Overcoming the Negative Energy Density Requirements in the Alcubierre Warp Field Equations with a Complex Shaping Function

The sampled negative energy density seen by inertial observers, in arbitrary quantum states is limited by quantum inequalities, which take the form of an inverse relation between the magnitude and duration of the negative energy. The quantum inequalities severely limit the utilization of negative energy to produce gross macroscopic effects, such as violations of the second law of thermodynamics. The restrictions on the sampled energy density along the worldlines of accelerated observers are much weaker than for inertial observers. Here we will illustrate this with several explicit examples. We consider the worldline of a particle undergoing sinusoidal motion in space in the presence of a single mode squeezed vacuum state of the electromagnetic field. We show that it is possible for the integrated energy density along such a worldline to become arbitrarily negative at a constant average rate. Thus the averaged weak energy condition is violated in these examples. This can be the case even when the particle moves at nonrelativistic speeds. We use the Raychaudhuri equation to show that there can be net defocusing of a congruence of these accelerated worldlines. This defocusing is an operational signature of the negative integrated energy density. These results in no way invalidate nor undermine either the validity or utility of the quantum inequalities for inertial observers. In particular, they do not change previous constraints on the production of macroscopic effects with negative energy, e.g., the maintenance of traversable wormholes.

Electrochemical energy storage is one of the critical technologies for energy storage, which is important for high‐efficiency utilization of renewable energy and reducing carbon emissions. In addition to the higher energy density requirements, safety is also an essential factor for developing electrochemical energy storage technologies. Lithium‐ion batteries (Li‐ion batteries) are commercialized as power batteries in electric vehicles (EVs) because of their advantages (such as high energy density, long life span, etc.), while for future electrochemical energy storage markets, lithium–sulfur (Li–S) and lithium–air (Li–air) batteries can be promising candidates for high energy density requirements. Therefore, this paper summarizes the present or potential thermal hazard issues of lithium batteries (Li‐ion, Li–S, and Li–air batteries). Moreover, the corresponding solutions are proposed to further improve the thermal safety performance of electrochemical energy storage technologies.

Polymer film capacitors are popular in many applications such as power systems, new energy vehicles and electromagnetic energy equipment. However, in the face of higher and higher working temperature and energy density requirements, energy storage characteristics of film capacitors needs to be improved. The charge injection characteristics between the electrode and the dielectric are a key factor affecting the energy storage characteristics of film capacitors. By depositing a high insulating inorganic layer on polymer surface, electrode-dielectric interface charge density can be controlled, and then the charge injection characteristics can be modulated to improve energy storage characteristics at high temperature. But the quantitative relationship between charge injection characteristics and energy storage performance needs further study. This paper proposed an energy storage and release model including charge injection characteristics, and simulated the impact of different interface charge density on energy storage of polyetherimide (PEI) composites at $150^{\circ}\mathrm{C}$. Simulation results match well with the experimental phenomena. Reducing electrode-dielectric interface charge density can effectively inhibit interface charge injection, reduce carrier mobility inside the dielectric and thus improve the energy storage density and efficiency. Under electric field of 511 $\mathrm{k}\mathrm{V}/\mathrm{m}\mathrm{m}$, with the interface charge density increasing from 0.1 $\mathrm{C}/\mathrm{m}^{3}$ to 15 $\mathrm{C}/\mathrm{m}^{3}$, the interface charge injection is obviously inhibited, the discharge energy density increasing from 1.86 $\mathrm{J}/\mathrm{m}^{3}$ to 3.62 $\mathrm{J}/\mathrm{m}^{3}$, and the charge-discharge efficiency increasing from 12.1% to 95.99%, which significantly improved high-temperature energy storage characteristics. This study provides theoretical guide for improving the high-temperature energy storage characteristics of dielectrics.

Enhanced energy density and fast-charging ability via directional particle configuration

We examine the maximum negative energy density which can be attained in various quantum states of a massless scalar field. We consider states in which either one or two modes are excited, and show that the energy density can be given in terms of a small number of parameters. We calculate these parameters for several examples of superposition states for one mode, and entangled states for two modes, and find the maximum magnitude of the negative energy density in these states. We consider several states which have been, or potentially will be, generated in quantum optics experiments.

With the increasing demand for high-performance power batteries in electric vehicles, low-altitude economy, military applications, and other fields, existing liquid electrolyte-based battery technologies are gradually becoming incapable of meeting the energy density and safety requirements. New battery systems based on solid electrolytes are the main candidate materials for future power batteries owing to their high safety and energy density. Thus far, researchers have conducted extensive studies on the ionic/electronic transfer mechanisms of solid electrolytes and electrode materials, as well as the cooperative effects and interface issues between them. Although much progress has been made, the practical application of solid-state batteries is still severely limited by the high interface impedance between the solid electrolyte and the anode. This impedance stems from incompatible physical and chemical properties and dynamic interface evolution. This paper focuses on the latest progress in the interface engineering strategies of solid electrolytes and anodes and systematically analyzes the cooperative coupling effect between charge transfer dynamics and mechanical stability at the interface. This review provides insights into the future research in this field, aiming to offer a new perspective to enhance our understanding of solid-state lithium batteries, thereby facilitating their more optimal design and promoting their practical applications.

