ELECTROCHEMICAL DEVICES THAT INCLUDE SEALING STRUCTURES
TECHNICAL FIELD
[0001] This invention generally relates to the joining of a ceramic and a
metal part using glass and active braze alloys. In some specific embodiments, the invention relates to using an intermediate structure having a glass composition along with an active braze alloy to provide strong sealing between components used at high temperatures, e.g., thermal rechargeable batteries.
BACKGROUND OF THE INVENTION
[0002] A variety of electrochemical devices require processes and
compositions for providing seals on or within the devices. The seals may be used to encapsulate the entire device, or they may separate various chambers within the device. As an example, many types of seal materials have been considered for use in high-temperature rechargeable batteries/cells for joining different components.
[0003] Sodium/sulfur or sodium/metal halides are good examples of high-
temperature batteries that may include a variety of ceramic and metal components. The ceramic components often include an electrically insulating alpha-alumina collar, and an ion-conductive electrolyte beta-alumina tube, and are generally joined or bonded via a sealing glass. The metal components usually include a metallic casing, current collector components, and other metallic components which are often joined by welding or thermal compression bonding (TCB). While mechanisms for sealing these components are currently available, their use can sometimes present some difficulty. For example, metal-to-ceramic bonding can be challenging, due to thermal stress caused by a mismatch in the coefficient of thermal expansion for the ceramic and metal components.

[0004] The metal-to ceramic bonding is most important for the reliability
and safety of the high-temperature cells. Many types of seal materials and sealing processes have been considered for joining metal to ceramic components, including ceramic adhesives, brazing, and sintering. However, most of the seals may not be able to withstand high temperatures and corrosive environments.
[0005] A common bonding technique for joining ceramic and metal
components involves multiple steps of metalizing the ceramic component, followed by bonding the metallized ceramic component to the metal component using a thermal compression bond (TCB). The bond strength of such metal-to-ceramic joints is controlled by a wide range of variables. A large number of these variables are associated with the metallization process, such as, ceramic density, particle size, metallization temperature, time, atmosphere, to name a few. In addition to this, the TCB process is a batch process and cannot be scaled up to large scale manufacturing. Therefore, it is desirable to develop a joining method that can eliminate the metallization process, and that is generally continuous in design, so as to allow a large manufacturing through-put. In order to ensure good bond strength, the processes of the prior art often require close control of several parameters involved in various process steps. In short, the prior art methods can be relatively expensive, and complicated, in view of the multiple processing steps, and the difficulty in controlling the processing steps.
[0006] Brazing is another potential technique for making the ceramic-to-
metal joints. A braze material is heated above its melting point, and distributed between two or more close-fitting parts by capillary action. However, most of the commercially available brazing materials (or braze materials) have limitations that prevent them from fulfilling all of the necessary requirements of high temperature batteries. Moreover, some of the commercial braze materials can be quite expensive themselves; and using them efficiently in various processes can also be costly. Nonetheless, brazing techniques remain of considerable interest for joining ceramic and metallic parts in various high-temperature devices.

[0007] In view of some of these challenges, it may be desirable to develop
new compositions and methods that have characteristics that meet performance requirements for high temperature rechargeable batteries, and are less complicated and less expensive to process, as compared to the existing sealing methods.
BRIEF DESCRIPTION
[0008] In one embodiment of the invention, an electrochemical cell is
presented. The cell includes a first component, a second component, and an intermediate structure disposed between the first component and the second component. The first component includes alpha alumina and the second component includes nickel. The intermediate structure includes a glass and an active braze alloy. The glass is present in an amount between about 17 volume percent and about 60 volume percent of the intermediate structure, and the active braze alloy includes an active metal element in an amount less than about 10 weight percent of the active braze alloy.
[0009] One embodiment of the invention is related to a battery that
includes a plurality of interconnected electrochemical cells. Each of the electrochemical cells includes a ceramic collar formed of alpha alumina, a metal ring formed of nickel, and a sealing structure in between the ceramic collar and the metal ring. The sealing structure includes a glass and an active braze alloy. The glass is present in an amount between about 17 volume percent and about 60 volume percent of the composition of the intermediate structure, and the active braze alloy includes an active metal element in an amount less than about 10 weight percent of the active braze alloy.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a schematic view showing a cross-section of an
electrochemical cell, according to some embodiments of this invention;

