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The conventional electrolyte of 1 m lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in dimethyl sulfoxide (DMSO) is unstable against the Li metal anode and therefore cannot be used directly in practical Li-O2 batteries. Here, we demonstrate that a highly concentrated electrolyte based on LiTFSI in DMSO (with a molar ratio of 1:3) can greatly improve the stability of the Li metal anode against DMSO and significantly improve the cycling stability of Li-O2 batteries. This highly concentrated electrolyte contains no free DMSO solvent molecules, but only complexes of (TFSI−) aLi+(DMSO) b (where a + b = 4), and thus enhances their stability with Li metal anodes. In addition, such salt-solvent complexes have higher Gibbs activation energy barriers than the free DMSO solvent molecules, indicating improved stability of the electrolyte against the attack of superoxide radical anions. Therefore, the stability of this highly concentrated electrolyte at both Li metal anodes and carbon-based air electrodes has been greatly enhanced, resulting in improved cycling performance of Li-O2 batteries. The fundamental stability of the electrolyte in the absence of free-solvent against the chemical and electrochemical reactions can also be used to enhance the stability of other electrochemical systems. [ABSTRACT FROM AUTHOR]

The stability of electrolytes against highly reactive, reduced oxygen species is crucial for the development of rechargeable Li-O2 batteries. In this work, the effect of lithium salt concentration in 1,2-dimethoxyethane (DME)-based electrolytes on the cycling stability of Li-O2 batteries is investigated systematically. Cells with highly concentrated electrolyte demonstrate greatly enhanced cycling stability under both full discharge/charge (2.0-4.5 V vs Li/Li+) and the capacity-limited (at 1000 mAh g−1) conditions. These cells also exhibit much less reaction residue on the charged air-electrode surface and much less corrosion of the Li-metal anode. Density functional theory calculations are used to calculate molecular orbital energies of the electrolyte components and Gibbs activation energy barriers for the superoxide radical anion in the DME solvent and Li+-(DME) n solvates. In a highly concentrated electrolyte, all DME molecules are coordinated with salt cations, and the C-H bond scission of the DME molecule becomes more difficult. Therefore, the decomposition of the highly concentrated electrolyte can be mitigated, and both air cathodes and Li-metal anodes exhibit much better reversibility, resulting in improved cyclability of Li-O2 batteries. [ABSTRACT FROM AUTHOR]

Abstract: The effects of six types of aprotic organic solvents on the discharge performance and discharge products in Li-O2 batteries are systematically investigated. A large amount of Li2O2 is identified in the air electrodes discharged in glyme-based electrolytes, while only a small amount of Li2O2 is detected in the air electrodes discharged in the electrolytes of nitrile, ionic liquid, phosphate, and sulfoxide. Li2CO3 and LiF are also found as byproducts whose compositions are related to the solvents. Li2CO3 is produced from oxidation and decomposition of the solvent, not from the oxidation of the carbon-based air electrode, as revealed by using a 13C-labeled carbon electrode and the solid-state 13C-magic angle spinning nuclear magnetic resonance technique. LiF in the discharge products can be attributed to the attack of superoxide radical anions to the Teflon binder and/or the F-containing imide salt. The formation of these byproducts will significantly reduce the Coulombic efficiency and cycle life of the Li-air batteries. Among the studied solvents, dibutyl diglyme is the suitable solvent for Li-O2 batteries based on its overall properties. However, better electrolytes that can ensure the formation of Li2O2 but minimize other reaction products need to be further investigated for long cycling rechargeable Li-air batteries. [Copyright &y& Elsevier]

Abstract: It is well known that LATP (Li1+x+y Al x Ti2−x Si y P3−y O12) glass is a good lithium (Li)-ion conductor. However, the interaction between LATP glass and H+ ions in aqueous electrolytes (including the diffusion and surface adsorption of H+ ions) needs to be well understood before the long-term application of LATP glass in an aqueous electrolyte can be realized. In this work, we investigate H+-ion diffusion in LATP glass and their interactions with the glass surface using both experimental and modeling approaches. Our results indicate that the apparent H+-related current observed in the initial cyclic voltammetry scan should be attributed to the adsorption of H+ ions on the LATP glass rather than the bulk diffusion of H+ ions. Furthermore, density functional theory calculations indicate that the H+-ion diffusion energy barrier (3.21 eV) is much higher than that for Li+ ions (0.79 eV) and Na+ ions (0.79 eV) in a NASICON-type LiTi2(PO4)3 material. As a result, H+-ion conductivity in LATP glass is negligible at room temperature. However, significant surface corrosion was found after the LATP glass in a strong alkaline electrolyte. Therefore, to prevent LATP glass from corrosion, appropriate electrolytes must be developed for long-term operation of LATP in aqueous Li–air batteries. [Copyright &y& Elsevier]

