Regulating solid electrolyte interphase film on fluorinedoped hard carbon anode for sodium-ion battery

For the performance optimization strategies of hard carbon,heteroatom doping is an effective way to enhance the intrinsic transfer properties of sodium ions and electrons for accelerating the reaction kinetics.However,the previous work focuses mainly on the intrinsic physicochemical property changes of the material,but little attention has been paid to the resulting interfacial regulation of the electrode surface,namely the formation of solid electrolyte interphase(SEI)film.In this work,element F,which has the highest electronegativity,was chosen as the doping source to,more effectively,tune the electronic structure of the hard carbon.The effect of F-doping on the physicochemical properties of hard carbon was not only systematically analyzed but also investigated with spectroscopy,optics,and in situ characterization techniques to further verify that appropriate F-doping plays a positive role in constructing a homogenous and inorganic-rich SEI film.The experimentally demonstrated link between the electronic structure of the electrode and the SEI film properties can reframe the doping optimization strategy as well as provide a new idea for the design of electrode materials with low reduction kinetics to the electrolyte.As a result,the optimized sample with the appropriate F-doping content exhibits the best electrochemical performance with high capacity(434.53 mA h g^(-1)at 20mA g^(-1))and excellent rate capability(141 mAh g^(-1)at 400 mA g^(-1)).

Anchoring polysulfide with artificial solid electrolyte interphase for dendrite-free and low N/P ratio Li-S batteries

Lithium sulfur batteries are regarded as a promising candidate for high-energy-density energy storage devices.However,the lithium metal anode in lithium-sulfur batteries encounters the problem of lithium dendrites and lithium metal consumption caused by polysulfide corrosion.Herein we design a dualfunction PMMA/PPC/LiNO3composite as an artificial solid electrolyte interphase(PMCN-SEI)to protect Li metal anode.This SEI offers multiple sites of C=O for polysulfide anchoring to constrain corrosion of Li metal anode.The lithiated polymer group and Li3N in PMCN-SEI can homogenize lithium-ion deposition behavior to achieve a dendrite-free anode.As a result,the PMCN-SEI protected Li metal anode enables the Li||Li symmetric batteries to maintain over 300 cycles(1300 h)at a capacity of 5 m Ah cm^(-2),corresponding to a cumulative capacity of 3.25 Ah cm^(-2).Moreover,Li-S batteries assembled with 20μm of Li metal anode(N/P=1.67)still deliver an initial capacity of 1166 m A h g-1at 0.5C.Hence,introducing polycarbonate polymer/inorganic composite SEI on Li provides a new solution for achieving the high energy density of Li-S batteries.

The influence of formation temperature on the solid electrolyte interphase of graphite in lithium ion batteries

Lithium-ion battery has greatly changed our lifestyle and the solid electrolyte interphase(SEI)covered on the graphite anode determines the service life of a battery.The formation method and the formation temperature at initial cycle of a battery determine the feature of the SEI.Herein,we investigate the gap of formation behavior in both a half cell(graphite matches with lithium anode)and a full cell(graphite matches with NCM,short for LiNixCoyMn1-x-yO2)at different temperatures.We conclude that high temperature causes severe side reactions and low temperature will result in low ionic conductive SEI layer,the interface formed at room temperature owns the best ionic conductivity and stability.

SEI膜形貌与结构对锂离子电池性能的影响

固态电解质界面膜(SEI)是电解液与电极在固/液相界面上发生电化学反应后,覆盖在电极表面的钝化层,其通常形成于电池的化成阶段,具有传导离子、隔绝电子的特征。优良的SEI膜对于提高锂离子电池(LIBs)的循环寿命、安全性等具有重要意义。不同电解液体系形成的SEI膜形貌和结构各不相同,对LIBs性能具有不同程度的影响。因此,深入分析SEI膜形貌和结构与电池性能之间的构效关系很重要。本文首先综述了影响SEI膜结构和性质的因素;然后阐述了原位/非原位表征SEI膜形貌和结构的主要方法,并介绍了一种新型的电化学阻抗表征技术;最后总结了SEI膜结构对LIBs离子传输、锂沉积和界面脱溶剂化等方面的影响。通过总结SEI膜的结构与LIBs性能之间的关系,以期靶向调控SEI膜结构提升锂离子电池性能。

