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L.K. Kiriinya

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Doctoral thesis (2025) - L.K. Kiriinya, E.M. Kelder, S.J. Picken
Fossil-fuel energy is finite and its associated negative environmental impact is fuelling efforts to provide alternative energy sources that are affordable, sustainable and efficient. This energy transition from the dominant fossil fuels to energy sources that have a lower carbon footprint is seen as an urgent call to adopt green and renewable energies. Renewable energy has long been poised as a strong alternative because of its circularity. However, most of the renewable energy sources are intermittent and require storage so as balance out the supply with the demand.

Electrochemical storage using batteries is the most commonly used storage technique due to its versatile nature in meeting varying energy demands. Batteries can be applied in stand-alone systems for large scale storage or in smaller distributed systems with wide spectrum of applications ranging from small portable devices such as mobile phones to EVs. The question now becomes whether the materials used for battery storage meet the threshold for circularity. The most advanced battery systems are based on Li-ion (LiBs) and still Lead-acid (LABs), with Na-ion (NiBs) beginning to gain some ground. Lead is considered toxic to both humans and the environment which has led to the push away from LABs. LiBs have gained popularity due to their high energy density, however, safety concerns and high material costs raise questions about their sustainability. NiBs present a lower cost option compared to the LiBs with acceptable performance. The consensus is that existing battery systems are not capable of meeting future energy storage demands and concerted efforts are underway to explore new battery chemistries that are sustainable, safe and affordable. Some of chemistries that have shown some promise are Zinc-ion and Mg-ion. In this work we focus on multivalent battery systems with a focus on Mg –ion batteries…
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Journal article (2025) - M.C. Kwakernaak, L.K. Kiriinya, W.J. Legerstee, W.M.J. Berghmans, C.G.T. Hofman, E.M. Kelder
We present magnesium alginate as an aqueous polymer electrolyte for use in magnesium batteries. Alginates are polysaccharides extracted from algae, which form hydrogel materials upon interaction with divalent and trivalent cations. They are renewable, non-toxic, biocompatible materials that are widely used in the food and pharmaceutical industries. Mg2+ is weakly bound to an alginate polymer, which results in a hydrogel-like material that contains mobile magnesium ions. We propose that this is the ideal situation for an electrolyte that behaves in a similar way as a ‘water-in-salt’ system. Magnesium alginate was successfully synthesized and characterized by FTIR, XRD, and PDF. Ionic conductivity was measured with EIS measurements; a 2 wt% magnesium electrolyte shows a conductivity of 1.8 mS/cm. During conductivity experiments, we noticed the formation of a black layer on magnesium electrodes, which can improve the ionic conductivity between the electrodes. We carefully characterized this layer with XPS and saw that it mainly consists of alginate derivatives. ...
The upcoming energy transition requires not only renewable energy sources but also novel electricity storage systems such as batteries. Despite Li-ion batteries being the main storage systems, other batteries have been proposed to fulfil the requirements on safety, costs, and resource availability. Moving away from lithium, materials such as sodium, magnesium, zinc, and calcium are being considered. Water-based electrolytes are known for their improved safety, environmentally friendliness, and affordability. The key, however, is how to utilize the negative metal electrode, as using water-based electrolytes with these metals becomes an issue with respect to oxidation and/or dendrite formation. This work studied magnesium, where we aimed to determine if it can be electrochemically deposited in aqueous solutions with alginate-based additives to protect the magnesium. In order to do so, atomic force microscopy was used to research the morphological structure of magnesium deposition at the local scale by using a probe—the tip of a cantilever—as the active electrode, during charging and discharging. The second goal of using the AFM probe technology for magnesium deposition and stripping was an extension of our previous study in which we investigated, for lithium, whether it is possible to measure ion current and perform nonfaradaic impedance measurements at the local scale. The work presented here shows that this is possible in a relatively simple way because, with magnesium, no dendrite formation occurs, which hinders the stripping process. ...
We present a sustainable, inherently safe battery chemistry that is based on widely available and cheap materials, that is, iron and manganese hosted in alginate bio-material known from the food and medical industry. The resulting battery can be recycled to allow circularity. The electrodes were synthesised by the alginate caging the multi-valent metals to form a hydrogel in an aqueous environment. Characterisation includes FTIR, XPS and Mössbauer spectroscopy. The electrochemical performance of the electrodes was investigated by performing cyclic voltammetry (CV) and (dis)charge experiments. Mn and Fe ions show good co-ordination with the alginic acid with higher oxidation states demonstrating complex bonding behaviour. The non-optimised iron and manganese alginate electrodes already exhibit a cycling efficiency of 98% and 69%, respectively. This work shows that Fe and Mn atomically disperse in a bio-based host material and can act as electrodes in an aqueous battery chemistry. While demonstrated at cell level, it is furthermore explained how these materials can form the basis for a (semi-solid) flow cell. ...