Effects of neodymium aliovalent substitution on the structure and electrochemical performance of LiFePO4

LiFe1−xNdxPO4/C (x = 0–0.08) cathode material was synthesized using a solid-state reaction. The synthesis conditions were optimized by thermal analysis of the precursor and magnetic properties of LiFePO4/C. The structure and electrochemical performances of the material were studied using XRD, FE-SEM, EDS, electrochemical impedance spectroscopy and galvanostatic charge–discharge. The results show that a small amount of aliovalent Nd3+ ion-dopant substitution on Fe2+ ions can effectively reduce the particle size of LiFePO4/C. Cell parameters of LiFe1−xNdxPO4 (x = 0.04–0.08) were calculated, and the results showed that LiFe1−xNdxPO4/C had the same olivine structure as LiFePO4. LiFe0.4Nd0.6PO4/C delivers the discharge capacity of 165.2 mAh g−1 at rate of 0.2 C and the capacity retention rate is 92.8% after 100 cycles. Charge-transfer resistance decreases with the addition of glucose and Nd3+ ions. Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) was synthesized and PZS nanorods were used as a carbon source to coat LiFePO4. All of the results show that aliovalent doping substitution of Fe in LiFePO4 is well tolerated.