Lithium nitrate regulated carbonate electrolytes for practical Li-metal batteries: Mechanisms, principles and strategies

Li-metal batteries(LMBs)regain research prominence owing to the ever-increasing high-energy requirements.Commercially available carbonate electrolytes exhibit unfavourable parasitic reactions with Limetal anode(LMA),leading to the formation of unstable solid electrolyte interphase(SEI)and the breed of Li dendrites/dead Li.Significantly,lithium nitrate(LiNO_(3)),an excellent film-forming additive,proves crucial to construct a robust Li_(3)N/Li_(2)O/Li_(x)NO_(y)-rich SEI after combining with ether-based electrolytes.Thus,the given challenge leads to natural ideas which suggest the incorporation of LiNO_(3) into commercial carbonate for practical LMBs.Regrettably,LiNO_(3) demonstrates limited solubility(~800 ppm)in commercial carbonate electrolytes.Thence,developing stable SEI and dendrite-free LMA with the incorporation of LiNO_(3) into carbonate electrolytes is an efficacious strategy to realize robust LMBs via a scalable and cost-effective route.Therefore,this review unravels the grievances between LMA,LiNO_(3)and carbonate electrolytes,and enables a comprehensive analysis of LMA stabilizing mechanism with LiNO_(3),dissolution principle of LiNO_(3) in carbonate electrolytes,and LiNO_(3) introduction strategies.This review converges attention on a point that the LiNO_(3)-introduction into commercial carbonate electrolytes is an imperious choice to realize practical LMBs with commercial 4 V layered cathode.

Synthesizing an inorganic-rich solid electrolyte interphase by tailoring solvent chemistry in carbonate electrolyte for enabling high-voltage lithium metal batteries

High-voltage(>4.0 V)lithium metal battery(LBM)is considered to be one of the most promising candidates for next-generation high-energy batteries.However,the commercial carbonate electrolyte delivers a poor compatibility with Li metal anode,and its organic dominated solid electrolyte interphase(SEI)shows a low interfacial energy and a slow Li^(+)diffusion ability.In this work,an inorganic LiF-Li_(3)N rich SEI is designed to enable high-voltage LBM by introducing nano-cubic LiF and LiNO_(3)into1 M LiPF_(6)ethylene carbonate(EC)/dimethyl carbonate(DMC)(v:v=1:1)electrolyte.Specifically,the unique nano-cubic structure of as-synthetized LiF particles achieves its high concentration dissolution in carbonate electrolyte to enhance the interfacial energy of SEI.In addition,tetramethylene sulfolane(TMS)is used as a carrier solvent to dissolve LiNO_(3)in the carbonate electrolyte,thereby deriving a Li_(3)N-rich SEI.As a result,the as-designed electrolyte shows a high average Li plating/striping CE of 98.3%after 100 cycles at 0.5 m A cm^(-2)/0.5 mA h cm^(-2).Furthermore,it also enables the ultrathin Li(~50μm)‖LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM,4.4 mA h cm^(-2))full cell to deliver a high-capacity retention of 80.4%after 100 cycles with an outstanding average CE of 99.7%.Notably,the practical application prospect of the modified electrolyte is also estimated in LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)‖Li pouch cell with an energy density of 261.2 W h kg^(-1).This work sheds light on the internal mechanism of Li^(+)transport within the inorganic dominated SEI and provides a simple approach to stabilize the high-voltage LMBs.

Hybrid solid electrolyte interphases formed in conventional carbonate electrolyte enable high-voltage and ultra-stable magnesium metal batteries

Magnesium metal batteries are considered as viable alternatives of lithium-ion batteries for their low cost and high capacity of magnesium.Nevertheless,the practical application of magnesium metal batteries is extremely challenging due to a lack of suitable electrolyte that can stabilize magnesium metal anode and high-voltage cathode simultaneously.Herein,we found that in-situ formed lithium/magnesium hybrid electrolyte interphases in conventional LiPF6-containing carbonate-based electrolyte can not only prevent the production of passivation layer on the magnesium metal anode,but also inhibit the oxidation of the electrolyte under high voltage.The symmetric magnesium‖magnesium battery can achieve reversible stripping/plating for 1600 and 600 h at 0.02 and 0.1 mA cm^(-2),respectively.In addition,when coupled with a carbon fiber cathode,the magnesium metal battery exhibited a capacity retention rate of 96.3% for 1000 cycles at a current density of 500 mA g^(-1)and presented a working voltage of ~3.1 V.This research paves a new and promising path to the commercialization process of rechargeable magnesium metal batteries.

