21700 battery.The main differences between nickel cadmium batteries and lithium batteries

　　The main differences between nickel cadmium batteries and lithium batteries

　　1. Different composition materials: Lithium batteries use carbon material (graphite) as the negative electrode and lithium containing compounds as the positive electrode; The positive electrode of a nickel cadmium battery is composed of active substances such as nickel oxide powder and graphite powder, while the negative electrode is composed of active substances such as cadmium oxide powder and iron oxide powder.

　　2. The working principle is different: Lithium batteries are more like a charge container and do not rely on electrochemical reactions during operation. When charging the battery, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move through the electrolyte to the negative electrode. As the negative electrode, carbon has a layered structure with many micropores, and the lithium ions that reach the negative electrode are embedded into the micropores of the carbon layer. The more lithium ions embedded, the higher the charging capacity. Similarly, when discharging the battery (i.e. the process we use the battery), the lithium ions embedded in the negative carbon layer are released and move back to the positive electrode. The more lithium ions are returned to the positive electrode, the higher the discharge capacity. The operation of nickel cadmium batteries requires electrochemical reactions. During charging, electrons travel along the wire to the cathode, and react with the water in the sodium hydroxide solution to form nickel hydroxide and hydroxide ions. Electrical energy is converted into chemical energy; During discharge, the hydroxide ions (OH -) in cadmium (Cd) and sodium hydroxide (NaOH) located at the negative electrode react to form cadmium hydroxide, which attaches to the anode and also releases electrons, converting chemical energy into electrical energy;

　　3. Different charging and discharging characteristics: Lithium batteries have strict control over the charging and discharging current, which cannot be too large, and the voltage gradually decreases and changes greatly during discharge. However, lithium batteries have higher charging efficiency and no memory effect; Nickel cadmium batteries can charge quickly with high current and provide high current to the load, and the voltage change during discharge is minimal. However, their charging efficiency is low and the memory effect is severe;

　　4. Single cell voltage is different: lithium batteries have a single cell voltage of 3.6V or 3.7V, while nickel cadmium batteries have a single cell voltage of 1.2V;

　　5. Durable characteristics differ: Lithium batteries are more delicate, and over discharging or overcharging can cause permanent damage. Therefore, protective circuit boards need to be installed, and maintenance needs to be carried out every six months; Nickel cadmium batteries can withstand overcharging or discharging, with simple and convenient operation. Long term storage will not cause performance degradation, and their original characteristics can be restored after being fully charged;

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