Abstract: The Li–O2 chemistry in nonaqueous liquid carbonate electrolytes and the underlying reason for its limited reversibility was systematically investigated. X-ray diffraction data showed that regardless of discharge depth lithium alkylcarbonates (lithium propylenedicarbonate (LPDC), or lithium ethylenedicarbonate (LEDC), with other related derivatives) and lithium carbonate (Li2CO3) are constantly the main discharge products, while lithium peroxide (Li2O2) or lithium oxide (Li2O) is hardly detected. These lithium alkylcarbonates are generated from the reductive decomposition of the corresponding carbonate solvents initiated by the attack of superoxide radical anions. More significantly, in situ gas chromatography/mass spectroscopy analysis revealed that Li2CO3 and Li2O cannot be oxidized even when charged to 4.6V vs. Li/Li+, while LPDC, LEDC and Li2O2 are readily oxidized, with CO2 and CO released from LPDC and LEDC and O2 evolved from Li2O2. Therefore, the apparent reversibility of Li–O2 chemistry in an organic carbonate-based electrolyte is actually an unsustainable process that consists of (1) the formation of lithium alkylcarbonates through the reductive decomposition of carbonate solvents during discharging and (2) the subsequent oxidation of these same alkylcarbonates during charging. Therefore, a stable electrolyte that does not lead to an irreversible by-product formation during discharging and charging is necessary for truly rechargeable Li–O2 batteries. [Copyright &y& Elsevier]

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]

Aqueous solutions are generally assumed to be superior electrolytic conductors because of the unique dielectric and fluid properties of water. It can be shown that conductivities can be matched by liquid electrolytes that contain no solvent. These are proton transfer salts that are liquid at ambient temperature. The high conductivities are due to the high fluidity and ionicity rather than some sort of Grotthus mechanism, although in certain cases a mobile proton population may make a non-negligible contribution. The highest conductivities have been obtained when both cations and anions contain protons.

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]

Localized high‐concentration electrolytes (LHCEs) based on five different types of solvents were systematically studied and compared in lithium (Li)‐ion batteries (LIBs). The unique solvation structure of LHCEs promotes the participation of Li salt in forming solid electrolyte interphase (SEI) on graphite (Gr) anode, which enables solvents previously considered incompatible with Gr to achieve reversible lithiation/delithiation. However, the long cyclability of LIBs is still subject to the intrinsic properties of the solvent species in LHCEs. Such issue can be readily resolved by introducing a small amount of additive into LHCEs. The synergetic decompositions of Li salt, solvating solvent and additive yield effective SEIs and cathode electrolyte interphases (CEIs) in most of the studied LHCEs. This study reveals that both the structure and the composition of solvation sheaths in LHCEs have significant effect on SEI and CEI, and consequently, the cycle life of energetically dense LIBs. [ABSTRACT FROM AUTHOR]

Localized high‐concentration electrolytes (LHCEs) based on five different types of solvents were systematically studied and compared in lithium (Li)‐ion batteries (LIBs). The unique solvation structure of LHCEs promotes the participation of Li salt in forming solid electrolyte interphase (SEI) on graphite (Gr) anode, which enables solvents previously considered incompatible with Gr to achieve reversible lithiation/delithiation. However, the long cyclability of LIBs is still subject to the intrinsic properties of the solvent species in LHCEs. Such issue can be readily resolved by introducing a small amount of additive into LHCEs. The synergetic decompositions of Li salt, solvating solvent and additive yield effective SEIs and cathode electrolyte interphases (CEIs) in most of the studied LHCEs. This study reveals that both the structure and the composition of solvation sheaths in LHCEs have significant effect on SEI and CEI, and consequently, the cycle life of energetically dense LIBs. [ABSTRACT FROM AUTHOR]

