Zinc is an inexpensive and widely available material that has long been used commercially in Zn–carbon and alkaline primary batteries, as well as in Zn–air primary batteries. Recently, rechargeable systems with mildly acidic electrolytes using zinc cations for charge transport—zinc-ion batteries (ZIBs) and zinc-metal batteries (ZMBs)—have attracted increasing attention. Compared with conventional lithium-ion batteries, these technologies offer several advantages, including the abundance of raw materials, lower production costs, a reduced CO₂ footprint 1 and the potential use of aqueous electrolytes. Since ZIBs and ZMBs generally deliver lower energy densities than lithium-ion batteries, they are particularly appealing for stationary energy storage applications.Despite their promise, several challenges still hinder widespread commercialization. Key issues include gas evolution and dendrite growth caused by uneven stripping and plating at the zinc anode, as well as the need for improved cathode active materials, where a major issue is transition metal leaching in contact to aqueous electrolytes. Focusing on the cathode side, materials with a spinel structure (A(II+)B₂(III+)O₄) have been repeatedly proposed as attractive active materials, not only in lithium-ion batteries 2, but also in context of ZMBs, like e.g. ZnMn₂O₄ 3 and ZnFe₂O₄ 4.In this work, electrospun zinc ferrite fibers were produced under different conditions and investigated in spinel|3M ZnSO4 + buffered aqueous electrolyte|Zn cells comparing acetate-based buffers at different pH levels with two commercially available phthalate- and MES-based buffers. Previous work in our group showed that application of ZnFe₂O₄ in combination with aqueous electrolytes leads to irreproducible results 4. This can be overcome by using electrospun fibers with improved surface area in combination with a buffered aqueous electrolyte. In addition, it was demonstrated that the adequate buffer composition and pH allow for moderation of additional processes in the cell, especially proton co-insertion.Acknowledgements: Bärbel Arling is doctoral student at the International Graduate School for Battery Chemistry, Characterization, Analysis, Recycling and Application BACCARA which is funded by the Ministry of Culture and Science of the State North-Rhine Westphalia. Patrick Mowe is funded by the Deutsche Forschungsgemeinschaft (DFG), project number 523164409. Literature1. Ruppert, J., et al., Competitive Rechargeable Zinc Batteries for Energy Storage. Advanced Energy Materials, 2025: p. e02866.2. Thackeray, M.M., Exploiting the spinel structure for Li‐ion battery applications: a tribute to John B. Goodenough. Adv Energy Mater, 2021. 11(2): p. 2001117.3. Cai, K., et al., Recent Advances on Spinel Zinc Manganate Cathode Materials for Zinc‐Ion Batteries. Chem Rec, 2022. 22(1): p. e202100169.4. Krämer, S., et al., Teaching an old dog new tricks: Ti-doped ZnFe2O4 as active material in zinc ion batteries – a proof of concept Energy Advances, 2024.
Neuhaus et al. (Thu,) studied this question.