Thermal batteries with thermally controlled heating capability for long life and thermal stability

Abstract

A thermal battery includes an enclosure that houses a plurality of battery cells, with each cell having an anode element, a cathode element, and a thermally activated electrolyte positioned between them. The thermally activated electrolyte is configured to activate at a specific threshold temperature. The battery features a heater designed to heat the thermally activated electrolyte to a prescribed temperature. This heater is made from aluminum nitride (AlN) material and is in thermal contact with the thermally activated electrolyte. Additionally, the battery incorporates thermally insulating layers, each consisting of a first outer layer with low thermal conductivity and a second inner layer made of AlN material.

Description

THERMAL BATTERIES WITH THERMALLY CONTROLLED HEATING CAPABILITY FOR LONG LIFE AND THERMAL STABILITYTECHNICAL FIELD

[0001] This disclosure relates to thermal batteries with thermally controlled heating capability for long life and thermal stability.BACKGROUND

[0002] Thermal batteries are uniquely designed around thermally activated electrolytes due to their distinct properties. At room temperature, these electrolytes exhibit high impedance when solid, but become conductive upon heating, thus enabling the operation of the thermal battery. The activation point of these electrolytes is typically greater than 300°C and, depending on class, sometimes as low as 100°C.

[0003] The thermal management of these batteries is complex and influenced by several factors. Internal heating is typically achieved through exothermic chemical reactions, known as “chemical heat,” which are initiated by activation of a squib (miniature explosive device) within the battery containment housing. Internal heating is engineered to raise the battery's temperature by a specific amount. This temperature increase must accommodate by design, the minimum and maximum range of operational temperatures required for the battery before activation.

[0004] Additionally, the electrodes (both cathodes and anodes) have limitations regarding the maximum temperature they can endure. This necessitates the incorporation of significant built-in heat generation along with extensive insulation systems. These combined requirements, including broad application needs and thermal functionality, ultimately reduce the total energy available from a given battery size.SUMMARY

[0005] Consistent with various other embodiments, the appended claims may serve as a further summary of the disclosure.

[0006] The embodiments disclosed herein are only examples, and the scope of this disclosure is not limited to them. Some embodiments may include all, some, or none of the components, elements, features, functions, operations, or steps of the embodiments disclosed herein. The dependencies or references back in the attached claims are chosen for formal reasons only. However, any subject matter resulting from a deliberate reference back to any previous claims (in particular multiple dependencies) can be claimed as well, so that anycombination of claims and the features thereof are disclosed and can be claimed regardless of the dependencies chosen in the attached claims. The subject-matter which can be claimed comprises not only the combinations of features as set out in the attached claims but also any other combination of features in the claims, wherein each feature mentioned in the claims can be combined with any other feature or combination of other features in the claims. Furthermore, any of the embodiments and features described or depicted herein can be claimed in a separate claim and / or in any combination with any embodiment or feature described or depicted herein or with any of the features of the attached claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1A depicts an illustrative embodiment of a thermal battery with Aluminum Nitride (AIN) elements, according to certain embodiments.

[0008] FIG. IB shows another illustrative embodiment of a thermal battery with a heater located in a central portion of the battery, according to certain embodiments.

[0009] FIGS. 1C-1E show illustrative embodiment of a heating element and battery cells, according to certain embodiments.

[0010] FIG. 2 shows illustrative plots of thermal battery heat imbalance at different ambient temperatures, according to certain embodiments.

[0011] FIGS. 3A and 3B illustrate the differences in the design of thermal batteries when AIN elements are present, according to certain embodiments.

[0012] FIG. 4 shows illustrative plots of a thermal battery with a heater at different ambient temperatures, according to certain embodiments.

[0013] FIG. 5 is an example diagram illustrating a method of regulating the operations of a thermal battery, according to certain embodiments.

[0014] FIG. 6 is a schematic of a controller, according to certain embodiments.DETAILED DESCRIPTION

[0015] In the following description, for the purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the present disclosure. It will be apparent, however, that embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known structures and devices are shown in schematic form to avoid unnecessarily obscuring the description of the present disclosure.

[0016] The text in conjunction with the accompanying drawings aims to articulate the designs and methods at a level of detail consistent with the communication standards among skilled individuals in the relevant arts. This level of detail mirrors the customarycommunication among those with expertise in the field, effectively expressing the structure and function of the various designs outlined in this disclosure.

[0017] Various embodiments may be described in this disclosure to illustrate various aspects. Other embodiments may be utilized, and structural, logical, and other changes may be made without departing from the scope of the embodiments that are specifically described. Various modifications and alterations are possible and expected. Some features may be described with reference to one or more embodiments or drawing figures, but such features are not limited to usage in the one or more embodiments or figures with reference to which they are described. Thus, the present disclosure is neither a literal description of all embodiments nor a listing of features that must be present in all embodiments.

[0018] Headings of sections and the title are provided for convenience but are not intended as limiting the disclosure in any way or as a basis for interpreting the claims.

[0019] A description of an embodiment with several components present does not necessarily imply that all such components are required. Optional components may be described to illustrate a variety of possible embodiments and to illustrate one or more aspects of the present disclosure more fully. When a single device or article is described, more than one device or article may be used in place of a single device or article. Where more than one device or article is described, a single device or article may be used in place of more than one device or article.

[0020] The functionality or features of a device may be alternatively embodied by one or more other devices that are not explicitly described as having such functionality or features. Thus, other embodiments need not include the device itself.Definitions

[0021] In various embodiments of the disclosure, terms such as “approximate,” “about,” “similar,” “equal,” “equivalent”, “substantially”, or “the same as” are used to indicate a degree of flexibility or tolerance in numerical values, measurements, and characteristics disclosed. The scope of the disclosure should not be limited to strict numerical precision, and these terms are employed to allow for variations within acceptable limits.

[0022] The terms “approximate,” “about,” and “similar” are used interchangeably to convey that a given value, parameter, or characteristic may deviate within a reasonable range from the stated value. This range may encompass slight variations that do not materially affect the functionality or performance of the systems and methods described in this disclosure. Forexample, the terms “approximate,” “about,” and “similar” may refer to a variation of ten percent from a specific value.

[0023] The terms “equal,” “equivalent,” or “the same as” are used to indicate that values, parameters, or characteristics described as such are substantially identical or sufficiently close in magnitude, without necessarily requiring absolute precision. For example, such terms may be referred to a deviation of a few percent from a specific value such as one or two percent.

[0024] Further, the term “similar” may be employed to denote a likeness or resemblance between two or more elements, aspects, or features, allowing for variations that do not compromise the fundamental nature or purpose of the disclosure.

[0025] In various embodiments of the disclosure, the term “set” is employed to denote a grouping or collection of objects, elements, components, or entities. The flexibility in the interpretation of the term “set” allows for adaptability and practical application in situations where a singular object satisfies the intended functionality or purpose of the disclosure. Thus, the disclosure is not limited to instances where a “set” must consist of multiple objects but rather contemplates scenarios where a “set” may include one object.Thermal Batteries with Thermally Controlled Heatins

[0026] Various embodiments discussed herein relate to thermal batteries with improved heat management and control. Additionally, the described thermal batteries feature enhanced electrical and mechanical properties.

[0027] Unlike traditional batteries that rely on ongoing chemical reactions, thermal batteries use heat to trigger what is typically a one-time set of electrochemical reactions. These batteries are especially valuable in specific high-power, short-duration applications where reliability and long shelf life are critical.

[0028] In various embodiments, thermal batteries include multiple stacked individual cells, or battery cells, each contributing to the overall voltage and capacity. Unlike conventional batteries, the internal structure of thermal batteries is more intricate, and designed to handle the high temperatures required for operation.

[0029] The battery includes an anode that can be made from highly reactive metals such as lithium, magnesium, or calcium. These metals act as the negative electrode and play an important role in the electrochemical reactions once the battery is activated.

[0030] Furthermore, the battery includes a cathode, serving as the positive electrode. The cathode is generally composed of metal salts, which can include group 1 (alkali metals) suchas lithium sulfide (Li2S), and group 2 (alkaline earth metals) such as magnesium sulfide (MgS), calcium sulfide (CaS), and strontium sulfide (SrS). Additionally, the cathode can be formed from transition metals such as iron disulfide (FeS?), known for its good electrochemical performance, cobalt disulfide (C0S2) with similar properties to FeS2, nickel sulfide (NiS), and copper sulfide (CuS), which is less common due to its lower cell voltage. Furthermore, the cathode can be formed from lanthanides, including cerium sulfide (CeS2). In some cases, other materials such as titanium disulfide (TiS2) can also be included. These materials are chosen for their ability to undergo a reduction reaction, accepting electrons during the battery's operation.

[0031] One class of thermally activated electrolytes is metal salts. The selection of a specific metal salt for a thermal battery cathode depends on several factors such as electrochemical performance, as the material should have a high operating voltage and be able to deliver the desired current output; thermal stability, as the cathode material needs to remain stable at high temperatures during battery operation; ionic conductivity, conducting the appropriate number of charged particles through the electrode at sufficient mobility to enable the required rate of discharge; electronic conductivity, conducting a sufficient number of electrons required to enable the required rate of electrode reduction; safety, as the material should not decompose or react violently during activation or storage; and cost and availability, as some materials may be more expensive or difficult to obtain than others.

