Multiconstituent Synthesis of LiFePO₄/C Composites with Hierarchical Porosity as Cathode Materials for Lithium Ion Batteries

Abstract

Monolithic, three-dimensionally ordered macroporous and meso-/microporous (3DOM/m) LiFePO 4 /C composite cathodes for lithium ion batteries were synthesized by a multiconstituent, dual templating method. Precursors containing sources for lithium, iron, and phosphate, as well as a phenol-formaldehyde sol and a nonionic surfactant were infiltrated into a colloidal crystal template. Millimeter-sized monolithic composite pieces were obtained, in which LiFePO 4 was dispersed in a carbon phase around an interconnected network of ordered macropores. The composite walls themselves contained micropores or small mesopores. The carbon phase enhanced the electrical conductivity of the cathode and maintained LiFePO 4 as a highly dispersed phase during the synthesis and during electrochemical cycling. Monoliths containing 30 wt % C were electrochemically cycled in a 3-electrode cell with lithium foil as counter and reference electrodes. No additional binder or conductive agent was used. The capacity was as high as 150 mA h g À1 at a rate of C/5, 123 mA h g À1 at C, 78 mA h g À1 at 8C, and 64 mA h g À1 at 16C, showing no capacity fading over 100 cycles. In spite of the low electronic conductivity of bulk LiFePO 4 (10 À9 À10 À10 S cm À1 ), the monolithic LiFePO 4 /C composite was able to support current densities as high as 2720 mA g À1 .

Fabrication of Porous Carbon/TiO2 Composites through Polymerization-Induced Phase Separation and Use As an Anode for Na-Ion Batteries

“…40,41,42 As little as 3 % carbon has been reported, 43 but similarly composites with 50-50 metal oxide-carbon have exhibited good performance as 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 electrodes. 44,45 One challenge associated with design of electrode materials is that the performance is driven by a plethora of both physical and chemical variables.…”

Porous Electrode Materials for Lithium‐Ion Batteries – How to Prepare Them and What Makes Them Special

“…[ 182 ] Even though a phenolic resin is generally considered a hard carbon precursor, the graphitic domains in the composite were quite large ( ∼ 5 nm), and the sample was able to support current densities as high as 2720 mA g − 1 . The large graphitic domains were attributed to the presence of Fe 2 + in the precursor mixture, which can act as a catalyst for the formation of graphitic carbon.…”

Heterogeneous Nanostructured Electrode Materials for Lithium-Ion Batteries – Recent Trends and Developments

“…They have found that the discharge capacity is strongly affected by the amount of carbon residue and sintering temperature. After optimization, LiFePO 4 /C composites with 1.87 wt % of carbon exhibited a best electrochemical performance with capacities of 140 mAh/g at C/10 and 84 mAh/g at 5 C. Vu et al (2011) synthesized monolithic, three-dimensionally ordered macroporous and meso-/microporous (3DOM/m) LiFePO 4 /C composite cathodes by a multiconstituent, dual templating method. In this composite, LiFePO 4 is dispersed in a carbon phase around an interconnected network of ordered macropores.…”