Simultaneously pre-alloying and artificial solid electrolyte interface towards highly stable aluminum anode for high-performance Li hybrid capacitor

Anode materials such as aluminum (Al) are promising candidates for Li-based energy storage devices, while they suffer from huge volume change when lithiated. The large volume expansion leads to: (1) electrode pulverization, which results in the loss of active materials and the formation of dead Li; (2) iterative destruction/formation of solid electrolyte interface (SEI), which continuously consumes the electrolyte and meanwhile increases the battery impedance. Herein, we introduce a strategy of combining the pre-alloying and artificial SEI together to enhance the cycling stability of Al anode. After investigating the matching behaviors of several additives with different anodes, a pre-alloyed LiAl alloy and a LiF-rich artificial SEI are simultaneously constructed on the Al anode by pre-alloying with lithium difluoro(oxalato)borate (LiDFOB) additive, which are beneficial to compensate for the irreversible consumption of Li+ ions and maintain the structural stability of SEI. Consequently, a novel Li hybrid capacitor (LHC) combining this pre-alloyed Al anode and environmental friendly and low-cost activated carbon (AC) cathode is established in the voltage range of 1.5–4.5 ​V, which exhibits a specific capacity of 123.6 ​mAh g-1 with a capacity retention of 85.6% after 2000 cycles.