An isothermal, physics-based model was developed in COMSOL multiphysics software to simulate the galvanostatic discharge performance of LixC6/Liquid Electrolyte/ Liy(NiaCobMnc)O2 dual lithium-ion insertion cell at 298 K. Modeling results are compared with experimental data to provide further insight into design and optimization of these cells for advanced electric vehicles.

Although uranium oxides have played essential roles in many nuclear reactions, it is imperative to pursue alternative solutions to reuse the spent fuels due to paramount safety and economic concern. Spent nuclear oxide fuels include uranium dioxide (UO2), triuranium octoxide (U3O8) and uranium trioxide (UO3). In this work, first principles calculations based on density functional theory (DFT) were carried out on MUO2, MU3O8 and MUO3 (M= Li, Na and K) to explore their possibilities to serve as grid-storage-based cathode materials. In particular, the result of the optimal structures, average open circuit voltages (OCV) and mechanic stabilities during charge and discharge processes are presented. These results are also compared to available experimental data.

Isotropic and anisotropic conductive carbon particles, carbon black (CB) and vapor grown carbon fiber (VGCF), were incorporated into a Lithium Titanate (LTO) battery anode material composition, and their effect on conductivity and electrochemical properties investigated. Nanocomposite electrodes comprised of LTO, polyvinyldine floride (PVDF) and as little as 5 wt% VGCF are reported to manifest more than one order of magnitude enhancement in conductivity over their CB counterparts. VGCF-based anodes are also found to exhibit more stable voltage discharge profiles and as much as 20% improvement in capacity retention during extended electrochemical cycling at charge/discharge rates as high as 2.625 A/g (15 C). Remarkably, we find that the benefits of VGCF relative to CB conductivity aids diminish at higher particle loadings and that a LTO anode formulation containing 5 wt% CB | 5 wt% VGCF yields optimal capacity retention. At 5C, this composite system outperformed both the 10 wt% VGCF and 10 wt% CB electrode systems by delivering 20% higher capacity during extended charge/discharge cycling. We explain this finding in terms of two synergetic effects: enhanced electrode conductivity facilitated by incorporation of a percolated network of anisotropic VGCF particles; and shorter transport distances between the insulative LTO and high surface area CB.

This study reports a high-performance hybrid lithium-ion anode material using coaxially coated silicon shells on vertically aligned carbon nanofiber (VACNF) cores. The robust bush-like highly conductive VACNFs effectively connect high-capacity silicon shells for lithium-ion storage. Such architecture allows the Si shells to freely expand/contract in the radial direction during lithium-ion insertion/extraction. A high specific capacity of 3000-3650 mAh(gSi)-1 was obtained at C/1 rate, comparable to the maximum value of amorphous Si, and ∼89% of the capacity was retained after 100 charge-discharge cycles. The lithium-ion storage capacity remains nearly the same from C/10 to C/0.5 rates. The ability to obtain high capacity at significantly improved power rates while maintaining the extraordinary cycle stability demonstrates the utilization of the unique properties of such hybrid architecture for lithium-ion batteries.

Two new diamines containing three nitriles are synthesized via a 3-step route. They are polymerized with four commercial dianhydrides (i.e. 6FDA, OPDA, BTDA and PMDA) in N,N-dimethylacetamide (DMAc) to afford poly(amic acid)s, which are thermally cured at temperatures up to 300 °C to form tough, creasable films. Most of these polyimides are soluble in common solvents. Their glass transition temperatures range from 216 to 341 °C. The polyimides are stable up to 400 °C. The dielectric constants of these OPDA-based polyimides increase from 2.9 (CP2) to 4.7 as measured by the D-E loops.

