2023-09-26 22:00:00
An accumulator is a complex electrochemical device used to convert the chemical energy of the active materials of the electrodes that compose it, into electrical energy. The latter is made available when the electrical circuit connecting its positive and negative terminals is closed. The accumulator differs from the battery in that it is electrically rechargeable, by means of an electric current circulating in the opposite direction to that of the discharge. Accumulators can be grouped into batteries in order to meet the increasingly varied application requirements that our society needs. From the smallest wireless products to the largest storage systems connected to the electrical network, including the massive electrification of transport, a wide range of accumulators, of varied sizes and technologies, are working to provide power and storage. energy required.
The fact that an accumulator can spontaneously deliver a current, as soon as its terminals are connected, is not without posing an obvious safety problem. This is an uninterruptible power supply, requiring training and electrical authorization from certain voltage thresholds and quantity of charges stored in the accumulator, in order to guarantee its safe operation. Beyond security aspects, understanding why this current is spontaneously available requires delving into theoretical considerations from numerous scientific disciplines: thermodynamics, physics, electrochemistry, among others…
First of all, it is necessary to understand what an electrolyte is, because it is an indispensable component of the accumulator. The chemical considerations relating to the ions and the solvent can give the reader the impression that he is wasting his time, studying phenomena occurring on a spatial scale so far removed from the physical reality of everyday life around him. However, this step is essential, because it lays the foundations for concepts that have repercussions on the limits of the accumulator in operation.
Next comes the study of the electrode. Due to the fact that it is immersed in the electrolyte, the notion of interface can be introduced, and with it, the appearance of an electric field. We are gradually beginning to understand the electromotive force at work, and its dependence on the environment (temperature and pressure). We also explain why a potential is inaccessible alone, how a reference electrode can allow us to access it indirectly, and what the price is to pay. Out of equilibrium, that is to say when a current passes through the electrode, we show that its electric potential drops due to overvoltages having very distinct origins.
Finally, the accumulator as a whole is treated as a closed system, having its own characteristics, determined by the nature of the electrodes and the electrolyte which compose it. We discuss its limits and the possibility of assembling several accumulators into a battery to push the limits even further.
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