The Detrimental Effects of Carbon Additives in Li₁₀GeP₂S₁₂-Based Solid-State Batteries

Abstract

All-solid-state batteries (SSBs) have recently attracted much attention due to their potential application in electric vehicles. One key issue that is central to improve the function of SSBs is to gain a better understanding of the interfaces between the material components toward enhancing the electrochemical performance. In this work, the interfacial properties of a carbon-containing cathode composite, employing LiGePS as the solid electrolyte, are investigated. A large interfacial charge-transfer resistance builds up upon the inclusion of carbon in the composite, which is detrimental to the resulting cycle life. Analysis by X-ray photoelectron spectroscopy reveals that carbon facilitates faster electrochemical decomposition of the thiophosphate solid electrolyte at the cathode/solid electrolyte interface-by transferring the low chemical potential of lithium in the charged state deeper into the solid electrolyte and extending the decomposition region. The occurring accumulation of highly oxidized sulfur species at the interface is likely responsible for the large interfacial resistances and aggravated capacity fading observed.

Manipulating Interfacial Nanostructure to Achieve High‐Performance All‐Solid‐State Lithium‐Ion Batteries

“…The sources of the data are listed in Table S2 (Supporting Information). It is apparent that the electrochemical performance of the dual shell structured LGPS@LNO@LCO overtakes previous results, especially the power density 6a,8a,21…”

“…In S 2p spectra (Figure A), S of LGPS is highly oxidized to SS or CoS x in comparison with S spectra of pristine LGPS. In addition, sulfite and sulfate species were also detected, which is also caused by the oxidization of LGPS by LCO during the charge‐discharge process . Interestingly, the intensity of oxidization peaks is reduced with the inner LNO shell (Figure A, bottom), suggesting the inner shell LNO can alleviate the oxidization of LCO during the charge–discharge process.…”

“…The low coulombic efficiency and significant polarization indicate serious interfacial reactions during the initial charging process. In addition, the slope at the very beginning of the charge curve is an indicator of a lithium‐deficient SCL between LCO and LGPS . The one‐shell LNO@LCO exhibits an initial discharge capacity of 92.2 mAh g −1 with the coulombic efficiency of 89.1%.…”

Facile Synthesis toward the Optimal Structure-Conductivity Characteristics of the Argyrodite Li6PS5Cl Solid-State Electrolyte

“…As shown in Figure 6b,d, the changes in Coulombic efficiency for both all-solid-state batteries suggest that side reactions occur during the cycling of both cells, which may be associated with the decomposition of the solid electrolyte in both the cathode mixture and the solid electrolyte layer. 30 Previous research has reported that the decomposition of the solid electrolyte leads to the formation of products at the interface which can be expected to retard the Li + mobility and lead to a large interfacial charge transfer resistance during cycling. 30−32 XPS data has shown that Li 6 PS 5 Cl has an electrochemical redox activity in the positive electrode, which can be partially oxidized into LiCl, P 2 S 5 , and polysulfides Li 2 S n upon charge.…”

“…30 Previous research has reported that the decomposition of the solid electrolyte leads to the formation of products at the interface which can be expected to retard the Li + mobility and lead to a large interfacial charge transfer resistance during cycling. 30−32 XPS data has shown that Li 6 PS 5 Cl has an electrochemical redox activity in the positive electrode, which can be partially oxidized into LiCl, P 2 S 5 , and polysulfides Li 2 S n upon charge. 31 The introduction of LiI in the cathode mixture may work as a protective layer separating particles of the Li 2 S active material and the solid electrolyte, reducing the redox reaction, potentially explaining the better cycling performance of the 80Li 2 S–20LiI/Li 6 PS 5 Cl/In all-solid-state battery.…”