Saravanan Kuppan, Jarry Angelique, Kostecki Robert, Chen Guoying
Environmental Energy Technologies Division Lawrence Berkeley National Laboratory Berkeley, California 94720, USA.
Sci Rep. 2015 Jan 26;5:8027. doi: 10.1038/srep08027.
Understanding the kinetic implication of solid-solution vs. biphasic reaction pathways is critical for the development of advanced intercalation electrode materials. Yet this has been a long-standing challenge in materials science due to the elusive metastable nature of solid solution phases. The present study reports the synthesis, isolation, and characterization of room-temperature LixMn1.5Ni0.5O4 solid solutions. In situ XRD studies performed on pristine and chemically-delithiated, micron-sized single crystals reveal the thermal behavior of LixMn1.5Ni0.5O4 (0 ≤ x ≤ 1) cathode material consisting of three cubic phases: LiMn1.5Ni0.5O4 (Phase I), Li0.5Mn1.5Ni0.5O4 (Phase II) and Mn1.5Ni0.5O4 (Phase III). A phase diagram capturing the structural changes as functions of both temperature and Li content was established. The work not only demonstrates the possibility of synthesizing alternative electrode materials that are metastable in nature, but also enables in-depth evaluation on the physical, electrochemical and kinetic properties of transient intermediate phases and their role in battery electrode performance.
了解固溶体与双相反应途径的动力学含义对于先进插层电极材料的开发至关重要。然而，由于固溶体相难以捉摸的亚稳性质，这一直是材料科学中的一个长期挑战。本研究报告了室温下Li x Mn 1.5 Ni 0.5 O 4固溶体的合成、分离和表征。对原始的和化学脱锂的微米级单晶进行的原位XRD研究揭示了由三个立方相组成的Li x Mn 1.5 Ni 0.5 O 4（0≤x≤1）正极材料的热行为：LiMn 1.5 Ni 0.5 O 4（相I）、Li 0.5 Mn 1.5 Ni 0.5 O 4（相II）和Mn 1.5 Ni 0.5 O 4（相III）。建立了一个将相结构变化作为温度和锂含量函数的相图。这项工作不仅证明了合成本质上是亚稳的替代电极材料的可能性，而且还能够深入评估瞬态中间相的物理、电化学和动力学性质及其在电池电极性能中的作用。
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