锂氧电池阴极分级纳米多孔金失效分析

Failure analysis on rechargeable Li⁃O_(2) battery with hierarchical nanoporous Au cathode

锂氧电池具有很高的理论比容量,作为锂离子电池的潜在高能替代品引起研究者极大兴趣。而阴极材料的选择和优化是提高锂氧电池性能的有效手段。为此,本文作者制备了可以同时实现高孔隙率和大比表面积的分级纳米多孔金(h⁃NPG),以此为阴极的锂氧电池展现出了优异的性能。而阻碍锂氧电池达到高理论比容量的一个重要原因是,电绝缘的放电产物过氧化锂(Li_(2)O_(2))会使电池阴极钝化,导致电池的容量迅速衰减和充放电循环次数降低。因此本文利用透射电镜(TEM)和电子能量损失谱(EELS)精准表征了锂氧电池阴极h⁃NPG在充放电过程中过氧化锂(Li_(2)O_(2))产物的微观结构演化,进而分析了Li_(2)O_(2)对阴极分级纳米孔道的影响,为新型阴极多孔材料提供了优化设计思路与失效判据。

Lithium⁃oxygen(Li⁃O_(2))batteries have attracted great attention due to their high theoretical specific capacity.They have been considered as the potential candidate for replacing lithium⁃ion batteries.However,the lithium peroxide(Li_(2)O_(2))as the discharge product of electrical insulation can passivate cathodes,and lead to the rapid attenuation of battery capacity and the reduction of charge⁃discharge cycles.To improve the performance of Li⁃O_(2) batteries,one of the effective ways is to select and optimize cathode materials of Li⁃O_(2) batteries,and to study the effect of Li_(2)O_(2) on the microstructure of cathodes.In this work,we used hierarchical nanoporous gold(h⁃NPG)with high porosity and surface⁃to⁃volume ratio as cathode materials.Transmission electron microscopy(TEM)and electron energy loss spectroscopy(EELS)techniques were employed to accurately characterize the microstructure evolution of Li_(2)O_(2) products during charging and discharging of the h⁃NPG cathode in Li⁃O_(2) batteries.Based on these characterizations,we can further explore the effect of Li_(2)O_(2) on the gradient nanopores of h⁃NPG cathodes,thus building the relation between Li_(2)O_(2) products and the microstructures of cathodes to reveal the potential failure mechanism.This work provides an efficient way for the optimized design and the failure criteria for new cathode porous materials.