Quantifying and Inhibiting Manganese Dissolution in Li-Rich Mn-Based Cathode Materials.

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Lithium-rich manganese-based (LRMO) materials are key for high-energy-density cathodes in electronics and electric vehicles.
• Manganese (Mn) dissolution poses a significant challenge, causing structural instability and performance degradation in LRMO cathodes.

Purpose of the Study:

• To elucidate the Mn dissolution mechanism in LRMO materials across various voltage ranges.
• To validate the proposed mechanism and enhance LRMO cathode stability through surface modification.

Main Methods:

• Electrochemical cycling and analysis of Mn dissolution.
• Surface modification using Atomic Layer Deposition (ALD) to apply a LPO nanocoating.
• Quantitative analysis of Mn dissolution levels and voltage retention.

Main Results:

• Mn dissolution mechanisms vary significantly with voltage: Mn4+ reduction and disproportionation (2.5-3.5 V), lattice oxygen release (above 4.3 V), and Jahn-Teller effects/electrolyte reactions (3.5-4.3 V).
• Contrary to expectations, substantial Mn dissolution occurs even in the moderate 3.5-4.3 V range.
• ALD-based LPO nanocoating effectively suppressed electrode/electrolyte side reactions, reduced Mn dissolution, and improved voltage retention.

Conclusions:

• Mn dissolution in LRMO cathodes is a complex, voltage-dependent phenomenon.
• Electrolyte interactions play a critical role in Mn dissolution.
• Surface engineering, specifically LPO nanocoating, is a viable strategy for stabilizing LRMO cathodes.