It has been widely assumed that the flammability of the liquid electrolyte is one of the most influential factors that determine the safety of lithium‐ion batteries (LIBs). Following this consideration, a completely nonflammable electrolyte is designed and adopted for graphite||LiFePO4 (Gr||LFP) batteries. Contrary to the conventional understanding, the completely nonflammable electrolyte with phosphorus‐containing solvents exhibits inferior safety performance in commercial Gr||LFP batteries, in comparison to the flammable conventional LiPF6‐organocarbonate electrolyte. Mechanistic studies identify the exothermic reactions between the electrolyte (especially the salt LiFSI) and the charged electrodes as the "culprit" behind this counterintuitive phenomenon. The discovery emphasizes the importance of reducing the electrolyte reactivity when designing safe electrolytes, as well as the necessity of evaluating safety performance of electrolytes on a battery level. [ABSTRACT FROM AUTHOR]

In article number 1602605, a new approach to enhance the cycling stability of Li‐O2 batteries with dimethyl sulfoxide (DMSO) based electrolyte is developed by Wu Xu, Ji‐Guang Zhang, and co‐workers. It is found that the LiTFSI‐3DMSO electrolyte exhibits an optimal concentration in which only most stable TFSI−–Li+–(DMSO)3 complexes exist but Li+–(DMSO)4 solvates and free DMSO solvent molecules are absent. This electrolyte significantly enhances the stability of both Li metal anodes and carbon‐based airelectrode. The finding on the fundamental stability of the electrolyte in the absence of free‐solvent against the chemical and electrochemical reactions can also be used to enhance the stability of other electrochemical systems. [ABSTRACT FROM AUTHOR]

Suppressing lithium (Li) dendritegrowth is one of the most critical challenges for the developmentof Li metal batteries. Here, we report for the first time the growthof dendrite-free lithium films with a self-aligned and highly compactednanorod structure when the film was deposited in the electrolyte consistingof 1.0 M LiPF6in propylene carbonate with 0.05 M CsPF6as an additive. Evolution of both the surface and the cross-sectionalmorphologies of the Li films during repeated Li deposition/strippingprocesses were systematically investigated. It is found that the formationof the compact Li nanorod structure is preceded by a solid electrolyteinterphase (SEI) layer formed on the surface of the substrate. Electrochemicalanalysis indicates that an initial reduction process occurred at ∼2.05V vs Li/Li+before Li deposition is responsible for theformation of the initial SEI, while the X-ray photoelectron spectroscopyindicates that the presence of CsPF6additive can largelyenhance the formation of LiF in this initial SEI. Hence, the smoothLi deposition in Cs+-containing electrolyte is the resultof a synergistic effect of Cs+additive and preformed SEIlayer. A fundamental understanding on the composition, internal structure,and evolution of Li metal films may lead to new approaches to stabilizethe long-term cycling stability of Li metal and other metal anodesfor energy storage applications. [ABSTRACT FROM AUTHOR]

Despite being an effective flame retardant, trimethyl phosphate (TMPa) is generally considered as an unqualified solvent for fabricating electrolytes used in graphite (Gr)‐based lithium‐ion batteries as it readily leads to Gr exfoliation and cell failure. In this work, by adopting the unique solvation structure of localized high‐concentration electrolyte (LHCE) to TMPa and tuning the composition of the solvation sheaths via electrolyte additives, excellent electrochemical performance can be achieved with TMPa‐based electrolytes in Gr∥LiNi0.8Mn0.1Co0.1O2 cells. After 500 charge/discharge cycles within the voltage range of 2.5–4.4 V, the batteries containing the TMPa‐based LHCE with a proper additive can achieve a capacity retention of 85.4 %, being significantly higher than cells using a LiPF6‐organocarbonates baseline electrolyte (75.2 %). Meanwhile, due to the flame retarding effect of TMPa, TMPa‐based LHCEs exhibit significantly reduced flammability compared with the conventional LiPF6‐organocarbonates electrolyte. [ABSTRACT FROM AUTHOR]