The development of a rechargeable lithium cell power source as a replacement for silver-oxide-zinc cells in naval underwater vehicles is described. Progress made for the most promising lithium system, lithium-cobalt oxide, which has 2.5 times the theoretical energy density of silver-oxide-zinc, is summarized. Initial laboratory cell studies showed cobalt oxide can meet or exceed program goals. Recent work has scaled the fractional Ah capacity laboratory cells up to 1.1 and 2.5 Ah size. At this level also, many of the cells tested reached or surpassed required energy density and cycle-life requirements. >

Researchers worldwide are searching for new electrochemical energy storage materials that meet high energy density, life, cost, and safety requirements of batteries for electric vehicle applications. The strategies for developing new chemistries with higher energy density, stability and safety concerns involve mitigating the problems of existing materials and understanding the structural changes and their relations with materials activity which requires characterization assisted material synthesis. For lithium ion cathode design, some of the mitigation strategies for low electrochemical cycle life, stability and safety concerns involve, increase of lithium content, change transition metal composition and use of different dopants and surface coatings. However, each change brings additional challenge to understand the structural modifications induced and its relationship with materials activity.In this work, we synthesize a series of Al2O3-coated LiNixMnyCo1-x-yO2(NMC) materials with different transition metal compositions, various aluminum loadings, solvents and different annealing conditions. Then solid state NMR, electron microscopy, and high-resolution X-ray diffraction techniques are applied to examine the interfacial and bulk composition and structure of alumina-coated cathodes prepared under different annealing temperatures and with cathode compositions. Their chemical and structural evolution after electrochemical cycling are further studied with 7Li and 27Al solid state NMR.We find that higher annealing temperatures lead to a more homogeneous and strongly attached coating on the cathode surface, accompanied with the formation of the new LiAlO2 phase due to the interaction between the surface alumina coating and the surface lithium species from the cathodes. A strong diffusion of surface Al into the bulk after high-temperature annealing is also found for cathodes with low Mn content. Aluminum loading level also determines how effectively a dopant and coating develop in the material. Our electrochemical tests show that material performance strongly depend on right coating to dopant ratio and interface composition which should be tuned for every cathode composition. This brings the need for characterization assisted synthesis for development of next generation lithium ion cathodes1-3.

A comprehensive review of stationary energy storage devices for large scale renewable energy sources grid integration

Hydrothermal synthesis of LiMn2O4 onto carbon fiber paper current collector for binder free lithium-ion battery positive electrodes

After presenting a lemma, two theorems on negative energy density associated with a quantum free scalar field are established. The first theorem provides a lower bound for a non-negative weight function whose existence is guaranteed by the lemma. The above energy density is evaluated over an inertial world line of the Minkowski space-time. The second theorem provides an upper bound for the averaged (with respect to the sampling function) absolute expectation value of the negative energy-density function. In particular, a complex-valued sampling function is introduced by the first time so a more generalized formulation is proposed.

An analysis is presented of the Bianchi type I cosmological models with a bulk viscosity when the universe is filled with the stiff fluid p=ε while the viscosity is a power function of the energy density, such as η=α‖ε‖n. Although the exact solutions are obtainable only when the 2n is an integer, the characteristics of evolution can be clarified for the models with arbitrary value of n. It is shown that, except for the n=0 model that has solutions with infinite energy density at initial state, the anisotropic solutions that evolve to positive Hubble functions in the later stage will begin with Kasner-type curvature singularity and zero energy density at finite past for the n≥1 models, and with finite Hubble functions and finite negative energy density at infinite past for the n<1 models. In the course of evolution, matters are created and the anisotropies of the universe are smoothed out. At the final stage, cosmologies are driven to infinite expansion state, de Sitter space-time, or Friedman universe asymptotically. However, the de Sitter space-time is the only attractor state for the n< (1)/(2) models. The solutions that are free of cosmological singularity for any finite proper time are singled out. The extension to the higher-dimensional models is also discussed.

LiNi0.5Mn1.5O4 nano-submicro cubes as high-performance 5 V cathode materials for lithium-ion batteries

Crack initiation behavior in magnetoelectroelastic composite under in-plane deformation

In this paper, we study classical general relativistic static wormhole configurations with pseudospherical symmetry. We show that, in addition to the hyperbolic wormhole solutions discussed by Lobo and Mimoso in [Phys. Rev. D 82, 044034 (2010)], there exists another wormhole class, which is a truly pseudospherical counterpart of spherical Morris--Thorne wormhole (contrary to the Lobo--Mimoso wormhole class), since all constraints originally defined by Morris and Thorne for spherically symmetric wormholes are satisfied. We show that, for both classes of hyperbolic wormholes, the energy density, at the throat, is always negative, while the radial pressure is positive, contrary to the spherically symmetric Morris--Thorne wormhole. Specific hyperbolic wormholes are constructed and discussed by imposing different conditions for the radial and lateral pressures, or by considering restricted choices for the redshift and the shape functions. In particular, we show that a hyperbolic wormhole cannot be sustained at the throat by phantom energy and that there are pseudospherically symmetric wormholes supported by matter with isotropic pressure and characterized by space sections with an angle deficit (or excess).