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当前位置:首页 > 医学/心理学 > 医学试题/课件 > 双草酸硼酸锂(LiBOB)电解质性能研究
双草酸硼酸锂(LiBOB)电解质性能研究仇卫华1,刘兴江2,邢桃峰1,黄佳原,连芳11北京科技大学材料科学与工程学院,北京,1000832中国电子科技集团天津电源研究所,天津,3003812009-10-171引言化学电源锂离子电池存在的问题随着电子技术、能源、交通、国防等领域的高速发展,人们对高能量密度、长寿命、高安全性、廉价、环境友好的高性能化学电源的需求更加迫切起来。锂离子电池高的工作电压高、能量密度,长的循环寿命和小的自放电率等优点,成为目前所有电池产品中最有前途的体系之一。但锂离子电池被用作动力电源时还存在一定的问题,如大功率充放电性能有待提高,成本问题,安全性问题等。改进锂离子电池关键材料的性能!正极电解质负极有机溶剂锂盐碳酸酯类羧酸酯类醚类LiPF6EC+共溶剂锂离子电池电解液LiPF6和EC基电解液存在的问题对水敏感,水解产物HF腐蚀电极热稳定性差高温性能不理想EC的熔点较高,低温性能不理想需要寻找新型锂盐来替代LiPF6,以获取更好的电解液性能制备条件苛刻,污染严重新型锂盐双草酸硼酸锂-LiBOB很好的热稳定性,热分解温度较高可达300oC——增强了电池的安全性;不含有F元素,不会产生HF腐蚀电极材料及集流体,提高了电池的循环寿命,——降低了电池的成本;能够在碳负极表面形成较稳定的SEI膜,可以在纯PC溶剂中使用,——拓宽了电池使用温度范围;合成原料廉价易得,制备工艺简单,对环境友好。B.Yu,W.Qiuetal./J.ofPoowerSources166(2007)499-502高温下电解液1mol·L-1LiPF6EC/EMC(1:1)与1mol·L-1LiBOBEC/EMC(1:1)在LiNiO2/C电池中的放电容量比较XuK,ZhangSS,JowTR,etal.ElectrochemicalandSolid-StateLetters,2002,5(1):A26~A29各种锂盐在PC中配制成1mol·L-1的电解液,在Li/C半电池中的充放电曲线JowTR,DingMS,XuK,etal.J.PowerSources,2003,119~121:343~348S.Wang,W.Qiuetal./ElectrochimicaActa52(2007)4907-4910LiBOB基电解液存在的问题LiBOB溶解度以及电导率都低于LiPF6,电池高倍率放电特性不好;有很强的吸湿性,空气和溶剂中的杂质会影响LiBOB基电解液的性能LiBOB+EC+共溶剂在同样的碳酸酯类溶剂体系中,LiBOB电解液的低温性能也不如LiPF61.寻找适合LiBOB盐的新溶剂体系;2.寻找LiBOB的稳定剂。▼S.Wang,W.Qiuetal./ElectrochimicaActa52(2007)4907-4910TheConductivitiesof0.7mol/lLiBOBEC/PC/DMC/EMCelectrolytesat20℃0.000.250.500.751.000.000.250.500.751.000.000.250.500.751.0020oC5.705.605.505.305.104.904.704.504.304.003.80EC+DMC(1:1)EC+PC(1:1)PC+EMC(1:1)TheConductivitiesof0.7mol/lLiBOBEC/PC/DMC/EMCelectrolytesat60℃DMC:EC:PC=4:5:1DMC:EC:PC=3:5:2contourplotexperimentaldataboundarypoint11.811.511.010.510.310.09.809.509.0012.012.510.811.31234567891011PC+EMC(1:1)12131415EC+PC(1:1)EC+DMC(1:1)DMC:EC:PC=1:5:4DMC:EC:PC=2:5:3▼锂盐与水反应的热力学计算商品化锂盐LiPF6对水比较敏感,容易水解,在与大气的水或溶剂的残余水接触时,会发生如下反应。623LiPF(sol.)+HOPOF(sol.)+LiF(s)+2HF(sol.)(式1)24222224LiB(CO)(sol.)+2HOLiBO(sol.)+2HCO(sol.)(式2)+++++与LiPF6相似,新型锂盐LiBOB容易水解,水解反应式如下:反应的能量变化及吉布斯自由能变化(298.15K)(式3)+++242233224LiB(CO)(sol.)+3HOLiOOCCOOH(sol.)+HBO(sol.)+HCO(sol.)ΔE/kJ·mol-1ΔG/kJ·mol-1式(1)-2.424-0.470式(2)-65.444-28.688式(3)-112.783-62.952▼2.提高LiBOB在电解液中溶解度和电导率表1在锂离子电池中常用的溶剂Boilingpoint/℃Freezingpoint/℃Flashingpoint/℃Dielectricconstantat25℃Viscosityat25℃(mPa-1s-1)EC24437143901.9(40℃)PC238-49128662.51DMC903183.10.59EMC108-55232.90.65DEC127-43252.80.75GBL204-44101421.72.1LiBOB在GBL基电解液中的性能02040608048121620Conductivity/mScm-1Temperature/C1.5MLiBOB-GBL1.5MLiPF6-GBL0.7MLiBOB-EC/DEC图11.5MLiBOB-GBL,1.5MLiPF6-GBL以及0.7MLiBOB-EC/DEC(1:1,wt.)电解液电导率随温度的变化规律1。溶解度测试:2。电导率测试:GBLPCLiBOB溶解度2.6M1.5M0.00.20.40.60.81.01.21.41.61.82468101214Viscosity/mPasConcentrationmol/L图2.