Synthesis and Electrochemical Properties of Li2TMCl4 (TM=V, Cr, Fe, Mn, Co)

Abstract

Li-rich Li2TMCl4 system (TM = V, Cr, Fe, Mn, and Co) was studied as an alternative to LiFePO4 due to its high ionic conductivity (10-5 S/cm for Li2FeCl4 at 60°C [1]), similar theoretical capacity (165 mAh/g for 1.2 Li+ out of Li2FeCl4 vs. 170 mAh/g for 1 Li+ out of LiFePO4 [2]), and higher working voltage (3.7 V for Li2FeCl4 vs. 3.4 V for LiFePO4 [1]). These cathode materials were successfully synthesized by ball milling and solid state reaction techniques, using LiCl and TMCl2as the precursors. The phase compositions were determined by X-ray diffraction and confirmed with Rietveld refinements. Swagelok devices were designed and built for electrochemically characterization. The cathode, a mixture of the active material, carbon black, and solid electrolyte, was consolidated with solid electrolyte using spark plasma sintering (SPS). The design of the devices and techniques were validated using standard materials, such as LiCoO2 and LiFePO4purpose., as well as EIS, CV, XRD, and galvanostatic cycling tests. The standard materials were also used to compare against the performance of the Li2TMCl4 cathode material system. Wang, C. & Hong, J. Electrochem. Solid-State Lett. 10, A65 (2007).Whittingham, M. S. Chem. Rev. 104, 4271–301 (2004).