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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Lithium diffusion pathways and vacancy formation in the Pmmn-Li_(1-x)FeO2 electrode material
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Lithium diffusion pathways and vacancy formation in the Pmmn-Li_(1-x)FeO2 electrode material

机译：Pmmn-Li_（1-x）FeO2电极材料中锂的扩散途径和空位形成

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Models for Li~+ ion mobility were developed and investigated in the 'corrugated layer' orthorhombic phase of Li_(1-x)FeO2, an attractive possible electrode material for reversible lithium ion batteries. The ground-state crystal energy was computed by first-principles DFT (Density-Functional-Theory) methods, based on the use of the hybrid B3LYP functional with localized Gaussian-type basis sets. Appropriate supercells were devised as needed, with full least-energy structure optimization. In the defect-free case (x = 0), ion diffusion was found to take place cooperatively inside a fraction of active lithium layers separated by inert ones, so as to reduce lattice strain; intermediate bottleneck states of Li are either in tetrahedral (energy barrier ΔE_a = 0.410 eV) or linear (ΔE_a = 0.468 eV) coordination. For the Li_(0.75)FeO2 deintercalated material a number of low energy vacancy configurations were considered, investigating also the vacancy influence on electron density of states and atomic charge distribution. The most favourable ion transport mechanisms (ΔE_a = 0.292 and 0.304 eV) imply a linear Li bottleneck state, with all lithium layers active and a quite small lattice strain. Accordingly, in the defective material the predicted ionic conductivity at room temperature rises from 10~(-5)-10~(-6) (LiFeO2) to 4 x 10~(-4) ohm~(-1) cm~(-1) (Li_(0.75)FeO2).
机译：锂离子迁移率模型的开发和研究是在Li_（1-x）FeO2的“波纹层”正交相中进行的，Li_（1-x）FeO2是一种有吸引力的可逆锂离子电池电极材料。基于第一原理DFT（密度泛函理论）方法，基于具有局部高斯型基集的杂化B3LYP函数，计算了基态晶体能量。根据需要设计了适当的超级电池，并进行了最小能耗的结构优化。在无缺陷的情况下（x = 0），发现离子扩散在一部分被惰性层隔开的活性锂层内协同发生，从而降低了晶格应变; Li的中间瓶颈状态为四面体（能垒ΔE_a= 0.410 eV）或线性（ΔE_a= 0.468 eV）配位。对于Li_（0.75）FeO2脱嵌材料，考虑了许多低能空位构型，还研究了空位对态电子密度和原子电荷分布的影响。最有利的离子传输机制（ΔE_a= 0.292和0.304 eV）表示线性的Li瓶颈态，所有锂层均处于活性状态，晶格应变很小。因此，在有缺陷的材料中，室温下的预测离子电导率从10〜（-5）-10〜（-6）（LiFeO2）上升到4 x 10〜（-4）ohm〜（-1）cm〜（- 1）（Li_（0.75）FeO2）。

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