Langella Aniello, Massaro Arianna, Muñoz-García Ana B, Pavone Michele
Department of Chemical Sciences, University of Naples Federico II, Complesso Univ. Monte Sant'Angelo Via Cintia 21, Naples 80126, Italy.
National Interuniversity Consortium of Materials Science and Technology - Reference Center for Electrochemical Energy Storage (INSTM-GISEL), Via G. Giusti 9, Firenze 50121, Italy.
ACS Energy Lett. 2025 Feb 6;10(3):1089-1098. doi: 10.1021/acsenergylett.4c03335. eCollection 2025 Mar 14.
Mn-based layered oxides hold great promise as high-energy, cost-effective cathodes for sodium-ion batteries (NIBs), but repetitive Na cycling induces harmful phase transitions. Understanding these mechanisms is essential for designing better performing NIB cathodes. Applying density functional theory (DFT) and variable cell-nudged elastic band (VC-NEB) calculations, we provide atomistic insights into phase transformation pathways and energy barriers in P2-Na MnO material and its Ni-doped variant. We reveal the key P2-to-OP4/O2 and P2-to-P2' transitions that occur across various sodiation levels, involving substantial rearrangements around the transition metal sites, with tetrahedral transition states accountable for energy barriers. Our analysis of bond length and angle distortions highlights that shear deformations are pivotal in triggering P-to-O gliding at low sodium levels. Based on these insights, our structural distortion metrics offer a straightforward and computationally efficient descriptor to evaluate structural integrity for these layered oxides, enabling the design of NIBs with improved stability and extended lifespan.
锰基层状氧化物作为钠离子电池（NIBs）的高能量、低成本阴极具有很大的潜力，但重复的钠循环会引发有害的相变。了解这些机制对于设计性能更好的 NIB 阴极至关重要。通过应用密度泛函理论（DFT）和可变晶胞推挤弹性带（VC-NEB）计算，我们对 P2-NaMnO 材料及其镍掺杂变体中的相变途径和能垒提供了原子尺度的见解。我们揭示了在各种钠化水平下发生的关键的 P2 到 OP4/O2 和 P2 到 P2' 转变，这些转变涉及过渡金属位点周围的大量重排，四面体过渡态是能垒的原因。我们对键长和角度畸变的分析强调，在低钠水平下，剪切变形在触发 P 到 O 的滑移中起关键作用。基于这些见解，我们的结构畸变指标提供了一个简单且计算效率高的描述符，用于评估这些层状氧化物的结构完整性，从而能够设计出具有更高稳定性和更长寿命的 NIBs。
