Materials and systems for polymer-based Metallocene batteries: Status and challenges

Modern society is highly dependent on portable electronics powered by rechargeable batteries that are not only fulfilling the basic requirements such as fast charging and durability but also overcome the environmental issues of current lithium-ion batteries. Moreover, the required miniaturization of e.g. communication systems or sensors in mobile, wearable, or implantable devices needs optimization of the architecture, thus battery technologies that are entirely shape-conformable and bendable without loss in energy and current density. Organometallic battery materials offer certain characteristics such as ultrafast charging, flexibility, compatibility with organic and aqueous electrolytes, and tunable cell voltage, which make them interesting alternatives to replace conventional metals as electroactive components while taking advantage of the bifunctional characteristics of metal ions and organic frameworks. This review presents an overview of the research on the oligo/polymeric organometallic materials for anodic and cathodic battery application and discusses the contribution of auxiliary components. Particularly the often necessary addition of conductive fillers represents a serious obstacle against the development of organometallic batteries. Moreover, the disadvantage of volume change upon redox cycling in organometallic batteries is discussed.