{"id":127549,"date":"2026-05-15T11:00:00","date_gmt":"2026-05-15T09:00:00","guid":{"rendered":"https:\/\/www.linseis.com\/?p=127549"},"modified":"2026-05-13T14:05:01","modified_gmt":"2026-05-13T12:05:01","slug":"thermal-diffusivity-in-batteries-influence-on-hot-spots-thermal-runaway-and-lifetime","status":"publish","type":"post","link":"https:\/\/www.linseis.com\/en\/wiki\/thermal-diffusivity-in-batteries-influence-on-hot-spots-thermal-runaway-and-lifetime\/","title":{"rendered":"Thermal diffusivity in batteries: Influence on hot spots, thermal runaway and lifetime"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"127549\" class=\"elementor elementor-127549 elementor-127524\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-b75441f e-flex e-con-boxed e-con e-parent\" data-id=\"b75441f\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-35d541b e-con-full e-flex e-con e-child\" data-id=\"35d541b\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-97683da elementor-toc--minimized-on-tablet elementor-widget elementor-widget-table-of-contents\" data-id=\"97683da\" data-element_type=\"widget\" data-e-type=\"widget\" data-settings=\"{&quot;headings_by_tags&quot;:[&quot;h2&quot;],&quot;exclude_headings_by_selector&quot;:[],&quot;no_headings_message&quot;:&quot;No headings were found on this page.&quot;,&quot;marker_view&quot;:&quot;numbers&quot;,&quot;minimize_box&quot;:&quot;yes&quot;,&quot;minimized_on&quot;:&quot;tablet&quot;,&quot;hierarchical_view&quot;:&quot;yes&quot;,&quot;min_height&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_tablet&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_mobile&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]}}\" data-widget_type=\"table-of-contents.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"elementor-toc__header\">\n\t\t\t\t\t\t<h4 class=\"elementor-toc__header-title\">\n\t\t\t\tTable of contents\t\t\t<\/h4>\n\t\t\t\t\t\t\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--expand\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__97683da\" aria-expanded=\"true\" aria-label=\"Open table of contents\"><svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-chevron-down\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M207.029 381.476L12.686 187.132c-9.373-9.373-9.373-24.569 0-33.941l22.667-22.667c9.357-9.357 24.522-9.375 33.901-.04L224 284.505l154.745-154.021c9.379-9.335 24.544-9.317 33.901.04l22.667 22.667c9.373 9.373 9.373 24.569 0 33.941L240.971 381.476c-9.373 9.372-24.569 9.372-33.942 0z\"><\/path><\/svg><\/div>\n\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--collapse\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__97683da\" aria-expanded=\"true\" aria-label=\"Close table of contents\"><svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-chevron-up\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M240.971 130.524l194.343 194.343c9.373 9.373 9.373 24.569 0 33.941l-22.667 22.667c-9.357 9.357-24.522 9.375-33.901.04L224 227.495 69.255 381.516c-9.379 9.335-24.544 9.317-33.901-.04l-22.667-22.667c-9.373-9.373-9.373-24.569 0-33.941L207.03 130.525c9.372-9.373 24.568-9.373 33.941-.001z\"><\/path><\/svg><\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<div id=\"elementor-toc__97683da\" class=\"elementor-toc__body\">\n\t\t\t<div class=\"elementor-toc__spinner-container\">\n\t\t\t\t<svg class=\"elementor-toc__spinner eicon-animation-spin e-font-icon-svg e-eicon-loading\" aria-hidden=\"true\" viewBox=\"0 0 1000 1000\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M500 975V858C696 858 858 696 858 500S696 142 500 142 142 304 142 500H25C25 237 238 25 500 25S975 237 975 500 763 975 500 975Z\"><\/path><\/svg>\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d69a620 elementor-widget elementor-widget-spacer\" data-id=\"d69a620\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-b80caf0 elementor-widget elementor-widget-heading\" data-id=\"b80caf0\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Why thermal diffusivity is more than just a material parameter<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-f563fb9 elementor-widget elementor-widget-text-editor\" data-id=\"f563fb9\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><a href=\"https:\/\/www.linseis.com\/en\/wiki\/measurement-of-thermal-stability\/\"><strong>Thermal