What type of study is this?

This is a GITT study (also classified as: DRT, In Situ XRD).

September 10, 2025

Structurally Compatible Anion Substitution for the Enhanced NASICON-Na4Mn1.5Fe1.5(PO4)2P2O7 Cathode

Key Points

Anion substitution resulted in enhanced Na+ mobility, leading to better rate performance during charge-discharge cycles.
The cathode achieved a capacity retention of 85.42% for 500 cycles at 1 C, showcasing its long-term stability.
This study supports the use of SiO4 as a structurally compatible substitute that facilitates charge redistribution and stability.
Overall, this work highlights a promising strategy for optimizing polyanionic frameworks in sodium-ion batteries.

Abstract

The integration of Mn in Na4Mn1.5Fe1.5(PO4)2P2O7 (NMFPP) enhances the energy density but compromises the Na+ mobility and structural stability due to limited electron hopping and pronounced Jahn-Teller effects. To address this, a structurally compatible anionic substitution strategy is implemented by partially replacing PO43- with bulkier and less electronegative SiO44- groups. The reinforced cathode exhibits enhanced rate performance, which is attributed to lattice expansion induced by the larger SiO44- units, thereby facilitating Na+ diffusion and reducing impedance during charge-discharge processes, as supported by GITT and DRT analyses. In addition, the improved cycling stability results from the lower electronegativity of Si, which enables SiO44- to accommodate local charge redistribution without triggering structural collapse, as evidenced by reduced lattice volume fluctuations observed in in situ XRD. Consequently, Na4Mn1.5Fe1.5(PO4)1.95(SiO4)0.05P2O7 achieves a capacity retention of up to 85.42% for 500 cycles at 1 C and 80.54% over 1500 cycles at 5 C. These findings highlight anion substitution as a promising strategy for optimizing polyanionic frameworks toward high-performance sodium-ion batteries.

KI fragen

Bookmark