[0011] FIG. 2 is a diagrammatical representation of an intermediate
structure of the joint between a ceramic component and a metal component of an electrochemical cell, according to some embodiments of this invention;
[0012] FIG. 3 is micrograph depicting an arrangement of an active braze
alloy and glass compositions in an intermediate structure, according to a specific embodiment of this invention; and
[0013] FIG. 4 is diagrammatical representations of different physical
arrangements of an active braze alloy and glass compositions in an intermediate structure, according to a specific embodiment of this invention.
DETAILED DESCRIPTION
[0014] The invention includes embodiments that relate to a structure
including a glass and an active braze alloy layer for providing various types of seals. Non-limiting examples of the applications that require these kinds of seals include various electrochemical cells, e.g., those in a sodium/sulfur or a sodium metal halide battery. The invention also includes embodiments that relate to devices made by using the active braze alloy compositions along with glass.
[0015] As discussed in detail below, some of the embodiments of the
present invention include a glass, along with an active braze alloy for sealing a ceramic component to a metal component, e.g., in an electrochemical cell; along with a metal halide battery formed thereof. These embodiments advantageously provide an improved seal and method for the sealing. Although the present discussion provides examples in the context of a metal halide battery, these processes can be applied to any other application, including ceramic-to-metal or ceramic-to-ceramic joining.
[0016] When introducing elements of various embodiments of the present
invention, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements, unless otherwise indicated. The terms

"comprising," "including," and "having" are intended to be inclusive, and mean that there may be additional elements other than the listed elements. Unless otherwise indicated herein, the terms "disposed on", "deposited on", or "disposed between", refer to both direct contact between layers, objects, and the like, or indirect contact, e.g., having intervening layers there between.
[0017] Approximating language, as used herein throughout the
specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it may be related. Accordingly, a value modified by a term such as "about" is not limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value.
[0018] FIG. 1 is a schematic diagram depicting an exemplary embodiment
of a sodium-metal halide battery cell 10. The cell 10 has an ion-conductive separator tube 20 disposed in a cell case 30. The separator tube 20 is usually made of P-alumina or P"-alumina. The tube 20 defines an anodic chamber 40 between the cell case 30 and the tube 20, and a cathodic chamber 50, inside the tube 20. The anodic chamber 40 is usually filled with an anodic material 45, e.g. sodium. The cathodic chamber 50 contains a cathode material 55 (e.g. nickel and sodium chloride), and a molten electrolyte, usually sodium chloroaluminate (NaAlC14).
[0019] An electrically insulating ceramic collar 60, which may be made of
alpha-alumina, is situated at a top end 70 of the tube 20. A cathode current collector assembly 80 is disposed in the cathode chamber 50, with a cap structure 90, in the top region of the cell. The ceramic collar 60 is fitted onto the top end 70 of the separator tube 20, and is sealed by a glass seal 100. In one embodiment, the collar 60 includes an upper portion 62, and a lower inner portion 64 that abuts against an inner wall of the tube 20, as illustrated in FIG. 1.

