Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, WA 99352, USA.
Institute of Microstructure and Properties of Advanced Materials, Beijing University of Technology, No. 100, Pingleyuan, Chaoyang District, Beijing, 100124, PR China.
Nat Commun. 2018 Jun 22;9(1):2437. doi: 10.1038/s41467-018-04862-w.
Electrochemically driven functioning of a battery inevitably induces thermal and mechanical effects, which in turn couple with the electrochemical effect and collectively govern the performance of the battery. However, such a coupling effect, whether favorable or detrimental, has never been explicitly elucidated. Here we use in situ transmission electron microscopy to demonstrate such a coupling effect. We discover that thermally perturbating delithiated LiNiMnCoO will trigger explosive nucleation and propagation of intragranular cracks in the lattice, providing us a unique opportunity to directly visualize the cracking mechanism and dynamics. We reveal that thermal stress associated with electrochemically induced phase inhomogeneity and internal pressure resulting from oxygen release are the primary driving forces for intragranular cracking that resembles a "popcorn" fracture mechanism. The present work reveals that, for battery performance, the intricate coupling of electrochemical, thermal, and mechanical effects will surpass the superposition of individual effects.
电池的电化学驱动作用不可避免地会引起热和机械效应，这些效应反过来又与电化学效应耦合，并共同决定电池的性能。然而，这种耦合效应（无论是有利的还是不利的）从未被明确阐明。在这里，我们使用原位透射电子显微镜来证明这种耦合效应。我们发现，对脱锂的 LiNiMnCoO 进行热扰动会引发晶格内颗粒内裂纹的爆炸性成核和扩展，这为我们提供了一个独特的机会，可以直接观察到裂纹的形成机制和动力学。我们揭示了与电化学诱导的相不均匀性和由于氧释放而产生的内部压力相关的热应力是导致颗粒内裂纹的主要驱动力，这种裂纹类似于“爆米花”断裂机制。本工作揭示了，对于电池性能而言，电化学、热和机械效应的复杂耦合作用将超过各单独效应的叠加。
