Stabilizing Layered Oxide Cathodes Based on Universal Surface Residual Alkali Conversion Chemistry for Rechargeable...

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Layered transition metal oxides (LTMOs) offer high theoretical capacity for rechargeable batteries.
• LTMOs face challenges like capacity fading, voltage decay, and poor kinetics due to oxygen evolution and unstable interfaces.
• Residual alkali species on LTMOs hinder their practical application.

Purpose of the Study:

• To develop a universal strategy for in situ conversion of surface residual alkali into a stable polymer coating on LTMOs.
• To address interfacial instability and improve the electrochemical performance of LTMOs.
• To demonstrate the broad applicability of the strategy for various LTMOs.

Main Methods:

• Treatment of LTMOs with ammonium fluoride (NH4F) to consume residual alkali.
• Induction of ring-opening polymerization of tetrahydrofuran using generated fluorides to form a polymer coating.
• Implementation and testing of the coated Li-rich Mn-based cathode materials (LRM) in lithium-ion batteries.
• Application of the strategy to sodium-rich LTMOs for sodium-ion batteries.

Main Results:

• The polymer coating significantly reduces voltage hysteresis and enhances kinetics and cycling stability in lithium-ion batteries.
• The coating effectively alleviates surface lattice oxygen release and layered-to-spinel phase transitions.
• Minimal mechanical degradation and surface parasitic reactions were observed.
• The strategy proved effective for air-sensitive sodium-rich LTMOs, showcasing its universality.

Conclusions:

• The proposed strategy offers a promising solution for overcoming residual alkali and interfacial instability issues in LTMOs.
• The in situ polymer coating enhances the performance and stability of LTMO-based batteries.
• This approach demonstrates broad applicability for both lithium-ion and sodium-ion battery systems.