The four Lithium battery components
▶ The cathode determines the capacity and voltage of the lithium ion battery
Lithium ion batteries generate electricity through the chemical reaction of lithium. This is why lithium is inserted into the battery and the lithium space is called "cathode". However, since lithium is unstable in elemental form, a combination of lithium and oxygen, lithium oxide is used for the cathode. The material that interferes with the electrode reaction of the actual battery like lithium oxide is called an "active material". In other words, in the cathode of a lithium ion battery, lithium oxide is used as the active material. If you look closely at the cathode, you will find a thin aluminum foil used to fix the frame of the cathode coating, using a compound composed of active materials, conductive additives and binders. The active material contains lithium ions, and conductive additives are added to increase the conductivity; the binder plays a role of adhesion, which helps the active material and the conductive additive to be well fixed on the aluminum substrate. The cathode plays an important role in determining the characteristics of the battery because the capacity and voltage of the battery are determined by the type of active material used for the cathode. The higher the lithium content, the greater the capacity; the greater the potential difference between the cathode and anode, the higher the voltage. The potential difference of the anode is very small, depending on their type, but for the cathode, the potential difference is usually relatively high. Therefore, the cathode plays an important role in determining the battery voltage.
▶ Anode sends electrons through wires
Like the cathode, the anode substrate is also coated with active material. The active material of the anode acts to cause current to flow through an external circuit, while allowing reversible absorption / emission of lithium ions released from the cathode. When the battery is charging, lithium ions are stored in the anode instead of the cathode. At this time, when the wire connects the cathode to the anode (discharged state), lithium ions naturally flow back to the cathode through the electrolyte, and electrons (e-) separated from the lithium ions generate electricity along the wire. For the use of anode graphite with a stable structure, and the anode substrate is coated with active material, conductive additives and binder. Due to the best quality of graphite, such as structural stability, low electrochemical reactivity, under the conditions of storing large amounts of lithium ions and price, the material is considered suitable for use in anodes.
▶ The electrolyte only allows ions to move
When explaining about the cathode and anode, it is mentioned that lithium ions pass through the electrolyte and electrons pass through the wire. This is the key to using electricity in batteries. If ions flow through the electrolyte, we not only cannot use electricity, but also endanger safety. The electrolyte is an important component. It is used as a medium capable of moving lithium ions only between the cathode and the anode. For the electrolyte, a material with high ion conductivity is mainly used, so that lithium ions easily move back and forth. The electrolyte consists of salts, solvents and additives. Dissolved salts are channels through which lithium ions move, solvents are organic liquids used to dissolve salts, and small amounts of additives are added for specific purposes. The electrolyte produced in this way only allows ions to move to the electrode and does not allow electrons to pass through. In addition, the moving speed of lithium ions depends on the electrolyte type. Therefore, only electrolytes that meet stringent conditions can be used.
▶ Protection plate, absolute barrier between cathode and anode
Although the cathode and anode determine the basic performance of the battery, the electrolyte and the protective plate determine the safety of the battery. The separator acts as a physical barrier to keep the cathode and anode separate. It prevents electrons from flowing directly, and only allows ions to pass through the internal micropores. Therefore, it must meet all physical and electrochemical conditions.