Lithium battery: How does it work?

As an indispensable power source in modern electronic devices, lithium batteries are of great importance. However, in addition to their use in various high-tech products, the working principle and composition of lithium batteries themselves are also worth exploring in depth. This article will analyse this issue from four aspects: the basic working principle of lithium batteries, the core components, the charging and discharging process, and the safety performance.

1. What is the basic principle of lithium batteries?

Lithium batteries, also known as lithium-ion batteries, are based on the reversible movement of lithium ions between positive and negative electrodes. During the charging process, the electrical energy provided by the external power source causes lithium ions to be released from the positive electrode material, migrate through the electrolyte to the negative electrode and embed themselves in the negative electrode material. In the process, electrical energy is converted to chemical energy and stored. During discharge, lithium ions are released from the negative electrode and migrate back through the electrolyte to the positive electrode, releasing energy for external devices to use. This process achieves an efficient conversion between electrical and chemical energy.

2. What are the main components of lithium batteries?

Lithium batteries are mainly composed of positive electrode, negative electrode, electrolyte, diaphragm and casing. The positive electrode material is usually lithium cobalt oxide, lithium nickel manganese cobalt oxide or lithium iron phosphate, which have high energy density and good electrochemical properties. The negative electrode is usually a graphite or silicon-based composite that can reversibly incorporate and extract lithium ions. The electrolyte is the medium for lithium ion migration and is generally composed of organic solvents and lithium salts. The membrane is located between the positive and negative electrodes to prevent direct contact and short-circuiting, while allowing lithium ions to pass freely. The casing serves to encapsulate and protect the internal components.

3. How do lithium batteries charge and discharge?

The charging and discharging of lithium batteries is a complex electrochemical reaction process. During charging, the external power supply controls the current and voltage through the Battery Management System (BMS) to ensure safe and efficient conversion of electrical energy into chemical energy. Lithium ions are extracted from the positive electrode under the action of the electric field, pass through the electrolyte and diaphragm, and finally embed in the negative electrode. During discharge, the process is reversed, with lithium ions escaping from the negative electrode and returning to the positive electrode, releasing the stored energy. During this process, the BMS is also responsible for monitoring battery status to prevent abnormal conditions such as overcharging, over-discharging and short-circuiting.

4. How can the safety performance of lithium batteries be ensured?

The safety performance of lithium batteries is the key to their widespread use. To ensure safety, lithium batteries are designed with several protective measures. Firstly, the positive and negative electrode materials are selected with good thermal stability and non-flammable electrolytes to reduce the risk of thermal runaway. Secondly, the diaphragm has excellent ion conductivity and mechanical strength, which effectively prevents internal short circuits. In addition, the battery case is made of strong materials that can withstand certain external impacts and crushes. Most importantly, the battery management system (BMS) can monitor the battery’s voltage, current, temperature and other parameters in real time, and take immediate action when an abnormality is detected, such as cutting power or starting the heat dissipation mechanism, ensuring that the battery operates under safe and efficient conditions.

In summary, the working principle and composition of lithium batteries is a complex and sophisticated system involving knowledge from many fields such as electrochemistry, materials science and electronics. Through continuous optimisation of materials, structures and management systems, the safety performance and service life of lithium batteries have been significantly improved, providing a solid energy guarantee for the technological progress of modern society.