[0032] The electrolyte in a thermal battery is a traditionally a molten salt mixture, which only becomes effectively conductive at high temperatures, usually between about 300°C and 450°C, and in some cases up to 550°C. The melting point (MP) range of electrolytes used in thermal batteries can vary depending on the specific composition of the molten salt mixture. Generally, the MP range for these electrolytes is between 350°C and 550°C. This range ensures that the electrolyte remains solid at room temperature for stability and safety but becomes conductive at the elevated temperatures required for ionic conductivity and the operation of the thermal battery. In other aspects the electrolyte becomes effectively conductive at lower temperatures to very low temperatures: less than 100°C, less than 0°C, temperatures between about 0°C and -55°C. These may employ very low melting salts or salt complexes where activation heats are very low, and may include low-melting salts and also what are commonly called ‘ionic liquids.’

[0033] The molten salt electrolyte is often a eutectic mixture of inorganic salts combined with an inorganic binder to ensure stability and effective ion conduction when melted. Examples of such molten salts include lithium chloride-potassium chloride (LiCl-KCl), sodiumchi ori de-magnesium chloride (NaCl-MgCb), lithium fluoride-lithium chloride-potassium chloride (LiF-LiCl-KCl), lithium fluoride- sodium fluoride-potassium fluoride (LiF-NaF-KF), and lithium fluoride-lithium bromide-potassium bromide (LiF-LiBr-KBr).

[0034] Separating the anode and cathode is a ceramic or powdered metal oxide separator. This component is important for maintaining the physical separation of the electrodes while allowing ion flow through its pores once the electrolyte is melted. The separator ensures that the electrochemical reactions can proceed efficiently without short-circuiting the battery. Examples of separator materials include aluminum oxide (AI2O3), magnesium oxide (MgO), and zirconium oxide (ZrCE). These materials can be structured in thin layers, with thicknesses ranging from 0.1 mm to 1 mm, depending on the specific requirements of the battery design. The porosity and pore size distribution of the separator are also tailored to optimize ion flow while preventing physical contact between the electrodes, ensuring both efficiency and safety in battery operation.

[0035] A distinctive feature of some thermal batteries is their pyrotechnic initiator or squib. This small device contains a heat-producing material, such as thermite or potassium perchlorate (KCIO4), which, when ignited, rapidly generates the heat necessary to melt the electrolyte and activate the battery. Other examples of heat-producing materials used in pyrotechnic initiators include barium chromate (BaCrO4), zirconium potassium perchlorate (Zr / KClO4), and iron (III) oxide-aluminum (Fe2O3 / Al) mixtures.

[0036] In addition to pyrotechnic initiators, non-pyrotechnic approaches can also be used to heat the electrolyte in thermal batteries. One method is the use of electrical heaters. These heaters can be resistive elements, such as nichrome or tungsten wires, which convert electrical energy into heat when a current is passed through them. The heaters are strategically placed within the battery to ensure uniform heating and rapid melting of the electrolyte.

[0037] One type of resistive heater is the tube heater. Tube heaters are resistive heating elements encased in a metal tube, often made of stainless steel or Inconel, which provides durability and efficient heat transfer. These heaters work by converting electrical energy into heat when a current is passed through the resistive element. Tube heaters can include resistive heating elements surrounded by any suitable heat conductive material. In an example embodiment, the tube heater includes a resistive heating element encased in an Aluminum Nitride (AIN) material. The AIN material provides electrical insulation for the resistive heating element while maintaining a high thermal conductivity. In one example embodiment, the resistive heating element for such a tube heater may be formed from a suitable electricallyconductive resistive material such as tungsten. The manufacturing process of poly-Aluminum Nitride (not single crystal) is to produce the AIN particles in a slurry which gets manufactured into sheets of “green” ceramic materials. Those sheets can be formed into shapes and also have tungsten in between layers for the heating elements. Once together they get cured into the final form. So, they can achieve many different shapes, including small particles, cylinders, a substantially continuous ceramic layer, for example.

[0038] A heater such as a tube heater can be installed within the battery assembly in close proximity to the electrolyte. When the battery needs to be activated, an electrical current is supplied to the tube heater, which then heats up rapidly and transfers heat to the surrounding electrolyte. This process causes the electrolyte to melt, allowing ions to flow and the battery to become operational.

[0039] Tube heaters offer several advantages. The temperature can be precisely controlled by adjusting the electrical input, ensuring uniform and efficient heating of the electrolyte. Additionally, tube heaters do not involve combustion or explosive reactions, reducing the risk of accidental ignition and improving the overall safety of the battery. The robust construction of tube heaters ensures they can withstand the thermal and mechanical stresses within the battery environment.

[0040] Other types of heaters include induction heaters, which use electromagnetic fields to induce currents within the battery components, generating heat. This method is particularly effective for providing quick and controlled heating without direct contact with the electrolyte.

[0041] Additionally, chemical heaters, which rely on exothermic chemical reactions, can be employed. For example, the reaction between calcium oxide (CaO) and water (JLO) generates significant heat and can be used to activate the battery.

[0042] In some cases, various heating devices may be part of heating elements that are configured to melt the electrolyte. Various types of heating elements can be employed, each with associated properties and advantages. Proper geometric positioning of these elements ensures effective heat transfer to both the heating element, such as a tube heater, and the electrolyte.

[0043] When using resistive heaters, nichrome or tungsten wires can be commonly used due to their high resistance and ability to withstand high temperatures. These wires can be coiled to fit within the battery structure and provide uniform heating. Another type of resistive heater includes metal foil heaters. Thin metal foils made of materials like nickel or stainlesssteel can be used to create flat heating elements, which are beneficial for applications requiring even surface heating.

[0044] Additionally, heating elements may include simple thermal conductors that penetrate the electrolyte. These conductors transfer heat directly from an external source into the electrolyte, ensuring it reaches the required temperature for activation.

[0045] In some cases, more than one heater can be used. For example, when the battery requires initial activation, a reactive chemical heater can be used to rapidly heat the thermal battery. Once the battery is heated and activated, an electrical heater, such as a tube heater, can be used to maintain the required temperature of the battery. In some instances, the power for the resistive heating element of the tube heater can be supplied from the electrical power generated by the thermal battery itself. This power can be regulated by a suitable controller that manages various aspects of the thermal battery's operation. For example, the controller may be configured to regulate the power delivered to different heating elements and to manage the distribution of temperature throughout the thermal battery, as further described below.

[0046] The geometric positioning of heating elements may be important to ensure efficient and uniform heating. Placing tube heaters centrally within the battery assembly allows them to radiate heat evenly outward. This central positioning ensures that the heat reaches the electrolyte uniformly. Induction coils can be wrapped around the central core of the battery, creating a uniform magnetic field that induces heat throughout the electrolyte. Nichrome wires can be coiled and distributed evenly within the battery, allowing for consistent heating throughout the electrolyte and minimizing cold spots. Foil heaters can be placed on the inner surfaces of the battery casing, providing a broad area of uniform heat distribution.

[0047] By layering resistive heating elements between layers of electrolyte material, heat can be transferred efficiently to each layer, ensuring that the entire volume of electrolyte is melted and activated. Chemical heater packs can be distributed between layers of battery components to provide localized heating where needed.

[0048] Further, placing heating elements around the periphery of the battery ensures that the edges receive sufficient heat, preventing any cold spots and ensuring complete melting of the electrolyte. Heating elements can also be encased around the battery's exterior to provide an even distribution of heat inward toward the electrolyte.

[0049] To ensure efficient heat transfer, materials used for the battery casing and separators should have good thermal conductivity to facilitate heat transfer from the heating elements to the electrolyte. Incorporating heat shields and reflectors can direct and focus the heat generatedby the heating elements, ensuring that the heat flows to the intended areas. Proper insulation around the heating elements can prevent heat loss and ensure that the maximum amount of heat is directed towards thermally activating the electrolyte. In various embodiments, the assembly of internal battery elements, such as battery cells, and heaters, is encased in a well-insulated shell. This insulation is important for minimizing heat loss and maintaining the high temperatures required for the battery's operation for as long as possible, ensuring efficient power delivery.

[0050] In its inactive state, a thermal battery is essentially inert. The electrolyte remains solid at room temperature, preventing any chemical reactions from occurring. This property makes thermal batteries ideal for long-term storage, often exceeding 20 years, without any degradation in performance. Activation occurs when an external electrical signal or mechanical impulse triggers the pyrotechnic heat source. The heat generated rapidly melts the solid electrolyte, making it conductive and initiating the battery's operation. With an electronic load on the battery and the electrolyte now in a molten state and capable of conducting ions, the anode begins to oxidize, losing electrons, while the cathode undergoes reduction by accepting electrons. This reaction creates a current flow through the external circuit connected to the battery's terminals, providing power to the device.

[0051] In various cases, thermal batteries are designed to deliver a high pulse of power for a short duration, which can range from a few seconds to several hours depending on the specific design and application. This makes them suitable for applications requiring intense bursts of energy.

[0052] In various embodiments, a thermal battery continues to function until one of the critical materials, either the anode or cathode, is depleted, or until the internal temperature drops below the threshold needed to keep the electrolyte molten. Once the electrolyte solidifies again, the reaction halts, marking the end of the battery's life.

[0053] In some cases, after the thermal battery freezes it can be unfrozen, with the process and feasibility depending on the specific design and materials used in the battery. Reheating is the primary method for unfreezing a thermal battery, involving the application of heat to raise the temperature of the battery above the melting point of the electrolyte. The heating can be achieved using the same methods initially employed to activate the battery, such as pyrotechnic initiators, electrical heaters, induction heaters, or chemical heaters. Pyrotechnic initiators can be reignited to generate the necessary heat, while electrical heaters can apply an electrical current to resistive elements like nichrome wires or tube heaters. Induction heaters utilizeelectromagnetic fields to induce currents within the battery components, generating heat. Chemical heaters initiate an exothermic reaction to produce heat. Use of thermocouples or other temperature information enable the use of exothermic electrode reactions (as in some liquid metal batteries) to be accommodated as additional heat supply during the discharge of the battery. Additionally, if the battery design includes thermal conductors that penetrate the electrolyte, these can transfer heat directly into the frozen electrolyte, ensuring efficient melting.

