This research automates edge detection for perovskite crystal grains using machine learning (ML). Once the edges of the crystal grains are located, a flood-fill algorithm can be used to find the distribution of crystal grain areas. The ML algorithm uses GNU Octave to run a regularized logistic regression algorithm that classifies each pixel of an input image as part of an edge or not part of an edge. The basic features used for the algorithm are each pixel’s grayscale intensity, its Sobel derivative. Higher order Sobel derivatives, higher degree polynomial terms, and intensities convolved by various kernels were used as additional features to improve the program’s accuracy and true-positive rate. Training data is obtained by using non-ML Canny Edge Detection to annotate the edges an SEM image of a pure perovskite solar cell (PSC). The classifier exhibits an 85.58% accuracy and produces an edge mask that clearly outlines the crystals visually. The ML edge mask exhibits far fewer false-positive mis-classifications for pixels in the middle of the crystals than Canny. However, the ML mask’s edges are fainter, owing to a lower true-positive classification rate. Using more kernels, higher order derivatives, and higher degree polynomial terms all significantly increased the true positive rate of the classifier, leading to thicker edges. This algorithm can greatly accelerate perovskite solar cell research (and potentially any research requiring particle size analysis), automating a process scientists previously had to perform by hand. This will facilitate the search for a solution for the world’s growing demands for renewable energy.

We attempt to reveal how electrolyte additives affect the structural evolution of the solid electrolyte interphase (SEI) film on the anode surface of a lithium-ion secondary battery. Employing the hybrid Monte-Carlo/molecular-dynamics method, we theoretically investigate the SEI film structures in organic liquid-electrolyte systems with and without an organosilicon additive. The results show that the excessive growth of the SEI film is suppressed by introducing the organosilicon additives. It is further elucidated that the decomposition products of the organosilicon molecules are stably aggregated in the vicinity of the anode surface, and protect the electrolyte solvents and the lithium salts from the further reductive decomposition. These findings imply that the organosilicon additive possibly improves the cycle performance of LIBs owing to the formation of the effective SEI film.

In energy storage systems, every component that makes up an electrode can greatly affect the electrochemical performance. One example includes the so-called “binders” used in secondary batteries. Herein, we compare the influence of using polyvinylidene fluoride (PVDF) or sodium carboxymethyl cellulose (CMC) on the electrochemical performance of an aluminium chloride battery (ACB) system. The active material of the cathode was a reduced graphene oxide dried under supercritical conditions (RGOCPD). Interestingly, while PVDF enabled one of the highest capacities reported for ACBs, the CMC resulted in a significant degradation of the cell’s performance.

Lithium-rich layered oxides such as Li2MnO3 have shown great potential as cathodes in Li-ion batteries, mainly because of their large capacities. However, these materials still suffer from structural degradation as the battery is cycled, reducing the average voltage and capacity of the cell. The voltage fade is believed to be related to the migration of transition metals into the lithium layer, linked to the formation of O-O dimers with a short bond length, which in turn is driven by the presence of oxygen holes due to the participation of oxygen in the redox process. We investigate the formation of O-O dimers for partially charged O1-Li2MnO3 using a first-principles density functional theory approach by calculating the reaction energy and kinetic barriers for dimer formation. Next, we perform similar calculations for partially charged O1-Li2IrO3, a Li-rich material for which the voltage fade was not observed during cycling. When we compare the stability of the oxygen framework, we conclude that the formation of O-O dimers is both thermodynamically and kinetically viable for O1-Li0.5MnO3. For O1-Li0.5IrO3, we observe that the oxygen lattice is much more stable, either returning to its original state when perturbed, or resulting in a structure with an O-O dimer that is much higher in energy. This can be explained by the mixed redox process for Li2IrO3, which is also shown from the calculated magnetic moments. The lack of O-O dimer formation in O1-Li0.5IrO3 provides valuable insight as to why Li2IrO3 does not demonstrate a voltage fade as the battery is cycled, which can be used to design Li-rich battery cathodes with an improved cycling performance.

High-energy lithium-sulfur (Li-S) batteries still suffer from poor rate capability and short cycle life caused by the polysulfides shuttle and insulating nature of S (and the discharge product, Li2S). Selenium disulfide (SeS2), with a theoretical specific capacity of 1342 mAh g−1, is a promising cathode material as it has better conductivity compared to sulfur. The electrochemical reaction kinetics of CNFs-S/SeS2 composites (denoted as CNFs/S1-xSex, where x ≤ 0.1) are expected to be remarkably improved because of the better conductivity of SeS2 compared to sulfur. Here, a high-performance composite cathode material of CNFs/S1-xSex for novel Li-S batteries is reported. The CNFs/S1-xSex composites combine the higher conductivity and higher density of SeS2 with high specific capacity of sulfur. The CNFs/S1-xSex electrode shows good initial discharge capacity of ∼1050 mAh g−1 at 0.05 C rate with high mass loading of materials (∼6-7 mg cm−2 of composites) and > 97% initial coulombic efficiency. The CNFs/S1-xSex electrode shows more than 600 mAh g-1 specific capacity after 50 charge-discharge cycles at 0.5C rate, much higher compared to the CNFs/S cathodes.

Monoclinic VO2 is a known polymorph of vanadium dioxide that has received much attention due to its oxidative capabilities, geometric configuration, and promising applications in functional windows. VO2 can usually be obtained through a hydrothermal method under high pressure. In this work we report a synthesis of VO2 doped with Manganese using a rapid single-step hydrothermal process with V2O5, manganese (II) acetate and citric acid as precursors. Different syntheses were carried out in which the concentration of V2O5 and citric acid remained constant whereas the concentration of manganese (II) acetate was varied. The reactants underwent a stirring phase for 30 minutes before being loaded into a hydrothermal reactor for 2.5 hours at 200°C. The resultant was washed three times to remove the residual precursors. Imaging and spectroscopy characterizations such as TEM, SEM and UV-VIS-NIR have been performed on different doping concentration and the results display a dependence on doping concentrations.

Brookite titanium dioxide is investigated from first principles as possible insertion-type cathode material for Li, Na and Mg. Recently structural similarity of this phase and amorphous titanium dioxide was reported. Low-concentration insertion energies and the corresponding voltages, however, suggest poor electrochemical performance of brookite in comparison to e.g. layered titania phases such as B-TiO2. We argue that this behavior could be explained by local electronic structure leading to higher voltages in amorphous compounds, since the lattice strains induced by intercalation in brookite are not sufficient to explain the poor binding energies with the investigated metals.