Roll-to-roll double side electrode processing for the development of pre-lithiated 80 F lithium-ion capacitor prototypes

Abstract Lithium-ion capacitors (LICs) show promise to help lithium-ion batteries (LIBs) and electrical double layer capacitors (EDLCs) in giving response to those applications that require an energy storage solution. However, pre-lithiation is a major challenge that needs to be tackled in order to develop efficient and long-lasting LIBs and LICs. In this work, we report for the first time the scale-up and utilization of sacrificial salts (dilithium squarate, Li₂C₄O₄) as a pre-lithiation strategy in a LIC prototype fabricated in a pilot line. The synthesis of the sacrificial salt is scaled-up to produce 1 kg and is later incorporated in the positive electrode during the slurry formulation. After in-depth process optimization, 12 meter of a double side electrode are fabricated, achieving a high mass loading of 5.5 mg cm⁻² for the HC negative electrode, and 14 mg cm⁻² for the positive electrode accounting both the activated carbon and the dilithium squarate. On account of the satisfactory mechanical and electrochemical behaviour of the electrodes, multilayer pouch cell LIC prototypes are fabricated reaching 80 F each. Pre-lithiation is completed during the first ten cycles and after the required gas exhaustion, electrochemical performance of prototypes is also satisfactory. Moreover, fabricated pouch cells overcome a float test of 1600 h at 50 °C showing a capacitance retention of 84.3%. These results give clear evidence for the potential use of this strategy in real products and can foster research in the field to promote pre-lithiation by means of sacrificial salts as the final solution to the pre-lithiation step, both for LIBs and LICs.