[0054] Several considerations and challenges are associated with this process. Material integrity is important, as repeated freezing and thawing cycles can affect the integrity of the battery materials. Ensuring that the materials can withstand these cycles without degradation is important. The electrolyte should be stable and maintain its properties after freezing and thawing, as some electrolytes might crystallize or change their structure, affecting performance. Uniform heating is important to avoid localized melting, which can lead to incomplete activation or hot spots that might damage the battery.

[0055] For instance, when unfreezing the battery, heat can be gradually applied to raise the temperature of the battery, such as by supplying an electrical current to a tube heater until the electrolyte reaches its melting point, typically between 350°C and 550°C. Uniform heating is ensured so that the electrolyte melts completely, with thermal sensors potentially used to monitor the temperature. Once unfrozen, the battery can be tested to ensure it is functioning correctly and has not been damaged during the freezing or unfreezing process.

[0056] Thermal batteries are traditionally, non-rechargeable due to the one-time use of their internal materials. Once activated and depleted, they cannot be reused. These batteries are ideal for scenarios requiring high power for brief periods, such as missile guidance systems, detonation triggers, and emergency beacons. Their design allows them to deliver the necessary power in critical moments.

[0057] The robust design of thermal batteries enables them to function effectively in extreme environments, including high temperatures and severe mechanical stresses. This reliability makes them invaluable for military and aerospace applications where conventional batteries might fail.

[0058] FIG. 1A illustrates an example of a thermal battery 100, which is housed within a cylindrical enclosure 116. The thermal battery 100 includes multiple battery cells 112 arranged inside an enclosure 116. A detailed view of illustrative battery cells 112A and 112B is provided in the zoomed-in section. These cells can be separated by an electrically insulating layer 115to ensure proper isolation and functioning. Each battery cell, such as battery cell 112A, consists of an anode element, a cathode element, and a thermally activated electrode such as a molten salt electrolyte positioned at least between the anode and cathode elements. The thermally activated electrolyte is designed to melt at a specific threshold temperature, enabling the electrochemical reactions necessary for the battery's operation.

[0059] Various materials can be used as anodes for thermal batteries, chosen based on their electrochemical properties, compatibility with the electrolyte, and overall battery performance requirements. Common anode materials for thermal batteries include lithium, calcium, magnesium, zinc, sodium, aluminum, and silicon. Lithium is highly reactive with a low atomic weight, making it useful for high-energy-density applications. Calcium offers a good balance of energy density and stability, suitable for applications requiring longer shelf life and high- temperature stability. Magnesium combines good electrochemical properties with costeffectiveness, while zinc is abundant, low-cost, and reliable. Sodium is an alternative to lithium, particularly where the cost is significant, though it has a lower energy density. Aluminum provides high energy density and stability in high-temperature environments and also functions effectively above its melting point as a liquid anode, and silicon, often used in combination with other materials, offers high energy density and good stability.

[0060] When selecting an anode material for a thermal battery or a liquid metal battery, several factors must be considered, including electrochemical potential, compatibility with the electrolyte, thermal stability, cost, availability, and safety. For instance, in an illustrative thermal battery design, a lithium anode might be used for its high energy density and electrochemical potential, paired with a compatible electrolyte such as a lithium chloridepotassium chloride (LiCl-KCl) molten salt mixture. During battery activation, the lithium anode undergoes oxidation, releasing electrons that flow through the external circuit to power the connected device, with resulting lithium ions migrating through the electrolyte to the cathode to complete the electrochemical reaction. By selecting the appropriate anode material based on these factors, thermal batteries can be designed to meet specific performance, safety, and cost requirements for various applications.

[0061] Various materials can be used as cathodes for thermal batteries, selected based on their electrochemical properties, compatibility with the electrolyte, and overall performance requirements. Common cathode materials for thermal batteries include metal sulfides and oxides, which provide good electrochemical performance and stability. Iron disulfide (FeS?) is often used due to its good electrochemical properties and high energy density. Cobalt disulfide(C0S2) offers similar properties to iron disulfide and is another popular choice. Nickel sulfide (NiS) is used for its stability and moderate energy density, while copper sulfide (CuS), although less common due to lower cell voltage, is also employed in specific applications. Lanthanides like cerium sulfide (CeS?) and other materials such as sulfur or titanium disulfide (Ti S2) can be included for their specific electrochemical advantages.

[0062] When selecting a cathode material for a thermal battery, several factors must be considered, including electrochemical performance, thermal stability, safety, cost, and availability. The material should have a high operating voltage and be able to deliver the desired current output, remain stable at high temperatures, and not decompose or react violently during activation or storage. Additionally, the cost and availability of the material can impact its feasibility for large-scale production.

[0063] For example, in an illustrative thermal battery design, iron disulfide (FeS2) might be used as the cathode material for its excellent electrochemical performance. This cathode would be paired with a compatible electrolyte, such as a lithium chloride-potassium chloride (LiCl-KCl) molten salt mixture. During battery activation, the FeS2 cathode undergoes a reduction reaction, accepting electrons that flow from the anode through the external circuit. The resulting ions migrate through the electrolyte to the anode, completing the electrochemical reaction.

[0064] Further, thermal battery 100 may include a suitable heater configured to heat the thermally activated electrolyte to a prescribed temperature. In some cases, the heater can include a heat producing resistive component. Further, the heater can be formed from an aluminum nitride (AIN) material. In various cases, the heater can be in thermal contact with the thermally activated electrolyte.

[0065] In various embodiments, the heater can be any suitable heating element such as a tube heater 114 configured to heat the molten salt electrolyte to a prescribed temperature. The prescribed temperature may be any suitable temperature that can range, for example, between 300 °C and 500°C.

[0066] Further, besides tube heater 114 additional heating elements internal to the thermal battery 100 may be used. These heater elements may be configured to be in thermal contact with the tube heater 114 and in thermal contact with the molten salt electrolyte, thereby conducting heat from the tube heater 114 to the molten salt electrolyte. While not shown in FIG. 1A, in addition to tube heater 114, which may be configured to provide heating during the operation of thermal battery 100, another heater, such as a pyrotechnic heater can be usedto initiate the battery by heating the battery to a prescribed temperature. Furthermore, once thermal battery 100 is heated to the prescribed temperature, tube heater 114 may be used to continue maintaining the temperature of the battery.

[0067] In some cases, tube heater 114 (or any other heater of thermal battery 100, if such heaters are presented) can be actively or passively controlled by a suitable battery controller configured to adjust the temperature of thermal battery 100 based on its operational requirements. For example, if the battery controller determines that the temperature of the thermal battery needs to be increased, it can adjust the power supplied to tube heater 114. This adjustment ensures that tube heater 114 maintains the appropriate temperature for optimal operation of thermal battery 100.

[0068] In various instances, the controller may be configured to receive temperature information from multiple sensors located within thermal battery 100. Based on these temperature readings, the battery controller can adjust the power supplied to tube heater 114. This dynamic adjustment ensures that the molten salt electrolyte maintains a suitable temperature, supporting the efficient operation of the thermal battery.

[0069] Additional considerations for the battery controller include the ability to manage multiple tube heaters within the thermal battery. Each tube heater can be individually adjusted to maintain adequate temperature distribution throughout the battery. This capability helps ensure uniform heating and avoids hot spots or cold areas, which can affect the battery's performance and longevity. The controller can receive temperature data from sensors distributed across different regions of the battery and adjust each tube heater's power output accordingly. This precise control allows the thermal battery to operate efficiently and reliably under varying conditions.

[0070] The battery controller should also be designed with safety mechanisms to prevent overheating and ensure the stability of the battery. It can include features such as automatic shutdown in case of abnormal temperature fluctuations and integration with the overall battery management system to coordinate with other components. These considerations are important for maintaining the safety, efficiency, and longevity of thermal battery 100.

[0071] In various embodiments, various internal heating elements may be formed from a material that includes aluminum nitride (AIN) material. For example, tube heater 114 may have a coating made from a composite material that includes AIN material. Additionally, or alternatively, other heating elements that are in thermal contact with both tube heater 114 andthe molten salt electrolyte may be formed from a composite material that includes AIN material.

[0072] When selecting materials for heating elements in thermal batteries, it is important to choose those that are both chemically inert and capable of withstanding high temperatures. Several materials can be used for heating elements in thermal batteries due to their relative chemical inertness and high-temperature capabilities. Such materials include a nichrome, a nickel-chromium alloy that can be composed of 80% nickel and 20% chromium, is widely used due to its high melting point of around 1400°C, good oxidation resistance, and stable performance at high temperatures. Its chemical inertness in many environments makes it suitable for high-temperature applications, and it is known for its durability and resistance to oxidation.

[0073] Further, molybdenum disilicide (MoSi2) is another popular choice, boasting a high melting point of around 2030°C, excellent oxidation resistance at high temperatures, and good electrical conductivity. It forms a protective silica layer on its surface, providing excellent resistance to oxidation and chemical attack. This makes MoSi2 ideal for use in high- temperature furnaces and extreme environments.

