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The application of silicon (Si) as potential anode material in Li-ion batteries provides a more than nine-fold increase in gravimetric storage capacity compared to conventional graphite anodes. However, full lithiation of Si induces the volume to increase by approximately 300%. Such enormous volume expansion causes large mechanical stress, resulting in non-elastic deformation and crack formation. This ultimately leads to anode failure and strong decrease in cycle life. This problem can be resolved by making use of structured anodes with small dimensions. Particularly honeycomb-shaped microstructures turned out to be beneficial in this respect. In the present paper, finite element modeling was applied to describe the experimentally observed mechanical deformation of honeycomb-structured Si anodes upon lithiation. A close agreement between simulated and experimentally observed shape changes is observed in all cases. The predictive ability of the model was further exploited by investigating alternative geometries, such as square-based microstructure. Strikingly, dimension and pattern optimization shows that the stress levels can be reduced even below the yield strength, while maintaining the footprint-area-specific storage capacity of the microstructures. The pure elastic deformation is highly beneficial for the fatigue resistance of optimized silicon structures. The obtained results are directly applicable for other (de)lithiating materials, such as mixed ionic-electronic conductors (MIEC) widely applied in Li-ion and future Na-ion batteries.

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In Denmark, biomass has been implemented in the majority of power plants either by firing biomass alone or co-firing of biomass and fossil fuels/additives. This has resulted in an accumulation of experience over the past two decades both from corrosion testing and also the assessment of failures which has given understanding with respect to alloy selection and corrosion rates at various temperatures. Many laboratory investigations focusing on specific aspects of corrosion in controlled atmospheres have also been undertaken to give improved understanding of corrosion mechanisms. However, there are still areas where further investigations are underway, with respect to both laboratory and field testing. The present focus areas of research include: a) Use of coatings in biomass power plants where the coatings perform differently in different biomass plants depending on fuel mix and temperature b) Importance of understanding the microstructure of component materials and how microstructure evolution with time and temperature can influence corrosion. This paper will recap past experience and highlight some of the results from the new research. Based on the brief review of research in the field, and the research described in detail in this paper, critical unresolved issues and a way forward for the industry is presented.