Department of Green and Sustainable Chemistry, Tokyo Denki University, 5Senju Asahi-Cho, Adachi, Tokyo 120-8551, Japan.
Frontier Research Institute for Materials Science, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan.
Nat Commun. 2016 Dec 23;7:13814. doi: 10.1038/ncomms13814.
Further increase in energy density of lithium batteries is needed for zero emission vehicles. However, energy density is restricted by unavoidable theoretical limits for positive electrodes used in commercial applications. One possibility towards energy densities exceeding these limits is to utilize anion (oxide ion) redox, instead of classical transition metal redox. Nevertheless, origin of activation of the oxide ion and its stabilization mechanism are not fully understood. Here we demonstrate that the suppression of formation of superoxide-like species on lithium extraction results in reversible redox for oxide ions, which is stabilized by the presence of relatively less covalent character of Mn with oxide ions without the sacrifice of electronic conductivity. On the basis of these findings, we report an electrode material, whose metallic constituents consist only of 3d transition metal elements. The material delivers a reversible capacity of 300 mAh g based on solid-state redox reaction of oxide ions.
为实现零排放车辆，需要进一步提高锂电池的能量密度。然而，由于商业应用中正极不可避免的理论限制，能量密度受到限制。超越这些限制的一种可能性是利用阴离子（氧离子）氧化还原，而不是传统的过渡金属氧化还原。然而，氧离子的激活起源及其稳定机制尚不完全清楚。在这里，我们证明了抑制锂提取过程中超氧类似物的形成可以导致氧离子的可逆氧化还原，而锰与氧离子的共价性相对较低可以稳定这种氧化还原，而不会牺牲电子导电性。基于这些发现，我们报告了一种电极材料，其金属成分仅由 3d 过渡金属元素组成。该材料基于氧化物离子的固态氧化还原反应，提供了 300 mAh g 的可逆容量。
