High-temporal-resolution infrared (IR) imaging is a critical tool for analyzing thermal behavior in energy storage systems subjected to pulsed loads, particularly in aerospace and defense applications where rapid charge-discharge cycles are common. Unlike conventional thermal imaging, which may capture data at low frame rates, high-speed IR cameras provide microsecond-scale resolution, enabling precise tracking of transient heat generation and dissipation. This capability is essential for understanding thermal dynamics in high-rate batteries and supercapacitors, where localized heating can influence performance, safety, and longevity.

When a battery or supercapacitor undergoes pulsed loading, heat generation occurs due to ohmic losses, charge transfer inefficiencies, and mass transport limitations. The thermal response depends on the cell’s internal resistance, thermal conductivity of materials, and heat dissipation pathways. High-temporal-resolution IR imaging captures these phenomena in real time, revealing how heat propagates through electrodes, current collectors, and casing. For example, in lithium-ion batteries under high-current pulses, hotspots often form near electrode edges or tab connections due to current crowding. Supercapacitors, with their low internal resistance, exhibit more uniform heating but still require monitoring to prevent degradation from cumulative thermal stress.

Thermal time constants are a key metric derived from high-speed IR data. They quantify how quickly a system reaches thermal equilibrium after a pulse. The time constant (τ) is calculated by fitting temperature decay curves to an exponential model, T(t) = T₀ + ΔT·e^(-t/τ), where T₀ is ambient temperature and ΔT is the temperature rise. For a high-rate Li-ion cell, τ may range from milliseconds to seconds, depending on cell design and cooling conditions. In aerospace applications, where weight constraints limit passive cooling, thermal time constants directly influence pulse frequency limits. Exceeding these limits can lead to heat accumulation, accelerating capacity fade or triggering thermal runaway.

Heat dissipation dynamics vary with cell architecture. Pouch cells, commonly used in aerospace, dissipate heat primarily through their large surface areas, while cylindrical cells rely on conductive pathways through metal casings. IR imaging reveals asymmetric cooling patterns; for instance, a pouch cell may cool faster along its aluminum laminate edges than at its center. Supercapacitors, with their organic electrolytes and porous electrodes, exhibit faster thermal equilibration than batteries but face challenges in managing heat during repetitive high-power bursts. Data from supercapacitor testing shows that pulse frequencies above 10 Hz can cause progressive temperature rise unless active cooling is employed.

Pulse frequency limits are dictated by the interplay between heat generation and dissipation. If the interval between pulses is shorter than the thermal time constant, residual heat accumulates, raising the baseline temperature. For example, a Li-ion battery with τ = 500 ms subjected to 5 Hz pulses (200 ms intervals) will experience stepwise temperature increases. IR imaging quantifies this effect, guiding the design of pulse profiles that avoid critical thresholds. In defense applications, where mission-critical systems require bursts of power, such analysis ensures reliable operation without thermal overload.

Case studies from supercapacitor testing illustrate these principles. A 3000 F ultracapacitor subjected to 100 A pulses at varying frequencies showed negligible heating at 1 Hz but a 15°C rise at 20 Hz. High-speed IR footage revealed that heat localized near the current collectors, with τ ≈ 50 ms. This data informed pulse frequency limits for a military radar system, ensuring thermal stability during peak loads. Similarly, a high-rate LiFePO₄ battery tested under aerospace conditions demonstrated τ ≈ 1.2 s, necessitating pulse intervals ≥ 2 s to prevent heat buildup.

Material properties also influence thermal dynamics. Electrodes with high thermal conductivity, such as those with copper or aluminum foils, distribute heat more evenly than resistive materials. IR imaging of silicon-anode batteries under pulsed loads shows pronounced hotspots due to silicon’s low thermal diffusivity, highlighting the need for thermal interface materials or enhanced cooling in such designs. Conversely, supercapacitors with graphene-based electrodes exhibit rapid heat dispersion, enabling higher pulse frequencies.

Implications for system design are significant. High-temporal-resolution IR data validates thermal models used to simulate battery behavior under pulsed loads. For aerospace applications, where weight and volume are constrained, this data optimizes trade-offs between energy density and thermal management. Active cooling systems, such as microchannel heat sinks, can be tailored based on IR-derived heat maps, minimizing parasitic power losses. In defense systems, where reliability is paramount, IR findings inform derating strategies to extend cycle life under extreme conditions.

Future advancements in IR imaging, such as higher frame rates or multi-spectral analysis, will further refine thermal characterization. Coupled with machine learning for real-time anomaly detection, these tools will enhance the safety and performance of batteries and supercapacitors in pulsed-load scenarios. The integration of high-speed IR into quality control processes ensures that thermal flaws are identified early, reducing failure risks in critical applications.

In summary, high-temporal-resolution IR imaging provides unparalleled insights into the thermal behavior of energy storage systems under pulsed loads. By quantifying heat dissipation dynamics and thermal time constants, it establishes pulse frequency limits that balance performance and safety. Examples from supercapacitor and high-rate battery testing demonstrate its utility in aerospace and defense, where thermal management is a key determinant of system success. As pulsed-load applications grow in complexity, the role of high-speed IR imaging will only expand, driving innovations in materials, cooling strategies, and operational protocols.