Nb-doping strategy to enable superior cyclability for high-nickel Li-rich oxide cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Li-rich layered oxides (LLOs) offer high reversible capacity but suffer from voltage decay and capacity degradation, hindering commercial use.
• Increasing nickel (Ni) content in LLOs boosts performance but often reduces cycling stability and capacity.
• Developing stable, high-performance cathode materials is crucial for advanced lithium-ion batteries.

Purpose of the Study:

• To enhance the electrochemical performance of high-nickel lithium-rich manganese-based oxides (LLMO) via niobium (Nb) doping.
• To investigate the stabilizing effect of Nb doping on the crystal structure and cathode electrolyte interfacial stability.
• To provide a novel strategy for designing high-performance Li-rich cathodes for high-energy-density lithium-ion batteries.

Main Methods:

• Synthesis of niobium-doped lithium-rich manganese-based oxides (LLMO-Nb).
• Electrochemical testing including cycling performance, capacity retention, and voltage fade analysis.
• Structural characterization to understand the role of Nb doping on the lattice framework and interfaces.

Main Results:

• The optimized LLMO-Nb3 cathode achieved a discharge capacity of 199 mAh g⁻¹ and energy density of 222 Wh kg⁻¹ after 200 cycles at 1.0C, significantly outperforming pristine LLMO (125 mAh g⁻¹, 136 Wh kg⁻¹).
• Nb doping effectively stabilized the oxygen lattice and suppressed capacity/voltage fading, showing 91.46% capacity retention after 300 cycles (0.5C) and minimal midpoint voltage attenuation (0.8 mV/cycle at 1.0C over 200 cycles).
• Improved cathode electrolyte interfacial (CEI) stability was observed, attributed to the synergistic effect of increased Ni content and Nb doping.

Conclusions:

• Nb doping is a highly effective strategy for enhancing the cycling stability and energy density of high-nickel Li-rich layered oxide cathodes.
• The robust Nb-O bonds and pillaring effect of Nb contribute to structural integrity and suppress performance degradation.
• This research offers valuable insights for designing advanced cathode materials for next-generation high-energy-density lithium-ion batteries.