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With the increasing amount of renewable energy produced, many governments and industries are pushing for the installation of battery energy storage system (BESS) solutions. Thermal batteries are systems that store heat made from various energy sources, and can be used to produce electricity upon demand. These systems are easily scalable and can be installed in cities, homes and remote locations. Thermochemical energy storage (TCES) uses the enthalpy of a chemical reaction to store and release heat through endothermic and exothermic processes, respectively. CaCO3 has been identified as an ideal TCES material as it is cheap and abundant, but maximising long-term cyclability is key to ensure battery longevity. This article investigates the addition of CaSiO3, CaTiO3 and CaZrO3 to CaCO3 in a 1 : 1 ratio to ascertain the reaction properties and cyclic capacity over time. Cycling longevity and thermodynamic properties were determined using simultaneous differential scanning calorimetry and thermogravimetric analysis (DSC–TGA) along with the Sieverts technique, and their reaction pathway studied by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The low cost of the CaCO3–CaSiO3 material of $1.8 USD per kW hth suggests that if a suitable particle refinement agent were to be employed to ensure cycling longevity this material would be an excellent TCES material. Despite the CO2 cycling capacity of the CaCO3–CaZrO3 system only reducing by 16 wt% over 100 cycles, the cost of ZrO2 brings the materials cost to $30.9 USD per kW hth, making this material currently unsuitable for application. The CaCO3–CaTiO3 system showed only a 17% drop in total CO2 uptake over 100 cycles, although the cost was $11.1 USD per kW hth. [ABSTRACT FROM AUTHOR]

Alternatives to fossil fuels are necessary to reduce greenhouse gas emissions, and energy storage is crucial to transition to renewable energy. Thermochemical energy storage is one option to store energy for 24/7 utilisation, and as such, the reversible carbonation of the Ca : Mg : Fe oxide system was investigated to determine its feasibility as a thermochemical energy storage material. The Ca : Mg : Fe (1 : 1 : 1) sample synthesised from co-crystallisation of metal acetates retained reversible CO2 sorption at 90% over 100 cycles, thus the associated physical properties were thoroughly investigated. Powder X-ray diffraction analyses indicated the formation of dicalcium ferrite and magnesioferrite, respectively in the decarbonated and carbonated states, which suggested a synergistic effect enhancing the reversible sorption of CO2 in the 2CaO·Fe2O3·MgO intermediate system involved in the reaction mechanism. The thermodynamics of the reactions were determined using pressure-composition-isotherm measurements, resulting in calculated enthalpies and entropies of ΔHabs = −146 ± 5 kJ mol−1 and ΔSabs = −141 ± 5 J mol−1 K−1, and ΔHdes = 178 ± 4 kJ mol−1 and ΔSdes = 167 ± 4 J mol−1 K−1 for CO2 absorption and desorption, respectively. The application of the Kissinger method determined an activation energy of 203 ± 14 kJ mol−1 for the decarbonation reaction. The maximum energy storage density of the system was evaluated to be 468 kJ kg−1 with an operating temperature of ≈750 °C. Overall, the Ca–Mg–Fe system can integrate thermochemical batteries and is promising to promote thermochemical energy storage for backing up power production using renewables. [ABSTRACT FROM AUTHOR]

Metal hydroborates and their derivatives have been receiving attention as potential solid-state ion conductors for battery applications owing to their impressive electrochemical and mechanical characteristics. However, to date only a fraction of these compounds has been investigated as solid-state electrolytes. Here, MB12H11NH3 (M = Li and Na) hydroborates are synthesized and investigated as electrolyte materials for all-solid-state batteries. The room temperature #945;-NaB12H11NH3 was structurally solved in P212121 (a = 7.1972(3) Å, b = 9.9225(4) Å, and c = 14.5556(5) Å). It shows a polymorphic structural transition near 140 °C to cubic Fm3m. LiB12H11NH3 and NaB12H11NH3 exhibit cationic conductivities of σ(Li+) = 3.0 × 10-4 S cm-1 and σ(Na+) = 1.2 × 10-4 S cm-1 at 200 °C. Hydration is found to improve ionic conductivity of the hydroborates. It is presumed that modest ionic conductivities could be due to a lack of significant reorientational dynamics in the crystal structure resulting from the presence of the bulky -NH3 group in the anion. [ABSTRACT FROM AUTHOR]

Research into the use of sodium tetraalkoxyborate salts for different chemical applications including synthetic catalysis, hydrogen storage, or battery applications has been investigated, however, understanding of the structural, thermal and electrochemical properties of these salts has been lacking since the 1950s and 1960s. A review of the synthesis, as well as a thorough characterization using 1H NMR, 11B NMR, 13C{1H} NMR, FTIR, XRD, in situ XRD, DSC-TGA, RGA-MS, TPPA, and EIS has newly identified polymorphic phase changes for Na[B(OMe)4], K[B(OMe)4], Li[B(OMe)4], Na[B(OEt)4], Na[B(OBu)4], and Na[B(OiBu)4]. The crystal structure of K[B(OMe)4] was also solved in I41/a (a = 22.337(2) Å, c = 7.648(3) Å, V = 3815.6(4) Å3, ρ = 1.128(1) g cm−3). Ionic conductivity of the different salts was analyzed, however it was found that the compounds with longer alkyl chains had no measurable ionic conductivity compared to the shorter chained samples, Na[B(OMe)4] and K[B(OMe)4] with 9.6 × 10−8 S cm−1 and 1.6 × 10−7 S cm−1, at 114 °C respectively. [ABSTRACT FROM AUTHOR]

Metal substituted dodecaborate anions can be coupled with alkali metal cations to have great potential as solid-state ion conductors for battery applications. A tin atom can replace a B–H unit within an unsubstituted dodecaborate cage to produce a stable, polar divalent anion. The chemical and structural change in forming a stannaborate results in a modified crystal structure of respective group 1 metal salts, and as a result, improves the material's ion conductivity. Li2B11H11Sn shows high ion conductivity of ∼8 mS cm−1 at 130 °C, similar to the state-of-the-art LiCB11H12 at these temperatures, however, obtaining high ion conductivity at room temperature is not possible with pristine alkali metal stannaborates. [ABSTRACT FROM AUTHOR]

Renewable energy requires cost effective and reliable storage to compete with fossil fuels. This study introduces a new reactive carbonate composite (RCC) where Fe2O3 is used to thermodynamically destabilise BaCO3 and reduce its decomposition temperature from 1400 °C to 850 °C, which is more suitable for thermal energy storage applications. Fe2O3 is consumed on heating to form BaFe12O19, which is a stable Fe source for promoting reversible CO2 reactions. Two reversible reaction steps were observed that corresponded to, first, the reaction between β-BaCO3 and BaFe12O19, and second, between γ-BaCO3 and BaFe12O19. The thermodynamic parameters were determined to be ΔH = 199 ± 6 kJ mol−1 of CO2, ΔS = 180 ± 6 J K−1 mol−1 of CO2 and ΔH = 212 ± 6 kJ mol−1 of CO2, ΔS = 185 ± 7 J K−1 mol−1 of CO2, respectively, for the two reactions. Due to the low-cost and high gravimetric and volumetric energy density, the RCC is demonstrated to be a promising candidate for next generation thermal energy storage. [ABSTRACT FROM AUTHOR]