As an important part of the lithium ion battery, the conductive agent, although it occupies a small amount in the battery, it greatly affects the performance of the lithium ion battery, and has an effect on improving battery cycle performance, capacity development, rate performance, etc. Very important role.
Like lithium ion battery electrode materials, conductive agents are constantly evolving. From the earliest carbon black materials, it is characterized by point-like conductive agents, which can also be called zero-dimensional conductive agents, which mainly improve conductivity through point contact between particles; later, conductive carbon fibers and carbon nanotubes have been gradually developed. A type of conductive agent with a one-dimensional structure, due to its fibrous structure, increases the contact with the electrode material particles, greatly improves the conductivity of the electrode, and reduces the pole piece resistance.
Recently, the hot graphene material has gradually become a new type of conductive material for lithium-ion batteries. Because graphene has a two-dimensional sheet-like structure, it greatly increases the contact between electrode particles, improves conductivity, and reduces The amount of conductive agent is increased, and the energy density of the lithium ion battery is improved.
The role of lithium ion battery conductive agent:
The role of conductive agent:
The primary function of the conductive agent is to improve the electronic conductivity. In order to ensure that the electrode has good charge and discharge performance, a certain amount of conductive agent is usually added during the production of the pole piece to collect the micro current between the active material and between the active material and the current collector to reduce the contact of the electrode. Resistance accelerates the rate of movement of electrons. In addition, the conductive agent can also improve the workability of the pole piece and promote the infiltration of the electrode into the electrode. At the same time, it can effectively increase the migration rate of lithium ions in the electrode material and reduce the polarization, thereby improving the charge and discharge efficiency of the electrode and the lithium The service life of the battery.
Comparative analysis of conductive agent:
Conductive agents mainly include particulate conductive agents such as acetylene black, carbon black, etc., conductive graphite is mostly artificial graphite, fibrous conductive agents such as metal fibers, vapor-grown carbon fibers, carbon nanotubes, etc., as well as new types of graphene and its mixed conductivity The slurry is used as a conductive agent.
The influence of conductive agent content on electrical performance:
The role of the conductive agent in the electrode is to provide a channel for electrons to move. The appropriate content of the conductive agent can achieve higher discharge capacity and better cycle performance. If the content is too low, there will be fewer electronic conductive channels, which is not conducive to high current charging and discharging; The relative content of active materials is reduced, and the battery capacity is reduced.
The presence of conductive agents can affect the distribution of electrolyte in the battery system. Due to the space limitation of lithium-ion batteries, the amount of electrolyte injected is limited, generally in a poor state, and the electrolyte is used as the internal connection of the battery system. The distribution of extremely polar ions has a vital influence on the migration and diffusion of lithium ions in the liquid phase. When the content of conductive agent in one electrode is too high, the electrolyte is concentrated in this electrode and the lithium ion transmission process of the other electrode is slow, the polarization degree is high, and it is prone to failure after repeated cycles, thereby affecting the overall performance of the battery .
When the content of the conductive agent reaches a turning point, too much will only reduce the electrode density and decrease the capacity, while too little will result in a low utilization rate of the active material in the electrode and a decrease in the high-rate discharge performance.