Liquid-metal electrode to enable ultra-low temperature sodium–beta alumina batteries for renewable energy storage

Abstract

Commercial sodium-sulphur or sodium-metal halide batteries typically need an operating temperature of 300-350°C, and one of the reasons is poor wettability of liquid sodium on the surface of beta alumina. Here we report an alloying strategy that can markedly improve the wetting, which allows the batteries to be operated at much lower temperatures. Our combined experimental and computational studies suggest that addition of caesium to sodium can markedly enhance the wettability. Single cells with Na-Cs alloy anodes exhibit great improvement in cycling life over those with pure sodium anodes at 175 and 150°C. The cells show good performance even at as low as 95°C. These results demonstrate that sodium-beta alumina batteries can be operated at much lower temperatures with successfully solving the wetting issue. This work also suggests a strategy to use liquid metals in advanced batteries that can avoid the intrinsic safety issues associated with dendrite formation.

Low-Temperature Molten Salt Electrolytes for Membrane-Free Sodium Metal Batteries

“…anode: A liq → A z+ + ze − [1] cathode: A z+ + ze − → A(in B) liq [2] overall: A liq → A(in B) liq [3] E cell,eq = − Ḡ cell z F = − RT z F lna A(in B)liq [4] Because all three active battery components are liquid phase, the system is able to operate at high current densities with minimal overpotential losses. In addition, because the cell is restored to its virgin liquid state upon each recharge, the device is immune to solid-state failure mechanisms common in lithium-ion batteries 3 and, as a result, is expected to provide exceptionally long amortizable service lifetimes.…”

“…As a result, there is great interest in lowering the operating temperature of the device through careful selection of the three active components. Because there are a variety of earth-abundant and low-temperature anode 2,4 and cathode metals 1 and alloys the component that most frequently sets the operating temperature of the device is the molten salt electrolyte. Such dependencies motivate the search for newer and lower-melting electrolytes to unlock both lower temperature battery designs as well as cheaper device operating costs on a $/kWh-cycle basis.…”

Enhanced sintering of β″-Al2O3/YSZ with the sintering aids of TiO2 and MnO2

“…To measure the ionic conductivity of the electrolyte, a symmetric electrochemical cell was employed and both of electrodes of the cell were NaeCs alloy (molar ratio of 1:4). The NaeCs alloy shows excellent wetting performance on the surface of b 00 -Al 2 O 3 , which, therefore, can ensure an intimate contact between the electrode/electrolyte interface [31]. The impedance spectra of the symmetric cell were collected with an electrochemical interface (Solartron 1287, Solartron Analytical) and a frequency response analyzer (Solartron 1260, Solartron Analytical) under open-circuit voltage (OCV).…”

A thermo-mechanical stress prediction model for contemporary planar sodium sulfur (NaS) cells

“…Accordingly, planar cell designs have been adopted for developing electrode materials/structures and for testing new cell chemistries with small circular plate-shaped BASE, of which diameter is typically in the range of 10e50 mm. For example, there are several recent efforts to reduce the operation temperatures of NaS battery systems from 300e350 C to intermediate temperatures (95e190 C) [21,22] or to room temperature [23e28]. In addition to these, the planar design is also useful for fundamental studies on the wetting characteristics of molten sodium on b/b 00 -Al 2 O 3 membrane [29,30], or on testing novel electrodes for sodium metal halide chemistries [31e33].…”