Study On Processability Of Spherical Lithium Iron Phosphate Material

Spherical lithium iron phosphate materials?LiFePO₄?are secondary particles aggregated from primary nanoparticles prepared by spray drying method,which has the advantages of better fluidity and higher compaction density,but it cannot be directly applied in the industry.For this situation,effect of pulping technology,mixed materials and composite conductive materials on processability and electrochemical properties of LiFePO₄ was systematically studied in this paper,through evaluating slurry performance,electrodes,and battery performance including rate capacity,cycle stability and low temperature performance.Pulping technologies to evaluate processability of spherical material lithium iron phosphates were firstly compared in this study,including wet pulping technology and dry pulping technology.It is found from experiments that the pulping time of wet pulping technology and dry pulping technology were 8-12 h and 3-6 h,respectively.Dry pulping technology shortens pulping time and increases slurry solid content to 56%.It is suitable for rapidly detecting the slurry performance,electrode adhesion and other processability,although this method may have uneven dispersion of the binder,leading to a large internal resistance of electrodes and poor cycling performance of batteries.Secondly,processability and electrochemical properties of mixtures with two groups were explored.One is the mixed spherical LiFePO₄ with non-spherical LiFePO₄ in a different proportion,the other is mixed with different particle size spherical LiFePO₄.The results show that in mixtures of spherical LiFePO₄ with non-spherical LiFePO₄,mixture with a 7:3 mass ratio has the excellent comprehensive performance,which slurry shows a better stability,electrodes exhibit preferable cohesiveness and compaction density,smaller resistance,outstanding rate capacity and good cycle stability.For the mixtures with different particle sizes,the greater difference in the two particle sizes of the blended spherical cathodes exhibits an enhanced comprehensive performance when tested with14500 cylindrical batteries.This improvements include a higher compaction density,lower resistance,superior high-rate capacity,and an excellent cycle stability.It is an effectively way to improve the processability and electrochemical performance of spherical materials by compounding.Effect of composite conductive agents on the processability,rate capacity and cycle properties was studied.The result is found that it is a good way to improve the high rate discharge capacity,cycle performance and reduce the resistance of battery by using composite conductive additives contain carbon nanotube?CNT?or graphene?G?,respectively.The battery with composite conductive agent of CNT/Super-P/KS-15 has excellent electrochemical properties:The discharge capacity of this battery at 10C is equivalent to 92.2%of which at 1C,discharge capacity at 1C at-20°C is equivalent to64.6%of that at 25°C and the cycle capacity remain is 91.6%at 1C after 2000 cycles.