Electrode design, using biological components to mimic mother-of-pearl, could be crucial to structural batteries for cars and aircraft
One of the biggest remaining problems facing electric vehicles – whether they are road-going, waterborne or flying – is weight. Vehicles must carry their energy storage, and in the case of electric vehicles this inevitably means batteries.
No matter how many advances electrical engineers make in improving energy density, batteries remain dense and heavy components, and this is a drag on vehicle performance.
One approach to reducing the weight of electric vehicles might be to incorporate energy storage into the structure of the vehicle itself, thereby distributing the mass all over the vehicle and reducing the need for a single large battery or even eliminating it altogether.
The stumbling block to this approach is that materials that are good for energy storage and release tend to have properties that are not useful for structural applications: they are often brittle, which has obvious safety implications.
A team led by a Texas A&M University chemical engineer, Jodie Lutkenhaus, now claims to have made progress towards solving this problem using an approach inspired by brain chemistry and a trick employed by shellfish to stick themselves to rocks.
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In a paper in the journal Matter, Lutkenhaus and her colleagues explain how their studies of redox active polymers for energy storage led them to investigate the properties of dopamine, most familiar as a signal-carrying molecule in the brain involved in movement, but also a very sticky substance that mimics proteins found in the material that mussels use to fasten themselves tightly to any surface underwater.
The team used dopamine to functionalise – that is, chemically bond to – graphene oxide, and then combine this material into a composite with aramid fibres, better known as Kevlar. This composite is both strong and tough, with a structure and properties similar to the famously tough natural material nacre or mother-of-pearl, and the graphene in its structure conveys both lightness and electrical properties that make it useful as an electrode.
The researchers describe using this material to form the electrodes for a super capacitor, a kind of energy storage device which can be charged and discharged very quickly.
The paper reports the highest ever multifunctional efficiency (a metric which evaluates material based on both its mechanical and electrochemical performance) for graphene-based materials.