Microwave assisted synthesis, characterization and electrochemical performance of LiVPO4F cathode material

Abstract

High-voltage cathode material, lithium vanadium fluorophosphate LiVPO4F, has been for the first time synthesized by a rapid two-step method based on microwave-assisted carbothermal reduction (CTR) and characterized with the use of scanning electron microscopy (SEM), X-ray diffraction and DTA/TG thermal analysis. Its electrochemical performance has been examined by galvanostatic charge-discharge cycling. Calculated lattice parameters of the obtained LiVPO4F compound were in accordance with literature. Its thermal stability up to 550 °C was confirmed. Charge-discharge cycling of LiVPO4F in the voltage range between 3.0 V and 4.4 V at a current rate of 7.75 mA⋅g−1 (C/20) after 5 cycles showed a charge capacity of 90 mA⋅h⋅g−1 and a discharge capacity of 58 mA⋅h⋅g−1. For a current rate of 15.5 mA⋅g−1 (C/10) after 10 cycles charge capacity achieved the value of 60 mA⋅h⋅g−1 whereas the discharge capacity was of 52 mA⋅h⋅g−1. The discharge plateau was at 4.18 V. The presented results suggest that LiVPO4F cathode material can be synthesized by the simplified two-step microwave-assisted reduction method. Although it needs to be further optimized, the method is simpler, faster and cheaper as compared to other preparation routes.