] As further shown in FIG. 11A, a plurality of cages 200 can be aligned in the y - direction on pusher plate 150 positioned on guide platform 140. The cages can include a first cage 200a, a second cage 200b, and a third cage 200c. Gas trough 141 can extend in the movement direction M (i.e., the x - direction) along the surface of the guide platform and can include a first gas trough 141a for supplying gas to the first cage 200a, a second gas trough 141b for supplying gas to the second cage 200b, and a third gas trough 141c for supplying gas to the third cage 200c.

[0096] Air inner gas line 1101A extends in the y - direction under the surface of guide platform 140 and can intersect each of the first gas trough 141a, the second gas trough 141b, and the third gas trough 141c. Nitrogen inner gas line 1101N also extends in the y - direction under the surface of guide platform 140 and can intersect each of the first gas trough 141a, the second gas trough 141b, and the third gas trough 141c.

[0097] Nitrogen and air can fill the first gas trough 141a, the second gas trough 141b, and the third gas trough 141c. As shown by the direction arrows in FIG. 11A, the nitrogen gas from the nitrogen inner gas line 1101N can flow in both directions in the x direction. That is, nitrogen can flow towards the first load lock region 1001 and also flow away from the first load lock region 1001. Similarly, the air from the air inner gas line 1101A can flow in both directions in the x direction. That is, air can flow towards the first load lock region 1001 and also flow away from the first load lock region 1001. Nitrogen and air flow through separate troughs to avoid their mixing. The CDA trough and the nitrogen (or reducing gas) trough are separated by a stopper, a plug or a similar separator between different furnace regions.

[0098] FIG. 11B is a perspective view of a guide platform 140 including a gas trough 141 of the gas flow system 1100 of FIG. 11A. Note that FIG. 11B is a view seen from the opposite side of the cage 200 shown in FIG. 11A. The bottom electrochemical cell stack 301 and the upper electrochemical cell stack 302 are omitted from FIG. 11B for ease of understanding.

[0099] As shown in FIG. 11B, nitrogen (indicated by the direction arrow) in the first gastrough 141a flows under the pusher plate 150a that supports the first cage 200a. Due to the pressure of the nitrogen in the first gastrough 141a, the nitrogen is introduced through the pusher plate 150a and the cage base plate 201a into the bottom electrochemical cell stack 301 (not shown), and provided through the spacer 204a into the upper electrochemical cell stack 302 (not shown). Similarly, nitrogen (indicated by the direction arrow) in the second gastrough 141b flows under the pusher plate 150b that supports the second cage 200b. Due to the pressure of the nitrogen in the second gastrough 141b, the nitrogen is introduced through the pusher plate 150b and the cage base plate 201b into the bottom electrochemical cell stack 301 (not shown), and provided through the spacer 204b into the upper electrochemical cell stack 302 (not shown). Similarly, nitrogen (indicated by the direction arrow) in the third gastrough 141c flows under the pusher plate 150c that supports the third cage 200c. Due to the pressure of the nitrogen in the third gastrough 141c, the nitrogen is introduced through the pusher plate 150c and the cage base plate 201c into the bottom electrochemical cell stack 301 (not shown), and provided through the spacer 204c into the upper electrochemical cell stack 302 (not shown).

[0100] FIG. 11C is a cross-sectional view of a second cage 200b including a gas flow path of the gas flow system 1100 according to an embodiment. As shown in FIG. 11C, nitrogen flows in the second gastrough 141b under the pusher plate 150b. The pusher plate 150b can include one or more tabs 150t that overlap or underlap tabs on the adjacent pusher plate 150 in the moving direction M. These tabs 150t can help seal the interface between the pusher plate 150b and the adjacent pusher plate 150 on the second gastrough 141b.

[0101] As further shown in FIG. 11C, the nitrogen in the second gastrough 141b enters the inlet manifold 150im of the pusher plate 150b, passes through the inlet manifold 201im of the cage base plate 201b, enters the fuel inlet riser opening 301ir in the stack 301, and can be provided into the fuel inlet riser opening 302ir of the upper electrochemical cell stack 302 through the inlet manifold 204im of the spacer 204b.

[0102] As further shown by the direction arrows in FIG. 11C, the nitrogen from the fuel inlet riser opening 301ir of the bottom electrochemical cell stack 301 can flow between the individual electrochemical cells in the fuel channels of the bottom electrochemical cell stack 301 and enter the fuel outlet riser opening 301or of the bottom electrochemical cell stack 301. The nitrogen from the fuel inlet riser opening 302ir of the upper electrochemical cell stack 302 can flow between the individual electrochemical cells in the fuel channels of the upper electrochemical cell stack 302, enter the fuel outlet riser opening 302or in the stack of the upper electrochemical cell stack 302, pass through the outlet manifold 204om of the spacer 204b, and enter the fuel outlet riser opening 301or of the bottom electrochemical cell stack 301. The nitrogen in the fuel outlet riser opening 301or of the bottom electrochemical cell stack 301 can then enter the outlet manifold 201om of the cage base plate 201b and flow into the exhaust manifold 150em of the pusher plate 150b, where it is exhausted into the internal volume (e.g., the sintering chamber 120) of the housing 102 of the furnace 100. Thereafter, the nitrogen exits the housing via the gas discharge port 107 (see FIG. 1).

[0103] The guide platform 140 can alternatively or additionally include one or more nitrogen supply ports (not shown) in the sintering region 120. The nitrogen supply ports can be connected to the same nitrogen inner gas line 1101N that supplies nitrogen to the gas tray 141. The nitrogen supply ports can be blocked during the transfer time (e.g., while the pusher assembly 160 is activated) and can maximize the direct nitrogen flow into the stack 301 during the dwell time. Alternatively, when the load lock region separates the air atmosphere and the nitrogen atmosphere into different regions, the nitrogen supply ports can be turned on during the transfer time. The nitrogen supply ports can be located under the pusher plate 150 within the sintering region 120. The nitrogen supply ports can be spaced apart at each pitch length within the sintering region 120. The nitrogen supply ports can direct nitrogen upward into the gas flow path described with reference to FIG. 11C (e.g., into the inlet manifold 150im, then into the inlet manifold 201im, etc.).

[0104] The guide platform 140 can alternatively or additionally include one or more nitrogen exhaust ports (not shown) within the sintering region 120 and a nitrogen exhaust line (not shown). The nitrogen exhaust line can be connected to a furnace exhaust line that exhausts nitrogen from the furnace 100. The nitrogen exhaust ports can be located under the pusher plate 150 adjacent to the nitrogen supply ports within the sintering region 120. The nitrogen exhaust ports can also be spaced apart at each pitch length in the sintering region 120. In this case, the exhaust manifold 150em can be designed to send nitrogen from the pusher plate 150 to the nitrogen exhaust ports, the nitrogen exhaust line, and the furnace exhaust line.

[0105] FIG. 12 is a cross-sectional view of a compression assembly 170 having an alternative design according to an alternative embodiment. As shown in FIG. 12, the alternative design of the compression assembly 170 can include gas flow paths for flowing nitrogen to an electrochemical cell stack (e.g., bottom electrochemical cell stack 301 and top electrochemical cell stack 302). The alternative design of the compression assembly 170 may be utilized instead of, or in addition to, the gas flow system shown in FIGS. 11A-11C.

[0106] As shown in FIG. 12, the compression rod 174 can include a nitrogen inlet port 1201 and a nitrogen outlet port 1202. The compression rod 174 can also include a nitrogen supply line 174i connected to the nitrogen inlet port 1201 and a nitrogen exhaust line 174o connected to the nitrogen outlet port 1202.

