Enhanced Long-Term Stability of Organic Electrode Materials by a Trap Filler Strategy

The sensitivity of organic electrode materials to water and oxygen has long been the bottleneck of their further development. The residual and penetrative water and oxygen in electrochemical cells form electron traps that trigger irreversible side reactions, which is detrimental to their long-term stability. A trap filler strategy by introducing molecules with low ionization energy in a cell, bis(pentamethylcyclopentadienyl)cobalt(II) (DMC) as an example, is demonstrated to deactivate traps spontaneously by donating electrons to traps without causing undesirable reactions with electrode materials. The electrode materials BthCz and AQCz, with lowest unoccupied molecular orbital levels above or near the electron traps (-3.6 to -3.8 eV), exhibit conspicuous stability increment of 68.6 and 26.3%, respectively, with the optimized DMC concentration of 5 × 10^-4 M in acetonitrile electrolyte.