Pre‐Lithiation Strategies for Lithium Ion Capacitors: Past, Present, and Future

Abstract Lithium ion capacitor (LIC) is an emerging technology that holds promise to bridge the energy‐to‐power gap between already market stablished lithium ion battery and electrochemical double‐layer capacitor technologies. Academic research is mainly focused on increasing energy, power and cycle life metrics, but next, pre‐lithiation strategy is the key that will open the final door, or not, towards industrialization and commercialization of the technology. Its relevance has only recently been thoroughly considered, but several strategies, all with their own particular set of assets, are already available within the state‐of‐the‐art. It is the right moment to make a retrospective review analysis of the pros and cons of each of the strategies, in order to draw the correct conclusions and look into the future with the best perspective. Despite some reviews newly considered the topic, they were all done in a broader framework, what finally waters down the importance of this critical step. Thus, this review aims to solely focus on the pre‐lithiation strategies that have been reported so far for LICs, from the first academic auxiliary lithium metal approach to the latest novel strategies. To conclude, challenges and requierements that the ideal pre‐lithiation strategy should fulfil in order to foster market uptake of LIC technology are also discussed.