Ko Sarah L, Dorrell Jordan A, Alter Ethan D, Ta Anthony C, Morris Andrew J, Griffith Kent J
Department of Chemistry and Biochemistry, University of California, San Diego, California 92093, United States.
School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
J Am Chem Soc. 2025 Mar 12;147(10):8513-8522. doi: 10.1021/jacs.4c16977. Epub 2025 Feb 3.
Careful control over the defect chemistry of crystalline compounds is typically critical to transport phenomena (ion, electron, phonon). In one-dimensional (1D) ion conductors, even small concentrations of defects in the diffusion pathway can be pernicious. Wadsley-Roth block phases are 1D ion conductors with high redox capacity and among the highest diffusivity of any battery electrode materials. The origin of their high-rate transport has been attributed to parallel tunnels that could impart defect tolerance, but direct evidence is limited. Herein, a new lithium-ion battery negative electrode material, NaNbO, is described that exhibits extreme defect tolerance. Multimodal characterization combining neutron diffraction, Na solid-state NMR spectroscopy, and DFT calculations reveals that more than half of the Na in NaNbO is in diffusion tunnel-blocking cuboctahedral environments (similar to the perovskite A-site). Despite the high point-defect concentration, NaNbO can reversibly lithiate to LiNaNbO and cycle 200 mAh·g in 10 h and 100 mAh·g in 3 min in large 4-23 μm (D-D) particles. synchrotron diffraction shows an anisotropic and asymmetric lithiation/delithiation process with two first-order phase transitions including one with nearly zero volume change. LiNaNbO also exhibits evidence for reversible Nb-Nb bond formation. From the same diffraction measurements, Nb-Nb distances between edge-sharing octahedra at the block peripheries vary from . 3.4 to 2.8 and back to 3.4 Å over one lithium insertion/extraction cycle, in quantitative agreement with the Nb-Nb bond formation charge storage mechanism recently proposed from the computational lithiation of several different Wadsley-Roth compounds.
对晶体化合物的缺陷化学进行精确控制通常对传输现象（离子、电子、声子）至关重要。在一维（1D）离子导体中，即使扩散路径中存在少量缺陷也可能是有害的。沃兹利 - 罗斯块相是具有高氧化还原容量的一维离子导体，并且是所有电池电极材料中扩散率最高的之一。它们高速率传输的起源归因于可能赋予缺陷耐受性的平行隧道，但直接证据有限。在此，描述了一种新型锂离子电池负极材料NaNbO，其表现出极高的缺陷耐受性。结合中子衍射、钠固态核磁共振光谱和密度泛函理论计算的多模态表征表明，NaNbO中超过一半的钠处于扩散隧道阻塞的立方八面体环境中（类似于钙钛矿A位）。尽管点缺陷浓度很高，但NaNbO在4 - 23μm（D - D）的大颗粒中仍能可逆地锂化形成LiNaNbO，在10小时内循环容量可达200 mAh·g，在3分钟内可达100 mAh·g。同步加速器衍射显示了一个各向异性和不对称的锂化/脱锂过程，有两个一级相变，其中一个相变的体积变化几乎为零。LiNaNbO还显示出可逆Nb - Nb键形成的证据。从相同的衍射测量中可以看出，在一个锂插入/提取循环中，块体周边边缘共享八面体之间的Nb - Nb距离从3.4变化到2.8，然后又回到3.4 Å，这与最近从几种不同沃兹利 - 罗斯化合物的计算锂化中提出的Nb - Nb键形成电荷存储机制在定量上一致。
