Effect of low concentration electrolytes on the formation and corrosion resistance of PEO coatings on AM50 magnesium alloy

In this paper,the formation process,morphology,and electrochemical performance of PEO coatings on AM50 magnesium alloy prepared in low concentration phosphate,aluminate,and phosphate-aluminate electrolytes were systematically studied.The results show that the coatings prepared from the phosphate electrolytes have a higher thickness and better corrosion resistance properties compared to the other electrolytes.The coatings prepared from low concentration phosphate-aluminate mixed electrolytes have slightly thinner thickness,a similar coating structure and an order of magnitude lower value of electrochemical impedance compared with phosphate electrolyte coatings.The Coatings prepared from low concentration aluminate electrolytes have the lowest thickness and the worst corrosion resistance properties which gets close to corrosion behavior of the bare AM50 under the same test conditions.Considering application,coatings prepared from single low concentration phosphate electrolytes and low concentration phosphate-aluminate electrolytes have greater potential than single low concentration aluminate coatings.However,reducing the electrolyte concentrations of coating forming ions too much has negative influence on the coating growth rate.

Diluted low concentration electrolyte for interphase stabilization of high-voltage LiNi_(0.5)Mn_(1.5)O_(4) cathode

The Co-free Li Ni_(0.5)Mn_(1.5)O_(4)(LNMO)is a promising cathode for lithium-ion batteries owing to its high operating voltage and low costs.However,the synthesis of LNMO is generally time and energy consuming,and its practical application is hindered by the lack of a compatible electrolyte.Herein,a spray pyrolysis-based energy-saving synthesis method as well as a diluted low concentration electrolyte(0.5 M LiPF_(6) in a mixture of fluoroethylene carbonate/dimethyl carbonate/1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether(FEC:DMC:TTE,1:4:5 by volume))are proposed to address these challenges.Owing to the unique features of the precursor prepared by spray pyrolysis,well-crystallized LNMO single-crystal can be obtained within 1 h calcination at 900℃.Besides,the fluorinated interphases derived from the diluted low concentration electrolyte not only mitigate the Mn dissolution and Al corrosion at the cathode side,but also suppresses dendritic Li deposition at the anode side,thus enabling stable cycling of both LNMO and Li metal anode.Thus,30μm Li|LNMO(1.75 m A h cm^(-2))cells achieve a high capacity retention(90.9%)after 168 cycles in the diluted low concentration electrolyte.

LiTFSI salt concentration effect to digest lithium polysulfides for high-loading sulfur electrodes

Sulfur utilization improvement and control of dissolved lithium polysulfide(LiPS;Li_(2)S x,2<x≤8)are cru-cial aspects of the development of lithium-sulfur(Li-S)batteries,especially in high-loading sulfur elec-trodes and low electrolyte/sulfur(E/S)ratios.The sluggish reaction in the low E/S ratio induces poor LiPS solubility and unstable Li_(2)S electrodeposition,resulting in limited sulfur utilization,especially under high-loading sulfur electrode.In this study,we report on salt concentration effects that improve sulfur utilization with a high-loading cathode(6 mgs ulfurcm^(-2)),a high sulfur content(80 wt%)and a low E/S ratio(5 m L gs ulfur^(-1)).On the basis of the rapid LiPS dissolving in a low concentration electrolyte,we estab-lished that the quantity of Li_(2)S electrodeposition from a high Li+diffusion coefficient,referring to the reduction of LiPS precipitation,was significantly enhanced by a faster kinetic.These results demonstrate the importance of kinetic factors for the rate capability and cycle life stability of Li-S battery electrolytes through high Li_(2)S deposition under high-loading sulfur electrode.

