Roll-to-roll Prelithiation of Li-ion Batteries Anodes Using Ultrathin Lithium Strips

•SEI formation reduces LIB energy density and demands anode prelithiation.•6-μm-thick Li strips prelithiation is precise and industrially compatible.•The SEI evolution throughout prelithiation and cycles is monitored and modeled.•Prelithiated pouch cell tests show lifted energy density after 1200 cycles. The irreversible formation of solid electrolyte interphase (SEI) reduces lithium-ion batteries’ capacity and energy density (LIBs), prompting the prelithiation strategies to compensate for the Li loss. However, the accuracy of the prelithiation degree and the SEI formation under prelithiation conditions remain key issues, especially for practical industrial production. Herein, we demonstrate that roll-to-roll prelithiation of graphite anodes can be done using ultrathin lithium strips (6-μm-thick), and the prelithiation degree can be precisely tuned by the topological distribution. More importantly, the formation of SEI during the prelithiation process and its influence on the long-term cycling performance of the prelithiated LiFePO4 || graphite pouch cells was revealed. Afterward, the prelithiated pouch LiFePO4 || graphite cell at the optimized conditions exhibits the upgraded energy density after even 1200 cycles. This study shall provide an industrial-scale prelithiation technique for high-energy–density LIBs and a pioneering systematic investigation of SEI chemistry during prelithiation.