Imaging the Phase Transformation in Single Particles of the Lithium Titanate Anode for Lithium-Ion Batteries
Imaging the Phase Transformation in Single Particles of the Lithium Titanate Anode for Lithium-Ion Batteries
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DOI：
10.1021/acsaem.0c02010
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发表时间：
2021-01-04
影响因子：
6.4
通讯作者：
Robinson, Ian K.
中科院分区：
文献类型：
--
作者：
Assefa, Tadesse A.;Suzana, Ana F.;Robinson, Ian K.
在放电和充电循环期间，钛酸锂（LTO）阳极材料中的锂吸收和释放是锂离子电池（LIB）的基本过程之一，在微观水平上仍未完全理解。在放电循环期间，LTO在立方晶格内经历Li 4 Ti 5 O 12和Li 7 Ti 5 O 12状态之间的相变。为了揭示微观机制的细节，有必要跟踪在不同的放电/充电状态下的操作条件下的相变序列。在这里，我们使用原位布拉格相干衍射成像（BCDI）和原位X射线衍射（XRD）实验，分别检查单个LTO颗粒和散装电池模拟物内的锂插入诱导材料相变。来自（111）布拉格峰的BCDI分析示出了两相转变，其表现为在放电区域的中间发生的单个LTO纳米颗粒内的明显的图像相位调制，然后朝向放电循环的结束而消退。我们观察到最大的相位变化在两相阶段，表明在放电过程中形成的相域的大小为200 nm。我们还观察到单个LTO纳米颗粒在（400）布拉格峰测量处的晶格收缩>0.2%，大于相应的块体材料。我们在单粒子水平上观察到的这种相变对理解阳极和阴极LIBs材料中相变的微观/介观尺度图像具有影响。
Lithium uptake and release in lithium titanate (LTO) anode materials during a discharge and charge cycle is one of the fundamental processes of a lithium-ion battery (LIB), still not fully understood at the microscopic level. During the discharge cycle, LTO undergoes a phase transformation between Li4Ti5O12 and Li7Ti5O12 states within a cubic crystal lattice. To reveal the details of the microscopic mechanism, it is necessary to track the sequence of phase transformations at different discharge/charge states under operating conditions. Here, we use in situ Bragg coherent diffraction imaging (BCDI) and in situ X-ray diffraction (XRD) experiments to examine the lithium insertion-induced materials phase transformation within a single LTO particle and a bulk battery analogue, respectively. BCDI analysis from (111) Bragg peak shows the two-phase transformation manifesting as a distinct image phase modulation within a single LTO nanoparticle occurring in the middle of the discharge region then subsiding toward the end of the discharge cycle. We observe the biggest phase variation at the two-phase stage, indicating the formation of phase domains of 200 nm in size during the discharge process. We also observe a lattice contraction of >0.2% in a single LTO nanoparticle at the (400) Bragg peak measurement, larger than that in the corresponding bulk material. Our observation of this phase transformation at a single-particle level has implications for the understanding of the microscopic/mesoscale picture of the phase transformation in anode and cathode LIBs materials.