Comparative analysis of several conventional lithium battery conductive agent materials
With the increasing commercialization of lithium batteries, the charging and discharging process of lithium batteries on the surface of the positive electrode material is that when the battery is discharged, the lithium ions in the pores enter the positive electrode active material. If the current increases, The polarization increases and the discharge is difficult, so the conductivity between the electrons is poor. The conductivity of the province alone is far from enough for the active material. In order to ensure the electrode has a good charge and discharge performance, a certain amount is usually added during the production of the pole piece. The conductive agent between the active materials and the current collector play a role in collecting micro-current. Overview of Conductive Agents Mainly conventional conductive agents SUPER-P, KS-6, conductive graphite, carbon nanotubes, graphene, carbon fiber VGCF, etc., used as conductive agent materials for lithium-ion batteries. These conductive agents have their own advantages and disadvantages. Specifically: the application of conductive agent 01SP The current domestic lithium-ion battery conductive agent is still dominated by conventional conductive agent SP. Carbon black has better ionic and electronic conductivity. Because carbon black has a larger specific surface area, it is beneficial to the adsorption of electrolytes and improves ion conductivity. In addition, the primary carbon particles agglomerate to form a branched structure, which can form a chain conductive structure with the active material, which helps to improve the electronic conductivity of the material. 02 The graphite conductive agent is basically artificial graphite. Compared with the negative electrode material, the artificial graphite has a smaller particle size, which is beneficial to the compaction of the pole piece particles and improves the ion and electronic conductivity. The application ratio of 03CNT conductive agent in the field of high-end digital batteries is as high as over 50%, and the application ratio in the field of power batteries is relatively low. However, in recent years, as power batteries have gradually increased performance requirements such as energy density, rate performance, and cycle life, the proportion of CNT conductive agents in this field is gradually increasing. 04 Ketjen Black Ketjen Black only needs a very low amount of addition to achieve high conductivity, so Ketjen Black has always been the best in conductive carbon black, and has been a leader in the market for a long time. Compared with other conductive carbon blacks used in batteries, Ketjen Black has a unique branched morphology. The advantage of this form is that the conductor has many conductive contact points, and the branched chain forms more conductive paths, so very high conductivity can be achieved with a small amount of addition (other carbon blacks are mostly spherical or flakes, Therefore, a high amount of addition is required to achieve the required electrical properties). Ketjen Black is currently a relatively cutting-edge super conductive carbon black. At present, the top 10 lithium batteries are basically in use or testing. Among them, EC-300J is mainly used for nickel-metal hydride and nickel-cadmium batteries; ECP and ECP-600JD are mainly used for high-rate, large-capacity and current density lithium batteries, among which ECP-600JD is particularly prominent. The industry generally believes that its superior electrical conductivity, high purity and unique branched chain structure will emerge in the era when iron-lithium is used as a cathode material. Ketjen Black uses two products in batteries: CarbonECP and CarbonECP600JD, CP300JD. The content of the conductive agent a) The role of the conductive agent in the electrode is to provide a channel for electrons to move. A proper 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 large Current charging and discharging; too high will reduce the relative content of active materials and reduce battery capacity. b) The presence of conductive agent 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 the ionic body of the positive and negative electrodes 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 is high, and it is prone to failure after repeated cycles, thereby affecting the overall performance of the battery . C) 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. Analysis believes that both carbon nanotubes and graphene can be made into conductive pastes, and the price is much more expensive than ordinary carbon black SP. Carbon black is a very mature conductive agent, and the price is relatively stable. As the scale effect of CNT and graphene increases in the future, there is relatively large room for price drop, and the future application prospects are objective.