Long‐life lithium batteries enabled by a pseudo‐oversaturated electrolyte

The specific energy of Li metal batteries(LMBs)can be improved by using high‐voltage cathode materials;however,achieving long‐term stable cycling performance in the corresponding system is particularly challenging for the liquid electrolyte.Herein,a novel pseudo‐oversaturated electrolyte(POSE)is prepared by introducing 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether(TTE)to adjust the coordination structure between diglyme(G2)and lithium bis(trifluoromethanesulfonyl)imide(LiTFSI).Surprisingly,although TTE shows little solubility to LiTFSI,the molar ratio between LiTFSI and G2 in the POSE can be increased to 1:1,which is much higher than that of the saturation state,1:2.8.Simulation and experimental results prove that TTE promotes closer contact of the G2 molecular with Li^(+)in the POSE.Moreover,it also participates in the formation of electrolyte/electrode interphases.The electrolyte shows outstanding compatibility with both the Li metal anode and typical high‐voltage cathodes.Li||Li symmetric cells show a long life of more than 2000 h at 1 mA cm^(−2),1 mAh cm^(−2).In the meantime,Li||LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)cell with the POSE shows a high reversible capacity of 134.8 mAh g^(−1 )after 900 cycles at 4.5 V,1 C rate.The concept of POSE can provide new insight into the Li^(+)solvation structure and in the design of advanced electrolytes for LMBs.

Synergy effect of regulated Li-plating and functional solid electrolyte interphase on graphite anodes

The growth of Li dendrites poses potential safety hazard to lithium-ion batteries(LIBs),and eliminating Li dendrites thoroughly stills face tough difficulties ahead.Thus,regulating Li-plating is a critical optimization-direction to address the issue.Herein,a“graphite-Li hybrid”anode with high reversibility is realized under the constant-capacity lithiation(CCL).Within CCL,the uniform distribution of Li-plating on the graphite surface is successfully achieved.The evolution in different states of solid electrolyte interphase(SEI)is investigated in detail to study the interaction between the potentials and impedance during the process of Liintercalation and Li-deintercalation.Under the potential below 0 V and the state of charge(SOC)of 110%relative to the theoretical capacity,the F-rich SEI with high stability is constructed to hinder the emergency of Li dendrites and maintain the intact structure of graphite anode under long cycling.The cell presents more than 100%Coulombic efficiency(CE)with the 900 cycles,demonstrating the reversible Li-plating and the utilization of defects.And the CCL half-cell provides a good cycling performance and specific capacity of 900 cycles at 0.5 C,it is attributed to the synergy effect of stable inorganic-rich SEI and regulated active Li-plating.

A Review of Solid Electrolyte Interphase(SEI)and Dendrite Formation in Lithium Batteries

Lithium-metal batteries with high energy/power densities have significant applications in electronics,electric vehicles,and stationary power plants.However,the unstable lithium-metal-anode/electrolyte interface has induced insufficient cycle life and safety issues.To improve the cycle life and safety,understanding the formation of the solid electrolyte interphase(SEI)and growth of lithium dendrites near the anode/electrolyte interface,regulating the electrodeposition/electrostripping processes of Li^(+),and developing multiple approaches for protecting the lithium-metal surface and SEI layer are crucial and necessary.This paper comprehensively reviews the research progress in SEI and lithium dendrite growth in terms of their classical electrochemical lithium plating/stripping processes,interface interaction/nucleation processes,anode geometric evolution,fundamental electrolyte reduction mechanisms,and effects on battery performance.Some important aspects,such as charge transfer,the local current distribution,solvation,desolvation,ion diffusion through the interface,inhibition of dendrites by the SEI,additives,models for dendrite formation,heterogeneous nucleation,asymmetric processes during stripping/plating,the host matrix,and in situ nucleation characterization,are also analyzed based on experimental observations and theoretical calculations.Several technical challenges in improving SEI properties and reducing lithium dendrite growth are analyzed.Furthermore,possible future research directions for overcoming the challenges are also proposed to facilitate further research and development toward practical applications.

