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Commercialized lithium iron phosphate (LiFePO4) batteries have become mainstream energy storage batteries due to their incomparable advantages in safety, stability, and low cost. However, LiFePO4 (LFP) batteries still have the problems of capacity decline, poor low-temperature performance, etc. The problems are mainly caused by the following reasons: (1) the irreversible phase transition of LiFePO4; (2) the formation of the cathode–electrolyte interface (CEI) layer; (3) the dissolution of the iron elements; (4) the oxidative decomposition of the electrolyte; (5) the repeated growth and thickening of the solid–electrolyte interface (SEI) film on the anode electrode; (6) the structural deterioration of graphite anodes; (7) the growth of lithium dendrites. In order to eliminate the problems, methods such as the modification, doping, and coating of cathode materials, electrolyte design, and anode coating have been studied to effectively improve the electrochemical performance of LFP batteries. This review briefly describes the working principle of the LFP battery, the crystal structure of the LFP cathode material, and its electrochemical performance as a cathode. The performance degradation mechanism of LFP batteries is summarized in three aspects—cathode material, anode material, and electrolyte—and the research status of LFP material modification and electrolyte design is emphatically discussed. Finally, the challenges and future development of LFP batteries are prospected. [ABSTRACT FROM AUTHOR]

Li 1.1Mn 2 − 2xCo xNi xO 4 ( x = 0, 0.075) spinel powders were successfully synthesized using a liquid stirred tank reactor method. The electrochemical performances of the undoped and doped spinels at 4.3 and 5 V were investigated by X-ray diffraction, field-emission scanning electron microscopy, and electrochemical impedance spectroscopy. The capacity of Li 1.1Mn 2 − 2xCo xNi xO 4 could be divided into two parts, with 4.3 V as the dividing line in the 3–5 V charge–discharge range. Low capacity and good cyclic performance were obtained when cycled in the 3–4.3 V range for the multi-doped Li 1.1Mn 2 − 2xCo xNi xO 4 spinel. In comparison with multi-doped spinel at 4.3 V, the results of the cyclic performance worsened at 5 V because the structure underwent further shrinkage, the charge transfer resistance rose and the electrolyte decomposed. [ABSTRACT FROM AUTHOR]

Abstract: The LiNi0.5−x Cu x Mn1.5−y Al y O4 (x = 0, 0.05, y = 0, 0.05) powders are synthesized by liquid co-precipitation and wet-milling. The doping effect on LiNi0.5Mn1.5O4 by Al3+, Cu2+, and Al3+/Cu2+ co-doping are investigated and compared in relation to physical and electrochemical characterization, namely, through X-ray diffraction, scanning electron microscopy, electronic conductivity, cyclic voltammetry and cycle tests. Results suggest that both Al3+ and Cu2+ doping effectively improve electrochemical performance of LiNi0.5Mn1.5O4, although the effect is different between the two cations. All doped samples exceed 95% capacity retention after 100 cycles at room temperature compared to 92% retention for the undoped sample. Moreover, co-doped LiNi0.45Cu0.05Mn1.45Al0.05O4 exhibits the best cyclic performance with slight superiority. [Copyright &y& Elsevier]