Application of spin-echo small angle neutron scattering to study cycling degradation from dendrite growth in lithium-ion batteries

Abstract:
On a global scale the demand for Lithium-ion batteries is facing a rapid escalation fuelled by a number of areas such as electric vehicles, renewable energy storage systems, and consumer electronics. In order to meet these demands current battery technology needs to dramatically improve especially in areas such as overall lifetime and degradation on cycling. However, it is difficult to study the degradation and failure mechanisms in-situ and in-operando and as a result most structural analysis is carried out post mortem using traditional microscopy techniques. These techniques fail to capture the development of the structure and suffer from both a small sample size and limited field of view. Previous work has shown that by developing an in-situ and in-operando cell compatible with small-angle neutron scattering we are able to capture small changes in the lithium morphology indicating dendrite growth. However, the results indicated the presence of larger structures outside the measured q range. To build on this work and further our understanding of dendrite growth, which plays an important role in battery degradation and failure, we propose to use spin-echo small angle neutron scattering which benefits from a much larger length scale range, up to 25 um, to characterise morphology in lithium-ion batteries over repeated cycling.

摘要：全球层面，受电动汽车、可再生能源储能系统及消费电子等多个领域驱动，锂离子电池（Lithium-ion batteries）的需求正快速攀升。为满足此类需求，当前电池技术亟需实现大幅提升，尤其是在整体循环寿命与循环降解性能等方面。然而，在原位（in-situ）与在线原位（in-operando）条件下研究降解与失效机制颇具难度，因此绝大多数结构分析均采用传统显微技术在电池退役后开展。此类技术无法捕捉结构的动态演化过程，且存在样本量偏小、视场范围受限的缺陷。既往研究表明，通过研发适配小角中子散射（small-angle neutron scattering）的原位与在线原位电池，我们能够捕捉到预示锂枝晶生长的锂形貌细微变化。但结果显示，在实测散射矢量q区间之外存在更大尺寸的结构。为延续此项研究并深化对锂枝晶生长的认知——锂枝晶生长在电池降解与失效过程中发挥着重要作用——我们提出采用自旋回波小角中子散射（spin-echo small angle neutron scattering）开展研究，该技术具备更宽的长度尺度探测范围，最高可达25微米，可对经过多次循环的锂离子电池的形貌进行表征。