Designing Advanced Liquid Electrolytes for Alkali Metal Batteries:Principles,Progress,and Perspectives

The ever-growing pursuit of high energy density batteries has triggered extensive efforts toward developing alkali metal(Li,Na,and K)battery(AMB)technologies owing to high theoretical capacities and low redox potentials of metallic anodes.Typically,for new battery systems,the electrolyte design is critical for realizing the battery electrochemistry of AMBs.Conventional electrolytes in alkali ion batteries are generally unsuitable for sustaining the stability owing to the hyper-reactivity and dendritic growth of alkali metals.In this review,we begin with the fundamentals of AMB electrolytes.Recent advancements in concentrated and fluorinated electrolytes,as well as functional electrolyte additives for boosting the stability of Li metal batteries,are summarized and discussed with a special focus on structure-composition-performance relationships.We then delve into the electrolyte formulations for Na-and K metal batteries,including those in which Na/K do not adhere to the Li-inherited paradigms.Finally,the challenges and the future research needs in advanced electrolytes for AMB are highlighted.This comprehensive review sheds light on the principles for the rational design of promising electrolytes and offers new inspirations for developing stable AMBs with high performance.

Charting the course to solid-state dual-ion batteries

An electrolyte destined for use in a dual-ion battery(DIB)must be stable at the inherently high potential required for anion intercalation in the graphite electrode,while also protecting the Al current collector from anodic dissolution.A higher salt concentration is needed in the electrolyte,in comparison to typical battery electrolytes,to maximize energy density,while ensuring acceptable ionic conductivity and operational safety.In recent years,studies have demonstrated that highly concentrated organic electrolytes,ionic liquids,gel polymer electrolytes(GPEs),ionogels,and water-in-salt electrolytes can potentially be used in DIBs.GPEs can help reduce the use of solvents and thus lead to a substantial change in the Coulombic efficiency,energy density,and long-term cycle life of DIBs.Furthermore,GPEs are suited to manufacture compact DIB designs without separators by virtue of their mechanical strength and electrical performance.In this review,we highlight the latest advances in the application of different electrolytes in DIBs,with particular emphasis on GPEs.

Electrolyte Concentration Regulation Boosting Zinc Storage Stability of High-Capacity K0.486V2O5 Cathode for Bendable Quasi-Solid-State Zinc Ion Batteries

Vanadium-based cathodes have attracted great interest in aqueous zinc ion batteries(AZIBs)due to their large capacities,good rate performance and facile synthesis in large scale.However,their practical application is greatly hampered by vanadium dissolution issue in conventional dilute electrolytes.Herein,taking a new potassium vanadate K0.486V2O5(KVO)cathode with large interlayer spacing(~0.95 nm)and high capacity as an example,we propose that the cycle life of vanadates can be greatly upgraded in AZIBs by regulating the concentration of ZnCl2 electrolyte,but with no need to approach“water-in-salt”threshold.With the optimized moderate concentration of 15 m ZnCl2 electrolyte,the KVO exhibits the best cycling stability with ~95.02% capacity retention after 1400 cycles.We further design a novel sodium carboxymethyl cellulose(CMC)-moderate concentration ZnCl2 gel electrolyte with high ionic conductivity of 10.08 mS cm^-1 for the first time and assemble a quasi-solid-state AZIB.This device is bendable with remarkable energy density(268.2 Wh kg^−1),excellent stability(97.35% after 2800 cycles),low self-discharge rate,and good environmental(temperature,pressure)suitability,and is capable of powering small electronics.The device also exhibits good electrochemical performance with high KVO mass loading(5 and 10 mg cm^-2).Our work sheds light on the feasibility of using moderately concentrated electrolyte to address the stability issue of aqueous soluble electrode materials.

