Robust diamond-like Fe-Si network in the zero-strain NaxFeSiO4 Cathode

TL;DR

This paper investigates the crystal structure and stability of Na2FeSiO4, a sodium iron orthosilicate with a diamond-like Fe-Si network, demonstrating its high structural stability during charge/discharge cycles through theoretical and experimental analysis.

Contribution

It provides a detailed analysis of the crystal structure and stability of Na2FeSiO4, highlighting the robustness of the Fe-Si network during electrochemical processes.

Findings

High structural stability of Na2FeSiO4 during sodium insertion/extraction

Good agreement between calculated and experimental voltages

Identification of a robust diamond-like Fe-Si network

Abstract

Sodium orthosilicates Na2MSiO4 (M denotes transition metals) have attracted much attention due to the possibility of exchanging two electrons per formula unit. In this work, we report a group of sodium iron orthosilicates Na2FeSiO4, the crystal structures of which are characterized by a diamond-like Fe-Si network. The Fe-Si network is quite robust against the charge/discharge process, which explains the high structural stability observed in experiment. Using the density functional theory within the GGA+U framework and X-ray diffraction studies, the crystal structures and structural stabilities during the sodium insertion/deinsertion process are systematically investigated. The calculated average deintercalation voltages are in good agreement with the experimental result.