Despite being an effective flame retardant, trimethyl phosphate (TMPa) is generally considered as an unqualified solvent for fabricating electrolytes used in graphite (Gr)‐based lithium‐ion batteries as it readily leads to Gr exfoliation and cell failure. In this work, by adopting the unique solvation structure of localized high‐concentration electrolyte (LHCE) to TMPa and tuning the composition of the solvation sheaths via electrolyte additives, excellent electrochemical performance can be achieved with TMPa‐based electrolytes in Gr∥LiNi0.8Mn0.1Co0.1O2 cells. After 500 charge/discharge cycles within the voltage range of 2.5–4.4 V, the batteries containing the TMPa‐based LHCE with a proper additive can achieve a capacity retention of 85.4 %, being significantly higher than cells using a LiPF6‐organocarbonates baseline electrolyte (75.2 %). Meanwhile, due to the flame retarding effect of TMPa, TMPa‐based LHCEs exhibit significantly reduced flammability compared with the conventional LiPF6‐organocarbonates electrolyte. [ABSTRACT FROM AUTHOR]

[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]

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]

A stable electrolyte is critical for practical application of lithium–oxygen batteries (LOBs). Although the ionic conductivity and electrochemical stability of the electrolytes have been extensively investigated before, their oxygen solubility, viscosity, volatility, and the stability against singlet oxygen (1O2) still need to be comprehensively investigated to provide a full picture of the electrolytes, especially for an open system such as LOBs. Herein, a systematic investigation is reported on the localized high‐concentration electrolytes (LHCEs) using different fluorinated diluents in comparison with those of conventional electrolytes. The physical properties and activation energies for reactions with singlet oxygen (1O2) of these electrolytes are calculated by density functional theory. The electrochemical performances of LOBs using these electrolytes are compared. This study reveals that the correlation between the stability of the electrolytes and their physical and electrochemical properties depends strongly on the diluents in LHCEs. Therefore, it shines light on the rational design of new electrolytes for LOBs. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report the electrochemical characteristics of a novel cathode material, Li2CoPO4F, prepared by solid-state reactions. The solid-state reaction mechanism involved in synthesizing the Li2CoPO4F also is analyzed in this paper. When cycled between 2.0V and 5.0V during cyclic voltammetry measurements, the Li2CoPO4F samples present one, fully reversible anodic reaction at 4.81V. When cycled between 2.0V and 5.5V, peaks occurring at 4.81V and 5.12V in the first anodic scan evolved to one broad oxidative, mound-like pattern in subsequent cycles. Correspondingly, the X-ray diffraction (XRD) pattern of the Li2CoPO4F electrode discharged from 5.5V to 2.0V is slightly different from the patterns exhibited by a fresh sample and the sample discharged from 5.0V to 2.0V. This difference may correspond to a structural relaxation that appears above 5V. In the constant current cycling measurements, the Li2CoPO4F samples exhibited a capacity as high as 109mAhg−1 and maintained a good cyclability between 2.0V and 5.5V vs. Li/Li+. XRD measurements confirmed that the discharged state is Li2CoPO4F. Combining these XRD results and electrochemical data proved that up to 1mol Li+ is extractable when charged to 5.5V. [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]

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]

LiNixMnyCo1−x−yO2 (NMC) cathode materials with Ni ≥ 0.8 have attracted great interest for high energy‐density lithium‐ion batteries (LIBs) but their practical applications under high charge voltages (e.g., 4.4 V and above) still face significant challenges due to severe capacity fading by the unstable cathode/electrolyte interface. Here, an advanced electrolyte is developed that has a high oxidation potential over 4.9 V and enables NMC811‐based LIBs to achieve excellent cycling stability in 2.5–4.4 V at room temperature and 60 °C, good rate capabilities under fast charging and discharging up to 3C rate (1C = 2.8 mA cm−2), and superior low‐temperature discharge performance down to −30 °C with a capacity retention of 85.6% at C/5 rate. It is also demonstrated that the electrode/electrolyte interfaces, not the electrolyte conductivity and viscosity, govern the LIB performance. This work sheds light on a very promising strategy to develop new electrolytes for fast‐charging high‐energy LIBs in a wide‐temperature range. [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]

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]

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]

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]

