Preparation And Properties Of Porous Carbon Electrode Materials For Lithium Air Batteries With Pollen As Template

Lithium-air battery especially nonaqueous electrolyte lithium-air battery is becoming the focus due to its extremely high theoretical energy density that can be comparable to internal combustion engines and is one of the potential power supply technologies for large capacity pure electric vehicles in the future. However, due to the imperfections of the theoretical research and many constraints, the actual energy density of lithium air battery is much lower than that of theoretical energy density, the upgrade of actual performance was limited. Air electrode is one of the main factors that affect the charge and discharge performance of lithium-air battery and porous carbon material is the key to determine the performance of air electrode. Theoretically, the porous carbon material air electrode should satisfie that can provide enough pores and channels for the rapid diffusion of oxygen; Material itself has good electrical conductivity;Preferably with a high specific surface area to get more reactive sites for the electrochemical reaction; Fast ion conductivity; It is beneficial to obtain a higher specific energy with a larger proportion of large pore volume. Therefore, the aim of this paper is to build a porous carbon material with easy control of pore structure, large specific surface area and excellent electrochemical performance.In this paper, the pollen/polyaniline composites with spherical structure were synthesized by in situ polymerization under acidic conditions, The physical properties and electrical conductivity of the prepared composites were tested. The effect of ethanol content and synthesis temperature on the morphology and conductivity of the composites was studied; The composites were treated by the conventional atmosphere baking process,the physical and electrochemical properties of the porous carbon electrode materials were characterized, The effects of carbonization temperature on the surface morphology, specific surface area, pore structure and electrochemical properties of porous carbon materials were studied. The composite were processed by microwave sintering, the physical and electrochemical properties of the porous carbon electrode materials were characterized. The effects of heating rate on the surface morphology, surface area, pore structure and electrochemical properties of porous carbon materials were investigated. The results obtained are listed as fellows:(1) The synthesis temperature has obvious influence on the morphology and electrical conductivity of the composites, The higher the temperature, the more serious the reunion phenomenon. the resistivity of the composites synthesised under 5℃ is 429.77cm, and the resistivity of materials synthesised under 60℃ were too high to measure.The content of ethanol in the solvent has no obvious influence on the morphology of HF/PANI composites. Ethanol content from zero to 20wt%, the resistivity of the composites increased from 429.77 to 1719.08Ω·cm, and the electrical conductivity was significantly worse;(2) The electrode materials with spherical and micro porous structure were obtained at different temperatures; The specific surface area, average diameter and pore volume of material roasted at 950℃ were 876.912m2.g-1,1.113nm, and 0.488cm3.g-1. Electrochemical tests showed that the first discharge capacity of electrode materials calcined at 950℃ and 1200℃ were 5659.5mAh.g-1 and 3972.7mAh.g-1, respectively.(3) Microwave sintering has a densification effect on the morphology of materials, materials has a mesoporous structure and appear to be a certain degree of aggregation phenomenon. The average pore diameter of t electrode materials,which were sintered at a temperature rate of 10℃/min and 20℃/min were 3.527nm and 3.443nm, the specific surface area and pore volume were 8.960m2g-1 and 0.0158 cm3g-1,9.812m2g-1 and 0.0169cm3g-1. Electrochemical performance studies showed that the two have a comparable capacity and cycle performance, The initial discharge specific capacity of the electrode material sintered at a temperature rate of 10℃/min was 774.7mAh.g-1 at a current density of 50mA.g-1 and 900.8mAh.g-1 of material sintered at a temperature rate of 20℃/min, after the sixth cycle, the two simultaneous discharge termination.