锂离子电池硅基负极电解液添加剂研究进展:挑战与展望

随着新能源和动力系统应用的日益成熟,锂离子电池在未来必将发挥越来越重要的作用,高比能电池已经成为当前研究的热点,并不断提出更高的性能要求。具有超高理论能量密度的硅材料被认为是缓解电动汽车行业里程焦虑的新一代负极材料,预示着未来几年将是硅基负极锂离子电池产业化应用的黄金时期。然而,硅在脱/嵌锂过程中会反复收缩膨胀(体积变化率约为300%),致使负极材料粉化、脱落,进而失去电接触,造成负极材料的失活;其次,循环过程中不断的体积变化会对其表面固体电解质界面层造成持续不断的破坏,因此难以形成稳定的固体电解质中间相(SEI)膜,这导致大量活性锂和电解液的消耗,最终导致容量快速衰减。本综述旨在从电解液添加剂在SEI形成和修饰、Lewis碱中和、溶剂化调控等作用机理角度对硅基负极界面恶化方面所面临的挑战进行分析,并重点介绍硅基负极电解液添加剂的最新成果。此外,通过对氟、硅烷、酰胺、氰酸酯等官能团构效关系方面的深入讨论和比较,本综述还深入研究了电解液添加剂的设计问题,以激发读者的新思路和新想法,协助读者识别或者设计合成适用于硅基负极的电解液添加剂,为高比能电池的发展铺平道路。

高温锂离子电池用混盐电解液体系

正极电解质相界面(CEI)膜会影响锂离子电池的高温性能。商用电解液在高温下的热稳定性差,形成的CEI膜不够稳定,易导致电池失效。以热稳定性及成膜性能良好的双三氟磺酰亚胺锂(LiTFSI)和二氟草酸硼酸锂(LiODFB)为锂盐,EC+EMC(体积比3∶7)为溶剂,构建电解液体系,考察制备的LiCoO_(2)/Li半电池的电化学性能。在70℃下,LiCoO_(2)/Li半电池在0.5 mol/L LiTFSI+0.5 mol/L LiODFB基电解液体系下,以1.0 C在2.7~4.2 V循环,首次放电比容量为131.2 mAh/g,循环100次的容量保持率为90.8%。这得益于电解液体系生成了均匀、致密且具有良好离子电导率的CEI膜。

高性能锂金属负极研究进展

锂金属负极凭借高理论容量和低电化学电位,一直被誉为最具潜力的负极材料。然而,锂金属目前仍面临着锂枝晶不可控生长的风险,这严重影响了锂金属电池的循环寿命和安全性能,阻碍了其在实际生产中的应用。目前,改善锂金属负极性能的研究主要集中在SEI膜的调控、构建锂复合结构和引入固态电解质等3个方面。本文综述了多种策略在锂金属负极性能优化中的研究现状,展望了锂金属负极在未来储能领域的发展趋势。

In-situ constructed polymer/alloy composite with high ionic conductivity as an artificial solid electrolyte interphase to stabilize lithium metal anode

Lithium(Li)metal is regarded as the best anode material for lithium metal batteries(LMBs)due to its high theoretical specific capacity and low redox potential.However,the notorious dendrites growth and extreme instability of the solid electrolyte interphase(SEI)layers have severely retarded the commercialization process of LMBs.Herein,a double-layered polymer/alloy composite artificial SEI composed of a robust poly(1,3-dioxolane)(PDOL)protective layer,Sn and LiCl nanoparticles,denoted as PDOL@Sn-LiCl,is fabricated by the combination of in-situ substitution and polymerization processes on the surface of Li metal anode.The lithiophilic Sn-LiCl multiphase can supply plenty of Li-ion transport channels,contributing to the homogeneous nucleation and dense accumulation of Li metal.The mechanically tough PDOL layer can maintain the stability and compact structure of the inorganic layer in the long-term cycling,and suppress the volume fluctuation and dendrites formation of the Li metal anode.As a result,the symmetrical cell under the double-layered artificial SEI protection shows excellent cycling stability of 300 h at 5.0 mA·cm^(−2)for 1 mAh·cm^(−2).Notably,the Li||LiFePO_(4)full cell also exhibits enhanced capacity retention of 150.1 mAh·g^(−1)after 600 cycles at 1.0 C.Additionally,the protected Li foil can effectively resist the air and water corrosion,signifying the safe operation of Li metal in practical applications.This present finding proposed a different tactic to achieve safe and dendrite-free Li metal anodes with excellent cycling stability.