[0074] Additionally, tungsten, with its very high melting point of around 3422°C, excellent thermal conductivity, and good resistance to thermal shock, is also commonly used. While tungsten is chemically inert at high temperatures, it can oxidize at lower temperatures. To prevent oxidation, it is often used in inert gas atmospheres or vacuum conditions. Tungsten is particularly suited for high-temperature applications, such as heating elements for high- temperature furnaces and specialized thermal batteries.

[0075] Further, silicon carbide (SiC) is known for its high melting point of around 2730°C, excellent thermal conductivity, and good electrical conductivity at high temperatures. It is chemically inert in most environments and forms a protective silicon dioxide layer at high temperatures, making it suitable for use in high-temperature furnaces and thermal processing.

[0076] In some cases, Kanthal, an iron-chromium-aluminum alloy, typically contains iron, chromium, and aluminum. It has a high melting point of around 1500°C, excellent oxidation resistance, and stable performance at high temperatures. Kanthal forms a protective aluminum oxide layer, enhancing its resistance to oxidation and chemical attack.Table 1, melting points and properties of different thermally conductive materials.

[0077] Aluminum Nitride functions as a good thermal conductor. It can be used to embed electrical heating elements such as tungsten wire to enable the design and use of an electrically insulating, thermally efficient heating element. In some designs the Aluminum Nitride is fashioned into tubes, cups, or enclosures that provide additional mechanical housing to individual or multiple battery cells or, bipolar components within the battery. These heating elements are useful in thermal battery environments because they can withstand high heat exposure without deformation and are electrically insulative which prevents electrical conductivity that would cause electrical short circuiting between the battery cells of the assembled battery.

[0078] Incorporating Aluminum Nitride (AIN) into composite materials can enhance the thermal conductivity and insulation properties of the heating elements while maintaining their high-temperature performance and chemical inertness. Some of the materials that can be effectively combined with AIN to create composite heating elements include molybdenum disilicide (MoSi2), silicon carbide (SiC), and Kanthal (Iron-Chromium-Aluminum Alloy).

[0079] For example, MoSi2 combined with AIN creates heating elements that retain the high-temperature stability of MoSi2 while benefiting from the excellent thermal conductivity of AIN. This combination enhances thermal conductivity, improves thermal shock resistance, and provides better heat distribution.

[0080] Similarly, combining SiC with AIN forms a composite that leverages the strengths of both materials. These SiC-AlN composite heating elements exhibit high thermal conductivity, excellent electrical insulation, and improved thermal stability, making them suitable for heating elements.

[0081] Incorporating AIN into Kanthal enhances the overall thermal management properties of the heating element. These Kanthal-AIN composite heating elements offer improved heat dissipation, increased resistance to thermal cycling, and enhanced durability.

[0082] The incorporation of AIN into composite materials like MoSi2, SiC, and Kanthal varies depending on the desired properties and applications of the composites. For MoSi2, AIN can be incorporated in the range of 10% to 30% by volume. This range allows for improved thermal conductivity and thermal management while maintaining the high-temperature stability and structural integrity of MoSi2.

[0083] For SiC, AIN can be incorporated up to about 20% to 40% by volume. This range leverages the high thermal conductivity and electrical insulation properties of AIN, enhancing the thermal performance and stability of the SiC composite in high-temperature applications.

[0084] In the case of Kanthal, which is an iron-chromium-aluminum alloy, AIN is usually incorporated in percentage that can range between around 5% to 50% by volume. This range provides enhanced thermal management capabilities and thermal stability without significantly affecting the mechanical properties of the Kanthal alloy.

[0085] These volume percentages are general guidelines and can vary based on specific processing techniques, desired properties, and the particular application requirements of the composite materials. For example, the volume fraction of AIN that can be incorporated into a composite material with Kanthal depends on the desired properties of the final composite, including its thermal conductivity, mechanical strength, and electrical properties. Typically, the volume fraction can range from 5% to 50%.

[0086] For higher thermal conductivity, a higher volume fraction of AIN may be used up to 50%. This significantly enhances the composite’s ability to conduct heat. For a balance between thermal conductivity and other properties, such as mechanical strength, a moderate volume fraction, around 20-30%, is common.

[0087] The mechanical properties of the composite, such as tensile strength and toughness, can be affected by the volume fraction of AIN. A higher AIN content might reduce the ductility of the composite, so finding an optimal balance is important.

[0088] The ease of manufacturing the composite material can also influence the volume fraction. High AIN content might make the material more brittle and challenging to process. Since AIN is an electrical insulator, the volume fraction will also depend on the required electrical properties of the composite. If electrical insulation is an important consideration, a higher volume fraction of AIN would be beneficial.

[0089] For low volume fractions of 10-20%, the composite is suitable for applications where moderate improvement in thermal conductivity is needed without significantly compromising the mechanical properties of Kanthal. A moderate volume fraction of 20-30% provides a good balance between enhanced thermal conductivity and mechanical strength and can be used where both properties are important. High volume fractions of 30-50% maximize thermal conductivity but may reduce mechanical strength and processability.

[0090] Thermal battery 100 further includes thermal insulating layers 110A-110C, forming one or more insulating layers within the enclosure. Each layer is designed to insulate internal components, such as battery cells and heating elements, from the external environment, preventing heat from escaping thermal battery 100. Additionally, these insulating materials help manage the temperature within thermal battery 100 by distributing heat to various parts of the battery through a thermally conductive inner layer. For example, insulating layers 110A- 110C may include an outer layer with low thermal conductivity and an inner layer with higher thermal conductivity. In various embodiments, the higher thermal conductivity of the inner layer is achieved by incorporating aluminum nitride (AIN) material into the layer.

[0091] The outer low thermal conductivity layer may be formed from any suitable insulating material. Several materials can be used as insulating elements, each with distinct thermal insulating properties. For example, ceramic fibers, can made from alumina (A12O3), silica (SiO2), or a combination of both, and have low thermal conductivity, around 0.03-0.06 W / m K. They can withstand temperatures up to 1600°C. Ceramic fibers offer excellent thermal insulation, are lightweight, and can be formed into various shapes.

[0092] Further, aerogels can be used. The aerogels can be silica-based but can also be made from other materials such as alumina or carbon. They have extremely low thermal conductivity, around 0.015-0.02 W / m K, and can withstand temperatures up to 650°C for silica aerogels,with higher temperatures for other types. Aerogels are extremely lightweight and have excellent insulating properties, though they can be fragile and expensive.

[0093] In some cases, microporous insulating materials can be used. Such materials can be composed of fumed silica, opacifiers, and reinforcing fibers. They can have very low thermal conductivity, around 0.02-0.04 W / m K, and can withstand temperatures up to 1200°C. Such materials can provide high thermal insulation with a thin profile, making it excellent for space- constrained applications.

[0094] In some cases, calcium silicate, a blend of lime and silica can be used. It has low thermal conductivity, around 0.05-0.1 W / m K, and can withstand temperatures up to 1000°C. It offers good thermal insulation, is durable, and can be cut into various shapes. Alternatively, vermiculite, fiberglass, or polyimide foams can be used. In some cases, the first outer layer having low thermal conductivity may be formed from sublayers with different sublayers formed from different insulating materials.Table 2, heat conductivity temperature stability, and properties for different thermally insulating materials.

[0095] In various cases, such insulating materials can be selected based on the specific requirements of the thermal battery application, such as the operating temperature range, space constraints, and desired thermal performance. In some cases, the AIN formation process can be used to structurally incorporate small voids or pockets on the outer diameter side of tubelike heaters. This structural design then performs to selectively transfer more heat toward the inside diameter of the tube-like heater than the outside diameter of the tube-like heater. This preferential directing of the heat conductivity is beneficial to the design of thermal batteries which use AIN types of heaters.

[0096] In various cases, different battery cells, such as battery cells 112A and 112B can be separated by an electrically insulating layer 115. In some cases, insulating layer 115 can be formed from a composite material containing AIN. Such an insulating layer can further improve heat management by distributing heat laterally over battery cells while isolating these battery cells electrically.

[0097] FIG. IB shows an illustrative embodiment of a thermal battery 101, which can be similar in structure and function to thermal battery 100. Similar to thermal battery 100, thermal battery 101 incudes, multiple battery cells 122 arranged inside enclosure 126. Further, thermal battery 101 includes thermal insulating layers 120A-120C, forming one or more insulating layers within the enclosure. Thermal battery 101 further includes a heater 129 including an element extending through the middle section of enclosure 126. In one example implementation, heater 129 may be an electrical heater. In some cases, the element of heater 129 extending through the central portion of enclosure 126 may have a substantially rectangular shape.

[0098] A detailed view of illustrative battery cells 122A and 122B is provided in the zoomed-in view. These cells can be separated by an electrically insulating layer 125 to ensure proper isolation and functioning.

[0099] In one example embodiment, as shown in FIG. 1C, a battery cell such as battery cell 122A has a semicircular shape and partially surrounds a heating element 129A of heater 129. FIG. ID shows two battery cells, 122A and 122B, surrounding heating element 129A. In some cases, a battery cell can have a circular shape and completely surround heating element 129A. Additionally, battery cell 122A can be separated from battery cell 122B by a horizontally placed heating element 129B. This heating element may be positioned over or within the insulating layer 125 (as shown in FIG. IB). In an example embodiment, heating element 129Bitself forms an insulating layer. For example, heating element 129B may be an electrical heating element encased in aluminum nitride (AIN) material, which is electrically insulating and thermally conductive. In various embodiments, heating element 129 A may be coupled to heating element 129B, allowing both elements to generate heat. Both heating elements 129 A and 129B may comprise electrical heating elements and include resistive heating elements encased in an electrically insulating, thermally conductive layer such as an AIN layer.

