Abate Iwnetim I, Pemmaraju C Das, Kim Se Young, Hsu Kuan H, Sainio Sami, Moritz Brian, Vinson John, Toney Michael F, Yang Wanli, Gent William E, Devereaux Thomas P, Nazar Linda F, Chueh William C
Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, CA 94305, USA.
Stanford Institute for Materials & Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.
Energy Environ Sci. 2021;14(9). doi: 10.1039/d1ee01037a.
Stabilizing high-valent redox couples and exotic electronic states necessitate an understanding of the stabilization mechanism. In oxides, whether they are being considered for energy storage or computing, highly oxidized oxide-anion species rehybridize to form short covalent bonds and are related to significant local structural distortions. In intercalation oxide electrodes for batteries, while such reorganization partially stabilizes oxygen redox, it also gives rise to substantial hysteresis. In this work, we investigate oxygen redox in layered NaMnO, a positive electrode material with ordered Mn vacancies. We prove that coulombic interactions between oxidized oxideanions and the interlayer Na vacancies can disfavor rehybridization and stabilize hole polarons on oxygen (O) at 4.2 V vs. Na/Na. These coulombic interactions provide thermodynamic energy saving as large as O-O covalent bonding and enable ~ 40 mV voltage hysteresis over multiple electrochemical cycles with negligible voltage fade. Our results establish a complete picture of redox energetics by highlighting the role of coulombic interactions across several atomic distances and suggest avenues to stabilize highly oxidized oxygen for applications in energy storage and beyond.
稳定高价氧化还原对和奇异电子态需要了解其稳定机制。在氧化物中，无论它们是用于能量存储还是计算，高度氧化的氧化物阴离子物种会重新杂化以形成短共价键，并且与显著的局部结构畸变有关。在电池的插层氧化物电极中，虽然这种重组部分稳定了氧氧化还原，但也会导致大量滞后现象。在这项工作中，我们研究了层状NaMnO（一种具有有序Mn空位的正极材料）中的氧氧化还原。我们证明，氧化的氧化物阴离子与层间Na空位之间的库仑相互作用不利于重新杂化，并在相对于Na/Na为4.2 V时稳定氧（O）上的空穴极化子。这些库仑相互作用提供了与O-O共价键合一样大的热力学能量节省，并在多个电化学循环中实现了约40 mV的电压滞后，且电压衰减可忽略不计。我们的结果通过突出几个原子距离上库仑相互作用的作用，建立了氧化还原能量学的完整图景，并为在能量存储及其他领域中稳定高度氧化的氧提供了途径。
