纳米锂镧锆钽氧粉体复合聚氧化乙烯制备的固态电解质电化学性能的研究

与采用液体电解液的传统二次锂离子电池相比,固态二次锂电池在高能量密度和安全性方面具有显著的潜在优势,近年来成为国内外的研究热点。作为固态二次锂电池的核心组成,固态电解质需要具备高离子电导率、宽电化学窗口、对锂稳定、力学性能优以及可抑制锂枝晶等特性。为达到以上要求,本工作探索制备了由纳米钽掺杂锂镧锆氧（LLZTO）粉体与聚氧化乙烯（PEO）复合的有机-无机复合固态电解质膜材料,对比研究了在有机物PEO中添加锂盐和不添加锂盐对固态电解质膜电导率及电化学特性的影响。发现在PEO-LLZTO复合电解质膜中,虽然PEO不导电,但界面处存在的渗流效应可极大提高膜的总电导率,室温离子电导率可达到2×104 S/cm。这一数值虽然略低于PEO-LiTFSI-LLZTO复合电解质膜（室温条件下电导率为6×104 S/cm）,但无锂盐添加的PEO-LLZTO复合电解质膜表现出较好的电化学稳定性和较强的抑制锂枝晶的能力。将PEO-LLZTO复合电解质膜与Li/LiFePO4和Li/LiFe0.15Mn0.85PO4组装成软包电池,在0.1 C、60 ℃的测试条件下可充分发挥正极材料的容量,并可稳定循环200次以上。     

Compounding preparation of novel solid electrolyte with high lithium ion conductivity

将二元硫化物固体电解质75Li2S·24P2S5·1P2O5（LPOS）的非晶前驱体与三元硫化物电解质Li10GeP2S12（LGPS）前驱体按不同质量比均匀混合后,在270℃下进行烧结制备得到系列新型固体电解质材料 (1ω%)LPOS·ω%(t-LGPS)（ω=3、5、7、10）。当ω=5时,制得的新型固体电解质95%LPOS·5%(t-LGPS) 在室温下具有最佳的离子电导率1.0×103 S/cm。采用XRD、EIS、SEM等手段对该新型电解质材料的结构、形貌及电化学性能等进行了系统表征,并对电导率提高的机理进行了探讨。构建的全固态锂电池LiCoO2/95%LPOS·5%(t-LGPS)/Li表现出良好的电池性能,在25℃、0.1 C下,电池首周放电容量为115.7 mA·h/g,循环20圈后仍有80.38%的容量保持率。     

ZIF-8复合PEO基固态电解质的制备与改性研究北大核心CSCD

在聚环氧乙烷(PEO)基固体聚合物电解质中加入无机填料,是一种低成本、有效改善其力学和电化学性能的方法。为了更有效地改善PEO基固态电解质的电化学性能,本工作采用流延法制备了纳米沸石咪唑骨架材料(ZIF-8)与聚氧化乙烯(PEO)复合的固态电解质。通过扫描电子显微镜(SEM)、X射线衍射(XRD)等物理表征和电化学阻抗谱(EIS)、伏安线性扫描(LSV)、充放电循环等电化学测试手段,证明了加入20%ZIF-8纳米粒子的PEO基复合固态电解质CPE20具有最小的体电阻、较宽的电化学稳定窗口与最低的活化能(8.4×10^(-3)eV);20℃时,其电导率达到了4.9×10^(-5)S/cm(比纯PEO高一个数量级);70℃时,其电导率为1.08×10^(-3)S/cm(与液态电解液相当);CPE20的锂离子迁移数提高至0.46,而纯PEO基固态电解质为0.36;采用CPE20制备的LiFePO_(4)||Li电池在室温下具有良好的容量和循环性能,而且容量保持率超过96%。加入适量的惰性填料ZIF-8时,可以有效降低聚合物的结晶度,增加聚合物的非晶区,促进锂盐的溶解,提高锂离子的迁移率,使复合固态电解质具有更加优异的电化学性能。因此添加ZIF-8的PEO基固相聚合物在固态金属锂电池中具有广阔的应用前景。     

