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Recharging battery‐powered electric vehicles (EVs) in a similar timeframe as those used for refueling gas‐powered internal combustion vehicles is highly desirable for rapid penetration of the EV market. It is well known that the electrolyte in a battery plays a critical role in fast‐charging capability of the battery because it determines the rate of ion transport together with its derived electrode/electrolyte interphases on both cathode and anode of the battery. In this study, the effects of contents of salt, coordinating solvent, and noncoordinating diluent on salt dissociation degree and electrolyte ionic conductivity are investigated, and a controlled solvation structure electrolyte is developed to improve the lithium ion mobility and conductivity in the electrolyte and to enhance the kinetics and stability of the electrode/electrolyte interphases in the battery. This electrolyte enables fast‐charging capability of high energy density lithium‐ion batteries (LIBs) at up to 5 C rate (12‐min charging), which significantly outperforms the state‐of‐the‐art electrolyte. The controlled solvation structure sheds light on the future electrolyte design for fast‐charging LIBs. [ABSTRACT FROM AUTHOR]

Lithium metal batteries (LMBs) are one of the most promising candidates for next‐generation high‐energy‐density rechargeable batteries. Solid electrolyte interphase (SEI) on Li metal anodes plays a significant role in influencing the Li deposition morphology and the cycle life of LMBs. However, a thorough understanding on the mechanisms of SEI formation and evolution is still inadequate. In this review, the progress in understanding structures, properties, and influencing factors of SEI, as well as efficient strategies of tailoring SEI are focused upon. First, the compositions, models, and recent progress in characterizing atomic structures of SEI are summarized. Second, the properties of SEI, including electronic conduction, ionic conduction, stability, and mechanical properties are elucidated. Structures and properties of SEI are greatly affected by multiple factors, thus interactions between these factors and SEI are systematically discussed. Correlations of SEI with Li deposition morphology, rate capability, and cycle life are further summarized. Moreover, efficient strategies of tailoring SEI with desired properties, including in situ SEI and ex situ SEI, are also reviewed. Finally, future directions, including in‐operando techniques, multi‐modality approaches for characterization of SEI, and artificial intelligence assisted understanding of correlations between electrolyte components and SEI properties are proposed. [ABSTRACT FROM AUTHOR]

To enable next‐generation high‐power, high‐energy‐density lithium (Li) metal batteries (LMBs), an electrolyte possessing both high Li Coulombic efficiency (CE) at a high rate and good anodic stability on cathodes is critical. Acetonitrile (AN) is a well‐known organic solvent for high anodic stability and high ionic conductivity, yet its application in LMBs is limited due to its poor compatibility with Li metal anodes even at high salt concentration conditions. Here, a highly concentrated AN‐based electrolyte is developed with a vinylene carbonate (VC) additive to suppress Li+ depletion at high current densities. Addition of VC to the AN‐based electrolyte leads to the formation of a polycarbonate‐based solid electrolyte interphase, which minimizes Li corrosion and leads to a very high Li CE of up to 99.2% at a current density of 0.2 mA cm‐2. Using such an electrolyte, fast charging of Li||NMC333 cells is realized at a high current density of 3.6 mA cm‐2, and stable cycling of Li||NMC622 cells with a high cathode loading of 4 mAh cm‐2 is also demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: The instability of lithium (Li) metal anodes due to dendritic growth and low Coulombic efficiency (CE) hinders the practical application of high‐energy‐density Li metal batteries. Here, the systematic studies of improving the stability of Li metal anodes and the electrochemical performance of Li metal batteries through the addition of combinational additives and the optimization of solvent compositions in dual‐salt/carbonate electrolytes are reported. A dendrite‐free and high CE of 98.1% for Li metal anode is achieved. The well‐protected Li metal anode and the excellent cyclability and rate capability of the 4‐V Li metal batteries are obtained. This is attributed to the formation of a robust, denser, more polymeric, and higher ionic conductive surface film on the Li metal anode via the electrochemical reductive decompositions of the electrolyte components and the ring‐opening polymerization of additives and cyclic carbonate solvents. The key findings of this work indicate that the optimization of solvent compositions and the manipulation of additives are facile and effective ways to enhance the performances of Li metal batteries. [ABSTRACT FROM AUTHOR]

