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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

Measurements of Heat Generation Rate in Nanoporous Pseudocapacitive Electrodes




Abstract

Heat generation in electrochemical capacitors used for high power energy storage can result in shorter lifetime and reduced performance due to accelerated aging and self-discharge, for example. This study aims to quantify experimentally the heat generation rate in electrochemical capacitors under various charging and discharging conditions. First, the design, construction, and validation of a custom-made non-adiabatic calorimeter are presented. In brief, the calorimeter consisted of (i) two heat flux sensors, (ii) two instrumented cold plates fed with a circulating coolant from a temperature-controlled chiller, (iii) an electrochemical test cell, and (iv) a potentiostat/galvanostat unit. The electrochemical test cell consisted of two different electrodes and a separator immersed in an electrolyte. Each heat flux sensors uses 16 T-type thermocouples connected in series to detect the instantaneous temperature variations in the test cell. Then, the heat generation rate can be extracted by deconvolution of the temporal evolution of the temperature. This technique shows a high sensitivity to temperature variation as low as 0.004 K. Finally, experimental measurements of heat generation rates out under galvanostatic cycling were reported for different parameters including (a) the operating temperature, (b) the electrode morphology and material, (c) the current density, and (d) the charging period. Particular attention was paid to the effect of the pseudocapacitive electrode thickness and the absence (thin) or occurrence (thick) of phase transformation during lithium intercalation.

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