A difunctional electrolyte boosting the electrochemical performance of the primary Li/CFx batteries

Abstract

Lithium/carbon fluorides (Li/CFx) batteries have received widespread attention because of the advantages of high energy density, low environmental pollution, and low self-discharge. However, less attention has been paid to electrolytes which also significantly affect the electrochemical performance of Li/CFx batteries. Herein, we develop a novel electrolyte for Li/CFx batteries, a mixture of lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluoro(oxalate) borate (LiODFB) with different ratios dissolving in propylene carbonate (PC)/methyl butyrate (MB). Interestingly, the LiODFB not only boosts the specific capacity exceeding the theoretical value (865 mAh−1) by introducing extra capacity via its ring opening reaction with Li+ during the discharge process, but also enhances the discharge voltage and rate capability at varying temperature. As expected, the Li/CFx batteries with electrolyte of 1 M LiODFB in PC/MB delivers an ultrahigh specific capacity of 1169.84 mAh g−1 and energy density of 2646.93 Wh kg−1 at 30 °C and 10 mA g−1, and 966.9 mAh g−1 and 2232.8 Wh kg−1 at 70 ℃ and 500 mA g−1, respectively. These findings provide new ideas on designing Li/CFx batteries with high capacity and high energy density.