Mechanically and Chemically Co-Robust Ni-Rich Cathodes with Ultrahigh Capacity and Prolonged Cycle Life

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Nickel-rich layered oxide (NRLO) materials are promising cathodes for lithium-ion batteries (LIBs).
• NRLOs suffer from capacity loss and instability due to chemical and mechanical failures during cycling.
• Doping is a potential strategy to enhance NRLO performance, but mechanisms remain unclear.

Purpose of the Study:

• To investigate the effects of high-valent Nb ion doping on NRLO materials.
• To understand the mechanical-chemical coupling regulation mechanism for improved electrochemical performance.
• To enhance the capacity and cycle life of NRLOs through Nb doping.

Main Methods:

• Nb5+ doping was introduced into NRLO materials.
• Characterization of grain refinement, grain boundary stabilization, and phase transition behavior.
• Analysis of Li diffusion barriers, oxygen release, and transition metal/Li antisite mixing.

Main Results:

• Nb doping refined secondary grains and stabilized grain boundaries, creating an intergrain fusion structure.
• This structure dissipated lattice strain, suppressed oxygen loss, and prevented cycling-induced cracks.
• Nb doping stabilized the monoclinic phase, promoted stable spinel twin boundaries, reduced Li diffusion barriers, and mitigated rock-salt phase formation.

Conclusions:

• Nb doping significantly enhances the capacity and cycle life of NRLOs.
• The study provides a comprehensive understanding of Nb-doping mechanisms, highlighting synergistic mechanical-chemical coupling.
• Nb-doped NRLOs show great potential for advanced lithium-ion battery applications.