Staging phase transitions in LixCoO2
Staging phase transitions in LixCoO2
复制标题
DOI：
10.1149/1.1519850
复制
发表时间：
2002-12-01
影响因子：
3.9
通讯作者：
Dahn, JR
中科院分区：
文献类型：
--
作者：
Chen, ZH;Lu, ZH;Dahn, JR
最近，人们越来越关注将LiCoO 2充电到4.2V以上的电位以增加其商业用途的比容量。与低于4.2 V的LixCoO 2的情况不同，高于4.2 V的LixCoO（2）的电化学和结构并不完全清楚。在本研究中，在Li/L（i）xCoO（2）电池的电压曲线中观察到在4.55和4.63 V处的两个可逆平台，然后通过原位X射线衍射（XRD）对其进行研究。在LixCoO 2中在4.6V下形成的中间相（x = 0.12）被确定为第二相，即锂仅占据CoO 2-夹层之间的每隔一个空间。该相的结构是使用Li0.12CoO2的非原位XRD图案的Rietveld精修来确定的。我们发现，相邻的CoO 2三明治堆叠AA过渡金属排列，如果它们之间没有Li原子（如在O 1-CoO 2）和AB排列，如果它们之间有Li原子（如在O3-LixCoO 2）。这导致六层单元电池。我们发现的结构与Ceder小组预测的第二阶段相的结构一致，他们称之为H1-3。(C)2002年电化学学会。
Recently, there has been more and more interest in charging LiCoO2 to potentials above 4.2 V to increase its specific capacity for commercial use. Unlike the situation for LixCoO2 below 4.2 V, the electrochemistry and structure of LixCoO(2) above 4.2 V is not completely clear. In this study, two reversible plateaus at 4.55 and 4.63 V were observed in the voltage profile of Li/L(i)xCoO(2) cells, which were then studied by in situ X-ray diffraction (XRD). The intermediate phase, formed at 4.6 V with x = 0.12 in LixCoO2, was determined to be a stage two phase, that is with lithium occupying only every second space between CoO2 "sandwiches.'' The structure of this phase was determined using Rietveld refinement of an ex situ XRD pattern of Li0.12CoO2. We find that adjacent CoO2 sandwiches are stacked with aa transition metal alignments if there are no Li atoms between them (as in O1-CoO2) and with ab alignments if there are Li atoms between them (as in O3-LixCoO2). This leads to a six-layer unit cell. The structure we find agrees well with that predicted by Ceder's group for the stage two phase that they call H1-3. (C) 2002 The Electrochemical Society.