Dual-Ion Batteries – Chances for Stationary Energy Storages By Electrode Structuring

In recent years, energy usage has changed and renewable energy sources are getting more and more important. These green sources (e.g. wind or solar energy) are generated locally but are strongly dependent on current weather conditions. Thus the demand on decentralized large-scale energy storages grows continuously.

In order to fit this market dual-ion batteries offer a high promising technology for stationary energy storage. This system has several benefits compared to the classical lithium-ion battery technology: low cost metal-free active materials, safe and non-toxic electrolytes and an extremely high cycling stability or life time, respectively. Furthermore the opportunity to use water soluble binders and thus cheaper aqueous suspensions in electrode production with a distinct reduction of energy during drying should be noticed.

This work focuses on process engineering aspects and challenges of the electrode production in order to transfer this new battery technology towards technical scale and continuous production processes.

Since particularly ion transport limitations due to large intercalating anions during charge are challenging, specific attention is paid to dual-ion battery electrode structures. Process engineering approaches to compensate these hindrances by optimizing the processing route and the electrode structure will be presented. These improvements result in up to 10 % higher capacities compared to available studies and capacity retentions from over 80 % after 5000 cycles (see figure 1).

The electrode structure is the key factor to support the ion transport for a reliable electrochemical performance. The total diffusion coefficient correlates with the ion mass transport within the electrolyte filled pore structure taking the porosity as well as the tortuosity into account. The presented work includes the determination of these structural parameters via mercury intrusion measurements and points out their contribution to understand transport limitation of large anions and its influence on electrochemical performance.