冠醚掺杂的聚合物固态电解质对全固态锂电池性能的影响北大核心CSCD

聚氧化乙烯(PEO)基固态电解质由于高的柔韧性、优异的加工性以及良好的界面兼容性等在全固态锂电池中极具应用前景,但其较低的室温离子电导率和较窄的电化学窗口限制了其高效应用。本工作采用溶液浇铸法将含有极性官能团的冠醚(15-C-5)分子分散在PEO/双三氟甲基磺酰亚胺锂(LiTFSI)基质中制备PEO/15-C-5聚合物固态电解质。重点探究冠醚含量对固态电解质中Li+传递的影响,同时对聚合固态电解质的形貌、力学性能、电化学性能进行系统研究。结果表明:10%15-C-5在PEO中分散性较好,可有效降低PEO的结晶度,进而提升PEO链段运动性,使其抗拉强度达1.83 MPa。15-C-5与锂离子间强的络合作用促进锂盐解离,同时对阴离子产生静电排斥,从而增强离子电导率并提高锂离子迁移数,30℃下离子电导率达到1.00×10^(-5)S/cm,60℃下锂离子迁移数达到0.42,分别是PEO电解质的4.5和1.9倍。另外冠醚与阴离子形成的静电排斥中心易捕获锂离子形成较为稳定的悬停位点,降低了PEO链段形成的O-Li络合活性位点促进C-O-C结构分解的可能性,从而提高PEO电解质的分解电压(从4.29 V到5.42 V)。与镍钴锰三元正极匹配的全固态锂电池展现出稳定的长循环性能,其在60℃、0.5 C的条件下初始放电比容量达到159 mAh/g,经100圈循环之后容量保持率达到89%。与磷酸铁锂正极匹配组装的全固态锂电池同样表现出优异的性能。     

PVDF-HFP基凝胶固态聚合物电解质的合成与锂离子电池性能

聚偏氟乙烯-六氟丙烯(PVDF-HFP)基凝胶聚合物电解质被认为是解决锂电安全性问题的一种有前途的固态电解质.然而,目前报道的是凝胶固态聚合物电解质由于含有大量易燃物质,安全性仍然无法保证.因此,本文合成制备基于PVDF-HFP的新型凝胶聚合物电解质,使用丁二腈(SN)作为塑化剂,双三氟甲基磺酰胺亚锂(LiTFSI)作为锂盐,利用热交联法原位制备了高热稳定性的新型凝胶固态聚合物电解质(GSPE).优化后的凝胶聚合物电解质离子电导率在25℃时可高达3.7×10?3 S/cm,电化学窗口室温下可达4.5 V.此外,凝胶聚合物电解质与电极具有良好的界面相容性;组装的磷酸铁锂电池在1 C下循环80次,容量保持率为89％.本项研究工作展示了高性能凝胶聚合物电解质对提升锂离子电池的循环稳定性与安全性具有较大潜在的应用价值.     

聚偏氟乙烯/聚偏氟乙烯磺酸锂/锂盐复合固态电解质的制备及其性能

以聚偏氟乙烯(PVDF)、氯磺酸和氢氧化锂等为原料制备了聚偏氟乙烯磺酸锂(SPVDFLi),将SPVDFLi与PVDF复合制得单离子聚合物电解质(SIPE).为进一步提高SIPE的电导率,向其添加双三氟甲烷磺酰亚胺锂(LiTFSI)制备双盐型聚合物复合电解质(SPVDFLi/LiTFSI-y),通过调控LiTFSI与聚合物的比例探究了双盐型聚合物电解质的电化学性能.结果表明:LiTFSI的添加有效提高了聚合物复合电解质的电导率.含40％LiTFSI的SPVDFLi/LiTFSI-40聚合物复合电解质室温电导率可达到1.41×10-4 S/cm,锂离子迁移数为0.68,稳定电压可以达到4.84 V.组装的LiFePO4/SPE/Li电池,0.2 C倍率下循环50圈后容量保持率为99.1％.该聚合物复合电解质有望用于制备高性能锂离子电池.     

