中南大学袁明亮团队报道了钠离子电池中Fe-Mn协同机理的理论研究。相关研究成果发表在2024年7月16日出版的《颗粒学报》。

该文通过第一性原理计算，初步探索了NaFeO₂（NFO）和NaMnO₂（NMO）两种构型的构造，并研究了不同铁锰比下的混合焓。结果表明，NaFe_3/8Mn_5/8O₂（NFMO）具有最稳定的热力学结构。随后对NFO、NMO和NFMO构型在钠提取过程中的混合焓和体积变化进行了计算，并给出了过渡金属（TM）和氧气的部分态密度（PDOS）和Bader电荷。

这些计算揭示了铁和锰的协同机制。铁和锰在钠提取过程中可以进行更复杂的电子交换，优化内部电子密度分布和整体电荷平衡，从而稳定晶体结构，减少深度钠提取过程中Fe³⁺向钠层的迁移。

Fe的3d电子和Mn的3d电子通过共享氧原子的2p轨道在Fe-Mn-O网络中相互作用。这种相互作用可以导致Mn³⁺原子周围的电子密度重新平衡，减轻由孤立Mn³⁺的d4构型引起的不对称电子密度分布，并抑制Mn³⁺的Jahn-Teller效应。此外，铁和锰之间的协同效应可以提供更平衡的电荷分布，减少氧原子电荷状态的极端变化，减少深钠提取过程中阴离子氧化还原反应引起的不可逆氧释放，从而提高材料的稳定性。

对铁和锰共掺杂时微观层面的相互作用机制的深入研究，为高性能阴极材料的合理设计和开发提供了有价值的见解。

附：英文原文

Title: Theoretical study on the synergistic mechanism of Fe-Mn in sodium-ion batteries

Author: Mingliang Yuan

Issue&Volume: 2024/07/16

Abstract: This article conducts first-principles calculations to initially explore the construction of two configurations, NaFeO2 (NFO) and NaMnO2 (NMO), and studies the mixing enthalpies under different Fe-Mn ratios. The results indicate that NaFe3/8Mn5/8O2 (NFMO) exhibits the most thermodynamically stable structure. Subsequent calculations on the mixing enthalpies and volume changes during the sodium extraction process for NFO, NMO, and NFMO configurations are presented, along with the partial density of states (PDOS) and Bader charges of transition metals (TM) and oxygen. These calculations reveal the synergistic mechanism of Fe and Mn. Fe and Mn can engage in more complex electron exchanges during sodium extraction, optimizing the internal electron density distribution and overall charge balance, thereby stabilizing the crystal structure and reducing the migration of Fe3+ to the sodium layers during deep sodium extraction. The interaction between Fe’s 3d electrons and Mn’s 3d electrons through the shared oxygen atoms’ 2p orbitals occurs in the Fe-Mn-O network. This interaction can lead to a rebalancing of the electron density around Mn3 atoms, mitigating the asymmetric electron density distribution caused by the d4 configuration of the lone Mn3 and suppressing the Jahn-Teller effect of Mn3+. Moreover, the synergistic effects between Fe and Mn can provide a more balanced charge distribution, reducing extreme changes to the charge state of oxygen atoms and decreasing the irreversible oxygen release caused by anionic redox reactions during deep sodium extraction, thereby enhancing the material’s stability. This in-depth study of the interaction mechanism at the microscopic level when co-doping Fe and Mn offers valuable insights for the rational design and development of high-performance cathode materials.

DOI: 10.1016/j.partic.2024.07.006

Source: https://www.sciencedirect.com/science/article/abs/pii/S1674200124001330