Rational design of oxide/carbon composites to achieve superior rate-capability: Via enhanced lithium-ion transport across carbon to oxide

Jun Hui Jeong, Myeong Seong Kim, Yeon Jun Choi, Geon Woo Lee, Byung Hoon Park, Suk Woo Lee, Kwang Chul Roh, Kwang Bum Kim

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Coating oxides with conductive carbon is a widely used strategy to improve the rate capability of oxides by enhancing their electronic conductivity. However, there is a growing concern that a carbon layer may hinder lithium-ion transport to oxides, thus limiting the rate capability. Nonetheless, this issue has not yet been thoroughly investigated, and whether lithium-ion transport across a carbon layer does indeed limit the rate capability remains unclear. To single out the effect of lithium-ion transport across a carbon layer on the rate capability, we propose the rational design and synthesis of nano-perforated graphene (NPG)-wrapped oxide composites using commercial Li4Ti5O12 (LTO) and LiFePO4 (both with a particle diameter of ∼70 nm), wherein the NPG has nano-perforations on the basal plane of graphene. As the number of nano-perforations in the composites increases, the rate capability significantly increases. For example, NPG-wrapped LTO shows a specific capacity of 117.9 mA h g-1 at 100C and could be stably charged-discharged even at 300C. The excellent rate capability is mainly due to the enhancement of lithium-ion transport through the nano-perforations of NPG. Cyclic voltammetry and impedance analyses reveal that the improved rate capability of NPG-wrapped LTO is closely associated with an increase in the area of electrochemically active sites of LTO in the composite due to the enhanced lithium-ion transport through the nano-perforations of NPG, indicating that lithium-ion transport across a carbon layer could limit the rate capability of oxides coated with highly conductive carbon. These salient results will provide further impetus to the design and synthesis of novel high-rate carbon-coated oxides.

Original languageEnglish
Pages (from-to)6033-6044
Number of pages12
JournalJournal of Materials Chemistry A
Volume6
Issue number14
DOIs
Publication statusPublished - 2018 Apr 14

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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