Abstract: Lithium (Li) metal is an ideal anode material for high energy density batteries. However, the low Coulombic efficiency (CE) and the formation of dendrites during repeated plating and stripping processes have hindered its applications in rechargeable Li metal batteries. The accurate measurement of Li CE is a critical factor to predict the cycle life of Li metal batteries, but the measurement of Li CE is affected by various factors that often lead to conflicting values reported in the literature. Here, several parameters that affect the measurement of Li CE are investigated and a more accurate method of determining Li CE is proposed. It is also found that the capacity used for cycling greatly affects the stabilization cycles and the average CE. A higher cycling capacity leads to faster stabilization of Li anode and a higher average CE. With a proper operating protocol, the average Li CE can be increased from 99.0% to 99.5% at a high capacity of 6 mA h cm−2 (which is suitable for practical applications) when a high‐concentration ether‐based electrolyte is used. [ABSTRACT FROM AUTHOR]

Abstract: The charging process of Li2O2-based air electrodes in Li–O2 batteries with organic carbonate electrolytes was investigated using in situ gas chromatography/mass spectroscopy (GC/MS) to analyze gas evolution. A mixture of Li2O2/Fe3O4/Super P carbon/polyvinylidene fluoride (PVDF) was used as the starting air electrode material, and 1-M lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) in carbonate-based solvents was used as the electrolyte. We found that Li2O2 was actively reactive to 1-methyl-2-pyrrolidinone and PVDF that were used to prepare the electrode. During the first charging (up to 4.6V), O2 was the main component in the gases released. The amount of O2 measured by GC/MS was consistent with the amount of Li2O2 that decomposed during the electrochemical process as measured by the charge capacity, which is indicative of the good chargeability of Li2O2. However, after the cell was discharged to 2.0V in an O2 atmosphere and then recharged to ∼4.6V, CO2 was dominant in the released gases. Further analysis of the discharged air electrodes by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy indicated that lithium-containing carbonate species (lithium alkyl carbonates and/or Li2CO3) were the main discharge products. Therefore, compatible electrolytes and electrodes, as well as the electrode-preparation procedures, need to be developed for rechargeable Li-air batteries for long term operation. [Copyright &y& Elsevier]

Due to the limited oxidation stability (<4 V) of ether oxygen in its polymer structure, polyethylene oxide (PEO)‐based polymer electrolytes are not compatible with high‐voltage (>4 V) cathodes, thus hinder further increases in the energy density of lithium (Li) metal batteries (LMBs). Here, a new type of polymer‐in‐"quasi‐ionic liquid" electrolyte is designed, which reduces the electron density on ethereal oxygens in PEO and ether solvent molecules, induces the formation of stable interfacial layers on both surfaces of the LiNi1/3Mn1/3Co1/3O2 (NMC) cathode and the Li metal anode in Li||NMC batteries, and results in a capacity retention of 88.4%, 86.7%, and 79.2% after 300 cycles with a charge cutoff voltage of 4.2, 4.3, and 4.4 V for the LMBs, respectively. Therefore, the use of "quasi‐ionic liquids" is a promising approach to design new polymer electrolytes for high‐voltage and high‐specific‐energy LMBs. [ABSTRACT FROM AUTHOR]

Abstract: In this work, Li/air batteries based on nonaqueous electrolytes were investigated in ambient conditions (with an oxygen partial pressure of 0.21atm and relative humidity of ∼20%). A heat-sealable polymer membrane was used as both an oxygen-diffusion membrane and as a moisture barrier for Li/air batteries. The membrane also can minimize the evaporation of the electrolyte from the batteries. Li/air batteries with this membrane can operate in ambient conditions for more than one month with a specific energy of 362Whkg−1, based on the total weight of the battery including its packaging. Among various carbon sources used in this work, Li/air batteries using Ketjenblack (KB) carbon-based air electrodes exhibited the highest specific energy. However, KB-based air electrodes expanded significantly and absorbed much more electrolyte than electrodes made from other carbon sources. The weight distribution of a typical Li/air battery using the KB-based air electrode was dominated by the electrolyte (∼70%). Lithium metal anodes and KB-carbon account for only 5.12% and 5.78% of the battery weight, respectively. We also found that only ∼20% of the mesopore volume of the air electrode was occupied by reaction products after discharge. To further improve the specific energy of the Li/air batteries, the microstructure of the carbon electrode needs to be further improved to absorb much less electrolyte while still holding significant amounts of reaction products. [Copyright &y& Elsevier]

[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]

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]