Reversible Magnesium Metal Anode Enabled by Cooperative Solvation/Surface Engineering in Carbonate Electrolytes

Magnesium metal anode holds great potentials toward future high energy and safe rechargeable magnesium battery technology due to its divalent redox and dendrite-free nature. Electrolytes based on Lewis acid chemistry enable the reversible Mg plating/stripping,while they fail to match most cathode materials toward highvoltage magnesium batteries. Herein,reversible Mg plating/stripping is achieved in conventional carbonate electrolytes enabled by the cooperative solvation/surface engineering. Strongly electronegative Cl from the MgCl_(2) additive of electrolyte impairs the Mg…O = C interaction to reduce the Mg^(2+) desolvation barrier for accelerated redox kinetics,while the Mg^(2+)-conducting polymer coating on the Mg surface ensures the facile Mg^(2+) migration and the e ective isolation of electrolytes. As a result,reversible plating and stripping of Mg is demonstrated with a low overpotential of 0.7 V up to 2000 cycles. Moreover,benefitting from the wide electrochemical window of carbonate electrolytes,high-voltage(> 2.0 V) rechargeable magnesium batteries are achieved through assembling the electrode couple of Mg metal anode and Prussian blue-based cathodes. The present work provides a cooperative engineering strategy to promote the application of magnesium anode in carbonate electrolytes toward high energy rechargeable batteries.

Catalytically altering the redox pathway of sulfur in propylene carbonate electrolyte using dual-nitrogen/oxygen-containing carbon

Carbonate electrolytes are one of the most desirable electrolytes for high-energy lithium-sulfur batteries(LSBs)because of their successful implementation in commercial Li-ion batteries.The low-polysulfide-solubility feature of some carbonate solvents also makes them very promising for overcoming the shuttle effects of LSBs.However,regular sulfur electrodes experience undesired electrochemical mechanisms in carbonate electrolytes due to side reactions.In this study,we report a catalytic redox mechanism of sulfur in propylene carbonate(PC)electrolyte based on a compari-son study.The catalytic mechanism is characterized by the interactions between polysulfides and dual N/O functional groups on the host carbon,which largely prevents side reactions between polysulfides and the carbonate electrolyte.Such a mechanism coupled with the low-polysulfide-solubility feature leads to stable cycling of LSBs in PC electrolyte.Favorable dual N/O functional groups are identified via a density functional theory study.This work provides an alternative route for enabling LSBs in carbonate electrolytes.

Realizing Stable Carbonate Electrolytes in Li-O_(2)/CO_(2)Batteries

The increasing demand for high-energy storage systems has propelled the development of Li-air batteries and Li-O_(2)/CO_(2)batteries to elucidate the mechanism and extend battery life.However,the high charge voltage of Li2CO3 accelerates the decomposition of traditional sulfone and ether electrolytes,thus adopting high-voltage electrolytes in Li-O_(2)/CO_(2)batteries is vital to achieve a stable battery system.Herein,we adopt a commercial carbonate electrolyte to prove its excellent suitability in Li-O_(2)/CO_(2)batteries.The generated superoxide can be captured by CO_(2)to form less aggressive intermediates,stabilizing the carbonate electrolyte without reactive oxygen species induced decomposition.In addition,this electrolyte permits the Li metal plating/stripping with a significantly improved reversibility,enabling the possibility of using ultra-thin Li anode.Benefiting from the good rechargeability of Li2CO3,less cathode passivation,and stabilized Li anode in carbonate electrolyte,the Li-O_(2)/CO_(2)battery demonstrates a long cycling lifetime of 167 cycles at 0.1 mA·cm^(-2)and 0.25 mAh·cm^(-2).This work paves a new avenue for optimizing carbonate-based electrolytes for Li-O_(2)and Li-O_(2)/CO_(2)batteries.

Room-temperature liquid metal engineered iron current collector enables stable and dendrite-free sodium metal batteries in carbonate electrolytes

Metallic sodium(Na)is believed to be a promising anode material for sodium-ion batteries(SIBs)due to its low electrochemical potential,high theoretical specific capacity,superior electrical conductivity,and so on.However,issues such as high chemical activity,the growth of Na dendrites,large volume change,and unstable interface impede its practical application.We design a cheap iron(Fe)-based substrate decorated by a thin liquid metal Ga layer for stable and dendrite-free Na metal anodes in low-cost carbonate electrolytes.The inherent mechanism of Ga-based liquid metal in inhibiting the growth of Na dendrites was revealed for the first time.Liquid metal Ga with sodiophilic property can act as nucleation seeds to decrease the nucleation barrier and induce homogeneous Na+flux,resulting in uniform and dendrite-free Na deposition.Full cells with Na_(3)V_(2)(PO_(4))_(3) cathode were also assembled to verify the practical application ability of the modified Na metal anode.Under the regulation of the liquid metal layer,the Coulombic efficiency,cycling life,and capacity of batteries are obviously enhanced.The strategy proposed here cannot only reduce the cost of batteries but also improve their electrochemical and safety performance.

