High-Voltage Phosphate Cathodes for Rechargeable Ca-Ion Batteries

Abstract

Calcium-ion batteries (CIBs) are under investigation as next-generation energy storage devices due to their theoretically high operating potentials and lower costs tied to the high natural abundance of calcium. However, the development of CIBs has been limited by the lack of available positive electrode materials. Here, for the first time, we report two functional polyanionic phosphate materials as high-voltage cathodes for CIBs at room temperature. NaV2(PO4)3 electrodes were found to reversibly intercalate 0.6 mol of Ca2+ (81 mA h g–1) near 3.2 V (vs Ca2+/Ca) with stable cycling performance at a current density of 3.5 mA g–1. The olivine framework material FePO4 reversibly intercalates 0.2 mol of Ca2+ (72 mA h g–1) near 2.9 V (vs Ca2+/Ca) at a current density of 7.5 mA g–1 in the first cycle. Structural, electronic, and compositional changes are consistent with reversible Ca2+ intercalation into these two materials.

A new high-voltage calcium intercalation host for ultra-stable and high-power calcium rechargeable batteries

“…Even with the 50-folds increase in the current density to 500 mA g −1 , nearly 50% of the specific capacity could be still retained, indicating a respectable rate capability. While this power performance does not reach that of the conventional LIBs based on the monovalent lithium ion conduction, it outperforms most other intercalation compounds reported in previous CIBs, e.g., 38 mAh g −1 at 400 mA g −1 for VOPO 4 ·2H 2 O cathode 25 , and 45 mAh g −1 at 117 mA g −1 for NaV 2 (PO 4 ) 3 cathode 26 . Moreover, it is noteworthy that the primary particles of our material are a few micrometers in size (Supplementary Fig.…”

Solvation, Rational Design, and Interfaces: Development of Divalent Electrolytes

“…In MV-metal batteries, the overall energy density is determined by that of the cathode. Viable MV cathodes have been limited to sulfides, selenides, and organic cathode materials, but do not surpass the energy density of Li-ion batteries (Gu et al, 2015;Kwon et al, 2020b;Kim et al, 2020;Liang et al, 2020).…”

Through the Maze of Multivalent‐Ion Batteries: A Critical Review on the Status of the Research on Cathode Materials for Mg2+ and Ca2+ Ions Insertion

“…Recently, Kim et. al [62] . reported the synthesis and electrochemical investigations on desodiated NaV 2 (PO 4 ) 3 and delithiated LiFePO 4 materials, focusing on Ca cation insertion/extraction at room temperature.…”