Reactions of the Li2MnO3 Cathode in an All-Solid-State Thin-Film Battery during Cycling
Reactions of the Li2MnO3 Cathode in an All-Solid-State Thin-Film Battery during Cycling
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DOI：
10.1021/acsami.0c18030
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发表时间：
2021-02-04
影响因子：
9.5
通讯作者：
Kanno, Ryoji
中科院分区：
文献类型：
--
作者：
Hikima, Kazuhiro;Hinuma, Yoyo;Kanno, Ryoji
我们评估了在全固态电池中作为具有（001）取向的外延膜沉积的正极材料Li 2 MnO 3的结构变化。我们开发了一种原位表面X射线衍射（XRD）技术，其中X射线以0.1度的非常低的掠射角入射。波长为0.82518 A的X射线穿透Li 2 MnO 3阴极上的类似于2 μ m厚的非晶Li 3 PO 4固态电解质和类似于1 μ m厚的金属Li阳极。实验揭示了一个结构变化的高容量（激活）阶段，进行逐步和连续的循环。激活阶段几乎没有显示出任何容量衰减。第一性原理计算表明，活化相具有O 1堆积，这是通过首先脱锂到具有O3堆积和四面体Li的中间相来实现的。该中间相在[001]方向上具有低的Li迁移势垒路径，但是进一步的脱锂导致能量上有利的和不可逆的向O 1相的转变。我们提出了一种机制的结构变化与循环：充电到一个高电压在一个足够低的锂浓度通常会引起不可逆的过渡到一个阶段，不利于循环，可能，但不一定，伴随着溶解的Mn和/或O的释放到电解质中，而一个逐渐的不可逆过渡到一个激活的阶段发生在一个类似的锂浓度在一个较低的电压。
We evaluated the structural change of the cathode material Li2MnO3 that was deposited as an epitaxial film with an (001) orientation in an all-solid-state battery. We developed an in situ surface X-ray diffraction (XRD) technique, where X-rays are incident at a very low grazing angle of 0.1 degrees. An X-ray with wavelength of 0.82518 A penetrated an similar to 2 mu m-thick amorphous Li3PO4 solid-state electrolyte and similar to 1 mu m-thick metal Li anode on the Li2MnO3 cathode. Experiments revealed a structural change to a high-capacity (activated) phase that proceeded gradually and continuously with cycling. The activated phase barely showed any capacity fading. First-principles calculations suggested that the activated phase has O1 stacking, which is attained by first delithiating to an intermediate phase with O3 stacking and tetrahedral Li. This intermediate phase has a low Li migration barrier path in the [001] direction, but further delithiation causes an energetically favorable and irreversible transition to the O1 phase. We propose a mechanism of structural change with cycling: charging to a high voltage at a sufficiently low Li concentration typically induces irreversible transition to a phase detrimental to cycling that could, but not necessarily, be accompanied by the dissolution of Mn and/or the release of O into the electrolyte, while a gradual irreversible transition to an activated phase happens at a similar Li concentration under a lower voltage.