Stable interfaces constructed by concentrated ether electrolytes to render robust lithium metal batteries

Lithium metal batteries(LMBs)are highly considered as promising candidates for next-generation energy storage systems.However,routine electrolytes cannot tolerate the high potential at cathodes and low potential at anodes simultaneously,leading to severe interfacial reactions.Herein,a highly concentrated electrolyte(HCE)region trapped in porous carbon coating layer is adopted to form a stable and highly conductive solid electrolyte interphase(SEI)on Li metal surface.The protected Li metal anode can potentially match the high-voltage cathode in ester electrolytes.Synergistically,this ingenious design promises high-voltage-resistant interfaces at cathodes and stable SEI with abundance of inorganic components at anodes simultaneously in high-voltage LMBs.The feasibility of this interface-regulation strategy is demonstrated in Li|LiFePO_(4) batteries,realizing a lifespan twice as long as the routine cells,with a huge capacity retention enhancement from 46.4%to 88.7%after 100 cycles.This contribution proof-ofconcepts the emerging principles on the formation and regulation of stable electrode/electrolyte interfaces in the cathode and anode simultaneously towards the next-generation high-energy-density batteries.

Concentrated dual-salt electrolytes for improving the cycling stability of lithium metal anodes

Lithium（Li） metal is an ideal anode material for rechargeable Li batteries, due to its high theoretical specific capacity（3860 mAh/g）, low density（0.534 g/cm3）, and low negative electrochemical potential（-3.040 V vs. standard hydrogen electrode）. In this work, the concentrated electrolytes with dual salts, composed of Li[N（SO2F）2]（Li FSI） and Li[N（SO2CF3）2]（Li TFSI） were studied. In this dual-salt system, the capacity retention can even be maintained at 95.7%after 100 cycles in Li｜Li FePO4 cells. A Li｜Li cell can be cycled at 0.5 mA/cm2 for more than 600 h, and a Li｜Cu cell can be cycled at 0.5 m A/cm2 for more than 200 cycles with a high average Coulombi efficiency of 99%. These results show that the concentrated dual-salt electrolytes exhibit superior electrochemical performance and would be a promising candidate for application in rechargeable Li batteries.

Recent advances in “water in salt” electrolytes for aqueous rechargeable monovalent-ion(Li^(+), Na^(+), K^(+)) batteries

Aqueous rechargeable batteries have attracted enormous attention owning to their intrinsic characteristics of non-flammability, low cost, and the superior ionic conductivity of the aqueous electrolyte.However, the narrow electrochemical stability window(1.23 V), imposed by hydrogen and oxygen evolution, constrains the overall energy density of batteries. The revolutionary "water-in-salt” electrolytes considerably expand the electrochemical stability window to 3 or even 4 volts, giving rise to a new series of high-voltage aqueous metal-ion chemistries. Herein, the recent advances in "water-in-salt” electrolytes for aqueous monovalent-ion(Li^(+), Na^(+), K^(+)) rechargeable batteries have been systematically reviewed. Meanwhile, the corresponding reaction mechanisms, electrochemical performances and the existing challenges and opportunities are also highlighted.

Moderately concentrated electrolyte enabling high-performance lithium metal batteries with a wide working temperature range

The electrolyte integrated with lithium metal anodes is subjected to the issues of interfacial compatibility and stability,which strongly influence the performances of high-energy lithium metal batteries.Here,we report a new electrolyte recipe viz.a moderately concentrated electrolyte comprising of 2.4 M lithium bis(fluorosulfonyl)imide(LiFSI)in a cosolvent mixture of fluorinated ethylene carbonate(FEC)and dimethyl carbonate(DMC)with relatively high ion conductivity.Owing to the preferential decomposition of LiFSI and FEC,an inorganic-rich interphase with abundant Li_(2)O and LiF nanocrystals is formed on lithium metal with improved robustness and ion transfer kinetics,enabling lithium plating/stripping with an extremely low overpotential of~8 mV and the average CE of 97%.When tested in Li||LiFePO_(4) cell,this electrolyte provides long-term cycling with a capacity retention of 98.3%after 1000 cycles at 1 C and an excellent rate performance of 20 C,as well as an areal capacity of 1.35 mA h cm^(-2)at the cathode areal loading of 9 mg cm^(-2).Moreover,the Li||LiFePO_(4) cell exhibits excellent wide-temperature performances(-40~60℃),including long-term cycling stability over 2600 cycles without visible capacity fading at 0℃,as well as extremely high average CEs of 99.6%and 99.8% over 400 cycles under-20℃ and 45℃.

