CuS modified graphite from spent Li-ion batteries towards building high energy Na-ion capacitors via solvent-co-intercalation process

Abstract

Sodium-ion capacitors (NICs) are one of the most modern hybrid energy storage devices, and they involve two different energy storage mechanisms (faradaic and non-faradaic). The NICs are bridging the gap between the Na-ion batteries and the capacitors with enhanced power and energy densities. This work explores a new combination electrode material, i.e., recovered graphite (RG) decorated with copper sulphide (CuS, CS) as the anode for the NIC application, in which graphite undergoes the solvent-co-intercalation process, and CuS adopts the conversion reaction. We also report the possibility of efficient direct recovery of the anode of dead/spent Li-ion batteries and upcycling as a battery-type component for NIC with commercially available activated carbon (AC) as the capacitor-type cathode. First, the Na-storage property is analyzed in the half-cell configuration, where the Na/RG-CS half-cell displayed excellent cyclic stability with a stable specific capacity of 113 mAh/g after 500 cycles with > 96 % coulombic efficiency in ether solutions. With a pre-sodiated form of RG-CS as anode and mass-balanced AC as a cathode, the NIC is fabricated. The NIC displayed a superior energy density of 64.6 Wh kg−1 with ultra-long cyclability for more than 10,000 cycles with > 85 % capacity retention. The compatibility of the NIC in different environmental conditions is also studied, and the cell renders better performance in all temperature conditions.