Supercapacitors are high power energy storage devices capable of sustaining millions of charge/discharge cycles. The development of hybrid capacitors such as lithium-ion capacitors (LICs), in which the negative activated carbon electrode is replaced by a lithium intercalated compound, led to capacitors requiring less active material, wider cell voltages, and greater recyclability. However, since the positive electrode of LICs is not a lithium-ion source, prelithiation of the negative electrode is difficult.

T. Brousse, Université de Nantes, France, and colleagues Have developed a strategy to prelithiate the negative electrode of LICs using a 3,4-dihydroxybenzonitrile dilithium salt (Li₂DHBN). The lithium enolate can be added to the active carbon of the electrode and irreversibly oxidized to the ortho-quinone species when a potential is applied. Upon oxidation, lithium is extracted and the oxidized species dissolves in the electrolyte yielding a cell that operates as a LIC.

The researches demonstrated that the LICs fabricated by prelithiation with Li₂DHBN maintained a high energy density (40–60 Wh kg^–1 per total mass of electrode material) and sustained long-term cycling. Further, no auxiliary lithium electrode is needed favouring a much safer electrochemical system. The method presented offers a pathway for a greener hybrid capacitor.

• Safe and recyclable lithium-ion capacitors using sacrificial organic lithium salt,
  P. Jeżowski, O. Crosnier, E. Deunf, P. Poizot, F. Béguin, T. Brousse,
  Nature Mater. 2017.
  https://doi.org/10.1038/nmat5029