A universal design for triggering the precise micro-structure reconstruction through in-situ electro-regulating to boost the pseudocapacitance of MnO_(2)

Developing a precise controllable strategy for modulating the micro-morphology,atom coordination environment,and electronic structure of electrode materials is crucial for the performance in the field of energy storage,yet still a tremendous challenge.Herein,a facile and universal in-situ electrochemical self-optimization design,electro-regulating,is designed to controllably produce electrode materials with abundant defects.Through detailed characterization studies,the microstructure of MnO_(2) is reconstructed after electro-regulating,which exhibits a structure of small fragments with numerous holes due to the partial self-dissolution of acidic oxides under an alkaline operating environment.Furthermore,the electro-regulating strategy not only presents the formation steps of numerous holes but is also accompanies by a number of O vacancies generation process due to the activation of an external electric field.This study provides a new inspiration for reasonably designing advanced functional electrode materials for various electrochemical applications and beyond.

Numerical reconstruction of microstructure of graphite anode of lithium-ion battery

Due to the presence of graphite flake cascades, the real graphite anode of Li-ion battery shows non-iso- tropic characteristic. The present work developed an ellipsoid-based simulated annealing method and numeri- cally reconstructed the three-dimensional microstructure of a graphite anode. The reconstructed anode is a composite of three clearly distinguished phases： pore （or electrolyte）, graphite, and solid additives, well representing the non- isotropic heterogeneous characteristic of real graphite anode. Characterization analysis of the reconstructed electrode gives information such as the connectivity of individual phase, the specific interracial area between solid and pore phase, and the pore size distribution. The effects of the ellipsoid size on the structural characteristics of graphite anode were particularly studied. As the size of the ellipsoidal particle slightly increases, the average pore diameter increases and as a result the specific interfacial area between the solid and pore phase in the reconstructed area decreases; compared with the equatorial radius, the polar radius of ellipsoidal graphite particles has more sig- nificant influence on the characteristics of electrode microstructure.

Thermal Response Variability of Random Polycrystalline Microstructures

A data-driven model reduction strategy is presented for the representation of random polycrystal microstructures.Given a set of microstructure snapshots that satisfy certain statistical constraints such as given low-order moments of the grain size distribution,using a non-linear manifold learning approach,we identify the intrinsic low-dimensionality of the microstructure manifold.In addition to grain size,a linear dimensionality reduction technique(Karhunun-Lo´eve Expansion)is used to reduce the texture representation.The space of viable microstructures is mapped to a low-dimensional region thus facilitating the analysis and design of polycrystal microstructures.This methodology allows us to sample microstructure features in the reduced-order space thus making it a highly efficient,low-dimensional surrogate for representing microstructures(grain size and texture).We demonstrate the model reduction approach by computing the variability of homogenized thermal properties using sparse grid collocation in the reduced-order space that describes the grain size and orientation variability.

Impact of carbon paper structural parameters on the performance of a polymer electrolyte fuel cell cathode via lattice Boltzmann method

Polymer electrolyte fuel cells(PEFCs)being employed in fuel cell electric vehicles(FCEVs)are promising power generators producing electric power from fuel stream via porous electrodes.Structure of carbon paper gas diffusion layers(GDLs)applying in the porous electrodes can greatly affect the PEFC performance,especially at the cathode side where electrochemical reaction is more sluggish.To discover the role of carbon paper GDL structure on the mass transfer properties,different cathode electrodes with dissimilar structural parameters are simulated via lattice Boltzmann method(LBM).3D contours of oxygen and water vapor concentration through the GDL as well as the 2D contours of current density on the catalyst layer are illustrated and examined.The results indicate that the carbon fiber diameter has a negligible impact on the current density while the impact of carbon paper thickness and porosity is significant.In fact,increasing of carbon paper thickness or porosity leads to lack of cell performance.