Investigation of Tailored Carbons on the Solubility of Poly(3-vinyl-N-methylphenothiazine)-Based Electrodes for Organic Batteries

Summary:

Nowadays, the state-of-the-art batteries, which are most commonly used in everyday devices, are based on lithium-ions. Due to many advantages of transition metal oxides, e.g. LiCo1/3Mn1/3Ni1/3O2, they are mainly utilized as active material in this type of battery application, however, they also suffer from significant drawbacks. These include the extraction of the transition metals with negative environmental and human impacts due to toxicity and lack of sustainability. [1] Organic materials are increasingly mentioned as an alternative for transition metal oxides as active material in batteries. They avoid the drawbacks of environmental damage and toxicity by using renewable resources. [2]
Since single small organic, redox-active molecules dissolve in most common battery electrolytes, these molecules are more often incorporated as a side group or into the backbone of a polymer. The resulting redox-active polymers are very promising active materials for battery application, and numerous p-type materials for dual-ion batteries have been reported in literature. During charging, the redox-active groups in the p-type polymer are oxidized and therefore the material is used as positive electrode against other organic active materials or lithium metal as negative electrode. For charge balancing of the oxidized redox-active group, anions from the electrolyte are required. [3]
In previous studies the redox-active polymer poly(3-vinyl-N-methylphenothiazine) (PVMPT) has been extensively studied. The material exhibits very good cycling stability due to the formation of π-interactions between the oxidized redox-active group MPT, but is well soluble in many standard electrolytes. [4]
In this work, we present the influence of tailored porous carbons as conductive additive in composite electrodes based on the polymer PVMPT on the cell performance. The carbons were expected to reduce the dissolution of the polymer in the electrolyte as a result of the penetration of PVMPT into the porous structure of the carbon with variable pores sizes. The effect of average pore size on penetration and thus on dissolution and battery performance will be highlighted.

[1] Banza C. et al., Nat. Sustain. 2018, 1, 495.
[2] Bhosale M. E. et al., J. Mater. Chem. A 2018, 6, 19885.
[3] Muench S. et al., Chemical reviews 2016, 116, 9438.
[4] Kolek M. et al., Chem. Mater. 2018, 30, 6307.