diffusivity<\/strong><\/a> \u03b1 describes how quickly a temperature disturbance spreads in a material. Via the relationship \u03bb = \u03b1 &#8211; \u03c1 &#8211; c\u209a, it is directly linked to the <a href=\"https:\/\/www.linseis.com\/en\/properties\/thermal-conductivity\/\"><strong>thermal conductivity<\/strong><\/a> and thus determines in lithium-ion cells whether locally generated heat &#8211; for example due to side reactions, current density nests or local overcharging &#8211; is dissipated quickly or builds up to a dangerous hot spot. Numerical 3D models of thermal runtime show that even moderate inhomogeneities of thermal diffusivity at electrode and separator level can lead to highly localized temperature peaks [Oehler et al., 2021; Cloos et al., 2024]. For cell architecture, this means that the distribution of thermal diffusivity across layer thickness, surface direction and transitions between layers is at least as important as the absolute value of an individual material.   <\/p><p>An illustrative practical example is the combination of highly conductive current collectors with significantly less conductive active mass layers. If the diffusivity in the graphite coating is significantly lower than in the collector, a pronounced temperature gradient forms within the anode at high C rates, which favors local lithium plating and degradation [Gandert et al., 2025]. Conversely, selectively increased diffusivity or thermally conductive additives can mitigate temperature peaks at critical points &#8211; provided they are sensibly integrated into the overall design.  <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-89c0869 elementor-widget elementor-widget-spacer\" data-id=\"89c0869\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\n\t\t\t<img class=\"e-image-base e-21f92a0-4b1c716\" \n\t\t\t\t\tdata-interaction-id=\"21f92a0\" \n\t\t \n\t\t data-e-type=\"widget\" data-id=\"21f92a0\"\n\t\t\t\t\t\t\t\t\tid=\"127543\"\n\t\t\t\t\t\t\t\t\t\t\t\tsrc=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Hot-Spot-Formation-in-Lithium-Ion-Batteries.png\"\n\t\t\t\t\t\t\t\t\t\t\t\twidth=\"1536\"\n\t\t\t\t\t\t\t\t\t\t\t\theight=\"1024\"\n\t\t\t\t\t\t\t\t\t\t\t\tsrcset=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Hot-Spot-Formation-in-Lithium-Ion-Batteries.png 1536w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Hot-Spot-Formation-in-Lithium-Ion-Batteries-300x200.png 300w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Hot-Spot-Formation-in-Lithium-Ion-Batteries-1024x683.png 1024w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Hot-Spot-Formation-in-Lithium-Ion-Batteries-768x512.png 768w\"\n\t\t\t\t\t\t\t\t\t\t\t\talt=\"Cross-sectional view of a lithium-ion battery showing the formation of local hotspots, heat flow and temperature gradients across the cathode, separator and anode layers.\"\n\t\t\t\t\t\t\/>\n\t\t\t\t\t<div class=\"elementor-element elementor-element-2779a66 elementor-widget elementor-widget-spacer\" data-id=\"2779a66\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-70a90bd elementor-widget elementor-widget-heading\" data-id=\"70a90bd\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Graphite anodes: Anisotropy as opportunity and risk<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-36f5a88 elementor-widget elementor-widget-spacer\" data-id=\"36f5a88\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-035f339 elementor-widget elementor-widget-text-editor\" data-id=\"035f339\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>Graphite anodes are thermally anisotropic: in-plane &#8211; along the layer plane &#8211; the thermal conductivity and thus the thermal diffusivity is significantly higher than through the layer thickness, which has a direct effect on the propagation of hot spots. Measurements on commercial NMC\/graphite cells show that the effective diffusivity value of the anode coating is not determined solely by the graphite, but essentially by the binder, conductive soot, porosity and contact with the copper collector [Cloos et al., 2024; Oehler et al., 2021]. It follows from this: The microstructural design of the electrode layer &#8211; particle sizes, degree of filling, pore network &#8211; is a lever to control the heat propagation in a targeted manner without necessarily worsening the electrochemical performance.  <\/p><p>Operando studies show that even mild local temperature increases in graphite composites can change the lithium behavior and lead to local Li leakage from Li\u2093C\u2086 phases or to underpotential plating [Wang et al., 2022; Alujjage et al., 2025]. In combination with limited thermal diffusivity, self-reinforcing hot spots arise: Increased temperature accelerates side reactions, these generate additional heat that remains trapped locally due to lack of fast diffusion. Thermal diffusivity of the anode is therefore not only a safety parameter, but also a degradation parameter that must be taken into account in fast charging strategies and service life models.  <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-ac9afd3 elementor-widget elementor-widget-spacer\" data-id=\"ac9afd3\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\n\t\t\t<img class=\"e-image-base e-1883e7c-cc392f0\" \n\t\t\t\t\tdata-interaction-id=\"1883e7c\" \n\t\t \n\t\t data-e-type=\"widget\" data-id=\"1883e7c\" \n\t\t\t\t\t\t\t\t\tid=\"127544\"\n\t\t\t\t\t\t\t\t\t\t\t\tsrc=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Anisotropic-Heat-Conduction-in-Graphite-Anodes.png\"\n\t\t\t\t\t\t\t\t\t\t\t\twidth=\"1536\"\n\t\t\t\t\t\t\t\t\t\t\t\theight=\"1024\"\n\t\t\t\t\t\t\t\t\t\t\t\tsrcset=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Anisotropic-Heat-Conduction-in-Graphite-Anodes.png 1536w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Anisotropic-Heat-Conduction-in-Graphite-Anodes-300x200.png 300w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Anisotropic-Heat-Conduction-in-Graphite-Anodes-1024x683.png 1024w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Anisotropic-Heat-Conduction-in-Graphite-Anodes-768x512.png 768w\"\n\t\t\t\t\t\t\t\t\t\t\t\talt=\"Anisotropic Heat Conduction in Graphite Anodes\"\n\t\t\t\t\t\t\/>\n\t\t\t\t\t<div class=\"elementor-element elementor-element-72b4575 elementor-widget elementor-widget-spacer\" data-id=\"72b4575\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-1b982d6 elementor-widget elementor-widget-heading\" data-id=\"1b982d6\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Separators: Thermal bottleneck with safety potential<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-92f5197 elementor-widget elementor-widget-spacer\" data-id=\"92f5197\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-5df331d elementor-widget elementor-widget-text-editor\" data-id=\"5df331d\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>Separators typically have a significantly lower thermal diffusivity than electrodes and current arresters and therefore often represent the thermal bottleneck in the cell cross-section. As a result, they can amplify temperature differences between the electrode sides; at the same time, modern separator concepts deliberately act as a &#8220;thermal fuse&#8221;, for example through targeted pore closure at defined temperatures. Current work on so-called smart thermal shutdown separators shows that the combination of low base diffusivity and specifically increased thermal conductivity through ceramic fillers &#8211; for example boron nitride (BN) &#8211; can mitigate local hot spots while maintaining electrochemical function during normal operation [Li et al., 2025; Liu et al., 2021].  <\/p><p><br>It is crucial not to consider separators in isolation, but in combination with the anode, cathode and electrolyte. Studies indicate that the interplay of separator diffusivity, electrode diffusivity and contact resistances determines the hot spot position &#8211; for example, whether critical zones tend to form in the electrode volume or in the vicinity of the separator [Gandert et al., 2025]. The surface emissivity of the separator and electrode surfaces also directly influences the sensitivity of imaging detection methods such as lock-in or IR thermography.  <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-c348815 elementor-widget elementor-widget-spacer\" data-id=\"c348815\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-95aac46 elementor-widget elementor-widget-heading\" data-id=\"95aac46\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Hot spot detection: Operando metrology meets material characterization<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-6dd2e47 elementor-widget elementor-widget-spacer\" data-id=\"6dd2e47\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-a18f69c elementor-widget elementor-widget-text-editor\" data-id=\"a18f69c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>For a reliable hot spot analysis, it is not enough to simply measure the external temperature of a cylinder or pouch cell. Spatially resolved temperature information and reliable material data are crucial. Operando IR thermography in combination with physics-based models makes it possible to derive internal temperature fields and quantify hot spots &#8211; provided the thermal diffusivity of the individual cell components is known [Wang et al., 2022]. New <em>thermal wave sensors<\/em> specifically use frequency-dependent thermal diffusion to draw conclusions about degradation states and local changes in thermal properties from the response to modulated thermal excitation.   <\/p><p>A recent study on internal temperature evolution in Li-ion cells shows that the discrepancy between internal and external temperature measurement under operating conditions can be considerable and that hot spots and lithium plating on graphite anodes can only be fully quantified in this way [Alujjage et al., 2025]. Not only the absolute temperature level, but also the temporal development with known thermal diffusivity provides valuable information about local defects, inhomogeneities or aging zones. The coupling of operando measurement methods with experimentally determined diffusivities is therefore an effective tool for detecting weak points in the cell architecture as early as the material and cell concept phase.  <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-3b379d1 elementor-widget elementor-widget-spacer\" data-id=\"3b379d1\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\n\t\t\t<img class=\"e-image-base e-04f427c-617bc41\" \n\t\t\t\t\tdata-interaction-id=\"04f427c\" \n\t\t \n\t\t data-e-type=\"widget\" data-id=\"04f427c\" \n\t\t\t\t\t\t\t\t\tid=\"127545\"\n\t\t\t\t\t\t\t\t\t\t\t\tsrc=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Operando-Hot-Spot-Detection-in-Lithium-Ion-Batteries.png\"\n\t\t\t\t\t\t\t\t\t\t\t\twidth=\"1536\"\n\t\t\t\t\t\t\t\t\t\t\t\theight=\"1024\"\n\t\t\t\t\t\t\t\t\t\t\t\tsrcset=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Operando-Hot-Spot-Detection-in-Lithium-Ion-Batteries.png 1536w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Operando-Hot-Spot-Detection-in-Lithium-Ion-Batteries-300x200.png 300w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Operando-Hot-Spot-Detection-in-Lithium-Ion-Batteries-1024x683.png 1024w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Operando-Hot-Spot-Detection-in-Lithium-Ion-Batteries-768x512.png 768w\"\n\t\t\t\t\t\t\t\t\t\t\t\talt=\"Scientific illustration showing operando IR thermography, internal temperature mapping, and hot-spot detection in lithium-ion batteries using thermal imaging and physics-based modeling.\"\n\t\t\t\t\t\t\/>\n\t\t\t\t\t<div class=\"elementor-element elementor-element-0e0a422 elementor-widget elementor-widget-spacer\" data-id=\"0e0a422\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-1632185 elementor-widget elementor-widget-heading\" data-id=\"1632185\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Cell format and thermal diffusivity: round cell, pouch and prismatic in comparison<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d6035da elementor-widget elementor-widget-spacer\" data-id=\"d6035da\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-cc80029 elementor-widget elementor-widget-text-editor\" data-id=\"cc80029\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>Thermal diffusivity has fundamentally different effects depending on the cell format &#8211; with direct consequences for the design of the thermal management system and the susceptibility to hot spots.