Crosslinked solubilizer enables nitrate-enriched carbonate polymer electrolytes for stable,high-voltage lithium metal batteries

High-voltage lithium metal batteries(LMBs)have been considered promising next-generation highenergy-density batteries.However,commercial carbonate electrolytes can scarcely be employed in LMBs owing to their poor compatibility with metallic lithium.N,N-dimethylacrylamide(DMAA)-a crosslinkable solubilizer with a high Gutmann donor number-is employed to facilitate the dissolution of insoluble lithium nitrate(LiNO3)in carbonate-based electrolytes and to form gel polymer electrolytes(GPEs)through in situ polymerization.The Lit solvation structure of the GPEs is regulated using LiNO3 and DMAA,which suppresses the decomposition of LiPFe and facilitates the formation of an inorganic-rich solid electrolyte interface.Consequently,the Coulombic efficiency(CE)of the LillCu cell assembled with a GPE increases to 98.5%at room temperature,and the high-voltage LillNCM622 cell achieves a capacity retention of 80.1%with a high CE of 99.5%after 400 cycles.The bifunctional polymer electrolytes are anticipated to pave the way for next-generation high-voltage LMBs.

Converting LiNO_(3)additive to single nitrogenous component Li_(2)N_(2)O_(2)SEI layer on Li metal anode in carbonate-based electrolyte

With the increasing demand for high energy density energy storage device,Li metal has received intensive attention for its ultrahigh capacity and the lowest redox potential.LiNO_(3)is widely used as electrolyte additive for ether electrolyte,which can improve the cycle performance of Li metal anode.Compared to ethers,carbonates are more suitable for Li metal batteries with high voltage cathode because they have a wider electrochemical window.However,LiNO_(3)performs poor solubility in carbonate electrolyte,restricting its application in high voltage Li battery.Herein,we presented a facile method to introduce abundant LiNO_(3)additive to carbonate electrolyte system by introducing LiNO_(3)-PAN es as the interlayer of the cell.LiNO_(3)-PAN es is in sufficient contact with the electrolyte so that it can continuously releases LiNO_(3)to assist the formation of Li_(2)N_(2)O_(2)-rich single nitrogenous component SEI layer on Li surface.With the help of LiNO_(3)-PAN es,Li metal anode shows excellent cycle stability even at a high current density of 4mA/cm^(2),so that the cycle performance of the full cells was significantly improved,whether in the anode-free Cu||LFP cell or the Li||NCM622 cell.

Understanding Sulfur Redox Mechanisms in Different Electrolytes for Room-Temperature Na-S Batteries

This work reports influence of two different electrolytes,carbonate ester and ether electrolytes,on the sulfur redox reactions in room-temperature Na-S batteries.Two sulfur cathodes with different S loading ratio and status are investigated.A sulfur-rich composite with most sulfur dispersed on the surface of a carbon host can realize a high loading ratio(72%S).In contrast,a confined sulfur sample can encapsulate S into the pores of the carbon host with a low loading ratio(44%S).In carbonate ester electrolyte,only the sulfur trapped in porous structures is active via‘solid-solid’behavior during cycling.The S cathode with high surface sulfur shows poor reversible capacity because of the severe side reactions between the surface polysulfides and the carbonate ester solvents.To improve the capacity of the sulfur-rich cathode,ether electrolyte with NaNO_(3) additive is explored to realize a‘solid-liquid’sulfur redox process and confine the shuttle effect of the dissolved polysulfides.As a result,the sulfur-rich cathode achieved high reversible capacity(483 mAh g^(−1)),corresponding to a specific energy of 362 Wh kg^(−1) after 200 cycles,shedding light on the use of ether electrolyte for high-loading sulfur cathode.

