Stabilizing zinc metal anodes for rechargeable zinc-metal batteries: from imaging to interface engineering

Licentiate thesis, 2025

Ongoing trends in electrification and digitalization have pushed forward the diversification of energy storage systems, particularly rechargeable batteries, to meet the demands of various applications. To date, lithium-ion batteries remain the leading technology on the battery market, especially for electric vehicles. However, no single battery chemistry is suitable for all use cases, which emphasizes the importance of developing complementary battery technologies. Rechargeable zinc batteries, particularly with zinc metal anodes, have been suggested as an alternative solution due to cost, safety and sustainability aspects. However, inhomogeneous Zn deposition and side reactions on the zinc anodes continue to be major obstacles for the long-term stability of rechargeable Zn-metal batteries.

The cycle life of Zn-metal batteries can be extended by regulating Zn deposition and addressing interfacial issues on the Zn anode. In this thesis, the fundamental mechanisms of Zn deposition and dissolution have been investigated through real-time X-ray tomographic imaging, design of a functional cellulose-based separator and optimisation of the electrolyte formulation. From X-ray tomography we show how we can follow the deposition and stripping processes on the metal anode in real time and that we can quantitatively correlate the volume change of Zn during deposition and stripping and the Coulombic efficiency obtained from electrochemistry recorded simultaneously. To improve the processes at the metal anode interface we have also investigated the role of a functional cellulose-based separator, built up of (TEMPO)-oxidized cellulose nanofibrils and cellulose nanocrystals, as well as the role of changing the solvation structure of Zn ions in the electrolyte by a low-transition-temperature Zn(TFSI)₂ and ethylene glycol electrolyte formulation.