Battery Separators Functionalized with Edge-Rich MoS2/C Hollow Microspheres for the Uniform Deposition of Li2S in High-Performance Lithium-Sulfur Batteries

As promising energy storage systems,lithium-sulfur(Li-S)batteries have attracted significant attention because of their ultra-high energy densities.However,Li-S battery suffers problems related to the complex phase conversion that occurs during the charge-discharge process,particularly the deposition of solid Li2S from the liquid-phase polysulfides,which greatly limits its practical application.In this paper,edge-rich MoS2/C hollow microspheres(Edg-MoS2/C HMs)were designed and used to functionalize separator for Li-S battery,resulting in the uniform deposition of Li2S.The microspheres were fabricated through the facile hydrothermal treatment of MoO3-aniline nanowires and a subsequent carbonization process.The obtained Edg-MoS2/C HMs have a strong chemical absorption capability and high density of Li2S binding sites,and exhibit excellent electrocatalytic performance and can effectively hinder the polysulfide shuttle effect and guide the uniform nucleation and growth of Li2S.Furthermore,we demonstrate that the Edg-MoS2/C HMs can effectively regulate the deposition of Li2S and significantly improve the reversibility of the phase conversion of the active sulfur species,especially at high sulfur loadings and high C-rates.As a result,a cell containing a separator functionalized with Edg-MoS2/C HMs exhibited an initial discharge capacity of 935 mAh g-1 at 1.0 C and maintained a capacity of 494 mAh g-1 after 1000 cycles with a sulfur loading of 1.7 mg cm-2.Impressively,at a high sulfur loading of 6.1 mg cm-2 and high rate of 0.5 C,the cell still delivered a high reversible discharge capacity of 478 mAh g-1 after 300 cycles.This work provides fresh insights into energy storage systems related to complex phase conversions.

A multi-layered Ti3C2/Li2S composite as cathode material for advanced lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries with lithium sulfide(Li2S)as cathode have attracted great attention recently,because of high specific capacity(1166 mA h g^-1)of Li2S and potential safety of using Li metal-free anode.Li2S cathode has lower volume expansion and higher thermal stability than the traditional sulfur cathode.However,the problems of"shuttle effect"and poor electrical conductivity of the cathode material still need to be overcome.In this work,multi-layered Ti3C2/Li2S(ML-Ti3C2/Li2S)composite has been prepared and applied as a cathode in advanced Li-S batteries.The unique multi-layer sheet structure of Ti3 C2 provides space for the storage of Li2S,and its good conductivity greatly enhances the usage ratio of Li2 S and improves the conductivity of the whole Li2S cathode.Compared with commonly used graphene,ML-Ti3C2 can trap polysulfides effectively by chemical adsorption and also activate the reaction of Li2S to polysulfides by forming Ti-S bond.As a result,during the cycling of the batteries with ML-Ti3C2/Li2S cathodes,the activation voltage barrier of the first cycle has decreased to 2.8 V,and the"shuttle effect"has been suppressed effectively.The cycling and rate performances of the ML-Ti3C2/Li2S cathodes have been significantly improved compared to that of graphene/Li2 S cathodes.They maintain a capacity of 450 mAh g^-1 at 0.2 C after 100 cycles,and deliver attractive rate performances of 750,630,540,470 and 360 mAh g^-1 at 0.1 C,0.2 C,0.5 C,1 C,and 2 C,respectively.

Co-recrystallization induced self-catalytic Li2S cathode fully interfaced with sulfide catalyst toward a high-performance lithium-free sulfur battery

Lithium sulfide(Li_(2)S)is a promising cathode for a practical lithium-sulfur battery as it can be coupled with various safe lithium-free anodes.However,the high activation potential(>3.5 V)together with the shuttling of lithium polysulfides(LiPSs)bottleneck its practical uses.We are trying to present a catalysis solution to solve both problems simultaneously,specially with twinborn heterostructure to shoot off the trouble in interfacial contact between two solids,catalyst and Li_(2)S.As a typical example,a Co9S8/Li_(2)S heterostructure is reported here as a novel self-catalytic cathode through a co-recrystallization followed by a one-step carbothermic conversion.Co9S8 as the catalyst effectively lowers the Li_(2)S activation potential(<2.4 V)due to fully integrated and contacted interfaces and consistently promotes the conversion of LiPSs to suppress the shuttling.The obtained freestanding cathode of Co9S8/Li_(2)S heterostructures encapsulated in three-dimensional graphene shows a high capacity,reaching 92.6%of Li_(2)S theoretical capacity,high rate performance(739 mAh g1 at 2 C),and a low capacity fading(0.039%per cycle at 1 C over 900 cycles).Even under a high Li_(2)S loading of 12 mg cm^(-2)and a low E/S ratio of 5μL mgLi_(2)S^(-1),86%of theoretical capacity can be utilized.

