Lithiation and Delithiation Properties of Si-based Electrodes Pre-coated with a Surface Film Derived from an Ionic-liquid Electrolyte

Ionic-liquid electrolytes can enhance battery performance and safety but are expensive. To reduce the use of ionic-liquid electrolytes, we investigated the charge/discharge properties of Si-based electrodes in an organic-liquid electrolyte, where the electrode surface was pre-coated with a film derived from an ionic-liquid electrolyte. No improvement in the electrode performance was observed compared to that of a nonmodified Si electrode. Once the modified film was broken down, a stable surface film could not be reformed in the organic-liquid electrolyte

Electrochemical Lithiation and Delithiation Properties of FeSi2/Si Composite Electrodes in Ionic-Liquid Electrolytes

We investigated the applicability of ionic-liquid electrolytes to FeSi2/Si composite electrode for lithium-ion batteries. In conventional organic-liquid electrolytes, a discharge capacity of the electrode rapidly faded. In contrast, the electrode exhibited a superior cycle life with a reversible capacity of 1000 mA h g(Si)−1 over 850 cycles in a certain ionic-liquid electrolyte. The difference in the cycle life was explained by surface film properties. In addition, the rate performance of the FeSi2/Si electrode improved in another ionic-liquid electrolyte. Remarkably, lithiation of only Si in FeSi2/Si composite electrode occurred whereas each FeSi2- and Si-alone electrode alloyed with Li in the ionic-liquid electrolyte. FeSi2 certainly covered the shortcomings of Si and the FeSi2/Si composite electrode exhibited improved cycle life and rate capability compared to Si-alone electrode

Effect of Annealing Temperature of Ni-P/Si on its Lithiation and Delithiation Properties

Annealed Ni–P–coated Si (Ni–P/Si) anodes for lithium-ion batteries have shown a superior cycle life with discharge capacity of 1000 mA h g−1 over 1100 cycles in some ionic-liquid electrolytes. However, the annealing temperature has yet to be optimized for Ni–P/Si electrodes. We investigated the electrochemical performance of Ni–P/Si electrode annealed at various temperatures in this study. The Ni–P/Si electrodes annealed at 800 ± 20 °C exhibited a superior cycle life with a reversible capacity of 1000 mA h g−1 over 1000 cycles, whereas the capacity of the electrodes annealed at temperatures of 750 °C and 850 °C faded at approximately 500 cycles. At 800 °C, a newly formed NiSi2 phase was theorized to significantly contribute to improving adhesion between the Ni–P coating layer and the Si particles. The Ni–P coating particles tended to aggregate at 850 °C, leading to a reduction in the coating effect, that is, a decline in their reactivity with Li+, acceleration of electrode disintegration, and a reduction in electrical conductivity. On the other hand, Ni–P/Si electrodes annealed at 850 °C exhibited a superior rate performance. The amount of available NiSi2 which ultimately contributed to higher reactivity with Li should increase

Action Research as a Methodology of Educational Study

This paper intends to discuss some theoretical issues of Action Research as a methodology of educational research. Action research has been developed in the field of social investigation, especially in workplaces. In the 1970s, some argument was brought out on the cognitive problems in social science and on the way of understanding of the world, not only as the objective existence but as emergent and interactional forms constructed with others. Also, Participatory Research has been created through adult educational practices in developing countries, and research networks have been constructed by International Council of Adult Education. Theoretically, this movement was first influenced by the philosophy of Paulo Freire. Considering these historical backgrounds, our discussion will focus on some controversial issues of AR and PR; a) problems of practical or reflective knowledge derived from the process of research; b) relationships between researchers and participants; and c) attributions as a way of inquiry. Finally, we examine some problems of validity of AR or PR

Electrochemical Lithiation and Delithiation Properties of FeSi2/Si Composite Electrodes in Ionic-Liquid Electrolytes

We investigated the applicability of ionic-liquid electrolytes to FeSi2/Si composite electrode for lithium-ion batteries. In conventional organic-liquid electrolytes, a discharge capacity of the electrode rapidly faded. In contrast, the electrode exhibited a superior cycle life with a reversible capacity of 1000 mA h g(Si)−1 over 850 cycles in a certain ionic-liquid electrolyte. The difference in the cycle life was explained by surface film properties. In addition, the rate performance of the FeSi2/Si electrode improved in another ionic-liquid electrolyte. Remarkably, lithiation of only Si in FeSi2/Si composite electrode occurred whereas each FeSi2- and Si-alone electrode alloyed with Li in the ionic-liquid electrolyte. FeSi2 certainly covered the shortcomings of Si and the FeSi2/Si composite electrode exhibited improved cycle life and rate capability compared to Si-alone electrode