A New Class of High‐Capacity Fe‐Based Cation‐Disordered Oxide for Li‐Ion Batteries: Li‐Fe‐Ti‐Mo Oxide

Abstract

Low‐cost Fe can be used for forming cation‐disordered rocksalt Li‐excess (DRX) materials instead of high‐cost d0‐species and then the Fe‐based DRX can be promising electrode materials because they can theoretically achieve high capacity, resulting from additional oxygen redox reaction and stable cation‐disordered structure. However, Fe‐based DRX materials suffer from large voltage hysteresis, low electrochemical activity, and poor cyclability, so it is highly challenging to utilize them as practical electrode materials for a cell. Here, novel high‐capacity Li‐Fe‐Ti‐Mo electrode materials (LFTMO) with high average discharge voltage and reasonable stability are reported. The effect of Ti/Mo on electrochemical reactions in Fe‐based DRX materials (LFTMO) is studied by controlling its composition ratio and using techniques for analyzing the local environment to find the key factors that improve its activity. It is found out that the introduction of appropriate quantity of redox‐active Mo4+/5+ to Fe‐based DRX materials can help stabilize the oxygen redox reaction via changing a local structure and can suppress a Fe redox reaction, which can cause poor performance. The understandings will help develop high capacity and long cyclability Fe‐based DRX electrode materials.

Regulating d0 transition metals and facilitating high-performance Li-excess cation-disordered rock salt cathode materials

“…These oxides and oxy-fluoride materials usually exhibit superior capacity exceeding 300 mA h g −1 and consist of earth-abundant elements, which could alleviate the gap between the market requirement and electrochemical properties and are thus promising for advanced LIBs. 18–22…”

“…31–33 A large amount of DRX materials were realized, which contained one or more d 0 metals in the compounds, such as Ti 4+ , Zr 4+ , Nb 5+ and Mo 6+ . 18,34–38 To explore DRX materials with better electrochemical properties, various d 0 transition metals with different contents were applied, leading to the diverse electrochemical performance. Yang et al applied different Nb contents in the Fe-based DRXs, Li 1+ x Nb x Fe 1−2 x O 2 (0 ≤ x ≤ 0.35), which showed that the DRX cathode material with a Nb content of 0.25 has excellent electrochemical performance with an initial discharge capacity of more than 250 mA h g −1 .…”