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首页> 外文期刊>Advanced energy materials >Asymmetric Rate Behavior of Si Anodes for Lithium-Ion Batteries: Ultrafast De-Lithiation versus Sluggish Lithiation at High Current Densities
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Asymmetric Rate Behavior of Si Anodes for Lithium-Ion Batteries: Ultrafast De-Lithiation versus Sluggish Lithiation at High Current Densities

机译：锂离子电池硅阳极的不对称速率行为：高电流密度下超快速去锂与缓慢锂化

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摘要

The combined effect of lithium-ion diffusion, potential-concentration gradient, and stress plays a critical role in the rate capability and cycle life of Si-based anodes of lithium-ion batteries. In this work, Si nanofilm anodes are shown to exhibit an asymmetric rate performance: around 72% of the total available capacity can be delivered during de-lithiation under a high current density of 420 A g-1 (100C where C is the charge-rate) in 22 s; in striking contrast, only 1% capacity can be delivered during lithiation. A mathematical model of single-ion diffusion is established to elucidate the asymmetric rate performance, which can be mainly attributed to the potential-concentration profile associated with the active material and the ohmic voltage shift under high currents; the difference in chemical diffusion coefficients during lithiation and de-lithiation also plays a role. This clarifies that the charge and discharge rates of lithium-ion-battery electrodes should be evaluated separately due to the asymmetric effect in the electrochemical system.
机译：锂离子扩散，电势浓度梯度和应力的综合作用在锂离子电池硅基负极的倍率能力和循环寿命中起着至关重要的作用。在这项工作中，Si纳米膜阳极表现出不对称的速率性能：在去锂化期间，在420 A g-1的高电流密度（100C，其中C是电荷-率）在22秒内;与之形成鲜明对比的是，在锂化过程中只能提供1％的容量。建立了单离子扩散的数学模型以阐明不对称的速率性能，这主要归因于与活性材料相关的电势浓度分布以及高电流下的欧姆电压漂移；锂化和去锂化过程中化学扩散系数的差异也起作用。这表明，由于电化学系统中的不对称作用，应分别评估锂离子电池电极的充电和放电速率。

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