Analysis of conductive agent on the properties of lithium iron phosphate battery charge and discharge

Source: 2020 - 04 - 14 after clicks: a conductive agent affect the performance of lithium iron phosphate lithium battery charge and discharge the battery paste preparation process, the addition of conductive agent is still necessary. Add conductive agent can make LiFePO formation of conductive network, collect micro electric current and reduce the contact resistance of electrode, speed up the electronic migration, thus improve the LiFePO charge and discharge performance. The commonly used conductive agent with carbon black, graphite, carbon fiber, metal fiber, etc. High structure carbon black particles small, mesh chain closely packed, specific surface area is big, is conducive to form in electrode conductive chain structure. Acetylene black ( AB) Is the best carbon black. Generally think of acetylene Hague degree is low, embedded in the lithium ion of gibbs free energy and release of lithium ion of gibbs free energy. Because the electrical conductivity of the acetylene black is big, small heat resistance, so it's influence on the battery safety degree is small. Graphite and carbon fiber has good electrical conductivity, density is small, the structure stability, chemical stability is good wait for a characteristic, is often used as lithium ion battery cathode material of conductive agent. As a kind of nano fiber materials, carbon nanotubes with high length to diameter ratio, large specific surface area and good conductive heat conduction performance. Ling-feng deng, compares the granular conductive carbon black and linear carbon nanofibers as conductive agent affect the performance of lithium-ion batteries. The content of conductive agent has obvious influence on charging and discharging performance of LiFePO4. If the conductive agent content is too low, it is difficult to form effective conductive network, also could not form enough electron conduction channel, is not conducive to large current charge and discharge. If the content is too high, can reduce the relative content of active material, reduce the specific capacity of the battery. The dispersion of conductive agent on the properties of ceramic materials has obvious influence. Dominko et al. Research has shown that add 2 wt % uniform dispersion of carbon black than add 10 wt % not uniform dispersion of carbon black with better electrochemical performance. Mr Kuroda and others also had similar junction. Chang-ling fan of LiFePO4 / C as the positive active material, with high electrical conductivity of polyaniline ( PAn) Instead of AB as a conductive agent for constant current charge and discharge test. Studies have shown that compared with AB, PAn as conductive agent the polarizability of LiFePO4 / C higher charge-discharge capacity under different current density increased. Zhang jie and studies the quantity and add koqin black rKB LiFePO4 positive paste in KB scattered on the influence of electrode coating adhesion and battery charging and discharging cycle performance comparison of the KB cell and AB LiFeP04 electrochemical performance of the battery. The results showed that the high-speed shear can effectively solve the lithium iron phosphate KB easy to reunite the problems in the process of preparation of electrode paste, improve battery paste dispersion, improve the adhesion strength of the anode coating; KB content too high or too low will affect the battery performance. When KB adding amount was 3%, 1 c discharge capacity under the multiplier of up to 141 mah/g. Charge and discharge of LiFePO4 mechanism in the process of charging and discharging of LiFePO4, P043 - in the crystal The existence of the limit of Li + mobile space, makes Li + stratification is only a two-dimensional movement process. Therefore, LiFePO4 conductivity and ionic diffusion rate is low, in large current charge and discharge capacity loss is bigger. People put forward different hypothesis to explain this phenomenon. Padhi et that unit interface product Li + transmission rate in LiFePO4 is fixed in the process of charging and discharging, interface from external to internal moving particles, shrinking. When the sum of all interface area is not enough to support the discharge current, discharge end. Of the discharge current, the greater the LiFePO4 particles can be embedded into the Li + concentration is smaller, the volume of LiFePO4 losses, the more serious.