LiNi(0.5)Mn(1.5)O4 high-voltage cathode coated with Li4Ti5O12: a hard X-ray photoelectron spectroscopy (HAXPES) study.
LiNi(0.5)Mn(1.5)O4 high-voltage cathode coated with Li4Ti5O12: a hard X-ray photoelectron spectroscopy (HAXPES) study.
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DOI：
10.1039/c5cp03837e
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发表时间：
2015-11
期刊：
影响因子：
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通讯作者：
M. Sachs;M. Gellert;Min Chen;Hans-Jörg Drescher;S. Kachel;Han Zhou;Malte Zugermeier;M. Gorgoi;B. Roling;J. M. Gottfried
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文献类型：
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作者：
M. Sachs;M. Gellert;Min Chen;Hans-Jörg Drescher;S. Kachel;Han Zhou;Malte Zugermeier;M. Gorgoi;B. Roling;J. M. Gottfried
将Li4Ti5O12 （LTO）薄膜作为缓冲层涂覆在LiNi0.5Mn1.5O4 （LNMO）高压阴极上，在电池电解液中循环后，利用同步辐射硬x射线光电子能谱（HAXPES）对LTO薄膜进行了研究。通过在2 keV和6 keV之间调节光子能量，我们获得了探测深度在6 nm到20 nm之间的涂层材料的非破坏性深度分布。发现该涂层表面覆盖着由电解液分解形成的几纳米薄的表面层。这一层主要由有机聚合物以及金属氟化物和氟磷酸盐组成。发现Li4Ti5O12涂层对表面层的尺寸和稳定性有积极的影响。涂层本身是由Li(I)、Ti（IV）、Ni（II）和Mn（IV）氧化物组成的均匀混合物，极有可能采用尖晶石结构，形成两种尖晶石LiNi0.5Mn1.5O4和Li4Ti5O12的固溶体，Li、Mn、Ni和Ti阳离子混合在尖晶石八面体位点上。在制备阴极的过程中，Ni和Mn离子扩散到Li4Ti5O12晶格中。Li4Ti5O12与开放d壳层离子Ni(2+) （d(8)）和Mn(4+) （d(3)）的掺杂应该会显著提高涂层的电子导电性，正如之前的研究发现的那样。Ti 2p， Ni 2p和Mn 2p核心能级的复杂信号结构提供了对过渡金属离子化学性质的深入了解。
A Li4Ti5O12 (LTO) film was coated as buffer layer onto a LiNi0.5Mn1.5O4 (LNMO) high-voltage cathode, and after cycling of the cathode in a battery electrolyte, the LTO film was investigated by means of synchrotron radiation based hard X-ray photoelectron spectroscopy (HAXPES). By tuning the photon energy between 2 keV and 6 keV, we obtained non-destructive depth profiles of the coating material with probing depths ranging from 6 nm to 20 nm. The coating was found to be covered by a few nanometers thin surface layer resulting from electrolyte decomposition. This layer consisted predominantly of organic polymers as well as metal fluorides and fluorophosphates. A positive influence of the Li4Ti5O12 coating with regard to the size and stability of the surface layer was found. The coating itself consisted of a uniform mixture of Li(I), Ti(IV), Ni(II) and Mn(IV) oxides that most likely adopted a spinel structure by forming a solid solution of the two spinels LiNi0.5Mn1.5O4 and Li4Ti5O12 with Li, Mn, Ni and Ti cations mixing on the spinel octahedral sites. The diffusion of Ni and Mn ions into the Li4Ti5O12 lattice occurred during the heat treatment when preparing the cathode. The doping of Li4Ti5O12 with the open d-shell ions Ni(2+) (d(8)) and Mn(4+) (d(3)) should increase the electronic conductivity of the coating significantly, as was found in previous studies. The complex signal structure of the Ti 2p, Ni 2p and Mn 2p core levels provides insight into the chemical nature of the transition metal ions.