[0107] When the compression assembly 170 is activated, the actuator rod 173 can press the compression rod 174 to push down the cage 200. For example, the compression rod 174 can contact a cage weight (e.g., the compression ball 206 portion of the cage weight 205) to push down the stack 301 located within the cage 200. The cage weight 205 can include a nitrogen inlet line 205i that couples to the nitrogen supply line 174i and a nitrogen outlet line 205o that couples to the nitrogen exhaust line 174o. A substantially airtight contact seal can be formed between the compression rod 174 and the cage weight 205. Thus, during the dwell time when the compression rod 174 is applying a second compression load to the cage weight 205, nitrogen may be provided from the nitrogen supply line 174i into the nitrogen inlet line 205i of the cage weight 205. During the travel time, the compression rod 174 can be retracted and the nitrogen supply to the nitrogen inlet port 1201 can be turned off.

[0108] As further indicated by the direction arrows of FIG. 12, nitrogen can then be provided into the upper electrochemical cell stack 302 and the bottom electrochemical cell stack 301 along a gas flow path similar to the gas flow path described above with respect to FIG. 11C, except that nitrogen first enters the upper electrochemical cell stack 302 instead of the bottom electrochemical cell stack 301. Nitrogen can exit the upper electrochemical cell stack 302, enter the nitrogen outlet line 205o within the cage weight 205, then enter the nitrogen exhaust line 174o of the compression rod 174, and then exit the compression rod 174 through the nitrogen outlet port 1202.

[0109] One exemplary method of sintering an electrochemical cell stack includes placing the electrochemical cell stack 301 within a cage 200 that applies a first compressive load to the electrochemical cell stack, moving the cage 200 that houses the electrochemical cell stack 301 in a moving direction M through a furnace 100 that includes a sintering region 120, sintering the electrochemical cell stack 301 within the sintering region 120 of the furnace 100, and applying a second compressive load to the electrochemical cell stack 301 that is greater than the first compressive load during sintering.

[0110] In an alternative embodiment, applying the second compressive load includes intermittently applying the second compressive load using a plurality of compression rods 174 that protrude into the sintering region 120.

[0111] Figures 13A through 13G show an exemplary movement cycle sequence of steps in which the electrochemical cell stack 301 receives a second compressive load from each of the compression rods 174 as the electrochemical cell stack 301 passes downward in the direction of movement. The first step includes moving a first cage 200A that houses the electrochemical cell stack 301 from an initial position shown in FIG. 13A to a first position within the sintering region 120. The movement of the cage 200A is shown in FIG. 13B, and the arrival of the cage at the first position is shown in FIG. 13C. The second step includes lowering a first compression rod 174A of the plurality of compression rods to apply a second compressive load to the electrochemical cell stack 301 while the cage 200A is located at the first position, as shown in FIG. 13C. The third step includes raising the first compression rod 174A to release the second compressive load from the electrochemical cell stack, and after raising the first compression rod, moving the cage that houses the electrochemical cell stack in the direction of movement as shown in FIG. 13D to a second position within the sintering region as shown in FIG. 13E. Meanwhile, a second cage 200B that houses another electrochemical cell stack 301A moves to the first position. The fourth step includes lowering a second compression rod 174B of the plurality of compression rods 174 to apply a second compressive load to the electrochemical cell stack 301 while the cage 200A is located at the second position. The fourth step also includes lowering the first compression rod 174A to apply a second compressive load to the electrochemical cell stack 301 located within the second cage 200B while the second cage 200B is located at the first position. The fifth step includes raising the second compression rod 174B to release the second compressive load from the electrochemical cell stack 301, and after raising the second compression rod, moving the cage 200A that houses the electrochemical cell stack 301 in the direction of movement as shown in FIG. 13F to a third position within the sintering region as shown in FIG. 13G. The sixth step includes lowering a third compression rod 174C of the plurality of compression rods 174 to apply a second compressive load to the electrochemical cell stack 301 while the cage 200A is located at the third position, as shown in FIG. 13G.The second compressive loads applied by the first compression rod and the second compression rod may be equal to or different from each other.

[0112] Figures 14A - 14E show a plurality of movement cycles in which the electrochemical cell stack 301 receives a second compressive load from only a part, but not all, of the compression rods 174 through which the electrochemical cell stack 301 passes downward in the moving direction. The first step includes moving the first cage 200A that houses the electrochemical cell stack 301 from the initial position shown in Figure 14A toward the first position within the sintering region 120. The movement of the cage 200A is shown in Figure 14B. However, in this embodiment, the first compression rod 174A does not descend and does not apply a second compressive load to the electrochemical cell stack 301. Instead, in the second step, while the first cage 200A is moved from the first position to the second position, a second cage 200B that houses another electrochemical cell stack 301 is moved to the first position. The movement of the cages 200A and 200B is shown in Figure 14C. The first compression rod 174A and the second compression rod 174B do not descend and do not apply a second compressive load to the electrochemical cell stacks 301 located within the first cage 200A and the second cage 200B. Instead, in the third step, the first cage 200A is moved from the second position to the third position, the second cage 200B is moved from the first position to the second position, and a third cage 200C that houses yet another electrochemical cell stack 301 is moved to the first position. The movement of the cages is shown in Figure 14D. In the fourth step, the first compression rod 174A, the second compression rod 174B, and the third compression rod 174C apply a second compressive load to the respective electrochemical cell stacks 301 located within their respective third cage 200C, second cage 200B, and first cage 200A, as shown in Figure 14E. The plurality of movement cycle sequences of the steps enables larger batches of the electrochemical cell stack 301 to be processed per furnace residence cycle while reducing the delay in the sintering process. Thereby, the residence time can be increased, and the quality of the sintering of the electrochemical cell stack 301 can be improved. In this embodiment, the load lock may be wider than the embodiment of the single movement cycle sequence of the steps in Figures 13A - 13G in order to simultaneously accommodate a plurality of cages 200 arranged in a row in the moving direction.

[0113] A series of steps of intermittently applying a second compressive load using a plurality of compression rods involves moving a first cage 200A that houses a first electrochemical cell stack 301 beyond a first position and a second position within a sintering region without applying the second compressive load to the first electrochemical cell stack, while moving the first cage 200A to a third position within the sintering region, and also moving a second cage 200B that houses a second electrochemical cell stack 301 beyond the first position to the second position, and moving a third cage 200C that houses a third electrochemical cell stack 301 to the first position. The method also includes lowering a first compression rod 174A, a second compression rod 174B, and a third compression rod 174C among the plurality of compression rods 174 while the first cage 200A is located at the third position, the second cage 200B is located at the second position, and the third cage 200C is located at the third position, and then applying the second compressive load to each of the third electrochemical cell stack 301, the second electrochemical cell stack 301, and the first electrochemical cell stack 301. The method further includes raising the first compression rod 174A, the second compression rod 174B, and the third compression rod 174C to release the second compressive load from each of the third electrochemical cell stack 301, the second electrochemical cell stack 301, and the first electrochemical cell stack 301, and after raising each of the third compression rod, the second compression rod, and the first compression rod, moving the first cage 200A in the moving direction to pass through a fourth position and a fifth position and move to a sixth position within the sintering region, while also moving the second cage 200B in the moving direction to pass through the fourth position and move to the fifth position, and moving the third cage 200C to the fourth position.

[0114] During sintering of the electrochemical cell stack, the electrochemical cell stack is heated to at least one of a melting or reflow glass temperature (or a glass-ceramic seal precursor material) located between the stack's interconnects and the electrochemical cells to form a glass or glass-ceramic seal between each of the electrochemical cells in the electrochemical cell stack and two adjacent interconnects. The sintered stack is then removed from the cage and placed into an electrochemical cell system such as a fuel cell system or an electrolyzer system.