Lead-carbon batteries could provide better performance on high-rate partial-state-of-charge (HRPSoC) cycles than lead-acid batteries (LABs), making them promising for the new-generation of hybrid electric vehicles. The addition of carbon allotropes to the negative active material (NAM) could induce a significant improvement to the battery performance. Herein, an environmentally friendly strategy is demonstrated to prepare lead oxide and carbon (PbO@C) composite by pyrolyzing the lead citrate precursor derived from the spent lead paste of LABs. When the PbO@C composite is used as an additive to the NAM of lead-carbon batteries, the utilization efficiency of the NAM is improved from 56.9% to 72.5%, and the cycle life of the cell in HRPSoC is tremendously extended by four times compared with the control one. The enhancement in battery performance is attributed to the hydrophilic carbon in the composite, which acts as a 3D electroosmotic pump facilitating electrolyte diffusion, and hindering the tendency to excess sulfation during the HRPSoC operation. This proposed research provides a sustainable and scalable strategy to recycle the discarded/spent LABs into high-performance lead-carbon batteries. [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]

Abstract: To understand the limited cycle life performance and poor energy efficiency associated with rechargeable lithium–oxygen (Li–O2) batteries, the discharge products of primary Li–O2 cells at different depths of discharge (DOD) were systematically analyzed using XRD, FTIR and Ultra-high field MAS NMR. When discharged to 2.0V, the reaction products of Li–O2 cells include a small amount of Li2O2 along with Li2CO3 and RO–(C;OLi in the alkyl carbonate-based electrolyte. However, regardless of the DOD, there is no Li2O detected in the discharge products in the alkyl-carbonate electrolyte. For the first time it was revealed that in an oxygen atmosphere the high surface area carbon significantly reduces the electrochemical operation window of the electrolyte, and leads to plating of insoluble Li salts on the electrode at the end of the charging process. Therefore, the impedance of the Li–O2 cell continues to increase after each discharge and recharge process. After only a few cycles, the carbon air electrode is completely insulated by the accumulated Li salt terminating the cycling. [Copyright &y& Elsevier]

Electrolytes: Advanced Electrolytes for Fast-Charging High-Voltage Lithium-Ion Batteries in Wide-Temperature Range (Adv. Keywords: high-Ni layered cathodes; lithium ion batteries; localized high-concentration electrolytes EN high-Ni layered cathodes lithium ion batteries localized high-concentration electrolytes 1 1 1 06/11/20 20200609 NES 200609 In article number 2000368, Wu Xu and co-workers report the fabrication of an advanced localized high-concentration electrolyte with a high oxidation potential over 4.9 V. This electrolyte enables formation of ultrathin, uniform, robust and conductive electrode/electrolyte interphases on both graphite anodes and Ni-rich cathodes. High-Ni layered cathodes, lithium ion batteries, localized high-concentration electrolytes. [Extracted from the article]

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]

Silicon anodes are regarded as one of the most promising alternatives to graphite for high energy‐density lithium‐ion batteries (LIBs), but their practical applications have been hindered by high volume change, limited cycle life, and safety concerns. In this work, nonflammable localized high‐concentration electrolytes (LHCEs) are developed for Si‐based anodes. The LHCEs enable the Si anodes with significantly enhanced electrochemical performances comparing to conventional carbonate electrolytes with a high content of fluoroethylene carbonate (FEC). The LHCE with only 1.2 wt% FEC can further improve the long‐term cycling stability of Si‐based anodes. When coupled with a LiNi0.3Mn0.3Co0.3O2 cathode, the full cells using this nonflammable LHCE can maintain >90% capacity after 600 cycles at C/2 rate, demonstrating excellent rate capability and cycling stability at elevated temperatures and high loadings. This work casts new insights in electrolyte development from the perspective of in situ Si/electrolyte interphase protection for high energy‐density LIBs with Si anodes. [ABSTRACT FROM AUTHOR]

In article number 1502151, Ji‐Guang Zhang, Wu Xu, and co‐workers present the formation of a transient high‐concentration electrolyte layer on the Li anode surface during a fast stripping process. The highly concentrated Li+ ions immediately coordinate with available solvent molecules and facilitate the formation of a stabilized solid electrolyte interphase on the Li surface, thus effectively mitigating Li corrosion and enabling the sustainable operation of Li metal batteries. [ABSTRACT FROM AUTHOR]