As an important component of lithium-ion batteries, conductive agent plays a very important role in improving the cycle performance, capacity and rate performance of lithium-ion batteries, although it occupies a small proportion in batteries.
Like lithium-ion battery electrode materials, conductive agents are also evolving. From the earliest carbon black material, its characteristic is point conductive agent, also known as zero-dimensional conductive agent, mainly through point contact between particles to improve conductivity; later, gradually developed conductive carbon fibers and carbon nanotubes with one-dimensional structure of conductive agents, because of its fibrous structure, increased contact with electrode material particles, greatly improving the conductivity of the electrode. Recently, the hot graphene material has gradually become a new conductive material for lithium ion batteries. Because graphene has two-dimensional lamellar structure, it greatly increases the contact between electrode particles, improves the conductivity, reduces the amount of conductive agent, and improves the energy density of lithium ion batteries.
The role of conductive agents:
The primary function of conductive agent is to improve the electronic conductivity. In order to ensure that the electrodes have good charge-discharge performance, a certain amount of conductive agent is usually added to the fabrication of the electrodes to collect micro-currents between the active substances and between the active substances and the collector, so as to reduce the contact resistance of the electrodes and accelerate the movement rate of electrons. In addition, the conductive agent can also improve the processability of the electrode, promote the infiltration of electrolyte into the electrode, and also effectively improve the migration rate of lithium ion in the electrode material, reduce polarization, thereby improving the charging and discharging efficiency of the electrode and the service life of the lithium battery.
Classification of conductive agents:
The main conductive agents are granular conductive agents such as acetylene black, carbon black, etc. Conductive graphite is mostly artificial graphite. Fibrous conductive agents such as metal fibers, gas-phase growth of carbon fibers, carbon nanotubes, and new graphene and its mixed conductive slurry are used as conductive agents. These conductive agents have their own advantages and disadvantages. Today we will focus on VGCF. What is VGCF? Vapor-grown carbon fibers (VGCF) are simply conductive carbon fibers.
Conductive carbon fibers have a linear structure, which is easy to form a good conductive network in the electrodes and show good conductivity, thus reducing the polarization of the electrodes, reducing the internal resistance of the battery and improving the performance of the battery. Compared with the point-to-point contact between conductive carbon black and conductive graphite, the contact form between active material and conductive agent is point-to-line contact in the battery with carbon fiber as conductive agent, which not only improves the conductivity of the electrode, but also reduces the amount of conductive agent and increases the capacity of the battery.
VGCF has very few impurities and can be used safely in positive additives. If VGCF is added to the electrodes (positive and negative), VGCF has a large aspect ratio. Even after the expansion and contraction of positive and negative active materials, the gap between the particles of active materials can be bridged by VGCF, and the transmission of electrons and ions will not be interrupted, which can greatly improve the conductivity of the electrodes. Because the VGCF nanofibers are hollow, the positive and negative electrodes can absorb more electrolytes, so that lithium ions can be embedded smoothly and quickly, which is conducive to high rate charging and discharging. VGCF is a high strength fiber material with large aspect ratio, which can increase the windability of the electrode plate. The bonding strength between the particles of active material of positive and negative poles is stronger, and the powder will not crack because of winding, so the strength of the electrode can be improved.
Because of its high conductivity and thermal conductivity, the conductivity of positive and negative active materials is not good. Adding carbon nanofibers to improve the conductivity of positive and negative electrodes can also improve the thermal conductivity of positive and negative electrodes, which is conducive to heat dissipation. The above effects can greatly improve the characteristics of lithium ion batteries (cycle characteristics, output characteristics, etc.). VGCF is the most suitable additive material for lithium-ion batteries for automobiles with long life and high output.
VGCF is a superfine carbon fiber produced successfully in the first batch by Zhao Electric Engineering. It has high thermal conductivity, high electrical conductivity and high tensile strength and modulus. It is added to other material systems to change or enhance the physical properties of the material. At present, VGCF is mainly used as conductive agent of lithium electrical materials and additive of composite materials.
1. Cost surface
ShowaDenko Co. Ltd. produces high-quality VGCF in large quantities according to large-scale advanced equipment, and has a large demand.
The price can be reduced accordingly.
2. Accumulation of technical knowledge and knowledge
ShowaDenko has been developing VGCF series since 1982, and is a pioneer in this field.
Can be based on rich knowledge and insight to meet customer needs.
3. Stable supply
ShowaDenko has a high market share of VGCF-X with an annual output of 400 tons, VGCF with 100 tons and brand VGCF-H.
Carbon nanotubes with very high purity and crystallization.
It has high conductivity, heat conductivity and other properties, and is widely used in lithium batteries, resin composites, rubber composites, ceramics and other fields.