Study on durability of Pt supported on graphitized carbon under simulated start-up/shut-down conditions for polymer electrolyte membrane fuel cells

The primary issue for the commercialization of proton exchange membrane fuel cell（PEMFC） is the carbon corrosion of support under start-up/shut-down conditions. In this study, we employ the nanostructured graphitized carbon induced by heat-treatment. The degree of graphitization starts to increase between 900 and 1300 ℃ as evidenced by the change of specific surface area, interlayer spacing, and ID/IG value. Pt nanoparticles are deposited on fresh carbon black（Pt/CB） and carbon heat-treated at 1700 ℃（Pt/HCB17） with similar particle size and distribution. Electrochemical characterization demonstrates that the Pt/HCB17 shows higher activity than the Pt/CB due to the inefficient microporous structure of amorphous carbon for the oxygen reduction reaction. An accelerating potential cycle between 1.0 and 1.5 V for the carbon corrosion is applied to examine durability at a single cell under the practical start-up/shutdown conditions. The Pt/HCB17 catalyst shows remarkable durability after 3000 potential cycles. The Pt/HCB17 catalyst exhibits a peak power density gain of 3%, while the Pt/CB catalyst shows 65% loss of the initial peak power density. As well, electrochemical surface area and mass activity of Pt/HCB17 catalyst are even more stable than those of the Pt/CB catalyst. Consequently, the high degree of graphitization is essential for the durability of fuel cells in practical start-up/shut-down conditions due to enhancing the strong interaction of Pt and π-bonds in graphitized carbon.

坚韧、弹性的氟化固体电解质界面稳定碳酸酯电解质中的锂金属

锂金属负极和碳酸酯类电解液之间不稳定的界面是限制高比能锂金属电池循环寿命的关键挑战.本文使用含苯环的双酚A乙氧基化物二甲基丙烯酸酯(BAED)交联剂调节聚(丙烯酸六氟丁酯)(PHFBA),设计了一种弹性人造固体电解质中间相(RASEI)来解决这个问题.刚性BAED分子可以对柔性PHBA基体进行调控,实现从600%伸长率到90%压缩率的卓越回弹性,并具有超过2 MPa的高杨氏模量.RASEI可以适应锂金属较大的体积变化,并确保电池运行过程中锂金属与RASEI之间的紧密接触,促进均匀的锂沉积并减少副反应.因此,经过RASEI修饰的Li‖Li对称电池可以在1 mA cm^(-2)和1 mAh cm^(-2)下实现超过500小时的长期循环.对循环后锂金属进行测试分析表明锂枝晶的生长得到了有效的抑制.此外,搭配20 mg cm^(-2)高阴极负载的NCM811软包电池在1 C下,经过200次循环后容量保持率超过85%.

Experimental and kinetic study on the stabilities and gas generation of typical electrolyte solvent components under oxygen-lean oxidation and pyrolysis conditions

The safety concerns of lithium-ion batteries(LIBs)due to thermal runaway hinder their broad applications.Flammable electrolytes are the major cause of gas venting and fire hazards of LIB,particularly when limited oxygen can be released because of the degradation of cathode materials.However,studies on the combustion characteristics of electrolytes under highly incomplete conditions,corresponding to thermal runaway scenarios,are limited.Therefore,a comprehensive experimental and kinetic study of three typical electrolyte solvents,namely,dimethyl carbonate(DMC),diethyl carbonate(DEC),and ethyl methyl carbonate(EMC),was performed under oxygen-lean and pyrolysis conditions.The experiments were conducted in a jet-stirred reactor with equivalence ratios of 2.5,5.0,and∞at atmospheric pressure,and the temperature ranged from 600 to 1100 K.Primary gas products,including H_(2),CH_(4),C_(2)H_(4),C_(2)H_(6),CH_(3)OH,C_(2)H_(5)OH,CO,and CO_(2),were quantified using gas chromatography.Results revealed that the consumption onset temperatures were in the order of DEC~EMC<DMC,regardless of the oxygen concentration.The addition of oxygen primarily influenced the consumption rate of DMC,whereas that of DEC and EMC was found to be less sensitive.Moreover,the oxidation of carbonates was prone to generate CO,CO_(2),H_(2),and CH_(4)rather than C_(2)H_(4).Reaction pathway analysis indicated that DEC and EMC were primarily consumed by two sequential unimolecular decomposition reactions,forming C_(2)H_(4),C_(2)H_(5)OH/CH_(3)OH,and CO_(2)regardless of the oxygen level.On the contrary,the primary reaction pathway for DMC changed from a unimolecular decomposition reaction to an H-abstraction reaction with oxygen addition.Furthermore,rate of production analysis was performed to obtain insights into the gas generation mechanism of flammable gases,such as H_(2),CH_(4),and C_(2)H_(4).The primary contributors to the formation and consumption of these gases under pyrolysis and oxidation conditions were revealed.

