A new review of single-ion conducting polymer electrolytes in the light of ion transport mechanisms

With the depletion of fossil fuels and the demand for high-performance energy storage devices,solidstate lithium metal batteries have received widespread attention due to their high energy density and safety advantages.Among them,the earliest developed organic solid-state polymer electrolyte has a promising future due to its advantages such as good mechanical flexibility,but its poor ion transport performance dramatically limits its performance improvement.Therefore,single-ion conducting polymer electrolytes(SICPEs)with high lithium-ion transport number,capable of improving the concentration polarization and inhibiting the growth of lithium dendrites,have been proposed,which provide a new direction for the further development of high-performance organic polymer electrolytes.In view of this,lithium ions transport mechanisms and design principles in SICPEs are summarized and discussed in this paper.The modification principles currently used can be categorized into the following three types:enhancement of lithium salt anion-polymer interactions,weakening of lithium salt anion-cation interactions,and modulation of lithium ion-polymer interactions.In addition,the advances in single-ion conductors of conventional and novel polymer electrolytes are summarized,and several typical highperformance single-ion conductors are enumerated and analyzed in what way they improve ionic conductivity,lithium ions mobility,and the ability to inhibit lithium dendrites.Finally,the advantages and design methodology of SICPEs are summarized again and the future directions are outlined.

Novel single-ion conducting polymer electrolytes with high toughness and high resistance against lithium dendrites

Solid-state polymer electrolytes are considered as an alternative to classic liquid electrolytes,particularly for application in highenergy lithium metal batteries.With respect to common dual-ion conductors,single-ion conducting polymer electrolytes(SICPEs)are less affected by lithium dendrites growth and thus are particularly interesting for application in lithium metal batteries.In this work,novel SIC-PEs are developed,based on an ionomer having poly(ethylene-alt-maleimide)backbone and lithium phenylsulfonyl(trifluoromethanesulfonyl)imide pendant moieties,further blended with poly(ethylene oxide)(PEO)and poly(ethylene glycol)dimethyl ether(PEGDME).These SIC-PEs exhibit ionic conductivity around~7×10^(−6)S·cm^(−1) at 70℃,lithium transference number close to unity,and excellent mechanical properties,with fracture toughness over 30 J·cm^(−3).Additionally,the electrolytes show very high resistance against lithium dendrites growth,by cycling for more than 1200 h in Li°symmetric cells at a current density of 0.1 mA·cm^(−2).LiFePO4||Li°cells with these SIC-PEs were cycled at 70℃ and C/10,showing initial capacity of almost 160 mAh·g^(−1)and residual capacity of 45%after 100 cycles.This work shows that single-ion conducting polymer electrolytes based on poly(ethylene-alt-maleimide)backbone are promising materials for application as electrolytes or catholytes in lithium metal polymer batteries.

A hybrid lithium sulfonated polyoxadiazole derived single-ion conducting gel polymer electrolyte enabled effective suppression of dendritic lithium growth

Lithium metal is deemed as an ideal anode material in lithium-ion batteries because of its ultrahigh theoretical specific capacity and the lowest redox potential.However,the rapid capacity attenuation and inferior security resulting from the dendritic lithium growth severely limit its commercialization.Herein a novel hybrid gel polymer electrolyte (GPE) based on electrospun lithium sulfonated polyoxadiazole (LiSPOD) nanofibrous membrane swelled by lithium bis(trifluoromethanesulfonyl)imide (Li TFSI) ether liquid electrolyte is proposed to address the issue of lithium dendrites.The Li-SPOD membrane synthesized by a simple one-pot method exhibits excellent mechanical strength and thermal resistance due to its high molecular weight and rigid backbone.The electron-withdrawing oxadiazole ring and oxadiazole ring-Li;complex,and N,O heteroatoms with lone pairs of electrons in Li-SPOD macromolecular chains facilitate the dissociation of-SO_(3)Li group and Li^(+)transference.The hybrid Li-SPOD GPE exhibits both a high lithium-ion transference number (0.64) and high ionic conductivity (2.03 m S/cm) as well as superior interfacial compacity with lithium anodes.The Li Fe PO_(4)-Li cell using this novel GPE can operate steadily at 2C for 300 cycles,remaining a high discharge capacity of 125 m Ah/g and dendrite-free anode.Remarkable performance improvements for the Li-Li and Cu-Li cells are also presented.

磺酸型聚氨酯离聚物的离子导电性能

本文以多种聚醚为软段，二异氰酸酯（ＭＤＩ和ＴＤＩ）为硬段，合成了多嵌段聚醚聚氨酯，以此聚氨酯为基材，与ＮａＨ及１，３－丙碳酸内酯反应，进一步合成了一系列不同离子化程度的阴离子型碳化聚氨酯离聚物，用交流阻抗谱仪测定了样品的阻抗谱，由此计算出样品的离子电导率。研究结果表明其他条件相同时，以聚乙二醇（ＰＥＧ）为软段的样品具有较高的离子电导率；以聚环氧丙烷（ＰＰＯ）为软段的样品次之，以聚四氢呋喃（ＰＴＭＯ）为软段的样品最低，对于离子化程度不同的聚氨酯离聚物以金属离子和烷氧单元之比为０．０５时导电性能最好。阳离子为Ｌｉ＋和Ｎａ＋的样品具有相近的离子电导率。