Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity

Abstract

The specific capacity of commercially available cathode carbon-coated lithium iron phosphate is typically 120-160 mAh g À 1 , which is lower than the theoretical value 170 mAh g À 1 . Here we report that the carbon-coated lithium iron phosphate, surface-modified with 2 wt% of the electrochemically exfoliated graphene layers, is able to reach 208 mAh g À 1 in specific capacity. The excess capacity is attributed to the reversible reduction-oxidation reaction between the lithium ions of the electrolyte and the exfoliated graphene flakes, where the graphene flakes exhibit a capacity higher than 2,000 mAh g À 1 . The highly conductive graphene flakes wrapping around carbon-coated lithium iron phosphate also assist the electron migration during the charge/discharge processes, diminishing the irreversible capacity at the first cycle and leading to B100% coulombic efficiency without fading at various C-rates. Such a simple and scalable approach may also be applied to other cathode systems, boosting up the capacity for various Li batteries.

Towards High Capacity Li-ion Batteries Based on Silicon-Graphene Composite Anodes and Sub-micron V-doped LiFePO4 Cathodes

“…Furthermore, different types and grades of graphene are becoming increasingly available, at cost competitive prices. Modification of the LFP surface with graphene has been shown to deliver capacities of up to 208 mAh g −1 , an increase of approximately 18% compared with the theoretical maximum of unmodified LFP (170 mAh g −1 )25. This is said to occur via a reversible redox reaction between the Li ions of the electrolyte and the flake graphene coating.…”

The high electrochemical performance of Li 3 V 2 (PO 4 ) 3 supported by graphene and carbon-nanofibers for advanced Li-ion batteries

“…The discharge capacity of Na 3 V 2 (PO 4 ) 3 was 119.6 mAh g À1 , slightly larger than theoretical capacity (117.6 mAh g À1 ) [46]. In addition, the LiFePO 4 wrapped with the electrochemically exfoliated graphene delivered a capacity of 208 mAh g À1 m, which is beyond the theoretical capacity of 170 mAh g À1 [47]. This is mainly attributed to the reversible redox reaction between the lithium ions of the electrolyte and the exfoliated graphene sheets.…”

Enhanced Efficiency of Dye-Sensitized Solar Counter Electrodes Consisting of Two-Dimensional Nanostructural Molybdenum Disulfide Nanosheets Supported Pt Nanoparticles

“…Figure 2d shows the high-resolution S 2p spectra, the S 2− 2p 3/2 and S 2− 2p 1/2 peaks at 161. 9 Pt is predominantly present as metallic Pt along with surface oxides and hydroxide, as is normally observed in the case of Pt NPs [19]. Therefore, as above-mentioned, the oxidation groups on the crystal planes of the MoS 2 NSs probably act as nucleation sites to reduce the precursor Pt 4+ to Pt 2+ and Pt 0 in the mixture solution (H 2 PtCl 6 -EG-water) for the subsequent formation of PtNPs by EG reduction.…”

“…Recently, inspired by the discovery of graphene-which opened up the new research field of two-dimensional (2D) nanomaterials [8,9]-studies on 2D nanomaterials have attracted great attention. As a typical transition metal dichalcogenide, 2D layered nanostructural molybdenum disulfide (MoS 2 ) is similar to the graphene structure, and is composed of three stacked atomic layers (a Mo layer sandwiched between two S layers, S-Mo-S) [10].…”