A New Approach to Develop Safe All‐Inorganic Monolithic Li‐Ion Batteries

Abstract

Li-ion batteries based on liquid electrolytes have conquered the electronics marketplace, however, cost and safety are the overriding parameters limiting their widespread use in electric vehicles (EVs) or hybrid EVs (HEVs). [ 1 ] Ideally, Li-ion batteries should rely on the use of dry polymer or inorganic electrolytes, as they would then be free of solvent leakages. The former are still under development after many years of research and the latter currently fall short in terms of high impedance issues associated with poorly defi ned interfaces. [ 2,3 ] Here, we report the use of spark plasma sintering (SPS) as a novel assembly technique for preparing all-inorganic, monolithic Li-ion batteries; these batteries have cycling characteristics approaching their liquid Li-ion counterparts, while being safer and faster to make. This achievement is grounded in the structural quality of the electrode-electrolyte interfaces, as probed by impedance spectroscopy and electron microscopy, which enables both good charge transfer and mechanical integrity upon cycling. This work provides a new path worth pursuing for designing Li-ion batteries capable of operating safely over a wide temperature range.The all-solid-state battery consists of a stack of 3 components (composite positive electrode/electrolyte/composite negative electrode) ( Figure 1 a), which should be assembled in such a way that intimate interfaces can be generated both between grains of the materials in each of the three parts as well as between the components themselves. To achieve these objectives, the materials should be selected principally using electrochemical criteria to insure high performances, but also taking into account additional criteria such as chemical compatibility suitable for "high" temperature sintering process.The composite electrodes should possess a high content of electrochemically active material (AM) for the energy density and electronic and ionic conductor additives to ensure efficient and homogeneous transfer of electrons and ions through the electrode volume. The composite electrodes should also display good mechanical behavior to allow easy handling and to insure cell lifetime, but also, more importantly, to permit volume variation upon Li insertion/extraction. It has been shown that oxide materials such as LiCoO 2 or LiMn 0.5 Ni 0.5 O 2 react at temperatures between 300 ° C and 500 ° C in presence of a Nasicon-type solid electrolyte with the formation of an ionblocking interface. [ 2 ] Another approach is to use ductile glasses or glass ceramics, such as those based on sulfi des, to assemble batteries by cold compaction. [ 4 ] However, beyond the intrinsic instability of sulfi des under air and water, which increases the process cost, cold-compacted systems present strong interface limitations implying to apply pressure on the battery to insure its cycle life. Finally, the stored energy, which is linked to the thickness of the composite electrodes, is limited to less than a few hundred μ Ah.cm − 2 .Based on all the previously listed co...

Study of the Mechanisms of Internal Short Circuit in a Li/Li Cell by Synchrotron X-ray Phase Contrast Tomography

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