Biomass‐Derived Carbon Materials as Prospective Electrodes for High‐Energy Lithium‐ and Sodium‐Ion Capacitors

Biomass‐derived carbon materials have received special attention as efficient, low‐cost, active materials for charge‐storage devices, regardless of the power system, such as supercapacitors and rechargeable batteries. In this Minireview, we discuss the influence of biomass‐derived carbonaceous materials as positive or negative electrodes (or both) in high‐energy hybrid lithium‐ion configurations with an organic electrolyte. In such hybrid configurations, the electrochemical activity is completely different to conventional electrical double‐layer capacitors; that is, one of the electrodes undergoes a Faradaic reaction, whilst the counter electrode undergoes a non‐Faradaic reaction, to achieve high energy density. The use of a variety of biomass precursors with different properties, such as surface functionality, the presence of inherent heteroatoms, tailored meso‐/microporosity, high specific surface area, various degrees of crystallization, calcination temperature, and atmosphere, are described in detail. Sodium‐ion capacitors are also discussed, because they are an important alternative to lithium‐ion capacitors, owing to the low abundance and high cost of lithium. The electrochemical performance of carbonaceous electrodes in supercapacitors and rechargeable batteries are not discussed. Batteries not included: Low‐cost biomass‐derived carbon materials from different sources have become established as promising electrode materials in lithium‐ion and sodium‐ion capacitors that are expected to bridge the gap between batteries and supercapacitors. This Minireview describes the preparation of biomass‐derived carbon materials and their properties, which change their electrochemical performance in lithium‐ion and sodium‐ion capacitors.