Ca- and Mg-based batteries represent a more sustainable
alternative
to Li-ion batteries. However, multivalent cation technologies suffer
from poor cation mass transport. In addition, the development of positive
electrodes enabling reversible charge storage currently represents
one of the major challenges. Organic positive electrodes, in addition
to being the most sustainable and potentially low-cost candidates,
compared with their inorganic counterparts, currently present the
best electrochemical performances in Ca and Mg cells. Unfortunately,
organic positive electrodes suffer from relatively low capacity retention
upon cycling, the origin of which is not yet fully understood. Here,
1,4,5,8-naphthalenetetracarboxylic dianhydride-derived polyimide was
tested in Li, Na, Mg, and Ca cells for the sake of comparison in terms
of redox potential, gravimetric capacities, capacity retention, and
rate capability. The redox mechanisms were also investigated by means
of operando IR experiments, and a parameter affecting most figures
of merit has been identified: the presence of contact ion-pairs in
the electrolyte.