Performance Of LiFePO₄-based Cells Using Three-dimensional Current Collector

Lithium iron phosphate battery has been considered as one of the most promisingcathode material for the application in the EVs and HEVs, featuring a high theoreticalcapacity, excellent cycling stability, low material cost, nontoxic and improved safety.However, two-dimensional structure of the electrode can not meet the demands forhigh loading of LiFePO4. Three-dimensional (3D) structure can provide more contactarea for electrochemical reactions which improve the charge-discharge performance.In this work, three-dimensional LiFePO4-based cell with Ni foam current collector wasprepared, and the electrochemical performance was also investigated.Different component proportions, mass loadings and thickness of LiFePO4cathodewere studied. Scanning Electron Microscope (SEM) was used to observe the electrodemorphology. The specific capacity and cyclic performance were studied by charge-discharge test, and Cyclic Voltammogram (CV) and Electrochemical ImpedanceSpectroscope (EIS) tests were used to discuss the electrochemical reactive process.The results show that the best component proportion is LiFePO4/C: AB: PVDF=80:10:10, and the thickness of the electrode is250μm with the mass loading under20mg. The specific capacities of LiFePO4-based cell at different rates are140mAh·g-1(1C),120mAh·g-1(3C),110mAh·g-1(5C) and90mAh·g-1(7C), respectively.The fault of the cell was induced by the lithium anode, and thus we prepared3Delectrodes for two materials, graphite and Li4Ti5O12, using Ni foam as the currentcollector. The results indicated that3D graphite electrode displayed the same rate andcyclic performance as the one using Al foil current collector, and the performace ofLiFePO4/graphite cell was not satisfied, with only a specific capacity of70mAh·g-1at0.2C. However, the3D Li4Ti5O12electrode displayed favourable rate performance.The LiFePO4/Li4Ti5O12cell displayed excellent rate performance and cyclicperformance. The specific capacity was70mAh·g-1at10C and there was no loss of thecapacity of the cell after300cycles at1C. The results indicated that the LiFePO4/Li4Ti5O12cell is a promising application in HEVs and EVs.