新型聚碳酸酯设计合成及构建有序复合固态电解质性能研究

All-solid-state lithium batteries have been drawn extensive attention in the past few year due to their unique characteristics of higher safety characteristics and higher energy density when compared with the traditional non-aqueous liquid lithium ion batteries. Very recently, it is demonstrated that polycarbonate-based solid polymer electrolytes have an advantage of higher ionic conductivity at ambient temperature and superior electrochemical stability over the conventional polyether-based solid polymer electrolytes. So, in this proposal a series of novel polycarbonates will be designed and synthesized using the renewable epoxy and carbon dioxide as starting materials. The highly ordered ceramic/polycarbonate based composite solid electrolytes will be prepared via some compositing 3D structural modulation strategies. Their electrochemical properties will be studied including the electrochemical stability windows, ionic conductivity and lithium ion transference number. Furthermore, the underlying ion diffusion mechanism and dynamics will be investigated. In addition, their electrochemical stability against oxidation and reduction on the surfaces of high voltage cathode and lithium foil anode will be discussed respectively, and the interphase components and its forming paths will be interpreted. The coin cells and pouch batteries will be assembled using the optimized ceramic/polycarbonate as solid polymer electrolyte. The battery performance such as charge/discharging capacity, rate capability, cycling capacity and safety issues will be evaluated as well as the failure mechanism. In conclusion, this proposal aims at providing some valuable guideline for developing superior polycarbonates-based solid polymeric electrolytes and for designing high performance solid state batteries.

最新初步研究表明，与传统聚乙二醇基固态电解质体系相比，聚碳酸酯基固态电解质具有室温离子电导率高和电化学稳定窗口宽等优势，因此有希望通过系统深入研究来进一步提高其综合性能。本项目拟设计合成不同结构特征的新型聚碳酸酯，并采用特定结构调控方法（如电场诱导排列取向法等）与无机陶瓷粒子有序“复合”构建3D快速离子通道网络，制备成高性能聚碳酸酯复合固态聚合物电解质。研究复合电解质多级结构（如微观尺度，介观尺度和宏观尺度）与锂离子输运和电极界面稳定性能之间的构效关系；深入研究新型聚碳酸酯复合固态电解质可能的锂离子传输机理及动力学行为；重点研究与高电位正极材料，与锂金属负极材料以及与铝集流体之间的界面相容性和稳定性，并探讨界面层可能的组成及形成途径；揭示聚碳酸酯电解质体系与固态电池充放电、倍率、长循环及安全性能以及失效原因等方面的内在关系；为开发高能量密度的聚碳酸酯固态锂电池提供重要的参考依据。

采用固态电解质代替液态电解质有望显著提升锂离子电池安全性能。与传统聚乙二醇基固态电解质体系相比，聚碳酸酯基固态电解质具有室温离子电导率较高和电化学稳定窗口宽等优势。本项目设计合成了一系列新型的聚碳酸酯聚合物，并采用一定手段与无机陶瓷粒子有序“复合”构建3D 快速离子通道网络，制备成高性能聚碳酸酯复合固态聚合物电解质。从微观尺度和宏观尺度等研究了锂离子输运和电极界面稳定性能之间的构效关系，进一步优化设计得到高离子电导率和宽电化学稳定窗口的聚碳酸酯固态电解质。取得的重要结果包括：（1）提出了一种用于室温锂电池的聚碳酸乙烯酯（PVCA）/丁二腈（SN）准固态复合聚合物电解质，其中塑晶型丁二腈（SN）作为多功能组分以提高离子电导率。所制备的PVCA-SN聚合物电解质的室温离子电导率高达为4.5x10–4 S/cm（25℃时）。基于PVCA-SN电解质的组装锂离子电池在室温下表现出优异的充放电性能。（2）开展了乙烯基碳酸乙烯酯/聚二氧戊烷共聚型固态电解质的设计合成及性能研究。聚1,3-二氧戊烷（PDOL）具有较高的氧原子含量，因此在理论上应具有较高的离子导电性和电化学性能。本研究采用端基引入不饱和双键的策略与乙烯基碳酸乙烯酯共聚的方法来提高聚碳酸酯的室温离子电导率和改善聚二氧戊烷基固态电解质的热稳定性。引入双键后可以自交联成膜或采用原位聚合方法制备固态电解质膜，以满足固态聚合物易加工的需求。（3）构筑无机/有机有序复合的固态电解质体系。采用高压同轴静电纺丝法制备Li0.33La0.557TiO3中空纳米管，并复合聚碳酸亚乙酯聚合物电解质，使其室温离子电导率大幅增强。（4）发展了一系列的巯基-丙烯酸酯点击反应原位高效生成高性能固态聚合物电解质的方法。（5）发现ALD法精准纳膜包覆正极材料可大幅提高聚合物电解质/电极界面的循环稳定性。（6）初步开展了聚合物全固态电池安全性及其热失控行为研究。