Martin Ebner

Battery Breakdown: Although a range of materials can be used for chemically storing electrical charge, many cannot be made into batteries that retain their capacity over many cycles. Failure may be because of secondary reactions, poisoning through the formation of surface coatings, or volumetric changes leading to fracture. Ebner et al. (p. 716 , published online 17 October) studied this last scenario in an operating battery using synchrotron x-ray tomographic microscopy, tracking both the chemical changes in the battery and the resulting mechanical changes in a tin oxide model system, which is known to undergo large volume changes.

The ability to engineer electrode microstructures to increase power and energy densities is critical to the development of high-energy density lithium-ion batteries. Because high tortuosities in porous electrodes are linked to lower delivered energy and power densities, in this paper, we experimentally and computationally study tortuosity and consider possible approaches to decrease it. We investigate the effect of electrode processing on the tortuosity of in-house fabricated porous electrodes, using three-dimensionally reconstructed microstructures obtained by synchrotron x-ray tomography. Computer-generated electrodes are used to understand the experimental findings and assess the impact of particle size distribution and particle packing on tortuosity and reactive area density. We highlight the limitations and tradeoffs of reducing tortuosity and develop a practical set of guidelines for active material manufacture and electrode preparation.