Novel Solid Electrolytes for Li-Ion Batteries: A Perspective from Electron Microscopy Studies

Abstract

Solid electrolytes can simultaneously overcome two of the most formidable challenges of Li-ion batteries: the severe safety issues and insufficient energy densities. However, before they can be implemented in actual batteries, the ionic conductivity needs to be improved and the interface with electrodes must be optimized. The prerequisite for addressing these issues is a thorough understanding of the material's behavior at the microscopic and/or the atomic level. (Scanning) transmission electron microscopy is a powerful tool for this purpose, as it can reach an ultrahigh spatial resolution. Here, we review recent electron microscopy investigations on the ion transport behavior in solid electrolytes and their interfaces. Specifically, three aspects will be highlighted: the influence of grain interior atomic configuration on ionic conductivity, the contribution of grain boundaries, and the behavior of solid electrolyte/electrode interfaces. Based on this, the perspectives for future research will be discussed.

Origin of High Interfacial Resistance in Solid‐State Batteries: LLTO/LCO Half‐Cells**

“…Spectrums from 4 points (marked in Figure 5(c)) are showed in Figure 5(e). La N 4,5 Peaks were only observed in the bright grain spectrums (B1,B2), while the peak position is most likely shifted due to the oxidation state of La [49] . This observation accords well with the TEM‐EDS results.…”

“…La N 4,5 Peaks were only observed in the bright grain spectrums (B1,B2), while the peak position is most likely shifted due to the oxidation state of La. [49] This observation accords well with the TEM-EDS results. Li K-edges were observed in phase α at about 62 eV, while one measurement of the phase β (D2) showed a Li K-edge at about 58 eV.…”

Energetics and cathode voltages of LiMPO4 olivines ( M=Fe , Mn) from extended Hubbard functionals

“…Despite steady progress in recent years and the introduction of new types of rechargeable batteries (e.g., K-, Na-, Mg-ion [1][2][3][4], or Li-air ones [5,6]) for dedicated purposes, many microscopic aspects of their behavior still need full clarification, with space for improvement and optimization [7][8][9][10][11]; significant research activity is taking place, in fact, on all battery components (anodes, cathodes, electrolytes) [12][13][14]. The constant efforts to improve performance have stimulated a vigorous search for better materials, especially for electrolytes (in the attempt to design solid-state media able to sustain safely higher voltages than their liquid counterparts, and comparable ionic currents) [15][16][17][18][19][20][21][22] and for cathodes (in order to identify more conductive, safer systems with higher energy density, higher voltage) [10,[23][24][25][26][27][28][29][30][31][32][33][34]. Cathode materials are, in fact, particularly important for the improvement of rechargeable Li-ion batteries as these components are not only the source of power, but also embody some of the most critical bottlenecks towards the improvement of current technologies including weight, safety, energy density, and overall power.…”

Mechanistic understanding and strategies to design interfaces of solid electrolytes: insights gained from transmission electron microscopy

“…This limitation is partially due to the small number of operando or in situ studies of solid-solid interfaces at the atomic scale. [24][25][26] Developing a precise understanding of ion transport behavior at solid-solid interfaces is challenging. Since solid-solid interfaces are often spatially confined and embedded, limited characterization techniques can clearly reveal the structural and chemical nature of interfaces at an adequate spatial resolution.…”