固态锂离子传导氧化物中的点缺陷

固态电解质能有效地解决液态电解质存在的易燃、易泄漏及化学稳定性差等问题,然而,固态电解质的锂离子电导率（105～103 S/cm）显著低于液态电解质电导率（102 S/cm）,导致全固态锂离子电池的充放电性能比液态电池差。因此,进一步提高固态电解质的锂离子电导率成为改善全固态电池性能的关键,认知并调控材料中的点缺陷对于改善锂离子电导具有重要意义。本研究团队选用两种重要的固态锂离子传导氧化物材料：具有钙钛矿结构的Li3xLa2/3x□1/32xTiO3（0.04x0.16）和具有石榴石结构的Li7La3Zr2O12为研究对象,对其中存在的点缺陷及缺陷反应进行分析,并进一步阐述各种点缺陷对材料锂离子、氧离子和电子电导率的影响。     

锂盐对LAGP-PEO复合固体电解质及全固态LFP锂离子电池性能的影响

将Li1.5Al0.5Ge1.5(PO4)3（LAGP）与少量PEO(LiX)复合,采用溶液浇注法制备了以LAGP为主相的固体复合电解质,研究了LiClO4、LiTFSI、LiBOB 3种锂盐对固体复合电解质离子电导率、电化学稳定窗口、与锂负极界面的化学稳定性和电化学稳定性的影响以及锂盐种类对LFP固态电池循环及倍率性能的影响。研究结果表明,采用LiClO4、LiTFSI、LiBOB 3种锂盐制备的固体复合电解质分解电压均超过5 V,具有较好的电化学稳定性。LAGP-PEO(LiTSFI)固体复合电解质的离子电导率以及室温对锂界面的稳定性相对更高。LAGP-PEO (LiBOB)与锂的界面在60 ℃时相对更稳定。与之对应,采用LAGP-PEO(LiTSFI)和LAGP-PEO(LiBOB)固体复合电解质的LFP全固态电池,分别在25 ℃和60 ℃具有最高的比容量和最好的循环稳定性。     

新型固态聚合物电解质在锂硫电池中的性能研究

本工作采用（氟磺酰）（三氟甲基磺酰）亚胺锂{Li[(FSO2)(CF3SO2)N],LiFTFSI}和聚氧乙烯（PEO）分别作为导电锂盐和聚合物主链,通过简单的溶液浇铸法制备了新型固态聚合物电解质（SPEs）,并采取示差扫描量热（DSC）、热重（TGA）、线性扫描伏安（LSV）、交流阻抗（EIS）和恒电位直流（DC）极化等方法研究了LiFTFSI/PEO （EO/Li+摩尔比为16）电解质的理化性质和电化学性质。结果表明,LiFTFSI/PEO电解质具有较高的室温离子电导率（σ ≈10−5 S/cm）,较高的氧化电位（4.63 V vs. Li/Li+）,并且耐热温度高达256 ℃。锂硫电池测试结果表明,该类SPEs展现出相对高的首周放电比容量（881 mA•h/g）,有效地抑制了多硫离子的“穿梭效应”,表现出良好的电池循环性能。     

PEO基Li_(1.5)Al_(0.5)Ge_(1.5)(PO_4)_3固体复合电解质的制备

以聚环氧乙烷(PEO)为黏结剂,离子导电性的Li1.5Al0.5Ge1.5(PO4)3(LAGP)为主相,乙腈为溶剂,按照EO/Li,摩尔比为13,变化Li N(CF3SO2)2(Li TFSI)中Li+与LAGP中Li+的比例,通过溶液浇注法制备得到LAGP-PEO(Li TFSI)固体复合电解质。用X射线衍射、扫描电镜(SEM)和电化学阻抗(EIS)等方法对固体复合电解质的形貌、结构和电导率进行表征。结果表明,LAGP可与PEO(Li TFSI)部分络合并均匀分散于PEO(LITFSI)内,整个体系内存有三个主体相,即PEO(Li TFSI)的复合相、LAGP晶相以及PEO与两种锂盐的过渡相。通过阻抗谱图发现,当质量比w(LAGP)∶w(PEO)=6∶4时,LAGP-PEO(Li TFSI)固体复合电解质具有最高的室温电导率,为2.68×10?5 S/cm,在333 K时,达到1.86×10?4 S/cm,接近LAGP的电导率水平。这说明固体复合电解质中加入LAGP即降低了PEO的结晶度,LAGP自身的电导率也有一定贡献。     