锂离子电池SEI成膜添加剂的研究

开发高效优质的固体电解质界面(SEI)成膜添加剂是提高锂离子电池性能的一种经济而有效的途径.本文从SEI成膜添加剂成膜机理的角度,分析和评价了已有的还原型添加剂、反应型添加剂及修饰型添加剂的作用效果;综述了理论计算在锂离子电池SEI成膜添加剂研究中的应用,并提出了"理论设计、材料合成、性能评估"三个研究环节无缝连接锂离子电池中SEI成膜添加剂创新研发的新思路.

Solid electrolyte interphase on anodes in rechargeable lithium batteries

Highly safe and efficient rechargeable lithium batteries have become an indispensable component of the intelligent society powering smart electronics and electric vehicles.This review summarizes the formation principle,chemical compositions,and theoretical models of the solid electrolyte interphase(SEI)on the anode in the lithium battery,involving the functions and influences of the electroactive materials.The discrepancies of the SEI on different kinds of anode materials,as well as the choice and design of the electrolytes are detailedly clarified.Furthermore,the design strategies to obtain a stable and efficient SEI are outlined and discussed.Last but not least,the challenges and perspectives of artificial SEI technology are briefly proposed for the development of high-efficiency batteries in practice.

锂离子电池SEI膜形成机理及化成工艺影响

固体电解质相界面(SEI)膜是锂离子电池在化成工艺过程中形成的重要物质,它的形成以及性能优劣对锂离子电池的最终性能有着重要影响,同时,锂离子电池生产中的化成工艺直接影响SEI膜的性质优劣。综述了电池负极上SEI膜的形成概况、化成工艺的参数控制对SEI膜形成过程和性质的作用,以及其对锂离子电池性能的影响。Si基负极材料是未来负极材料的重点发展方向,分析了针对Si基负极材料的SEI膜形成所面临的困难与挑战,以及Si基负极的化成工艺参数控制是改进电池生产的必要手段与基础。

Vinylene carbonate additive for EMITFSI-based electrolyte for Li/LiFePO_4 batteries

Ionic liquids have been paid much attention and are considered to replace the conventional organic electrolyte and solve the safety issues by virtue of nonvolatility,non-flammability,high ionic conductivity and extended electrochemical steady window.The paper introduces ionic liquids electrolyte on basis of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI),which shows a wide electrochemical window (0.5-4.5 V vs.Li+/Li),and is theoretically feasible as an electrolyte for Li/LiFePO4batteries to improve the safety.Linear sweep voltammetry (LSV) was performed to investigate the electrochemical stability window of the polymer electrolyte.Interfacial resistance for Li/electrolyte/Li symmetric cells and Li/electrolyte/LiFePO4 cells were studied by electrochemical impedance spectroscopy (EIS).The results showed that additive vinylene carbonate (VC) enhances the formation of solid electrolyte interphase film to protect lithium anodes from corrosion and improves the compatibility of ionic liquid electrolyte towards lithium anodes.Accordingly,Li/LiFePO4cells delivers the initial discharge capacity of 124 mAh g-1 at a current rate of 0.1C in the ionic liquid electrolyte (EMITFSI+0.8 mol L-1LiTFSI+5 wt%VC),and shows better cyclability than in the ionic liquid electrolyte without VC.