<\/p><p>In <b>round cells<\/b> (18650, 21700), a pronounced anisotropy between axial and radial direction dominates. Anisotropic thermal conductivities of 0.20 W-m-\u00b9-\u00b0C-\u00b9 in the radial direction and up to 30.4 W-m-\u00b9-\u00b0C-\u00b9 in the axial direction have been measured for 18650 round cells. Heat generated in the cell core is therefore preferentially dissipated axially, while radial transport &#8211; in the direction of the cell surface and the cooling system &#8211; is strongly inhibited. At high C-rates, this results in considerable temperature gradients between the core and the cladding, which cannot be detected with pure external temperature measurement [Gandert et al., 2025].   <\/p><p><b>Pouch cells<\/b> have complementary characteristics: Pouch cells have inherently good in-plane heat dissipation due to their large surface area and flat design. However, as heat dissipation in the through-plane direction is less homogeneous, temperature gradients and hot spots can occur &#8211; particularly pronounced during fast charging. The thermal characterization of pouch cells therefore requires methods that capture both directions &#8211; laser flash analysis on representative layer stacks provides the most reliable input data for simulation models [Lin et al., 2022; Cloos et al., 2024].  <\/p><p><b>Prismatic cells<\/b> combine elements of both geometries. In prismatic and pouch cells, the thermal conductivity is decomposed along length, height and layer thickness, while in cylindrical geometries a decomposition in radial and axial direction is more appropriate. Here too, the through-plane diffusivity &#8211; perpendicular to the electrode layers &#8211; represents the dominant thermal bottleneck [Oehler et al., 2021].  <\/p><p>This results in a clear requirement for measurement technology: a single scalar diffusivity measurement is not sufficient for any of these formats. Only the complete anisotropic characterization of realistic layer systems over the relevant temperature range provides the input parameters for reliable thermal simulations and hot-spot predictions [Gandert et al., 2025; Cloos et al., 2024]. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-c7225d7 elementor-widget elementor-widget-spacer\" data-id=\"c7225d7\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-2c36fea elementor-widget elementor-widget-heading\" data-id=\"2c36fea\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Measurement technology: Flash analysis as the basis for realistic material parameters<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-5093464 elementor-widget elementor-widget-spacer\" data-id=\"5093464\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-2b2fdfa elementor-widget elementor-widget-text-editor\" data-id=\"2b2fdfa\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>A robust method for measuring the thermal diffusivity of graphite anodes, separators and composite structures is essential for use in R&amp;D and quality assurance. An established approach is laser flash analysis (LFA): A short energy pulse heats a sample surface, and the temperature rise over time on the opposite side is recorded using an IR detector, from which the thermal diffusivity can be calculated [Balaji et al., 2024]. The combination with density and specific heat capacity then results in the thermal conductivity &#8211; the central input parameter for thermal simulation models.  <\/p><p>For battery-relevant materials, it is important to examine not only bulk samples, but also realistic configurations: Graphite coatings on copper, separator foils or composite electrode stacks. Studies show that the effective thermal diffusivity of an electrode composite deviates significantly from the ideal value of pure graphite &#8211; in particular due to the interface with the copper foil and the distribution of polymeric and conductive additives [Cloos et al., 2024; Gandert et al., 2025]. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-760196a elementor-widget elementor-widget-spacer\" data-id=\"760196a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\n\t\t\t<img class=\"e-image-base e-0c39e62-19ff8d9\" \n\t\t\t\t\tdata-interaction-id=\"0c39e62\" \n\t\t \n\t\t data-e-type=\"widget\" data-id=\"0c39e62\" \n\t\t\t\t\t\t\t\t\tid=\"127546\"\n\t\t\t\t\t\t\t\t\t\t\t\tsrc=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Thermische-Diffusivitaet-in-Batterien-LFA.png\"\n\t\t\t\t\t\t\t\t\t\t\t\twidth=\"1140\"\n\t\t\t\t\t\t\t\t\t\t\t\theight=\"641\"\n\t\t\t\t\t\t\t\t\t\t\t\tsrcset=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Thermische-Diffusivitaet-in-Batterien-LFA.png 1140w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Thermische-Diffusivitaet-in-Batterien-LFA-300x169.png 300w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Thermische-Diffusivitaet-in-Batterien-LFA-1024x576.png 1024w, https:\/\/www.linseis.com\/wp-content\/uploads\/2026\/05\/Thermische-Diffusivitaet-in-Batterien-LFA-768x432.png 768w\"\n\t\t\t\t\t\t\t\t\t\t\t\talt=\"Laser Flash Analysis (LFA) devices for measuring the thermal diffusivity and thermal conductivity of materials used in battery research and advanced thermal characterization.