Synthesis And Application Of Phosphate-based Cathode Materials With High Rate Cycling

Olivine-type phosphate-base cathodes with the advantages of excellent cyclability,outstanding thermal stability and costly ineffectiveness have been favored for lithium ion battery.Herein,olivine-type lithium iron phosphate(LiFePO4,LFP)with high rate cycability was synthesized and characterized.Additionally,Ni-rich cathode material(LiNi0.8Co0.1Mn0.1O2,LNCM)surface coated by olivine-type lithium manganese iron phosphate(LiFe0.2Mn0.8PO4,LFMP)with high electrochemically active,high voltage plateau and structural stability was systematically investigated,resulting into the improving of cycle performance and security for cathode material LiNi0.8Co0.1Mn0.1O2.A high-crystallized cathode material LiFePO4 was firstly fabricated by an arc-melting technique with high efficiency.The electrochemical measurements demonstrated that LiFeP04/C electrode delivered a high reversible capacity of 93 mAh g-1 at 20 C at room temperature after 300 cycles,which exhibited superior rate cycling performance.The pilot production of ultrafast fabrication of LiFePO4 sample with superior electrochemical performances were obtained,which can be further optimize to production of LiFePO4 in industrial scale with reduced energy consumption,and reduce the cost and increase the technical support.Secondly,an economical and scalable synthesis route of LiFePO4 precursors was prepared in pure water phase.After carbon coating,the LiFePO4/C nanoparticles exhibit a high discharge capacity of 107 mAh g-1 at 20 C.A high capacity retention with 90.7%could be obtianded after 500 cycles even at high current rate of 20 C with coulombic efficiency of 99.5%.This work suggested a simple,economic and environmentally benign method in preparation of LiFePO4/C cathode material for power batteries that would be feasible for industrial scale production.As demonstration in previous section,reduced nano-sized LiFeP04 precursor particles were fabricated.The nano-size LiFeP04/C particles were proved to have excellent high rate discharge capacity and long cycle life,and the cathode delivered high rate discharge capacity of 104 mAh g-1 at 30 C.Moreover,a capacity of 101.7 mAh g-1 with capacity retention of 97%remained after 850 cycles at 30 C.Lastly,the effects of surface coating by olivine-type LiFe0.2Mn0.8PO4 on the crystal structure,interfacial characteristics,electrochemical performance and thermal stability of Ni-rich cathode material LiNi0.8Co0.1Mn0.1O2 were investigated.It was confirmed that LiFe0.2Mn0.8PO4 homogeneously distributed on the surface of LiNi0.8Co0.1Mn0.1O2 cathode material.The electrochemical test shows capacity retention was 83.7%at 1 C after 100 cycles for the sample with 5%LiFe0.2Mn0.8PO4 coating,whereas that of the pristine sample was only 62%under the same conditions,respectively.The cycling performance of Ni-rich cathode material LiNi0.8Co0.1Mn0.1O2 was significantly improved by LiFe0.2Mn0.8PO4 surface coating.Moreover,the thermal stability of LiNi0.8Co0.1Mn0.1O2@LiFe0.2Mn0.8PO4 samples was enhanced with the exothermic peak shifts from 220.7? to 236.7? and 251.3?,which suggested that the thermal stability was effectively improved.Present study proposed an important technical scheme of surficial coating technology that might further expand the application field of the nickel-rich cathode materials.