Enhanced Structural and Electrochemical Performance of LiNi 0.5 Mn 1.5 O 4 Cathode Material by PO 4 3− /Fe 3+ Co-Doping.

Series of PO₄³⁻/Fe³⁺ co-doped samples of LiNi_0.5Mn_1.5-5/3xFe_xP_2/3xO₄ (x = 0.01, 0.02, 0.03, 0.04, 0.05) have been synthesized by the coprecipitation–hydrothermal method, along with high-temperature calcination using FeSO₄ and NaH₂PO₄ as Fe³⁺ and PO₄³⁻ sources, respectively. The effects of the PO₄³⁻/Fe³⁺ co-doping amount on the crystal structure, particle morphology and electrochemical performance of LiNi_0.5Mn_1.5O₄ are intensively studied. The results show that the PO₄³⁻/Fe³⁺ co-doping amount exerts a significant influence on the crystal structure and particle morphology, including increased crystallinity, lowered Mn³⁺ content, smaller primary particle size with decreased agglomeration and the exposure of high-energy (110) and (311) crystal surfaces in primary particles. The synergy of the above factors contributes to the obviously ameliorated electrochemical performance of the co-doped samples. The LiNi_0.5Mn_1.45Fe_0.03P_0.02O₄ sample exhibits the best cycling stability, and the LiNi_0.5Mn_1.4333Fe_0.04P_0.0267O₄ sample displays the best rate performance. The electrochemical properties of LiNi_0.5Mn_1.5-5/3xFe_xP_2/3xO₄ can be regulated by adjusting the PO₄³⁻/Fe³⁺ co-doping amount. [ABSTRACT FROM AUTHOR]