Hybrid Polymer Electrolytes for Lithium Metal Batteries

Abstract

The use of lithium (Li) metal as anode in rechargeable batteries has been revived recently because Li metal has the potential to double the specific energy density of the state-of-the-art Li ion batteries. However, Li dendrite growth and low Coulombic efficiency still hinder the application of Li metal batteries. The urgent and most important thing is to develop an electrolyte which can enable Li metal to be used as anode with high safety and good stability. Solid polymer electrolytes (SPEs) have attracted much attention due to their outstanding advantages over conventional liquid electrolytes, including no leakage of electrolytes, good flexibility, low flammability, high safety and stable contact with the electrodes. As the most widely studied polymer in SPEs, polyethylene oxide (PEO) still faces some challenges, including the low ionic conductivity (σ < 10-5 S cm-1) at room temperature (RT) and instability when charged to above 4 V vs. Li/Li+. In this work, we developed a hybrid polymer electrolyte (HPE) which exhibits high oxidation voltage and high ionic conductivity. The HPE shows an oxidation stability above 4.5 V vs. Li/Li+ when platinum was used as the working electrode in a three-electrode cell. The pure HPE has an ionic conductivity of 0.46 mS cm-1 and 2.8 mS cm-1 at 30 °C and 60 °C, respectively. The increased electrochemical window and the high conductivity of the HPE enable the Li||LiNi1/3Mn1/3Co1/3O2 cells (with an areal capacity loading of 2 mAh cm-2) to show a stable cycling in the voltage range of 3.0 – 4.2 V, having a high capacity retention of 84.2% after 170 cycles under charge rate of C/5 and discharge rate of C/3 at 60 °C. More details will be reported during the presentation at the meeting. Acknowledgement This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, the Advanced Battery Materials Research (BMR) Program of the U.S. Department of Energy (DOE) under contract no. DE-AC02-05CH11231.