Effect of the iron doping in LiCoPO4 cathode materials for lithium cells

• Undoped and iron-doped lithium cobalt phosphate olivines are synthesized by a low temperature solvothermal route
• Iron doping induces large alteration in the morphology and stoichiometry of the material
• Iron doping enhance the performances of LiCoPO4 in lithium cells by improving the cycling ability
• Iron-doped LiCoPO4 material annelaed under Ar shows superior performances in lithium cells.

LiCoPO4 (LCP) is a promising candidate as alternative cathode for high-voltage lithium-ion batteries. However, its practical electrochemical performances are still far from the theoretical data likely due to the low electronic and ionic conductivities. Moreover LCP typically suffers a rapid capacity fading upon cycling, probably due to structural degradations and electrolyte decomposition at 5 V vs. Li+/Li. Previous studies showed that carbon coating and metal doping may improve LCP electrochemical properties. In this work we report: (a) the fine tuning of a novel synthetic route at low temperature to obtain micrometric LCP crystallites morphologically homogeneous and crystallographically pure; (b) the analysis of the effect of iron doping on LCP structural features and electrochemical properties in lithium cell; (c) the beneficial simultaneous effect of iron doping and post-synthesis high-temperature annealing on the electrochemical performances in Li cells. The optimized material shows a reversible capacity of 120 mAh g−1 at 0.1C rate and a capacity retention of 78% after 20 cycles.

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