Degradation of lithium Iron phosphate-based cathode in lithium-ion batteries: a...

• Author(s): Plancha, Maria João ; Rangel, C. M. ; Rodrigues, B. ; Azevedo, F. ; Silva, A. A.
• Date: 2010
• Persistent ID: http://hdl.handle.net/10400.9/1133
• Origin: Repositório do LNEG
• Subject(s): Cathode degradation; Lithium-ion batteries; Lithium iron phosphate; Charge/discharge cycles
• Document Type: Conference Object
• Language: English

Description

Commercial Li-ion batteries were studied in view to investigate the degradation of the positive electrode in an end-of-life battery condition. Post-mortem analyses were performed by using SEM and DRX techniques; structural and morphological changes after prolonged cycling were evaluated comparatively to a fresh cathode sample. The cycling procedure based on a constant current (CC)/constant voltage (CV) charge and CC discharge was executed, being the condition of end-of-life battery achieved after submitting the Li-ion battery to nearly 2000 charge/discharge cycles. EDS analysis revealed zirconium element as the dopant of a LiFePO4-based cathode of the battery under study. According to X-ray diffraction results for the fresh (charged condition) cathode, the positive electrode includes in its constitution a mixture of crystalline compounds, LiFePO4 and FePO4. SEM images displayed and DRX patterns obtained for the cycled cathode showed modifications compared to the fresh cathode results, evidencing the degradation of the battery at the end-of-life: decrease in the density of microparticles associated to areas where the insertion/de-insertion occurs; decrease of the LiFePO4/FePO4 ratio; both results pointed out to the occurrence of battery loss capacity with the imposed charge/discharge cycles.