Organic batteries

Polymers bearing redox-active groups can be successfully utilized as active electrode material in organic batteries. The resulting battery materials can compete with inorganic battery materials, in particular in terms of theoretical capacity, power and energy density. Moreover, beneficial features of organic compounds like lightweight, flexibility, and printability make them promising candidates as active electrode materials for the next generation of secondary batteries. The richness of the organic chemistry provides a large variety of redox-active structures that can be utilized as active material in organic batteries. In particular quinones and their derivates are very promising candidates because of their tunable redox potential involving two electrons accompanied with low molar mass and high electrochemical stability. However, the synthesis of polymers bearing quinone units revealed to be challenging, because of the polarity of the carbonyl moiety and the radical scavenging properties of the quinone structure, which exclude common polymerization techniques. The introduction of methyl-groups to the benzoquinone core reduces the radical scavenging properties and enables radical polymerization of the methacrylate monomer. Nevertheless, the second electrochemical reduction of these polymers is irreversible possibly due to the nucleophilic attack of the formed anion to the ester functionality, which makes them not suitable as active material in batteries. Another possibility to apply the free radical polymerization technique is the introduction of a vinyl group to an aromatic substituent of the benzoquinone core. The direct conjugation inhibits the radical quenching abilities and further stabilizes the radical formed during the polymerization reaction. Thienyl substituents were introduced to the quinone core to lower the redox potential and a vinyl group was attached at position two in a four-step procedure. Polymers obtained from this monomer exhibit in lithium salt containing electrolytes a two-staged redox behavior displayed as one broad redox wave. Prototype lithium organic batteries with this material exhibit a capacity of 217 mAh/g at an average discharge cell potential of 2.2 V and a high rate performance with up to 10C without significant capacity decrease (complete charge or discharge within 6 min). However, the redox reaction is not side reaction-free and the capacity fades upon charge/discharge cycling