Abstract
All-solid-state batteries are intensively investigated, although their performance is not yet satisfactory for large-scale applications. In this context, the combination of Li10GeP2S12 solid electrolyte and LiNi1-x-yCoxMnyO2 positive electrode active materials is considered promising despite the yet unsatisfactory battery performance induced by the thermodynamically unstable electrode|electrolyte interface. Here, we report electrochemical and spectrometric studies to monitor the interface evolution during cycling and understand the reactivity and degradation kinetics. We found that the Wagner-type model for diffusion-controlled reactions describes the degradation kinetics very well, suggesting that electronic transport limits the growth of the degradation layer formed at the electrode|electrolyte interface. Furthermore, we demonstrate that the rate of interfacial degradation increases with the state of charge and the presence of two oxidation mechanisms at medium (3.7 V vs. Li+/Li < E < 4.2 V vs. Li+/Li) and high (E ≥ 4.2 V vs. Li+/Li) potentials. A high state of charge (>80%) triggers the structural instability and oxygen release at the positive electrode and leads to more severe degradation.
Highlights
All-solid-state batteries are intensively investigated, their performance is not yet satisfactory for large-scale applications
To study the degradation at the LGPS|NCM622 interface, cells were rested at open-circuit voltage (VOC) for ~20 h after being charged up to a pre-defined voltage
Three semicircles in the high-frequency (~200 kHz), mid-frequency (~500 Hz), and low-frequency (~4 Hz) regions are mainly attributed to ionic transport in the composite cathode, the solid electrolytes (SEs)| cathode active materials (CAMs) interface, and the anode (In/InLi) |SE interface, respectively
Summary
All-solid-state batteries are intensively investigated, their performance is not yet satisfactory for large-scale applications In this context, the combination of Li10GeP2S12 solid electrolyte and LiNi1-x-yCoxMnyO2 positive electrode active materials is considered promising despite the yet unsatisfactory battery performance induced by the thermodynamically unstable electrode|electrolyte interface. The energy densities of lithiumion batteries with non-aqueous liquid electrolytes can still be improved, safety issues due to the flammable electrolyte and the hope for the safe use of the lithium metal anode drive the development of solid-state batteries (SSBs). Besides the issues with dendrite formation at the lithium metal anode, the interfacial degradation of SEs and cathode active materials (CAMs) currently limits the electrochemical performance of SSBs6–12. SEs with very high ionic conductivities in the order of 10−2 S cm−1 are required for the construction of the cathode composite with sufficient specific energy and rate capability[14]. Tphffieffi experimentally observed interfacial decomposition shows a t dependence for diffusion control and is in good agreement with theoretical predictions[17], which provides a deeper understanding of the stability of the anode|SE interface
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