Enhanced interfacial compatibility of FeS@N,S-C anode with ester-based electrolyte enables stable sodium-ion full cells

The development of sodium-ion full cells is seriously suppressed by the incompatibility between electrodes and electrolytes. Most representatively, high-voltage ester-based electrolytes required by the cathodes present poor interfacial compatibility with the anodes due to unstable solid electrode interphase(SEI). Herein, Fe S@N,S-C(spindle-like Fe S nanoparticles individually encapsulated in N,S-doped carbon) with excellent structural stability is synthesized as a potential sodium anode material. It exhibits exceptional interfacial stability in ester-based electrolyte(1 M NaClO_(4) in ethylene carbonate/propylene carbonate with 5% fluoroethylene carbonate) with long-cycling lifespan(294 days) in Na|Fe S@N,S-C coin cell and remarkable cyclability in pouch cell(capacity retention of 82.2% after 170 cycles at 0.2 A g^(-1)).DFT calculation reveals that N,S-doping on electrode surface could drive strong repulsion to solvated Na_(2) and preferential adsorption to ClO_(4)^(-) anion, guiding the anion-rich inner Helmholtz plane.Consequently, a robust SEI with rich inorganic species(NaCl and Na_(2)O) through the whole depth stabilizes the electrode–electrolyte interface and protects its integrity. This work brings new insight into the role of electrode’s surface properties in interfacial compatibility that can guide the design of more versatile electrodes for advanced rechargeable metal-ion batteries.

SEI膜对锂金属负极电化学性能影响的研究进展

固体电解质界面(SEI)膜是影响锂离子在电极表面电化学行为的主要因素。阐述了SEI膜的形成机制,分析了SEI的微观结构和组成模型,讨论了锂离子在SEI膜中的迁移机制。在此基础上,进一步介绍了对SEI膜进行改性调控锂离子的电化学行为的研究进展,以期为SEI膜的改性提供参考。

Challenges in the Development of Film-Forming Additives for Lithium Ion Battery: A Review

Electrolytes additives are ubiquitous and indispensable in all electrochemical devices. In this sense, the principle and the classification of film-forming additives for lithium ion secondary batteries are described. The film formation mechanism and research progress of the pyrazole derivatives, organic halogenide, esters and derivatives, boron compounds and inorganic compounds are introduced. Emphasis is focused on the principles and film-forming mechanisms of each additive. The development of film-forming additives is forecasted and prospected.

Dynamically lithium-compensated polymer artificial SEI to assist highly stable lithium-rich manganese-based anode-free lithium metal batteries

Owing to the unique structure,anode-free lithium metal batteries(AFLMBs)have higher energy density and lower production cost than traditional lithium metal batteries(LMBs)or lithium-ion batteries(LIBs),However,AFLMBs suffer from an inherently finite Li reservoir and exhibit poor cycle stability,low Coulombic efficiency(CE)and severe dendrite growth.In this work,polydiallyl lithium disulfide(PDS-Li)was successfully synthesized and coated on Cu current collector by electrochemical polymerization.The PDS-Li acts as an additional lithium resource to compensate for the irreversible loss of lithium during cycling.In addition,the special structure and lithiophilicity of PDS-Li contribute to lower nucleation overpotential and uniform lithium deposition.When coupled with Li-rich manganese-based(LRM)cathode of Li1.2Mn0.54Ni0.13Co0.13O2,the anode-free full cell exhibits significantly improved cycle stability over 100 cycles and capacity retention of 63.3%and 57%after 80 and 100 cycles,respectively.We believe that PDS-Li can be used to ensure stable cycling performance and high-energy-density in AFLMBs.

15-冠醚-5用作电解液低温添加剂的综述

向电解液加入低温添加剂可改善锂离子电池的低温性能。当温度降低(如-20℃以下)导致电解液大量凝固或锂盐析出时,电池的阻抗会急剧上升。综述15-冠醚-5作低温添加剂改进低温性能的因素:与Li+的特定溶剂化,有利于形成光滑致密的固体电解质相界面膜;可提高锂盐在低温下的溶解度和电离度;熔点为-40℃,可降低电解液的凝固温度。