These results suggest that natural areas provide a consistent positive environment for children with ADHD. However, more research is needed to obtain a fuller understanding of the influences of the physical environment on children with ADHD.

Microscale silicon particles in lithium-ion battery anodes undergo large volume changes during (de)lithiation, resulting in particle pulverization and surface area increase concomitant with a continuous growth of the solid-electrolyte-interphase. One approach to overcome these phenomena is to operate the silicon anode under capacity-limited conditions (i.e., with partial capacity utilization). Since crystalline silicon is irreversibly transformed into amorphous phases upon lithiation, the purpose of the partial capacity utilization is to maintain a crystalline phase and thus prevent particle disintegration. Here, we investigate the amorphization process of micro-sized silicon particles in a silicon-rich anode (70 wt% silicon) over extended charge/discharge cycling in half-cells with a lithium reference electrode, varying the lower cutoff potential of the Si electrode. While the capacity of Si electrodes after formation remain constant for lithiation cutoffs of ≥170 mV vs Li+/Li, their capacity continuously increases over cycling for cutoffs of <170 mV vs Li+/Li, implying an ongoing amorphization of the crystalline phase. To quantify the ratio of the amorphous phase fraction over cycling, we employed an in-situ XRD method, utilizing the copper reflex of the current collector as internal standard. This allowed to determine the extent of amorphization over the course of cycling depending on the lithiation potentials.

Isothermal microcalorimetry is used to study the heat flow of lithium-ion cells to provide insight into active material characteristics and to provide data required for the thermal optimization on the cell and system level. Recent research has shown the application of this technique to cells during high cycling rates, such as for fast charging. However, the limitation of isothermal microcalorimetry is the low-pass characteristic of the measured heat flow, introduced by the thermal inertia of the setup and the calorimeter itself. To solve this problem, we introduce an optimized cell holder design and a novel data processing method for a time-resolved measurement of highly dynamic heat flow profiles. These are described in detail and validated using a synthetic power profile applied to a dummy cell. Experiments on a graphite-lithium half-cell illustrate improvement of the method and the optimized cell holder when compared to the state-of-the-art setup, demonstrating a 3.6 times faster response time, which was further improved using a post-processing deconvolution technique. This improved time resolution provides the acquisition of more detailed features than currently shown in the literature and allows an accurate correlation of the thermal signals to electrochemical features like, e.g., the differential voltage of the cell.

A meaningful benchmarking of battery active materials with inherently different properties requires knowledge of both their intrinsic electrochemical properties as well as of the differences in the resulting porous electrode structures for equal, practically relevant areal capacities. Here we compare graphite and microsilicon anodes with practical areal capacities of 2.8 mAh cm−2 for lithium-ion batteries with regard to their temperature-dependent kinetic charge-transfer resistances (R ct) and their ion transport resistances through the electrolyte phase within the pores of the electrodes (R ion), measured via impedance spectroscopy. We deconvolute the kinetic resistance from the impedance spectra by individually measuring the temperature-dependent pore resistance between −5 and +45 °C, showing that the charge-transfer resistance dominates at low temperatures, while at high temperatures the pore resistance dominates for both electrode types due to the significantly higher activation energy of R ct. An analysis of the potential profile of the electrodes at different lithiation rates shows how the thinner silicon electrode is significantly less affected by R ion-induced transport losses compared to a thicker graphite electrode, resulting in lower overpotentials when fast-charging at high temperatures, despite similar kinetic resistances. Overall the silicon electrodes could be charged up to two times faster than graphite before reaching 0 V vs Li+/Li.