About Microwave Solvothermal Synthesis of Solid Solutions LiFe_xMn_(1-x)PO_4/C and Their Electrochemical Properties

摘要

Microwave solvothermal synthesis is used to obtain solid solutions of LiFe_xMn_(1-x)PO_4 (with x=0, 0.1, 0.2, ..., 1.0). To improve ionic and electronic conductivity, the samples are coated with a conductive layer. To investigate the effect of the formation of a solid solution, LiFe_(0.5)Mn_(0.5)PO_4, produced by microwave irradiation, is compared to different mechanical preparation methods of equimolar mixtures between LiFePO_4 and LiMnPO_4. All powders are analyzed regarding to their structural-chemical and electrochemical properties. Slope cuts of prepared electrodes for LiFe_(0.5)Mn_(0.5)PO_4/C are further characterized by back scattered electron imaging and EDX analysis. The highest capacity of 139mAh g~(-1) at 0.1C is achieved for the microwave-synthesized LiFe_(0.5)Mn_(0.5)PO_4/C (sample F). The iron substitution by manganese leads to altered X-ray diffraction patterns and influences the oxidation and reduction potential position of Fe~(2+)/Fe~(3+) and Mn~(2+)/Mn~(3+). Further, we found out that the preparation method is crucial in terms of solid solution formation between iron and manganese.