Basic electrochemical principles

Electrochemical cells facilitate the conversion between electrical and chemical energy.

When discharging, the electrochemical cell converts chemical energy into electrical energy, operating as a galvanic cell. Conversely, when charging, it converts electrical energy into chemical energy, functioning as an electrolytic cell.

Electrochemical cells such as batteries consist of a cathode and an anode. The cathode, sometimes called the negative electrode, is where electrochemical reduction reactions take place. The anode, sometimes called the positive electrode, is where electrochemical oxidation (redox) reactions take place.

These electrodes are made of conductive materials to facilitate the electrochemical reactions that occur at their surface. Metals and carbon materials are commonly used in the production of electrode materials due to their good electrical conductivity (Gaddam & Zhao, 2023).

The anode and cathode are separated by an electrolyte, which contains ions that move between the anode and cathode. In redox reactions, electrons move between electrodes through an external circuit, while ions move inside the electrochemical cell via the electrolyte to keep the charge balance in the cell (Berg, 2015).

As described in the previous step, batteries are classified as primary (non-rechargeable) and secondary (rechargeable) types. Non-rechargeable batteries are only able to convert chemical energy into electrical energy and are thus galvanic cells. In contrast, rechargeable batteries can work as both galvanic and electrolytic cells (Berg, 2015).

Research and share

Next week, we will explore secondary batteries with different chemistries: lead-acid, nickel-metal hydride (NiMH), and lithium-ion (Li-ion).

To finish this week, research one of the secondary battery types we won’t be covering in as much detail: nickel-cadmium (NiCad). Look into its charge/discharge mechanism and applications. Share some findings in the comments below.

References

Berg, H. (2015). Batteries for electric vehicles: materials and electrochemistry. Cambridge University Press.

Gaddam, R. R., & Zhao, G. (2023). Handbook of Sodium-Ion Batteries: Materials and Characterization. Jenny Stanford Publishing.

Figure 19.1 Electrochemical Cells from Chapter 19.1: Describing Electrochemical Cells in General Chemistry: Principles, Patterns, and Applications. Saylor Academy, 2012; CC BY-NC-SA 3.0