[0020] In order to seal the cell 10 at the top end (i.e., its upper region), a
metal ring 110 is sometimes disposed. The metal ring 110 may have two portions; an outer metal ring 120 and an inner metal ring 130, which are joined, respectively, with the upper portion 62 and the lower portion 64 of the ceramic collar 60, by means of the seals 140 and 150, including active braze alloys.
[0021] The seal 140, the seal 150, or both may include suitable active
braze alloy compositions, such as those described in pending Patent Applications 13/407870, filed on February 29, 2012; 13/538203, filed on June 29, 2012; 13/600333, filed on August 31, 2012; and 13/628548, filed on September 27, 2012, the entire contents of which are incorporated herein by reference. There can sometimes be a large mismatch in the coefficient of thermal expansion (CTE) between an alpha alumina ceramic part and the metal rings. This large CTE mismatch leads to large undesired tensile stresses in the ceramic, resulting in low joint strength. Achieving high bond strength between the ceramic parts, active braze alloys, and the metallic part is desirable. An intermediate structure, including a glass along with active braze alloy between the ceramic collar 60 and the metal ring 110, is hereby disclosed to be very effective in reducing the CTE mismatch and strengthening the overall bonding of the ceramic-metal joints.
[0022] FIG. 2 depicts an enlargement of an illustrative joining structure
between the ceramic and metal parts that would be found in the electrochemical cell of FIG. 1. Accordingly, in one embodiment, an electrochemical cell is disclosed that has a first component 200 and a second component 400, and an intermediate structure 300 disposed between the first component 200 and the second component 400, as shown in FIG. 2. In one embodiment, the first component 200 of the cell comprises a ceramic, and the second component 400 comprises a metal. The (first) ceramic component 200 can be a collar that includes an electrically insulating material, such as alpha-alumina. The (second) metal component 400 can be formed of a variety of metals and alloys. In a particular embodiment, the second component is made up of nickel metal, i.e., the component contains at least about 95 % of nickel metal.

[0023] The intermediate structure 300 includes an active braze alloy 310
and a glass composition 320. An "active braze alloy" is an alloy composition including an active metal element that promotes wetting of a ceramic surface, enhancing the capability of providing a hermetic seal with the first component 200.
[0024] However, active brazing of the current configuration of alumina
collar 60 to nickel ring 110 (FIG. 1) may still lead to large residual tensile stresses on alumina, due to the large thermal expansion mismatch between alumina and nickel. This may result in low joint strength. Different embodiments of this invention disclose a novel design of a joint, where an intermediate structure including an active braze alloy and glass is used to join alumina and nickel. Glass absorbs the stresses above its glass transition temperature, similar to a polymer material, and helps to prevent the occurrence of tensile stress in the alumina component. Such a joint has minimal residual stress that can cause cracks in alumina. Furthermore, such a joint can exhibit relatively high strength.
[0025] The first component 200 (FIG. 2) used herein is usually an alpha
alumina-containing ceramic component having oxygen as part of the composition of the component. The "active metal element" of the active braze alloy refers to a reactive metal that has high affinity to the oxygen within the ceramic, and thereby reacts with the first component 200. The active metal element undergoes a decomposition reaction with the ceramic, when the braze alloy is in a molten state, and leads to the formation of the reaction layer 330 at the interface of the first component 200 and the braze alloy 310 of the intermediate structure 300.
[0026] The active metal element is an essential constituent of a braze
alloy for employing active brazing. A variety of suitable active metal elements may be used to form the active braze alloy. The selection of a suitable active metal element mainly depends on the chemical reaction with the ceramic (e.g., alumina) of the first component 200 to form the reaction layer 330. The reaction layer 330 formed may be of uneven thickness and discontinuous in some

