The growing demand for storage systems to be integrated into the processes of generating electricity from renewable sources to make up for the limits deriving from the discontinuous nature of the latter, together with the critical issues linked to the limited terrestrial abundance, the cost and the geopolitical risk of supplying the lithium, has given rise to an ever-increasing interest in the development of sodium ion batteries (NIB) to be used to replace and/or complement lithium ion batteries (LIB).

All components of the NIB are still being studied to try to increase their performance. Among the many active materials studied for the development of anodes to be used in NIBs, interest has also been directed towards those substances capable of forming an alloy with sodium.

Alloy anodes have the advantage of having low average potentials and high theoretical capacities. In this work we considered active materials based on metallic tin and binary oxides of iron and germanium (GFO). The experimental tests produced reproducible materials with valid electrochemical performances, equal to 350mAh/g at C/10 for the Sn-based anodes and 400mAh/g at C/10 for the doped GFO samples. This work reports the experimental investigations of the effects of binders and current collectors on the electrochemical performance of alloy anodes for sodium ion batteries. Following the description of the experimental tests, the first research relating to the creation of a theoretical model capable of simulating the behavior of alloy electrodes in the process of alloying and de-alloying of sodium ions is also reported, based both on theoretical elements than on experimental data.

The large expansion of the electrodes caused by sodiation has a strong impact on the behavior of the cell in NIBs; therefore, it is essential to develop specific theoretical models to simulate the behavior of electrodes following electrochemical reactions. The numerical simulations of the model may be useful for designing the structures of the various components present in future production electrodes.

The Report is available on the Italian site