Revealing the Ultrahigh Rate Performance of the La and Ce Co-doping LiFePO₄Composite

LiFePO₄with ultrahigh rate ability and enhanced electronic/ionic conductivity can be achieved by element doping. However, the role of substitution on the electronic/ionic conductivity and size effect on the electrochemical performance are still open. Here, LiFePO₄particles (LC-LFP) with tuned sizes are synthesized via La and Ce co-doping, delivering a capacity of 91.9 mAh g^-1under 200 C. In addition, LC-LFP exhibit a power density as high as 57.6 kW kg^-1when the energy density is nearly 300 Wh kg^-1owing to the 10⁵enhancement of inherent conductivity and 10⁵Li⁺diffusion ability. DFT results suggest that La and Ce co-doping would not only facilitate free Li⁺ions to extrude out of the unit cell due to the structure distortion but also generate extra middle-gap states to boost the carrier concentration. Furthermore, it appears that atoms on the surface of the particles tend to decrease the band gap and lower the conduction band compared to the atoms in the bulk. This work demonstrates and discloses a promising strategy to enhance the rate performance of LiFePO₄by element co-doping.