Spatial Thermal Conductivity Characterization in Prismatic Formats
Measuring anisotropic conductivity tensors under mechanical stack compression prevents thermal modeling errors in large prismatic lithium battery packs.
Through-Plane Thermal Resistance
Meaning
Total opposition to conductive heat transfer measured perpendicular to the flat active surface of layered electrodes, separators, or composite cell stacks quantifies heat dissipation efficiency across thickness dimensions. Determining through-plane thermal resistance is necessary when designing battery module cooling systems that extract heat from large cell faces into external cooling plates. Sourcing teams use this property to evaluate whether cell internal architecture allows rapid heat extraction during high-current DC fast-charging cycles.
Structural Impedance
Layered battery jelly rolls or stacked pouch cell configurations alternate between metallic current collectors, porous active electrode coatings, polymeric separators, and liquid electrolyte films. Heat conduction across these interfaces encounters numerous microscopic boundary resistances, making through-plane thermal conductivity significantly lower than in-plane conductivity along copper and aluminum foils. Polyolefin separator membranes and porous ceramic coatings exhibit low intrinsic thermal conductivity, creating primary thermal bottlenecks within the cell core.
High-density calendering and complete electrolyte wetting reduce internal void spaces, lowering overall through-plane resistance.
Thermal Bottlenecks
Heat generated by ohmic dissipation and electrochemical reaction kinetics during fast charging must travel across multiple electrode layers to reach external cooling surfaces. Elevated through-plane resistance traps heat in the cell center, generating steep internal temperature gradients that accelerate localized electrode aging. Inadequate heat conduction causes core temperatures to exceed allowable safety margins while outer surfaces appear cool.
Efficient module thermal management demands minimal through-plane impedance to prevent internal thermal degradation during continuous high-load duty cycles.
Laboratory Characterization
Standardized testing procedures such as ASTM D5470 or specialized guarded heat flow meters measure through-plane impedance under controlled mechanical compression loads. Procurement specifications stipulate maximum acceptable thermal resistance across complete cell stacks under nominal end-of-life swelling pressures. Sourcing engineers review characterization reports showing through-plane thermal properties across diverse states of charge and operating temperatures.
Accurate measurement inputs ensure battery pack thermal simulations match real-world thermal performance.