Li2S-P2S5体系电解质及其在全固态锂离子电池中的应用研究进展

全固态锂离子电池具有安全性能好、能量密度高、工作温区广等优点,被广泛应用于便携式电子设备。固态电解质是全固态锂离子电池的关键材料之一,其中的硫化物电解质具有离子电导率高、电化学窗口宽、晶界电阻低和易成膜等特点,被认为最有希望应用于全固态锂离子电池。本文综述了Li2S-P2S5体系电解质的发展状况,包括固态电解质的制备、改性、表征以及电极/固态电解质之间的固-固界面的稳定兼容问题。本文还涉及了以Li2S-P2S5为电解质的全固态锂离子电池性能的研究进展。

不同浓度Li_2SO_4水溶液结构的X射线衍射研究

用θ～ 2θ型粉末衍射仪反射法精确测量了不同浓度的Li2 SO4水溶液的衍射数据 ,通过数据处理给出了溶液的结构函数和径向分布函数 ,由几何结构模型的最小二乘法精修 ,得到了溶液中阳离子和阴离子第一、二水合层的结构参数。

All-Solid-State Thin-Film Lithium-Sulfur Batteries

Lithium-sulfur(Li-S)system coupled with thin-film solid electrolyte as a novel high-energy micro-battery has enormous potential for complementing embedded energy harvesters to enable the autonomy of the Internet of Things microdevice.However,the volatility in high vacuum and intrinsic sluggish kinetics of S hinder researchers from empirically integrating it into allsolid-state thin-film batteries,leading to inexperience in fabricating all-solid-state thin-film Li-S batteries(TFLSBs).Herein,for the first time,TFLSBs have been successfully constructed by stacking vertical graphene nanosheets-Li2S(VGsLi2S)composite thin-film cathode,lithium-phosphorous-oxynitride(LiPON)thin-film solid electrolyte,and Li metal anode.Fundamentally eliminating Lipolysulfide shuttle effect and maintaining a stable VGs-Li2S/LiPON interface upon prolonged cycles have been well identified by employing the solid-state Li-S system with an“unlimited Li”reservoir,which exhibits excellent longterm cycling stability with a capacity retention of 81%for 3,000 cycles,and an exceptional high temperature tolerance up to 60℃.More impressively,VGs-Li2S-based TFLSBs with evaporated-Li thin-film anode also demonstrate outstanding cycling performance over 500 cycles with a high Coulombic efficiency of 99.71%.Collectively,this study presents a new development strategy for secure and high-performance rechargeable all-solid-state thin-film batteries.

电解质体系对FeS_2/LiSi热电池激活时间的影响研究

采用空载和带载两种放电方式,研究了热电池常用的二元和三元全锂电解质体系对Fe S2/Li Si热电池激活时间的影响。实验结果表明:空载放电时,二元电解质激活时间短;带载放电时,三元全锂电解质激活时间短。

ZnS coating of cathode facilitates lean‐electrolyte Li‐S batteries

Tremendous effort has been devoted to lithium‐sulfur batteries,where flooded electrolytes have been employed ubiquitously.The use of lean electrolytes albeit indispensable for practical applications often causes low capacity and fast capacity fading of the sulfur cathode;thus,the electrolyte/sulfur active mass ratios below 5μL/mg have been rarely reported.Herein,we demonstrate that ZnS coating transforms sulfur cathode materials electrolyte‐philic,which tremendously promotes the performance in lean electrolytes.The ZnS‐coated Li2S@graphene cathode delivers an initial discharge capacity of 944mAh/g at an E/S ratio of 2μL/mg at the active mass loading of 5.0 mg Li2S/cm^2,corresponding to an impressive specific energy of 500Wh/kg based on the mass of cathode,electrolyte,and the assumed minimal mass of lithium metal anode.Density functional theory calculations reveal strong binding between ZnS crystals and electrolyte solvent molecules,explaining the better wetting properties.We also demonstrate the reversible cycling of a hybrid cathode of ZnS‐coated Li2S@graphene mixed with VS2 as an additive at an E/AM(active mass)ratio of 1.1μL/mg,equivalent to the specific energy of 432 Wh/kg on the basis of the mass of electrodes and 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.

