Improved performance of LiFePO4 cathode for Li-ion batteries through percolation studies. (1st September 2017)

• Record Type: Journal Article
• Authors: Guzmán, G.; Vazquez-Arenas, J.; Ramos-Sánchez, G.; Bautista-Ramírez, M.; González, I.
• Is Part Of: Electrochimica acta. Volume 247(2017)
• Page Start: 451
• Page End: 459
• Publication Date: 2017-09-01
• Subjects: LiFePO4 -- Li-ion battery -- carbon Super P -- PVDF -- percolation threshold -- ionic transport; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2017.06.172
• Languages: English
• ISSNs: 0013-4686

Abstract

Graphical abstract: Abstract: This study evaluates the relationship established between active/inactive material of LiFePO4 (LFP) composites and the contributions arising from electronic conduction/Li + ionic transport during electrochemical performance of a Li-ion cell. A traditional electrode preparation technique is used to assembly four electrode compositions (LFP/C-SP: 94/06, 86/14, 80/20 and 74/26), selected around the percolation threshold, which are subsequently characterized using voltammetry, rate capabilities, electrochemical impedance spectroscopy and scanning electron microscopy. ∼7 wt% of carbon Super P (C-SP) is determined as the electric percolation threshold from the conductivity curves collected for binary components: LFP:C-SP and PVDF:C-SP. Cyclic voltammetry and rate capability plots reveal that electronic conduction (∼10 −2 S cm −1 ) of composites (80/20 and 74/26) above the percolation threshold do not present any impact in the rate capabilities of LFP cathode, whence this increase of C-SP only shrinks capacity, which is more emphasized at high C-rates. Thus, it is suggested that the excess of binder and conductive carbon beyond the percolation threshold generates the ion-blocking effect of PVDF, and ionic transport pathways are extended. A well interconnected network with an efficient amount of binder avoiding particle segregation and carbon disconnection is determined for the 86/14 ratio, likewise, obtaining better rate capabilities, electrode stability and properties during 50 cycles. This differs from the traditional composition used to assembly these composites (80/20).