The liquid-phase method of synthesis of lithium iron(II) phosphate (LiFePO4) in the medium of choline chloride and diethylene glycol under the action of microwave heating is proposed. With a power of microwave radiation of 920 and 1150 W, a nanocrystalline LiFePO4 without impurities was obtained. Obtained samples of microwave processes contain amorphous phase and require long annealing resulting in nanocrystalline LiFePO4/C composites with small impurities Li3PO4, Li3Fe2(PO4)3, Fe2O3. For samples obtained in the choline chloride with diethylene glycol microwave heating characteristic is lamellar morphology – the same as for LiFePO4 obtained by thermal heating, but in the case of using microwave irradiation plates are smaller. This indicates that the reaction mechanism of LiFePO4 synthesis does not change in the microwave synthesis, but the reaction rate is significantly increased (up to 6 times faster than thermal synthesis). Using the Raman spectroscopy, the nature of the carbon coating on the crystal of LiFePO4 was studied. The Raman spectra of the LiFePO4/C composites obtained from an annealed powder with glucose and malic acid have pronounced D (~ 1340 cm-1) and G (~ 1600 cm-1) peaks, as well as two additional bands at ~ 1200 and ~ 1520 cm-1 obtained after the expansion of main peaks. The ratio of peak intensities of lines D and G (ID/IG) has a value of 1.06 for the material obtained after glucose carbonation and 1.01 for LiFePO4/C composites annealed with malic acid, which correlates with the results of other investigations of the carbon coating LiFePO4 (ID/IG ~ 1-3) That means the choice of an organic precursor does not affect the nature of the carbon coating (ID/IG ~ 1). Capacity of cathode material based on LiFePO4/C composites is ~ 130 mAh/g for a current of 0.1C.
2. Grewal A. S., Kumar K., Redhu S., Bhardwaj S. Microwave assisted synthesis: a green chemistry approach. Int. Res J Pharm. App Sci. 2013. 3: 278.
3. Protsenko V.S., Bobrova L.S., Burmistrov K.S., Danilov F.I. The application of hole theory for the interpretation of data on conductivity of ionic liquids containing chromium(III) chloride, choline chloride and water additives. Voprosy Khimii i Khimicheskoi Tekhnologii. 2017. 1(110): 27. [in Ukrainian].
4. Tomе L., Baiгo V., Silva W., Brett C. Deep eutectic solvents for the production and application of new materials. Applied Materials Today. 2018. 10: 30.
5. Galaguz V., Malovanyi S., Panov E. Synthesis of LiFePO4 nanocrystals and properties of cathodic material on their basis. J. Serb. Chem. Soc. 2018. 83(10): 1123.
6. Swain P., Viji M., Mocherla P.S.V., Sudakar C. Carbon coating on the current collector and LiFePO4 nanoparticles inﬂuence of sp2 and sp3-like disordered carbon on the electrochemical properties. J. Pow. Sour. 2015. 293: 613.
7. Nagpurea S. C., B. Bhushana, S.S. Babub Raman and NMR studies of aged LiFePO4 cathode. Appl. Surf. Sci. 2012. 259: 49.
8. Zhao B., Yu X., Cai R. Solution combustion synthesis of high-rate performance carbon-coated lithium iron phosphate from inexpensive iron (III) raw material. J. Mater. Chem. 2012. 22: 2900.
9. Long Y., Shu Y., Ma X., Ye M. In-situ synthesizing superior high-rate LiFePO4/C nanorods embedded in graphene matrix. Electr. Acta 2014. 117: 105.