Pencil Powered Faradaic Electrode for Lithium-Ion Capacitors with High Energy and Wide Temperature Operation

Lithium-ion capacitors (LICs) are considered next-generation energy storage devices that combine the goodness of both Li-ion batteries and electric double-layer capacitors. In this work, LIC is assembled with electrochemically pre-lithiated (LiC6) pencil graphite (PG, 1B&4H grades) as anode and activated carbon (AC) as the cathode. PG grades, naturally available graphite silica composite materials, are characterized, and the electrochemical performance is studied in half-cell assembly for 14 grades. PG grades in the middle of the hardness scale demonstrated better electrochemical activity than the end compositions, representing the involvement of graphite and silica's role in overall performance. However, it is observed that SiO2/clay component in PG material is to provide only mechanical support to the system considering the inactiveness of SiO2 towards Li storage. The assembled LICs (AC/PG 1B LIC) & (AC/PG 4B LIC) delivered maximum energy density of similar to 172 & similar to 162 Wh kg(-1), respectively, with long-term stability under balanced mass loading conditions. Besides ambient temperature, the LICs exhibited stable performance at low (-5 and 10 degrees C) and high-temperature (50 degrees C) conditions. The outstanding electrochemical performance of PG material in LIC assembly indicates the choice of pencil's aptness in energy storage devices.