[0100] In one embodiment, battery cells 122 have a semicircular shape, arranged in several stacks. For instance, a first stack of battery cells may be positioned on one side of element 129 A and a second stack may be positioned on the opposite side of element 129 A. Thus, element 129A is configured to separate the first stack from the second stack.

[0101] FIG. IE shows another illustrative implementation of a heating element 139, which can be similar to heating element 129A shown in FIG. 1C. However, heating element 139 is configured to extend all the way to the outer diameter of battery cell 132, which can be similar to battery cell 122A shown in FIG. 1C. This extended heating element 139 has more surface area contact with the electrolyte of battery cell 132, thereby imparting more heat to the electrolyte (or controlling heat transfer to battery cell 132).

[0102] Returning to FIG. IB, in addition to heater 129, thermal battery 101 may optionally include additional heaters, such as heater 124 and / or heater 121. Heater 124 may be similar in structure and / or function to heater 114, as shown in FIG. 1A. For example, heater 124 may be positioned radially peripheral to heater 129.

[0103] Heater 121 can be a chemical heater designed to provide initial rapid heating for thermal battery 101. For example, heater 121 can activate a highly exothermic chemical reaction to raise the temperature of the battery to the prescribed level necessary for its operation. Heater 121 may contain sufficient chemical materials to generate enough heat to increase the battery's temperature above the operational threshold, such as 450°C, 500°C, 550°C, 600°C, 650°C, and similar levels. Once the battery's temperature has been sufficiently increased, the temperature can be maintained using heater 129 and / or heater 124. In one embodiment, heater 121 may be activated either prior or concurrently with the activation of heaters 129 and / or 124.

[0104] In some illustrative embodiments, the middle section of enclosure 126 includes a channel that extends substantially through the middle section. Gases heated and / or generated by heater 121 are designed to expand within this channel, transmitting heat to battery cells 122.

[0105] FIG. IB further shows that thermal battery 101 may include a controller 127 configured to manage the operations of thermal battery 101. For example, controller 127 can control the power supplied to heater 129, as well as optional heater 124. Further, controller 127 may be configured to activate heater 121. In some cases, different elements of heater 129, such as 129B, may be configured to generate varying amounts of power, thus controlling the distribution of temperature throughout thermal battery 101.

[0106] FIG. IB also shows that thermal battery 101 may include sensors 128, such as temperature sensors. An example sensor 128A is shown in the zoomed view and may be located next to, or within, insulating layer 125. In one example embodiment, sensors 128 are encapsulated in an electrically insulating material such as aluminum nitride (AIN). As illustrated in FIG. IB, multiple sensors 128 may be present, and data from these sensors is provided to controller 127. This feedback helps controller 127 determine how to adjust power to the various heating elements within thermal battery 101.

[0107] It should be noted that while one particular configuration of heater 129 is shown, heater 129 can have any suitable shape and can be configured to be in thermal contact with the molten salt electrolyte of battery cells 122. Heater 129, in its various configurations, is designed to heat the molten salt electrolyte to a prescribed temperature. In one implementation, for example, heater 129 may be a mesh comprising resistive heating elements encapsulated within AIN material. Additionally, heater 129 may include one or more internal heating elements made of aluminum nitride (AIN), which are in thermal contact with both the heater and the molten salt electrolyte. In some cases, these internal heating elements may not contain resistive heating elements and are used for distributing heat to various regions of battery cells 122.

[0108] In some cases, heater 129 may be formed from heater segments, with electrical current to at least some of these segments controlled via suitable transistors. These transistors are high-temperature transistors designed to withstand temperatures of about 700°C. Examples of such high-temperature transistors include Silicon Carbide (SiC) MOSFETs, Gallium Nitride (GaN) HEMTs, and Silicon-on-Insulator (SOI) MOSFETs. These transistors can be managed via controller 127.

[0109] In various cases, controller 127 is configured to control the power supplied to the different heating elements 129B of heater 129, as well as to heater 124. Controller 127 regulates the power by adjusting the electrical current to these elements. In some instances, the electrical current for these heating elements can be sourced from the power generated by the battery cells 122.

[0110] FIG. 2 shows temperature plots of an example thermal battery, such as thermal battery 100 as a function of time. FIG. 2 shows how a thermal battery performs under different ambient temperatures: -55°C, 25°C, and 60°C. The graph plots the temperature profiles over time for these conditions. All three temperature curves show a sharp increase at the beginning, indicating the activation of the heat source such as, for example, the pyrotechnic heat source, which melts the solid electrolyte and activates the battery.[OHl] At 60°C (plot 210), the thermal battery heats up to around 575°C initially. The temperature then gradually declines over time. At 25°C (plot 220), the battery heats up to approximately 550°C and then cools down gradually. This moderate cooling rate allows the battery to remain operational for a significant duration within the effective temperature range. At -55°C (plot 230), the battery heats up to around 500°C but cools down rapidly, leading to an earlier “Freeze-Out” compared to the other ambient temperatures.

[0112] FIG. 2 also marks the maximum operating temperatures for different cathode materials with red dashed lines: around 625°C for iron disulfide (FeS2) and slightly above 650°C for cobalt disulfide (CoS2). These lines indicate the upper limits for safe and effective battery operation. The gray shaded area represents the effective operational temperature range of the battery for different electrolytes: LiF-NaF-KF in the top part of the shaded area and LiF- LiBr-KBr in the bottom part of the shaded area. As the temperature drops below the top portion of the shaded area, the thermal battery stops operating if it contains LiF-NaF-KF electrolyte due to “Freeze-Out,” where the electrolyte solidifies, halting the electrochemical reactions. Similarly, Freeze-Out occurs when the temperature drops below the bottom portion of the shaded area if the battery contains LiF-LiBr-KBr electrolyte.

[0113] FIG. 2 highlights several aspects of thermal batteries. The initial spike in temperature upon activation is important for starting the battery. The ambient temperature significantly impacts the battery's cooling rate and operational duration, with higher ambient temperatures extending the operational time. The maximum operating temperatures for different cathode materials set the upper limits for safe operation. The ability to maintain functionality over varying environmental conditions makes thermal batteries suitable for high- power, short-duration applications such as military and aerospace use, where reliability is important.

[0114] FIG. 3A shows a design of a thermal battery 301 that does not include heating elements made from a composite material containing AIN, nor does it have an insulating layer with a second inner thermally conductive layer formed from a composite material containingAIN. In contrast, FIG. 3B illustrates an embodiment of a thermal battery 302 where both the heating elements and the insulating layer include a composite material containing AIN. Thermal battery 301 is bulkier and larger due to the need for more insulation and support materials to effectively maintain operating temperatures. Without AIN, thermal battery 301 lacks optimized heat distribution and retention, resulting in less efficient thermal management.

[0115] In contrast, thermal battery 302 incorporates AIN material, resulting in a more compact and efficiently designed structure. AIN is known for its high thermal conductivity and electrical insulation properties, which enhance the battery's thermal management. This allows for more efficient heat distribution and retention, reducing the need for excessive insulation and support materials. Consequently, the battery with AIN is smaller and lighter without compromising performance. The diameter of thermal battery 302 is reduced by about 10 percent, and the height is reduced by a few percent. The compact design allows for reduced insulation and less heat required to reach the target temperatures for the molten salt electrolyte.

[0116] FIG. 4 compares temperature plots for a thermal battery under different ambient temperatures (-55°C, 25°C, and 60°C), incorporating the use of a heater. The temperature profile plots 410-430 demonstrate that the thermal battery heats up rapidly and then the temperature of the thermal battery gradually declines, similar to the profiles shown in FIG. 2. The heater (e.g., tube heater 114, as shown in FIG. 1A) significantly improves thermal management. A plot 440 indicated by the dotted line represents the battery's performance without the heater, showing a rapid temperature decline. In contrast, plot 430 (indicated by a solid line) show improved performance with the heater, extending the operational range and delaying the “Freeze-Out” point.

[0117] In various embodiments, a thermal battery may include separator layers disposed within the molten salt electrolyte, positioned between the anode and cathode elements. These separator layers can be made from a composite material that incorporates aluminum nitride (AIN). The presence of these layers is important for maintaining the physical separation of the anode and cathode, preventing short circuits and ensuring stable operation. The composite material’s inclusion of AIN enhances the thermal and electrical properties, offering better heat management and electrical insulation, which can improve the battery's efficiency and safety.

[0118] The composite material used for the separator layers can include Alumina (AI2O3), Zirconia (ZrCh), or SiC, with dispersed AIN material, such as AIN particles, AIN cylinders, or any other type of AIN elements. These materials are selected fortheir excellent thermal stability and electrical insulation properties. Alumina offers robust thermal stability, Zirconia providestoughness and high-temperature resistance, and Silicon Carbide delivers superior thermal conductivity and mechanical strength. The dispersion of AIN material within these materials further improves their performance by enhancing heat transfer and maintaining electrical insulation, which is important for the reliable operation of the battery under high-temperature conditions.

[0119] In some implementations, composite materials are formed with AIN cylinders. These cylinders provide a structured method to enhance thermal conductivity and mechanical stability within the battery. By forming cylindrical shapes, the AIN material can create efficient pathways for heat transfer, ensuring uniform temperature distribution across the battery components. This configuration not only improves the thermal management of the battery but also adds to its structural integrity, making it more durable and capable of withstanding mechanical stresses during operation.

