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Controllable synthesis of LiFePO4 in different polymorphs and study of reaction mechanism

Abstract

Lithium Iron Phosphate, a widely used cathode material in Lithium Ion Batteries (LIB), crystalizes typically in olivine-type phase, α-LiFePO4 (aLFP). However, the new phase β-LiFePO4 (bLFP) which can be transformed from aLFP under high temperature with high pressure, can be produced through simple liquid-phase reaction. The mechanism of controllable synthesis of the two polymorphs of lithium iron phosphate has not been studied thoroughly. In this paper, with thorough experiments, we demonstrate that controllable synthesis of LFP with different crystal polymorphs can be obtained by controlling certain conditions. Phosphate acid ratio in reactants and reaction time play key roles in the controllable syntheses. Higher phosphate acid ratio and shorter reaction time would result in more bLFP content, while less phosphate acid and longer reaction time would be beneficial to aLFP formation. To illustrate the mechanism for this phenomenon, detailed reaction process was researched via X-ray diffraction, from which a possible mechanism associated with evolution of crystal structures was demonstrated. Solvent content is also important for the process: some water content would lead to nanoplate-shaped aLFP particles appearing. Their influence on the reaction could be attributed to change of thermodynamics and kinetics, which leads to different crystal nucleation, growth and phase-change process.

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Publication details

The article was received on 18 Apr 2017, accepted on 08 Jun 2017 and first published on 08 Jun 2017


Article type: Paper
DOI: 10.1039/C7TA03369A
Citation: J. Mater. Chem. A, 2017, Accepted Manuscript
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    Controllable synthesis of LiFePO4 in different polymorphs and study of reaction mechanism

    H. Guo, H. Ping, J. Hu, X. Song, J. Zheng and F. Pan, J. Mater. Chem. A, 2017, Accepted Manuscript , DOI: 10.1039/C7TA03369A

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