Heat Evolution and Electrical Work of Batteries as a Function of Discharge Rate: Spontaneous and Reversible Processes and Maximum Work

摘要

Many types of batteries power an ever-growing number of devices. Electrochemical devices like batteries and fuel cells can, in principle, exceed Carnot efficiency for energy conversion. In this novel laboratory experiment, students explore the partitioning of the enthalpy change of a battery’s electrochemical reaction between useful electrical work and waste heat, ΔH = w _(elec) + q . Work is measured by monitoring cell potential and current during battery discharge; waste heat evolved at the battery is simultaneously measured in a calorimeter. Results from discharging AA-size “alkaline” batteries are presented. Data for nickel–cadmium, nickel–metal hydride; a D-size, single cell, lead-acid storage battery; and Zn/Ag_(2)O watch batteries are also presented in the Supporting Information.