[0120] Alternatively, the AIN material can be composed of AIN particles. These particles can be uniformly distributed within the composite materials used in the battery, enhancing both thermal conductivity and electrical insulation. The fine distribution of AIN particles ensures that heat is efficiently transferred and dissipated, preventing hotspots and improving the overall performance of the battery. This design choice also contributes to the mechanical strength of the composite materials, making the battery more robust and less prone to failure under thermal cycling and mechanical stress.

[0121] In some cases, multiple different elements can be combined. For example, both AIN particles and cylinders may be present in the composite material.

[0122] In some cases, particular parameters for the geometrical shape of AIN elements, such as the characteristic length of AIN cylinders, the characteristic length of cylinder’s diameters, and / or particles can be used for optimizing the thermal and mechanical properties of a composite material. For example, AIN cylinders might have specific diameters and heights to maximize heat transfer and structural integrity. Similarly, the characteristic size of AIN particles, including their diameter and distribution uniformity, affects the overall performance of the composite material. Fine, evenly distributed AIN particles ensure consistent thermal conductivity and electrical insulation, which are important for the battery's efficiency and reliability.

[0123] In various embodiments, the thermal battery includes insulation layers placed on the inner walls of the enclosure. These insulation layers are used for minimizing heat loss and maintaining the battery's internal temperature. By insulating the inner walls, the battery canretain heat more effectively, ensuring that the molten salt electrolyte remains conductive for extended periods. This enhancement in thermal management improves the battery's efficiency and operational duration, making it suitable for applications that require sustained high power output.

[0124] As described above and reiterated here, the second inner layer (being the second layer of an insulating layer, as discussed above) can be made from a composite ceramic material containing AIN. This layer is designed to enhance the thermal and structural properties of the battery. The inclusion of AIN in the ceramic material ensures efficient heat distribution and retention, which is important for maintaining the battery's performance under high-temperature conditions. Additionally, the ceramic matrix provides mechanical strength and stability, contributing to the overall durability of the battery.

[0125] In some embodiments, the composite ceramic material in the second inner layer can be of molybdenum disilicide reinforced aluminum nitride matrix composite, silicon carbide reinforced aluminum nitride matrix composite, or Kanthal (Iron-Chromium-Aluminum alloy) reinforced aluminum nitride matrix composite.

[0126] Furthermore, in some cases, the composite ceramic material can include Tungsten or Nichrome. These materials are known for their high melting points and excellent thermal and electrical conductivity. Adding Tungsten or Nichrome to the composite material can enhance its thermal management capabilities and electrical performance. This combination ensures that the battery can operate efficiently and reliably under high-temperature conditions.

[0127] The concentration of AIN by volume in the composite ceramic material can be a usable parameter for adjusting the thermal / electrical and / or mechanical properties of such materials. This concentration needs to be optimized to balance thermal conductivity, electrical conductivity, and mechanical properties. By adjusting the volume of AIN, the composite material can achieve the desired performance characteristics, ensuring the battery operates efficiently while maintaining structural integrity and minimizing costs.

[0128] The thermal battery's first outer layer is designed to have low thermal conductivity, with a thermal conductivity of less than 1 Watt per meter per Kelvin (W / (mK)). This low thermal conductivity layer helps to minimize heat loss from the battery, ensuring that the internal temperature remains stable. This is important for maintaining the molten state of the electrolyte and ensuring the battery's efficient operation over its intended lifespan.

[0129] Conversely, the second inner layer containing AIN material has a high thermal conductivity, exceeding a few tens of W / (mK). This high thermal conductivity ensures thatheat is effectively distributed within the battery, preventing localized hotspots and enhancing overall thermal management. This property is important for maintaining the electrolyte in a molten state and ensuring the battery's efficient and reliable performance.

[0130] The concentration of AIN within the composite material may be selected to minimize a cost function associated with the required values for thermal conductivity, electrical conductivity, and mechanical properties. This optimization ensures that the composite material meets the necessary performance standards while remaining cost-effective. By carefully selecting the concentration of AIN, the battery can achieve a balance between performance and cost, making it a viable option for various high-demand applications.

[0131] In some embodiments, internal heating elements of the thermal battery are made from another (second) composite ceramic material containing AIN (e.g., composite material different from the one used for making the second inner layer). These heating elements are important for initiating and maintaining the battery's operation by ensuring the electrolyte remains in a molten state. The use of AIN in the composite material enhances the thermal conductivity of the heating elements, ensuring efficient heat distribution and retention.

[0132] The second composite ceramic material for the internal heating elements can include molybdenum disilicide reinforced aluminum nitride matrix composite, silicon carbide reinforced aluminum nitride matrix composite, or Kanthal reinforced aluminum nitride matrix composite.

[0133] In various embodiments, the concentration of AIN within the second composite material is selected to allow the internal heating elements to undergo temperature cycling between ambient temperature and about 800 degrees Celsius for at least 1000 cycles without mechanical failure. This high durability ensures that the battery can be used in applications requiring frequent thermal cycling, maintaining its performance and structural integrity over an extended period.

[0134] In some embodiments, the second inner layer of insulating layers for thermal battery comprises a first composite ceramic material containing AIN, and the internal heating elements also comprise a second composite ceramic material with AIN. The concentration of AIN by volume in the second ceramic material is higher than in the first ceramic material. This higher concentration of AIN ensures that the heating elements have enhanced thermal conductivity, providing efficient heat distribution and retention, while the second inner layer maintains structural integrity and overall thermal management. In some cases, the concentration of AIN by volume in the second layer may be 10% higher, 20% higher, and the like.

[0135] The internal heating elements of the thermal battery may include extending members that distribute heat within the molten salt electrolyte. These extending members ensure that heat is evenly distributed throughout the electrolyte, preventing localized cooling and maintaining the electrolyte's molten state. This design feature enhances the battery's efficiency and reliability, ensuring consistent performance.

[0136] In various embodiments, the tube heater in the thermal battery can have a coating formed from a composite material containing AIN. This coating enhances the thermal conductivity of the heater, ensuring efficient heat transfer to the electrolyte. The use of AIN in the coating also provides electrical insulation, improving the safety and reliability of the heater.

[0137] The AIN material in the thermal battery may comprise elongated elements that form a thermally conductive percolation network. This network enhances the overall thermal conductivity of the battery, ensuring efficient heat distribution and retention. The percolation network also adds to the mechanical strength of the battery, making it more robust and durable under operational stresses.

[0138] In various embodiments, a thermal battery includes a suitable controller configured to manage its various operations. FIG. 5 illustrates an example method 500 that can be performed by such a controller for operating the thermal battery. Method 500 begins at step 510 with the initiation of the thermal battery's operation using a heating system. At step 510, the controller activates heaters within the heating system, thereby heating the thermal battery. In one example embodiment, the heater could be heater 121, as shown in FIG. IB.

[0139] At step 512, method 500 involves measuring the temperature (Tp) of the battery cells and the molten salt electrolyte after heating the thermal battery by activating the heating system. This measurement is important for determining the current thermal state of the battery and deciding whether additional heating is necessary. Temperature sensors distributed throughout the battery, are configured to provide accurate readings to the controller.

[0140] At step 514, method 500 includes evaluating the measured temperature Tp against a predefined threshold (Tl) to determine if further heating is required. If temperature Tp is below operational threshold Tl (step 514, Yes), method 500 proceeds to step 518, in which one or more heating elements are activated or their power increased. For instance, at step 518, a heater such as heaters 129 or 124, as shown in FIG. IB, may be activated. After activating the heating elements or increasing their power, method 500 proceeds to step 522.

[0141] If temperature Tp is not below operational threshold Tl (step 514, No), method 500 proceeds to step 516 to check if the temperature Tp exceeds a second threshold T2. Iftemperature Tp is above second threshold T2 (step 516, Yes), method 500 proceeds to step 520 to deactivate or reduce the power of one or more heating elements. After completing step 520, method 500 proceeds to step 522. If temperature Tp is not above second threshold T2 (step 516, No), method 500 proceeds directly to step 522.

[0142] At step 522, method 500 includes checking whether the heating system needs to be deactivated. The deactivation may be necessary due to various factors such as power loss in the thermal battery or overheating. If deactivation is required (step 522, Yes), method 500 deactivates the heating system at step 526 and terminates. If deactivation is not required (step 522, No), method 500 proceeds to step 524. Step 524 involves waiting for a predetermined period to allow the battery's temperature to stabilize. After completing step 524, method 500 returns to step 512 to continue monitoring and controlling the battery's temperature.

[0143] FIG. 6 illustrates a controller 600 for controlling various aspects of the operation of a thermal battery, such as thermal battery 100 as shown in FIG. 1 A. In particular embodiments, controller 600 performs one or more steps of the methods described or illustrated herein. Controller 600 also provides the functionality described or illustrated in various embodiments. Additionally, software running on controller 600 can perform one or more steps of the methods or provide the functionality described herein. References to controller 600 may encompass a computing device, and vice versa, where appropriate. Moreover, references to a controller may encompass one or more controllers, where appropriate.

[0144] This disclosure contemplates any suitable number of controllers such as controller 600. Controller 600 can take any suitable physical form. For example, and not by way of limitation, controller 600 may be an embedded computer system, a system-on-chip (SoC), a single-board computer system (SBC) (such as, for example, a computer-on-module (COM) or system-on-module (SOM)), and the like. As an example, and not by way of limitation, controller 600 may perform one or more steps in real-time or in batch mode, or at different times or locations, as described or illustrated herein.

[0145] In particular embodiments, controller 600 may include a processor 601, a memory 602, and a storage 603. Although this disclosure describes and illustrates a particular controller with a specific number of components arranged in a particular manner, it contemplates any suitable controller with any suitable number of components in any suitable arrangement.

