LiNO3 and TMP enabled high voltage room-temperature solid-state lithium metal battery

Abstract

The poor interfacial contact and notorious instability issues between solid electrolyte and electrodes seriously handicap the practical applications of solid-state lithium metal batteries (LMBs). In-situ polymerization is a considerable choice to upgrade the interfacial transport properties by directly curing the liquid precursor inside the cell. Herein, a ∼ 17 μm poly(ethylene glycol) methyl ether methacrylate (PEGMEA) based solid polymer electrolyte (SPE) is prepared by this method. Trimethyl phosphate (TMP) and LiNO3 are introduced to promote the ion transport as well as enhance the electrodes/electrolyte interfacial stability. Interestingly, although LiNO3 increases the electrolyte’s glass transition temperature thus hinders the anion transport, while higher Li+ conductivity is obtained due to the weakened interaction between Li+ and its ligands, ethylene oxide (EO) and TMP. The optimal electrolyte (PTLiN1) shows an acceptable ionic conductivity of 1.2 × 10-4 S cm−1 at 55°C and lithium ion transference number (tLi+) of 0.46, which enables the Li||Li symmetric cells to run stability within 1500 h (0.2 mA cm−2, 0.4 mAh cm−2) at 55°C and 1000 h (0.1 mA cm−2, 0.2 mAh cm−2) at 25°C. Meanwhile, the LiFePO4||Li cell with PTLiN1 shows superior long cycle lifetime with a high capacity retention of 88.4% over 300 cycles at 0.5 C. The cells coupled with LiCoO2 can even work stably under room temperature in the voltage range of 3.0 ∼ 4.3 V. Pouch cells based on PTLiN1 are also prepared and show outstanding flexibility and high security, which provides new idea for the development of economical and convenient solid-state batteries.