Recycle Usage Of Recovering F-doped Lithium Iron Phosphate&Improvement Of Modified Al Foil On The Rate Performance Of The Cathode

The power batteries of lithium iron phosphate have been widely used in the field of electric vehicles.It is estimated that the many power batteries of lithium iron phosphate are on the point of attaining service life in the next several years.Therefore,it is important to study the recovering of lithium iron phosphate batteries.Among all power batteries of the lithium iron phosphate,the fluorine doped(F-doped)lithium iron phosphate occupies the major proportion.In addition,as one of the main parts of the lithium ions batteries,the performance of lithium ions batteries determines on the current collector of the Al foil.This dissertation main discuss the recycle usage of recovering F-doped lithium iron phosphate and the improvement of Al foil modified on the rate performance of layer lithium nickel cobalt manganese oxide(LNCM).Many advanced techniques,such as x-ray diffraction analysis,charge-discharged cycle,electrochemical impedance,cyclic voltammetry,scanning electron microscope,distribution of particle diameter,were employed to invertigate which is the key factor to determine the electrochemical performance of the samples.The main results are as follows:1 In the field of the recycle usage of recovering F-doped lithium iron phosphate:(1)the optimal sample of recovering F-doped lithium iron phosphate(OSRFLFP with the composition of LiFe(PO4)1.04F0.021)were prepared involving several steps as following:sintering,adding lithium salt,adding phosphate,adding carbon sources and sintering again.The experimental results show that the OSRFLFP prepared with sintering at 350℃ and added 5%glucose exhibits the 1st cycle capacity of 119.2 mAh·g-1 at the 2C rate,however,the F-doped lithium iron phosphate exhibits the 1st cycle capacity of 74.7 mAh.g-1.(2)The optimal sample of recovering F-doped lithium iron phosphate/graphene without sintering(OSRFLFP/G without sintering)with a olivine structure prepared by adding 6%graphene exhibits best electrochemical performance among all samples.While the discharged current is increasing from 0.2C rate to 100C one,its discharged voltage of the platform is decreased from 3.379 V to 3.359 V,the decreasing rate of the voltage is only 0.59%.It exhibits the capacity of 134.4 mAh·g-1(0.2C rate),123.0 mAh·g-1(2C rate),121.6 mAh·g-1(10C rate),121.3 mAh·g-1(50C rate),121.3 mAh·g-1(100C rate),respectively.Therefore,the graphene obviously improved the rate performance of recovering F-doped lithium iron phosphate.2 In the field of the improvement of the Al foil modified on the rate performance of the cathode of the layer lithium cobalt nickel manganese oxide(LiNi0.5Co0.2Mn0.3O2),three kinds of cathodes,prepared with an Al without pretreatment/LNCM,Al with pretreatment/LNCM and Al with pretreatment/graphene/LNCM,were prepared in advance.The charge-discharged performance of the as-prepared cathodes were investigated the performance at room temperature,55℃,-22℃,respectively.The experimental results show that the rate performance of the Al with pretreatment/graphene/LNCM is better than those of Al without pretreatment/LNCM and Al with pretreatment/LNCM.The Al with pretreatment/graphene/LNCM exhibits the capacity of 165.1 mAh·g-1(0.1C rate),162.7 mAh·g-1(1C rate),153.8 mAh·g-1(5C rate),152.3 mAh·g-1(10 C rate),respectively;Al with pretreatment/LNCM exhibit the capacity of 155.5 mAh·g-1(0.1C rate),150.4 mAh·g-1(1C rate),142.6 mAh·g-1(5C rate),137.1 mAh·g-1(10 C rate).The graphene and pretreatment obviously improved the rate performance of LNCM.The LNCM with the composition of LiNi0.5Co0.2Mn0.3O2 on the cathode of Al with pretreatment/graphene/LNCM exhibits the diffusion coefficients of lithium ions of 6.98 10-15cm2,s-1.