Material strategies for high energy layered cathodes with improved stability for Li-ion batteries: investigation of doping strategies and solid-state concepts using a combined in- situ/operando approach

点击翻译按钮获取中文摘要

Li-ion batteries (LIB) have been of great interest for a variety of applications such as mobile energy storage devices, electromobility (electrical and hybrid vehicles), and stationary energy storage. To obtain high energy densities as required for future applications, further materials and technology development is required, particularly regarding positive electrodes (cathodes). Above all, the class of two-component Li and Mn-rich 'layered-layered' xLi2MnO3(1-x)LiMO2 materials (M = Ni, Mn, Co) is very promising for application in high energy cathodes, providing capacities of >200 mAh/g in the potential range of 2.0 V - 4.6 V. However, presently this type of material suffers from voltage decay and capacity loss.This proposal aims to obtain a comprehensive understanding of the degradation of high energy cathode materials with a focus on layered-layered materials, and to propose materials and materials strategies for electrodes with improved stability. As part of the work, we will test and combine different material strategies, such as use of Li-containing surface layers and solid electrolytes, doping with highly charged cations, as well as doping with halide ions. By means of a combined investigation using a multi-method in situ/operando analysis approach on model and composite electrodes, we intent to clarify the role of lattice doping and coating for structural stability and surface layer formation. Specifically, we propose to combine electronic structure analysis, analysis of crystal structure and analysis of local order and inhomogeneity to obtain insights into irreversible defect formation and coupled phase transformation and degradation phenomena. Special attention is thereby given to the electrode-electrolyte interface formation and to electrode reactivity.In its fundamental orientation, our proposal also addresses key issues for other mixed conducting materials or electrode materials in general, such as materials used in sensors or fuel cells.