[0115] The pusher assembly 160 may be referred to as an indexing conveyance system or a furnace indexer. The cycle time of the furnace indexer may be referred to as the indexer cycle time. The indexer cycle may include a dwell portion where the electrochemical cell stack (e.g., the bottom electrochemical cell stack 301 and the top electrochemical cell stack 302) in the furnace 100 is stationary, and a moving portion where the electrochemical cell stack is moving (e.g., being pushed by the pusher assembly 160).

[0116] The indexer cycle time t index is given as the sum of a ramp-up time t ramp-up , a dwell time t dwell , a ramp-down time t ramp-down , and a move time t move (t index = t ramp-up + t dwell + t ramp-down + (move-cycles * t move )). In one embodiment, the dwell time t dwell may be greater (e.g., much greater) than the move time t move . The move time refers to the time required for the cage supporting the electrochemical cell stack to move forward by one pitch length (e.g., from a first position under the first compression rod 174A in the furnace 100 to a second position under the second compression rod 174B). In one embodiment, the dwell time t dwell may be in the range of about 5 minutes to about 40 minutes (e.g., 15 minutes to 25 minutes), while the move time tmove should be within the range of about 5 seconds to about 100 seconds (for example, 20 seconds to 80 seconds). For example, in the single movement cycle sequence of the steps in FIGS. 13A to 13G, the residence time may be 5 minutes to 10 minutes, and the movement time may be 20 seconds to 30 seconds. In contrast, in the multiple movement cycle sequence of the steps in FIGS. 14A to 14E, the residence time may be 15 minutes to 25 minutes, and the movement time may be 70 seconds to 80 seconds. The movement time is multiplied by the number of movement cycles "move - cycles", where the movement cycle is defined as the number of times the indexer moves before the compression load is applied. For example, the number of movement cycles in the embodiment of FIGS. 13A to 13G is 1, and the number of movement cycles in the embodiment of FIGS. 14A to 14E is 3. The ramp - up time t ramp-up is defined as the time required for the compression load to reach its set value from zero. The ramp - down time t ramp-down is defined as the time required for the compression load to reach zero from its set value. The electrochemical cell stack 301 or set of stacks located within each cage 200 can enter and exit the furnace 100 after each indexer cycle. When a plurality of rows of cages 200 are supported by the guide platform 140, the plurality of cages 200 can enter and exit the furnace 100. The electrochemical cell stack 301 may be assembled inside the cage 200 while the cage 200 is located outside the furnace 100. Then, the cage 200 containing the electrochemical cell stack is transferred to and from the furnace 100 via an electromechanical device (for example, a robotic arm, a gantry robot, etc.) for each indexer cycle.

[0117] In one embodiment, the step of moving the electrochemical cell stack is performed over a plurality of cycles including a cycle ramp-up time, a cycle dwell time, a cycle ramp-down time, and a cycle move time. The step of applying the second compressive load is performed during the cycle ramp-up time, the cycle dwell time, and the cycle ramp-down time in the sintering region, but not during the cycle move time. The compressive load increases from zero to a predetermined value during the ramp-up time, is held at the predetermined value during the dwell time, and decreases from the predetermined value to zero during the ramp-down time. The step of moving the cage is performed during the move time, but not during the cycle ramp-up time, the cycle dwell time, and the cycle ramp-down time.

[0118] The electrochemical cell stack or set of stacks located within each cage 200 can enter and exit the furnace 100 after each indexer cycle. When a plurality of rows of cages 200 are supported by the guide platform 140, the plurality of cages 200 can enter and exit the furnace. The electrochemical cell stack may be assembled inside the cage 200 while the cage 200 is located outside the furnace 100. Then, the cage 200 containing the electrochemical cell stack is transferred to and from the furnace 100 via an electromechanical device (e.g., a robotic arm, a gantry robot, etc.) for each indexer cycle.

[0119] The second compression load may be incrementally applied to the electrochemical cell stacks 301, 302 within the furnace 100. The application of the second compression load may be linear or non-linear. A linear variable differential transformer (LVDT) sensor can be used to measure and monitor the compression of the electrochemical cell stack within the furnace. In the electrochemical cell stack within the furnace 100, a constant mass (e.g., the first compression load) may be continuously applied to the electrochemical cell stack for low force compression. The constant mass may consist of the weight 205, or a metal rod having an outer ceramic layer, or any other load mass. Depending on the desired compression force, the metal rod can have a height in the range of 100 mm to 300 mm. The metal rod may include a steel rod or a rod of a material denser than steel (e.g., lead, tungsten, etc.).

[0120] The compression assembly 170 can include one actuator 171 per cage 200 (e.g., when the cage 200 has a 1×1 design (see FIG. 6B)), or multiple actuators 171 per cage 200 (e.g., when the cage 200 has a 3×1 design (see FIG. 6A)) for each pitch length within the sintering region 120. Further, the actuator-to-cage ratio can also be modified to allow for multiple movement cycles. The actuator 171 may be stationary, and the compression may be performed via a compression rod 174 that slides through a sealing member 175 within the housing 102 of the furnace body 101. The compression rod can retract when a pusher assembly 160 (e.g., an indexer) moves the electrochemical cell stack within the furnace 100.

[0121] Each electrochemical cell stack can be processed in furnace 100 for a total of about 300 to about 600 minutes. During this time, the position of the electrochemical cell stack can change over time in a stepped manner where the electrochemical cell stack moves 1 step in the moving direction M and then stops during the residence time, repeating this. In addition, the first compression load may be continuously provided to each of the electrochemical cell stacks in the warm-up region 110, the sintering region 120, and the cooling region 130, while the second compression load is intermittently applied only during the residence time and not during the moving time, within the sintering region 120. The total number of actuators 171 can depend on the residence time t dwell . When the residence time is relatively long (i.e., when the cage 200 takes a longer time to be sintered while under the load from each actuator), fewer actuators per row are required to provide the desired total sintering time within the furnace. In contrast, when the residence time is relatively short, more actuators per row are present to provide the same desired total sintering time within the furnace. For example, a residence time t dwell of 20 minutes can correspond to about 12 actuators per row (48 actuators in total), and a residence time t dwell of 5 minutes can correspond to about 48 actuators per row (144 actuators in total). In one embodiment, furnace 100 can include an indexer cycle that includes a residence time t dwell of 20 minutes and a moving time t move of 30 seconds.

[0122] The furnace 100 can include a periodic gas flow and / or a continuous gas flow. The sintering process can include a sufficient level of internal nitrogen flow (e.g., ultra-high purity nitrogen (>99.9%)) to ensure that oxidation does not occur inside the electrochemical cell stack. In one embodiment, the gas trough 141 may route nitrogen to the electrochemical cell stack only during the residence time or, optionally, during both the residence time and the travel time. Alternatively or additionally, the interior of the sintering chamber 120 of the housing of the furnace 100 may be filled with nitrogen. In one embodiment, the nitrogen may be preheated in the furnace 100 before entering the electrochemical cell stack.

[0123] FIGS. 15A and 15B are a perspective view and a side cross-sectional view of a stabilization device 1510 according to an alternative embodiment of the present disclosure. The stabilization device 1510 differs from the above-described stabilization devices 410 and 510 in that the stabilization device 1510 can be used during both the conveyance and sintering of the electrochemical cell stacks 301, 302.

[0124] In this alternative embodiment, the stabilization device 1510 can include ceramic components made of a ceramic material such as alumina, stabilized zirconia, etc., that can withstand the sintering temperature within the furnace 100. Further, the stabilization device 1510 can include the above-described ceramic compression rod 174. The compression rod 174 of this alternative embodiment may be detached from the actuator 171 of the compression assembly 170 as described above with respect to FIGS. 7A, 7B, and 8.

