3D-Microbattery Architectural Design Optimization Using Automatic Geometry Generator and Transmission-Line Model.

Optimization of the 3D battery architecture is crucial to improve the performance of microbatteries. However, such optimization is difficult and time consuming by hand for even experts. In this article, we propose a battery optimization system, which consists of an automatic geometry generator and performance simulators. The geometry generator creates feasible 3D batteries without using any human intuition and experience for the spatial arrangement of positive and negative electrodes. For quick evaluation of the internal resistance, which relates power and energy densities, we propose the transmission line model, the so-called 3D porous electrode model, as one of the performance simulators. To show the effectiveness of the optimization system, we designed the lithium-ion microbatteries. In the trade-off frontier for the internal resistance and the capacity, we successfully found a new battery architecture that has higher power and energy densities over the conventional interdigitated plates configuration.

Fock-Matrix Corrections in Density Functional Theory and Use in Embedded Mean-Field Theory.

We introduce Fock-corrected density functional theory (FCDFT), a semiempirical minimal-basis method part way between density-functional tight binding (DFTB) and DFT. FCDFT contains DFTB-like Fock-matrix contributions calculated using simple pairwise formulas and Slater-Koster transformations, but it also contains the full Kohn-Sham treatment of Coulombic electrostatics. The resulting method is better suited than either minimal-basis DFT or DFTB for modeling the low-level subsystem in embedded mean-field theory (EMFT), improving upon the former by correcting for basis-set incompleteness and upon the latter by properly accounting for electrostatics. EMFT calculations using DFT-in-FCDFT have much smaller errors in orbital energies, dipole moments, and reaction energies than our previous DFT-in-DFT calculations.

Embedded mean-field theory.

We introduce embedded mean-field theory (EMFT), an approach that flexibly allows for the embedding of one mean-field theory in another without the need to specify or fix the number of particles in each subsystem. EMFT is simple, is well-defined without recourse to parameters, and inherits the simple gradient theory of the parent mean-field theories. In this paper, we report extensive benchmarking of EMFT for the case where the subsystems are treated using different levels of Kohn-Sham theory, using PBE or B3LYP/6-31G* in the high-level subsystem and LDA/STO-3G in the low-level subsystem; we also investigate different levels of density fitting in the two subsystems. Over a wide range of chemical problems, we find EMFT to perform accurately and stably, smoothly converging to the high-level of theory as the active subsystem becomes larger. In most cases, the performance is at least as good as that of ONIOM, but the advantages of EMFT are highlighted by examples that involve partitions across multiple bonds or through aromatic systems and by examples that involve more complicated electronic structure. EMFT is simple and parameter free, and based on the tests provided here, it offers an appealing new approach to a multiscale electronic structure.

Organic dicarboxylate negative electrode materials with remarkably small strain for high-voltage bipolar batteries.

As advanced negative electrodes for powerful and useful high-voltage bipolar batteries, an intercalated metal-organic framework (iMOF), 2,6-naphthalene dicarboxylate dilithium, is described which has an organic-inorganic layered structure of π-stacked naphthalene and tetrahedral LiO4 units. The material shows a reversible two-electron-transfer Li intercalation at a flat potential of 0.8 V with a small polarization. Detailed crystal structure analysis during Li intercalation shows the layered framework to be maintained and its volume change is only 0.33%. The material possesses two-dimensional pathways for efficient electron and Li(+) transport formed by Li-doped naphthalene packing and tetrahedral LiO3C network. A cell with a high potential operating LiNi(0.5)Mn(1.5)O4 spinel positive and the proposed negative electrodes exhibited favorable cycle performance (96% capacity retention after 100 cycles), high specific energy (300 Wh kg(-1)), and high specific power (5 kW kg(-1)). An 8 V bipolar cell was also constructed by connecting only two cells in series.

Elimination of Translational and Rotational Motions in Nuclear Orbital Plus Molecular Orbital Theory: Contribution of the First-Order Rovibration Coupling.

The translation- and rotation-free nuclear orbital plus molecular orbital (TRF-NOMO) theory was developed to determine nonadiabatic nuclear and electronic wave functions. This study implemented a computational program for the TRF-NOMO method including first-order rotational terms, which corresponds to rovibronic coupling. Numerical assessments of first-order TRF-NOMO Hartree-Fock as well as second-order Møller-Plesset perturbation methods were carried out for several small molecules. The first-order contributions give small corrections in energy. Thus, we confirm that the approximate zeroth-order treatment is sufficient for eliminating the rotational contamination.

Elimination of translational and rotational motions in nuclear orbital plus molecular orbital theory.

The nuclear orbital plus molecular orbital (NOMO) theory was developed in order to determine the nonadiabatic nuclear and electronic wave functions. This study presents a formulation to remove the contamination of rotational motion as well as translational motion in the NOMO theory. We have formulated the translation- and rotation-free (TRF)-NOMO theory by introducing the TRF Hamiltonian. The principal moment of inertia, which is the denominator in the rotational Hamiltonian, is expanded in a Taylor series. The zeroth-order of the Taylor expansion corresponds to a rigid-body rotator. The first-order terms contribute the coupling between the vibration and the rotation. Hartree-Fock equations have been derived in the framework of the TRF-NOMO theory. Numerical assessments, which were preformed for H2, D2, T2, mu2 (muon dimmer), and H2O, confirmed the importance of the TRF treatment.