Simultaneously enhancing the thermal stability and electrochemical performance of solid polymer electrolytes by incorporating rod-like Zn2(OH)BO3 particles

Solid polymer electrolytes provide high safety and good electrochemical stability in solid-state lithium batteries (SSLBs) compared with conventional liquid electrolytes. In this work, a novel solid polymer composite electrolyte based on poly (ethylene oxide) (PEO) filled with rod-like Zn₂(OH)BO₃ particles was prepared by a grinding process followed with a heating treatment process and a cold pressing process. The effect of the incorporation amount of rod-like Zn₂(OH)BO₃ particles on the ionic conductivity was investigated systemically. It is found that 10 mol% of rod-like Zn₂(OH)BO₃ particles addition resulted in a highest ionic conductivity of 2.78 × 10⁻⁵ at 30 °C and the improved ionic conductivity was considered to be caused by the reducing of PEO crystallinity and the increasing of Li ion migrating pathway on the interface between the Zn₂(OH)BO₃ and PEO. In addition, the optimum composite electrolyte exhibited a high electrochemical stability window of 4.51 V (vs. Li/Li⁺), good lithium stability and excellent thermal stability.     

Electrochemical performance of lithium ion capacitors using high-capacitance Li2NiO2/AC as the negative electrode

兼具锂离子电池高能量密度和双电层电容器高功率特性的锂离子电容器成为了现今超级电容器性能提升的重点发展方向。本工作以高富锂金属氧化物Li2NiO2为锂离子电容器用负极锂源,将其与活性物复合组成正极电极,并制备出“无金属锂片”预嵌锂过程的300 F锂离子电容器,考察了金属氧化物Li2NiO2的理化性能与电化学特性、不同Li2NiO2添加量对锂离子电容器样品的电化学性能影响。结果表明,Li2NiO2材料具有398 mA·h/g的首次不可逆容量,首次放电不可逆率为94.8%。添加15%～20% Li2NiO2的样品在10 A电流下具有大于75%倍率特性以及91%的容量保持率。当Li2NiO2添加量为20%时,样品在1 A条件下具有400 F的容量,15.5 W·h/kg的能量密度以及11.3 kW/kg的功率密度,是一种制备工艺简单、性能优异的新型锂离子电容器。     

PEO/PS/PMMA聚合物电解质膜的制备及性能研究

聚合物电解质是解决锂离子电池安全性问题的有效途径之一。考察了由聚环氧乙烷(PEO)、聚苯乙烯(PS)、聚甲基丙烯酸甲酯(PMMA)、聚乙二醇(PEG)和双三氟甲烷磺酰亚胺锂盐(LiTFSI)组成的固体聚合物电解质膜的性能。采用聚合物共混技术制备了一系列复合聚合物电解质膜,通过扫描电子显微镜(SEM)和X射线衍射(XRD)对膜的形态和晶体结构进行了分析,并详细考察了离子电导率、孔隙率和吸液率等性能。PS和PMMA的加入降低了PEO的结晶度,提高了它的拉伸强度。结果表明,当PEO/PS/PMMA膜中各组成质量比为75:10:15时,聚合物电解质膜具有优良的性能,膜的离子电导率为3.56×10^-4S·cm^-1,拉伸强度为11.56MPa,孔隙率达到57.6%,吸液率高达164.3%。     

Ionic liquid doped PEO-based solid polymer electrolytes for lithium-ion polymer batteries

