Solid Electrolyte Interphases in Magnesium Batteries

As human impact on the environment has come under increased scrutiny, more sustainable technologies for generating and storing energy have become necessary. Lithium-ion batteries (LIBs) have so far been instrumental in this process, offering reliable energy storage at both the large and small scale. However, LIBs suffer from high cost, and environmental damage and humanitarian concerns involved in the extraction of lithium and cobalt that are necessary for their function.

The magnesium battery has been identified as an attractive alternative to LIBs due to higher volumetric charge capacity, improved safety, greater abundance of raw materials and therefore reduced cost. Such batteries would be more sustainable environmentally due to reduced pollution, more sustainable socially because of Co mining's reliance on child labour and modern slavery, and more sustainable economically due to reduced cost.

The greatest limitation to the success of magnesium batteries has been the solid electrolyte interphase (SEI), a layer that forms on the surface of the negative electrode as it reacts with the electrolyte. The high charge density of Mg ions means that the electrostatic interactions within the SEI drastically slow down the rate of Mg ion diffusion. The resulting resistance must be overcome to realise the potential of Mg batteries.