Phosphorene oxides as a promising cathode material for sealed non-aqueous Li-oxygen batteries
Phosphorene oxides as a promising cathode material for sealed non-aqueous Li-oxygen batteries
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磷烯氧化物作为密封非水锂氧电池的有前景的正极材料
DOI：
10.1039/c8ta01218k
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发表时间：
2018
影响因子：
11.9
通讯作者：
Wang Lin-Wang
中科院分区：
文献类型：
--
作者：
Li Yan;Ma Fei;Wang Lin-Wang
将第一性原理方法与分子动力学模拟和隐式溶剂模型相结合，评价了一种新型的二维材料--P4O_1、P_4O_2、P_4O_3和P_4O_4四种表面氧化态的氧化膦(POS)作为密封锂氧电池的潜在正极材料。该系统可以密封，因为与开放式锂空气电池不同，它不需要从空气中获取氧气。我们的模拟表明：(1)通过形成最大数目的Li-O键，李灿被紧密地吸附在POS表面，结合能从−2.32 eV到−3.72 eV，∼0.9e从Li到O的电荷转移。(2)Li在POS上的扩散是强烈的各向异性，因为扶手椅方向的势垒比之字形方向的势垒高近两倍。随着氧化程度的增加，势垒急剧下降到0.2 eV，表明有很高的扩散率。(3)对于P4O4正极，热力学稳定、完全放电的产物的化学计量比为Li ： P ： O=1 ： 1 ： 1，比容量为570.56 mA h g−1，平均开路电压为2.55V，能量密度为1457W h kg−1。考虑溶剂效应可进一步提高能量密度。与低极性的1，2-二甲氧基乙烷(DME)相比，高极性的环状碳酸亚乙酯(EC)溶剂能带来更大的能量密度提高。(4)锂吸附后，POS内部发生了半导体到金属的转变，促进了PO电池的电输运。强锂吸附、高扩散率和良好的导电性使POS成为未来全密封锂氧电池的极佳候选者。
A new type of two-dimensional (2D) material, phosphorene oxides (POs) in four surface oxidation states (P4O1, P4O2, P4O3 and P4O4), is evaluated as a potential cathode for sealed Li–oxygen batteries by combining the first-principles method with molecular dynamics simulations and implicit solvent models. The system can be sealed because, unlike open Li–air batteries, there is no need to take oxygen from air. Our simulations reveal that: (1) by forming a maximum number of Li–O bonds, Li can be tightly chemisorbed on the surface of POs with a large binding energy ranging from −2.32 to −3.72 eV and a charge transfer of ∼0.9e from Li to O. (2) The diffusion of Li on POs is strongly anisotropic as the barrier along the armchair direction is nearly two times higher than that along the zigzag direction. The barrier dramatically decreases to 0.2 eV with increasing oxidation, indicating a high diffusivity. (3) For the P4O4 cathode, the thermodynamically stable, fully discharged product has a stoichiometry of Li : P : O = 1 : 1 : 1, achieving a specific capacity of 570.56 mA h g−1, an average open-circuit voltage of 2.55 V and an energy density of 1457 W h kg−1. The energy density can be further increased by considering solvent effects. More polar cyclic ethylene carbonate (EC) solvent brings about a larger energy density enhancement than less polar linear 1,2-dimethoxyethane (DME). (4) Semiconductor-to-metal transition occurs within POs after Li adsorption, facilitating the electrical transport in PO-based batteries. A combination of strong Li adsorption, high diffusivity, and good conductivity makes POs great candidates for future fully sealed Li–oxygen batteries.