If the breakthrough of electromobility is to succeed, electric vehicles will have to have a longer range in the future, charging must be faster and, in addition, the price of the battery must fall significantly. The next generation battery type therefore needs to have a higher energy density and better capacity, and be made of inexpensive, safer and more environmentally friendly materials. Rechargeable batteries, which basically function according to the same technology as lithium-ion batteries, but in which lithium-ion is replaced by cheaper metal ions such as sodium, magnesium and aluminium ions, are being intensively investigated.
Organic materials are ideal for the electrodes because they usually do not contain any harmful and expensive heavy metals and can easily be adapted for different purposes. Unfortunately, they dissolve in the liquid electrolyte, making such electrodes unstable.
Chunsheng Wang and his team from the University of Maryland (USA) along with an international group of scientists have developed an organic polymer cathode that does not dissolve, but at the same time has a high capacity for rapid discharge and charging. For the sodium ion, it showed a significantly better short- and long-term capacity than other cathodes made of polymeric or inorganic materials. According to the study, the approach also achieved excellent results for magnesium and aluminum ions.
The scientists identified the organic compound hexaazatrinaphthalene (HATN) as a cathode material with high energy density and good storage readiness for methallions. HATN has already been tested in lithium ion batteries and supercapacitors, but, like most organic materials, it dissolved in the electrolyte over time. In order to stabilize the material, the researchers linked the individual molecules with binding bridges. The result was an organic polymer called polymeric HATN or PHATN. The capacity for sodium, aluminium and magnesium ions was excellent.