The positive electrode is mainly responsible for providing the lithium ions and electrons required for discharge. It is usually made of lithium composite oxides (such as ternary materials, lithium iron phosphate). The choice of the material directly determines the energy density and voltage level of the battery. For example, the high energy density of ternary lithium batteries is attributed to the characteristics of the positive electrode material; while the high safety of lithium iron phosphate batteries is closely related to the stable structure of the positive electrode material.
The negative electrode is responsible for receiving and storing lithium ions. The mainstream negative electrode materials are mainly graphite, and some high-end batteries will incorporate silicon-based materials to increase capacity. During charging, lithium ions are released from the positive electrode, pass through the electrolyte and the separator, and are embedded into the pores of the negative electrode material; during discharge, these lithium ions are again released from the negative electrode, returning to the positive electrode and releasing electrons to form an electric current.
The electrolyte is responsible for allowing lithium ions to freely move between the positive and negative electrodes. It is typically divided into liquid electrolytes and solid electrolytes. Currently, liquid electrolytes are still the mainstream in batteries, consisting of lithium salts, organic solvents, and additives. The ionic conductivity and stability of the electrolyte directly affect the charging speed and cycle life of the battery - high-quality electrolytes enable the rapid transmission of lithium ions while avoiding adverse reactions with the positive and negative electrodes.
The separator is a porous membrane, typically made of polyethylene or polypropylene. It physically isolates the positive and negative electrodes, preventing direct contact between them and avoiding short circuits. At the same time, the porous structure of the separator allows lithium ions to pass through smoothly without affecting energy transmission. When the battery temperature is too high, some separators will shrink their pore diameters through the "thermal closed pore" property to prevent the movement of lithium ions, thereby preventing thermal runaway and adding "double insurance" for battery safety.
These four components are like a well-coordinated "team": the positive electrode provides energy, the negative electrode stores energy, the electrolyte transports energy, and the separator safeguards safety. It is their collaborative work that enables the battery to stably and continuously provide power for mobile phones, cars, energy storage devices, etc., becoming an indispensable energy core in modern life.