墨水涂覆法制备硫化物全固态锂离子电池

采用墨水涂覆技术制备基于硫化物的电解质薄膜及其全固态锂离子电池。通过N-甲基吡咯烷酮(NMP)溶剂对真空烧结法制得的Li_8P_2S_9粉末进行处理,获得均匀、稳定的湛蓝色Li_8P_2S_9墨水。研究结果表明:NMP溶剂处理后的Li_8P_2S_9颗粒粒径从10μm降低到1μm左右,物相晶体结构不变,但改善颗粒间的接触性能。在Li_8P_2S_9墨水中添加一定量的聚偏二氟乙烯(PVDF)黏结剂,溶解完全后将墨水滴涂在磷酸铁锂正极表面,除去溶剂即可一步实现电解质的成膜及电解质与正极的复合。当PVDF与Li_8P_2S_9的质量比为1:10时,电解质膜30℃下的锂离子电导率为2.03×10^(-4)S/cm,25℃电化学窗口为5.15V。以该墨水涂覆法制得的LiFePO_4/Li电池可在室温下稳定工作,0.2C下循环100圈的平均比容量为113.7mA·h/g,库仑效率为99%。

具有碳纳米管基底的硫化交联聚苯乙烯刷的制备及其锂载体性能

不可控的锂枝晶生长、严重的体积膨胀以及脆弱的固态电解质中间相(SEI)严重制约了锂金属电池(LMBs)的实际应用。在本研究中,我们成功设计合成了一类具有碳纳米管基底的硫化超交联聚苯乙烯刷(CNT-g-sxPS),并将其用作新型的三维锂金属载体。CNT-g-sxPS的层次化大孔、中孔和微孔能够促进锂离子的传输,缓解锂负极的体积变化,提供高比表面积以降低局部电流密度,从而实现快速且均匀的锂沉积/剥离。同时,孔骨架表面均匀分布的含硫基团可以与锂原位反应生成含Li2S的SEI,有利于构筑稳定的负极/电解液界面。此外,碳纳米管基底还能提供快速的电子传输路径。因此,利用CNT-g-sxPS负载的锂金属负极(CNT-g-sxPS@Cu/Li)组装的Li|Li对称电池在1 mA cm^(-2)、1 mAh cm^(-2)下可稳定循环超过500 h。当与磷酸铁锂正极(LFP)匹配时,利用CNT-g-sxPS@Cu/Li负极组装的全电池在1 C下循环600圈后仍然具有101 mAh g^(-1)的放电比容量,容量保持率为77%。

Dual-Functional Organotelluride Additive for Highly Efficient Sulfur Redox Kinetics and Lithium Regulation in Lithium–Sulfur Batteries

High energy density and low cost made lithium–sulfur(Li–S)batteries appealing for the next-generation energy storage devices.However,their commercial viability is seriously challenged by serious polysulfide shuttle effect,sluggish sulfur kinetics,and uncontrollable dendritic Li growth.Herein,a dual-functional electrolyte additive,diphenyl ditelluride(DPDTe)is reported for Li–S battery.For sulfur cathodes,DPDTe works as a redox mediator to accelerate redox kinetics of sulfur,in which Te radical-mediated catalytic cycle at the solid–liquid interface contributes significantly to the whole process.For lithium anodes,DPDTe can react with lithium metal to form a smooth and stable organic–inorganic hybrid solid-electrolyte interphase(SEI),enabling homogeneous lithium deposition for suppressing dendrite growth.Consequently,the Li–S battery with DPDTe exhibits remarkable cycling stability and superb rate capability,with a high capacity up to 1227.3 mAh g^(-1)and stable cycling over 300 cycles.Moreover,a Li–S pouch cell with DPDTe is evaluated as the proof of concept.This work demonstrates that organotelluride compounds can be used as functional electrolyte additives and offers new insights and opportunities for practical Li–S batteries.

Resonant charge transfer in slow Li^+–Li(2s) collisions

The resonant charge transfer process for Li＋-Li（2s） collision is investigated by the quantum-mechanical molecular orbital close-coupling（QMOCC） method and the two-center atomic-orbital close-coupling（AOCC） method in an energy range of 1.0 e V/u-104e V/u. Accurate molecular structure data and charge transfer cross sections are given. Both the allelectron model（AEM） and one-electron model（OEM） are used in the QMOCC calculations, and the discrepancies between the two models are analyzed. The OEM calculation can also give a reliable prediction of the cross sections for energies below 1 ke V/u.