Concentrated ternary ether electrolyte allows for stable cycling of a lithium metal battery with commercial mass loading high-nickel NMC and thin anodes

A new concentrated ternary salt ether-based electrolyte enables stable cycling of lithium metal battery(LMB)cells with high-mass-loading(13.8 mg cm^(−2),2.5 mAh cm^(−2))NMC622(LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2))cathodes and 50μm Li anodes.Termed“CETHER-3,”this electrolyte is based on LiTFSI,LiDFOB,and LiBF4 with 5 vol%fluorinated ethylene carbonate in 1,2-dimethoxyethane.Commer-cial carbonate and state-of-the-art binary salt ether electrolytes were also tested as baselines.With CETHER-3,the electrochemical performance of the full-cell battery is among the most favorably reported in terms of high-voltage cycling stability.For example,LiNi_(x)Mn_(y)Co_(1-x-y)O_(2)(NMC)-Li metal cells retain 80%capacity at 430 cycles with a 4.4 V cut-off and 83%capacity at 100 cycles with a 4.5 V cut-off(charge at C/5,discharge at C/2).According to simulation by density functional theory and molecular dynamics,this favorable performance is an outcome of enhanced coordination between Li^(+)and the solvent/salt molecules.Combining advanced microscopy(high-resolution transmission electron microscopy,scanning electron microscopy)and surface science(X-ray photoelectron spectroscopy,time-of-fight secondary ion mass spectroscopy,Fourier-transform infrared spectroscopy,Raman spectroscopy),it is demonstrated that a thinner and more stable cathode electrolyte interphase(CEI)and solid electrolyte interphase(SEI)are formed.The CEI is rich in lithium sulfide(Li_(2)SO_(3)),while the SEI is rich in Li_(3)N and LiF.During cycling,the CEI/SEI suppresses both the deleterious transformation of the cathode R-3m layered near-surface structure into disordered rock salt and the growth of lithium metal dendrites.

Flame-retardant concentrated electrolyte enabling a Li F-rich solid electrolyte interface to improve cycle performance of wide-temperature lithium–sulfur batteries

Lithium–sulfur batteries have been regarded as the most promising high-energy electrochemical energy storage device owing to the high energy density, low cost and environmental friendliness. However, traditional lithium–sulfur batteries using ether-based electrolytes often suffer from severe safety risks(i.e. combustion). Herein, we demonstrated a novel kind of flame-retardant concentrated electrolyte(6.5 M lithium bis(trifluoromethylsulphonyl)imide/fluoroethylene carbonate) for highly-safe and widetemperature lithium–sulfur batteries. It was found that such concentrated electrolyte showed superior flame retardancy, high lithium-ion transference number(0.69) and steady lithium plating/stripping behavior(2.5 m Ah cm^(-2) over 3000 h). Moreover, lithium–sulfur batteries using this flame-retardant concentrated electrolyte delivered outstanding cycle performance in a wide range of temperatures(-10 °C, 25 °C and 90 °C). This superior battery performance is mainly attributed to the LiF-rich solid electrolyte interphase formed on lithium metal anode, which can effectively suppress the continuous growth of lithium dendrites. Above-mentioned fascinating characteristics would endow this flame-retardant concentrated electrolyte a very promising candidate for highly-safe and wide-temperature lithium–sulfur batteries.

An all-organic aqueous potassium dual-ion battery

Benefiting from the environmental friendliness of organic electrodes and the high security of aqueous electrolyte,an all-organic aqueous potassium dual-ion full battery(APDIB) was assembled with 21 M potassium bis(fluoroslufonyl)imide(KFSI) water-in-salt as the electrolyte.The APDIB could deliver a reversible capacity of around 50 mAh g^(-1) at 200 mA g^(-1)(based on the weight of total active materials),a long cycle stability over 900 cycles at 500 mA g^(-1) and a high coulombic efficiency of 98.5%.The reaction mechanism of APDIB during the charge/discharge processes is verified:the FSI-could associate/disassociate with the nitrogen atom in the polytriphenylamine(PTPAn) cathode,while the K^(+) could react with C=O bonds in the 3,4,9,10-perylenetetracarboxylic diimide(PTCDI) anode reversibly.Our work contributes toward the understanding the nature of water-into-salt electrolyte and successfully constructed all-organic APDIB.

