A novel carbonate free electrolyte, 1 M lithium difluoro(oxalato) borate (LiDFOB) in 1:1 gamma-butyrolactone (GBL)/methyl butyrate (MB), has been compared to a standard electrolyte, 1 M LiPF 6 in 1:1:1 EC/DMC/DEC, and a 1 M LiDFOB in 1:1:1 EC/DMC/DEC electrolyte. The conductivity of 1 M LiDFOB in GBL/MB is higher at low temperature, but slightly lower at higher temperature compared to the standard electrolyte. The 1 M LiDFOB in GBL/MB electrolyte has comparable cycling performance to the standard electrolyte, and better cycling performance than the 1 M LiDFOB in EC/DMC/DEC electrolyte. The reversible cycling performance suggests that the LiDFOB in GBL/MB electrolyte forms a stable anode solid electrolyte interface (SEI) in the presence of GBL. Ex-situ surface analysis of the extracted electrodes has been conducted via a combination of XPS, FTIR-ATR and SEM which suggests that the stable anode SEI results is primarily composed of reduction products of LiDFOB. The widespread implementation of electric vehicles (EVs) requires further improvements in lithium ion batteries.1-3 Some of the biggest challenges for lithium ion batteries in EVs are cost, low temperature performance and battery lifetime.2,3 Improvements in the electrolyte can assist in the resolution of each of these problems.1,4,5 Most commercial electrolytes are composed of LiPF 6 in a mixture of carbonate solvents.5 However, the high cost and poor thermal and hydrolytic stability of LiPF 6 is problematic for the electrolyte.6-8 In addition, ethylene carbonate (EC) is typically a required component of the electrolyte due to the role of EC in the formation of the solid electrolyte interphase (SEI) on the anode. 5,9-14 Since EC is a solid at room temperature, electrolytes containing EC frequently have poor performance at low temperature.15 Despite the shortcomings of LiPF 6 / EC based electrolytes, these formulations have proven very difficult to replace. While there have been significant efforts to develop novel electrolytes with superior performance to LiPF 6 in carbonates, there has been limited success. The development of novel solvent systems has been more limited and frequently targeted toward specific problems such as high voltage cathodes, salt solubility, or reactivity issues. [16][17][18][19][20][21] The development of novel salts has encountered problems related to salt solubility and corrosion of the aluminum current collector on the cathode. 21,22 One of the more interesting and promising alternative salts is lithium difluoro(oxalato) borate (LiDFOB). 1,4,23,24 LiDFOB is promising due to good solubility, thermal stability, passivation of the aluminum current collector, stable SEI formation, and potentially lower cost. While there have been a limited number of investigations of LiD-FOB as the conducting salt in the electrolyte, 4,16,25 there have been several reports of the use of LiDFOB and the related salts lithium bis(oxalato) borate (LiBOB) and lithium tetrafluoro(oxalato) phosphate (LiTFOP) as additives to LiPF 6 based electrolytes to form...
Understanding the interfacial reactions between sodium metal (SM) and the solid-state electrolyte (SSE) Na3PS4 (NPS) and its oxygen-doped derivatives, Na3PS4–x O x (NPSO), will help develop a strategy to stabilize the SM–SSE interface. Previous reports have demonstrated that NPS is a promising SSE due to its high ionic conductivity, but it is known to be unstable against SM. This chemical instability and hence reactivity are critical problems in most sulfide materials, and in this work, we report one of the very first detailed studies of the reaction between SM and NPSO SSEs. It was discovered that the reaction between SM and Na3PS4 is facilitated simply by contact and is not driven by a forced potential difference. A combination of powder X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy was used to identify the main reaction product as the reduced phosphide Na3P. Additionally, the reaction is significantly slowed but not completely eliminated by the addition of oxygen in NPSO oxy-sulfide SSEs. We find that NPS is unstable because the SM-NPS reaction layer product is heavily exfoliated, allowing further sodium reaction between the newly created sheets. This degradation mechanism results in further chemical reaction until either the metallic sodium or NPS SSE is fully consumed, whichever is the limiting reagent in the reaction. As oxygen is added, x > 0, the SSE surface remains dense and is slower to react, making it more difficult for the SM to react through the NPSO SSE. The central finding here is that in our work, we find that the x = 1 Na3PS3O SSE remains unreacted with SM over periods of months at room temperature and so far appears to be one of the very few sulfide-based SSEs that is stable against SM and as such is a highly promising SSE for all solid-state sodium batteries (ASSSBs).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.