Synergistic Gd Doping and Coating for High-Rate LiFePO4 Cathodes

To address the demand for high-rate and long-cycle-life cathode materials in the electric vehicle field, this research focuses on overcoming the intrinsic kinetic limitations of lithium iron phosphate (LiFePO4, LFP). By employing the rare-earth element gadolinium (Gd) as a multifunctional modifier, an innovative one-step modification strategy was developed. This approach achieves homogeneous bulk doping of LFP while simultaneously forming a thin protective surface coating in situ. The optimal LFP-1% Gd composite exhibits a high reversible capacity of 157.9 mAh g–1 at 0.1 C, accompanied by significantly reduced electrochemical polarization. Comprehensive characterization confirms that Gd3+ doping effectively expands the crystal lattice, thereby broadening Li+ diffusion pathways. In addition, the concomitant nanoscale surface coating stabilizes the electrode–electrolyte interphase and facilitates charge transfer. This synergistic dual-modification effect results in exceptional long-term cycle performance and superior rate performance. Specifically, it achieves 97.2% capacity retention after 900 cycles at 1 C and delivers 99.2 mAh g–1 at an ultrahigh rate of 20 C. This work elucidates a clear structure-performance relationship and provides a viable material design strategy for developing next-generation lithium-ion battery cathodes with high-rate and high-power.