High-Entropy Li-Rich Layered Cathodes with Negligible Voltage Decay through Migration Retardation Effect

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Advanced Li- and Mn-rich layered oxides (LRO) are crucial for high-energy lithium-ion batteries (LIBs).
• LRO materials suffer from significant voltage hysteresis and decay due to irreversible transition metal (TM) migration during cycling.

Purpose of the Study:

• To synthesize a high-entropy Li_1.17Mn_0.50Ni_0.12Co_0.12Mg_0.03Cu_0.02Ti_0.02Nb_0.02O₂ (HELRO) cathode for LIBs.
• To investigate the mechanisms behind improved voltage retention and energy output in HELRO.
• To understand the structural degradation and manganese migration in HELRO during prolonged cycling.

Main Methods:

• Synthesis of a novel high-entropy oxide cathode (HELRO).
• Electrochemical cycling and performance testing of HELRO in LIBs.
• Analysis of structural degradation and ion migration using advanced characterization techniques.

Main Results:

• The synthesized HELRO cathode demonstrated significantly improved voltage retention and energy output compared to conventional LRO.
• HELRO exhibited sluggish degradation of superlattice and local structures during long-term charge-discharge cycles.
• The "migration retardation effect" was observed, attributed to higher configurational entropy increasing energy barriers for Mn migration.

Conclusions:

• High-entropy design effectively suppresses voltage decay in Li- and Mn-rich layered cathodes.
• Synergistic ionic-covalent enhancement of Mn─O bonds in HELRO contributes to migration retardation.
• This study provides insights into high-entropy cathode mechanisms and demonstrates a viable strategy for suppressing voltage decay in LIBs.