A Gradient Doping Strategy toward Superior Electrochemical Performance for Li-Rich Mn-Based Cathode Materials

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Lithium-rich layered oxides (LLOs) offer high reversible capacities (>250 mA h g⁻¹) for next-generation lithium-ion batteries.
• Critical drawbacks including oxygen release, structural degradation, and poor kinetics limit LLO commercialization.

Purpose of the Study:

• To enhance the electrochemical performance of LLOs by tuning their local electronic structure.
• To improve capacity retention, energy density, and rate performance through gradient doping.

Main Methods:

• Gradient doping of LLOs with tantalum (Ta5+).
• Electrochemical testing to evaluate capacity retention and rate performance.
• Theoretical calculations (density of states, oxygen vacancy formation energy) to understand doping effects.

Main Results:

• Capacity retention improved from 73% to over 93% after 200 cycles at 1 C.
• Energy density increased from 65% to over 87% under the same conditions.
• Ta5+ doped LLOs showed higher discharge capacity (155 mA h g⁻¹ at 5 C) compared to undoped LLOs (122 mA h g⁻¹).
• Doping increased oxygen vacancy formation energy, enhancing structural stability.
• Electronic conductivity of LLOs was significantly boosted.

Conclusions:

• Gradient Ta5+ doping effectively improves the structural stability and electronic conductivity of LLOs.
• This doping strategy enhances energy density retention and rate performance, addressing key limitations of LLOs.
• Modulating the local structure via gradient doping offers a promising approach for advancing LLO cathode materials.