Temperature stability of symmetric activated carbon supercapacitors assembled with in situ electrodeposited poly (vinyl alcohol) potassium borate hydrogel electrolyte

The temperature stability of supercapacitor（SC） is largely determined by the properties of the electrolyte.Hydrogel electrolytes（HGE）, due to their hydrophilic polymer skeleton, show different temperature stability to that of liquid aqueous electrolytes. In this study, symmetric activated carbon（AC） SCs had been assembled with in situ electrodeposited poly（vinyl alcohol） potassium borate（PVAPB） HGE. The electrochemical performance of the SCs was systematically studied at different temperatures. Results show that the conductivity of PVAPB HGE is comparable with that of liquid aqueous electrolytes at different temperatures. The operating temperature range of PVAPB HGE SCs is -5–60°C, while those of the 1 mol/L Na2SO4SCs and the 0.9 mol/L KClSCs are 20–80°C and 20–40°C, respectively. The specific capacitance of PVAPB HGE SC is higher than those of SCs using liquid aqueous electrolytes at any temperature. The excellent temperature stability of PVAPB HGE makes it possible to build stable aqueous SCs in the wider temperature range.

High-performance organic electrolyte supercapacitors based on intrinsically powdery carbon aerogels

A novel class of powdery carbon aerogels（PCAs） has been developed by the union of microemulsion polymerization and hypercrosslinking, followed by carbonization. The resulting aerogels are in a microscale powdery form, demonstrate a well-defined 3D interconnected nanonetwork with hierarchical pores derived from numerous interstitial nanopores and intraparticle micropores, and exhibit high surface area（up to 1969 m^2/g）. Benefiting from these structural features, PCAs show impressive capacitive performances when utilized as electrodes for organic electrolyte supercapacitors,including large capacitances of up to 152 F/g, high energy densities of 37-15 Wh/kg at power densities of 34–6750 W/kg, and robust cycling stability.

Pre-constructed SEI on graphite-based interface enables long cycle stability for dual ion sodium batteries

Lithium batteries have been widely used in all over the world for its high energy density, long-term cycle stability. While the resources of lithium metal and transition metal are limited, which restrict their applications in the grid energy storage. Dual ion sodium batteries(DISBs) possess higher energy density,especially owning high power density for its higher operating voltage(> 4.5 V). Nevertheless, the poor oxidation tolerance of carbonate electrolyte and the co-intercalation of solvents accompanied with anions are main obstacles to make the DISBs commercialization. Herein, a physical barrier(artificial SEI film) is pre-constructed in the Na||graphite batteries to solve these thorny problems. With the CSMG(covered SEI on modified graphite), batteries deliver higher capacity 40 mAh/g even under the current density of 300 mA/g and the capacity retention maintains very well after 100 cycles at a high operating voltage.Moreover, the function mechanism was revealed by in-situ XRD, demonstrating that the pre-constructed SEI can effectively suppress the irreversible phase transition and exfoliation of graphite, resulting from the co-intercalation of anions. Additionally, the work voltage windows of carbonate electrolyte are significantly broadened by establishing electrode/electrolyte interphase. This method opens up an avenue for the practical application of DISBs on the grid energy storage and other fields.

Effects of ionic strength and temperature on the aggregation and deposition of multi-walled carbon nanotubes

The aggregation and deposition of carbon nanotubes（CNTs） determines their transport and fate in natural waters.Therefore,the aggregation kinetics of humic-acid treated multi-walled carbon nanotubes（HA-MWCNTs） was investigated by time-resolved dynamic light scattering in NaCl and CaCl_2 electrolyte solutions.Increased ionic strength induced HA-MWCNT aggregation due to the less negative zeta potential and the reduced electrostatic repulsion.The critical coagulation concentration（CCC） values of HA-MWCNTs were 80 mmol/L in NaCl and 1.3 mmol/L in CaCl_2 electrolyte,showing that Ca^（2＋） causes more serious aggregation than Na~＋.The aggregation behavior of HA-MWCNTs was consistent with Derjaguin-Landau-Verwey-Overbeek theory.The deposition kinetics of HA-MWCNTs was measured by the optical absorbance at 800 ran.The critical deposition concentrations for HA-MWCNT in NaCl and CaCl_2 solutions were close to the CCC values,therefore the rate of deposition cannot be increased by changing the ionic strength in the diffusion-limited aggregation regime.The deposition process was correlated to the aggregation since larger aggregates increased gravitational deposition and decreased random Brownian diffusion.HA-MWCNTs hydrodynamic diameters were evaluated at 5,15 and 25℃.Higher temperature caused faster aggregation due to the reduced electrostatic repulsion and increased random Brownian motion and collision frequency.HA-MWCNTs aggregate faster at higher temperature in either NaCl or CaCl_2electrolyte due to the decreased electrostatic repulsion and increased random Brownian motion.Our results suggest that CNT aggregation and deposition are two correlated processes governed by the electrolyte,and CNT transport is favored at low ionic strength and low temperature.