On the Lithiation Mechanism of Amorphous Silicon Electrodes in Li-Ion Batteries
On the Lithiation Mechanism of Amorphous Silicon Electrodes in Li-Ion Batteries
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DOI：
10.1021/acs.jpcc.9b06011
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发表时间：
2019-09-12
影响因子：
3.7
通讯作者：
Schmidt, Harald
中科院分区：
文献类型：
--
作者：
Uxa, Daniel;Jerliu, Bujar;Schmidt, Harald
非晶硅是一种用于先进锂离子电池的高容量负极材料。我们结合操作中子反射法和异位二次离子质谱法，研究了电化学锂化和脱锂过程中锂嵌入和脱锂的机制。结果表明，在第一次循环以及锂化和脱锂过程中的后续循环中存在异质锂化机制，其中高度锂化相渗透硅电极。在第一个锂化半循环期间，发生两步过程，这对于脱锂和更高的循环来说是不存在的。第一步，贫锂相渗透硅电极，产生约 10% 的最大容量。然后，在第二步中，富锂相移动到电极中，导致在较慢的过程中完成锂化。不同的相被仅几纳米的相对尖锐的界面分开。脱锂后，遍布整个电极的贫锂相仍然以不可逆捕获的锂形式存在。
Amorphous silicon is a high-capacity negative electrode material for use in advanced lithium-ion batteries. We investigated the mechanism of Li incorporation into and removal from this material during electrochemical lithiation and delithiation using a combination of in operando neutron reflectometry and ex situ secondary ion mass spectrometry. The results indicate that a heterogeneous lithiation mechanism is present for the first cycle and also for subsequent cycles during lithiation and delithiation, where a highly lithiated phase penetrates the silicon electrode. During the first lithiation half-cycle, a two-step process takes place, which is not present for delithiation and higher cycles. In the first step, a Li-poor phase penetrates the silicon electrode leading to about 10% of maximum capacity. Afterward, during the second step, a Li-rich phase moves into the electrode leading to complete lithiation in a slower process. The different phases are separated by a relatively sharp interface of only several nanometers. The Li-poor phase extended over the entire electrode is still present after delithiation in the form of irreversibly trapped Li.