[0146] In particular embodiments, processor 601 includes hardware for executing instructions, such as those making up a computer program. As an example, and not by way of limitation, to execute instructions, processor 601 may retrieve (or fetch) the instructions froman internal register, an internal cache, memory 602, or storage 603; decode and execute them; and then write one or more results to an internal register, an internal cache, memory 602, or storage 603. In particular embodiments, processor 601 may include one or more internal caches for data, instructions, or addresses. This disclosure contemplates processor 601 including any suitable number of any suitable internal caches, where appropriate. As an example, and not by way of limitation, processor 601 may include one or more instruction caches, one or more data caches, and one or more translation lookaside buffers (TLBs). Instructions in the instruction caches may be copies of instructions in memory 602 or storage 603, and the instruction caches may speed up retrieval of those instructions by processor 601. Data in the data caches may be copies of data in memory 602 or storage 603 for instructions executing at processor 191 to operate on; the results of previous instructions executed at processor 601 for access by subsequent instructions executing at processor 601 or for writing to memory 602 or storage 603; or other suitable data. The data caches may speed up read or write operations by processor601. The TLBs may speed up virtual-address translation for processor 601. In particular embodiments, processor 601 may include one or more internal registers for data, instructions, or addresses. This disclosure contemplates processor 601 including any suitable number of any suitable internal registers, where appropriate. Where appropriate, processor 601 may include one or more arithmetic logic units (ALUs); be a multi-core processor; or include one or more processors. Although this disclosure describes and illustrates a particular processor, this disclosure contemplates any suitable processor.

[0147] In particular embodiments, memory 602 includes main memory for storing instructions for processor 601 to execute or data for processor 601 to operate on. As an example, and not by way of limitation, controller 600 may load instructions from storage 603 or another source (such as, for example, another controller 600) to memory 602. Processor 601 may then load the instructions from memory 602 to an internal register or internal cache. To execute the instructions, processor 601 may retrieve the instructions from the internal register or internal cache and decode them. During or after the execution of the instructions, processor 601 may write one or more results (which may be intermediate or final results) to the internal register or internal cache. Processor 601 may then write one or more of those results to memory602. In particular embodiments, processor 601 executes only instructions in one or more internal registers or internal caches or in memory 602 (as opposed to storage 603 or elsewhere) and operates only on data in one or more internal registers or internal caches or in memory 602 (as opposed to storage 603 or elsewhere). One or more memory buses (which may each includean address bus and a data bus) may couple processor 601 to memory 602. In particular embodiments, one or more memory management units (MMUs) reside between processor 601 and memory 602 and facilitate access to memory 602 requested by processor 601. In particular embodiments, memory 602 includes random access memory (RAM). This RAM may be volatile memory, where appropriate. Where appropriate, this RAM may be dynamic RAM (DRAM) or static RAM (SRAM). Moreover, where appropriate, this RAM may be singleported or multi-ported RAM.

[0148] In particular embodiments, storage 603 includes mass storage for data or instructions. As an example, and not by way of limitation, storage 603 is a non-volatile, solid- state memory.

[0149] Controller 600 is designed to receive information from sensors 610 and store data from these sensors in storage 603 for further processing. Sensors 610, which are suitable temperature sensors, are strategically placed throughout the thermal battery. The thermal battery may be divided into sections, each equipped with an associated temperature sensor. In one example embodiment, the temperature sensors could be thermocouples capable of measuring temperature within a specific range. For accurate measurements within the range of 0-600°C, sensors such as K-Type thermocouples, RTDs (Resistance Temperature Detectors) with ceramic insulation, and thermistor probes with high-temperature ratings are ideal, as they can withstand temperatures up to 700°C without being damaged.

[0150] In some cases, sensors 610 may include multiple sensors within a particular area, each capable of measuring temperature within a selected range. These sensors ensure accurate monitoring of the thermal battery's temperature profile. For example, such sensors can achieve accuracy up to a few tens of degrees, or within a few degrees, ensuring precise temperature management. To protect the sensors and ensure accurate readings, they can be enclosed within a thermally conductive and electrically insulating material, such as aluminum nitride (AIN). AIN provides excellent thermal conductivity and electrical insulation, making it a suitable material for this application.

[0151] Various aspects of the subject matter disclosed are presented in detail below.

[0152] [A] There is provided a thermal battery comprising: an enclosure; a plurality of battery cells disposed within the enclosure, each battery cell comprising: an anode element; a cathode element; a thermally activated electrolyte disposed at least between the anode element and the cathode element, the thermally activated electrolyte configured to activate battery function at a threshold temperature; and a heater configured to heat the thermally activatedelectrolyte to a prescribed temperature, the heater comprising a heat producing resistive component and aluminum nitride (AIN) material being in thermal contact with the thermally activated electrolyte. At least one pair of the plurality of battery cells may be separated by an electrically insulating material comprising an AIN material; or each one of the plurality of battery cells may be separated by an electrically insulating material comprising an AIN material. The AIN material may comprise aluminum nitride cylinders or aluminum nitride particles. The AIN material may comprise elongated elements forming a thermally conductive percolation network. [B] The thermal battery may further comprise thermal sensors configured to determine temperature distribution within the thermal battery, wherein at least some thermal sensors are insulated by a composite material containing the AIN material. The heater may comprise multiple heating segments, each configured to generate a specific amount of heat output, with the heat output of each heating segment controlled by a controller; each of the multiple heating segments may include a resistive element, and wherein the controller may be configured to control current flowing through the resistive element of each heating segment from the multiple heating segments. In another aspect, each of the multiple heating segments includes a resistive element, and wherein the current provided the heating unit is limited by the total resistance of the heating component, such that a controller is not needed. [C] The thermal battery may further comprise a controller for regulating power delivered to the heater, wherein the controller is configured to supply at least some power to the heater from power generated by the plurality of battery cells. [D] The threshold temperature is greater than 0° C, or the threshold temperature is greater than 100° C, or the threshold temperature is less than 700° C, or the threshold temperature is less than 600° C, or the threshold temperature is less than 500° C, or the threshold temperature is less than 400° C. [E] The threshold temperature is less than 100° C, or less than 0° C, or less than -10° C, or between about -10° C and -55° C.

[0153] In aspects, the heater comprises an element extending through a middle section of the enclosure. Each battery cell from the plurality of battery cells has a disk or an annular cylinder shape or portion thereof; or each battery cell in the plurality of battery cells has a semicylinder shape; and wherein the plurality of battery cells forms a first stack positioned on one side of the element and a second stack positioned on an opposite side of the element, with the element separating the first stack from the second stack. Optionally, the element is substantially rectangular in shape.

[0154] The heater is a first heater, the thermal battery may further comprise a second heater positioned radially peripheral to the first heater, the heater may comprise a tube heater, the tubeheater may comprise a resistive heating element being encased in a material comprising AIN material. The AIN material may be a composite material and may comprise at least 30% by volume AIN, the material may have a minimum thermal conductivity greater than 24W / m-K and insulation being high dielectric strength greater than 14kV / mm and resistivity greater than 10A9 ohm-cm. The resistive element of the heater may be formed from tungsten.

[0155] The second heater is a reactive chemical heater, and the second heater is configured to be activated either prior to or concurrently with an activation of the first heater. The enclosure has a middle section which may include a channel substantially extending through the middle section, and wherein gases heated by the second heater are configured to expand within the channel and transmit heat to the plurality of battery cells.

[0156] [A] The thermal battery may further comprise one or more internal heating elements comprising aluminum nitride (AIN) material, the one or more internal heating elements being in thermal contact with the heater and in thermal contact with at least one of (i) the anode, (ii) the cathode, and (iii) the thermally activated electrolyte. The internal heating elements may include extending members for distributing heat within the thermally activated electrolyte. [B] The thermal battery may comprise a second inner layer comprising a first composite ceramic material containing the AIN material, and the heater comprises a second composite ceramic material containing the AIN material, and wherein concentration of AIN by volume in the second ceramic material is higher than concentration of AIN by volume in the first ceramic material. The second composite ceramic material may be one of molybdenum disilicide reinforced aluminum nitride matrix composite material, silicon carbide reinforced aluminum nitride matrix composite material, or iron-chromium-aluminum alloy reinforced aluminum nitride matrix composite material. [C] Concentration of AIN within the second composite material is selected to allow the internal heating elements to undergo temperature cycling between ambient and about 800° C for at least 1000 cycles without mechanical failure, or at least 1 cycle without mechanical failure.

[0157] The thermal battery having cells separated by an electrically insulating material may also comprise one or more separator layers disposed within the thermally activated electrolyte between anode and cathode elements, the one or more separator layers formed from a composite material comprising the AIN material. The composite material may comprise one of Alumina (AI2O3), Zirconia (ZrCh), or Silicon Carbide (SiC) with dispersed AIN particles.

[0158] [A] A thermal battery wherein the heater may comprise an element that partially surrounds the cathode element and the anode element of each one of the plurality of batterycells. [B] A thermal battery wherein the heater may comprise an element that substantially surrounds the cathode element and the anode element of each one of the plurality of battery cells. [C] The thermal battery having a heater that comprises an element that substantially surrounds the cathode and anode of each battery cell, wherein an outward side of the heater may transfer heat at least ten percent less than an internal side of the heater, and may further comprise thermally insulating layers, each one of the thermally insulating layers comprising: a first outer layer having low thermal conductivity; and a second inner layer containing an AIN material, and the second inner layer comprises a first composite ceramic material containing the AIN material, and the first composite ceramic material is one of molybdenum disilicide reinforced aluminum nitride matrix composite material, silicon carbide reinforced aluminum nitride matrix composite material, or iron-chromium-aluminum alloy reinforced aluminum nitride matrix composite material, and this first composite ceramic material may further comprise one of tungsten or nichrome. The second inner layer may comprise a first composite ceramic material containing the AIN material, and the heater comprises a second composite ceramic material containing the AIN material, and wherein concentration of AIN by volume in the second ceramic material is higher than concentration of AIN by volume in the first ceramic material.

