Metal-free batteries raise hope for eco-friendly grids

Rechargeable batteries that use ammonium cations as charge carriers could provide a sustainable alternative to metal-ion-based batteries such as lithium-ion, the team said.

Metal-ion batteries are the go-to energy storage solution, dominating the market for portable consumer electronics and electric vehicles due to their high energy density and versatility. However, metal ions used in the electrolytes come from lithium and declining resources which threatens long-term availability. Their toxicity and flammability can also be unsafe and harmful to the environment.

There have been several attempts to generate ammonium-ion-based batteries to solve sustainability and environmental issues because these cations are lightweight and easy to synthesise and recycle.

However, ammonium cations are prone to reduction into hydrogen and ammonia at low operation potential, preventing the batteries from achieving their full potential. They also dissolve readily in electrolytes, making them difficult to incorporate into electrode materials.

According to Husam Alshareef, postdoc Zhiming Zhao and coworkers, the team developed a high-efficiency metal-free battery by combining an ammonium-cation-containing electrolyte with carbon-based electrodes. The graphite cathode and the organic semiconductor anode are cheap, environmentally friendly and renewable, Zhao said.