Conditioning of all solid state Lithium Ion Batteries with LiMPO4 (M=Co, Ni) thin film cathodes

正极材料在决定锂离子电池的能量密度、安全性和寿命周期中起着至关重要的作用。它的热力学稳定性取决于本征电压极限，而本征电压极限是由相关材料中阴离子的固有氧化极限定义的。整个电池单元的外部稳定性还受到电解液的氧化还原电位和阴极/电解液界面的化学兼容性的影响。功率能力取决于Li和/或电子通过块状阴极材料和跨越相界面的阴极/电解液的转移速率。因此，要开发稳定的高功率、高密度电池，必须解决以下关键问题：a)高压荷电状态下电池的热力学稳定性和化学兼容性；b)锂离子在相间和相界的高迁移速率；c)电极中的高电子导电性和电解液界面的堵塞。由于涉及添加剂的设置的复杂性，这些因素在经典电池结构中的具体作用很难阐明。本课题的目标是新型高压固态电池的制备和研究。我们将重点放在橄榄石型结构材料LiMPO4(M=Fe，Co，Ni)上，其中通过用Co(4.8V)和Ni(&gt；5V)取代Fe来增加电压窗口。应解决以下科学问题：a)LiCoPO4和LiNiPO4橄榄石型正极材料在脱除的情况下热力学稳定吗？它们是否适用于高电压应用，直到未知的本征电压极限？B)LiCoPO4和LiNiPO4与氟乙烯碳酸盐等典型电解液在化学上是否相容，橄榄石/电解液界面在5V左右是否稳定？3)LiCoPO4和LiNiPO4与固体电解质(如LiPON)在化学上是否相容？薄膜正极材料及其界面将在超高电压条件下制备，并将主要用电子能谱原位研究其电子性质。通过将这种新的表面科学方法应用于离子导体，我们将解决高压橄榄石的内在和外在稳定性范围，并研究避免腐蚀副反应的可能途径。

The cathode material plays a key role in the determination of energy density, safety and life cycle of Lithium Ion Batteries (LIB). Its thermodynamic stability depends on the intrinsic voltage limit which is defined by the inherent oxidation limit of the anions within the relevant material. The extrinsic stability of the whole battery cell is additionally influenced by the redox potential of the electrolyte and by the chemical compatibility of the cathode/electrolyte interface. Power capability depends on the Li+ and/or electron transfer rates through the bulk cathode material and across the phase boundary cathode/electrolyte. Thus, to develop a stable high power and high density battery, the following key issues have to be solved: a) thermodynamic stability and chemical compatibility of the battery cell operated at a high voltage charged state; b) high migration rate of Li+ ions through the phases and across the phase boundaries; c) high electronic conductivity in the electrode and a blocking electrolyte interface. The specific role of these factors can hardly be clarified in classical battery structures due to the complexity of the set-up involving additives. The aim of our project is the preparation and investigation of novel high voltage solid state batteries. We focus on the olivine type structure material as LiMPO4 (M=Fe, Co, Ni) in which the voltage window is increased by substitution of Fe by Co (4.8 V) and Ni (> 5 V. The following scientific problems shall be addressed: a) Are LiCoPO4 and LiNiPO4 olivine-type cathode materials thermodynamically stable under delithiation and are they suitable for high voltage application up to a still unknown intrinsic voltage limit? b) Are LiCoPO4 and LiNiPO4 chemically compatible with typical electrolytes as fluoroethylene carbonate and is the olivine/electrolyte interface stable at voltage around 5 V? c) Are LiCoPO4 and LiNiPO4 chemically compatible with solid electrolytes (as e. g. LIPON)?The film cathode materials and their interfaces will be prepared under UHV condition and their electronic properties will be studied in situ mostly by using electron spectroscopy. With such a novel surface science approach applied at ion conductors we will address the intrinsic and extrinsic stability range of high voltage Olivines and investigate possible routes to avoid corrosive side reactions.