Site-dependent electrochemical performance of Mg doped LiFePO4

• Two types of Mg-doped LiFePO4 samples were prepared via a two-step approach.
• The Mg-doped LiFePO4 samples have different Mg dwelling sites.
• Their electrochemical activity is highly site-dependent on Mg dopant.
• Fe-site doping is more efficient than Li-site in the LiFePO4.

Exotic metal (EM) doping in LiFePO4 materials could mitigate their poor electronic conductivity and electrochemical performance. This effect is believed to be dependent on the EM dwelling site, which has yet been well clarified due to experimental difficulty. Herein, we report on Mg-doped LiFePO4 samples with dopant in two distinct sites, namely the Li1 − 2xMgxFePO4 and LiFe1 − xMgxPO4, using a specially designed two-step reaction. The conductivity and electrochemical test results are a clear indication that the performance of the doped LiFePO4 samples is highly Mg site dependent, consistent with theoretical analysis.