Lithium iron phosphate power cell is the most potential lithium-ion power battery for electric vehicles in the market, which has the advantages of good safety, long cycle life, and high energy density. However, lithium iron phosphate has poor electrical conductivity and conductive agent must be added to improve its conductivity. Most commonly used conductive agents are carbon black and graphite, which is cheap. However, in the process of multiple charging and discharging, the expansion and contraction of graphite materials reduces the contact between graphite particles, increases the gap, and even separates from the collector fluid and no longer participates in the electrode reaction. Therefore, the choice of conductive agent has an important role in improving battery performance.
At present, carbon nanotubes(CNTs) have gained wide attention in the application of conductive agents due to their excellent physical and chemical properties. The conductive mechanism of carbon nanotubes is that because they belong to one-dimensional nanomaterials, the length-diameter ratio is relatively large, which is good for the formation of conductive networks, and can improve the bonding between active materials and their collective flow, also it play the role as a physical adhesive. At the same time, it has excellent mechanical properties and chemical inertia, and it also has good thermal conductivity. It can improve the specific capacity and cycle life of the battery and improve the high temperature performance. It is an ideal new type of conductive material for lithium ion batteries.
In the experiment, multi-wall carbon nanotubes were applied to the positive and negative poles of lithium iron phosphate batteries respectively, and different tired batteries were prepared. The conventional performance and doubling rate were tested, and they were compared with the cores prepared by ordinary conductive carbon black. The test results show that, The electric core of high-conductive multi-wall carbon nanotubes added to the carburetor nanotubes has better conventional performance and double discharge performance than the conventional core, and the double discharge effect of both positive and negative poles is the best, followed by the addition of negative poles. The addition of MWCNTs to the negative electrode also shows the same situation. After the negative electrode capacity increases, it can embed more lithium ions when charging, which is conducive to the increase of discharge capacity, and because multi-walled carbon nanotubes have better electronic transport capabilities. In addition, more continuous conductive networks are formed in the click, which reduces the number of active substance particles encouraged. Also, the positive pole is added. The carbon nanotube, in high purity, is easy to disperse, has a low resistivity and can reach a resistivity of 650 μΩ. M, which is very suitable for battery use.
Multi-wall carbon nanotubes for lithium iron phosphate batteries
The addition of carbon nanotubes also has an important influence on the electrochemical performance of lead acid battery negative plates. After adding CNT, it can increase the amount of liquid absorption of the electrode, improve the transmission performance of the electrolyte in holes, and also improve the negative electrode conductivity, enhance the charging and discharging ability, improve the morphology and utilization rate of the active material, and slow down the salt of the negative electrode. In partial charge state, the rapid discharge cycle life of the plate can be extended. The negative electrode is added to the CNT battery prepared by 0.5 % CNT. When the SBAS0101 is rapidly charged and discharged under 50 % charge state, the battery discharge termination voltage is increased and the cycle life is extended.
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