embodiments, but may be uniform and continuous in some other embodiments. In some preferred embodiments for the present invention, the active metal element is titanium. Other suitable examples of the active metal element include, but are not limited to, zirconium, hafnium, and vanadium. A combination of two or more active metal elements may also be used.
[0027] In one embodiment, the reaction layer 330 includes a metallic
element of the first component 200 and a sub-oxide of the active metal element. For example, in an embodiment where the first component is of alpha alumina, and the active metal element is titanium, the reaction layer 330 may have a composition comprising aluminum and a sub-oxide of the active metal element. A sub-oxide of titanium may be defined as a titanium oxide with the titanium-to-oxygen ratio less than 1:2. Thus a titanium sub-oxide is TiOx with x < 2. T12O, TiO, and TiOu can be the examples of a titanium sub-oxide.
[0028] The presence and the amount of the active metal in the active braze
alloy 310 may influence the thickness and the quality of the reactive layer 330, which contributes to the wettability or flowability of the braze alloy of the intermediate structure 300 with the first component 200, and therefore, the bond strength of the resulting joint. In some embodiments, the active metal is present in a concentration less than about 10 weight percent, based on the total weight of the active braze alloy. A suitable range is often from about 0.1 weight percent to about 5 weight percent. In some specific embodiments, the active metal is present in an amount ranging from about 1 weight percent to about 3 weight percent, based on the total weight of the active braze alloy of the intermediate structure 300. The active metal element is generally present in relatively small amounts suitable for improving wetting of the ceramic surface, and forming the reaction layer 330. A high amount of the active metal, e.g., above about 10 weight percent, may cause or accelerate halide corrosion.
[0029] The reaction layer 330 is often a very thin layer that allows the
active braze alloy of the intermediate structure 300 to wet the surface of the first

component 200. In one embodiment, the formed reaction layer 330 is continuous and has an average thickness less than about 10% of the intermediate structure 300. In one embodiment, the reaction layer thickness is less than about 5% of the intermediate structure 300. In some preferred embodiments, the reaction layer thickness is less than about 10 micrometers, and specifically less than about 5 micrometers.
[0030] In order to address some of the problems associated with
corrosion, the present inventors discovered that nickel could be used as a component of the active braze alloy 310. Nickel provides a degree of chemical inertness in a corrosive environment. Further, the use of nickel in the active braze alloy 310 may promote the integration of joints with the nickel-containing second component 400. Additionally, nickel can also increase the liquidus temperature of the alloy composition. As used herein, the term "liquidus temperature" generally refers to a temperature at which an alloy is transformed from a solid into a molten or viscous state when heated. However, a high amount of nickel may undesirably raise the liquidus temperature of the alloy composition, i.e., above the required brazing temperature.
[0031] In some embodiments of this invention, a suitable level for the
amount of nickel in the braze alloy composition may be at least about 30%, based on the total weight of the braze alloy 310. Very often, nickel is present in an amount of at least about 45%. In some embodiments that are preferred for selective end-use applications, the nickel is present from about 50% to about 70%, based on the total weight of the active braze alloy 310, and more often, from about 50% to about 65%.
[0032] The active braze alloy 310 composition may further comprise an
element selected from chromium, niobium, tantalum, cobalt, and combinations thereof. These elements are especially useful for providing strength, high-temperature resistance, and corrosion-resistance in a sodium-containing environment.

[0033] In one embodiment, the braze alloy 310 composition is based on a
nickel-germanium (Ni-Ge) binary alloy. Nickel is a base metal for the braze alloy, which is relatively inert in corrosive environments, as compared to other known base metals, e.g. copper, iron, chromium, etc. Germanium is a melting point depressant, the addition of which reduces the melting point of the overall composition. As used herein, the term "melting point depressant" refers to an element which may depress the melting point of the resulting alloy, when added to another element or an alloy. The melting point depressant element may decrease the viscosity and, in turn, increase the flowability (also referred to as wettability) of the braze alloy, at an elevated temperature.
[0034] In order to reduce the liquidus temperature of the active braze
alloy 310, additional melting point depressants may be added. Suitable examples of the additional melting point depressant include, but are not limited to, silicon, boron, manganese, or iron.
[0035] In some specific embodiments, the active braze alloy 310 is
substantially free of some commonly used melting-point depressant materials. For example, in one embodiment, the active braze alloys 310 are free of copper, silver, gold, and platinum. In another example, the active braze alloys are free of zinc, rhenium, and phosphorous. In a specific embodiment, the active braze alloy 310 is free of melting point depressant materials such as copper, silver, gold, zinc, platinum, rhenium, and phosphorous. In some particular embodiments, these elements may only be present as impurities, not being added purposefully to optimize a particular characteristic of the active braze alloy 310. The addition of some these elements may be helpful for decreasing the liquidus temperature of the active braze alloy 310, but can sometimes be problematic in the case of sodium metal halide electrochemical cells. For example, gold and silver tend to form various intermetallics with sodium, at the operating temperature of the cells, and this can promote corrosion when the cell is in operation. Thus, it is often preferred that the active braze alloy 310 composition be free of these metals.