电解液粘度随LiBOB浓度的变化电解液浓度(mol/L)粘度(mPas)(27ºC)0.22.060.42.540.83.891.25.631.613.1表2.LiBOB-GBL粘度3。粘度图3室温条件下SS/0.8MLiBOB-GBL/SS电池的循环伏安图(扫描速率5mV/s)4。电化学稳定窗口的测试012345-0.10-0.08-0.06-0.04-0.020.000.020.040.060.080.100.8mol/LLiBOB-GBLCurrentDensity/mAcm-2Voltage/Vvs.Li+/LiS1S25.GBL分解产物测试RT:0.00-23.05SM:7G0246810121416182022Time(min)0102030405060708090100RelativeAbundance13.009.728.5310.8919.9521.8718.0616.7814.411.935.942.987.274.64NL:1.17E8TICF:MSyeti图3。1循环伏安扫描后的GBL溶液总离子色谱流出图(液相)Rt=8.53min所对应的是EAEARt=9.72min所对应的是DMCDMCRt=12.84min所对应的是GBLGBLRt=13.19min所对应的4–甲基–-丁内酯4–甲基–-丁内酯biao02#4004RT:13.19AV:1AV:5SB:123997-40024006-4011NL:2.66E5T:+cFullms[29.00-650.00]50100150200250300350400450500550600650m/z0102030405060708090100RelativeAbundance55.7084.71207.18132.89280.93354.90400.81460.23552.10OObiao02#3896RT:12.83AV:1AV:5SB:123889-38943898-3903NL:1.95E7T:+cFullms[29.00-650.00]50100150200250300350400450500550600650m/z0102030405060708090100RelativeAbundance85.67154.85280.78110.37197.85592.94542.76415.87324.04640.25367.03241.28OO图3。2Rt=12.84min的质谱图及其所对应的物质结构式(GBL)图3。3Rt=13.19min的质谱图及其所对应的物质结构式(4–甲基–-丁内酯)OOyeti#2585RT:8.53AV:1AV:5SB:122578-25832587-2592NL:4.69E5T:+cFullms[29.00-650.00]50100150200250300350400450500550600650m/z0102030405060708090100RelativeAbundance207.84132.99280.09493.35430.46354.82562.55610.11yeti#2949RT:9.72AV:1AV:5SB:122942-29472951-2956NL:8.54E5T:+cFullms[29.00-650.00]50100150200250300350400450500550600650m/z0102030405060708090100RelativeAbundance76.65281.68136.60206.70329.85416.34371.30613.30488.91OOO图3。4Rt=8.53min的质谱图及其所对应的结构式(EA)图3。5Rt=9.72min的质谱图及其所对应的结构式(DMC)6Li/LiFePO4半电池性能用1.5MLiBOB-GBL以及1.5MLiPF6-GBL电解液分别组装成Li/LiFePO4半电池,测试电池充放电的循环性能使用LiBOB-GBL电解液,LiFePO4/Li电池能够表现出良好的循环性能。而LiPF6-GBL电解液则不适用于LiFePO4/Li电池。010203040500255075100125150Dischargecapacity/mAhg-1Cyclenumber1.5MLiBOB-GBL1.5MLiPF6-GBL图430℃,1.5MLiBOB/LiPF6-GBL电解液Li/LiFePO4电池的充放电循环性能图(0.5C)(充放电电压范围为2.6~4.25V)6交流阻抗测试溶液电阻过大润湿性不好,界面电阻过大解决方法与粘度较低的有机溶剂配合使用080001600024000080001600024000204060800255075Z'/ohm-Z''/ohmZ'/ohm-Z''/ohm图51.0mol/LLiBOB-GBL电解液的交流阻抗图01020304050406080100120140160DischargingCapacity/mAh/gCyclenumber0.8MLiBOB-GBL:EA(1:1vol.)0.8MLiBOB-GBL:EA:DMC(1:1;1vol.)010203040506080100120140160DischargingCapacity/mAh/gCyclenumber0.8MLiBOB-GBL:EA(1:1vol.)0.8MLiBOB-GBL:EA:DMC(1:1:1vol.)7GBL/EA/DMC体系图60.8MLiBOB-GBL/EA体系和0.8MLiBOB-GBL/EA/DMC体系放电性能对比(0.5C)(50oC)图70.8MLiBOB-GBL/EA体系和0.8MLiBOB-GBL/EA/DMC体系倍率性能对比0.5C1C2C3C5C01020304050020406080100120140160
本文标题:双草酸硼酸锂(LiBOB)电解质性能研究
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