Lithium-ion Full Cell Manufacturing Process Training--Conductive agents Section
1.Introduction to conductive agents
1.1.The normal charging and discharging process of lithium battery is the process in which lithium ions and electrons participate in the reaction, which requires that the electrode of the lithium-ion battery must be a mixed conductor of ions and electrons, and the electrode reaction can only occur at the junction of electrolyte, conductive agent and active material. However, the conductivity of the positive and negative active materials of lithium-ion batteries is not satisfactory.
1.2.Cathode: mostly transition metal oxide or transition metal phosphate, which is a semiconductor or insulator with poor conductivity.
1.3.Anode: Graphite is the main material with good conductivity,but the graphite base surface is mainly conductive, and at the same time, the expansion and contraction of the graphite material during the charging and discharging process will lead to the deterioration of the contact between the particles, the increase of the gap, and the increase of battery polarization.
To sum up, both positive and negative electrodes need to be added and used with conductive agents
2.The role of conductive agents and the conductive mechanism
2.1.The role of conductive agents
2.1.1.Improve electrical conductivity, reduce polarization, improve the capacity of the material (increase the depth of reaction), and improve the discharge platform
2.1.2.Improvement of battery rate characteristics (charge + discharge)
2.1.3.Improves battery cycle life
2.1.4.Reduce the generation of lithium dendrites and improve the safety performance of batteries
2.1.5.Some conductive agents form a connection network inside the electrode to improve the adhesion of the electrode
2.1.6.Some conductive agents improve the rolling performance of the electrode and increase the compaction density
2.2.Conductive mechanism of conductive agents
2.2.1.Electronic conductivity: Construct short- and long-range conductive networks through self or physical connections to improve the physical polarization of the battery
2.2.2.Ionic conductivity: By absorbing and holding the electrolyte, it provides a reaction interface for the lithium ion charging and discharging process and reduces electrochemical polarization
3.Common types of conductive agents