Factors Affecting Diffusion of Ions in Soils

In this work the diffusion coefficients of Na+, K+, Ca2+, NO3- and Cl- ions were estimated in terms of measuring apparent direct current (DC) conductivities of latosol, red soil and yellow-brown earth containing, respectively, NaNO3, KCI, and CaCl2 of different concentrations (0.005, 0.05, 0.10, and 0.15 mol / L) in the case of moisture contents ranging from wet to water saturation. The results showed that when bulk density, moisture content, and electrolyte concentration were constant, the diffusion coefficients of cations were in the order Na+> K+> Ca2+ except for Na+ and K+ in latosol, while the order for anions was NO3- > Cl-. The diffusion coefficients (Di) of cations and anions were linearly proportional to volumetric moisture content (θ) as electrolyte concentration and bulk density were unchanged. When moisture content and bulk density were constant, the diffusion coefficients of cations decreased, to varying extents, with the increase of electrolyte concentration, and the decrement in different soils followed the order yellow-brown earth > red soil > latosol, but the decrement order of different cations was Na+> K+ > Ca2+.

Lactation mastitis: Promising alternative indicators for early diagnosis

Although lactation mastitis(LM)has been extensively researched,the incidence rate of LM remains a salient clinical problem.To reduce this incidence rate and achieve a better prognosis,early and specific quantitative indicators are particularly important.It has been found that milk electrolyte concentrations(chloride,potassium,and sodium)and electrical conductivity(EC)significantly change in the early stages of LM in an animal model.Several studies have evaluated EC for the detection of subclinical mastitis in cows.EC,chloride,and sodium content of milk were more accurate for predicting infection status than were other variables.In the early stages of LM,lactic sodium,chloride,and EC increase,but potassium decreases.However,these indicators have not been reported in the diagnosis of LM in humans.This review summarizes the pathogenesis and the mechanism of LM in terms of milk electrolyte concentration and EC,and aim to provide new ideas for the detection of sub-clinical mastitis in humans.

MXene-based symmetric supercapacitors with high voltage and high energy density

MXene-based aqueous symmetric supercapacitors(SSCs)are attractive due to their good rate performances and green nature.However,it remains a challenge to reach voltages much over 1.2 V,which significantly diminishes their energy density.Herein,we report on Mo_(1.33)CTz MXene-based SSCs possessing high voltages in a 19.5 M LiCl electrolyte.Benefiting from the vacancy-rich structure and high stable potential window of Mo_(1.33)CTz,the obtained SSCs deliver a maximum energy density of>38.2 mWh cm^(-3) at a power density of 196.6 mW cm^(-3) under an operating voltage of 1.4 V,along with excellent rate performance and impressive cycling stability.This highly concentrated LiCl electrolyte is also applicable to Ti_(3)C_(2)Tz,the most widely studied MXene,achieving a maximum energy density of>41.3 mWh cm^(-3) at a power density of 165.2 mW cm^(-3) with an operating voltage of 1.8 V.The drop in energy density with increasing power in the Ti_(3)C_(2)Tz cells was steeper than for the Mo-based cells.This work provides a roadmap to develop superior SSCs with high voltages and high energy densities.

Concentrated electrolytes for rechargeable lithium metal batteries

Traditional lithium-ion batteries with graphite anodes have gradually been limited by the glass ceiling of energy density.As a result,lithium metal batteries(LMBs),regarded as the ideal alternative,have attracted considerable attention.However,lithium is highly reactive and susceptible to most electrolytes,resulting in poor cycle performance.In addition,lithium grows Li dendrites during charging,adversely affecting the safety of LMBs.Therefore,LMBs are more sensitive to the chemical composition of electrolytes and their relative ratios(concentrations).Recently,concentrated electrolytes have been widely demonstrated to be friendly to lithium metal anodes(LMAs).This review focuses on the progress of concentrated electrolytes in LMBs,including the solvation structure varying with concentration,unique functions in stabilizing the LMA,and their interfacial chemistry with LMA.

