In the recent years, olivine LiFePO4 has been considered as a prospective cathode material for lithium-ion batteries. However, low conductivity is an obstacle to the commercialization of LiFePO4; doping the transition metal such as Mn and Ni is one of the solutions for this issue. This work aimed to synthesize the Mn-doped olivines LiMnxFe1−xPO4 at low content of Mn (x = 0.1, 0.2) via the hydrothermal route followed by pyrolyzed carbon coating. The synthesized olivines were well crystallized in olivine structure, with larger lattice parameters compared with LiFePO4. The EXD and TGA results confirmed the coated carbon of 4.14% for LiMn0.1Fe0.9PO4 and 6.86% for LiMn0.2Fe0.8PO4. Both of Mn-doped olivines showed higher diffusion coefficients of Li+ intercalation than those of LiFePO4 that led a good performance in the cycling test. LiMn0.2Fe0.8PO4 exhibited a higher specific capacity (160 mAh/g) than LiMn0.1Fe0.9PO4 (155 mAh/g), and the Mn content is beneficial for the cycling performance as well as ionic conductivity.
In 21th century, rechargeable batteries are main key of modern technology in many applications from portable devices (smartphone, laptop) to large-scale (hydride electric vehicle-HEV, smart grid system). Among the rechargeable batteries, Li-ion battery (LIB) is outstanding member due to the highest gravimetric as well as volumetric capacity; and Sodium-ion batteries (SIBs) can have contribution to alternating LIBs in large-scale application. Li-ion and Na-ion batteries have the same configuration with an insertion/extraction reversible of Li+ ions and Na+ ions into electrode positive and negative during charge-discharge process. This work aimed to investigate Na-immigration into olivine LiFePO4. The olivine phase LiFePO4 was prepared by hydrothermal process. The synthesized LiFePO4 was characterized the structure, morphology and electrochemical properties. The XRD pattern showed the high crystalline and, the Rietveld refinement with X2 = 2.32% confirmed the highly pure olivine phase without impurity. The SEM images exhibited the uniform and good distribution of synthesized olivine in submicrometric scale. The delithiated phase FePO4 was prepared by electrochemical oxidation at low rate C/20. The charge-discharge curves demonstrated the reversible Na-immigration into olivine host with a highest capacity of 80 mAh/g, the cyclability was found out in 73 mAh/g upon 30 cycles. The ex-situ XRD (electrode after electrochemical oxidation, electrode after Na-insertion) revealed the stability of FePO4 framework during Na-immigration.
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