[0125] The stabilization device 1510 also includes a ceramic upper restraint plate 1552, at least one ceramic spring 1554, and a ceramic locking nut 1556. The stabilization device 1510 can also optionally include a ceramic shim 1558. The restraint plate 1552 is supported by the upper portion of the cage 200. The restraint plate 1552 has a width that is narrower than the central portion of the restraint plate 1552 and houses side protrusions 1553 that project through the openings 1562 on the sides of the cage 200.

[0126] The compression rod 174 extends through the central opening 1586 of the upper restraint plate 1552. The central opening 1586 may or may not have internal threads. The ceramic spring 1554 can include one or more ceramic leaf springs. In one embodiment, the ceramic spring 1554 includes a ceramic leaf spring pack as described in U.S. Patent No. 8,785,074, issued July 22, 2014, which is hereby incorporated by reference in its entirety. The ceramic locking nut 1556 includes any suitable internally threaded ceramic nut. The compression rod 174 may have internal threads such that the compression rod 174 is threaded into the locking nut 1556. The locking nut 1556 prevents the compression rod 174 from rising and disengaging from the upper restraint plate 1552.

[0127] In this embodiment, the cage weight 205 may be provided on top of the upper electrochemical cell stack 302. Alternatively, the cage weight 205 may be omitted. Further, if at least one ceramic spring 1554 and / or ceramic shim 1558 is present, the compression ball 206 can also be omitted. The ceramic shim 1558 can include any suitable ceramic plate or block that is narrower than at least one ceramic spring 1554 and is positioned under the ceramic spring 1554. The shim 1558 prevents direct contact between the ceramic spring 1554 and the flat surface of the cage weight 205 or the upper electrochemical cell stack 302 positioned under the shim 1558.

[0128] To attach the restraint plate 1552 to the cage 200, a ceramic stabilization bracket 1560 can be provided. The stabilization bracket 1560 comprises a ceramic plate configured to be positioned on the side surface of the cage 200. Each stabilization bracket 1560 comprises an opening 1562, such as a groove or a recess, that fits over each side projection 1553 of the upper restraint plate 1552. Each stabilization bracket 1560 also comprises at least one peg 1564 that fits into each opening of the cage 200. For example, each stabilization bracket 1560 comprises four pegs 1564, as shown in FIGS. 15A and 15B.

[0129] FIGS. 15C, 15D, and 15E are perspective views of a cage 200 including at least one electrochemical cell stack 302 and a stabilization device 1510 in different states according to one or more embodiments. FIG. 15C is a perspective view of a cage 200 housing at least one electrochemical cell stack 302 and a stabilization device 1510 in an unsintered transport state according to an alternative embodiment. The stabilization device 1510 can be attached to the cage 200 using the stabilization brackets 1560. Each side projection 1553 of the upper restraint plate 1552 is inserted into each opening 1562 of each stabilization bracket 1560. The pegs 1564 of the stabilization brackets 1560 are inserted into each opening of the cage 200 to lock the stabilization device 1510 to the cage 200. The cage 200 housing at least one electrochemical cell stack 302 and the stabilization device 1510 is transported from the construction area to the furnace 100.

[0130] FIG. 15D is a perspective view of a cage 200 and a stabilization device 1510 in a sintered state according to an alternative embodiment. A cage 200 that houses at least one electrochemical cell stack 302 and a stabilization device 1510 is inserted into a furnace 100 without removing the stabilization device 1510 from the cage 200. However, the stabilization bracket 1560 may be removed before moving the cage 200 through the furnace 100. An actuator 171 of a compression assembly 170 compresses a compression rod 174 during a sintering step within the furnace 100, as described above with respect to FIGS. 7A, 7B, and 8.

[0131] FIG. 15E is a perspective view of a cage 200 and a stabilization device 1510 in a sintering transport state according to an alternative embodiment. Specifically, a cage 200 that houses at least one sintered electrochemical stack 302 and a stabilization device 1510 is removed from the furnace 100 and transported to the next location (e.g., an electrochemical system manufacturing area or a storage area) without removing the stabilization device 1510. The restraint plate 1552 and the locking nut 1556 can be raised relative to at least one ceramic spring 1554 in a sintering transport state. The stabilization bracket 1560 can be attached onto the cage 200 and the stabilization device 1510 before transporting the cage 200 away from the furnace 200. Each step of removing and attaching the stabilization device 1510 before and after sintering may be omitted in this alternative embodiment, thus simplifying the overall manufacturing process.

[0132] FIGS. 16A and 16B are a perspective view and a side cross-sectional view of a cage 200 that houses a stabilization device 1610 according to another alternative embodiment of the present disclosure. The stabilization device 1610 can be used during both the transport and sintering of the electrochemical cell stacks 301, 302 in a manner similar to the stabilization device 1510 described above with respect to FIGS. 15C - 15E. The stabilization device 1610 is different from the stabilization device 1510 in a plurality of different aspects described below.

[0133] The stabilization device 1610 does not require the above-described ceramic leaf spring 1554, optional shim 1558, or optional stabilization bracket 1560. The stabilization device 1610 includes a ceramic restraint plate 1652 and a ceramic locking nut 1656. The restraint plate 1652 is supported by the upper portion of the cage 200. The restraint plate 1652 has a narrower width than the upper portion of the restraint plate 1652 and houses a bottom protrusion 1653 that protrudes downward from the upper portion of the restraint plate 1652. The bottom protrusion 1653 is inserted into a recess 202r in the upper portion of the horizontal rail 202a of the cage side plate 202 to attach the stabilization device 1610 to the cage 200. The restraint plate 1652 can also be pinned to the cage side plate 202 using a ceramic pin 1660.

[0134] The stabilization device 1610 also includes a ceramic guide block 1670. The guide block 1670 can include a hexagonal portion 1672, a wider lower portion 1674, and an internally threaded opening 1676 that can extend continuously through the hexagonal portion 1672 and the lower portion 1674. The compression rod 174 extends through the inner opening 1676 of the guide block 1670 and applies pressure to a cage weight 205 located below the guide block 1670. In this embodiment, the cage weight 205 includes a recess 205r that houses the bottom tip of the compression rod 174. Alternatively, the cage weight 205 can include the above-described compression ball 206 that fits into the groove of the contact pad 176 of the compression rod 174, as described in the previous embodiment.

[0135] To apply the compressive load, the compression rod 174 is screwed in by rotating the guide block 1670 while holding it in place at a predetermined position on the upper flat portion until the compression rod 174 contacts the cage weight 205. The ceramic thrust bearing 1684 allows the guide block 1670 to rotate while a compressive load is being applied to the ceramic restraint plate 1652 during this process. In this embodiment, the locking nut 1656 is positioned above the restraint plate 1652 and is screwed onto the male thread of the compression rod 174. Thus, the locking nut 1656 and the lower portion 1674 of the guide block 1670 lock the compression rod against the restraint plate 1652. The restraint plate 1652 guides the vertical movement of the guide block 1670 at their interface 1686 during the sintering process due to the reduction in the heights of stacks 301 and 302.

[0136] Figures 17A and 17B are a perspective view and a side cross-sectional view of a cage 200 housing a stabilization device 1710 according to yet another alternative embodiment of the present disclosure. The stabilization device 1710 is different from the stabilization device 1610 in a plurality of different respects described below.

[0137] The stabilization device 1710 includes a spring housing 1770 instead of the guide block 1670 described above. The spring housing 1770 can include a hollow ceramic cylinder. The compression rod 174 extends through the hollow portion of the spring housing 1770. A biasing member 1778 (e.g., a ceramic spring) surrounds the compression rod 174 inside the spring housing 1770, similar to the biasing member 178 described above with respect to FIGS. 7A and 7B.

[0138] The spring housing 1770 also includes one or more restraint tabs 1772 located at the lower part of the outer surface of the spring housing 1770. The restraint tabs 1772 include ceramic protrusions that extend radially away from the outer wall of the spring housing 1770. At least one of the restraint tabs 1172 includes a tab opening 1774 that extends through the entire thickness of the restraint tab 1772.

