Structural and Electrochemical Studies on the Depolarizability of Manganese Dioxides

在过去的两年中，对二氧化锰的去极化率的基础研究得到了发展。这一系列实验和理论工作的目标是：（1）从理论电化学和结构无机化学相结合的角度理解二氧化锰在水和非水电池中的“去极化率”;（2）建立电化学体系中材料的氧化还原电化学的一些基本原理，包括可溶性过渡金属离子和有机化合物以及混合价态无机化合物。（1）二氧化锰均相电化学反应的研究，在电位-还原度曲线上，二氧化锰均相电化学反应的电位曲线为理想的S形，L-五氧化二铌在锂非水电池中畸变的S形电位曲线的研究，研究了过渡金属离子在酸性溶液中的电化学行为和有机化合物在非水溶液中的电化学行为，通过非原位X射线衍射研究证实了二氧化锰和五氧化二铌的拓扑还原反应，并提出了反应机理。本文从统计热力学的角度出发，提出了一种解释某些混合价化合物电势曲线的理论，强调了固体基质中电荷载体在电化学反应中的作用。

The fundamental reseach on the depolarizability of manganese dioxide has been developed during the past two years. The objectives in this series of experimental and theoretical works are;(1) to understand the "depolarizability" of manganese dioxide both in aqueous and nonaqueous cells in terms of the theoretical electrochemistry combined with structural inorganic chemistory, and(2) to establish some fundamentals on the redox electrochemistory of materials in electrochemical systems, which include the soluble transition metal ions and the organic compounds together with the mixed valence inorganic compounds.Specific experimental and theoretical works done are;(1) a study on the homogeneous electrochemical reaction of manganese dioxide, which recognized as an ideal S-shaped potential curve in the potential vs. the reduction degree plots, and(2) a study on the distorted S-shaped potential curve of L-niobium pentoxide in lithium nonaqueous cell.In order to support these studies, the electrochemical behaviors of the transition metal ions in an acid solution and of the organic compounds in a nonaqueous solution were also examined and the redox properties of materials were specified in terms of electron donor and acceptor.Topotactic reductions of manganese dioxide and L-niobium pentoxide were confirmed by ex-situ X-ray diffraction studies and the reaction mechanisms were proposed. A theory to explain the potential curves of some mixed valence compounds were developed on the basis of statistical thermodynamics, in which the roles of charge charriers in a solid matrix on the electrochemical reaction were emphasized.