Na/Co dual-doped olivine LiMn_0.6Fe_0.4PO₄ cathode with superior reaction kinetics for Li-ion batteries

Olivine-type lithium manganese iron phosphate (LMFP) has been a promising cathode for Li-ion batteries (LIB) owing to its superior safety performance and low cost, yet the intrinsic low ionic/electronic conductivities result in large electrochemical polarization and inferior rate performance. Herein, we report a LMFP with high-power Li-storage capability through a Na/Co co-doped strategy. The Na⁺ with a larger ionic radius (1.02 Å) locates at Li-sites, effectively widening the Li⁺ diffusion channel to improve the Li-ion transfer dynamic. The Co²⁺ located at transition metal sites (TM-sites) can lower the band gap to improve the electronic conductivity, while it can also alleviate the increase in the b-axis parameter to shorten the Li⁺ transfer path. Accordingly, the concurrently improved ionic/electronic transfer rate endows the superior rate performance of LMFP, with a high reversible capacity of 113.5 mAh g⁻¹ at 5 C, much higher than the pristine sample (only 79.5 mAh g⁻¹). The modified LMFP also displays excellent cycling stability, maintaining 97.1% of its initial capacity after 1000 cycles at 1 C.