STEM-EELS Spectrum Imaging of an Aerosol-Deposited NASICON-Type LATP Solid Electrolyte and LCO Cathode Interface

Abstract

All-solid-state batteries (ASSBs) are promising candidates for application as next-generation high-power supply and storage devices in electric vehicles. ASSBs offer excellent safety and a high energy density; however, the high interfacial resistance between the positive electrode and solid electrolyte due to solid−solid contact reactions at elevated temperatures limits their applications. To address these issues, the effect of thermal annealing on the interfacial structure between a sodium super ionic conductor (NASICON)-type Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) solid electrolyte and a LiCoO 2 (LCO) cathode in an ASSB fabricated by aerosol deposition was investigated experimentally. Specifically, spectrum imaging was conducted by combining scanning transmission electron microscopy and electron energy loss spectroscopy. Metastable degraded low-density transition layers were formed between LATP and LCO in the as-deposited sample. A significant reduction in interfacial resistance was achieved after thermal annealing at 250−300 °C, which was mainly attributed to structural recovery in this temperature range. However, thermal annealing at 400 °C resulted in increased interfacial resistance due to the formation of a Co 3 O 4 -like spinel blocking layer at the LATP/LCO interface. These findings provided valuable insights into the electronic properties of the ASSB composite under investigation and were consistent with theoretical predictions of Li and O transfer between the layers due to thermal annealing.

Co-sintering process of LiCoO2 cathodes and NASICON-type LATP solid electrolytes studied by X-ray diffraction and X-ray absorption near edge structure

“…[12][13][14][15] On the other hand, the poor plasticity of oxide-based solid electrolytes requires co-sintering at a relatively high temperature to construct a highly ion-conducting interface with electrode materials. [16][17][18][19] Small-sized oxide-based ASSLIBs constructed by a similar manufacturing process to multi-layered ceramic condensers are already commercialized for IoT devices such as smartphones, sensors and other portable devices. However, the sintering of the reactive substances often results in undesired side reactions.…”

“…However, the sintering of the reactive substances often results in undesired side reactions. [19][20][21][22][23][24] For example, a highly ion-conducting solid electrolyte, LATP and a high-capacity cathode material, LCO which is practically used in conventional liquid LIBs, fatefully react with each other to produce completely different species instead of forming a well-defined interface. 1,23 Although a few experimental results on the co-sintering products of LCO and LATP studied by XRD have been reported, [25][26][27] the main purpose of these previous reports was not the clarification of the reaction mechanism but fabrication of ASSLIBs.…”

“…However, the sintering of the reactive substances often results in undesired side reactions. 19–24 For example, a highly ion-conducting solid electrolyte, LATP and a high-capacity cathode material, LCO which is practically used in conventional liquid LIBs, fatefully react with each other to produce completely different species instead of forming a well-defined interface. 1,23…”

Fundamentals of the Cathode‐Electrolyte Interface in All‐solid‐state Lithium Batteries

“…Advanced deposition techniques are effective means of preparing various thin film materials and have also been successfully applied in the preparation of thin-film SEs and solid-state batteries, including chemical vapor deposition (CVD), [83] pulsed laser deposition (PLD), [84,85] magnetron sputtering, [86,87] aerosol deposition [88] and atomic layer deposition (ALD). [89,90] It also takes advantages in constructing nanoscale conformal interfaces, which is preferential for decreasing interfacial resistance and local polarization.…”

Effect of Low Environmental Pressure on Sintering Behavior of NASICON-Type Li1.3Al0.3Ti1.7(PO4)3 Solid Electrolytes: An In Situ ESEM Study

“…Recently, developing suitable solid-state electrolytes for solid-state batteries has been an important task because these electrolytes are safer and support high-energy electrodes. Therefore, all-solid-state batteries can better enable many applications, including in the automotive, electronic, aeronautic, and photovoltaic sectors. , The NASICON-structured solid electrolyte Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) is recognized to be one of the promising electrolytes due to their relatively high ionic grain conductivity, low toxicity, and good electrochemical stability while being easy to process and inexpensive. ,− Similar to most solid-state electrolytes, LATP can be processed via solid-state sintering . Typically, pre-sintered materials are prepared by mixing powders and compacting them into a pellet to form the green compact, which is then sintered.…”