[0139] In this embodiment, an upper restraint block 1750 is provided instead of the restraint plate 1652. The upper restraint block 1750 includes an upper plate portion 1752 and a lower plate portion 1754 separated by a groove 1714. The upper restraint block 1750 also houses the aforementioned bottom protrusion 1653, which has a width narrower than that of the upper plate portion 1752 of the upper restraint block 1750 and protrudes below the lower plate portion 1754 of the upper restraint block 1750. The bottom protrusion 1653 is inserted into a recess 202r in the upper portion of the horizontal rail 202a of the cage side plate 202 to attach the stabilization device 1710 to the cage 200.

[0140] The central opening 1686 extends through both the upper plate portion 1752 and the lower plate portion 1754 of the upper restraint block 1750. The upper portion of the central opening 1686 that extends through the upper plate portion 1752 includes one or more slots 1686S that extend radially away from the center of the central opening 1686. The upper restraint block 1750 also includes at least one opening 1712 that extends through the entire thickness of the upper plate portion 1752 to the groove 1714.

[0141] To engage the stabilization device 1710 with the electrochemical cell stacks 301, 302 located within the lower cage 200, the spring housing 1770 and the compression rod 174 are lowered through the central opening 1686 in the upper restraint block 1750 such that the compression rod 174 compresses the cage weight 205. The restraint tabs 1772 are lowered through their respective slots 1686S such that each restraint tab 1772 is positioned within the groove 1714 between the upper and lower plate portions of the upper restraint block 1750. Next, the spring housing 1770 is rotated axially to rotate the tabs 1772 within the groove 1714 and align the tab openings 1774 of the tabs 1772 with the openings 1712 in the upper plate portion 1752 of the upper restraint block 1750. Next, the locking pin 1716 is lowered through the openings 1712 in the upper plate portion 1752 of the upper restraint block 1750 and the tab openings 1774 to secure the spring housing 1770 to the upper restraint block 1750 in a fixed position above the cage 200. The bottom of the spring housing 1770 may rest on the upper surface of the lower plate portion 1754.

[0142] The stabilization device 1710 can be used during the sintering of the electrochemical cell stacks 301, 302 located within the cage 200. To remove the stabilization device 1710 from the cage 200 after sintering, the locking pin 1716 is raised, the spring housing 1770 is rotated to align the lock tabs 1772 with the slots 1686S, and the spring housing 1770 and the compression rod 174 are lifted away from the cage 200.

[0143] A method of sintering an electrochemical cell stack 301 and / or 302 of an alternative embodiment of FIGS. 15A-15E, FIGS. 16A and 16B and / or FIGS. 17A and 17B includes, after placing the electrochemical cell stack within cage 200, attaching a stabilization device 1510, 1610, or 1710 that houses compression rod 174 to cage 200, and transporting cage 200 that houses stabilization device 1510, 1610, or 1710 and electrochemical cell stack 301 and / or 302 to furnace 100. The method also includes using an actuator 171 located outside furnace 100 and removably coupled to compression rod 174 to lower compression rod 174 toward electrochemical cell stacks 301, 302 within sintering region 120 to apply a second compressive load to electrochemical cell stacks 301, 302 during sintering. The method also includes transporting cage 200 that houses stabilization device 1510, 1610, or 1710 and electrochemical cell stacks 301, 302 away from furnace 100 (e.g., to another location such as a storage area or a system construction area). The stabilization device is not removed from the cage during and between the two transport steps and the sintering step.

[0144] FIGS. 18A-18C illustrate a method of cyclic compression in furnace 100 according to one or more embodiments. In particular, FIG. 18A is a schematic perspective view of the arrangement of compression assembly 170 within sintering region 120 of furnace 100 according to another embodiment. FIG. 18B is a schematic perspective view of the steps of a compression cycle (CC) according to the embodiment of FIG. 18A. FIG. 18C is a graph showing the level of force applied to the columns of electrochemical cell stacks 301, 302 during the stages of compression cycle (CC) in the embodiments of FIGS. 18A and 18B. Note that in FIGS. 18A and 18B, compression assembly 170 is shown in a simplified form and various elements of cage 200 and furnace 100 are omitted for ease of illustration.

[0145] Referring to FIG. 18A, the sintering region 120 of the furnace 100 can include four compression stations 1851-1854 that house four pusher plates 150, and each pusher plate 150 supports a plurality (e.g., two or more, e.g., two to six, e.g., three) of columns of the electrochemical cell stacks 301, 302. More or fewer pusher plates 150 may be housed in the sintering region 120. The pusher plates 150 may contact each other when pressed in the moving direction (M) inside and outside the sintering region 120.

[0146] The sintering region 120 can include rows of a plurality of compression assemblies 170. The number of compression assemblies 170 in each row is equal to the number of columns of the electrochemical cell stacks 301, 302 supported on the pusher plate 150. For example, each of the compression stations 1851-1854 in the sintering region 120 may have two or more, e.g., two to six, e.g., three compression assemblies 170. In FIG. 18A, the compression assemblies 170 are shown in an engaged state. The compression assembly 170 can include an actuator 171 (e.g., a pneumatic actuator) located outside the furnace 100, a compression rod 174 that can be driven inside and outside the furnace housing 102 by the actuator 171, and a contact pad 176 at the end of the compression rod 174 that applies pressure to the columns of the electrochemical cell stacks 301, 302.

[0147] The spacing of the actuators 171 of the compression assemblies 170 can correspond to the spacing of the columns of the electrochemical cell stacks 301, 302 within the sintering region 120. In one embodiment, the actuators 171 may be evenly spaced within the sintering region 120. In particular, the actuators 171 may be separated by a first distance D1 in the x direction (e.g., the moving direction (M)) and a second distance D2 in the y direction corresponding to the separation distance between the columns of the electrochemical cell stacks 301, 302.

[0148] Referring again to FIGS. 18B and 18C, the compression assembly 170 can perform periodic compression of the electrochemical cell stacks 301, 302 in the sintering region 120. The periodic compression cycle can include four phases (e.g., steps), namely, a movement period 1801, a force ramp-up 1802, a dwell period 1803, and a force ramp-down 1804. In FIG. 18B, it should be noted that only one pusher plate 150 and only one compression assembly 170 are shown for each of the phases for ease of illustration. The four phases of the compression cycle can be performed simultaneously by all of the compression assemblies 170 within the sintering region 120.

[0149] The graph of FIG. 18C shows the force applied over time to the electrochemical cell stacks 301, 302 by the compression assembly 170 for four compression cycles. During the movement period 1801, the pusher plate 150 that supports the columns of the electrochemical cell stacks 301, 302 can be moved to a position below each compression assembly 170. In the force ramp-up 1802, while the electrochemical cell stacks 301, 302 are stationary (e.g., the pusher plate 150 is stationary), the actuator 171 of the compression assembly 170 can decline relatively rapidly with a relatively weak force until direct or indirect contact with the column (e.g., direct contact with the column, or indirect contact via an element located on the column such as the compression ball 206 described above) occurs. Once direct or indirect contact with the column is confirmed, the compression force is increased as a function of time until the maximum force value is reached and a high compression load is applied. During the dwell period 1803 (e.g., waiting period), the compression assembly 170 can apply a substantially constant compression force (e.g., high compression load) to the columns of the electrochemical cell stacks 301, 302. In the force ramp-down 1804 after the dwell period 1803 is completed, the actuator 171 can decrease the compression force applied to the columns of the electrochemical cell stacks 301, 302 over time by retracting the compression rod 174 upward. At the end of the force ramp-down 1804, no compression force is applied to the electrochemical cell stacks 301, 302 by the compression assembly 170. The time corresponding to the ramp-up curve 1802 can be different from the time corresponding to the ramp-down curve 1804. For example, the ramp-down curve 1804 may be shorter in time than the ramp-up curve 1802.

