Synchrotron XPS studies of illuminated and annealed flash evaporated a-Ge2S3 films

271

239

All-solid-state batteries (ASSBs) show great potential for providing high power and energy densities with enhanced battery safety. While new solid electrolytes (SEs) have been developed with high enough ionic conductivities, SSBs with long operational life are still rarely reported. Therefore, on the way to high-performance and long-life ASSBs, a better understanding of the complex degradation mechanisms, occurring at the electrode/electrolyte interfaces is pivotal. While the lithium metal/solid electrolyte interface is receiving considerable attention due to the quest for high energy density, the interface between the active material and solid electrolyte particles within the composite cathode is arguably the most difficult to solve and study. In this work, multiple characterization methods are combined to better understand the processes that occur at the LiCoO cathode and the LiGePS solid electrolyte interface. Indium and LiTiO are used as anode materials to avoid the instability problems associated with Li-metal anodes. Capacity fading and increased impedances are observed during long-term cycling. Postmortem analysis with scanning transmission electron microscopy, electron energy loss spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy show that electrochemically driven mechanical failure and degradation at the cathode/solid electrolyte interface contribute to the increase in internal resistance and the resulting capacity fading. These results suggest that the development of electrochemically more stable SEs and the engineering of cathode/SE interfaces are crucial for achieving reliable SSB performance.

Section: ■ Results and Discussionmentioning

confidence: 53%

Section: Resultsmentioning

confidence: 84%

See 1 more Smart Citation

Degradation Mechanisms at the Li₁₀GeP₂S₁₂/LiCoO₂ Cathode Interface in an All-Solid-State Lithium-Ion Battery

Zhang

Richter

Culver

et al. 2018

271

239

“…Given that these species cannot be resolved by XPS, the precise origin of the new oxidized sulfur signals (A and B) are purely speculative at the moment. The signals may be due to LGPS decomposition products like germanium sulfides, − or to the terminal sulfur groups of Li 2 S n , to P–S–(S−) n , like polysulfide species with different chain lengths as well as possible disordered species containing −P–S–P– (−Ge–S–P– or −Ge–S–Ge−) bonds. , Furthermore, it is also likely that cobalt sulfides have formed at the LCO/LPGS interface, as the formation of Co–S species is thermodynamically favored. , Signals well above 165 eV can be assigned to oxygen-bonded sulfur and are indicative of the participation of oxygen from the active material in the decomposition reactions. This is further supported by changes in the Ge 3d and P 2p signals.…”

Section: Resultsmentioning

confidence: 99%

“…For the cathode containing 5.7 wt % C65, an additional component at a binding energy of 134.5 eV (D) is present, suggesting the presence of phosphate species . Similar results were obtained for the Ge 3d region: two new components were required for fitting the spectra of both cycled samples, whereas the signal at 31.5 eV (E) may be due to germanium sulfide and the signal at 32.4 eV (F) is likely due to oxide species (e.g., GeO 2 ) …”

Section: Resultsmentioning

confidence: 99%

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

Zhang

Leichtweiß

Culver

et al. 2017

287

284

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.

Distinguishing the Effects of the Space-Charge Layer and Interfacial Side Reactions on Li₁₀GeP₂S₁₂-Based All-Solid-State Batteries with Stoichiometric-Controlled LiCoO₂

Geng

et al. 2022

All-solid-state lithium batteries (ASSLBs) with high volumetric energy density and enhanced safety are considered one of the most promising next-generation batteries. Elucidating the capacity-fading mechanism caused by the space-charge layer (SCL) and the interfacial side reaction (ISR) is crucial for the future development of high-energy-density ASSLBs with a longer cycle life. Here, a systematic study to probe the electrochemical performance of Li 10 GeP 2 S 12 -based ASSLBs with stoichiometric-controlled Li x CoO 2 was performed with the aid of density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS), focused ion beam-field emission scanning electron microscopy (FIB-SEM), and solid-state nuclear magnetic resonance (NMR) spectroscopy. We discovered that the overstoichiometric Li 1.042 CoO 2 shows a high capacity at first cycle with the smallest overpotential, but the capacity gradually decreases, which is ascribed to the weak SCL effect and strong interfacial side reactions. On the contrary, the lithiumdeficient Li 0.945 CoO 2 achieves the best cycling stability with a very low capacity associated with the strongest SCL effect and weak interfacial side reactions. The SCL effect is indeed coupled with ISR, which eventually leads to capacity fading in long-term operation. We believe that the new insights gained from this work will accelerate the future development of LiCoO 2 /LGPS-based ASSLBs with both a mitigated SCL effect and a longer cycle life.