Reducing Li-diffusion pathways via ``adherence'' of ultra-small nanocrystals of LiFePO4 on few-layer nanoporous holey-graphene sheets for achieving high rate capability

Dutta, Dipak and Santhosha, AL and Sood, AK and Bhattacharyya, Aninda J (2016) Reducing Li-diffusion pathways via ``adherence'' of ultra-small nanocrystals of LiFePO4 on few-layer nanoporous holey-graphene sheets for achieving high rate capability. In: RSC ADVANCES, 6 (92). pp. 89328-89337.

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Abstract

Olivine structured lithium iron phosphate, LiFePO4 (LFP), is a promising alternative cathode material due to its high theoretical capacity (170 mA h g(-1)), low cost and higher environmental compatibility. However, due to its poor electronic conductivity and Li+-ion diffusivity the electrochemical performance of LFP deteriorates with increasing charge/discharge rates. Networking of downsized LFP particles with an improperly chosen carbon conduit may not effectively reduce the Li+-ion diffusion pathways and improve electron transport. We demonstrate here a unique 3D configuration comprising ultra-small LFP particles (size: 5 +/- 2 nm) ``adhered'' to few-layer reduced holey-graphene oxide sheets (h-GO) that allows Li+-ions to traverse shorter non-tortuous pathways. The h-GO sheets, which are only <= 1% of the total weight of the LFP-carbon assembly, contain micro (approximate to 1.1-1.9 nm) to meso (approximate to 2.8-13.9 nm) scale sized chemically punctured holes and hence the probability of their blockage by the ultra-small LFP nanocrystals is negligible. On the other hand, a higher content of sp(2)-carbon in h-GO compared to graphene oxide (GO) simultaneously provides excellent electronic conductivity. The assembly of adhered monodispersed LFP nanocrystals on h-GO sheets displayed theoretical capacity (over nearly 1000 cycles) and extremely high rate performance at widely varying current densities (0.1-10C). Choice of hGO leads to an increase in the lithium diffusion, DLi+ in the LFP-h-GO by nearly two orders compared to the composite of LFP with non-porous graphene oxide (GO). The novel electrode architecture discussed here, which specifically exploits tweaking the charge transport pathways at small length scales (similar to nm), will also be highly applicable for electrodes of relevance to various battery chemistries and supercapacitors.

Item Type:	Journal Article
Publication:	RSC ADVANCES
Additional Information:	Copy right for this article belongs to the ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit Division of Physical & Mathematical Sciences > Physics
Date Deposited:	03 Dec 2016 09:57
Last Modified:	03 Dec 2016 09:57
URI:	http://eprints.iisc.ac.in/id/eprint/55381

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