[0150] In one embodiment, the pusher plate 150 can be advanced into and out of the sintering region 120 one pusher plate 150 at a time for each compression cycle. In this case, the furnace 100 can be designed such that the total number of actuators 171 multiplied by the length of the residence period is equal to the total required sintering time. Thus, for example, the four-row pusher plates 150 of FIG. 18A can be advanced into the sintering region 120 one at a time such that each pusher plate 150 can receive four consecutive compression cycles (CC), as shown in FIG. 18C. In this case, the duration of the compression cycle CC may be substantially equal to 1 / 4 of the total required sintering time. In one embodiment, the total sintering time may be in the range of 1 hour to 4 hours.

[0151] In an alternative embodiment, multiple pusher plates 150 can be advanced into and out of the sintering region 120 of the furnace 100 during each compression cycle (CC). In this case, the duration of each compression cycle (CC) may be substantially the same as the total sintering time required for the electrochemical cell stacks 301, 302. For example, the four pusher plates 150 of FIG. 18A can be advanced into the sintering region 120 together. Then, one compression cycle CC can be continuously performed over the entire required sintering time. Then, the four pusher plates 150 can be advanced out of the sintering region 120 together.

[0152] FIG. 19 shows additional details of the stages of a compression cycle (CC) according to one embodiment of the present disclosure. A weak initial contact force is applied to the compression rod 174 while the compression rod is being lowered and contacting the columns of the electrochemical cell stacks 301, 302 directly or indirectly (i.e., either contacting the columns directly or contacting the columns indirectly via the compression balls 206). Subsequently, after it is determined that the compression rod 174 is properly in direct or indirect contact with the columns of the electrochemical cell stacks 301, 302 (e.g., the compression rod 174 is in contact with the compression balls 206 above the columns of the electrochemical cell stacks 301, 302), the compression force on the compression rod 174 is increased.

[0153] The compression cycle (CC) of FIG. 19 can be substantially the same as the compression cycles of FIGS. 18B and 18C. The compression cycle can include the movement period 1801, force ramp-up 1802, dwell period 1803, and force ramp-down 1804 shown in FIGS. 18B and 18C. However, FIG. 19 further shows a "soft touch" step 1801A and a compression rod lift step 1804A.

[0154] During the movement period 1801 (i.e., the movement phase), the cage 200 on the pusher plate 150 is moved to the next compression station. During the force ramp-up 1802 (i.e., compression ramp-up), it can be confirmed that the contact pad 176 on the compression rod 174 is in contact with the compression ball 206 (i.e., the alignment ball), and the force can increase at a ramp-up speed set by the compression profile as shown in FIG. 18C. During the dwell period 1803 (compression hold), the compression assembly 170 can hold the set point compression load. During the force ramp-down 1804 (i.e., compression ramp-down), the compression assembly 170 can decrease the compression load at a ramp-down speed set by the compression profile. During the compression rod lift step 1804A, the compression rod 174 can be removed from the compression ball 206. In the compression rod lift step 1804A, there may be no limit to the speed at which the compression rod 174 is lifted by the actuator 171, and there may be no limit to the force applied to the compression rod 174 by the actuator 171.

[0155] Applying a strong force to compress ball 206 (or cage weight 205 if the compress ball 206 is omitted) may cause cracks in the electrochemical cells of the electrochemical cell stacks 301, 302. The soft touch step 1801A can be included between the movement period 1801 and the force ramp-up 1802 to reduce the risk of cracking the electrochemical cell due to a strong impact force. In the soft touch step 1801A, the contact pad 176 of the compression assembly 170 can be gently contacted with the compress ball 206 with a weak impact force. In particular, in the soft touch step 1801A, the actuator 171 can drive the compression rod 174 downward by a drop at a relatively high speed but with a weak force so that the contact pad 176 gently contacts the compress ball 206. For example, the force during the soft touch step 1801A may be in the range of 1 pound to 100 pounds, while the force during the dwell time 1803 may be in the range of 300 pounds to 600 pounds.

[0156] The extra time required to ensure a weak impact force by the compression rod on the electrochemical cell stacks 301, 302 during the soft touch step 1801A is the soft touch time t st which may be referred to as. In the compression cycle (CC) of FIG. 19, the index time t i (e.g., the process time for one pusher plate 150 to complete the CC) depends on the total sintering time required to sinter the stack. Considering the soft touch time t st , the index time t i can be given by the following. t i =t m +(t st +t ru +t c +t rd +t rr ) Here, t m is the movement time during stage 1801 (e.g., the time for the pusher plate 150 to move forward by one position), and t ruis the ramp-up time during step 1802 (e.g., the time required for the compression assembly 170 to exert the full compression load), and t c is the compression time during step 1803 (e.g., the time during which the static full compression load is applied to the electrochemical cell stacks 301, 302), and t rd is the ramp-down time during step 1804 (e.g., the time required for the compression assembly 170 to reduce the full compression load to zero compression load), and t rr is the rod return time (e.g., the time required for the compression rod 174 to return to a position where it will not interfere with the movement of the cage 200 in step 1804A).

[0157] The method for determining the soft touch time t st can be based on the process control method used in the sintering operation. In particular, in open loop control, the soft touch time t st can be a fixed time that ensures that only a weak impact force is provided. Using velocity feedback control, the soft touch time t st can be determined by the measured decrease in the compression rod velocity indicating contact with the compression ball 206. Using force feedback control, the soft touch time t st can be determined by a force sensor indicating compression rod contact with the compression ball 206.

[0158] FIG. 20 shows potential alignment issues associated with the compression assembly 170 according to a comparative embodiment. In the sintering region 120 of the furnace 100, there can be a risk of misalignment both within the compression assembly 170 and between the compression assembly 170 and the cage 200. Misalignment can be caused by multiple factors such as variations in the size or design of one or more elements within the furnace 100, movement of the furnace housing 102 due to thermal expansion, etc.

[0159] Figure 20 shows a first misalignment risk (A) and a second misalignment risk (B). The first misalignment risk (A) may include misalignment between the actuator rod 173 (e.g., the lower rod portion 173b of the actuator rod 173) and the compression rod 174 (e.g., the contact plate 177 on the compression rod 174). The first misalignment risk (A) may be caused by the compression rod 174 moving with the furnace 100 as the furnace 100 expands due to heating. In particular, the thermal expansion of the furnace housing 102 may cause a shift in the position of the opening in the furnace housing 102 where the compression rod 174 of the compression assembly 170 can slide back and forth during the compression cycle (CC). The first misalignment risk (A) may also be caused by installation variations between the actuator rod 173 and the compression rod 174, or by component size variations (e.g., the size of the contact plate 177 and / or the size of the lower rod portion 173b may vary from the designed size).

[0160] The second misalignment risk (B) may include misalignment between the compression rod 174 (e.g., the contact pad 176 on the compression rod 174) and the compression ball 206 (or the cage weight 205 if the compression ball 206 is omitted). The second misalignment risk (B) may be caused by variations in the position of the pusher plate 150 associated with each pressing from the pusher assembly 160 (see FIG. 1) (e.g., the pusher plate 150 may stop at different locations after each indexing movement). The second misalignment risk (B) may also be caused by variations in component size.

[0161] One or more methods can be used to reduce the risk of misalignment within furnace 100. For example, actuator 171 of compression assembly 170 can be mounted on a compliant mount (e.g., movable linear stage 800) as shown in FIG. 8. This allows actuator 171 to move with the holes in furnace housing 102 during thermal expansion. Compression ball 206 can also help reduce the risk of misalignment by allowing only the vertical component of the force from compression rod 174 to be transmitted to electrochemical cell stacks 301, 302.

