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[Display omitted] Rechargeable lithium (Li) metal batteries (LMBs) with ultrahigh-nickel (Ni) layered oxide cathodes offer a great opportunity for applications in electrical vehicles. However, increasing Ni content inherently arouses a tradeoff between specific capacity and electrochemical cyclability due to the aggressive side reactions with electrolyte contributed by the highly reactive Ni species. Here, a protective and stable cathode/electrolyte interphase featuring enriched and evenly-distributed LiF is in situ formed on ultrahigh-Ni cathode LiNi 0.94 Co 0.06 O 2 (NC) with an advanced ether-based localized high-concentration electrolyte (LHCE), which concurrently shows good compatibility with Li metal anode. Subsequently, the NC cathode can deliver high capacity retentions of 81.4% after 500 cycles at 25 °C and 91.6% after 100 cycles at 60 °C in the voltage range of 2.8–4.4 V in Li||NC cells at 1C cycling rate (1.5 mA cm−2). Meanwhile, the conductive electrode/electrolyte interphases formed in LHCE enable a high reversible capacity of about 209 mAh g−1 at 3C charging rate. This work provides an effective approach and important insight from the perspective of in situ ultrahigh-Ni cathode/electrolyte interphase protection for high energy–density, long-lasting LMBs. [ABSTRACT FROM AUTHOR]

Highlights • X-ray photoelectron spectroscopy can provide atomistic and microscopic view of chemical speciation and distribution at complexelectrode-electrolyte interfaces. • Identifying the reactant and products of decomposition reaction can help evaluate the longevity of electrolyte and subsequent life cycle of battery. • Novelin situ XPS can provide real time view of electrode-electrolyte interphase formation and help us correlate the battery failure mechanisms. Abstract Technological development requires reliable power sources where energy storage devices are emerging as a critical component. Wide range of energy storage devices, Redox-flow batteries (RFB), Lithium ion based batteries (LIB), and Lithium-sulfur (LSB) batteries are being developed for various applications ranging from grid-scale level storage to mobile electronics. Material complexities associated with these energy storage devices with unique electrochemistry are formidable challenge which needs to be address for transformative progress in this field. X-ray photoelectron spectroscopy (XPS) - a powerful surface analysis tool - has been widely used to study these energy storage materials because of its ability to identify, quantify and image the chemical distribution of redox active species. However, accessing the deeply buried solid-electrolyte interfaces (which dictates the performance of energy storage devices) has been a challenge in XPS usage. Herein we report our recent efforts to utilize the XPS to gain deep insight about these interfaces under realistic conditions with varying electrochemistry involving RFB, LIB and LSB. [ABSTRACT FROM AUTHOR]

Reformulation of electrolyte systems and improvement of separator wettability are vital to electrochemical performances of rechargeable lithium (Li) metal batteries, especially for suppressing Li dendrites. In this work we report a bifunctional electrolyte additive that improves separator wettability and suppresses Li dendrite growth in Li metal batteries. A triblock polyether (Pluronic P123) is added as an additive into a commonly used carbonate-based electrolyte. It is found that addition of 0.2–1% (by weight) P123 into the electrolyte can effectively enhance the wettability of polyethylene separator. More importantly, the adsorption of P123 on Li metal surface can act as an artificial solid electrolyte interphase layer and suppress the growth of Li dendrites. A smooth and dendrite-free Li morphology can be achieved in the electrolyte with 0.2% P123. The Li||Li symmetric cells with the 0.2% P123-containing electrolyte exhibit a relatively long cycling stability at high current densities of 1.0 and 3.0 mA cm −2 . [ABSTRACT FROM AUTHOR]

Rechargeable lithium (Li) metal batteries with conventional LiPF 6 -carbonate electrolytes have been reported to fail quickly at charging current densities of about 1.0 mA cm −2 and above. In this work, we demonstrate the rapid charging capability of Li||LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) cells can be enabled by a dual-salt electrolyte of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(oxalato)borate (LiBOB) in a carbonate solvent mixture. The cells using the LiTFSI-LiBOB dual-salt electrolyte significantly outperform those using the LiPF 6 electrolyte at high charging current densities. At the charging current density of 1.50 mA cm −2 , the Li||NCA cells with the dual-salt electrolyte can still deliver a discharge capacity of 131 mAh g −1 and a capacity retention of 80% after 100 cycles. The Li||NCA cells with the LiPF 6 electrolyte start to show fast capacity fading after the 30th cycle and only exhibit a low capacity of 25 mAh g −1 and a low retention of 15% after 100 cycles. The reasons for the good chargeability and cycling stability of the cells using the LiTFSI-LiBOB dual-salt electrolyte can be attributed to the good film-formation ability of the electrolyte on the Li metal anode and the highly conductive nature of the sulfur-rich interphase layer. [ABSTRACT FROM AUTHOR]

The practical application of lithium (Li) metal anode in rechargeable Li batteries is hindered by both the growth of Li dendrites and the low Coulombic efficiency (CE) during repeated charge/discharge cycles. Recently, we have discovered that CsPF 6 as an electrolyte additive can significantly suppress Li dendrite growth and lead to highly compacted and well aligned Li nanorod structures during Li deposition on copper substrates. In this paper, the effect of CsPF 6 additive on the performance of rechargeable Li metal batteries with lithium iron phosphate (LFP) cathode is further studied. Li|LFP coin cells with CsPF 6 additive in electrolytes show well protected Li anode surface, decreased resistance, enhanced rate capability and extended cycling stability. In Li|LFP cells, the electrolyte with CsPF 6 additive shows excellent long-term cycling stability (at least 500 cycles) at a charge current density of 0.5 mA cm −2 without internal short circuit. At high charge current densities, the effect of CsPF 6 additive becomes less significant. Future work needs to be done to protect Li metal anode, especially at high charge current densities and for long cycle life. [ABSTRACT FROM AUTHOR]

In this work, localized high concentration electrolytes (LHCEs) based on tetramethylene sulfone (TMS) were designed. Similar to LHCEs based on other solvents, TMS-based LHCEs can achieve excellent compatibility with high energy density lithium-ion batteries (LIBs) when combined with a proper additive. The unique solvation structure of LHCEs facilitates the synergetic decomposition of anion, solvent and additive in the solid electrolyte interphase (SEI) formation. Proper combinations of the three constituents of the solvation sheaths in LHCEs can promote the formation of highly effective SEI on graphite negative electrode. The absence of LiPF 6 in LHCEs also suppresses the degradation of positive electrode materials in LIBs. The superior interphasial properties of LHCEs are the key to realizing the long lifespan of high energy density LIBs. • Tetramethylene sulfone (TMS) based LHCEs with different additives were studied. • Additive-free TMS-LHCE outperforms conventional electrolyte in Gr.||Ni-rich LIBs. • Proper additives in TMS-LHCE can further boost performance of Gr.||Ni-rich LIBs. • Electrolyte solvation structure/content govern interphase and battery performance. [ABSTRACT FROM AUTHOR]