[0036] Generally, the active braze alloy 310 has a liquidus temperature
lower than the melting temperatures of the first and second components. In one embodiment, the active braze alloy 310 has a liquidus temperature of at least about 850 degrees Celsius. In one embodiment, the active braze alloy 310 has a liquidus temperature from about 950 degrees Celsius to about 1300 degrees Celsius, and in some specific embodiments, from about 1000 degrees Celsius to about 1250 degrees Celsius.
[0037] In some specific embodiments, a sheet or foil of the active braze
alloy 310 may be desirable. The thickness of the sheet or foil may usually be less than about 75% of the thickness of intermediate structure 300.
[0038] The glass 320 portion of the intermediate structure 300 aids in
reducing the effect of thermal expansion mismatch between the first component 200 and the second component 400 by absorbing the thermal expansion and contraction stresses above the glass transition temperature. The glasses used herein in some of the embodiments are of good thermal and mechanical stability at room temperature and at the operating temperature of the electrochemical cell, and have a glass transition temperature in a range from about 500°C to about 700°C.
[0039] The glass transition temperature, mechanical stability, density, and
the corrosion resistance properties of the glass 320 composition are often selected in a manner best adapted for operation in sodium metal halide electrochemical cells. Accordingly, in one embodiment, the glass 320 of the intermediate structure 300 comprises oxides of aluminum, silicon, and boron as a part of its composition. High aluminum content in the glass 320 composition increases the high temperature stability and Tg (glass transition temperature) of the glass 320. Boron and silicon are typically added to decrease the Tg to the desired range of about 500°C to about 700°C, among other advantages. However, a higher boron and silicon content may be detrimental to the chemical stability of the glass 320 at the operating environment of the electrochemical cell. Further, boron and silicon

may be more reactive towards the active metal elements of the active braze alloys than aluminum, and can therefore form reaction products which reduce the actual glass 320 percentage of the intermediate structure 300.
[0040] In one embodiment, depending on the type of electrochemical cell,
the active braze alloys 310 used, and the active metal element of the active braze alloy 310, the content of aluminum, boron, and silicon are carefully designed. In one embodiment, the desired glass 320 composition includes alumina in a range from about 4.7 wt% to about 20 wt%, silicon in a range from about 8 wt% to about 69.5 wt%, and boron in a range from about 17 wt% to about 45 wt%.
[0041] Along with oxides of aluminum, silicon, and boron, the glass 320
may further include calcium, barium, strontium, sodium, zinc, zirconium, lithium, or a combination thereof. In one embodiment, the glass 320 composition includes more than about 48 % of B2O3, more than about 20 % each of AI2O3, and BaO, and less than about 5 % of Si02. Another glass 320 composition contains more than about 65 % of Si02, less than about 20 % each of A1203, Na20, and B203, and less than about 1 % each of ZnO and Li20. Another suitable glass composition includes more than about 65 % of Si02, about 15% to 20 % of B203, about 5% to 10 % of Na20, less than 5 % of A1203, and less than 2 % of ZnO.
[0042] In an example, a glass 320 composition of about 46% of Si02,
25% of B203, 10% of A1203, 4% of Na20, 3% of CaO, 6% of SrO, and 6% of BaO is used along with a suitable active braze alloy 310. In another example, about 41.8% of Si02,22.7% of B203,18.2% of A1203, 3.6% of Na20, 3% of CaO, 5.5% of SrO, and 5.5% of BaO is used as the glass 320 composition. Table 1 presents some of the other suitable glass 320 examples (in wt%) that can be effectively used with various active braze alloy 310 compositions described in this application, for the use as a part of intermediate structure 300.