[0162] In addition to methods for reducing the risk of misalignment, furnace 100 can also include one or more mechanisms for detecting misalignment and / or measuring the degree of misalignment, and the misalignment can then be corrected by the furnace operator based on the measured data. In one embodiment, active electronic position sensing can be used to detect the alignment of compression rod 174 with the upper part of electrochemical cell stacks 301, 302 within cage 200. The position sensing can be performed within sintering region 120 of furnace 100 using an alignment device such as a laser interferometer sensor including a capacitance displacement sensor or an optical detector (e.g., a camera). Other types of position sensing are also within the scope contemplated by the present disclosure.

[0163] FIGS. 21A and 21B show a capacitance displacement sensor 2100 for detecting misalignment and / or measuring the degree of misalignment according to one embodiment. Sensor 2100 includes at least one capacitive probe 2101, or preferably two probes 2101 and 2102, attached to compression rod 174, and at least one conductive element 2103 attached to cage 200. For example, conductive element 2103 can comprise a metal bar attached to the inner surface of ceramic cage upper plate 203.

[0164] The sensor 2100 can capacitively measure the degree of misalignment between the compression rod 174 and the center of the cage 200 by measuring the capacitance between the conductive element 2103 and the probes 2101, 2102. The measured misalignment may be corrected, for example, by repositioning the actuator 171, adjusting the positioning of the pusher plate 150, adjusting the positioning of the cage 200 on the pusher plate 150, and the like.

[0165] Figures 22A and 22B are schematic views of a thermal uniformity measurement tool 250 according to one or more embodiments. Figure 22A is a perspective view of a thermal uniformity measurement tool 250 according to one or more embodiments. Figure 22B is a top view of a thermal uniformity measurement tool 250 according to one or more embodiments.

[0166] The Thermal Uniformity Measurement (TUM) tool 250 can be used during the testing and qualification of the furnace 100 to measure the thermal uniformity of the electrochemical cell stacks 301, 302 during operation of the furnace 100. To measure the thermal uniformity, the TUM tool 250 may be placed on the test pusher plate 150T next to the pusher plate 150 that supports the rows of the cage 200 housing the electrochemical cell stacks 301, 302. While the furnace 100 is operating, the test pusher plate 150T with the TUM tool 250 can be pushed through the furnace 100 together with one or more cages 200 on the pusher plate 150 to approximate actual furnace sintering conditions. The TUM tool 250 may be connected by wiring 250W to temperature sensors TS200 (e.g., thermocouples) within or near the electrochemical cell stacks 301, 302 located within the cage 200. The temperature sensors TS200 can generate a temperature-dependent voltage that represents the temperature distribution within the electrochemical cell stacks 301, 302. The TUM tool 250 can also include an outer casing 251 of a thermal barrier that surrounds the electronics (e.g., data logger) of the TUM tool 250 and various sensors. The TUM tool 250 can include a Datapaq™ Oven Tracker thermal profiling system commercially available from Fluke Process Instruments, or another suitable thermal profiling system.

[0167] FIG. 23 is a schematic perspective view of a furnace 100 including a camera 2300 according to another embodiment of the present disclosure. As shown in FIG. 23, the furnace housing 102 within the sintering region 120 of the furnace 100 can include one or more windows 2305. Each window 2305 can be formed from, for example, quartz or other high-temperature resistant material. The window 2305 can provide a field of view from the outside of the furnace 100 to the inside of the sintering region 120. In particular, the window 2305 can provide a view of the operation of the compression assembly 170 within the sintering region 120.

[0168] The window 2305 may be, for example, one or more small port holes. For thermal uniformity evaluation, one or more windows 2305 may be provided in each temperature zone. For alignment checking, one or more of the windows 2305 may be provided at each compression station 1851 - 1854 shown in FIG. 18A.

[0169] The furnace 100 may also include a camera 2300 (e.g., an image capture device) positioned adjacent to each window 2305. Alternatively, the camera 2300 may be present at only some of the windows 2305. The camera 2300 can include a still camera and / or a video camera. The camera 2300 may be an infrared (IR) camera or a visible light camera that captures images within the sintering region 120. In particular, the camera 2300 may be an IR camera that can perform thermal imaging of the cage 200 and the electrochemical cell stacks 301, 302 within the cage 200 to determine their temperature distribution and uniformity as a function of their height and / or width.

[0170] Alternatively, the camera 2300 can include a visible or IR camera that images the operation of the compression assembly 170 to ensure that the compression assembly 170 is properly aligned with the electrochemical cell stacks 301, 302 (e.g., to determine whether the compression rod 174 collides with the center of the stack and / or the compression ball 206 above the center of the stack).

[0171] Camera 2300 may be connected to the furnace control system 2500 by a wired or wireless data connection 2300W. The camera 2300 can generate still images and / or video images that can be converted by a computer 2511 into a display signal that generates a display on the display device 2513 of the furnace control system 2500. The display can provide an operator looking at the display with an image (e.g., a thermal image) within the sintering region 120. The operator can then use the input device 2512 of the furnace control system 2500 (or, alternatively, the display device 2513 if it includes a touch screen) to control the operation of the furnace based on the image.

[0172] The foregoing description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the described embodiments. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the scope of the disclosure. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.

Claims

1. A method for sintering an electrochemical cell stack, comprising: placing the electrochemical cell stack in a cage that applies a first compressive load to the electrochemical cell stack; moving the cage containing the electrochemical cell stack in a moving direction through a furnace including a sintering region; sintering the electrochemical cell stack in the sintering region of the furnace; applying a second compressive load greater than the first compressive load to the electrochemical cell stack during the sintering; The method as described above.

2. The moving of the cage containing the electrochemical cell stack is carried out over a plurality of cycles including a cycle ramp-up time, a cycle dwell time, a cycle ramp-down time, and a cycle moving time, The applying of the second compressive load is carried out at least during the cycle dwell time in the sintering region, but not during the cycle moving time. The compressive load is increased from zero to a predetermined value, held at the predetermined value, and decreased from the predetermined value to zero, The moving of the cage is carried out during the moving time, but not during the cycle ramp-up time, the cycle dwell time, and the cycle ramp-down time. The method according to Claim 1.

3. The applying of the second compressive load is carried out during the cycle ramp-up time, the cycle dwell time, and the cycle ramp-down time. The compressive load is increased from zero to a predetermined value during the ramp-up time, held at the predetermined value during the dwell time, and decreased from the predetermined value to zero during the ramp-down time. The method according to Claim 2.

4. The applying of the second compressive load includes intermittently applying the second compressive load using a plurality of compression rods protruding into the sintering region. The method according to Claim 1.

5. The intermittently applying of the second compressive load using the plurality of compression rods includes: moving the cage containing the electrochemical cell stack to a first position within the sintering region; while the cage is in the first position, lowering at least a first compression rod among the plurality of compression rods to apply the second compressive load to the electrochemical cell stack within the cage; raising the first compression rod to release the second compression load from the electrochemical cell stack; after raising the first compression rod, moving the cage that houses the electrochemical cell stack in the moving direction to a second position within the sintering region; while the cage is positioned at the second position, lowering at least a second compression rod of the plurality of compression rods to apply the second compression load to the electrochemical cell stack within the cage; raising the second compression rod to release the second compression load from the electrochemical cell stack; after raising the second compression rod, moving the cage that houses the electrochemical cell stack in the moving direction to a third position within the sintering region; The method according to claim 4, comprising:

6. The sintering region of the furnace includes an opening sealed by a sealing member configured to move laterally to accommodate thermal expansion of the furnace, and applying the second compression load includes advancing a portion of the first compression rod into the sintering region through the sealing member. The method according to claim 5.

