We are putting a lot of efforts on greener and sustainable organic non-aqueous and aqueous batteries at the IMN. In this communication, we report on novel crystallized organic positive electrode materials for the non-aqueous application of organic batteries. However the synthesis of high-voltage lithiated materials is rather challenging, so very few examples of all-organic Li-ion cells currently exist.
Compounds of the Mn+2/n-p-DHT (with Mn+ = Li+, Mg2+, Ca2+ and Ba2+) family were studied to better understand the effect of substitution chemistry on the redox properties of the Li-diphenolate cycle of p-DHT. This innovative chemical approach makes it possible to tune the redox potential of lithiated organic electrode materials, by playing on the nature and the ionic potential of a spectator cation in the host structure. Indeed, by adjusting the attractor/donor electron effects in the organic redox-active backbone, it is possible to modify the redox potential of the molecule by inductive effect.
We show that substituting magnesium (2,5-dilithium-oxy)-terephthalate for lithium (2,5-dilithium-oxy)-terephthalate enables an outstanding voltage gain of 800 mV, leading to a high operating voltage of 3.4V vs. Li+/Li [2]. This Mg(Li2)-p-DHT compound is the first lithiated organic positive electrode material with an operating potential as high as that of LiFePO4. Based on this finding, full organic Li-ion cells with an output voltage of 2.5V and long cycle life have been achieved, thus making a big step forward the design of high energy green and sustainable organic batteries.
References
[1] P. Poizot, F. Dolhem, Energy Environ. Sci. 4, 2003 (2011).
[2] A. Jouhara, N. Dupré, A.C. Gaillot, D. Guyomard, F. Dolhem, P. Poizot, Nature Commun., 9, 4401 (2018).