Table 1.
[0043] The glass 320 may be in an amount between about 17 volume
percent and about 60 volume percent of the composition of the intermediate structure 300. A certain minimum amount of glass 320 may be desirable to have effective percolation in the intermediate structure 300. If the glass level is more than 60 vol%, the brittleness of the intermediate structure may increase to an undesirable level. Further, the suitable volume percent of the glass 320 in the intermediate structure may depend upon the composition of the glass 320, composition of the active braze alloy 310, thickness of the intermediate structure 300, grain sizes of the glass 320 used, and the physical arrangement of the active braze alloy 310 and the glass 320 in the intermediate structure 300, to name a few factors.
[0044] The physical arrangement of the active braze alloy 310 and the
glass 320 in the intermediate structure 300 may be varied to obtain effective bonding between the ceramic collar 60 and metal ring 110 (FIG.l). The glass composition 320 should be in contact with the first component 200 to decrease the tensile stress of the first component during cooling of the brazed joints between the ceramic collar 60 and the metal ring 110. In other words, some part of the glass 320 composition is in physical contact with the first component 200. Moreover, some portion of the active braze alloy 310 component should be in

contact with the second component 400. In a further embodiment, it is desirable that the glass composition be in contact with the second component 400, while the active braze alloy 310 is also in contact with the first component 200. One such exemplary microstructure is shown in FIG. 3, wherein an alumina component and a nickel component are joined using a combination of an active braze alloy 310 and a glass 320 composition. It can be seen that the glass phase 320 is largely in contact with the alumina component; and the active braze alloy component is largely in contact with the nickel component.
[0045] In one embodiment, the glass 320 composition is a continuous
phase in the intermediate structure 300, and in another embodiment, the active braze alloy 310 is a continuous phase. In a specific embodiment, both the active braze alloy 310 and the glass 320 compositions are continuous phases in the intermediate structure 300. Various non-limiting examples of the different physical arrangements of the active braze alloy 310 and the glass 320 compositions in the intermediate structure 300 are shown in FIG. 4. The active braze alloy 310 and glass compositions 320 may be in a slanted layer arrangement 340, or a vertical layer arrangement 350, a matted arrangement 360, a gravel arrangement 370, or in a mixture arrangement 380. In one exemplary embodiment, the intermediate structure 300 is a homogenous mixture of glass 320 and the active braze alloy 310, with the glass 320 phase as a continuous phase.
[0046] With reference to FIG. 2, the intermediate structure 300 of various
embodiments of this specification has a density greater than about 92%, and is hermetic to helium gas. A small amount of porosity in the intermediate structure 300 may enhance the flowability of glass 320, and better accommodate the CTE mismatch-stress of alumina collar 60. In one embodiment, a stable joint that can remain intact against a tensile force greater than about 0.1 MPa is prepared between an alpha alumina component and a nickel metal, using a glass and an active braze alloy mixture.

