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The assessed guidelines showed a broad range of quality: some producers attached importance to an evidence-based development process; but in spite of this, a large number of guidelines were only of middling quality. As national particularities are only rarely mentioned and the development process of guidelines is complex, an international collaboration that aims toward the production of shareable guidelines might be promising.

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Extreme fast charging lithium ion batteries require aggressive thermal management, which keeps the maximum cell temperature below abusive thresholds without derating the charging power. The importance of thermal management is further increased for many new cell designs with improved energy density which often brings along weaker thermal performance. For instance, reducing the volume fraction of electrochemically inactive materials like the current collectors reduces the thermal conductivity and increases the heat generation. Aggressive cooling is achieved by increasing the heat convection coefficients between the cell surface and the heat transfer medium. With high heat convection coefficients, the internal thermal conductivity of the electrode-separator-composite determines the maximum cell temperature. Consequently, the thermal conductivity needs to be characterized accurately for fast charging investigations, which includes dependencies on parameters like temperature or compression load at the cell surface. Therefore, this work presents thermal conductivity measurements at different cell temperatures and compression loads with their impact on fast charging. The thermal conductivity of a large-format NMC-111 graphite cell with a flat-wound jelly roll and prismatic PHEV2 hardcase made of aluminum alloy is measured at temperatures between -10 and 50 °C and at external compression loads between 37 and 74 kPa. This compression range is defined by the manufacturer at the largest cell surfaces to counter swelling of the jelly roll. Based on the guarded heater principle, a precise thermal conductivity test bench is designed and validated by a stainless steel reference material. For deriving the thermal conductivity of the electrode-separator-composite from the full-cell measurements, the thermal conductivity of the hardcase has to be compensated. For this purpose, a fast and simple technique for measuring the thermal conductivity of the hardcase by using electrical resistance measurements and applying theories like the law of Wiedemann–Franz is introduced. According to the measurement result, the thermal conductivity increases by 13.6% at 20 °C when the compression load rises from 37 to 74 kPa, which is mainly attributed to reduced thermal contact resistances between the cell layers. At constant compression and rising mean temperature, the thermal conductivity decreases by more than -1% per °C compared to the value at 20 °C. Both findings affect the cell internal temperature rise during aggressive cooling and therefore the power-derating events due to overheating. Based on these findings, implications for thermal control strategies during fast charging are discussed. Figure: Thermal conductivity of NMC-G electrode-separator-composite in through-plane direction at different cell temperatures and compression loads at the two largest surfaces of a prismatic PHEV2 cell. Figure 1

ResumenPropósitoEvaluamos la calidad de las directrices de tratamiento europeas en el campo de la salud mental que han producido las asociaciones psiquiátricas nacionales. El enfoque principal estaba en la pregunta de si el proceso de desarrollo de las directrices siguió los principios básicos de la medicina científico-estadística (evidence-based).MétodosSe evaluó 61 directrices de práctica clínica europeas de 14 países, publicadas entre 1998 y 2003, utilizando el “Instrumento de Apreciación de Directrices para la Investigación y la Evaluación (AGREE)”. Se calculó la puntuación de dominio para cada uno de los seis dominios del instrumento AGREE. Se evaluó detalladamente los siete elementos del dominio “rigor del desarrollo” y un elemento adicional acerca de las particularidades nacionales.ResultadosLas puntuaciones medias en los seis dominios fueron bastante bajas, aunque la calidad variaba entre las diferentes directrices. La puntuación media más alta se obtuvo en el dominio claridad y presentación (70,8%, DT = 23,5); la más baja, en independencia editorial (19,7%, DT = 29,3). Se podría considerar que las recomendaciones de aproximadamente la mitad de las directrices evaluadas eran científico-estadísticas.ConclusiónLas directrices evaluadas mostraron un amplio abanico de calidad: algunos productores concedían importancia a un proceso de desarrollo científico-estadístico, pero, a pesar de esto, un gran número de directrices era sólo de calidad regular. Como las particularidades nacionales se mencionan únicamente con poca frecuencia y el proceso de desarrollo de las directrices es complejo, una colaboración internacional que apuntara a la producción de directrices compartibles podría ser prometedor.