\"\n\t\t\t\t\t\t\/>\n\t\t\t\t\t<div class=\"elementor-element elementor-element-ab69d4f elementor-widget elementor-widget-spacer\" data-id=\"ab69d4f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-e8790b5 elementor-widget elementor-widget-heading\" data-id=\"e8790b5\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Strategic consequences for battery development<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-3b81415 elementor-widget elementor-widget-spacer\" data-id=\"3b81415\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-5d6b329 elementor-widget elementor-widget-text-editor\" data-id=\"5d6b329\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>For developers of cell architectures, there is a clear action plan: thermal diffusivity should be considered early in the material selection process &#8211; especially for graphite anode formulations and separator concepts. Anisotropies can be used in a targeted manner, for example through high in-plane diffusivity for lateral heat dissipation; at the same time, gradients through the layer thickness must be verified by measurement and modeling [Oehler et al., 2021]. Material and cell models should be systematically fed with experimentally determined diffusivity values in order to derive realistic temperature fields and <em>thermal runaway scenarios<\/em>. Operando methods &#8211; IR thermography, thermal waves, internal sensors &#8211; only develop their full potential in combination with exact thermophysical data: Hot spots thus become not only qualitatively visible, but also quantitatively assessable [Alujjage et al., 2025].   <\/p><p>Thermal diffusivity is thus being transformed from an often neglected material parameter into a strategic development parameter that can be used to increase safety margins, extend fast-charging windows and mitigate degradation mechanisms in graphite anodes and separators at an early stage.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-49c8dc2 elementor-widget elementor-widget-spacer\" data-id=\"49c8dc2\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d311197 elementor-widget elementor-widget-heading\" data-id=\"d311197\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Bibliography<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-bc5a2c1 elementor-widget elementor-widget-spacer\" data-id=\"bc5a2c1\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-7ec0ae5 elementor-widget elementor-widget-text-editor\" data-id=\"7ec0ae5\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<ol><li><p>[Alujjage <strong> et al, 2025]<\/strong> Alujjage, N. et al: <em>Internal Temperature Evolution Metrology and Analytics in<\/em><em>Li-Ion<\/em><em>Cells<\/em>. Advanced Functional Materials, 2025. DOI: 10.1002\/adfm.202417273 <a href=\"https:\/\/advanced.onlinelibrary.wiley.com\/doi\/10.1002\/adfm.202417273\" target=\"_blank\" rel=\"noopener\">https:\/\/advanced.onlinelibrary.wiley.com\/doi\/10.1002\/adfm.202417273<\/a><\/p><\/li><li><p>[<strong>Balaji et al, 2024]<\/strong> Balaji, C. et al: <em>Thermal Transport and Thermal Diffusivity by Laser Flash Technique: A Review<\/em>. International Journal of Thermophysics, 2024. DOI: 10.1007\/s10765-024-03479-0 <a href=\"https:\/\/www.researchgate.net\/publication\/387526329_Thermal_Transport_and_Thermal_Diffusivity_by_Laser_Flash_Technique_A_Review\" target=\"_blank\" rel=\"noopener\">https:\/\/www.researchgate.net\/publication\/387526329_Thermal_Transport_and_Thermal_Diffusivity_by_Laser_Flash_Technique_A_Review<\/a>  <\/p><\/li><li><p>[<strong>Cloos et al., 2024]<\/strong> Cloos, L.; Herberger, S.; Queisser, O. et al.: <em>Thermal Material Properties of Commercial NMC532 \/ Graphite Lithium-Ion Battery Cell<\/em>. Karlsruhe Institute of Technology (KIT), 2024. DOI: 10.35097\/kAlrZQzUaHBxWkIj <a href=\"https:\/\/publikationen.bibliothek.kit.edu\/1000171382\" target=\"_blank\" rel=\"noopener\">https:\/\/publikationen.bibliothek.kit.edu\/1000171382<\/a>  <\/p><\/li><li><p>[<strong>Gandert et al., 2025]<\/strong> Gandert, J. C.; M\u00fcller, M.; Paarmann, S.; Queisser, O.; Wetzel, T.: <em>Challenges of the Measurement of the Effective Thermal Conductivity of Battery Electrodes with Laser Flash Analysis and Guarded Hot Plate Method<\/em>. Energy Technology, 2025. DOI: 10.1002\/ente.202501125 <a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/10.1002\/ente.202501125\" target=\"_blank\" rel=\"noopener\">https:\/\/onlinelibrary.wiley.com\/doi\/10.1002\/ente.202501125<\/a><\/p><\/li><li><p>[<strong>Li et al., 2025]<\/strong> Li, Y. et al.: <em>Smart thermal-shutdown separators with fast response for safe Li-metal batteries<\/em>. ScienceDirect \/ Journal of Power Sources, 2025. <a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/S3050914925000962\" target=\"_blank\" rel=\"noopener\">https:\/\/www.sciencedirect.com\/science\/article\/pii\/S3050914925000962<\/a> <\/p><\/li><li><p>[<strong>Lin et al, 2022]<\/strong> Lin, J.; Chu, H. N.; Monroe, C. W.; Howey, D. A.: <em>Anisotropic Thermal Characterization of Large-Format Lithium-Ion Pouch Cells<\/em>. Batteries &amp; Supercaps, 5, e202100401, 2022. DOI: 10.1002\/batt.202100401 <a href=\"https:\/\/chemistry-europe.onlinelibrary.wiley.com\/doi\/10.1002\/batt.202100401\" target=\"_blank\" rel=\"noopener\">https:\/\/chemistry-europe.onlinelibrary.wiley.com\/doi\/10.1002\/batt.202100401<\/a><\/p><\/li><li><p><strong>[Liu et al., 2021]<\/strong> Liu, W. et al: <em>Safer<\/em><em>Lithium-Ion<\/em><em>Batteries from the Separator Aspect: Development and Future Perspectives<\/em>. Energy &amp; Environmental Materials, 2021. DOI: 10.1002\/eem2.12129 <a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/full\/10.1002\/eem2.12129\" target=\"_blank\" rel=\"noopener\">https:\/\/onlinelibrary.wiley.com\/doi\/full\/10.1002\/eem2.12129<\/a>  <\/p><\/li><li><p>[<strong>Oehler et al., 2021]<\/strong> Oehler, D.; Seegert, P.; Wetzel, T.: <em>Investigation of the Effective Thermal Conductivity of Cell Stacks of<\/em><em>Li-Ion<\/em><em>Batteries<\/em>. Energy Technology, 2021. DOI: 10.1002\/ente.202000722 <a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/full\/10.1002\/ente.202000722\" target=\"_blank\" rel=\"noopener\">https:\/\/onlinelibrary.wiley.com\/doi\/full\/10.1002\/ente.202000722<\/a><\/p><\/li><li><p>[<strong>Wang et al, 2022]<\/strong> Wang, W. et al: <em>In-situ thermography revealing the evolution of internal short circuit of lithium-ion batteries<\/em>. Journal of Power Sources, 2022. DOI: 10.1016\/j.jpowsour.2022.231602 <a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S037877532200605X\" target=\"_blank\" rel=\"noopener\">https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S037877532200605X<\/a><\/p><\/li><\/ol>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Thermal diffusivity \u03b1 describes how quickly a temperature disturbance spreads in a material. It is directly linked to the thermal conductivity via the relationship \u03bb = \u03b1 &#8211; \u03c1 &#8211; c\u209a and thus determines in lithium-ion cells whether locally generated heat &#8211; for example due to side reactions, current density nests or local overcharging &#8211; is dissipated quickly or builds up to a dangerous hot spot.   <\/p>\n","protected":false},"author":3,"featured_media":127547,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[106],"tags":[],"class_list":["post-127549","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-wiki"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/posts\/127549","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/comments?post=127549"}],"version-history":[{"count":0,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/posts\/127549\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/media\/127547"}],"wp:attachment":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/media?parent=127549"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/categories?post=127549"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/tags?post=127549"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}