FABRICATION AND ELECTROCHEMICAL PERFORMANCE OF LiFePO4/Ga-LLZO/Li ALL-SOLID-STATE LITHIUM BUTTON CELL

Abstract

An all-solid-state Lithium button cell with Ga-doped Li7La3Zr2O12 (Ga-LLZO) as solid electrolyte, LiFePO4-based as cathode, and Li metal as anode has been successfully fabricated and characterized. The solid electrolyte was first optimized to obtain a high total conductivity. Different compositions of Li7-3xGaxLa3Zr2O12, where x =0, 0.1, 0.2, and 0.3. Li7La3Zr2O12 (LLZO) were synthesized using solid-state reaction and were characterized for its structural, morphological, electrical conductivity properties. XRD patterns of all sintered samples showed that all of the major peaks can be indexed to a cubic-phased garnet LLZO. SEM images revealed a densified sintered samples with relative densities of about 90% for all samples. Among the different studied compositions, the Ga-doped LLZO with x = 0.1 achieved the highest total conductivity of about 2.03 x 10-4 Scm-1 at 25oC, with an activation energy of 0.31 eV. From this solid electrolyte, an all-solid-state Lithium battery, 2032 button cell, was fabricated using LiFePO4-based cathode and Lithium metal as the anode. Charging and discharging characteristics were performed at 1C, 0.5C, and 0.2C rates. The results showed a good retention of coloumbic efficiency even after 50 cycles of charge and discharge. The capacity retention is about 15-20% after 50 cycles. The best performance of the coin cell battery revealed an initial specific discharging capacity of about 140 mAh/g using C/5 rate.