An ultra-low concentration electrolyte with fluorine-free bulky anions for stable potassium metal batteries

Potassium metal battery is a promising alternative to Li-ion battery for large-scale energy storage due to the abundant potassium resources and high energy density.However,it suffers from rapid capacity fading and safety issues due to the uncontrolled dendrite growth.Herein,we design a fluorine-free ultra-low concentration electrolyte(ULCE)with the super bulky[BPh_(4)]^(−) anions for stable potassium metal battery.In this special electrolyte,the migration rate of K+in the electrolyte is about six times faster than that of the[BPh_(4)]^(−) anions because of the super bulky structure of the[BPh_(4)]^(−) anions,thus resulting in a high K^(+)transference number of 0.76.This high transference number can effectively make up for the deficiency of K^(+)in ULCE for ensuring the normal operation of the potassium metal battery.In addition,the improved transference number can also promote the uniform distribution of K^(+)flux on the surface of the K metal anode,resulting in uniform K deposition.As a result,this electrolyte achieves a high K plating/stripping Coulombic efficiency of 92.6%over 200 cycles and a stable discharging/charging for 100 cycles under the full battery configuration(K used as the anode and perylene-3,4,9,10-tetracarboxylic dianhydride used as the cathode).

Solvating power regulation enabled low concentration electrolyte for lithium batteries

Li^(+) solvation structures have a decisive influence on the electrode/electrolyte interfacial properties and battery performances.Reduced salt concentration may result in an organic rich solid electrolyte interface(SEI)and catastrophic cycle stability,which makes low concentration electrolytes(LCEs)rather challenging.Solvents with low solvating power bring in new chances to LCEs due to the weak salt-solvent interactions.Herein,an LCE with only 0.25 mol L^(-1) salt is prepared with fluoroethylene carbonate(FEC)and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether(D_(2)).Molecular dynamics simulations and experiments prove that the low solvating power solvent FEC not only renders reduced desolvation energy to Li^(+) and improves the battery kinetics,but also promotes the formation of a LiF-rich SEI that hinders the electrolyte consumption.Li||Cu cell using the LCE shows a high coulombic efficiency of 99.20%,and LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)||Li cell also exhibits satisfying capacity retention of 89.93%in 200 cycles,which demonstrates the great potential of solvating power regulation in LCEs development.

Effect of electrolyte concentration o n the tribological performance of MAO coatings on aluminum alloys

Micro-arc oxidation(MAO)is an efficient approach to improve the hardness,wea r resistance,and other properties of aluminum alloys.In order to investigate the effect of the electrolyte concentration on the properties of MAO coatings for LY12 alloy,the voltage variation during the MAO process was recorded.The surface morphologies and phase compositions of the coatings produced with different electrolytes were investigated using scanning electron microscopy and X-ray diffraction,respectively.The roughness and thickness of the coatings were measured using a pocket roughness meter a nd an eddy-current thickness meter,respectively.The tribological performances of the coatings wer e investigated against GCr15 bearing steel on aball-on-disc wear tester in open air.The results showed that with an increase in the Na2SiO3 content,the working voltage of the MAO process decreased,the roughness a nd thickness of the coatings increased significantly,a nd the relative content of the α-Al2O3 phase decreased.With an increase in the KOH content,the working voltage decreased slightly,the roughness and thickness of the coatings increased slightly,and the α-and γ-Al2O3 phase contents remained unchanged.The friction coefficient and wear rate of the coatings increased with an increase in the Na2Sio3 and KoH concentrations.A decrease in the porosity and roughness and an increase in the α-Al2O3 content of the coatings reduced their wear mass loss.