An increase in the amount of nickel in LiMO2 (M = Ni, Co, Mn) layered system is actively pursued in lithium‐ion batteries to achieve higher capacity. Nevertheless, fundamental effects of Ni element in the three‐component layered system are not systematically studied. Therefore, to unravel the role of Ni as a major contributor to the structural and electrochemical properties of Ni‐rich materials, Co‐fixed LiNi0.5+xCo0.2Mn0.3–xO2 (x = 0, 0.1, and 0.2) layered materials are investigated. The results, on the basis of synchrotron‐based characterization techniques, present a decreasing trend of Ni2+ content in Li layer with increasing total Ni contents. Moreover, it is discovered that the chex.‐lattice parameter of layered system is not in close connection with the interslab thickness related to actual Li ion pathway. The interslab thickness increases with increasing Ni concentration even though the chex.‐lattice parameter decreases. Furthermore, the lithium ion pathway is preserved in spite of the fact that the c‐axis is collapsed at highly deintercalated states. Also, a higher Ni content material shows better structural properties such as larger interslab thickness, lower cation disorder, and smoother phase transition, resulting in better electrochemical properties including higher Li diffusivity and lower overpotential when comparing materials with lower Ni content.

Li ion battery (LIB) is one of the most remarkable energy storage devices currently available in various applications. With a growing demand for high-performance batteries, the role of electrochemical analysis for batteries, especially, electrode reactions are becoming very important and crucial. Among various analytical methods, cyclic voltammetry (CV) is very versatile and widely used in many fields of electrochemistry. Through CV, it is possible to know electrochemical factors affecting the reaction voltage and reversibility, and furthermore, quantitative analysis on Li + diffusivity as well as intercalation and capacitive reactions, and also anionic redox reaction. However, the explanation or interpretation of the results of CV is often deficient or controversial. In this mini-review, we briefly introduce the principle of cyclic voltammetry and its applications in LIB to bring a better understanding of the electrochemical reaction mechanisms involved in LIB.

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This paper presents important, new results of a study on the problem of task scheduling and voltage allocation in dynamically variable voltage processors, the purpose of which was minimization of processor energy consumption. The contributions are twofold: (1) For given multiple discrete supply voltages and tasks with arbitrary arrival-time/deadline constraints, we propose a voltage allocation technique that produces a feasible task schedule with optimal processor energy consumption.(2) We then extend the problem to include the case in which tasks have nonuniform loads (i.e.; switched) capacitances and solve it optimally. The proposed technique, called Alloc-vt, in (1) is based on the prior results in [Yao, Demers and Shenker. 1995. In Proceedings of IEEE Symposium on Foundations of Computer Science. 374-382] (which is optimal for dynamically continuously variable voltages, but not for discrete ones) and [Ishihara and Yasuura. 1998. In Proceedings of International Symposium on Low Power Electronics and Design. 197-202] (which is optimal for a single task, but not for multiple tasks), whereas the proposed technique, called Alloc-vt cap , in (2) is based on an efficient linear programming (LP) formulation. Both techniques solve the allocation problems optimally in polynomial time.

The ever‐growing demand for high‐energy lithium‐ion batteries in portable electronics and electric vehicles has triggered intensive research efforts over the past decade. An efficient strategy to boost the energy and power density of lithium‐ion batteries is to increase the Ni content in the cathode materials. However, a higher Ni content in the cathode materials gives rise to safety issues. Herein, thermal expansion and oxygen vacancies are proposed as new critical factors that affect the thermal stability of charged Ni‐rich cathode materials based on a systematic synchrotron‐based X‐ray study of Li0.33Ni0.5+xCo0.2Mn0.3‐xO2 (x = 0, 0.1, 0.2) cathode materials during a heating process. Charged cathode materials with higher Ni contents show larger thermal expansion, which accelerates transition metal migration to the Li layers. Oxygen vacancies are formed and accumulate mainly around Ni ions until the layered‐to‐spinel phase transition begins. The oxygen vacancies also facilitate transition metal migration to the Li layers. Thermal expansion and the presence of oxygen vacancies decrease the energy barrier for cation migration and facilitate the phase transitions in charged cathode materials during the heating process. These results provide valuable guidance for developing new cathode materials with improved safety characteristics.