In-situ scanning electron microscopy (SEM) has emerged as a powerful tool for studying real-time battery degradation mechanisms. Unlike ex-situ methods, which analyze samples after cycling, in-situ SEM enables direct observation of dynamic processes such as dendrite growth, electrode cracking, and solid-electrolyte interphase (SEI) layer formation under operational conditions. This capability provides critical insights into failure modes and material behaviors that are otherwise difficult to capture.

One of the primary applications of in-situ SEM is observing lithium dendrite formation during cycling. Dendrites, which grow as needle-like structures on the anode surface, are a major cause of battery short circuits and capacity loss. By integrating a miniature electrochemical cell within the SEM chamber, researchers can monitor dendrite nucleation and propagation in real time. The setup typically involves a lithium metal anode, a liquid or solid electrolyte, and a counter electrode, all housed in a specialized sample holder that maintains electrical contact while allowing electron beam penetration. High-resolution imaging reveals dendrite morphology, growth rates, and interactions with the electrolyte. Challenges include preventing beam-induced artifacts and maintaining stable imaging conditions despite the dynamic nature of dendrite evolution.

Electrode cracking is another degradation mechanism studied using in-situ SEM. Repeated lithiation and delithiation during cycling induce mechanical stress in electrode materials, leading to fracture and capacity fade. For example, silicon anodes, which undergo significant volume expansion, are prone to cracking. In-situ setups for this purpose often employ a half-cell configuration with the electrode material deposited on a conductive substrate. The SEM captures real-time images as the electrode cycles, showing crack initiation and propagation. Quantitative analysis of crack patterns and strain distribution helps correlate mechanical degradation with electrochemical performance. A key technical challenge is ensuring the sample holder accommodates the electrode’s volume changes without introducing external stresses that could skew results.

SEI layer formation is also investigated using in-situ SEM. The SEI layer, which forms on the anode surface during initial cycles, plays a critical role in battery stability but can also contribute to impedance growth if uneven or excessively thick. By cycling a battery inside the SEM, researchers observe SEI nucleation, growth, and evolution at the nanoscale. The technique reveals inhomogeneities in SEI composition and thickness, as well as dynamic changes during cycling. However, SEI studies face unique challenges due to the layer’s sensitivity to electron beams and vacuum conditions. Some setups use a protective window or low-voltage imaging to minimize beam damage, while others employ environmental SEM (ESEM) to introduce controlled gas pressures that mimic realistic battery environments.

Technical challenges in in-situ SEM for battery studies are significant. The high-vacuum environment of conventional SEMs is incompatible with liquid electrolytes, necessitating creative solutions such as solid electrolytes, ionic liquids, or sealed liquid cells with electron-transparent membranes. Even with these adaptations, beam interactions can alter sample chemistry or introduce imaging artifacts. Sample holder design is equally critical; it must provide electrical connections, mechanical stability, and compatibility with the SEM stage while minimizing interference with the electron beam. Thermal management is another consideration, as localized heating from the beam or electrochemical reactions can affect degradation kinetics.

Despite these challenges, in-situ SEM offers unparalleled insights into battery degradation. For example, studies have captured dendrite penetration through separators, identified critical stress thresholds for electrode fracture, and documented SEI growth dynamics under varying cycling conditions. These observations inform material design, such as developing dendrite-suppressing electrolytes or strain-tolerant electrode architectures. Future advancements may involve coupling in-situ SEM with other techniques like energy-dispersive X-ray spectroscopy (EDS) for compositional analysis or atomic force microscopy (AFM) for mechanical property mapping during cycling.

In summary, in-situ SEM is a transformative tool for understanding real-time battery degradation. By enabling direct observation of dendrite growth, electrode cracking, and SEI formation, it bridges the gap between electrochemical performance and material behavior. While technical hurdles remain, ongoing innovations in sample preparation, holder design, and imaging protocols continue to expand its capabilities. As battery technologies advance toward higher energy densities and longer lifetimes, in-situ SEM will play an increasingly vital role in uncovering and mitigating degradation mechanisms.