A facile coprecipitation approach for synthesizing LaNi0.5Co0.5O3 as the cathode for a molten-salt lithium-oxygen battery.

The cathode of a lithium-oxygen battery (LOB) should be well designed to deliver high catalytic activity and long stability, and to provide sufficient space for accommodating the discharge product. Herein, a facile coprecipitation approach is employed to synthesize LaNi0.5Co0.5O3 (LNCO) perovskite oxide with a low annealing temperature. The assembled LOB exhibits superior electrochemical performance with a low charge overpotential of 0.03-0.05 V in the current density range of 0.1-0.5 mA cm-2. The battery ran stably for 119 cycles at a high coulombic efficiency. The superior performance is ascribed to (i) the high catalytic activity of LNCO towards oxygen reduction/evolution reactions; (ii) the increased temperature enabling fast kinetics; and (iii) the LiNO3-KNO3 molten salt enhancing the stability of the LOB operating at high temperature.

Relative error's quadratic dependence on the electric current and the methods for its compensation in fiber optic current sensor systems.

We find that the relative error of a fiber optic current sensor (FOCS) increases quadratically with the electric current to be measured, causing unacceptable inaccuracy for direct current (DC) measurements beyond 100 kA. We prove analytically and confirm experimentally that such a nonlinear relative error escalation (REE) mainly originates from the residual linear birefringence of the spun fiber used in the FOCS. We propose and demonstrate that by first measuring residual linear birefringence, together with the circular birefringence of the spun fiber, the REE of the FOCS can be significantly reduced from -1.22% to -0.15% at 200 kA DC by a compensation scheme using the measured birefringences in the quadratic expression we derived. Further reduction of the REE to -0.02% at 200 kA DC can be obtained if the quadratic relation between the REE and the current under test is experimentally obtained. Our work points to a new direction for drastically improving the accuracy of FOCS at large currents and shall prove beneficial for scientists and engineers working in the field of current sensing.

Introduction and measurement of the effective Verdet constant of spun optical fibers.

We introduce the term effective Verdet constant to describe the effect of spun fiber fabrication parameters on the Faraday polarization rotation sensitivity in response to a longitudinal magnetic field along the fiber. We obtain the expression of the effective Verdet constant of a spun fiber showing that it is always less than that of an ideal fiber free of birefringence by a factor relating to the ratio of spin twist rate to unspun fiber retardation per unit length. The larger the ratio, the closer the effective Verdet constant to that of the ideal fiber is. By measuring the polarization rotation in spun fibers with a highly accurate polarization analysis system made with binary polarization rotators, we experimentally obtain the effective Verdet constants of three different high birefringence spun fibers from three different manufactures at 1310 nm, with values of 1.07 × 10-6 rad/A, 1.05 × 10-6 rad/A, and 1.04 × 10-6 rad/A, respectively, which are 98%, 96%, and 95% of that of the ideal fused silica fiber free of birefringence. Our work is important for understanding the Faraday Effect in the spun optical fibers, as well as for quantifying the Faraday sensitivity of different spun fibers for electrical current and magnetic field sensing applications.

Quantum verification of NP problems with single photons and linear optics.

Quantum computing is seeking to realize hardware-optimized algorithms for application-related computational tasks. NP (nondeterministic-polynomial-time) is a complexity class containing many important but intractable problems like the satisfiability of potentially conflict constraints (SAT). According to the well-founded exponential time hypothesis, verifying an SAT instance of size n requires generally the complete solution in an O(n)-bit proof. In contrast, quantum verification algorithms, which encode the solution into quantum bits rather than classical bit strings, can perform the verification task with quadratically reduced information about the solution in [Formula: see text] qubits. Here we realize the quantum verification machine of SAT with single photons and linear optics. By using tunable optical setups, we efficiently verify satisfiable and unsatisfiable SAT instances and achieve a clear completeness-soundness gap even in the presence of experimental imperfections. The protocol requires only unentangled photons, linear operations on multiple modes and at most two-photon joint measurements. These features make the protocol suitable for photonic realization and scalable to large problem sizes with the advances in high-dimensional quantum information manipulation and large scale linear-optical systems. Our results open an essentially new route toward quantum advantages and extend the computational capability of optical quantum computing.

Review on Polymer-Based Composite Electrolytes for Lithium Batteries.

Lithium-ion batteries have dominated the high performance and mobile market for last decade. Despite their dominance in many areas, the development of current commercial lithium-ion batteries is experiencing bottlenecks, limited by safety risks such as: leakage, burning, and even explosions due to the low-boiling point organic liquid electrolytes. Solid electrolyte is a promising option to solve or mitigate those issues. Among all solid electrolytes, polymer based solid electrolytes have the advantages of low flammability, good flexibility, excellent thermal stability, and high safety. Numerous researchers have focused on implementing solid polymer based Li-ion batteries with high performance. Nevertheless, low Li-ion conductivity and poor mechanical properties are still the main challenges in its commercial development. In order to tackle the issues and improve the overall performance, composites with external particles are widely investigated to form a polymer-based composite electrolyte. In light of their work, this review discusses the progress of polymer-based composite lithium ion's solid electrolytes. In particular, the structures, ionic conductivities, electrochemical/chemical stabilities, and fabrications of solid polymer electrolytes are introduced in the text and summarized at the end. On the basis of previous work, the perspectives of solid polymer electrolytes are provided especially toward the future of lithium ion batteries.