[0047] Some embodiments of this invention provide a method for joining
the first component 200 to the second component 400 by using the intermediate structure 300 (FIG. 2). The method includes the steps of mixing and introducing the powders of active braze alloy 310 and the glass 320 compositions, or inserting layers of the active braze alloy 310 and the glass 320, in the appropriate locations. The layers of active braze alloy 310 and the glass 320 may be obtained by combining (e.g., mixing and/or milling) commercial powders of the constituents in their respective amounts. In some embodiments, the physical form of each layer may be a foil, a sheet, a ribbon, a preform, or a wire, or may be formulated into a paste containing water and/or organic fluids. In some embodiments, the precursor metals or metal alloys may be melted to form homogeneous melts, before being formed and shaped into layers. In some cases, the molten material can be directly shaped into foils, preforms or wires.
[0048] In a typical embodiment, the method further includes the step of
heating the structure to form an intermediate structure 300 between the first component 200 and the second component 400, thus forming a joint between the first and second components.
[0049] Some of the other inventive embodiments of this invention are
directed to an energy storage device (battery) that includes a plurality of the electrochemical cells as disclosed in previous embodiments. The cells are, directly or indirectly, in thermal and/or electrical communication with each other. Those of ordinary skill in the art are familiar with the general principles of such devices. For example, U.S. Patent 8,110,301 is illustrative, and incorporated by reference herein. However, there are many other references which generally describe various types of energy storage devices, and their construction.
[0050] The present invention has been described in terms of some specific
embodiments. They are intended for illustration only, and should not be construed as being limiting in any way. Thus, it should be understood that modifications can be made thereto, which are within the scope of the invention

and the appended claims. Furthermore, all of the patents, patent applications, articles, and texts which are mentioned above are incorporated herein by reference.

CLAIMS:
1. An electrochemical cell, comprising:
a first component comprising alpha alumina;
a second component comprising nickel; and
an intermediate structure disposed between the first component and the second component, comprising a glass and an active braze alloy, wherein
the glass is present in an amount between about 17 volume percent and about 60 volume percent of the composition of the intermediate structure; and
the active braze alloy comprises an active metal element in an amount less than about 10 weight percent.
2. The electrochemical cell of claim 1, wherein a glass transition temperature of the glass is in a range from about 500°C to about 700°C.
3. The electrochemical cell of claim 1, wherein the glass comprises oxides of aluminum, silicon, and boron.
4. The electrochemical cell of claim 3, wherein the glass further comprises calcium, barium, strontium, sodium, or a combination thereof.
5. The electrochemical cell of claim 1, wherein the intermediate structure further comprises reaction products of the glass and the active braze alloy.

6. The electrochemical cell of claim 5, wherein an interface of the glass and active braze alloy comprises partial oxides of the active metal element.
7. The electrochemical cell of claim 1, wherein the intermediate structure is a mixture of glass and the active braze alloy.
8. The electrochemical cell of claim 1, wherein a liquidus temperature of the active braze alloy is in a range from about 1000°C to about1350°C.
9. The electrochemical cell of claim 1, wherein the active braze alloy further comprises nickel.
10. The electrochemical cell of claim 1, wherein the active metal element comprises titanium, zirconium, hafnium, vanadium, or a combination thereof.
11. The electrochemical cell of claim 1, wherein the activel braze alloy further comprises germanium.
12. The electrochemical cell of claim 1, wherein the active braze alloy further comprises chromium and iron.
13. The electrochemical cell of claim 1, wherein the active braze alloy further comprises chromium, niobium, and cobalt.
14. The electrochemical cell of claim 1, wherein the active braze alloy is substantially free of copper, silver, gold, and platinum.
15. The electrochemical cell of claim 1, wherein the active braze alloy is substantially free of zinc, rhenium, and phosphorous.
16. The electrochemical cell of claim 1, further comprising a reaction layer disposed between the first component and the intermediate structure.

17. The electrochemical cell of claim 16, wherein the reaction layer comprises a sub-oxide of the active metal element and aluminum.
18. The electrochemical cell of claim 16, wherein a thickness of the reaction layer is less than about 10% of the thickness of the intermediate structure.
19. A battery that comprises a plurality of interconncted electrochemical cells, wherein each cell comprises:
a ceramic collar comprising alpha alumina;
a metal ring comprising nickel; and
a sealing structure disposed between the ceramic collar and the metal ring, comprising a glass and an active braze alloy, wherein
the glass is in an amount between about 17 volume percent to about 60 volume percent of the composition of the sealing structure; and
the active braze alloy comprises an active metal element in an amount less than about 10 weight percent.