Lithium iron phosphate material has become a promising lithium ion battery cathode material because of its low cost, good environmental compatibility, high specific capacity and good stability. Since the lithium iron phosphate material has low conductivity, a certain amount of conductive agent needs to be added during the compounding, and the conductive agent has a large specific surface area and a large number of particles per unit mass, which is favorable for opening a chain conductive network in the electrode, thereby improving the conductivity of the electrode. It contributes to the capacity of lithium iron phosphate and reduces the internal polarization of the battery.
In conventional production, SP and KS-6 conductive additives are generally used to improve the conductivity of the pole piece and improve the flexibility of the pole piece. Carbon nanotubes (CNTs) have high conductivity and one-dimensional structure, and carbon nanotubes as conductive additives can significantly improve the conductivity of the positive electrode. Compared with granular conductive agents, fibrous conductive agents, such as gas-phase grown carbon fibers, carbon nanotubes, etc., have large aspect ratios, have large specific surface area and good electrical and thermal conductivity, and are favorable for forming conductive networks. And the conductivity is better. Experiments have shown that if a particulate conductive agent is added to the fibrous conductive agent, it can complement each other and take advantage of each material.
Thorat et al. used carbon fiber (CF) as a conductive additive, and the electrode consisted of 8% carbon fiber, 84% lithium iron phosphate and 8% polyvinylidene fluoride. The 2048 battery produced by the ** charge power was 3882 W/kg; The solid phase is mixed with carbon nanotubes, lithium iron phosphate powder and binder, and the obtained electrode has a discharge specific capacity of about 20 mAh/g at a discharge specific capacity of 0.1 C, and a discharge specific capacity of more than 146 mAh/g at a rate of 1.0 C. .
Deng Longzheng and Wu Feng from Beijing Institute of Technology proposed that the use of 1% CNT + 3% super P +1% KS-6 composite additive in the lithium iron phosphate battery cathode material can play a synergistic role in the composite additive and can effectively improve electricity. The overall performance of the core. The experimental data shows that the cell's capacity-to-capacity ratio reaches 146.32 mAh/g, which is higher than the cell's capacity-to-capacity ratio of 139.06 mAh/g with CNT + super P composite additive; the former has an internal resistance of 1.0 mΩ after the cell is divided. The latter is 3.25mΩ. In addition, the self-discharge of CNT + SP + KS-6 composite additive battery is small, the battery cycle performance is excellent, the battery has 2165 cycles, the capacity retention rate is 91.78%, and the battery cycle life is expected to reach 4000 or more (80% DOD). It can meet the needs of power batteries and energy storage batteries.
Comparison of cycle performance of lithium iron phosphate battery using composite conductive additive
(1C, 25 ° C)
Shoring tower is an effective supporting system. It is easy to assemble and dismantlement, and has excellent stability and bearing capacity. It has been widely used in the construction of industry & residential buildings, bridges, tunnels and dam project, etc.