7. The sealing member includes a bushing that seals the opening and a tube connected to the bushing, and applying the second compression load includes advancing a portion of the first compression rod into the sintering region through the bushing and the tube of the sealing member. The method according to claim 6.

8. The sealing member includes a compression coil that seals the opening, and applying the second compression load includes advancing a portion of the first compression rod into the sintering region through the compression coil of the sealing member. The method according to claim 6.

9. Applying the second compression load includes using an actuator located outside the furnace and removably coupled to the first compression rod to advance a portion of the first compression rod into the sintering region. The method according to claim 5.

10. The first compression rod includes a spring-loaded compression rod biased by a spring so as to be in a retracted state, and applying the second compression load includes pushing a part of the first compression rod into the sintering region against the biasing of the spring using the actuator, the method according to claim 9.

11. The actuator includes a pneumatic actuator mounted on a linear stage, and applying the second compression load includes moving the linear stage so as to accommodate thermal expansion of the furnace, the method according to claim 9.

12. The actuator is fixed in a fixed position relative to the furnace, the first compression rod includes a contact plate configured to accommodate thermal expansion of the furnace, and applying the second compression load includes bringing the contact plate into contact with the actuator, the method according to claim 9.

13. The cage housing the electrochemical cell stack includes a first cage, and the electrochemical cell stack includes a first electrochemical cell stack. Intermittently applying the second compression load using the plurality of compression rods Moving the first cage housing the first electrochemical cell stack to a third position within the sintering region beyond a first position and a second position within the sintering region without applying the second compression load to the first electrochemical cell stack, while also moving a second cage housing a second electrochemical cell stack to the second position beyond the first position, and moving a third cage housing a third electrochemical cell stack to the first position. While the first cage is located at the third position, the second cage is located at the second position, and the third cage is located at the third position, lowering a first compression rod, a second compression rod, and a third compression rod among the plurality of compression rods, and applying the second compression load to the third electrochemical cell stack, the second electrochemical cell stack, and the first electrochemical cell stack, respectively. Raising the first compression rod, the second compression rod, and the third compression rod to release the second compression load from the third electrochemical cell stack, the second electrochemical cell stack, and the first electrochemical cell stack, respectively. After raising each of the third compression rod, the second compression rod, and the first compression rod, while moving the first cage in the moving direction through a fourth position and a fifth position to a sixth position within the sintering region, the second cage is also moved in the moving direction through the fourth position to the fifth position, and the third cage is also moved to the fourth position. The method according to claim 4, comprising the above.

14. Before sintering the electrochemical cell stack, gradually raising the temperature of the electrochemical cell stack in a warm-up region of the furnace where the temperature gradually increases along with the distance in the moving direction. After sintering the electrochemical cell stack, gradually lowering the temperature of the electrochemical cell stack in a cooling region of the furnace where the temperature gradually decreases along with the distance in the moving direction. The method according to claim 1, further comprising the above.

15. Flowing compressed dry air (CDA) through or over the electrochemical cell stack in the warm-up region and the cooling region. Flowing nitrogen or forming gas through the electrochemical cell stack in the sintering region. The method according to claim 14, further comprising the above.

16. Moving the cage includes pressing the cage on a pusher plate through the furnace using an external actuator. Flowing the CDA includes flowing the CDA into the electrochemical cell stack through a manifold in the pusher plate. Flowing the nitrogen or forming gas includes flowing the nitrogen or forming gas into the electrochemical cell stack through the manifold in the pusher plate. The sintering region is a sintering chamber, and includes a first door through which the electrochemical cell stack passes when entering the sintering chamber from the warm-up region, and a second door through which the electrochemical cell stack passes when exiting the sintering chamber and entering the cooling region, and is provided with a sintering chamber. Flowing the nitrogen or forming gas into the sintering region further includes maintaining an environment with a high nitrogen content in the sintering chamber during sintering of the electrochemical cell stack. The method according to claim 15.

17. The electrochemical cell stack comprises an alternating stack of interconnects and electrochemical cells, wherein the electrochemical cell includes a fuel cell or an electrolytic cell, The method according to claim 1, wherein sintering the electrochemical cell stack includes heating the electrochemical cell stack to at least one of a temperature for melting or reflowing a glass or glass-ceramic seal precursor material to form a glass or glass-ceramic seal between each of the electrochemical cells in the electrochemical cell stack and two adjacent interconnects.

18. After disposing the electrochemical cell stack in the cage, attaching to the cage a stabilization device that houses a compression rod, transporting the cage that houses the stabilization device and the electrochemical cell stack to the furnace, using an actuator located outside the furnace and removably coupled to the compression rod to lower the compression rod toward the electrochemical cell stack in the sintering region to apply the second compression load to the electrochemical cell stack during sintering, transporting the cage that houses the stabilization device and the electrochemical cell stack away from the furnace, The method according to claim 1, further comprising:

19. Lowering at least the first compression rod includes lowering the first compression rod with a first force until the first compression rod directly or indirectly contacts the electrochemical cell stack in the cage, and subsequently increasing the force applied to the electrochemical cell stack by the first compression rod after the first compression rod directly or indirectly contacts the electrochemical cell stack. The method according to claim 5.

20. The method according to claim 5, further comprising measuring displacement of the first compression rod relative to the center of the cage using a camera or a capacitance displacement sensor.

21. The method according to claim 5, further comprising measuring a temperature distribution of the electrochemical cell stack located in the furnace using an infrared camera positioned outside the furnace adjacent to a window in the furnace.

22. Testing the furnace further includes performing a measurement of the thermal uniformity of the electrochemical cell stack within the cage in the furnace by using a thermal uniformity tool that is electrically connected to at least one thermocouple located within or adjacent to the electrochemical cell stack.

23. A furnace comprising: A furnace body including a sintering region; A pusher assembly configured to press a cage that houses an electrochemical cell stack sintered within the furnace body, the cage being configured to apply a first compressive load to the electrochemical cell stack; A compression assembly located within the sintering region of the furnace body and configured to apply a second compressive load greater than the first compressive load to the electrochemical cell stack; The furnace comprising the above components.

24. The compression assembly includes: A sealing member configured to seal each opening of the sintering region of the furnace body; A plurality of compression rods protruding into the sintering region through each of the sealing members; A plurality of actuators located outside the furnace body and removably coupled to each of the plurality of compression rods; The furnace according to Claim 23, comprising the above components.

25. A guide platform including a gas trough configured to convey gas; A pusher plate configured to convey the cage that houses the electrochemical cell stack by sliding it along the surface of the guide platform; The furnace according to Claim 23, further comprising the above components.

26. The pusher plate is aligned with the anode inlet of the gas trough and the electrochemical cell stack, and includes a pusher plate manifold configured to flow gas from the gas trough to the anode inlet of the electrochemical cell stack. The furnace according to Claim 25.

27. At least one load lock region located in the path between the inlet to the furnace body and the sintering region; At least one load lock region located in the path between the sintering region and the outlet from the furnace body; The furnace according to Claim 23, further comprising the above components.

28. The furnace body further includes a plurality of heating regions within it. A part of the plurality of heating regions is configured to gradually increase the temperature of the electrochemical cell stack as the electrochemical cell stack moves toward the sintering region, a part of the plurality of heating regions is configured to maintain the temperature of the electrochemical cell stack within a predetermined temperature range in the sintering region, and a part of the plurality of heating regions is configured to gradually decrease the temperature of the electrochemical cell stack as the electrochemical cell stack moves away from the sintering region. The furnace according to claim 23.

29. The furnace according to claim 23, further comprising a capacitance displacement sensor configured to measure the alignment of the compression assembly with the cage.

30. The furnace according to claim 23, further comprising a window configured to enable viewing the inside of the furnace from the outside of the furnace, and a camera positioned adjacent to the window and configured to capture an image of the inside of the furnace through the window.

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