Enabling versatile, custom-made lithium-ion capacitor prototypes: Benefits and drawbacks of using hard carbon instead of graphite

In this work, the benefits and drawbacks of replacing graphite by hard carbon as negative electrode in a lithium -ion capacitor are studied. Beyond the material selection and electrode optimization, the impact of the cell design in the final performance is also evaluated. When selecting hard carbon, final prototype avoids using any critical raw material, since a sacrificial salt (dilithium squarate) has been also used as a pre-lithiation strategy, instead of the most preferred industrial metallic lithium-based solution. The combination of these two strategies shows unique features, enabling the development of a highly sustainable, easy-to-recycle, eco-friendly energy storage solution, towards a more realistic approach. Likewise, this solution offers high versatility and degree of freedom to tune the mass loading, mass balance and operating voltage, enabling custom-made prototypes, offering a large portfolio of products, owing to the electrochemical characteristics of hard carbon. Prototype's internal compo-nents design determines final cell performance, which it is directly related to the equilibrium between the most relevant metrics, i.e., energy, power and cyclability. Thus, smart ad-hoc designs can be developed to cover a wide range of applications and specific needs of different market niches. Full performance analysis for different-in -design monolayer pouch cells that can operate beyond 4.0 V is reported in this work.