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首页> 外文期刊>Advanced energy materials >On the Capacity Losses Seen for Optimized Nano-Si Composite Electrodes in Li-Metal Half-Cells
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On the Capacity Losses Seen for Optimized Nano-Si Composite Electrodes in Li-Metal Half-Cells

机译：关于锂金属半电池中优化的纳米硅复合电极的容量损失

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摘要

While the use of silicon-based electrodes can increase the capacity of Li-ion batteries considerably, their application is associated with significant capacity losses. In this work, the influences of solid electrolyte interphase (SEI) formation, volume expansion, and lithium trapping are evaluated for two different electrochemical cycling schemes using lithium-metal half-cells containing silicon nanoparticle-based composite electrodes. Lithium trapping, caused by incomplete delithiation, is demonstrated to be the main reason for the capacity loss while SEI formation and dissolution affect the accumulated capacity loss due to a decreased coulombic efficiency. The capacity losses can be explained by the increasing lithium concentration in the electrode causing a decreasing lithiation potential and the lithiation cut-off limit being reached faster. A lithium-to-silicon atomic ratio of 3.28 is found for a silicon electrode after 650 cycles using 1200 mAhg(-1) capacity limited cycling. The results further show that the lithiation step is the capacity-limiting step and that the capacity losses can be minimized by increasing the efficiency of the delithiation step via the inclusion of constant voltage delithiation steps. Lithium trapping due to incomplete delithiation consequently constitutes a very important capacity loss phenomenon for silicon composite electrodes.
机译：尽管使用硅基电极可以显着增加锂离子电池的容量，但其应用却会带来很大的容量损失。在这项工作中，使用包含硅纳米粒子的复合电极的锂金属半电池，针对两种不同的电化学循环方案，评估了固体电解质中间相（SEI）形成，体积膨胀和锂捕获的影响。锂的捕集是由不完全的脱锂引起的，这被证明是容量损失的主要原因，而SEI的形成和溶解会由于库仑效率降低而影响累积的容量损失。容量损失可以通过电极中锂浓度的升高导致锂化电位降低以及锂化截止极限更快地得到解释。使用1200 mAhg（-1）容量受限循环，经过650次循环后，硅电极的锂硅原子比为3.28。结果还表明，锂化步骤是容量限制步骤，并且通过包括恒定电压去锂化步骤来提高去锂化步骤的效率，可以使容量损失最小化。因此，由于不完全脱锂而引起的锂俘获构成硅复合电极非常重要的容量损失现象。

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