Enabling fluorine-free lithium-ion capacitors and lithium-ion batteries for high-temperature applications by the implementation of lithium bis(oxalato)borate and ethyl isopropyl sulfone as electrolyte

A novel fluorine-free electrolyte comprising a solution of lithium bis(oxalato)borate in ethyl isopropyl sulfone is presented. It is characterized by its safety and non-toxic properties, along with the capability to effectively suppress the anodic dissolution of aluminum. Successful high-temperature application of this electrolyte in combination with various capacitor- and battery-like electrode materials is shown. Further utilization in a lithium-ion capacitor and a lithium-ion battery is demonstrated. To the best of the knowledge, the lithium-ion capacitor presented in this work represents the first entirely fluorine-free device suitable for high-temperature applications. When operating at 60 °C, this device delivers a maximum energy output of 169 Wh kg−1 AM at a power of 200 W kg−1 AM and even 80 Wh kg1 AM at 10 kW kg-1 AM, along with the ability to retain 80% of its initial capacitance after 3500 cycles at 5 A g−1. As such, this novel electrolyte is a promising alternative to conventional fluorine-containing configurations since its performance is capable to match or even surpass that of most similar laboratory-scale LICs