The influence of adding the room-temperature ionic liquid 1-ethyl-3-methyllimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) to poly(ethylene oxide) (PEO)–lithium difluoro(oxalato)borate (LiDFOB) solid polymer electrolyte and the use of these electrolytes in solid-state Li/LiFePO₄ batteries has been investigated. Different structural, thermal, electrical and electrochemical studies exhibit promising characteristics of these polymer electrolyte membranes, suitable as electrolytes in rechargeable lithium-ion batteries. The crystallinity decreased significantly due to the incorporation of ionic liquid, investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The ion–polymer interaction, particularly the interaction of cations in LiDFOB and ionic liquid with ether oxygen atom of PEO chains, has been evidenced by FT-IR studies. The polymer electrolyte with ～40 wt% of ionic liquid offers a maximum ionic conductivity of ～1.85 × 10^?4 S/cm at 30 °C with improved electrochemical stabilities. The Li/PEO-LiDFOB-40 wt% EMImTFSI/LiFePO₄ coin-typed cell cycled at 0.1 C shows the 1st discharge capacity about 155 mAh g^?1, and remains 134.2 mAh g^?1 on the 50th cycle. The addition of the ionic liquid to PEO₂₀-LiDFOB polymer electrolyte has resulted in a very promising improvement in performance of the lithium polymer batteries.     

Enhanced electrochemical properties of PEO-based composite polymer electrolyte with shape-selective molecular sieves

ZSM-5 molecular sieves, usually known as shape-selective catalyst in a great deal of catalysis fields, due to its special pore size and two-dimensional interconnect channels. In this work, a novel PEO-based composite polymer electrolyte by using ZSM-5 as the filler has been developed. The interactions between ZSM-5 and PEO matrix are studied by DSC and SEM techniques. The effects of ZSM-5 on the electrochemical properties of the PEO-based electrolyte, such as ionic conductivity, lithium ion transference number, and interfacial stability with lithium electrode are studied by electrochemical impedance spectroscopy and steady-state current method. The experiment results show that ZSM-5 can enhance the ionic conductivity and increase the lithium ion transference number of PEO-based electrolyte more effectively comparing with traditional ceramic fillers such as SiO₂ and Al₂O₃, resulting from its special framework topology structure. The excellent performances such as high ionic conductivity, good compatibility with lithium metal electrode, and broad electrochemical stability window suggesting that PEO–LiClO₄/ZSM-5 composite polymer electrolyte can be used as candidate electrolyte materials for lithium polymer batteries.     

Ionanofluid plasticized electrolyte with improved electrical and electrochemical properties for high-performance lithium polymer battery

Herein, the electrochemical characteristics of Li/LiFePO₄ battery, comprising a new class of poly (ethylene oxide) (PEO) hosted polymer electrolytes, are reported. The electrolytes were prepared using lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) dopant salt and imidazolium ionic liquid-based nanofluid (ionanofluid) as the plasticizer. Morphological, thermophysical, electrical, and electrochemical properties of these newly developed electrolytes were studied. Using FT-IR spectroscopy, the interactions between dopant salt plasticizers and the host polymer, within the electrolytes, were evaluated. The optimized 30 wt% ionanofluid plasticized electrolyte exhibits a room temperature ionic conductivity of 6.33 × 10⁻³ S cm⁻¹, wide electrochemical voltage window (~4.94 V vs Li/Li⁺) along with a moderately high value of lithium-ion transference number (0.47). The values are substantially higher than that of similar wt% IL plasticized electrolyte (7.85 × 10⁻⁴ S cm⁻¹, ~4.44 V vs Li/Li⁺ and ~ 0.28, respectively). Finally, the Li/LiFePO₄ battery, comprising optimized 30 wt% ionanofluid plasticized electrolyte, delivers 156 mAh g⁻¹ discharge capacity at 0.1 C rate and able to retain its 92% value after 50 cycles. Such a superior battery performance as compared to the IL plasticized electrolyte cell (137 mAh g⁻¹ and 84% after 50 cycles at the same current rate) would endow this ionanofluid a very promising plasticizer to develop electrolytes for next-generation lithium polymer battery.