铁系纳米材料的结构稳定性对锂离子电池长循环性能的影响

Much longer cycle life means lesser resource consumption for energy storage materials. And the durability of structures is the prior factor that influence the long-term cycles in lithium ion batteries (LIB). The project focuses on three routes to achieve highly stable nanostructure or reduce the destruction of nanostructures, i.e., synthesizing asymmetric nanostructures (bowl-like structure etc.) with open internal and external surfaces, combining iron group nanomaterials with carbon in various dimensions (carbon QDs, CNTs and reduced graphene oxide sheets), and fabricating direct electrode nanomaterials. Through the characterizations on components, structures, and interfaces of the active electrode materials during their long-term cycling processes, the main reason will be revealed for structure damages in the charge and discharge of LIB, which can be used to arrange designs of stable nanostructures. Based on analyzing the preliminary and the second characterizations after cycling on the electrode nanomaterials as well as the electrochemical properties, the interior relationship of the structure durability and long-term cycling life of the batteries will be summarized and provide theoretical supports for the design of electrode nanomaterials with excellent electrochemical properties.

就储能材料而言，更长的循环寿命意味着更少的资源消耗。而材料的结构稳定性是影响锂离子电池长循环性能的第一要素。本项目通过合成具有开放内外表面的碗状等非对称结构的纳米材料，构造复合电极材料实现高稳纳米结构或减少电极循环过程中纳米结构的损失，得到具有优异电化学性能的铁系纳米电极材料。通过对长循环过程中材料的成分、结构、界面等进行表征，揭示电池充放电过程对纳米结构损害的主要因素，指导材料的设计合成。结合电极材料的初步表征、电化学性能与循环完成后的二次表征结果，总结结构的稳定性与电池长循环性能间的内在联系，为优异性能纳米电极材料的结构设计提供理论依据。

铁系纳米材料作为电池电极材料具有高的比容量，但长循环稳定性差、电导率低。针对上述问题，本项目通过设计特殊纳米结构辅以界面调控，构造了纳米碗、三明治结构、超薄碳层稳定的量子点等高稳纳米结构，使其能承受嵌脱锂过程产生的应力作用，进而实现了优异的长循环性能。同时，界面复合引入的石墨烯、超薄碳层等材料有效地减少了电极材料中电子/离子传输路径，提高了电子/离子传输效率，使得材料具有优异的比容量与倍率性能。如1 A/g倍率下，三明治型CoO/C纳米片电极的可逆容量在1200次超长循环后依然达到864.8 mA h/g，具有100 %的库伦效率，其容量保持率高达~100 %。并且通过对材料的形貌成分表征、电化学表征结合模拟计算，建立构效关系，为高效纳米电极材料的结构设计提供理论依据。