Multiscale correlative imaging reveals sequential and heterogeneous degradations in fast-charging batteries

Abstract

Fast-charging lithium-ion batteries provide a promising solution to address the range anxiety of electric vehicles (EVs) but they face challenges in terms of durability and safety. Kinetically-driven lithium-plating on the anode is widely considered as a major bottleneck and has dominated the research attention so far. Here we develop lengthscale-bridging, multimodal SEM-Raman-NanoSIMs techniques to understand the complex chemical–structural–mechanical interplays within fast-charging batteries. Statistical understanding from multiple-particle analysis at the electrode-level is obtained for the first time. Electrolyte depletion is found to be the first domino to fall (even when the capacity fade is still trivial), which triggers a wide range of anode failures including the lithium plating and byproduct accumulation. The cathode remains relatively healthy early on but does exhibit increasing heterogeneity in lithium concentration, particle fracture behaviors, and lattice-structure disorder as the batteries cycle. These complex electro–chemo–mechanical interplays trigger self-amplifying “vicious circles” and cause severe electrode distortion and even rupture inside the batteries, which become hidden safety threats. This work provides new perspectives and useful insights for developing better fast-charging batteries.