基于高弹多孔隔膜的呼吸型硅碳负极锂电池的构筑与性能优化

The main challenges for silicon anode are the large volume change during the lithiation/delithiation process and the instability of the solid- electrolyte-interphase (SEI) associated with this process. This project aims to prepare a “breathable” silicon/carbon anode lithium battery by the use of highly elastic porous membrane. Different kinds of elastic separators will be designed and the relationship between the volume changes and stress of them will be studied based on the study model of the structure, volume changes and stress relationship. The battery volume change and its influencing factors will be studied by using the porosity and thickness testing technology. The volume change of silicon-based lithium battery during the lithiation/delithiation process can be remedied by the separator and the safety of silicon/carbon anode lithium battery will be improved as the breakage of battery package caused by the electrode swelling is consequently prevented. And by controlling the interface stress between the separator and the electrode, containing the expansion of the electrode to ensure a good contact with the separator, the interface resistance of the battery can be reduced as well, and the silicon is firmly contacted with the conductive network, thus to improve the performance of the battery. The influence mechanism of the interface stress on the performance of batteries and the formation of SEI will be studied systematically to build a theoretical system and the preparation of silicon/carbon anode lithium battery will be guided. The implementation of this project provides a new way for the development of silicon/carbon anode lithium battery, which is expected to provide important references for the performance and safety improvement of silicon/carbon anode lithium battery.

硅材料理论比容量高、嵌锂平台较低，成为高容量锂电池研究的热点，但是充放电过程中巨大体积变化导致的容量衰减以及固体电解质膜（SEI）不稳定等问题，限制了硅基锂电池的发展。本项目拟以带有压敏元件的模拟电池为主要实验手段，以弹性材料改性、隔膜构建以及硅碳复合负极的制备为基础，研究隔膜及其与电极间的界面应力对硅碳负极锂电池性能的影响机制及作用机理。具体思路为：宏观方面，研究弹性隔膜形变与应力的关系，结合硅碳负极锂电池体积变化率的研究，实现充放电过程中体积恒定的呼吸型硅碳负极锂电池的构筑；微观方面，通过添加压敏元件改造模拟电池，调控隔膜结构并固定电池的工作空间，量化界面应力对硅碳负极锂电池性能的影响机制，揭示界面应力与SEI膜形成及变化的内在联系，形成理论体系指导硅碳负极锂电池的研发。本项目的实施，为硅碳负极锂电池的研究提供了新的思路，有望在硅碳负极锂电池的性能优化和安全性提高等方面提供重要的借鉴。

摘要：高的体积变化以及其造成的材料粉化、SEI不断再生、电解液持续消耗以及电极与隔膜界面脱离接触成为硅碳材料所面对的主要难题。利用弹性隔膜的体积变化协同材料在充放电过程中的体积变化，防止界面脱离接触。与此同时，利用弹性隔膜提供的界面应力，有效保持材料的有效接触，助力强韧性SEI膜的形成，有效提高电池的性能。这些研究结果对于提升高体积变化的电极材料性能具有十分重要的意义。具体研究成果分为以下3个方面：1）机械应力对电池性能的影响及作用机理。2）弹性隔膜的制备及电池性能的优化。3）弹性隔膜在其他电池体系中的应用。项目执行期在Nano research, Materials today energy, polymers 以及化工学报发表论文5篇，其研究结果为通过隔膜提升硅碳电池的性能提供了实验依据和理论指导。