Li nucleation on the graphite anode under potential control in Li-ion batteries
Li nucleation on the graphite anode under potential control in Li-ion batteries
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DOI：
10.1039/d2ta02420a
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发表时间：
2022-05-10
影响因子：
11.9
通讯作者：
Skylaris, Chris-Kriton
中科院分区：
文献类型：
--
作者：
Bhandari, Arihant;Peng, Chao;Skylaris, Chris-Kriton
锂离子电池在电动汽车中的应用需要提高安全性、延长寿命和高充电速率。锂离子电池最常用的嵌入阳极材料之一石墨易受锂成核的影响，这是一种与嵌入过程竞争的副反应，并导致电池可逆容量的损失、老化和短路。在这项研究中，我们部署了一个组合的巨正则大尺度电子密度泛函理论（DFT）和泊松-玻尔兹曼电解质理论研究锂团簇的成核和生长的石墨阳极在其周围的电解质环境的存在下，在不同的外加电压相对于锂金属参比电极。我们发现低于该电压的成核能变成负的（对应于Li成核成为能量有利的），“零成核能的电位”（U-PZN）。我们观察到一个独特的最小值在绘图的U-PZN作为一个函数的大小的有核集群。当施加在石墨电极上的电压低于U-PZN的最小值时，成核团簇开始在石墨电极上无束缚地生长。发现团簇生长（U-PCG）的电势在未锂化石墨的周期基面上为-0.12V，在锂化石墨上为-0.08V。锯齿形边缘终止的相应电势在未锂化石墨上为-0.06V，在锂化石墨上为-0.04V。因此，与周期性基面相比，成核和簇生长在石墨电极的Z字形边缘终端上是有利的，并且与未锂化石墨相比，成核和簇生长在锂化石墨上是有利的。我们发现，周围的环境起着重要的作用，成核是更容易发生在电解质环境比从真空中的计算预测。我们观察到在电解质中用巨正则系综密度泛函方法得到的势与实验数据接近。该研究对电池中金属枝晶的成核、生长和控制具有深远的意义。
Application of Li-ion batteries in electric vehicles requires improved safety, increased lifetime and high charging rates. One of the most commonly used intercalation anode material for Li-ion batteries, graphite, is vulnerable to Li nucleation, a side reaction which competes with the intercalation process and leads to loss of reversible capacity of the battery, ageing and short-circuits. In this study, we deploy a combined grand canonical large-scale electronic density-functional theory (DFT) and Poisson-Boltzmann electrolyte theory to study the nucleation and growth of Li clusters on the graphite anode in the presence of its surrounding electrolyte environment at different applied voltages with respect to the Li metal reference electrode. We find the voltage below which the nucleation energy becomes negative (corresponding to Li nucleation becoming energetically favourable), the 'potential of zero nucleation energy' (U-PZN). We observe a distinct minimum in the plots of U-PZN as a function of the size of nucleated clusters. When the applied voltage on the graphite electrode is below the minimum value of U-PZN, the nucleated clusters start growing unbounded on graphite electrode. This potential for cluster growth (U-PCG) is found to be -0.12 V on the periodic basal plane of unlithiated graphite and -0.08 V on lithiated graphite. The corresponding potential for the zigzag edge termination is -0.06 V on unlithiated graphite and -0.04 V on lithiated graphite. Thus, the nucleation and cluster growth is favored on the zigzag edge termination of the graphite electrode as compared to the periodic basal plane and on the lithiated graphite as compared to the unlithiated graphite. We find that the surrounding environment plays a significant role and that nucleation is more likely to occur in electrolyte environment than that predicted from calculations in vacuum. We observe that the potentials obtained with grand canonical ensemble DFT method in electrolyte are close to experimentally available data. The study has profound implications for the nucleation, growth and control of metal dendrites in a battery cell.