Lithium sulfide:a promising prelithiation agent for high-performance lithium-ion batteries

Lithium-ion batteries are widely used in portable electronics and electric vehicles due to their high energy density,stable cycle life,and low self-discharge.However,irreversible lithium loss during the formation of the solid electrolyte interface greatly impairs energy density and cyclability.To compensate for the lithium loss,introducing an external lithium source,that is,a prelithiation agent,is an effective strategy to solve the above problems.Compared with other prelithiation strategies,cathode prelithiation is more cost-effective with simpler operation.Among various cathode prelithiation agents,we first systematically summarize the recent progress of Li_(2)S-based prelithiation agents,and then propose some novel strategies to tackle the current challenges.This review provides a comprehensive understanding of Li_(2)S-based prelithiation agents and new research directions in the future.

Bonding VSe2 ultrafine nanocrystals on graphene toward advanced lithium-sulfur batterie

Lithium–sulfur batteries have been attracting considerable research attention due to their high energy densities and low costs. However, one of their main challenges is the undesired shuttling of polysulfides, causing rapid capacity degradation. Herein, we report the first example of sulfiphilic VSe2 ultrafine nanocrystals immobilized on nitrogen-doped graphene to modify the battery separator for alleviating the shuttling problem. VSe2 nanocrystals provide numerous active sites for chemisorption of polysulfides as well as benefit the nucleation and growth of Li2S. Furthermore, the kinetic reactions are accelerated which is confirmed by higher exchange current density and higher lithium ion diffusion coefficient. And the first-principles calculations further show that the exposed sulfiphilic planes of VSe2 boost the redox of Li2S. When used as separators within the lithium sulfur batteries, the cell indicates greatly enhanced electrochemical performances with excellent long cycling stability and exceptional rate capability up to 8 C. Moreover, it delivers a higher areal capacity of 4.04 mAh·cm^−2 as well as superior cycling stability with sulfur areal loading up to 6.1 mg·cm^−2. The present strategy can encourage us in engineering novel multifunctional separators for energy-storage devices.

Improvement of stability and solid-state battery performances of annealed 70Li_(2)S–30P_(2)S_(5) electrolytes by additives

The replacement of liquid electrolyte with solid electrolyte can significantly improve the safety and power/energy density of lithium batteries.70Li_(2)S–30P_(2)S_(5) is one of the most promising solid electrolytes with high conductivity for solid–state batteries.In this work,the ionic conductivity and stability toward moisture and lithium metal of 70Li_(2)S–30P_(2)S_(5) were enhanced by introducing the different amounts of Li_(2)O additives.65Li_(2)S–30P_(2)S_(5)–1%Li_(2)O delivered the highest conductivity,while 65Li_(2)S–30P_(2)S_(5)–5%Li_(2)O showed the best moisture stability and improved lithium compatibility.Solid-state batteries using 65Li_(2)S–30P_(2)S_(5)–5%Li_(2)O electrolyte and high-voltage LiNi_(0.6)Mn_(0.2)Co_(0.2)O_(2) cathode exhibited low initial discharge capacity(100 mAh·g^(-1))and Coulombic efficiency(69%).Li_(3)InCl_(6) electrolytes were introduced both in the cathode mixture to replace sulfide electrolyte and in the interface layer to improve the cathode compatibility for the solid-state batteries,showing enhanced discharge capacity(175 mAh·g^(-1))and improved initial Coulombic efficiency(86%).Moreover,it also exhibited good performance at-20℃.

Li10GeP2S12固态电解质电极界面特性研究

采用高温固相法合成了固态电解质Li10GeP2S12,其室温离子电导率为2.02×10-3 S/cm,并组装了LiNbO3@LiNi1/3Co1/3Mn1/3O2/Li10GeP2S12/Li全固态电池.恒流充放电测试表明全固态电池首次放电容量121.2 mAh/g,库伦效率40周后稳定在99.8%左右,循环100周后容量保持率达93.7%.电化学阻抗谱的测试结果表明,其典型的阻抗谱图由高频区半圆(HFS)、中频区半圆(MFS)和低频区斜线(LFL)组成,其中,HFS归属于电解质阻抗(Rel//Qel),MFS归属于电荷传递过程(Rct//Qdl),LFL归属于锂离子的固态扩散过程.通过选取适当的等效电路,对实验所得的电化学阻抗谱数据进行拟合,并分析了Rel和Rct随电极电位的变化规律.