Mechanoactivation-assisted synthesis and electrochemical characterization of manganese lightly doped LiFePO4

Olivine compounds LiFe1-xMnxPO4 (0.0 <= x <= 0.3) for cathodes of secondary lithium-ion batteries were synthesized via a mechanoactivation-assisted solid-state reaction. The optimal manganese content and electrochemical performance of the as-synthesized powders were investigated by XRD, EDX mapping, cyclic voltammetry, and charge-discharge characterizations. According to XRD and EDX mapping results, phase-pure compounds with olivine structure were formed after the calcination under nitrogen atmosphere at 700 degrees C for 20h. Among the various LiFe1-xMnxPO4 under test, LiFe0.8Mn0.2PO4 showed the highest electrical conductivity, which reached a value of 3.49 x 10(-5) S cm(-1) at room temperature, more than 5 orders higher than that of pristine LiEePO(4) (1.08 x 10(-10) S cm(-1)). Without the carbon coating, pristine LiFe0.8Mn0.2PO4 showed discharge capacity of similar to 123 and 100 mAh g(-1) at 0.1 and 1 C rates, respectively. It means about 91% and 74% of the Fe2+ in LiFe0.8Mn0.2PO4 is electrochemically utilizable correspondingly. For a comparison, they are only 65% and 15% for the pristine LiFePO4 prepared by a similar process. LiFe1-xMn4PO4 also showed stable cycling performance within the 50 cycles under test. It suggests manganese lightly doped LiFePO4 could be practical cathode materials for high-rate lithium-ion batteries. (c) 2009 Elsevier B.V. All rights reserved.