Provided is a sodium secondary battery capable of operating at a low temperature. More particularly, the sodium secondary battery according to the present invention includes: an anode containing sodium; a cathode containing a transition metal and an alkali metal halide; and a sodium ion conductive solid electrolyte provided between the anode and the cathode, wherein the cathode is impregnated in a molten salt electrolyte containing a sodium.metal halogen salt including at least two kinds of halogens.

The disclosure provides seals for devices that operate at elevated temperatures and have reactive metal vapors, such as lithium, sodium or magnesium. In some examples, such devices include energy storage devices that may be used within an electrical power grid or as part of a standalone system. The energy storage devices may be charged from an electricity production source for later discharge, such as when there is a demand for electrical energy consumption.

A method for joining a ceramic component to a metallic component is described. At least one initial layer of an active metal is applied to one of the joining surfaces, by a cold spray technique. At least one second layer of a nickel-based braze composition is then applied over the initial layer by cold-spraying. The braze composition and components are then heated, so as to form an active braze joint between them. A method of sealing an open region of a sodium metal halide-based battery is also disclosed, using the brazing technique described herein to form braze joints that seal various components in the battery cells, such as metallic rings and ceramic collar structures.

A fuel cell system includes a fuel cell module for generating electrical energy by electrochemical reactions of a fuel gas and an oxygen-containing gas, a condenser for condensing water vapor in an exhaust gas discharged from the fuel cell module by heat exchange between the exhaust gas and a coolant to collect the condensed water and supplying the collected condensed water to the fuel cell module. The condenser includes an air cooling condensing mechanism using the oxygen-containing gas as the coolant. The air cooling condensing mechanism includes a secondary battery for inducing endothermic reaction during charging and inducing exothermic reaction during discharging.

A battery is provided with an associated method for transporting metal-ions in the battery using a low temperature molten salt (LTMS). The battery comprises an anode, a cathode formed from a LTMS having a liquid phase at a temperature of less than 150 C., a current collector submerged in the LTMS, and a metal-ion permeable separator interposed between the LTMS and the anode. The method transports metal-ions from the separator to the current collector in response to the LTMS acting simultaneously as a cathode and an electrolyte. More explicitly, metal-ions are transported from the separator to the current collector by creating a liquid flow of LTMS interacting with the current collector and separator.

An intermediate temperature molten sodium-metal halide rechargeable battery utilizes a molten eutectic mixture of sodium haloaluminate salts having a relatively low melting point that enables the battery to operate at substantially lower temperature compared to the traditional ZEBRA battery system and utilize a highly conductive NaSICON solid electrolyte membrane. The positive electrode comprises a mixture of NaX and MX, where X is a halogen selected from Cl, Br and I and M is a metal selected Ni, Fe, and Zn. The positive electrode is disposed in a mixed molten salt positive electrolyte comprising at least two salts that can be represented by the formula NaAlX.sub.4-X.sub., where 0<<4, wherein X and X are different halogens selected from Cl, Br and I. The positive electrode may include additional NaX added in a molar ratio ranging from 1:1 to 3:1 of NaX:NaAlX.sub.4-X.sub..

An energy storage system comprising a molten alkali metal in contact with a layer disposed on a surface of a substrate, wherein the surface layer comprises a composite comprising carbon, and the surface layer is metal-free and metal oxide-free.

Provided herein are energy storage devices. In some cases, the energy storage devices are capable of being transported on a vehicle and storing a large amount of energy. An energy storage device is provided comprising at least one liquid metal electrode, an energy storage capacity of at least about 1 MWh and a response time less than or equal to about 100 milliseconds (ms).

Disclosed herein are methods and systems for monitoring and/or regulating energy storage devices. Examples of such monitoring and/or regulating include cell balancing, dynamic impedance control, breach detection and determination of state of charge of energy storage devices.

A separator for a metal conversion battery can include an alkali metal-conducting ceramic material, where at least five convex curves and at least five concave curves can define a closed transverse cross-sectional profile of the separator, where the transverse cross-sectional profile can be perpendicular to a longitudinal axis of the separator.