Understanding doping strategies in the design of organic electrode materials for Li and Na ion batteries: an electronic structure perspective.

In this paper, we present a systematic study of the effects of p- and n-doping in small molecules on the voltage and capacity of organic electrode materials for electrochemical batteries. In particular, coronene, phenalene derivatives as well as disodium terephthalate and related fused ring derivatives, representing often used building blocks in organic electrode materials, are chosen as model systems. We show that p-doping can drastically increase the binding strength to Li or Na and is therefore an effective strategy to design organic electrode materials for both lithium and sodium ion batteries. It could also be used to increase the theoretical capacity. On the other hand, n-doping generally has a much smaller effect on the voltage. The effects of n- and p-doping are rationalized based on the analysis of changes they induce in the band structure as well as in the molecular structure.