Azole derived deep eutectic electrolyte for high performance lithium metal-free full batteries

Abstract

Electrolytes are considered the lifeblood of lithium batteries, facilitating ion transfer between the cathode and anode. However, the flammability, volatility and corrosiveness of organic electrolytes impede the sustainable development of lithium batteries. Deep eutectic electrolytes (DEEs) have emerged as a promising alternative, exhibiting high stability, non-flammability and wide electrochemical window. Herein, a series of DEEs with varying molar ratios of azoles and LiTFSI were facilely prepared through the interaction of Li⋯N. These DEEs demonstrate unique advantages, including non-flammability, high conductivity and a favourable Li+ transference number. In particular, the DEEs ImL-4:1 and PyL-4:1 (Imidazole:LiTFSI = 4:1 and Pyrazole:LiTFSI = 4:1, respectively) achieve high ionic conductivities of 4.5 × 10−3 and 5.8 × 10−3 S cm−1 at 80 °C, respectively. Notably, the electrochemical window of PyL-4:1 is stable, making it a suitable electrolyte for the lithium metal-free Li4Ti5O12/LiFePO4 full battery. This system exhibits an initial specific capacity of 147 mAh g−1 and maintains stable cycling performance over 200 cycles. This study offers valuable insights into the design of electrolytes, addressing the challenges posed by traditional organic electrolytes and paving the way for sustainable lithium battery development.