Charge-transfer complexes for high-power organic rechargeable batteries

Organic redox compounds are potential substitutes for transition-metal-oxide electrode materials in rechargeable batteries because of their low cost, minimal environmental footprint, and chemical diversity. However, their inherently low electrical conductivity and high solubility in organic solvents are serious impediments to achieving performance comparable to that of currently used inorganic-based electrode materials. Herein, we report organic charge-transfer complexes as a novel class of electrode materials with intrinsically high electrical conductivity and low solubility that can potentially overcome the chronic drawbacks associated with organic electrodes. The formation of the charge-transfer complexes, phenazine–7,7,8,8-tetracyanoquinodimethane and dibenzo-1,4-dioxin–7,7,8,8-tetracyanoquinodimethane, via a room-temperature process leads to enhancement in the electrical conductivity and reduction in the dissolution resulting in the high power and cycle performances that far outperform those of each single-moiety counterpart. This finding demonstrates the general applicability of the charge-transfer complex to simultaneously improve the electrical conductivity and mitigate the shortcomings of existing single-moiety-based organic electrode materials, and opens up an uncharted pathway toward the development of high-performance organic electrode materials via the exploration of various combinations of donor–acceptor monomers with different stoichiometry.