聚(1,4-蒽醌)作为有机正极材料：对锂、钠、镁、钙的可观测键合性质模拟
Poly(1,4-anthraquinone) as an Organic Cathode Material: Simulation of Observable Bonding Properties to Li, Na, Mg, and Ca
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中文总结 AI 辅助
本研究采用DFT与DFTB模拟结合恒电流测量，揭示聚(1,4-蒽醌)与Li、Na、Mg、Ca的键合机制，解释了一价离子在该有机正极材料中容量更高的原因。
中文摘要 AI 辅助
聚(1,4-蒽醌)（P14AQ）已成为一种极具前景的正极材料，具备高容量与良好的循环稳定性，然而决定金属离子键合及电化学行为的原子级机制仍未被充分理解。为解决这一问题，本研究采用量子力学方法，特别是密度泛函理论（DFT）与密度泛函紧束缚理论（DFTB），探究Li、Na、Mg、Ca与P14AQ的键合机制。该材料的结构复杂性是一项关键挑战：P14AQ的多种构象体能量相近，但因存在显著能垒而在动力学上相互孤立。为应对这一问题，研究人员开发了一种自动化方法，通过取向标记方案生成周期性聚合物链中所有无旋转重复的独特P14AQ构象体。针对每个构象体，研究人员系统地将金属原子放置在每个氧位点附近，以全面探索键合构型。研究人员观察到两种结构基序：单金属-氧键以及与两个相对氧原子的配位。Li和Na呈现连续的能量分布，而Mg和Ca在两种基序之间存在能隙，且强烈倾向于双氧键合构型。恒电流测量结果支持这些发现：Ca和Mg的重量容量低于Li和Na；对于Na，不同数量的金属-氧键对应于实验中观测到的两个电压平台。总体而言，计算与实验结果相结合，解释了一价离子在P14AQ中容量更高的原因：二价离子因能量不利无法与单个氧位点有效键合，且聚合物链的构象分布阻碍了最优配位。
英文摘要
Poly(1,4-anthraquinone) (P14AQ) has emerged as a promising cathode material, offering high capacity and good cycling stability, yet the atomic-scale mechanisms governing metal-ion binding and electrochemical behavior remain poorly understood. To address this, we investigate the binding mechanisms of Li, Na, Mg, and Ca to P14AQ using quantum mechanical methods, particularly DFT and DFTB. A key challenge lies in the material's structural complexity: multiple conformers of P14AQ are energetically similar but kinetically isolated due to significant energy barriers. To account for this, we develop an automated method to generate all unique P14AQ conformers for a periodic polymer chain without rotational duplicates through an orientation labeling scheme. For each conformer, we systematically place a metal atom adjacent to every oxygen site, enabling a complete exploration of binding configurations. We observe two structural motifs: a single metal-oxygen bond and coordination to two opposite oxygen atoms. While Li and Na exhibit continuous energy distributions, Mg and Ca show an energy gap between the two motifs, with a strong preference for the two-oxygen binding configuration. Galvanostatic measurements support these findings by showing lower gravimetric capacities for Ca and Mg than for Li and Na. For Na, the different numbers of metal-oxygen bonds are reflected in the two voltage plateaus observed experimentally. Overall, the combined computational and experimental results explain the higher capacity of monovalent ions in P14AQ: divalent ions cannot bind efficiently to a single oxygen site due to unfavorable energetics, and the conformational distribution of the polymer chain prevents optimal coordination.
