A New Class of Ternary Compound for Lithium-Ion Battery: from Composite to Solid Solution

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• High-performance cathode materials are essential for developing advanced lithium-ion batteries (LIBs) with high-energy densities for electric vehicles (EVs).
• Lithium-rich Li₂MnO₃ offers high capacity but suffers from poor structural stability and electronic conductivity.
• Replacing Mn⁴⁺ with Sn⁴⁺ in Li₂MnO₃ aims to improve stability, but ionic radius differences cause phase separation during synthesis.

Purpose of the Study:

• To overcome phase separation issues in Li₂MnO₃-Li₂SnO₃ systems.
• To explore the formation of a single solid-solution phase using a ruthenium buffer agent.
• To investigate the impact of ruthenium content and Mn/Sn molar ratios on electrochemical performance.

Main Methods:

• Synthesis of Li₂RuO₃-Li₂MnO₃-Li₂SnO₃ ternary systems with varying ruthenium content.
• Analysis of phase evolution from composite to single solid-solution phases.
• Electrochemical testing to evaluate discharge capacity, cycling stability, and kinetics.

Main Results:

• The Li₂RuO₃-Li₂MnO₃-Li₂SnO₃ system transitions to a single solid-solution phase with increasing ruthenium content.
• Discharge capacity significantly increases at the phase transformation point due to improved Li⁺/e^- transportation and anionic redox chemistry.
• Higher tin content enhances cycling stability by suppressing structural transformation from layered-to-spinel phases.

Conclusions:

• Ruthenium acts as an effective buffer agent to form stable solid-solution phases in lithium-rich cathode materials.
• The developed ternary system demonstrates improved electrochemical performance, offering a new route for advanced LIB cathode exploration.
• This research paves the way for designing novel ternary and quaternary lithium-rich cathode materials for high-energy density applications.