Pakhira Anindya, Hariyani Shruti, Agbeworvi George, Ayala Jaime R, Weiland Conan, Jaye Cherno, Fischer Daniel A, Ma Lu, Banerjee Sarbajit
Department of Chemistry, Texas A&M University, College Station, TX, 77843, USA.
Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
Angew Chem Int Ed Engl. 2025 Aug 11;64(33):e202507650. doi: 10.1002/anie.202507650. Epub 2025 Jun 23.
Topochemical insertion/extraction of cations has emerged as a generalizable strategy for modulating the crystal and electronic structure of periodic solids. In contrast, strategies for topochemical anion insertion are poorly explored and fundamental principles for designing insertion hosts to accommodate anions remain scarce. Here, we observe reversible room-temperature fluoride-ion insertion within tunnels of SnTiO defined by the stereochemical expression of Sn 5s lone pairs. X-ray scattering studies of fluoride-ion-insertion-induced crystal structure modulation and X-ray absorption/emission spectroscopy probes of electronic structure along with magnetic susceptibility measurements and first-principles calculations are used to decipher design principles underpinning reversible fluoride-ion insertion and bulk diffusion. Fluoride-ion insertion is enabled by a combination of a large, polarizable tunnel, delocalized redox at Ti─O─Sn centers, inherent repulsion between the fluoride-ion and Sn 5s electron lone pairs, and the formation of dative interactions between Sn-centered σ-holes and fluoride-ions, yielding a reversible capacity of 0.5 fluoride-ions per SnTiO formula unit. Our results demonstrate that the complex interplay between dative interactions and stereochemically active lone pair repulsions is critical to defining the thermodynamics and kinetics controlling fluoride-ion insertion and diffusion. As such, the design of fluoride-ion insertion hosts for anion batteries requires site-selective modification to modulate lattice-ion interactions.
阳离子的拓扑化学插入/萃取已成为一种可推广的策略，用于调节周期性固体的晶体和电子结构。相比之下，拓扑化学阴离子插入的策略研究较少，设计容纳阴离子的插入主体的基本原理仍然匮乏。在此，我们观察到在由Sn 5s孤对的立体化学表达所定义的SnTiO隧道内，氟离子在室温下可进行可逆插入。通过氟离子插入诱导的晶体结构调制的X射线散射研究、电子结构的X射线吸收/发射光谱探测以及磁化率测量和第一性原理计算来解读支撑可逆氟离子插入和体扩散的设计原理。氟离子的插入是由大的、可极化的隧道、Ti─O─Sn中心的离域氧化还原、氟离子与Sn 5s电子孤对之间的固有排斥以及Sn中心的σ空穴与氟离子之间形成的配位相互作用共同实现的，每个SnTiO化学式单元产生0.5个氟离子的可逆容量。我们的结果表明，配位相互作用和立体化学活性孤对排斥之间的复杂相互作用对于定义控制氟离子插入和扩散的热力学和动力学至关重要。因此，用于阴离子电池的氟离子插入主体的设计需要进行位点选择性修饰以调节晶格离子相互作用。