[0159] A thermal battery of the preceding paragraph wherein the first outer low thermal conductivity layer may have a thermal conductivity of less than 1 Watt per meter per Kelvin (W / (mK)), and wherein the second inner layer containing the AIN material may have a thermal conductivity of more than a few tens of W / (mK).

[0160] In the foregoing specification, embodiments of the present disclosure have been described with reference to numerous specific details that may vary from implementation to implementation. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the present disclosure, and what is intended by the applicants to be the scope of the present disclosure, is the literal and equivalent scope of the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction.

[0161] The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particularcomponents, elements, feature, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, features, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Additionally, although this disclosure describes or illustrates particular embodiments as providing particular advantages, particular embodiments may provide none, some, or all of these advantages.

[0162] Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context.

Claims

CLAIMSWhat is claimed is:

1. A thermal battery comprising: an enclosure; a plurality of battery cells disposed within the enclosure, each battery cell comprising: an anode element; a cathode element; a thermally activated electrolyte disposed at least between the anode element and the cathode element, the thermally activated electrolyte configured to activate battery function at a threshold temperature; and a heater configured to heat the thermally activated electrolyte to a prescribed temperature, the heater comprising a heat producing resistive component and aluminum nitride (AIN) material being in thermal contact with the thermally activated electrolyte.

2. The thermal battery of claim 1, wherein the heater comprises an element extending through a middle section of the enclosure.

3. The thermal battery of claim 2, wherein the element is substantially rectangular.

4. The thermal battery of claim 2, wherein each battery cell from the plurality of battery cells has a disk or an annular cylinder shape or portion thereof.

5. The thermal battery of claim 3, wherein each battery cell in the plurality of battery cells has a semicylinder shape, and wherein the plurality of battery cells forms a first stack positioned on one side of the element and a second stack positioned on an opposite side of the element, with the element separating the first stack from the second stack.

6. The thermal battery of claim 2, wherein the heater is a first heater, the thermal battery further comprising a second heater positioned radially peripheral to the first heater.

7. The thermal battery of claim 1, wherein the heater comprises a tube heater, the tube heater comprising a resistive heating element being encased in a material comprising AIN material.

8. The thermal battery of claim 7, wherein the material is sufficiently thermally conductive and sufficiently electrically insulating to enable battery function.

9. The thermal battery of claim 7, wherein the resistive heating element is formed from tungsten.

10. The thermal battery of claim 2, wherein the heater is a first heater, the thermal battery further comprising a second heater, the second heater being a reactive chemical heater, the second heater is configured to be activated either prior or concurrently with an activation of the first heater.

11. The thermal battery of claim 10, wherein the middle section of the enclosure includes a channel substantially extending through the middle section, and wherein gases heated by the second heater are configured to expand within the channel and transmit heat to the plurality of battery cells.

12. The thermal battery of claim 1, further comprising one or more internal heating elements comprising aluminum nitride (AIN) material, the one or more internal heating elements being in thermal contact with the heater and in thermal contact with at least one of (i) the anode, (ii) the cathode, and (iii) the thermally activated electrolyte.

13. The thermal battery of claim 1, wherein each one of the plurality of battery cells is separated by an electrically insulating material comprising an AIN material.

14. The thermal battery of claim 1, wherein at least one pair of the plurality of battery cells is separated by an electrically insulating material comprising an AIN material.

15. The thermal battery of claim 13, further comprising one or more separator layers disposed within the thermally activated electrolyte between anode and cathode elements, the one or more separator layers forming from a composite material comprising the AIN material.

16. The thermal battery of claim 15, wherein the composite material comprises one of Alumina (AI2O3), Zirconia (ZrCh), or Silicon Carbide (SiC) with dispersed AIN particles.

17. The thermal battery of claim 1, wherein the AIN material comprises AIN cylinders.

18. The thermal battery of claim 1, wherein the AIN material comprises:AIN particles, or a substantially continuous ceramic structure.

19. The thermal battery of claim 1, wherein the heater comprises an element that substantially surrounds the cathode element and the anode element of each one of the plurality of battery cells.

20. The thermal battery of claim 1, wherein the heater comprises an element that partially surrounds the cathode element and the anode element of each one of the plurality of battery cells.

21. The thermal battery of claim 19, wherein an outward side of the heater transfers heat at least ten percent less than an internal side of the heater.

22. The thermal battery of claim 19, further comprising thermally insulating layers, each one of the thermally insulating layers comprising: a first outer layer having low thermal conductivity; and a second inner layer containing an AIN material.

23. The thermal battery of claim 22, wherein the second inner layer comprises a first composite ceramic material containing the AIN material.

24. The thermal battery of claim 23, wherein the first composite ceramic material is one of Molybdenum disilicide reinforced aluminum nitride matrix composite material, SiliconCarbide reinforced aluminum nitride matrix composite material, or Iron-Chromium-Aluminum alloy reinforced aluminum nitride matrix composite material.

25. The thermal battery of claim 23, wherein the first composite ceramic material further includes one of Tungsten or Nichrome.

26. The thermal battery of claim 22, wherein the first outer low thermal conductivity layer has a thermal conductivity of less than 1 Watt per meter per Kelvin (W / (mK)).

27. The thermal battery of claim 22, wherein the second inner layer containing the AIN material has a thermal conductivity of more than a few tens of W / (mK).

28. The thermal battery of claim 23, wherein concentration of AIN within the first composite material is selected to minimize a cost function associated with required values for thermal conductivity, electrical conductivity and mechanical properties such that the battery may have a minimum thermal conductivity greater than 24W / m-K and insulation being high dielectric strength greater than 14kV / mm and resistivity greater than 10A9 ohm-cm.

29. The thermal battery of claim 12, wherein the internal heating elements comprise a second composite ceramic material containing the AIN material.

30. The thermal battery of claim 29, wherein the second composite ceramic material is one of Molybdenum disilicide reinforced aluminum nitride matrix composite material, Silicon Carbide reinforced aluminum nitride matrix composite material, or Iron-Chromium-Aluminum alloy reinforced aluminum nitride matrix composite material.

31. The thermal battery of claim 30, wherein concentration of AIN within the second composite material is selected to allow the internal heating elements to undergo temperature cycling between ambient and about 800 degrees for at least 1 cycle or at least about 1000 cycles without mechanical failure.

32. The thermal battery of claim 22, wherein the second inner layer comprises a first composite ceramic material containing the AIN material, and the heater comprises a secondcomposite ceramic material containing the AIN material, and wherein concentration of AIN by volume in the second ceramic material is higher than concentration of AIN by volume in the first ceramic material.

33. The thermal battery of claim 12, wherein the internal heating elements include extending members for distributing heat within the thermally activated electrolyte.

34. The thermal battery of claim 1, wherein the AIN material comprises elongated elements forming a thermally conductive percolation network.

35. The thermal battery of claim 1, further comprising thermal sensors configured to determine temperature distribution within the thermal battery, wherein at least some thermal sensors are insulated by a composite material containing the AIN material.

36. The thermal battery of claim 1, wherein the heater comprises multiple heating segments, each configured to generate a specific amount of heat output, with the heat output of each heating segment controlled by a controller.

37. The thermal battery of claim 36, wherein each of the multiple heating segments includes a resistive element, and wherein the controller is configured to control current flowing through the resistive element of each heating segment from the multiple heating segments.

38. The thermal battery of claim 36, wherein each of the multiple heating segments includes a resistive element, and wherein the current provided to the heater is limited by the total resistance of the heating component.

39. The thermal battery of claim 1, further comprising a controller for regulating power delivered to the heater, wherein the controller is configured to supply at least some power to the heater from power generated by the plurality of battery cells.

40. The thermal battery of claim 1 , wherein the threshold temperature is greater than 100°C.

41. The thermal battery of claim 1, wherein the threshold temperature is greater than 0° C.

42. The thermal battery of claim 1, wherein the threshold temperature is less than 700°C.

43. The thermal battery of claim 42, wherein the threshold temperature is less than about 500° C, or less than about 400° C, or less than about 300° C, or less than about 200° C.

44. The thermal battery of claim 1, wherein the threshold temperature is between about 0° C and about -55° C.

45. The thermal battery of claim 1, wherein the anode element and, or the cathode element is substantially in a liquid state during at least 10% of the battery discharge.

46. An electrochemical battery comprising: an enclosure; one or a plurality of battery cells disposed within the enclosure, each battery cell comprising: an anode element; a cathode element; an electrolyte disposed at least between the anode element and the cathode element, and a heater configured to heat the battery cells to a prescribed temperature, the heater comprising a heat producing resistive component and aluminum nitride (AIN) material being in thermal contact with the electrolyte.

47. The battery of claim 46, where the heater is operational when a temperature in the battery cell is below -10°C.

48. The battery of claim 46, where the heater is operational when the battery discharge is greater than 1W.

49. The electrochemical battery of claim 46, wherein the anode element and, or the cathode element is substantially in a liquid state during at least 10% of the battery discharge.

Images