Analysis of Minerals as Electrode Materials for Ca-based Rechargeable Batteries

Abstract

Rechargeable lithium-ion batteries dominate the consumer electronics and electric vehicle markets. However, concerns on Li availability have prompted the development of alternative high energy density electrochemical energy storage systems. Rechargeable batteries based on a Ca metal anode can exhibit advantages in terms of energy density, safety and cost. The development of rechargeable Ca metal batteries requires the identification of suitable high specific energy cathode materials. This work focuses on Ca-bearing minerals because they represent stable and abundant compounds. Suitable minerals should contain a transition metal able of being reversibly reduced and oxidized, which points to several major classes of silicates and carbonates: olivine (CaFeSiO 4 ; kirschsteinite), pyroxene (CaFe/MnSi 2 O 6 ; hedenbergite and johannsenite, respectively), garnet (Ca 3 Fe/Cr 2 Si 3 O 12 ; andradite and uvarovite, respectively), amphibole (Ca 2 Fe 5 Si 8 O 22 (OH) 2 ; ferroactinolite) and double carbonates (CaMn(CO 3 ) 2 ; kutnahorite and CaFe(CO 3 ) 2 ; ankerite). This work discusses their electrode characteristics based on crystal chemistry analysis and density functional theory (DFT) calculations. The results indicate that upon Ca deintercalation, compounds such as pyroxene, garnet and double carbonate minerals could display high theoretical energy densities (ranging from 780 to 1500 Wh/kg) with moderate structural modifications. As a downside, DFT calculations indicate a hampered Ca mobility in their crystal structures. The overall analysis then disregards olivine, garnet, pyroxene, amphibole and double carbonates as structural types for future Ca-cathode materials design.

Defects and Dopants in CaFeSi2O6: Classical and DFT Simulations

“…High activation energies reveal that very slow Ca-ion diffusion would be expected in CaFeSi 2 O 6 . Table 4 reports the activation energies calculated in previous DFT modelling in different Ca-based electrode materials [11,12]. In general, high activation energy is noted.…”

“…A variety of compounds such as garnets (e.g., Ca 3 Fe 2 Si 3 O 12 ), pyroxenes (e.g., CaMnSi 2 O 6 ), double carbonates (e.g., CaMg(CO 3 ) 2 ), marokites (e.g., CaMn 2 O 4 ) have been tested as cathode materials for application in Ca-ion batteries experimentally or theoretically [11,12]. In a combined experimental and theoretical study on CaMn 2 O 4 by Arryo-de Dompablo et al [12], it was concluded that deinsertion of Ca ions from CaMn 2 O 4 is hard, and this was further confirmed by the high activation energy (1.00 eV) calculated for the Ca-ion migration.…”

“…In a combined experimental and theoretical study on CaMn 2 O 4 by Arryo-de Dompablo et al [12], it was concluded that deinsertion of Ca ions from CaMn 2 O 4 is hard, and this was further confirmed by the high activation energy (1.00 eV) calculated for the Ca-ion migration. In a DFT (Density Functional Theory) study by Torres et al [11]…”

Appraisal of calcium ferrites as cathodes for calcium rechargeable batteries: DFT, synthesis, characterization and electrochemistry of Ca4Fe9O17

“…Sustainable cathode materials should include abundant and non-toxic elements, and at the same time, comply with the high energy density requirements. These criteria prompted the investigation of light and abundant oxidizing 3d-transition † Electronic supplementary information (ESI) available: 26 and CaMnSi 2 O 6 ( johannsenite). 26 In contrast, research on Fe oxides has been scarce; the perovskite CaFeO 3 and the related brownmillerite Ca 2 Fe 2 O 5 compounds have been only evaluated by computational means.…”

“…These criteria prompted the investigation of light and abundant oxidizing 3d-transition † Electronic supplementary information (ESI) available: 26 and CaMnSi 2 O 6 ( johannsenite). 26 In contrast, research on Fe oxides has been scarce; the perovskite CaFeO 3 and the related brownmillerite Ca 2 Fe 2 O 5 compounds have been only evaluated by computational means. 16,23 It was found that Ca-perovskites are not competitive materials due to hindered Ca mobility (a calculated energy barrier of 2 V).…”