Diffusion of Li-deficient phases in large LiFePO4 single crystals during chemical delithiation. Issue 23 (30th May 2018)

• Record Type: Journal Article
• Authors: Yamanaka, Toshiro; Abe, Takeshi; Nishio, Koji; Ogumi, Zempachi
• Is Part Of: Journal of materials chemistry. Volume 6:Issue 23(2018)
• Page Start: 11005
• Page End: 11011
• Publication Date: 2018-05-30
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c8ta02449a
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Unexpectedly fast diffusion of microphases with Li-vacancies through large LiFePO4 single crystals was detected by Raman spectroscopy. Abstract : Diffusivity of lithium (or Li vacancies) in active materials in a lithium ion battery is a key property to achieve high battery performance. Propagation of Li-deficient phases in large LiFePO4 single crystals along the (100), (010) and (001) planes (a, b and c planes, respectively) during chemical delithiation was studied by in situ Raman spectroscopy. Li was extracted from one of the b (a, c) planes, and Raman spectroscopy was simultaneously conducted on the other b (a, c) plane on the opposite side. Li-deficient phases were observed 10 minutes after delithiation was started. The results indicate that the diffusivity of Li along the b axis during migration of Li-deficient phases under this condition is in the order of 10 −5 cm 2 s −1, which are five to seven orders of magnitude higher than Li diffusivities previously reported. The density of Li-deficient phases on the b plane continued to increase even after delithiation had stopped. The diffusivities of Li along the a and c axes were also in the order of 10 −5 cm 2 s −1, but the diffusivity along the a axis was smaller than those along the b and c axes. The very fast diffusion is thought to be induced by a diffusion mechanism that is strongly coupled to the chemical potential of Li in Li x FePO4 depending on the concentration of Li( x ).