Anthraquinone Oligomers as Anode-Active Material in Rechargeable Nickel/Oligomer Batteries with Aqueous Electrolyte

This work is an initial investigation of the possible use of redox-active anthraquinone as anode material in combination with Ni­(OH)2 in a secondary battery with aqueous KOH electrolyte. Three different anode materials are investigated: an anthraquinone monomer and two different anthraquinone based oligomers. All batteries are rechargeable, and almost 100% of the theoretical capacity can be accessed in the first cycle, after which significant capacity loss occurs. The capacity loss is attributed mainly to swelling of the electrodes and solubility of anthraquinones in their charged (reduced) state because reduced anthraquinone is deprotonated and ionized in alkaline solutions. Nonetheless, batteries based on one of the oligomerized anthraquinones (oligo­[benzene-1,4-dithiol-alt-(1,5- dichloroanthraquinone)] anode) show the best performance and retain almost 50% of the discharge capacity after 100 cycles. The better performance is attributed to the reduced solubility caused by the oligomerization. It is anticipated that measures to decrease the solubility further could lead to much improved capacity retention.