Storage performance of Mg²⁺ substituted NaMnPO₄ with an olivine structure

Abstract

Magnesium ions have a strong impact on the storage performance of olivine-type NaMnPO4.

Dual‐Ion Intercalation Chemistry Enabling Hybrid Metal‐Ion Batteries

“…[82] The realization of dual Li/ Na intercalation in the full cells operating with Li 4 Ti 5 O 12 anode results in three times higher specific capacities (100 and 60 mAh g À 1 at charge and discharge) in comparison with the full cell working with a single Na intercalation at the cathode and carbon anode (35 and 25 mAh g À 1 ). [82] Another example for higher discharge capacities due to the Li/Na intercalation has been reported in the case of a nanosized NASICON-type Na 3 Fe 2 (PO 4 ) 3 obtained by a mild oxidation of NaFePO 4 maricite (280 °C in the presence of oxygen traces): 150 vs. 90 mAh g À 1 at C/50 rate in Li and Na half-cells, respectively (Figure 4e,f). [81 ] According to ex-situ XRD, HRTEM, and selected area electron diffraction (SAED) studies during the cycling in the Li-electrolytes, the initial NASICON phase Na 3 Fe 2 (PO 4 ) 3 (monoclinic SG C2/ c) undergoes a transformation into lithium NASICON phase having a trigonal structure (R-3) isostructural to Li 3 Fe 2 (PO 4 ) 3 (Figure 4e, f).…”

“…[82] Ex-situ high-resolution transmission electron microscopy (HRTEM) studies reveal that the Li half-cells operate with a dual Li + /Na + intercalation (from the in-situ formed dual electrolyte) into the nano-sized phospho-olivine framework of Mg-NMP as evidenced by the clear differentiation of lithium and sodium phospho-olivine domain structures (LiMnPO 4 and NaMnPO 4 , respectively) in the cycled electrodes. [82] It was also found that the type of the lithium and sodium electrolyte (NaPF 6 , NaTFSI, LiPF 6 , LiBF 4 ) has a significant role on the electrochemical performance, the effect on the specific capacities being more pronounced for the Li-electrolytes of which LiPF 6 (EC/DMC) is the most appropriate (Figure 4c). In Na halfcells a higher discharge capacity and more structured charge/ discharge curves are obtained with NaTFSI in PC (propylene carbonate) containing 5 % NaPF 6 in comparison with pure NaPF 6 electrolyte (Figure 4c).…”

“…[80] (b) Cation distribution in Mg‐NMP (left) and CV curves in Li half‐cells with LiPF 6 electrolyte [82] . (c) Charge‐discharge curves of Mg‐NMP in Na and Li half‐cells and full cells with different electrolytes [82] . (d) CV curves of oxidized NaMnPO 4 maricite in Na and Li half‐cells with NaTFSI and LiPF 6 electrolytes.…”

“…In the Li half‐cells the specific capacities of Mg‐NMP are 146 and 110 mAh g −1 at charging and discharging (C/100 rate), respectively, which exceed with 22 % the values in the Na half‐cells (120 and 90 mAh g −1 , respectively) using PF 6 ‐based electrolytes in the two types of cells (Figure 4c). [82] Ex‐situ high‐resolution transmission electron microscopy (HRTEM) studies reveal that the Li half‐cells operate with a dual Li + /Na + intercalation (from the in‐situ formed dual electrolyte) into the nano‐sized phospho‐olivine framework of Mg‐NMP as evidenced by the clear differentiation of lithium and sodium phospho‐olivine domain structures (LiMnPO 4 and NaMnPO 4 , respectively) in the cycled electrodes [82] . It was also found that the type of the lithium and sodium electrolyte (NaPF 6 , NaTFSI, LiPF 6 , LiBF 4 ) has a significant role on the electrochemical performance, the effect on the specific capacities being more pronounced for the Li‐electrolytes of which LiPF 6 (EC/DMC) is the most appropriate (Figure 4c).…”

“…(a) Cation distribution in NMP (left) and charge-discharge curves in Li half-cell with LiPF 6 electrolyte (right) [80]. (b) Cation distribution in Mg-NMP (left) and CV curves in Li half-cells with LiPF 6 electrolyte [82]. (c) Charge-discharge curves of Mg-NMP in Na and Li half-cells and full cells with different electrolytes [82].…”