Silicon-based anode materials face significant challenges when operating under high-temperature conditions, with performance degradation primarily driven by accelerated solid electrolyte interphase (SEI) layer evolution, exacerbated particle cracking, and irreversible capacity loss. These issues stem from silicon's intrinsic material properties, including its large volume expansion and high reactivity with electrolytes. Understanding these failure mechanisms and developing targeted stabilization strategies is critical for enabling reliable high-temperature operation in advanced battery systems.

At elevated temperatures, the SEI layer on silicon anodes undergoes rapid and unstable growth. The SEI forms through reductive decomposition of electrolyte components, a process that accelerates with increasing temperature due to enhanced kinetics of side reactions. Conventional carbonate-based electrolytes decompose more readily at high temperatures, forming a thicker and more resistive SEI layer. This layer consists of inorganic components such as LiF and Li2CO3 near the silicon surface, with organic compounds like lithium alkyl carbonates in outer regions. The continuous SEI growth consumes active lithium and electrolyte while increasing interfacial resistance, leading to capacity fade and power loss. Unlike graphite anodes where the SEI may stabilize, silicon's volume changes during cycling cause SEI fracture and reformation, creating a positive feedback loop of degradation.

Particle cracking represents another major failure mode under thermal stress. Silicon experiences approximately 300% volume expansion during full lithiation, generating substantial mechanical stresses. At higher temperatures, these stresses combine with thermal expansion effects to accelerate particle fracture. The expansion mismatch between silicon and common conductive additives or binders becomes more pronounced with temperature, leading to loss of electrical contact within the electrode. Crack formation exposes fresh silicon surfaces to electrolyte, triggering additional SEI formation and further lithium inventory loss. The combination of thermal and cycling stresses causes progressive pulverization of silicon particles, ultimately destroying the electrode's structural integrity.

Performance degradation pathways manifest through several measurable parameters. Capacity fade occurs through both active material loss and lithium inventory depletion. Coulombic efficiency drops significantly at high temperatures due to increased parasitic reactions. Impedance rise stems from thickened SEI and contact loss between particles. These effects often follow an exponential relationship with temperature, with degradation rates doubling for every 10°C increase above 60°C in many systems. The degradation becomes particularly severe when high temperatures coincide with high states of charge, where silicon is most expanded and reactive.

Recent stabilization strategies focus on addressing these specific high-temperature failure mechanisms through material engineering approaches. Carbon coatings have proven effective by providing both mechanical support and chemical protection. Uniform carbon layers around silicon particles serve as diffusion barriers that slow electrolyte decomposition while accommodating volume changes. The carbon matrix maintains electrical connectivity even as silicon particles expand and contract. Pyrolytic carbon coatings demonstrate particular stability at elevated temperatures due to their high thermal stability and chemical inertness. Coatings with controlled porosity allow for lithium ion transport while blocking larger electrolyte molecules from reaching reactive silicon surfaces.

Pre-lithiation methods offer another stabilization pathway by compensating for initial lithium losses. Controlled lithium pre-doping creates an initial SEI layer before cycling begins, reducing the extent of subsequent SEI growth during high-temperature operation. Pre-lithiation can be achieved through various techniques including direct contact with lithium metal, electrochemical methods, or incorporation of lithium-rich additives. The pre-formed SEI tends to be more uniform and stable compared to SEI formed during normal cycling, particularly when combined with electrolyte additives designed for high-temperature operation. This approach mitigates the first-cycle irreversible capacity loss that plagues silicon anodes under thermal stress.

Composite material strategies combine silicon with thermally stable phases that buffer both mechanical and chemical degradation. Silicon-carbon composites with optimized phase distributions show improved high-temperature performance by limiting direct silicon-electrolyte contact while maintaining ionic pathways. The incorporation of ceramic phases such as silicon oxide or silicon nitride can further enhance thermal stability, though often at the expense of initial capacity. These composites balance the high capacity of silicon with the thermal resilience of more stable materials.

Electrolyte engineering complements these material approaches by formulating systems that form more stable SEI layers at high temperatures. Fluorinated carbonate solvents and lithium salts with higher thermal stability reduce the extent of parasitic reactions. Additives such as fluoroethylene carbonate become particularly important for silicon anodes operating under thermal stress, promoting the formation of LiF-rich SEI layers that are more mechanically robust and less prone to thermal decomposition.

Operational strategies also play a role in maintaining performance at elevated temperatures. Voltage window optimization can avoid the most damaging states of charge where silicon is most expanded and reactive. Advanced thermal management systems help maintain more moderate operating temperatures even in high-ambient conditions. These approaches work synergistically with material-level improvements to extend silicon anode lifetime under thermal stress.

The development of reliable silicon anodes for high-temperature applications requires careful balancing of multiple factors. Material solutions must simultaneously address mechanical stability, interfacial chemistry, and lithium inventory management while maintaining practical energy densities. Ongoing research continues to refine these stabilization strategies, with particular focus on scalable manufacturing processes that can translate laboratory successes into commercial products capable of withstanding real-world operating conditions. The ultimate goal remains achieving silicon's theoretical capacity advantages while meeting the stringent reliability requirements of applications where thermal challenges are unavoidable.