LiMnPO4 cathode materials of various sizes and shapes are synthesized by a hydrothermal method. In order to control the morphology of the LiMnPO4 particles, a nonionic surfactant or a cationic surfactant has employed as a key additive to the reactant solution. LiMnPO4 nanoparticles of grain-shape and rod-shape can be made with sizes between about 100 and 300 nm by adding a nonionic large polymer surfactant. Micrometer-sized LiMnPO4 particles of cuboid shape result from the reaction with a cationic surfactant. LiMnPO4 spheres of about 20 μm diameter are produced when no surfactant is added. The cathode composed of nanocrystalline (about 100 nm size) LiMnPO4 exhibited the best performance with the specific capacity of 153 mAhg-1 for the first battery cycle.

Carbon-Li4Ti5O12 (C-LTO) and carbon nanotube-Li4Ti5O12 (CNT-LTO) nanocomposite particles have been synthesized by hydrothermal method and a following high-temperature calcinations using a mixture of micro-size Li-Ti-O precursors and conducting black and carbon nanotubes, respectively. Two different types of coating layers have been characterized and analyzed on two kinds of Li4Ti5O12 particles surface by high resolution transmission electron microscopy images (HR-TEM) and selected area electron diffraction (SAED). Typical HR-TEM images and SAED patterns at nano-scale confirmed and showed that both particles exhibited a well-developed spinel nanocrystal with average sizes around 20-50 nm. The C-LTO particles exhibited the roughly spherical shape with more than 5 nm graphitic coating uniformly on the spherical surfaces; however, the CNT-LTO particles showed uniform square nanocrystal with edge length around 30 nm and a few layers of graphene covering the surface.

Electrochemical studies of galvanostatic discharge/charge cycling capacity testing indicated that both Li4Ti5O12particles showed the superior initial discharge capacity of more than 200 mA·h/g at 0.1C rate, and also the CNT-LTO particles show much improved specific capacity than that of the C-LTO particles during different cycling processing. It has been proposed that, grephene covering layers and the CNT interconnection networks are prove to increase electronic conductivity and improve the kinetics of Li4Ti5O12 toward fast lithium insertion/extraction. The comparative experimental results demonstrated that both nanoscale grephene layer and CNT inter-networks among particles is highly effective in improving the electrochemical properties of the CNT-LTO particles.

This paper describes a novel ultracapacitor made from carbon nano-onions. Characterization of the material was performed including measurement of the impedance spectra and cyclic voltammetry. A new ultracapacitor model composed of an LRC circuit and a constant phase element was developed along with a parameter extraction procedure. The model was validated using experimental data and simulation.

Our study is motivated by the need for development and deployment of reliable and efficient energy storage devices, such as lithium-ion batteries. However, the rate-capacity loss is the key obstacle faced by current lithium-ion battery technology, hindering many potential large-scale engineering applications, such as future transportation modalities, grid stabilization and storage systems for renewable energy. During electrochemical processes, diffusion-induced stress is an important factor causing electrode material capacity loss and failure. In this study, we present models that are capable for describing diffusion mechanisms and stress formation in LiFePO4 nanoparticles, a lithium-ion battery cathode material which promises an alternative, with the potential for reduced cost and improved safety. To evaluate mechanics of diffusion-induced fractures, a plate-like model is adopted with anisotropic materials properties and volume misfits during the phase transformation are considered. Stress distribution at phase boundaries and fracture mechanics information (energy release rates and stress intensity factors) are provided to further understand the stress development due to lithium-ion diffusion during discharging. This study contributes to the fundamental understanding of kinetics of materials in lithium-ion batteries, and results from our stress analysis provides better electrode materials design rules for future lithium-ion batteries.

We explore, via density functional theory (DFT) calculations, the effect on the barrier height for Li and Na diffusion in bulk Si of the presence of an extra Li/Na atom at the neighboring tetrahedral (T) or hexagonal (H) interstitial site. For both neighboring sites, the lowest diffusion barrier height is reduced, although the magnitude of the reduction depends on the inter-atomic distance between the 2 Li/Na atoms. We further calculate the effective interaction between the 2 atoms and show that it is a strong predictor of diffusion barrier heights for both Li-Si and Na-Si systems. Importantly, the correlation between inter-dopant interaction and barrier height may be used in future work to predict the diffusion barriers at higher concentration of inserted atoms.